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DEPARTMENT OF TRANSPORTATION Nassif Building, 400 Seventh Street, will stamp the date on the postcard and SW., Washington, DC, between 9 a.m. mail it to you. Federal Aviation Administration and 5 p.m., Monday through Friday, Availability of Rulemaking Documents except Federal holidays. 14 CFR Part 25 FOR FURTHER INFORMATION CONTACT: Don You can get an electronic copy using the Internet by: [Docket No. 2005–22840; Notice No. 05–10] Stimson, FAA, Airplane & Flight Crew Interface Branch, ANM–111, Transport (1) Searching the Department of RIN 2120–AI14 Airplane Directorate, Aircraft Transportation’s electronic Docket Certification Service, 1601 Lind Avenue Management System (DMS) Web page Airplane Performance and Handling (http://dms.dot.gov/search); Qualities in Icing Conditions SW., Renton, WA 98055–4056; telephone: (425) 227–1129; fax: (425) (2) Visiting the Office of Rulemaking’s Web page at http://www.faa.gov/avr/ AGENCY: Federal Aviation 227–1149, e-mail: [email protected]. Administration (FAA), DOT. arm/index.cfm; or SUPPLEMENTARY INFORMATION: (3) Accessing the Government ACTION: Notice of proposed rulemaking Comments Invited Printing Office’s Web page at http:// (NPRM). www.gpoaccess.gov/fr/index.html. The FAA invites interested persons to You can also get a copy by sending a SUMMARY: This action proposes to participate in this rulemaking by introduce new airworthiness standards request to the Federal Aviation submitting written comments, data, or Administration, Office of Rulemaking, to evaluate the performance and views. We also invite comments relating handling characteristics of transport ARM–1, 800 Independence Avenue to the economic, environmental, energy, SW., Washington, DC 20591, or by category airplanes in icing conditions. or federalism impacts that might result This proposed action would improve calling (202) 267–9680. Make sure to from adopting the proposals in this identify the docket number, notice the level of safety for new airplane document. The most helpful comments designs when operating in icing number, or amendment number of this reference a specific portion of the rulemaking. conditions, and would harmonize the proposal, explain the reason for any U.S. and European airworthiness recommended change, and include Authority for This Rulemaking standards for flight in icing conditions. supporting data. We ask that you send The FAA’s authority to issue rules DATES: Send your comments on or us two copies of written comments. regarding aviation safety is found in before February 2, 2006. We will file in the docket all Title 49 of the United States Code. ADDRESSES: You may send comments comments we receive, as well as a Subtitle I, section 106 describes the identified by Docket Number FAA– report summarizing each substantive authority of the FAA Administrator. 2005–22840 using any of the following public contact with FAA personnel Subtitle VII, Aviation Programs, methods: concerning this proposed rulemaking. describes in more detail the scope of the • DOT Docket Web site: Go to http:// The docket is available for public agency’s authority. dms.dot.gov and follow the instructions inspection before and after the comment This rulemaking is promulgated for sending your comments closing date. If you wish to review the under the authority described in subtitle electronically. docket in person, go to the address in VII, part A, subpart III, section 44701, • Government-wide Regulations and the ADDRESSES section of this preamble ‘‘General requirements.’’ Under that Policies Web site: Go to http:// between 9 a.m. and 5 p.m., Monday section, the FAA is charged with www.faa.gov/regulations_policies/ and through Friday, except Federal holidays. promoting safe flight of civil aircraft in follow the instructions for sending your You may also review the docket using air commerce by prescribing minimum comments electronically. the Internet at the Web address in the standards required in the interest of • Mail: Docket Management Facility; ADDRESSES section. safety for the design and performance of U.S. Department of Transportation, 400 Privacy Act: Using the search function aircraft. This regulation is within the Seventh Street, SW., Nassif Building, of our docket Web site, anyone can find scope of that authority because it Room PL–401, Washington, DC 20590– and read the comments received into prescribes new safety standards for the 001. any of our dockets, including the name design of transport category airplanes. • Fax: 1–202–493–2251. of the individual sending the comment • Hand Delivery: Room PL–401 on (or signing the comment of behalf of an Organization of This NPRM the plaza level of the Nassif Building, association, business, labor union, etc.). Discussion of this proposal is 400 Seventh Street, SW., Washington, You may review DOT’s complete organized under the headings listed DC, between 9 a.m. and 5 p.m., Monday Privacy Act statement in the Federal below. Whenever there is a reference to through Friday, except Federal holidays. Register published on April 11, 2000 a document being included in the For more information on the (65 FR 19477–78) or you may visit docket for this NPRM, the docket rulemaking process, see the http://dms.dot.gov. referred to is Docket Number FAA– SUPPLEMENTARY INFORMATION section of Before acting on this proposal, we 2005–22840. A list of acronyms used is this document. will consider all comments we receive included in an appendix located at the Privacy: We will post all comments on or before the closing date for end of the preamble material, between we receive, without change, to http:// comments. We will consider comments the regulatory evaluation and the text of dms.dot.gov, including any personal filed late if it is possible to do so the proposed amendments. Unless information you provide. For more without incurring expense or delay. We stated otherwise, rule sections information, see the Privacy Act may change this proposal in light of the referenced in this NPRM are part of discussion in the SUPPLEMENTARY comments we receive. Title 14, Code of Federal Regulations INFORMATION section of this document. If you want the FAA to acknowledge (14 CFR). Docket: To read background receipt of your comments on this documents or comments received, go to proposal, include with your comments I. Executive Summary http://dms.dot.gov at any time or to a pre-addressed, stamped postcard on If adopted, this rulemaking would Room PL–401 on the plaza level of the which the docket number appears. We revise certain sections of part 25 of Title

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14 Code of Federal Regulations (14 icing conditions and the operation of A. Past Regulatory Approach CFR). Part 25 contains the airworthiness the ice protection system. Currently, § 25.1419, ‘‘Ice protection,’’ standards for type certification of Service history shows that flight in requires transport category airplanes transport category airplanes, but it does icing conditions may be a safety risk for with approved ice protection features be not currently include specific transport category airplanes. There have capable of operating safely within the requirements for airplane performance been nine accidents since 1983 that may icing conditions identified in appendix or handling qualities for flight in icing have been prevented if this proposed C of part 25. This section also requires 1 conditions. Although part 25 requires rule had been in effect. The service flight testing and analyses to be airplanes with approved ice protection history that we examined includes performed to make this determination. features to be able to operate safely in airplanes certificated to part 25, to its Although an airplane’s performance icing conditions, there is no standard set predecessor, the Civil Air Regulations capability and handling qualities are of criteria defining what ‘‘to safely (CAR) 4b, or to part 25 icing standards important in determining whether an operate’’ in icing conditions means in when the airplane was certified under airplane can operate safely, part 25 does terms of airplane performance and part 23. In evaluating the potential for not have specific airplane performance handling qualities. Further, because the this rulemaking to avoid future or handling qualities requirements for existing icing regulations only address accidents, we only considered past flight in icing conditions, nor does the airplanes with ice protection provisions, accidents involving tailplane stall or FAA have a standard set of criteria it is unclear what requirements apply in potential airframe ice accretion effects defining what ‘‘to safely operate’’ in cases where the applicant is seeking to on drag or controllability. Accidents icing conditions means in terms of have an airplane without an ice related to ground deicing were not airplane performance and handling protection system certificated for flight considered. qualities. The proposed revisions to part in icing conditions. The NTSB has issued several safety 25 would provide a comprehensive set This notice proposes to amend part 25 recommendations related to airframe of harmonized requirements for airplane by adding a comprehensive set of icing, some of which are addressed, at performance and handling qualities to airworthiness requirements that must be least in part, by this notice. If adopted, address safe operation of transport met to receive certification approval for this rulemaking would require, during category airplanes in icing conditions. flight in icing conditions, including type certification, that manufacturers of Further, § 25.1419 requires an specific performance and handling transport category airplanes: applicant to demonstrate that the • qualities requirements, and the ice Investigate the susceptibility of airplane can operate safely in icing accretion (that is, the size, shape, their airplanes to ice-contaminated conditions only when the applicant is location, and texture of the ice) that tailplane stall (ICTS); • seeking to certificate ice protection must be considered for each phase of Provide for adequate warning on features. It fails to address certification flight. These proposed revisions would the flight deck of an impending stall in approval for flight in icing conditions ensure that minimum operating speeds icing conditions; • for airplanes without ice protection determined during the certification of Show that their airplanes meet the features. all future transport category airplanes same maneuvering capability and In contrast, the European would provide adequate maneuver handling characteristics requirements in airworthiness standards specifically capability in icing conditions for all icing conditions as in non-icing address certification for flight in icing phases of flight and all airplane conditions; and conditions, independent of whether the • configurations. Show that their airplanes have airplane includes ice protection This notice proposes to require the adequate performance capability in features. In addition, the European Joint same airplane handling characteristics icing conditions. Aviation Authorities (JAA) proposed that apply in non-icing conditions to As discussed in more detail later, the additional guidance material in the continue to apply in icing conditions. FAA has tentatively determined that early 1990s to provide criteria for Additionally, a specific evaluation for this rulemaking would have the determining whether an airplane’s susceptibility to tailplane stall in icing following costs and benefits over a 45- performance and handling qualities conditions would be added. This year analysis period. The cost of the would allow the airplane to operate proposal, if adopted, would harmonize proposed rule would be $22.0 million safely in icing conditions. The JAA’s the U.S. and European airworthiness (present value). The FAA assumes the guidance material was proposed in draft standards for flight in icing conditions. initial certification costs of $6.7 million Advisory Material—Joint (AMJ) It would benefit the public interest for four new airplane models are 25.1419.2 The JAA’s draft AMJ was while retaining or enhancing the current incurred in year one of a 45-year published on April 23, 1993, as a Notice level of safety for operation in icing analysis period. The future additional of Proposed Amendment (NPA) 25F– conditions. fuel burn expense is estimated to be 219, ‘‘Flight in Icing Conditions— If adopted, this rulemaking would $59.7 million and would be incurred Acceptable Handling Characteristics affect manufacturers, modifiers, and over the 45-year analysis period. The and Performance Effects.’’ operators of transport category airplanes benefits of this proposed rule consist of the value of lives saved due to avoiding B. Harmonization of U.S. and European (but only for new designs or significant Regulatory Standards changes to current designs that would accidents involving part 25 airplanes affect the safety of flight in icing operating in icing conditions. Over the 1. Federal Aviation Administration conditions). Manufacturers and 45-year period of analysis, the potential benefit of the proposed rule would be Title 14 CFR part 25 contains the U.S. modifiers may need to develop new airworthiness standards for type tests and analyses to determine ice $89.9 million ($23.7 million in present value at seven percent). certification of transport category accretions and to estimate performance airplanes. The part 25 standards apply effects for design and certification to 1 These accidents were selected from the National to airplanes manufactured within the address icing conditions. Operators may Transportation Safety Board’s (NTSB) accident need to develop new or revised database, and are discussed in Appendix 3 of this 2 A JAA AMJ is similar to an FAA advisory procedures regarding identification of premable. circular.

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U.S. and to airplanes manufactured in C. Proposal Development—Aviation performance standards already provide other countries and imported to the U.S. Rulemaking Advisory Committee some safety margin to offset the negative under a bilateral airworthiness The FAA, in cooperation with the effects of ice accretion. On the basis of agreement. JAA and representatives of the this service history, the FTHWG decided that the general approach to 2. Joint Aviation Authorities American and European aerospace industries, recognized that a common airplane performance in icing The JAR–25 contains the European set of standards would not only conditions used by the JAA in their airworthiness standards for type economically benefit the aviation draft AMJ 25.1419 was appropriate and certification of transport category industry, but also maintain a high level used this approach in its airplanes. Thirty-seven European of safety. In 1988, the FAA and the JAA recommendations to the FAA. This countries accept airplanes type began a process to harmonize their approach allows a limited reduction in certificated to the JAR–25 standards, respective airworthiness standards. To airplane performance capability due to including airplanes manufactured in the assist in the harmonization efforts, the ice before the effects of icing must be U.S. that are type certificated to JAR–25 FAA established the Aviation fully taken into account in the standards for export to Europe. Rulemaking Advisory Committee performance data provided in the 3 Airplane Flight Manual (AFM). Such an 3. European Aviation Safety Agency (ARAC) in 1991, to: approach minimizes the costs to (EASA) 1. Provide advice and recommendations concerning the full manufacturers and operators while The European Community established range of our safety-related rulemaking increasing the current level of safety for a new aviation regulatory body, EASA, activity; flight in icing conditions. to develop standards to ensure the 2. Develop better rules in less overall This proposed rulemaking is based on highest level of safety and time using fewer FAA resources than the FTHWG’s report, which ARAC environmental protection, oversee their are currently needed; and approved and forwarded to the FAA, uniform application across Europe, and 3. Obtain firsthand information and and refers to the ice accretions to be promote them internationally. The insight from interested parties regarding used in showing compliance. These ice EASA formally became operational for proposed new rules or revisions of accretions are defined in a new certification of aircraft, engines, parts, existing rules. subsection of appendix C to part 25.5 and appliances on September 28, 2003. There are 73 member organizations on The EASA will eventually absorb all of the committee, representing a wide D. Related Rulemaking Activity the functions and activities of the JAA, range of interests within the aviation 1. Amendment 25–108 including its efforts to harmonize the community. European airworthiness certification We tasked the ARAC Flight Test This Amendment, ‘‘1-g Stall Speed as regulations with those of the U.S. Harmonization Working Group the Basis for Compliance With Part 25 The JAR–25 standards have been (FTHWG) to recommend to the ARAC of the Federal Aviation Regulations’’ incorporated into the EASA’s new or revised requirements and (referred to as the 1-g stall rule) (67 FR ‘‘Certification Specifications for Large compliance methods related to airplane 708112, November 26, 2002) redefines Aeroplanes,’’ (CS)–25, in similar if not performance and handling qualities in the criteria for determining the stall identical language. The EASA’s CS–25 icing conditions.4 speed for transport category airplanes. became effective October 17, 2003. The FTHWG reviewed in-service The stall speed is important because it The proposals contained in this notice incidents and accidents involving is used as a reference speed for defining were developed in coordination with transport category airplanes. This minimum operating speeds that provide the JAA. However, since the JAA’s JAR– review revealed numerous incidents a safety margin above the speed at 25 and the EASA’s CS–25 are essentially resulting from the effects of ice on which the airplane will stall. The the same, all of the discussions of these airplane performance. The same review previous part 25 definition of stall speed proposals relative to JAR–25 also apply showed that the icing-related accidents defined it as the minimum speed to CS–25. resulted from a loss of control of the reached in a stalling maneuver. This The FAA’s rulemaking proposal, if airplane due to the effect of the ice on definition could result in a stall speed adopted, would parallel the JAA’s airplane handling qualities. Considering being defined that is too low to support rulemaking proposal, ‘‘Notice of this service history, the FTHWG the weight of the airplane in level flight. determined that airplanes should Proposed Amendment (NPA) 25B, E, F– The recently adopted 1-g stall rule generally meet the same handling 332,’’ published on June 1, 2002. defines the stall speed as the speed at qualities standards in icing conditions The EASA recently published for which the aerodynamic lift can support that they currently must meet for non- comment NPA 16/2004, ‘‘Draft Decision the weight of the airplane in 1-g flight. icing conditions. In certain areas, of the Executive Director of the Agency The 1-g stall rule also introduces a however, the FTHWG decided that the on Certification Conditions.’’ This NPA, requirement to demonstrate adequate current handling qualities standards published for comment in late 2004, is maneuver capability at the minimum were inappropriate for flight in icing based on the standards that the JAA operating speeds for airplane conditions. In these areas, the FTHWG were expected to adopt. configurations associated with low developed alternative criteria that Although the FAA, the JAA, and speed operations around airports. The would apply to icing conditions. EASA intend to harmonize the JAA adopted the same 1-g stall speed Since airplane performance standards for airplane performance and requirements in Change 15 to JAR–25. handling qualities for flight in icing degradation was not a causal factor in any of the icing-related accidents, the conditions, there are some differences 5 FTHWG concluded that the current The complete text of the FTHWG’s report is between this rulemaking proposal and available at http://www.faa.gov/avr/arm/arac/ the standards proposed by the JAA and aractasks/fr0404report.pdf. The FTHWG preferred 3 Published in the Federal Register (56 FR 2190), the term ‘‘ice accretion’’ rather than ‘‘ice shape’’ EASA. The differences are primarily on January 22, 1991. because it includes physical characteristics of the editorial and are not intended to result 4 Published in the Federal Register (56 FR 2190), ice build-up such as texture and surface roughness in significant regulatory differences. on June 10, 1994. in addition to its general size and shape.

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2. Ice Protection Harmonization II. Discussion of the Proposals handling qualities flight testing to be Working Group (IPHWG) conducted in natural icing conditions. A. Proof of Compliance (§ 25.21) Recommendations However, we expect that for most new We propose to add paragraph (g), to airplane designs, and for significant The FAA tasked the ARAC to specify the requirements that must be changes to existing designs, at least a consider whether airplane met in icing conditions if an applicant limited set of tests would be flown in manufacturers or operators should be seeks certification approval for flight in natural icing conditions. The purpose of required to install ice detectors or icing conditions. As discussed above, a these tests would be to confirm the provide some other acceptable way to review of icing-related incidents and airplane handling qualities and warn flightcrews of potentially unsafe accidents revealed loss of control to be performance results found through other ice accumulations. The ARAC assigned the greatest threat to safety of flight in means. The proposed advisory material this task to the IPHWG. The IPHWG icing conditions. Consequently, the will provide guidance on an acceptable recommended to the ARAC that the FTHWG identified the existing part 25 flight test program, including the FAA adopt an operating rule for certain requirements that could prevent loss of specific tests that should be conducted types of airplanes that would require a control if they were applied to icing in natural icing conditions. reliable method of informing pilots conditions. The FTHWG found, and we Historically, flight tests in measured when to activate the ice protection tentatively agree, that airplanes should natural icing conditions have also been system as well as a way of knowing continue to comply with most of conducted to verify analyses used to when ice is accumulating aft of areas subpart B of part 25 with ice on the generate ice accretions for compliance protected by the ice protection system. airplane to ensure safe flight in icing with § 25.1419(b), and to confirm the The IPHWG is also working on a conditions. The subpart B regulations general physical characteristics and recommendation for a type certification that would be excluded by paragraph location of ice accretions used to requirement that would identify (g)(1) were determined to be beyond evaluate airplane performance and acceptable ways to inform the flightcrew what was necessary to determine an handling qualities. This proposed rule is when to activate the ice protection airplane’s ability to operate safely in not intended to alter this practice or system. icing conditions. interpretation of § 25.1419(b). Existing We also tasked the ARAC to: Because the airplane performance and AC 25.1419–1, ‘‘Certification of • Define an icing environment that handling qualities requirements are Transport Category Airplanes for Flight includes supercooled large drop (SLD) flight-related requirements, it is in Icing Conditions,’’ provides guidance icing conditions; appropriate to place the proposed on comparing the ice accretions used to requirements for flight in icing • Recommend requirements to assess evaluate airplane performance and conditions in part 25, subpart B (Flight) the ability of aircraft to safely operate in handling qualities with those obtained rather than in the current ice protection SLD icing conditions, either for the in natural icing conditions. rule in § 25.1419. Section 25.1419 is in period of time necessary to exit or to Proposed paragraph (g)(1) would subpart F (Equipment), and, though it is operate without restriction; and apply the same airplane handling • closely linked with the subpart B qualities requirements to flight in icing Consider mixed phase conditions (a requirements proposed in this notice, it conditions as are currently required for mixture of supercooled water droplets primarily applies to the ice protection non-icing conditions. Paragraph (g)(1) and ice crystals) if such conditions are equipment on the airplane. would also apply most of the airplane more hazardous than the liquid phase The proposed subpart B requirements performance requirements currently icing environment containing would provide the minimum required for non-icing conditions to supercooled water droplets. performance and handling qualities flight in icing conditions. The icing When ARAC finishes its tasks, we requirements corresponding to the conditions for showing compliance expect it to forward to us a report § 25.1419 requirement that the airplane would be defined in appendix C to part containing their recommendations. ‘‘be able to safely operate in the 25. These requirements would apply to These recommendations may lead to continuous maximum and intermittent normal operations of the airplane and future rulemaking to address SLD icing maximum icing conditions of appendix its ice protection system as specified in conditions, but would not directly C.’’ Additionally, the proposed the AFM. By referencing the AFM, this impact this rulemaking. requirements would supply the means paragraph would require that this E. Advisory Material for determining, from a performance manual include the limitations and and handling qualities standpoint, operating procedures that are specific to In addition to being tasked to whether the ice protection system and operating in icing conditions. recommend new or revised its components are effective, as required As noted in the introductory requirements related to airplane by § 25.1419(b). discussion, some degradation in performance and handling qualities in Compliance with the proposed airplane performance capability would icing conditions, the ARAC FTHWG performance and handling qualities be permitted when showing compliance was tasked to recommend advisory requirements may be shown by a variety with the requirements for non-icing material identifying acceptable ways to of means that would be evaluated conditions. The amount of performance comply with the proposed new or during the particular airplane type degradation permitted in each case is revised requirements. The FTHWG certification program. These means may identified in the discussion of the developed a proposed Advisory include flight testing in natural icing individual performance regulations. Circular, (AC) 25.21–1X, ‘‘Performance conditions or in non-icing conditions Proposed paragraph (g)(2) would and Handling Characteristics in the using artificial ice shapes, wind tunnel prevent the use of different load, weight, Icing Conditions Specified in Part 25, testing and analysis, engineering and center-of-gravity limits for flight in Appendix C.’’ We are requesting public simulator testing and analysis, icing, except where compliance with the comments on this proposed advisory engineering analysis, and comparison to applicable performance requirements circular through a separate notice of previous similar airplanes. impose more restrictive weight limits. availability in this edition of the Federal The proposed requirements would not The reason for these proposed Register. specifically require performance and requirements is that operation in icing

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conditions should be essentially • The use of anti-icing fluids that precipitation on the ground. At earlier transparent to the flightcrew. There provide some protection from icing points in the takeoff path, while the should not be any special procedures or during the takeoff; airplane is closer to the ground, the methods used for operating in icing • Increasing use of ice detectors and proposed takeoff icing conditions would conditions other than activating ice deicing/anti-icing systems on airplanes be conservative, that is, they would protection systems. This philosophy that can be operated while the airplane predict larger ice accretions than would comes from applying human factors is still on the ground; and be likely to occur. If these conditions principles to reduce operational • The icing conditions that we were to actually occur at ground level, complexity and flightcrew workload. propose to use for the takeoff flight they would form a freezing fog phase. condition that would probably reduce B. Stall Speed (§ 25.103) Existing operating rules, §§ 91.527(a), visibility to the point that takeoffs could 121.629(b), and 135.227(a), prohibit We propose to revise § 25.103 to not be made. pilots from taking off with snow or ice require applicants to determine stall An important part of determining the adhering to the wings or other critical speeds with ice on the airplane. The effects of ice accretion on takeoff airplane surfaces. Additionally, proposed § 25.103(b)(3) adds ice performance is to decide at what point §§ 121.629(c) and 135.227(b) require accretion as a variable that must be in the takeoff ice accretion is considered airplane operators to have either an considered when determining stall to begin. For the purposes of this approved ground deicing/anti-icing speeds to use for the different part 25 rulemaking, we consider ice accretion to program or conduct a pre-takeoff airplane performance standards. begin when the airplane lifts off the contamination check within five runway surface during takeoff. Determining stall speeds with ice minutes before beginning a takeoff to Proposed § 25.105(a) would require accretions is necessary to identify any ensure that the wings, control surfaces, applicants to determine airplane takeoff increase in stall speeds from those and other critical surfaces are free of performance for icing conditions if the determined for non-icing conditions. frost, ice, or snow. Operators must train ice that can accrete during takeoff The applicant would then compare any the pilots on the effects of these results in increasing the reference stall change in stall speed due to ice contaminants on airplane performance speed (VSR) or degrading climb accretion with the allowable stall and and controllability, on how to recognize performance beyond specified limits. operating speed effects contained in the airplane contamination, and on Section 25.105(a) references all proposed airplane performance procedures intended to ensure that regulations related to the takeoff path. standards to determine whether or not contamination is removed before As a result, the performance for the airplane performance data must be takeoff. entire takeoff path, including takeoff determined specifically for icing Ground deicing/anti-icing programs speeds and distances, must be conditions. include the use of deicing/anti-icing determined for icing conditions if the fluids to remove ice and snow and C. Takeoff (§ 25.105) stall speed or climb performance prevent them from reappearing on degradation limits are exceeded. We propose to revise § 25.105(a) to airplane surfaces during freezing Section 25.105(a)(2)(i) of the proposal add the net takeoff flight path described precipitation conditions. Although these would require applicants to determine in § 25.115 to the list of airplane takeoff fluids are designed to flow off the takeoff path performance for icing performance parameters that must be airplane during the takeoff roll, we conditions if the stall speed increases by determined under the conditions expect the fluids to continue to provide more than 3 knots in calibrated airspeed specified in this paragraph. some protection throughout the takeoff or 3 percent due to ice accretions. This Additionally, § 25.105(a) would specify ground run. proposed requirement would be more when compliance must be shown On some older airplane models, the stringent than the guidance used by the specifically for icing conditions. wing ice protection system was JAA in their draft AMJ 25.1419. The designed for use in flight and cannot be We consider the proposed changes draft AMJ allowed up to a 5 knot or 5 operated while the airplane is on the necessary to ensure the safety of takeoff percent increase in stall speed before ground. Yet many of the current operations in icing conditions. Ice on the takeoff performance would need to generation of airplanes have ice the wings and control surfaces can be recomputed for icing conditions. protection systems that can be operated Several commenters on the AMJ, reduce the safety margins that currently while the airplane is on the ground. including us, expressed concern over are provided to prevent stalling the Some of these systems are also coupled allowing such a large increase in stall airplane. It can also degrade airplane with ice detector systems that will speed believing it would result in a climb performance, and cause automatically activate the ice protection significant reduction in safety margin controllability problems. We system in icing conditions. These between the minimum operating speeds acknowledge that many transport features tend to reduce the chances that and the stall speed. We agree with the category airplanes have safely operated ice will adhere to critical airfoil surfaces FTHWG recommendation that a 3 knot in icing conditions using takeoff speeds during airplane ground operations in or 3 percent increase in stall speeds is determined for non-icing conditions. atmospheric icing conditions. the maximum that should be permitted We agree with the FTHWG, however, As discussed later, we propose to before the takeoff performance data that it is in the interest of safety to revise appendix C of part 25 to define should be recalculated to consider the consider the effects of ice accretions on atmospheric icing conditions effects of icing. airplane takeoff performance. specifically for the takeoff phase of Also, the JAA’s draft AMJ 25.1419 In developing this proposal, the flight. These proposed atmospheric used the effect of ice accretions on FTHWG and the FAA considered four icing conditions would apply airplane drag rather than on climb factors: throughout the takeoff path, but are performance to determine when the • Operating rules and practices based on the more critical conditions takeoff performance data must be intended to ensure that critical surfaces that would be expected to occur at the provided for icing conditions. However, of the airplane are free of snow or ice end of the takeoff path. These we agree with the FTHWG before beginning a takeoff; conditions do not include freezing recommendation to consider the effect

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of ice accretions in terms of climb takeoff. Takeoff speeds must be E. Takeoff Path (§ 25.111) performance in § 25.105(a)(2)(ii) because established sufficiently above this speed it would cover more operating variables to assure the airplane can safely take off Currently, § 25.111 defines the takeoff than just the effect of ice on airplane considering the variations in procedures path, describes the airplane drag. and conditions that can reasonably be configuration that applies to each The part 25 takeoff climb expected in day-to-day operations. portion of the takeoff path, and provides requirements include a safety margin by Because these proposals assume that ice airplane performance requirements that requiring applicants to determine a net accretion does not begin until liftoff, must be met. We propose to revise § 25.111 by adding a new paragraph flight path based on the airplane’s actual this proposal would allow the VMU climb performance capability reduced speeds for non-icing conditions to be (c)(5) stating that the airplane’s drag by a set value that depends on the used for determining takeoff speeds in used to determine the takeoff path after number of engines on the airplane. icing conditions. liftoff would be based on the ice Proposed § 25.105(a)(2)(ii) would The ground minimum control speed accretions defined in the proposed require applicants to determine takeoff (VMCG) is used in determining the revision to appendix C. To path performance specifically for icing takeoff V1 speed. The takeoff V1 speed accommodate the addition of the new conditions if more than half of this is the highest speed at which the pilot paragraph, the ‘‘and’’ at the end of safety margin would be lost due to the must take the first action to be able to § 25.111(c)(3) would be moved to the effects of ice accretion. safely stop the airplane during a rejected end of § 25.111(c)(4). Part 25 divides the takeoff climb takeoff and the lowest speed at which The takeoff path begins at the start of performance requirements into several the takeoff can be safely continued after the takeoff roll and ends when the segments. To establish the allowable an engine failure. Since VMCG, like VMU, airplane is either 1,500 feet above the limit for takeoff climb performance occurs before the airplane lifts off the takeoff surface, or at the altitude at degradation in icing conditions, runway, the assumption is that ice has which the transition from the takeoff to § 25.105(a)(2)(ii) would consider the not yet begun accreting on the airplane. the en route configuration is completed effect of ice accretions on just the Therefore, this proposal would allow and the final takeoff speed attained, takeoff climb segment defined by the VMCG speeds determined for non- whichever is higher. The takeoff path § 25.121(b). For most transport category icing conditions to be used for typically has two distinct climb airplanes, this segment most often limits determining V1 for icing conditions. segments: One from the point at which the allowable takeoff weight, and The air minimum control speed, VMC the airplane is 35 feet above the runway therefore is the most critical to safety. If (commonly referred to as VMCA), is up to 400 feet, and the other from a the effects of ice accretions during the defined in § 25.149(b) as the airspeed at height of 400 feet to the end of the takeoff climb segment defined in which it is possible to maintain control takeoff path. The proposed changes to § 25.121(b) are beyond specified limits, of the airplane, with no more than 5 § 25.111 would identify when the the airplane performance for the entire degrees of bank, when the critical takeoff path must be determined for takeoff path must be determined with engine is suddenly made inoperative. flight in icing conditions and specify the ice accretions on the airplane. This Section 25.107 requires the rotation ice accretion that must be used for these would include from the beginning of the speed (VR) and the takeoff safety speed two climb segments. takeoff roll until the airplane is at least (V2) to be sufficiently higher than VMCA New paragraph (c)(5) would refer back 1,500 feet above the takeoff surface. to assure that the airplane will be safely to the proposed § 25.105(a)(2) to identify Thus, for airplanes that would be most controllable if the critical engine fails when the takeoff path must be affected by ice accretions during the during the takeoff. Since VR occurs determined for flight in icing takeoff climb, additional safety margins before liftoff, like VMU and VMCG, this conditions. The ice accretions would also be provided for the takeoff proposal would allow the VMCA speeds referenced in new paragraph (c)(5) ground run even though ice accretion is determined for non-icing conditions to would apply to the airborne portions of assumed not to begin until liftoff. be used for determining VR for icing conditions. the takeoff path, since we are assuming D. Takeoff Speeds (§ 25.107) Several concerns must be addressed if that ice accretion does not begin until We propose to revise § 25.107(c)(3) we are to allow VMCA speeds liftoff. If takeoff path performance must and (g) to change the reference for determined in non-icing conditions to be determined for icing conditions, then maneuver capability considerations be used to determine V2 in icing the takeoff path must use the takeoff from § 25.143(g) to § 25.143(h). This is conditions. Unlike VR, V2 occurs after speeds of the proposed § 25.107 for an editorial change due to the liftoff and ice could have begun icing conditions, using the ice redesignation of § 25.143(g) to accreting on the airplane. Ice may accretions specified in paragraph (c)(5). § 25.143(h) proposed below. accrete at V2 because ice protection F. Landing Climb: All-Engines- We also propose to revise § 25.107 by systems are typically not turned on until Operating (§ 25.119) adding a new paragraph (h). This new the airplane climbs more than 400 feet paragraph would state that the after takeoff. Also, many airplanes do We propose to revise § 25.119 by minimum control speeds (VMCG and not have any ice protection on the requiring the airplane landing climb VMC) and minimum unstick speeds vertical stabilizer. These concerns could performance to be determined for both (VMU) determined for the airplane in lead to a reduction in the airplane’s non-icing and icing conditions; adding non-icing conditions may also be used directional control capability if ice references to the appropriate paragraphs for the airplane in icing conditions. The accretion occurs. To alleviate these of the proposed § 25.125 revision for the VMU, VMCG, and VMC speeds are used to concerns, the proposed § 25.143(c) landing climb speed to use for non-icing determine the takeoff speeds V1, VR, and would require applicants to show that and icing conditions; referring to the V2. airplanes are safely controllable and proposed appendix C revision to The minimum unstick speed (VMU) is maneuverable at the minimum V2 speed identify the ice accretion that would be defined in § 25.107(d) as the airspeed at with the critical engine inoperative and used in determining landing climb and above which the airplane can safely with the ice accretion applicable to the performance in icing conditions; and lift off the ground and continue the takeoff flight phase. changing the speed used to show

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compliance with § 25.119 from a speed could be accreted during this climb for determining en route flight paths, less than or equal to VREF to VREF. segment. Therefore, the proposal for which would apply to both icing and We consider the approach and § 25.21(g)(1) excludes compliance with non-icing conditions. The proposed landing phases of flight to be the flight § 25.121(a) with ice accretions on the speed, VFTO, is currently used as the phases most affected by icing conditions airplane. minimum allowable speed for the final because of the potential for descending We propose revising § 25.121(d) to takeoff. into and holding in icing conditions state when the approach climb speed Additionally, the proposed revision to prior to landing. In addition, service must be adjusted for use in icing § 25.123(b) would state when an history has shown that the majority of conditions. Unlike the speeds used in applicant must determine the en route icing accidents and incidents occur in the takeoff path, the need to adjust the flight paths specifically for icing the holding, approach, and landing approach climb speed would not be conditions. Similar to the takeoff path flight phases. For these reasons, our based on the effect of ice accretions on requirements of the proposed revision to policy for the last 40 years has been for the airplane’s stall speed. Instead, the § 25.111, en route flight path applicants to account for the effects of measure for determining whether the performance needs to be specifically airframe ice accretion in their airplane’s approach climb speed needs to be determined for icing conditions if the approach and landing climb adjusted for icing conditions is based on effect of ice: (1) Increases the en route performance data provided in the the effect of ice accretions on the speed by more than 3 knots or 3 percent, Airplane Flight Manual. (Approach and approach climb speed. If the approach or (2) reduces climb performance by landing climb performance refer to the climb speed for icing conditions does more than half the safety margin airplane’s climb capability in the not exceed the climb speed for non- provided by the net gradient adjustment approach and landing configurations icing conditions by more than the required by § 25.123(b). The ice during the approach and landing flight greater of 3 knots calibrated airspeed accretion to be used would be specified phases. Sections 25.121(d) and 25.119 (CAS) or 3 percent VSR, then non-icing in the proposed revision to appendix C. require minimum level of approach and speeds may be used for calculating The reason for proposing to limit the landing climb performance to ensure approach climb performance for icing minimum allowable en route climb that airplanes can abort an approach or conditions. speed to VFTO to is to prevent applicants landing attempt and safely climb away.) The existing requirement for from showing compliance with § 25.123 The proposed changes to §§ 25.119 and determining the approach climb speed by trading altitude for airspeed when 25.121(d) (see below) serve to codify in non-icing conditions provides transitioning from the final takeoff to this policy. applicants some flexibility by only the en route climb segment. This specifying the maximum allowable clarifying change is consistent with our G. Climb: One-Engine-Inoperative approach climb speed. No lower limit is original intent for § 25.123(a). (§ 25.121) specified and we have accepted Another reason for not allowing an en We propose to revise § 25.121 by approach climb speeds as low as 1.13 route climb speed less than VFTO is that rearranging paragraphs (b), (c), and (d) VSR (that is, 13 percent above the VFTO is the speed at which the to specify when the required climb reference stall speeds). We would accept maneuver capability requirements performance must be determined for this same level of flexibility for contained in the existing § 25.143(g) icing conditions; refer to the proposed establishing the approach climb speeds must be met in the en route appendix C revision to identify the ice in icing conditions. The approach climb configuration. Allowing an en route accretion that would be used in speeds for icing conditions should also climb speed lower than VFTO would not calculating approach climb performance be evaluated to ensure that they provide ensure that the airplane has adequate in icing conditions; and provide the adequate maneuver capability. maneuvering capability during the en conditions under which the approach This proposal for the approach climb route climb phase of flight. climb speed must be increased to segment is less stringent than the 3 We are not proposing any changes to account for the effect of ice accretion. knots or 3 percent VSR standard used for the two-engine-inoperative en route Sections 25.121(b) and (c) provide the takeoff path speeds. For example, if the flight path requirements contained in climb performance requirements for the approach climb speed is 1.25 VSR and § 25.123(c) for flight in icing conditions. takeoff path segments beginning at the VSR is 100 knots, 3 percent of the We do not expect the pilot to stay in point the landing gear is fully retracted approach climb speed is 3.75 knots, icing conditions with one engine and ending at the end of the takeoff while 3 percent of VSR would be only inoperative for a long enough duration path. As in the proposed revision to 3 knots. The approach climb speed for the failure of a second engine in § 25.105, we propose to revise could increase by 3.75 knots without icing conditions to be an issue. § 25.121(b) and (c) to require takeoff requiring this increased approach climb En route and takeoff flight paths have climb performance to be determined for speed to be used for calculating the similar safety issues. Therefore, we are icing conditions if the effect of ice: (1) approach climb performance in icing proposing requirements for identifying Increases the stall speed at maximum conditions. We consider this small when en route climb flight paths must takeoff weight by more than 3 knots or alleviation to be acceptable since it is be determined for icing conditions that 3 percent, or (2) reduces the climb only relative to the need for increasing are similar to those proposed for takeoff performance determined in § 25.121(b) the approach climb speed for icing flight paths. The only significant by more than half the safety margin conditions. The approach climb difference is that for the en route climb provided by the net gradient adjustment performance must be recalculated with paths, a speed of 1.18 VSR determined required by § 25.115. the holding ice accretion and presented with the en route ice accretion of Section 25.121(a) provides the climb in the AFM regardless of whether the proposed appendix C is compared to the performance requirements for the approach climb speed is adjusted for en route climb speed selected for non- takeoff path segment beginning at liftoff operations in icing conditions. icing conditions instead of comparing and ending when the landing gear is stall speeds with and without ice fully retracted. Since we are assuming H. En Route Flight Paths (§ 25.123) accretions. that ice accretion does not begin until We propose to revise § 25.123(a) by The reason for this difference is to liftoff, only a minimal amount of ice specifying a minimum allowable speed provide a more stringent requirement

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for airplanes that use the minimum be lower than 1.23 VSR0 with the The current § 25.125(a)(2), which allowable en route climb speed of 1.18 landing ice accretion on the airplane if would be redesignated as VSR. (1.18 VSR is the minimum that speed exceeds the VREF for non- § 25.125(b)(2)(i), requires VREF for non- allowable value of VFTO prescribed by icing conditions by more than 5 knots icing conditions to be not less than the § 25.107(g)). Airplanes that use a higher CAS. landing minimum control speed, VMCL. en route climb speed have a larger speed The existing paragraphs (b) through (f) This existing requirement ensures that margin to the stall speed and more would be redesignated as (c) through (g). adequate directional control is available maneuvering capability in the en route Whether landing distances or landing in case an engine fails during a go- climb phase to help offset the negative speeds must be determined specifically around. Under the proposed new rule, effects of ice accumulation. for icing conditions depends on whether the VMCL determined for non-icing Due to differences in their methods of VREF needs to be increased by more than conditions would continue to be used generating thrust, propeller-driven 5 knots CAS to counteract the effect of for icing conditions. This would be airplanes generally have better climb ice on airplane stall speeds. The reasons similar to the takeoff flight phase, where performance at lower airspeeds than behind allowing VREF to increase by up the takeoff minimum control speeds, turbojet-powered airplanes. To optimize to 5 knots CAS in icing conditions VMCG and VMCA, determined for non- performance, the en route climb speed before requiring landing distance icing conditions would continue to be used for propeller-driven airplanes is performance to be recomputed for icing used for icing conditions. Unlike the usually the minimum allowable speed conditions are: takeoff case; however, the continued use • of 1.18 VSR, while the en route climb As part of the flight testing to of the non-icing VMCL is not explicitly speed used for turbojet-powered demonstrate compliance with the stated. We consider the proposed airplanes is usually higher. Therefore, landing distance requirements, we requirements to adequately address this the proposed requirement would be typically evaluate airplane issue without proposing an additional more stringent for propeller-driven controllability when landing at speeds explicit requirement. Section airplanes. We consider the increased lower than the normal landing speeds. 25.125(b)(2)(ii) requires VREF for icing stringency for propeller-driven airplanes We usually perform this evaluation at a conditions to be not less than VREF for to be desirable for the following reasons: speed 5 knots below VREF to cover non-icing conditions. Under • Propeller-driven airplanes generally inadvertent speed variations that may § 25.125(b)(2)(i), VREF for non-icing have deicing systems that cycle on and occur in operational service. Plus or conditions must be not less than VMCL off, allowing ice to accrete on the minus five knots variation from VREF is for non-icing conditions. Taken protected surfaces before removing it. frequently used as a guideline for together, these two proposed Also, these deicing systems typically do evaluating expected operational requirements would allow the VMCL not remove all of the ice with each variations in landing speeds. determined for non-icing conditions to • cycle, leaving some residual ice. Both of Normal approaches in transport continue to be used for icing conditions. these effects result in drag increases that category airplanes are typically flown at To assure that using the VMCL are generally not present on turbojet speeds above VREF to provide speed determined for non-icing conditions airplanes that have ice protection margins to account for wind gusts. will provide safe controllability and systems using hot bleed air from the Although the additional speed should maneuverability for icing conditions, engines. be bled off by the time that the airplane the proposed §§ 25.143(c)(2) and (c)(3) • Propeller-driven airplanes will is over the landing threshold, it may not would require the applicant to show likely be subjected to increased be. Service history does not indicate any that the airplane will be safely exposure to icing conditions, due to safety problems with the resulting controllable and maneuverable during their slower operating speeds, shorter longer landing distance. an approach and go-around and an flight lengths, and lower cruising • Many transport category airplanes approach and landing, both with the altitudes. are flown at a speed 5 knots higher than critical engine inoperative. For added VREF during final approach to counter safety during certification flight testing, I. Landing (§ 25.125) any inadvertent speed loss. Often this these maneuvers may be accomplished We propose to revise § 25.125(a) to additional speed has not been bled off with a simulated engine failure (as identify when the landing distance must before reaching the landing threshold. noted in the proposed advisory material be determined specifically for icing Again, service history does not indicate associated with this proposal). conditions. The proposed requirement any safety problems with the resulting would specify that the landing distance longer landing distance. J. Controllability and Maneuverability— General (§ 25.143) must be determined for icing conditions • A 5-knot increase above the VREF if the VREF in icing conditions exceeds speed for non-icing conditions equates We propose to revise § 25.143 to add the VREF in non-icing conditions by to approximately 3 percent of the 1-g a new paragraph (c) that requires the more than 5 knots CAS. For icing stall speed (slightly less than 3 percent applicant to show that the airplane with conditions, the landing distance would for larger airplanes). This is consistent ice accretions and with the critical be determined with the landing ice with the allowable stall speed increase engine inoperative is safely controllable accretion defined in the proposed proposed for the takeoff path and maneuverable during takeoff, an revision to appendix C. requirements for icing conditions. approach and go-around, and an Additionally, a new paragraph (b) As a further safety consideration for approach and landing; a new paragraph would be added to include the landing the VREF speed, § 25.125(b)(ii)(c) would (i) to identify the ice accretions that distance requirements that would be require that VREF for icing conditions must be used in showing compliance moved from the existing paragraph (a). must provide the same maneuvering with § 25.143 in icing conditions, and to The new paragraph (b) would also set capability (with ice accretions on the introduce two specific controllability the requirements for determining the airplane) as is currently required at VREF requirements that apply to flight in icing landing speeds to use in determining for non-icing conditions. This may conditions; and a new paragraph (j) to the landing distances for both icing and result in an increase to VREF for icing specify tests for ensuring that the non-icing conditions. For icing conditions even if this increase is less airplane has adequate controllability for conditions, the landing speed must not than 5 knots. flight in icing conditions before the ice

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protection system is activated and characterized either by completely controllability criteria proposed in performing its intended function of stalled airflow over the horizontal paragraph (j), we considered the likely removing any ice accretions from stabilizer, or by an elevator hinge duration of this time period and the protected surfaces. moment reversal due to separated flow means that might be used for detecting In addition, existing paragraphs (c) on the lower surface of the horizontal icing conditions and activating the ice through (g) would be redesignated as stabilizer caused by ice accretions on protection system. The proposed paragraphs (d) through (h), and the tailplane. advisory material for part 25, appendix paragraph references in the newly Several incidents and accidents have C, part II(e) would provide additional designated paragraphs (d), (e), and (f) been caused by ICTS. These incidents guidance for determining the would be revised accordingly. and accidents have typically occurred appropriate ice accretion for this testing The requirements proposed in new during landing approach when the based on the means of ice detection. paragraph (c) are intended to ensure that flightcrew either lowered the flaps or Although activation of the ice using the minimum control speeds for abruptly decreased the airplane’s pitch protection system is expected to occur non-icing conditions would not result in attitude. Either of these actions will shortly after entering icing conditions, it controllability and maneuverability increase the angle-of-attack (AOA) of the may not occur for a relatively long time safety concerns when the same speeds local airflow over the tailplane. If there if the method of detecting icing are used for icing conditions. is ice on the tailplane, the increased conditions depends on the crew visually The proposed new paragraph (i)(1) AOA may lead to an ICTS. observing a specified amount of ice would require compliance with all of The proposed pushover maneuver buildup on some reference surface (for § 25.143 in icing conditions except increases the AOA on an ice- example, windshield wiper, icing paragraphs (b)(1) and (2). Sections contaminated tailplane by inducing a probe). To address this concern, 25.143(b)(1) and (2) are excepted from nose down pitch rate. An airplane is not proposed § 25.143(j)(1) requires icing analysis under proposed section susceptible to an ICTS if, during the compliance with all of the requirements 25.21(g). pushover maneuver: of § 25.143 that would apply to flight in These proposed requirements assume • The pilot must continue to apply a icing conditions for this method of a conventional empennage (that is, push force to the pitch control detecting icing conditions. In this case, wing/fuselage/tailplane) configuration. throughout the maneuver (that is, the the ice accretion to be used in showing Special conditions, issued in airplane will not continue the maneuver compliance would be the ice accretion accordance with § 21.16, may be to or toward a zero g load factor unless that would exist before the ice necessary for certification of airplanes the pilot applies a push force to the protection system is activated and is with an unconventional empennage pitch control); and performing its intended function. configuration. • The pilot can promptly recover For airplanes that use other means of Applicants can minimize the number from the maneuver without exceeding detecting icing conditions, the proposed of ice accretions to be tested by using 50 pounds of pull force on the pitch requirements would be less stringent. one accretion that is shown to be the control. This reflects the expectation that the most critical accretion for several flight The proposed pushover maneuver airplane would fly only briefly in icing phases. evolved from earlier criteria developed conditions before activation of the ice In many cases, a thin, rough, layer of shortly after a series of incidents and protection system. Instead of requiring ice (defined as sandpaper ice in the accidents highlighted the safety compliance with all of the requirements proposed revision to appendix C) has concerns related to ICTS. For example, of § 25.143 that apply to flight in icing been shown to have a more detrimental early ICTS test criteria called for conditions, § 25.143(j)(2) would require effect on handling qualities for airplanes executing a pushover to a 0.3 g to 0.4 only a demonstration that the airplane with unpowered control systems than g load factor with a pitch rate of not less is controllable in a pull-up maneuver up larger ice accretions. The effect of than 10 degrees per second in an to 1.5 g load factor, and that there is no sandpaper ice accretions may be more attempt to copy the documented ICTS longitudinal control force reversal significant than larger ice accretions on accident conditions. An aggressive during a pushover maneuver down to a these airplanes. In some cases, such an pushover to zero g was later found to 0.5 g load factor. accretion has resulted in control surface result in the same combination of load hinge moment reversals that required factor and pitch rate, but with the K. Stall Warning (§ 25.207) the flightcrew to apply extremely high advantage of not needing sophisticated We propose to revise paragraph (b) to forces to the controls to regain control test instrumentation to perform the test. require that the means for providing a of the airplane. Applicants would have In addition to the pushover maneuver, warning of an impending stall must be to consider sandpaper ice in showing we propose that applicants demonstrate the same for both icing and non-icing compliance with the proposed the safety of a sideslip maneuver with conditions. There would be one § 25.143(i). an ice-contaminated tailplane, since this exception to this general rule. If the The proposed paragraph (i)(2) would has been shown to be a more critical means of detecting icing conditions require applicants to conduct a ICTS triggering maneuver for some does not involve waiting until some pushover maneuver down to a zero g airplanes. The proposed § 25.143(i)(3) specified amount of ice has accreted on load factor with the critical ice accretion would require that any changes in the a reference surface, then the stall on the airplane. (If the airplane lacks force the pilot must apply to the pitch warning may be provided by a different enough elevator power to get to a zero control to maintain speed with means during the time from when the g load factor, the maneuver may be increasing sideslip angle must steadily airplane first enters icing conditions ended at the lowest load factor increase with no force reversals. until the ice protection system is obtainable.) The purpose of this Proposed § 25.143(j) would address activated and is performing its intended proposed requirement is to evaluate an airplane controllability between the function. airplane’s susceptibility to a time when the airplane first enters icing We propose to add a new paragraph phenomenon known as ice- conditions and when the ice protection (e) to specify the stall warning margin contaminated tailplane stall (ICTS). Ice- system is activated and performing its that the stall warning system must contaminated tailplane stall can be intended function. In developing the provide in icing conditions. The stall

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warning margin is how far in advance general requirement. The conditions for the pilot can safely recover the airplane the pilot is warned of a potential stall. the exception to the general requirement after a stall warning has occurred. This We propose to evaluate the stall would be established in demonstration occurs during the flight warning margin in both straight and § 25.207(h)(2)(ii). tests to show acceptable flight turning flight while decelerating the The general rule of § 25.207(b) may characteristics for stall recovery. For the airplane at rates of up to one knot per result in a different stick shaker time that the airplane is in icing second. The pilot must be able to activation point for icing conditions conditions before the ice protections prevent stalling the airplane using the because the airplane may stall at a system has been activated, if stall same recovery maneuver that would be different speed or AOA with ice warning is provided by a different used in non-icing conditions, starting accretions. In order to maintain a safe means than for non-icing conditions, it the recovery maneuver not less than 3 margin above the stall speed and to may take longer for the flightcrew to seconds after the stall warning begins. provide sufficient maneuvering recognize the impending stall and take Paragraph (e) also specifies the ice capability, an increase in the minimum recovery action. Therefore, instead of accretions that would be used for operating speeds may be needed. allowing a recovery maneuver to be showing compliance. Increasing the minimum operating started one second after the onset of We propose to revise paragraph (f) to speeds, such as takeoff and landing stall warning, the recovery maneuver consist of the existing paragraph (e), speeds, may result in a cost increase if must not begin until at least 3 seconds revised to clarify that the pilot must use operators have to reduce payload to after the onset of stall warning. the same maneuver to demonstrate that comply with performance requirements Paragraph (h)(2)(i) of the proposal the airplane can safely recover from a at the higher operating speeds. allows the recovery to start within one stall in icing conditions as is used for These potential cost impacts may be second of the stall warning. The more non-icing conditions. minimized for stall warning in icing stringent three-second requirement is We propose to add a new paragraph conditions after the ice protection contained in the proposed paragraph (h) to specify the stall warning system has been turned on. Then the (h)(2)(ii). requirements for the time period when higher settings for flight in icing Additionally, proposed paragraph the airplane first enters icing conditions conditions would only be used if the ice (h)(2)(ii) would require the applicant to until the ice protection system is protection system has been activated. show that the airplane has safe handling activated and is performing its intended The higher operating speeds would not qualities in case the flightcrew does not function. The proposed stall warning be a factor, or cost, in other operations. take suitable recovery action in time to requirements would be different for However, this design solution would prevent stalling. Compliance with the different means of detecting icing not protect the airplane during the time stall characteristics requirements of conditions and whether or not the stall that the airplane is in icing conditions § 25.203 would be required for stalls warning is provided by the same means before activation of the ice protection demonstrated using a one knot per for icing conditions and non-icing system. To protect the airplane during second deceleration rate. conditions. this time period, any changes to the stall Earlier, we stated that in most cases, Currently, part 25 requires airplanes warning system settings for potential ice flight in icing conditions before to provide the flightcrew an adequate accretions would need to be active at all activation of the icing system is warning of an impending stall so that times. This would mean that the expected to be relatively brief. However, the flightcrew can prevent the stall. The minimum operating speeds would be if the means of detecting icing current requirement does not consider increased for both icing and non-icing conditions and activating the ice the effects of ice accretions on the conditions with resulting cost protection system depends on the airplane. With ice accretions on the implications. flightcrew visually identifying a discrete airplane, the airplane may stall sooner To minimize the potential cost amount of ice on a reference surface (for (that is, at a higher speed or lower impact, while ensuring flight safety, the example, one-quarter-inch of ice on the AOA), possibly even before the stall FTHWG examined whether different wing’s leading edge), then this warning would occur. For an airplane to stall warning requirements could be temporary condition may be of a be approved for flight in icing used for flight in icing conditions before relatively long duration. Therefore, we conditions, we consider it necessary to activation of the ice protection system. consider it appropriate to apply the provide an adequate stall warning Flight in icing conditions before same requirements for stall warning to margin with ice accretions on the activation of the ice protection system is this case as are applied to the case of airplane. For human factors reasons, we a temporary condition. In most cases, flight in icing conditions after the ice also consider it necessary for the means this time is expected to be relatively protection system is fully active. For of providing the stall warning to be the short. In those cases, proposed this case, we propose that the stall same in icing conditions and non-icing paragraph (h)(2) would allow the stall warning indication must be provided by conditions. But as discussed in the warning to be provided by a different the same means as in non-icing specific proposal for § 25.207(h), we means than is used for non-icing conditions. Proposed paragraph (h)(1) would allow a limited exception to this conditions. For example, natural contains this requirement. general requirement. airplane buffeting might be used instead The FTHWG determined that In most transport category airplanes, of a stick shaker. By allowing a different applying the existing stall warning the stall warning is provided by a device means of stall warning, the need to margin requirements of § 25.207(c) and called a stick shaker, which shakes the change the stall warning system setting (d) to icing conditions would be far control column to alert the pilot when would be minimized. more stringent than best current the airplane is close to stalling. The However, if the stall warning is practices and would unduly penalize proposed addition to § 25.207(b) would provided by a different means than for designs that have not exhibited safety establish the general requirement for the flight in non-icing conditions, the problems in icing conditions. The same means for the stall warning in proposal seeks to balance this with more FTHWG examined whether the stall icing conditions and non-icing stringent flight demonstration warning requirements of existing conditions. Section 25.207(b) would, requirements. The requirements would § 25.207(c) and (d) could be made less however, allow an exception to the be more stringent for demonstrating that stringent for icing conditions without

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compromising safety. The proposed crosswinds are a significant safety O. Inlet, Engine, and Exhaust § 25.207(e) resulted from this effort. concern. Proposed § 25.237(a)(2) Compatibility (§ 25.941) In developing the proposed explicitly states that the takeoff § 25.207(e), the FTHWG determined that crosswind component without icing is We propose to revise the references to the types of transport category airplanes valid for icing conditions. §§ 25.143(c), (d), and (e), contained in involved in icing-related stall accidents: However, the conditions on landing paragraph (c) of § 25.941, to read • Were equipped with deicing boots are different. Before landing, the § 25.143(d), (e), and (f). that operated cyclically (for example, a airplane may spend a significant The proposed changes are necessary boot cycle every one to three minutes), amount of time exposed to icing to maintain references to the correct and conditions. These ice accretions may paragraphs of § 25.143 if the changes to • Were generally very susceptible to affect directional control when § 25.143 being proposed by this large affects on stall speeds from ice crosswinds are encountered close to the rulemaking are adopted. accretions during the periods between ground. As a result, (a)(3)(ii) requires P. Ice Protection (§ 25.1419) boot cycles (known as intercycle ice). evaluation of the landing crosswind The proposed criteria of § 25.207(e), component with ice accretion. We propose to revise the introductory in combination with the proposed text of § 25.1419 to replace the phrase, § 25.207(b), would likely require M. High-Speed Characteristics (§ 25.253) ‘‘If certification with ice protection different stall warning system settings We propose to revise § 25.253 by provisions is desired * * *’’ with ‘‘If for icing conditions and non-icing adding a new paragraph (c) to define the certification for flight in icing conditions on future airplanes with maximum speed for stability conditions is desired * * *’’ The those characteristics. These proposals characteristics, VFC/MFC, for icing current rule requires an applicant to would have a lesser impact on airplanes conditions. The proposal would permit demonstrate an airplane’s ability to without those characteristics. The stall applicants to define a VFC/MFC for icing safely operate in icing conditions only warning settings established for the conditions that is different than the VFC/ when the applicant is seeking to airplane without ice accretions may be MFC defined for non-icing conditions. certificate ice protection features. It fails retained for operation in icing Additionally, § 25.253(b) would be to address certification approval for conditions, provided they are still revised to refer to § 25.143(g) rather than flight in icing conditions for airplanes adequate to prevent stalling if the pilot § 25.143(f) due to the proposed without ice protection features. The does not take any action to recover until renumbering of § 25.143. proposed revision, which would adopt three seconds after the initiation of stall VFC/MFC is the highest speed at which the existing wording from JAR 25.1419, warning. Since all modern conventional compliance with several airplane would require an applicant to transport category airplanes use some handling qualities requirements must be demonstrate the airplane’s ability to type of artificial stall warning system shown. The FTHWG’s review of safely operate in icing conditions (stick shaker or combined aural and historical certification data showed that whenever the applicant is seeking visual warning), and since three seconds none of the flight tests for airplane approval for flight in icing conditions. is considered adequate time for handling qualities performed with ice We also propose to simplify the response by a trained pilot, we agree accretions were conducted above 300 second sentence of § 25.1419 to remove with the FTHWG that this stall warning knots CAS. The air loads associated redundant wording. This change is definition would be acceptable for icing with such high speeds tend to make it editorial in nature and is not intended conditions. difficult to keep either artificial or to change the requirement in any way. The proposed revision of § 25.207(f) natural ice attached to the airframe to We propose to amend § 25.1419 to would require the pilot to use the same accomplish the testing. It also incorporate the revised introductory text stall recovery maneuver during the minimizes the possibility of for the following reasons: compliance demonstration for icing encountering this condition in • conditions as is used for non-icing operational service. Therefore, we A literal reading of the current conditions. This proposal is based on propose that the maximum speed for § 25.1419 wording could imply that the human factors considerations. In demonstrating stability characteristics applicant does not have to demonstrate that the airplane can be safely operated operational service, pilots would not be with ice accretions is the lower of VFC, expected to respond differently to a stall 300 KCAS, or any other speed at which in icing conditions unless an ice warning indication in icing conditions it can be shown that the airframe will protection system is installed. • versus non-icing conditions. be free of ice. The revised text would clarify that any airplane approved to fly in icing L. Wind Velocities (§ 25.237) N. Pilot Compartment View (§ 25.773) conditions must be capable of operating The proposed revisions to § 25.237(a) We propose to revise § 25.773(b)(1)(ii) in the icing conditions of appendix C of would add a requirement to establish a to replace the phrase ‘‘if certification part 25 regardless of whether or not the safe landing crosswind component for with ice protection provisions is airplane has an ice protection system. use in icing conditions. The proposed requested’’ with ‘‘if certification for Q. Part 25, Appendix C revision to paragraph (a) also would flight in icing conditions is requested.’’ state that the crosswind component The proposed change is necessary to We propose to revise appendix C of established for takeoff without ice be consistent with the proposed change part 25 to create two subsections: Part accretions may be used for takeoffs to § 25.1419. As discussed in the reason I to define the atmospheric icing conducted in icing conditions. for revising § 25.1419, compliance with conditions that must be considered For taking off in crosswinds, we icing-related safety of flight when showing compliance with the consider it unnecessary to consider the requirements should depend on icing-related requirements of part 25, effect of ice accretions since these whether the airplane would be and part II to define ice accretions for proposals assume that ice accretions do approved to operate in icing conditions, each phase of flight. We also propose to not begin until liftoff. Therefore, not on whether the airplane has add a definition of the atmospheric airplanes will accrete very little ice, if approved ice protection provisions icing conditions to use specifically for any, while close to the ground where installed. the takeoff phase of flight.

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Proposed Appendix C, Part I height of 1,500 feet above the takeoff appendix C. To perform the evaluation Proposed appendix C, part I would surface (ref. § 25.111(a)), we consider it required by § 25.125(a)(1), an applicant contain the existing appendix C reasonable to assume that the entire would use the landing ice definition definitions of atmospheric icing takeoff phase could be flown within the found in paragraph (5) of this section. To reduce the number of artificial ice conditions. We propose adding a same icing cloud. Therefore, we propose accretions that must be considered, definition of ‘‘takeoff maximum icing,’’ that the takeoff maximum icing proposed part II(b) would permit the ice which is to be used in determining ice conditions would extend from ground accretion determined for one flight accretions for the takeoff phase of flight. level to a height of 1,500 feet above the level of the takeoff surface. phase to be used in showing compliance Proposed Appendix C, Part II Although measured data for liquid with the flight requirements of another Proposed appendix C, part II(a) would water content at low altitudes are phase, provided the applicant can show contain definitions of the ice accretions sparse, a comparison of data contained it has a more critical effect on the flight parameter being evaluated. For example, appropriate to each phase of flight. in the FAA Technical Center’s database on inflight icing conditions with using the ice accretion determined for Proposed appendix C, part II(b) would theoretical predictions suggest a the holding phase to show compliance provide options for reducing the maximum liquid water content within with the requirements for the takeoff number of ice accretions to be the icing cloud of 0.35 grams/meter 3 phase will generally have a larger effect considered for each phase of flight. from ground level up to 1,500 feet. We on performance and therefore be more Proposed appendix C, part II(c) would propose to use this value within the penalizing than using an ice accretion permit applicants to use, for the definition of the maximum takeoff icing determined specifically for the takeoff airplane performance tests, the same ice conditions. This proposed value would phase. accretion used for evaluating handling also cover the potential for dense Proposed part II(c) clarifies that the characteristics. Proposed appendix C, ground fog at freezing temperatures, ice accretion with the most adverse part II(d) would define the conditions which our meteorologists stated would effect on handling qualities may also be for determining the ice accretions for expose the airplane to a liquid water used during the flight test the takeoff phase of flight. Proposed content of approximately 0.30 grams/ demonstrations of performance as long appendix C, part II(e) would define meter 3. as any performance differences are what ice accretion must be considered For the size of the water droplets, conservatively taken into account. This prior to normal ice protection system both industry and FAA icing specialists proposed section is consistent with the operation. concurred that a mean effective intent behind proposed part II(b) to One early concern with developing diameter of 20 microns would be reduce the number of ice accretions that appropriate airplane performance and appropriate for icing conditions must be considered. Unlike handling handling qualities requirements for the occurring near ground level. We qualities, performance effects between takeoff phase of flight was the propose to use this value within the relatively small differences in ice atmospheric icing environment close to definition of the maximum takeoff icing accretion generally can be addressed the ground. The FTHWG members conditions. adequately through analysis. expressed significant concerns with Selection of the ambient temperature Proposed part II(d) states the using the existing appendix C for takeoff icing was based on assumptions under which the takeoff ice atmospheric icing envelopes for this theoretical predictions that showed the accretions are determined. Proposed purpose. The FAA meteorologists effect of temperature to decrease part II(d) also states that it must be confirmed that the existing appendix C significantly as the temperature itself assumed that the crew does not take any atmospheric envelopes are not generally decreased. We propose to use an action to activate the ice protection representative of icing conditions close ambient temperature for the takeoff system until the airplane is at least 400 to the ground. icing atmosphere of minus 9 degrees feet above the takeoff surface. This In general, for determining the size, Celsius (¥9° C), the point at which any requirement is consistent with the shape, location, and texture of ice further decrease in temperature had a existing requirement of § 25.111(c)(4) accretions on the airplane, one needs negligible effect on the resulting ice that limits the types of configuration information about the atmospheric icing accretion. changes requiring crew action before environment, i.e., icing cloud size, According to our meteorologists, the reaching 400 feet above the takeoff cloud liquid water content, water amount of water vapor that can be held surface. droplet size, expressed in terms of the without condensing in a given volume We consider it necessary to also take mean effective diameter of the droplets, of space depends only on the into account the effects of any ice and ambient air temperature. temperature of the gas (water vapor, air, accretion that may form on the airplane We propose to use the following etc.) in that space. It does not vary with from the time the airplane enters icing definition of atmospheric icing altitude. Therefore, the proposed takeoff conditions until the ice protection conditions for takeoff maximum icing icing atmosphere would be equally system is activated and is performing its conditions in appendix C, part I(e): An applicable to all airport runway intended function. The size, shape, icing cloud extending from ground level elevations. location, and texture of this ice to a height of 1,500 feet above the Proposed part II(a) references specific accretion will depend on: (1) The means takeoff surface with a liquid water phases of flight and defines the critical used to identify that the airplane is in content of 0.35 grams/meter 3, water ice accretions associated with the icing conditions (for example, the pilot droplets with a mean effective diameter specific phase of flight. In the main seeing ice accreting on the airplane, an of 20 microns, and an ambient body of the rule, various sections ice detector, a combination of freezing temperature of minus 9 degrees Celsius require evaluation using the ice temperatures and visible moisture), (2) (¥9° C). The following discussion accretion defined in appendix C. the means and procedures for activating presents the reasons for selecting these Proposed part II(a) contains those the ice protection system (for example, values. definitions. For example, § 25.125(a)(1) the pilot manually activating the system Since the takeoff phase of flight is requires evaluation of landing distance after a specified amount of ice builds up relatively short, generally ending at a using the ice accretion defined in or automatic activation), and (3) the

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system characteristics (for example, the be performed to zero g, the group did promptly recover from the maneuver without time it takes to effectively remove the not reach a consensus on whether the exceeding 50 pounds pull control force. ice). We propose to define the ice pilot should be required to apply a push Further supporting rationale: FAA accretion applicable to the time period force to the longitudinal control system Advisory Circular 25–7A, ‘‘Flight Test before the ice protection system has throughout the maneuver until a zero g Guide for Certification of Transport been activated and is performing its load factor is attained. The FTHWG Category Airplanes,’’ defines the intended function as a period of time in considered two alternatives. boundaries of various flight envelopes. the continuous maximum icing Alternative 1 was developed by With regard to the minimum load factor conditions of proposed part I of FTHWG members who did not support with flaps down: appendix C, including: our proposal of requiring a push force • The normal flight envelope (NFE) • The time for recognition, to be maintained down to zero g load goes to 0.8 g; • A delay time appropriate to the factor in the pushover maneuver. These • The operational flight envelope means of ice detection and activation of FTHWG members disagreed with the (OFE) goes to 0.5 g; and the ice protection system, and proposal for the following reasons: • • The limit flight envelope (LFE) goes The time needed for the ice • Historically, the pushover test was to zero g. protection system to perform its performed to a 0.5 g load factor rather Conceptually, the boundaries of the intended function after manual or than zero g. For example, as practiced OFE are as far as the pilot is expected automatic activation. by Transport Canada (the Canadian to go intentionally, while the LFE is III. Discussion of Non-Consensus Issues airworthiness regulatory authority), this based on structural or other limits that demonstration was done with a high should not be exceeded. Between the One of the goals of the ARAC process pitch rate. Consequently, there was OFE and the LFE, it is acceptable for is consensus on the proposed significant overshoot of the 0.5 g load degraded handling qualities, but the recommendations. Due to the variety of factor, down to approximately 0.25 g or airplane must remain controllable and it interests represented in the FTHWG, less. This maneuver was intended to be must be possible to avoid exceeding the this goal was not fully achieved. The a controllability test beginning with the limit load factor (see § 25.143(b)). areas of non-consensus, however, were pilot abruptly pushing on the control Although existing regulations do not confined to specific details within the column to achieve a high nose-down allow force reversals (for example, from proposals, and not to the overall need to pitch rate, followed by a pull to recover. a push force on the control column to amend part 25 to address airplane The intent was not to reach a specific a pull force in this case) for the en route performance and handling qualities in g level below 0.5 g, but to show that the flight phase, in practice, the certification icing conditions. The issues for which pilot could perform a satisfactory tests for these rules do not cover the full full consensus was not achieved within recovery. This has proven to be an structural limit flight envelope. Rather, the FTHWG were: 1. The requirement that a push force acceptable test technique. To date, the certification tests cover a reasonable must be needed throughout the airplanes evaluated with this technique range of load factors sufficient to cover pushover maneuver proposed in the have had a satisfactory safety record in normal operations. For example, in the new § 25.143(i)(2); service. en route configuration, where the limit • 2. Whether the test to evaluate Since the beginning of the 1980s, minimum load factor is usually negative longitudinal handling qualities during the practice of many certification 1 g, the JAA’s Advisory Circular Joint sideslip maneuvers should be required authorities has been to require testing to (ACJ) No. 2 to JAR 25.143(f) states: by regulation as proposed in the new lower load factors. This evolved until ‘‘* * * assessment of the characteristics § 25.143(i)(3), or should only be the introduction of the JAA’s NPA 25F– in the normal flight envelope involving included in advisory material as one 219, which not only requires testing to normal accelerations from 1 g to zero g, means of showing compliance; zero g, but also requires a push force will normally be sufficient.’’ 3. Whether the same airplane throughout the maneuver to zero g. A With flaps up, zero g is the midpoint performance and handling qualities zero-g pushover is considered to be an between the limit load factor and the requirements (§§ 25.143(j) and improbable condition, going well trim point. The corresponding points for 25.207(h)) should always apply beyond any operational maneuver, and flaps down are zero g for the limit load whenever the means to activate the ice does not properly represent gusts, pitch factor and 0.5 g for the midpoint protection system depends on the pilot rate, elevator position, or other factors assessment of characteristics. The to visually identify when the airplane is that may contribute to tailplane stalls. supporters of alternative 1 to in icing conditions; and Also, since the NPA requirement was § 25.143(i)(2) are concerned that 4. Whether the proposed revision to developed for a specific turboprop, and requiring a push force to zero g means appendix C adequately ensures that the motivated by service experience on that this limit load factor will be full range of variables are considered in turboprop airplanes, other requirements routinely exceeded in the flight tests determining what the critical ice were proposed for other types of used to show compliance with the accretion is for a particular flight phase. airplanes. proposed rule. Each of these non-consensus issues is For the above reasons, the supporters The zero-g pushover is not like typical discussed in more detail below. of alternative 1 to § 25.143(i)(2) consider stability tests where it is possible to that requiring a push force to load establish steady state conditions and A. Non-Consensus Issue 1— factors as low as zero g is excessive. measure a repeatable control force. The § 25.143(i)(2) Instead, they recommend replacing pushover is an extremely dynamic The FTHWG did not reach a proposed § 25.143(i)(2) with: maneuver lasting only a few seconds consensus on the issue of requiring a and involving high pitch rates in both The airplane must be controllable in a push force throughout the maneuver pushover maneuver down to zero g, or the directions. There will always be down to a zero g load factor (or the lowest load factor obtainable if limited by variability due to pilot technique. The lowest load factor obtainable if limited elevator power. It must be shown that a push pilot may pull slightly before reaching by elevator power). Although there was force is required throughout the maneuver zero g to reduce the nose-down pitch consensus that the test maneuver should down to 0.5 g. It must be possible to rate and anticipate the recovery. This

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makes it impossible to distinguish the anti-ice system off) than the types event involved a sudden nose-down between the force required to reach a that have had accidents. pitch-over from 1-g flight like the ICTS given g level and the force the pilot Ice-contaminated tailplanes retain accident scenarios. The same ice applies to track the targeted pitch rate. normal linear characteristics until the accretion had degraded pushover At critical conditions, airplanes that onset of flow separation. The separation characteristics to the point that a 50- meet the criterion suggested in the causes the hinge moment coefficient to pound pull was required to recover from alternative proposal still require a slope gradually from one level to zero g with flaps 10, and 100 pounds significant pull force to recover. another over a range of 4 to 10 degrees was required with flaps 20. Alternative 1 to § 25.143(i)(2) would AOA. With the elevator down, the hinge Accordingly, the criteria proposed as set a limit of 50 pounds on the total moment coefficient changes sign at an alternative 1 to § 25.143(i)(2) provide an control force needed to recover AOA in this range, which results in the adequate safety margin, and would have promptly. This would ensure that the control force reversal from a push to a identified the aircraft as unacceptable force that the pilot must exert is low pull. On a particular business jet with before it ever got to the flaps 40 enough so that even with only one hand a relatively small elevator, this results in configuration at which it lost control. on the pitch control (the other hand a gradually increasing pull force from 0 We disagree with the position of the might be on the thrust levers or another pounds at approximately 0.4 g to 25 supporters of alternative 1 to control), the pilot can handle a pounds at zero g. § 25.143(i)(2) for the following reasons: combination of: On airplanes with large unpowered a. Ice contaminated tailplane stall/ • The force to halt the nose-down elevators, especially those with long elevator hinge moment reversal has pitch rate, chord lengths, the elevator control been a significant factor in accidents • The force due to any hinge moment forces resulting from a stalled tail can be occurring in icing conditions. Rapid and reversal, and very high. These forces may even be too large changes in pitch, significant • The force to establish a satisfactory high for the pilots to counteract. For changes in control forces, pilot surprise, nose-up pitch rate for recovery. example, assume the elevator and possible disorientation in poor The 50-pound limit is used for a dimensions of the previous example are visibility that can follow from a similar purpose in several other rules. scaled up by a factor of 2. The elevator tailplane stall/elevator hinge moment The effect of data scatter and variations chord is then doubled, the area is reversal can result in loss of pitch in pilot technique will cause airplanes quadrupled, and the pilot must exert 8 control. Coupled with the weather that are not clearly free of ICTS times as much force on the control to conditions that lead to ICTS, this loss of concerns to exceed the 50-pound limit move the elevator. If the control force in control will usually occur at low too often, so they will not pass this test. the previous example were 25 pounds at altitude where there is a higher The supporters of alternative 1 to zero g, the control force for this larger probability of an accident. § 25.143(i)(2) believe that the proposal elevator would be 200 pounds. These b. Historically, the pushover test was contained in this rulemaking has the examples illustrate how the size and usually performed to 0.5 g load factor, potential for adversely affecting an design of elevators for certain airplanes although this was often done with a entire class of airplanes—namely light determine whether the control forces high pitch rate and, hence, there was to medium business jets with trimmable would be acceptable or hazardous. The some overshoot of the 0.5 g load factor. stabilizers and unpowered elevators. test criteria recommended for showing A push force on the elevator control was Many of these airplanes exhibit a mild compliance with the requirements required to reach this g level. control force reversal from a push force proposed as alternative 1 to Certification testing and service to a pull force between zero g and 0.5 § 25.143(i)(2) would identify those experience has since shown that testing g. airplanes with the hazardous to only to 0.5 g is inadequate, Although such a characteristic will characteristics. Therefore, the considering the relatively high not comply with the proposed rule, the supporters of alternative 1 to frequency of experiencing 0.5 g in airplane remains easily controllable. § 25.143(i)(2) believe that there is no operations. Since the beginning of the The proposed requirement for a push difference in safety between this 1980s, the practice of many certification force to be required down to a zero g alternative and our proposal. authorities has been to require testing to load factor would reduce the stabilizer Results of the National Aeronautics lower load factors, and the JAA’s Notice incidence available for trimming the and Space Administration’s (NASA) of Proposed Amendment (NPA) 25F– airplane by two to four degrees. This Tailplane Icing Program provide a basis 219 requires a push force throughout the would require either a 20 to 40 percent for evaluating whether the proposed maneuver to zero g. larger stabilizer or other design changes requirements adequately address the c. Reversal of elevator control force to compensate for the reduction in safety concerns. Flight tests were versus normal acceleration is not stabilizer trim range. The supporters of conducted in which a test airplane acceptable within the flight envelope. alternative 1 to § 25.143(i)(2) do not performed a series of pushovers and Existing requirements and advisory believe that the cost of these changes is other maneuvers with and without ice material addressing elevator control justified by any safety benefit, as these accretions. Even without ice accretions, force characteristics (§§ 25.143(f), airplanes are not the types having ICTS reversed control forces were sometimes 25.255(b)(2), and the guidance material accidents. experienced in the pushover maneuvers to § 25.143(f)) do not allow force Furthermore, the proposed for some configurations. With the ice reversals. Furthermore, a survey of FAA, § 25.143(i)(1) would require that accretions, control forces exceeding 100 JAA, and other flight test personnel sandpaper ice be considered if the pounds were experienced in some of the showed that a clear majority did not elevator is unpowered, regardless of the pushovers although the airplane favor anything less than a push force on ice protection system. Many of the remained controllable. In one test, a the elevator control to zero g. current business jets are equipped with departure from controlled flight Alternative 1 to § 25.143(i)(2) would anti-ice systems that prevent ice occurred during a power transition with at least partially address the cause of formation on the stabilizer leading edge. a critical ice accretion and flaps 40 past ICTS accidents. However, the Thus, the jets would be evaluated under (which is the maximum landing flap method proposed for determining the more critical assumptions (that is, with configuration for this airplane). This acceptability of a control force reversal

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is subjective and would lead to combining pitch rate with a normal issue; the only difference appears to be inconsistent evaluations. We maintain acceleration in a requirement is whether it should be addressed in that a push force to zero g with an ice- probably too complex, especially for the advisory material or in the proposed contaminated tailplane is the minimum wide range of aircraft designs rule. We consider that this issue raises standard that can be accepted. Zero g is encompassed by part 25 and the parallel important safety concerns that must be within the flight envelope of the JAR–25 standards. Thus, Transport addressed as a specific evaluation airplane and this criterion addresses the Canada considers that, if the requirement. Therefore, it is appropriate need to have acceptable handling requirement would only specify a ‘g’ to place it in the rule rather than in an qualities for operational service when level, then 0.5 g for positive stability is AC. We recognize that AC material may the pilot would not expect any control inadequate. As a compromise, Transport also be needed to provide guidance on force reversal. Requiring a push force to Canada proposes requiring a push force an acceptable means of compliance. zero g also removes subjectivity in the down to a value of 0.25 g as alternative C. Non-Consensus Issue 3— assessment of the airplane’s 2 to § 25.143(i)(2). §§ 25.143(j)(1) and 25.207(h) controllability and provides readily While it is a compromise between the understood criteria of acceptability. Any requirement proposed in this The proposed new §§ 25.143(j)(1) and lesser standard would not give rulemaking and alternative 1 (by 25.207(h) would apply different confidence that the problem has been specifying 0.25 g for the push force requirements when different means are fully addressed. requirement), we disagree with this used for the pilot to visually recognize Transport Canada proposed the alternative because it does not fully icing conditions. Compliance with all of following alternative as a compromise address the safety concerns throughout the § 25.143 controllability requirements between requiring a push force to either the flight envelope. It also does not fully for non-icing conditions would apply if zero g or 0.5 g: address the cost concerns expressed activation of the ice protection system Transport Canada advisory material within the FTHWG regarding depends on seeing a specified ice dating back to the mid-1980s specified § 25.143(i)(2) as proposed in this accretion on a reference surface (for that applicants must demonstrate ± 0.5 rulemaking. example, on an ice accretion probe, or g applied to the longitudinal control. In The Transport Canada alternative a wing leading edge). However, less practice, the demonstration was done in recognizes the importance of pitch rate. stringent requirements using a lesser ice a fairly abrupt maneuver that generated An abrupt nose-down control input is accretion would apply to any other a significantly higher transient pitch required to reach zero g. We consider means of identifying icing conditions, rate than that associated with a steady that testing to zero g, however, ensures including seeing the first indication of normal acceleration. The minimum that high pitch rates are adequately an ice accretion on a reference surface. normal acceleration obtained was evaluated without the added The FTHWG did not reach a usually around 0.25 g or less. It was complication of specifying a pitch rate consensus on the proposed considered that the pitch rate aspect requirement. § 25.143(j)(1). The Air Line Pilots was just as important as the actual Association (ALPA), which was B. Non-Consensus Issue 2— normal acceleration in determining represented in the FTHWG, disagrees § 25.143(i)(3) whether there were unsafe with the proposal. The ALPA considers characteristics associated with tailplane The proposed new § 25.143(i)(3) visually recognizing the first indication stall. No pass/fail criteria were provided would add a requirement that any of ice accreting on a reference surface to in the Transport Canada guidance changes in longitudinal control force to be the same situation as visually except that the characteristics had to be maintain speed with increasing sideslip recognizing a specific amount of ice satisfactory. angle be progressive with no reversals or accretion on a reference surface. To the The accident record on ice unacceptable discontinuities. The ALPA, both are means of visual contaminated tailplane stall indicates FTHWG did not reach a consensus on recognition that require the flightcrew to that a significant factor was the pilot’s whether it would be necessary to add a monitor conditions outside the cockpit. startled reaction to an abrupt hinge specific regulatory requirement to Whenever it is necessary for the pilots moment reversal and the magnitude of address this issue. The majority of the to check outside the cockpit (which the the control force required to recover the FTHWG members felt that there did not ALPA does not consider to be airplane to a normal 1 g condition. appear to be sufficient data to establish equivalent to a primary instrument Alternative 1 to § 25.143(i)(2) would criteria specific enough to stand as a visual scan pattern), the ALPA believes recognize this controllability issue by regulatory requirement and proposed that the same basic maneuver limiting the amount of pull force that the issue be addressed through non- capabilities, stall protection required to promptly recover the regulatory guidance material. requirements, and ice accretion amounts airplane from a zero g condition to a 50- Anomalies in longitudinal control should apply. pound pull force. In addition, force during sideslip maneuvers have The ALPA proposes the following recognizing that positive stability is also been of concern to some accident alternative text for § 25.143(j)(1): important, alternative 1 to § 25.143(i)(2) investigators and regulatory specialists. ‘‘If normal operation of any ice would require a push force down to 0.5 At one time, we proposed that pushover protection system is dependent upon g. maneuvers be conducted while in visual recognition of ice accretion, the Accident data available to Transport sideslips. Transport Canada considered requirements of § 25.143 are applicable Canada indicate that aircraft involved in that performing sideslips in a pushover with the ice accretion defined in incidents and/or accidents incurred a maneuver was excessive, but proposed appendix C, part II(e).’’ tailplane stall at approximately 0.3 g to recognizing the concern, proposed an The ALPA has similar concerns with 0.4 g. Based on this data and Transport additional requirement that would the proposed § 25.207(h)(1) and Canada’s past practice, alternative 1 to specifically assess longitudinal control proposes the following alternative text: § 25.143(i)(2) would be acceptable, stick forces while in sideslip ‘‘If normal operation of any ice except that the issue of pitch rate is not maneuvers. protection system is dependent upon specifically identified in the criteria. We consider that a consensus was visual recognition of ice accretion, the Transport Canada recognizes that reached on the need to address this requirements of this section, except

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paragraphs (c) and (d), are applicable atmospheric conditions are considered. consider ice accretions for all phases of with the ice accretion defined in The alternative text would read: flight and all configurations of high lift appendix C, part II(e).’’ Section 25.21(g) states that if certification devices. The proposed rule would We disagree with the alternative for flight in icing conditions is desired, the require consideration of the effects of proposals for §§ 25.143(j)(1) and applicable requirements of subpart B must be the ice accretion during the phases of 25.207(h)(1). met in the icing conditions of appendix C, flight with high lift devices extended. The FTHWG found that there are unless otherwise prescribed. The most The associated proposed advisory significant differences in the critical ice accretion in terms of handling material specifically recommends that aerodynamic effects on an airplane characteristics and performance for each natural icing flight testing with high lift flight phase must be determined, taking into devices extended in the approach and between the two different means of consideration the atmospheric conditions of visual recognition of icing conditions part I of this appendix, and all flight landing conditions be conducted. identified in the ALPA alternative conditions within the operational limits of We do not concur with the alternative proposal discussion. The best example the airplane (for example, configuration, discussed above. The research referred of the means covered by §§ 25.143(j)(1) configuration changes, speed, angle-of-attack, to above determined the effect on lift and 25.207(h)(1), as proposed in this and altitude). The following ice accretions and drag of a spoiler-like shape located notice, are airplanes with pneumatic must be determined: at various chord locations of a two deicing boots. The operating procedures The NASA research following the dimensional airfoil. (A two dimensional call for a specified amount of ice build- Model ATR–72 accident at Roselawn, airfoil is a wing with an infinite up before activating the ice protection Indiana, in 1994, observed that wingspan, that is, there are no wingtips. system, a process that is repeated often decreasing AOA causes an increase in It is common practice for wind tunnel during an icing encounter. In this case, aft ice accretion limit on the upper testing to use wings that span the test the airplane is assured of being operated surface of an airfoil. Likewise, the fact section from one wall of the wind with some level of aerodynamic that airflow separation on the negative tunnel to the other. Results obtained for degradation before activation of the ice pressure side (upper surface for a a two dimensional airfoil must usually protection system. typical wing) is caused by ice accretions be adjusted to properly represent a real The best example of the second type on the upper surface is discussed. wing.) These data do not support the of visual recognition of icing conditions Research performed by Dr. Michael B. alternative position because no data are airplane models that are equipped Bragg and others at the University of were presented in the references to with an ice accretion probe in the pilot’s Illinois has demonstrated significant connect either this shape or its location field of view outside the airplane. The variation in the effects on airfoil with airplane flight conditions or icing published procedure calls for activating aerodynamics of a simulated ice conditions, either inside or outside of the ice protection system at the first accretion depending upon its location proposed appendix C. There were no indication of ice buildup on the on the negative pressure side of the data showing the effect of the shape on accretion probe. Such accretion probes, airfoil. an airfoil with high lift devices or an equivalent such as a windshield Differing airspeeds and high lift extended. wiper post, are highly efficient ice device configurations significantly The effect of any shape on a two- collectors, and typically will accrete change the AOA and, consequently, the dimensional airfoil is much larger than visible ice prior to ice accretion on location of the stagnation point around the effect of a similar shape on a aerodynamic surfaces. Under this means which any ice accretion forms on an complete airplane with high lift devices of detecting icing conditions, there may airfoil. For normal operation, this extended, and the effect of such a shape be little or no ice buildup on should make no difference on surfaces diminishes with increasing airplane aerodynamic surfaces before activation that are protected by the icing system. size. and normal operation of the ice But for unprotected surfaces, in the The effect of ice accretions similar to protection system, and little or no failure case and for ice that accumulates the shapes tested in the referenced aerodynamic degradation. These two prior to normal system operation, report were also considered by the means of visually recognizing that icing changing the location of ice on the FTHWG when it discussed ice accreted conditions are present are distinctly negative pressure side of the airfoil may in conditions outside of proposed different. be significant. Procedural restrictions appendix C. The majority of the FTHWG (that is, no holding with flaps extended, recommended not including these D. Non-Consensus Issue 4—Appendix C speed or configuration restrictions in accretions in the recommendations The ALPA representative on the case of ice system failure, etc.) could be because the only icing design envelope FTHWG did not consider that the used to limit the configurations available is proposed appendix C. combination of the proposed regulatory necessary to determine the most critical IV. Rulemaking Notices and Analyses changes and associated proposed ice accretion. However, the full range of advisory material provided a definitive possible accumulation locations must be Paperwork Reduction Act enough description of the required ice considered. The Paperwork Reduction Act of 1995 accretions, particularly with regard to In their report on the Embraer Model (44 U.S.C. 3507(d)) requires that the the variables that must be considered in EMB 120 accident at Monroe, Michigan, FAA to consider the impact of determining the critical ice accretion for in 1997, the NTSB concluded that: paperwork and other information a particular flight phase. The ALPA The icing certification process has been collection burdens imposed on the alternative proposal recommends inadequate because it has not required public. We have determined that there adding specific references to ‘‘all flight manufacturers to demonstrate the airplane’s are no current new information conditions within the operational limits flight handling and stall characteristics under collection requirements associated with of the airplane’’ and ‘‘configuration a sufficiently realistic range of adverse this proposed rule. changes’’ to the general ice accretion accretion/flight handling conditions. requirements of proposed part II(a) of (Finding #27) International Compatibility appendix C to ensure that the full range The recommendations submitted by In keeping with U.S. obligations of possible accretion locations for the FTHWG, and this proposed rule, under the Convention on International

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Civil Aviation, it is FAA policy to private sector, of $100 million or more Benefits of This Rulemaking comply with International Civil annually (adjusted for inflation). Aviation Organization (ICAO) Standards In conducting these analyses, FAA The benefits of this proposed rule and Recommended Practices to the has determined this rule (1) has benefits consist of the value of lives saved due maximum extent practicable. The FAA that justify its costs, (2) is not a to avoiding accidents involving part 25 has determined that there are no ICAO ‘‘significant regulatory action’’ as airplanes operating in icing conditions. Standards and Recommended Practices defined in section 3(f) of Executive We estimate that a total of 13 fatalities that correspond to these proposed Order 12866, and is not ‘‘significant’’ as could potentially be avoided by regulations. defined in DOT’s Regulatory Policies adopting the proposed rule. We use $3.0 million as the value of an avoided Executive Order 13132, Federalism and Procedures; (3) would not have a significant economic impact on a fatality. Over the 45-year period of The FAA analyzed this proposed rule substantial number of small entities; (4) analysis, the potential benefit of the under the principles and criteria of would have a neutral impact on proposed rule would be $89.9 million Executive Order 13132, Federalism. We international trade; and (5) does not ($23.7 million in present value at seven determined that this action would not impose an unfunded mandate on state, percent). have a substantial direct effect on the local, or tribal governments, or on the Cost of This Rulemaking States, on the relationship between the private sector. These analyses, available national Government and the States, or in the docket, are summarized below. We estimate the costs of this proposed on the distribution of power and rule to be about $66.4 million ($22.0 responsibilities among the various Total Benefits and Costs of This million in present value at seven levels of government, and therefore Rulemaking percent) over the 45-year analysis would not have federalism implications. The estimated cost of this proposed period. The total cost of $66.4 million Regulatory Evaluation, Regulatory rule is $66.4 million ($22.0 million in equals the fixed certification costs of Flexibility Determination, International present value at seven percent). The $6.7 million incurred in the first year Trade Impact Assessment, and estimated potential benefits of avoiding plus the variable annual fuel burn cost Unfunded Mandates Assessment 13 fatalities are $89.9 million ($23.7 of $59.7 million. million in present value at seven This portion of the preamble Regulatory Flexibility Determination summarizes the FAA’s analysis of the percent). economic impacts of a proposed rule Who Is Potentially Affected by This The Regulatory Flexibility Act of 1980 amending part 25 of 14 CFR to change Rulemaking (RFA) establishes ‘‘as a principle of the regulations applicable to transport • Operators of part 25 U.S.-registered regulatory issuance that agencies shall category airplanes certificated for flight aircraft conducting operations under 14 endeavor, consistent with the objective in icing conditions. It also includes CFR parts 121, 129, 135, and of the rule and of applicable statutes, to summaries of the initial regulatory • fit regulatory and informational flexibility determination. We suggest Manufacturers of those part 25 aircraft. requirements to the scale of the readers seeking greater detail read the business, organizations, and full regulatory evaluation, which is in Our Cost Assumptions and Sources of governmental jurisdictions subject to the docket for this rulemaking. Information regulation.’’ To achieve that principle, Introduction This evaluation makes the following the RFA requires agencies to solicit and consider flexible regulatory proposals Changes to Federal regulations must assumptions: • and to explain the rationale for their undergo several economic analyses. The base year is 2003. • This proposed rule is assumed to actions. The RFA covers a wide-range of First, Executive Order 12866 directs that small entities, including small each Federal agency propose or adopt a become a final rule in 2 years, and will then be effective immediately. businesses, not-for-profit organizations regulation only upon a reasoned and small governmental jurisdictions. determination that the benefits of the • The production run for newly intended regulation justify its costs. certificated airplane models is 20 years. Agencies must perform a review to Second, the Regulatory Flexibility Act • The average life of an airplane is 25 determine whether a proposed or final of 1980 requires agencies to analyze the years. rule will have a significant economic economic impact of regulatory changes • We analyzed the costs and benefits impact on a substantial number of small on small entities. Third, the Trade of this proposed rule over the 45-year entities. If the agency determines that it Agreements Act (19 U.S.C. 2531–2533) period (20 + 25 = 45) 2005 through will, the agency must prepare a prohibits agencies from setting 2049. regulatory flexibility analysis as standards that create unnecessary • We used a 10-year certification described in the Act. obstacles to the foreign commerce of the compliance period. For the 10-year life- However, if an agency determines that United States. In developing U.S. cycle period, the FAA calculated an a proposed or final rule is not expected standards, this Trade Act requires average of four new certifications would to have a significant economic impact agencies to consider international occur. on a substantial number of small standards and, where appropriate, to be • We performed sensitivity analysis entities, section 605(b) of the 1980 RFA the basis of U.S. standards. Fourth, the on present value discount rates of one, provides that the head of the agency Unfunded Mandates Reform Act of 1995 three, and the base case seven percent. may so certify and a regulatory (Pub. L. 104–4) requires agencies to • New airplane certifications will flexibility analysis is not required. The prepare a written assessment of the occur in year one of the analysis time certification must include a statement costs, benefits, and other effects of period. providing the factual basis for this proposed or final rules that include a • Value of fatality avoided—$3.0 determination, and the reasoning should Federal mandate likely to result in the million (Source: ‘‘Treatment of Value of be clear. This proposed rule would not expenditure by State, local, or tribal Life and Injury In Economic Analysis,’’ have a significant economic impact on governments, in the aggregate, or by the (FAA APO Bulletin, February 2002).) a substantial number of small entities.

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International Trade Impact Assessment requirements of Title II of the Act, • Would the proposed regulations be therefore, do not apply. easier to understand if they were The Trade Agreement Act of 1979 divided into more (but shorter) sections? Regulations Affecting Intrastate prohibits Federal agencies from • Is the description in the NPRM Aviation in Alaska establishing any standards or engaging preamble helpful in understanding the in related activities that create Section 1205 of the FAA proposed regulations? unnecessary obstacles to the foreign Reauthorization Act of 1996 (110 Stat. Please send your comments to the commerce of the United States. 3213) requires the Administrator, when address specified in the FOR FURTHER Legitimate domestic objectives, such as modifying regulations in Title 14 of the INFORMATION CONTACT section. [new safety, are not considered unnecessary CFR in a manner affecting intrastate template uses ADDRESSES] obstacles. The statute also requires aviation in Alaska, to consider the Environmental Analysis consideration of international standards extent to which Alaska is not served by and, where appropriate, that they be the transportation modes other than FAA Order 1050.1E identifies FAA basis for U.S. standards. The FAA has aviation, and to establish such actions that are categorically excluded assessed the potential effect of this regulatory distinctions as he or she from preparation of an environmental proposed rule and determined that it considers appropriate. Because this assessment or environmental impact would impose the same costs on proposed rule would apply to the statement under the National domestic and international entities and certification of future designs of Environmental Policy Act in the thus have a neutral trade impact. transport category airplanes and their absence of extraordinary circumstances. The FAA has determined this proposed Unfunded Mandates Assessment subsequent operation, it could, if adopted, affect intrastate aviation in rulemaking action qualifies for the The Unfunded Mandates Reform Act Alaska. The FAA therefore specifically categorical exclusion identified in of 1995 (the Act) is intended, among requests comments on whether there is paragraph number 312f and involves no other things, to curb the practice of justification for applying the proposed extraordinary circumstances. imposing unfunded Federal mandates rule differently in intrastate operations Regulations That Significantly Affect on State, local, and tribal governments. in Alaska. Energy Supply, Distribution, or Use Title II of the Act requires each Federal Plain Language agency to prepare a written statement The FAA has analyzed this NPRM assessing the effects of any Federal Executive Order 12866 (58 FR 51735, under Executive Order 13211, Actions Concerning Regulations that mandate in a proposed or final agency Oct. 4, 1993) requires each agency to Significantly Affect Energy Supply, rule that may result in an expenditure write regulations that are simple and Distribution, or Use (May 18, 2001). We of $100 million or more (adjusted easy to understand. We invite your have determined that it is not a annually for inflation) in any one year comments on how to make these ‘‘significant energy action’’ under the by State, local, and tribal governments, proposed regulations easier to executive order because it is not a in the aggregate, or by the private sector; understand, including answers to ‘‘significant regulatory action’’ under such a mandate is deemed to be a questions such as the following: Executive Order 12866, and it is not ‘‘significant regulatory action.’’ The Are the requirements in the proposed likely to have a significant adverse effect FAA currently uses an inflation- regulations clearly stated? on the supply, distribution, or use of adjusted value of $120.7 million in lieu • Do the proposed regulations contain energy. of $100 million. This proposed rule unnecessary technical language or does not contain such a mandate. The jargon that interferes with their clarity? V. Appendixes to the Preamble

APPENDIX I.—LIST OF ACRONYMS USED IN THIS DOCUMENT [For your reference and ease of reading, the following list defines the acronyms that are used throughout this document. This appendix will not appear in the Code of Federal Regulations.]

Acronym Definition

AC ...... Advisory Circular. ACJ ...... Advisory Circular Joint (issued by JAA). AFM ...... Airplane Flight Manual. ALPA ...... Air Line Pilots Association. AMJ ...... Advisory Material Joint (issued by JAA). AOA ...... Angle-of-Attack. ARAC ...... Aviation Rulemaking Advisory Committee. CAS ...... Calibrated Airspeed. CS ...... Certification Specifications (EASA airworthiness standards). EASA ...... European Aviation Safety Agency. FAA ...... Federal Aviation Administration. FTHWG ...... Flight Test Harmonization Working Group. ICTS ...... Ice-Contaminated Tailplane Stall. IPHWG ...... Ice Protection Harmonization Working Group. JAA ...... Joint Aviation Authorities. JAR ...... Joint Aviation Requirements (JAA airworthiness standards). LFE ...... Limit Flight Envelope. NASA ...... National Aeronautics and Space Administration. NFE ...... Normal Flight Envelope. NPA ...... Notice of Proposed Amendment (issued by JAA or EASA). NPRM ...... Notice of Proposed Rulemaking. NTSB ...... National Transportation Safety Board. OFE ...... Operational Flight Envelope.

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APPENDIX I.—LIST OF ACRONYMS USED IN THIS DOCUMENT—Continued [For your reference and ease of reading, the following list defines the acronyms that are used throughout this document. This appendix will not appear in the Code of Federal Regulations.]

Acronym Definition

SLD ...... Supercooled Large Drop. V1 ...... The maximum speed in the takeoff at which the pilot must take the first action (for example, apply brakes, reduce thrust, deploy speed brakes) to stop the airplane within the accelerate-stop distance. V1 also means the minimum speed in the takeoff, following a failure of the critical engine at VEF, at which the pilot can continue the takeoff and achieve the re- quired height above the takeoff surface within the takeoff distance. V2 ...... Takeoff Safety Speed. (The target speed to be reached by the time the airplane is 35 feet above the takeoff surface.) VDF/MDF ...... Demonstrated Flight Diving Speed. VEF ...... Engine Failure Speed. The speed at which the critical engine is assumed to fail during takeoff. VFC/MFC ...... Maximum Speed for Stability Characteristics. VFE ...... Maximum Flaps Extended Speed. VFTO ...... Final Takeoff Speed. The speed at which compliance is shown with the final takeoff climb gradient requirements of § 25.121(c). VMC ...... Minimum Control Speed with the critical engine inoperative. VMCA ...... Air Minimum Control Speed. (Commonly used terminology for VMC.) VMCG ...... Ground Minimum Control Speed. VMCL ...... Landing Minimum Control Speed. VMO/MMO ...... Maximum Operating Limit Speed. VMU ...... Minimum Unstick Speed. The minimum airspeed at and above which the airplane can safely lift off the ground and con- tinue the takeoff. VR ...... Rotation Speed. The speed at which the pilot first makes an input to the airplane controls to rotate the airplane to the takeoff pitch attitude. VREF ...... Landing Reference Speed. VS 1–g ...... 1–g Stall Speed. The calibrated airspeed at which aerodynamic forces alone can support the airplane in 1–g flight. VSR ...... Reference Stall Speed. VSR may not be less than VS 1–g. For airplanes with a device that abruptly pushes the nose down at a selected angle of attack, (for example, a stick pusher), VSR may not be less than 2 knots or 2 percent, whichever is greater, above the speed at which the device operates. VSR0 ...... Reference Stall Speed in the landing configuration.

APPENDIX 2.—LIST OF TERMS USED IN THIS NPRM [For the reader’s reference and ease of reading, the following list defines terms that are used throughout this document. This appendix will not appear in the Code of Federal Regulations.]

Term Definition

Airfoil ...... The shape of the wing when looking at its profile. Airplane handling qualities ...... The response of the airplane to control inputs as assessed primarily by a pilot evaluating the ease of accomplishing maneuvering tasks. Airplane handling qualities refer to the stability, controllability, and maneuverability of the airplane. Airplane performance ...... The capability of the airplane in terms of speeds, distances, weights, flight paths, etc., expressed in terms of characteristics like takeoff and landing distances, en route altitude capability, climb and descent rates, flight paths, fuel burn, payload capability, range, etc. En route ice ...... The critical ice accretion appropriate to normal operation of the ice protection system during the en route phase of flight. Final takeoff ice ...... The most critical ice accretion appropriate to normal operation of the ice protection system during the final takeoff segment. Ice accretion is assumed to start at liftoff in the takeoff maximum icing conditions of 14 CFR part 25, appendix C, part 1, paragraph (c). Force reversal ...... A reversal in the direction of the force that the pilot needs to apply to perform a specified maneuver or achieve a specified load factor. For example, in a maneuver to reduce the load factor, a push force on the pitch control is initially needed to begin the maneuver, but changes to a pull force as the load factor is reduced. Holding ice ...... The critical ice accretion appropriate to normal operation of the ice protection system during the holding phase of flight. Hinge moment ...... The rotational force about the hinge of a control surface. Depending on the design of the airplane’s flight control system, large hinge moments can result in large forces at the pilot’s control, and hinge moment reversals can result in forces reversals. Ice-contaminated tailplane stall ...... Ice accretions on the tailplane leading to either completely stalled airflow over the horizontal sta- bilizer, or an elevator hinge moment reversal due to separated flow on the lower surface of the horizontal stabilizer. Landing ice ...... The critical ice accretion appropriate to normal operation of the ice protection system during the landing phase of flight. This is usually the same as holding ice. Load factor ...... The lift divided by the weight, expressed in units of gravity, or ‘‘g.’’ For example, in straight and level flight, the lift equals the weight and the load factor is 1 g. Pushover maneuver ...... A maneuver resulting from the pilot applying a push force to the airplane pitch control to pitch the airplane’s nose down. Sandpaper ice ...... A thin, rough layer of ice. Stall ...... Loss of lift caused by the airflow becoming detached from the upper surface of a lifting surface such as a wing or tailplane.

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APPENDIX 2.—LIST OF TERMS USED IN THIS NPRM—Continued [For the reader’s reference and ease of reading, the following list defines terms that are used throughout this document. This appendix will not appear in the Code of Federal Regulations.]

Term Definition

Takeoff ice ...... The critical ice accretion appropriate to normal operation of the ice protection system during the takeoff phase of flight, assuming accretion starts at liftoff in the takeoff maximum icing conditions of 14 CFR part 25, appendix C, part 1, paragraph (c). Tailplane ...... The horizontal wing attached to the tail assembly of the airplane.

Appendix 3: Relevant NTSB This safety recommendation resulted from their airplane provides adequate warning of Recommendations an accident on January 9, 1997, near Monroe, an impending stall in icing conditions. 8 If adopted, this rulemaking would respond Michigan. In that accident, the flightcrew Although we do not currently have a part to the following National Transportation were attempting a turning maneuver and did 25 regulatory requirement for stall warning to Safety Board (NTSB) Safety not know there was ice on the wing’s leading be provided by a warning device in the Recommendations. edge. With the degraded aerodynamics due to cockpit, general industry design practice is to 1. Safety Recommendation A–91–87. the ice on the wing’s leading edge, the use a device called a stick shaker to shake the ‘‘Amend the icing certification rules to airplane was at too low an airspeed to control column to warn the pilot of an require flight tests wherein ice is conduct the turning maneuver without impending stall. stalling. This caused a rapid descent after an accumulated in those cruise and approach XIV. Proposed Amendment flap configurations in which extensive uncommanded roll excursion, resulting in a exposure to icing conditions can be expected, crash. The airplane was destroyed and the 2 List of Subjects in 14 CFR Part 25: and require subsequent changes in flight crewmembers, 1 flight attendant, and configuration, to include landing flaps.’’ 26 passengers all died. The NTSB determined Aircraft, Aviation safety, Reporting [complete text available in the docket] that the probable cause of this accident was and recordkeeping requirements. This safety recommendation resulted from the FAA’s failure to establish adequate The Proposed Amendment an accident on December 26, 1989, at Pasco, aircraft certification standards for flight in Washington, where the airplane stalled due icing conditions, and to require the In consideration of the foregoing, the to ice-contamination on the tailplane.6 The establishment of adequate minimum airspeed Federal Aviation Administration radar data revealed that the airplane was in for icing conditions.9 proposes to amend part 25 of Title 14, the clouds in icing conditions for almost 91⁄2 As discussed in more detail later, this Code of Federal Regulations, as follows: minutes. The NTSB determined that the notice proposes to require applicants to probable cause of this accident was the demonstrate during type certification that PART 25—AIRWORTHINESS flightcrew’s decision to continue an their airplane has adequate maneuvering STANDARDS: TRANSPORT unstabilized ILS approach that led to a stall, capabilities in icing conditions. The CATEGORY AIRPLANES most likely of the horizontal stabilizer, and requirements added to part 25 by the 1-g stall loss of control at low altitude. Contributing rule 10 and the requirements proposed in this 1. The authority citation for part 25 to the stall and loss of control was the NPRM would ensure that the minimum continues to read as follows: accumulation of airframe ice that degraded operating speeds determined during the Authority: 49 U.S.C. 106(g), 40113, 44701, the aerodynamic performance of the certification of all future transport category 44702, and 44704 airplane.7 The airplane was destroyed and airplanes provide adequate maneuver the two pilots and all four passengers capability in both non-icing and icing 2. Amend § 25.21 by adding a new received fatal injuries. As discussed in more conditions. paragraph (g) to read as follows: detail later, this notice proposes to require 3. Safety Recommendation A–98–96. applicants to demonstrate during type ‘‘Require the manufacturers and operators of § 25.21 Proof of compliance. certification that their airplane is not all airplanes that are certificated to operate * * * * * susceptible to ice-contaminated tailplane in icing conditions to install stall warning/ (g) The requirements of this subpart stall. protection systems that provide a cockpit associated with icing conditions apply 2. Safety Recommendation A–98–94. warning (aural warning and/or stick shaker) only if certification for flight in icing ‘‘Require manufacturers of all turbine-engine before the onset of stall when the airplane is conditions is desired. If certification for driven airplanes (including the EMB–120) to operating in icing conditions.’’ [complete text flight in icing conditions is desired, the provide minimum maneuvering airspeed available on the NTSB Web site at: http:// information for all airplane configurations, ntsb.gov/Recs/letters/1998/A98_88_106.pdf] following requirements also apply: phases, and conditions of flight (icing and This safety recommendation resulted from (1) Each requirement of this subpart, non-icing conditions); minimum airspeeds the same accident discussed under Safety except §§ 25.121(a), 25.123(c), also should take into consideration the Recommendation A–98–94, above. The 25.143(b)(1) and (b)(2), 25.149, effects of various types, amounts, and airplane stalled before either the stall 25.201(c)(2), 25.207(c) and (d), 25.239, locations of ice accumulations, including warning system or the stall protection system and 25.251(b) through (e), must be met thin amounts of very rough ice, ice activated. As discussed in more detail later, in icing conditions. Compliance must be accumulated in supercooled large droplet this notice proposes to require applicants to shown using the ice accretions defined icing conditions, and tailplane icing.’’ demonstrate during type certification that in appendix C, assuming normal [complete text available on the NTSB Web operation of the airplane and its ice site at: http://ntsb.gov/Recs/letters/1998/ 8 _ _ Comair flight 3272, Empresa Brasileira de protection system in accordance with A98 88 106.pdf] Aeronautica, S/A (Embraer) EMB–120, operated by COMAIR Airlines, Inc. the operating limitations and operating 6 United Express flight 2415 (Sundance 415), a 9 National Transportation Safety Board, 1998. ‘‘In- procedures established by the applicant British Aerospace BA–3101 Jetstream, operated by Flight Icing Encounter and Uncontrolled Collision and provided in the Airplane Flight NPA Inc., (NPA is the name of the airline and is With Terrain, Comair Flight 3272, Embraer EMB– Manual. not an abbreviation). 120RT, N265CA, Monroe, Michigan, January 9, (2) No changes in the load 7 ‘‘Effect of Ice on Aircraft Handling 1997.’’ Aircraft Accident Report NTSB/AR–98/04. Characteristics (1984 Trials),’’ Jetstream 31—G– Washington, DC. distribution limits of § 25.23, the weight JSSD, British Aerospace Flight Test Report 10 Docket No. FAA–2002–13982, published in the limits of § 25.25 (except where limited FTR.177/JM, dated May 13, 1985. Federal Register (67 FR 70812, November 26, 2002). by performance requirements of this

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subpart), and the center of gravity limits 6. Amend § 25.111 by revising (i) The critical engine inoperative, the of § 25.27, from those for non-icing paragraph (c)(3)(iii), (c)(4), and adding a remaining engines at the takeoff power conditions, are allowed for flight in new paragraph (c)(5) to read as follows: or thrust available at the time the icing conditions or with ice accretion. landing gear is fully retracted, § 25.111 Takeoff path. 3. Amend § 25.103 by revising determined under § 25.111, unless there paragraph (b)(3) to read as follows: * * * * * is a more critical power operating (c) * * * condition existing later along the flight § 25.103 Stall speed. (3) * * * path but before the point where the (iii) 1.7 percent for four-engine * * * * * airplane reaches a height of 400 feet (b) * * * airplanes. (4) The airplane configuration may above the takeoff surface; and (3) The airplane in other respects (ii) The weight equal to the weight not be changed, except for gear (such as flaps, landing gear, and ice retraction and automatic propeller existing when the airplane’s landing accretions) in the condition existing in feathering, and no change in power or gear is fully retracted, determined under the test or performance standard in thrust that requires action by the pilot § 25.111. which VSR is being used; (2) The requirements of paragraph may be made until the airplane is 400 (b)(1) of this section must be met: * * * * * feet above the takeoff surface; and (i) In non-icing conditions; and 4. Amend § 25.105 by revising (5) If § 25.105(a)(2) requires the (ii) In icing conditions with the paragraph (a) to read as follows: takeoff path to be determined for flight takeoff ice accretion defined in in icing conditions, the airborne part of § 25.105 Takeoff. appendix C, if in the configuration of the takeoff must be based on the § 25.121(b) with the takeoff ice (a) The takeoff speeds prescribed by airplane drag: § 25.107, the accelerate-stop distance (i) With the takeoff ice accretion accretion: (A) The stall speed at maximum prescribed by § 25.109, the takeoff path defined in appendix C, from a height of takeoff weight exceeds that in non-icing prescribed by § 25.111, the takeoff 35 feet above the takeoff surface up to conditions by more than the greater of distance and takeoff run prescribed by the point where the airplane is 400 feet 3 knots CAS or 3 percent of V ; or § 25.113, and the net takeoff flight path above the takeoff surface; and SR prescribed by § 25.115, must be (ii) With the final takeoff ice accretion (B) The degradation of the gradient of determined in the selected configuration defined in appendix C, from the point climb determined in accordance with for takeoff at each weight, altitude, and where the airplane is 400 feet above the § 25.121(b) is greater than one-half of ambient temperature within the takeoff surface to the end of the takeoff the applicable actual-to-net takeoff flight operational limits selected by the path. path gradient reduction defined in applicant— § 25.115(b). * * * * * (c) Final takeoff. In the en route (1) In non-icing conditions; and 7. Revise § 25.119 to read as follows: (2) In icing conditions, if in the configuration at the end of the takeoff configuration of § 25.121(b) with the § 25.119 Landing climb: All-engines- path determined in accordance with takeoff ice accretion defined in operating. § 25.111: appendix C: In the landing configuration, the (1) The steady gradient of climb may (i) The stall speed at maximum takeoff steady gradient of climb may not be less not be less than 1.2 percent for two- weight exceeds that in non-icing than 3.2 percent, with the engines at the engine airplanes, 1.5 percent for three- conditions by more than the greater of power or thrust that is available 8 engine airplanes, and 1.7 percent for four-engine airplanes, at VFTO with— 3 knots CAS or 3 percent of VSR; or seconds after initiation of movement of (ii) The degradation of the gradient of the power or thrust controls from the (i) The critical engine inoperative and climb determined in accordance with minimum flight idle to the go-around the remaining engines at the available § 25.121(b) is greater than one-half of power or thrust setting— maximum continuous power or thrust; the applicable actual-to-net takeoff flight (a) In non-icing conditions, with a and (ii) The weight equal to the weight path gradient reduction defined in climb speed of VREF determined in § 25.115(b). accordance with § 25.125(b)(2)(i); and existing at the end of the takeoff path, (b) In icing conditions with the determined under § 25.111. * * * * * landing ice accretion defined in (2) The requirements of paragraph 5. Amend § 25.107 by revising appendix C, and with a climb speed of (c)(1) of this section must be met: paragraph (c)(3) and (g)(2) and adding V determined in accordance with (i) In non-icing conditions; and new paragraph (h) to read as follows: REF § 25.125(b)(2)(ii). (ii) In icing conditions with the final § 25.107 Takeoff speeds. 8. Amend § 25.121 by revising takeoff ice accretion defined in appendix C, if in the configuration of * * * * * paragraphs (b), (c), and (d) to read as follows: § 25.121(b) with the takeoff ice (c) * * * accretion: (3) A speed that provides the § 25.121 Climb: One-engine inoperative. (A) The stall speed at maximum maneuvering capability specified in * * * * * takeoff weight exceeds that in non-icing § 25.143(h). (b) Takeoff; landing gear retracted. In conditions by more than the greater of * * * * * the takeoff configuration existing at the 3 knots CAS or 3 percent of VSR; or (g) * * * point of the flight path at which the (B) The degradation of the gradient of (2) A speed that provides the landing gear is fully retracted, and in climb determined in accordance with maneuvering capability specified in the configuration used in § 25.111 but § 25.121(b) is greater than one-half of § 25.143(h). without ground effect: the applicable actual-to-net takeoff flight (h) In determining the takeoff speeds (1) The steady gradient of climb may path gradient reduction defined in V1, VR, and V2 for flight in icing not be less than 2.4 percent for two- § 25.115(b). conditions, the values of VMCG, VMC, engine airplanes, 2.7 percent for three- (d) Approach. In a configuration and VMU determined for non-icing engine airplanes, and 3.0 percent for corresponding to the normal all-engines- conditions may be used. four-engine airplanes, at V2 with: operating procedure in which VSR for

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this configuration does not exceed 110 (ii) The degradation of the gradient of determined on a level, smooth, dry, percent of the VSR for the related all- climb is greater than one-half of the hard-surfaced runway. In addition— engines-operating landing configuration: applicable actual-to-net flight path (1) The pressures on the wheel (1) The steady gradient of climb may reduction defined in paragraph (b) of braking systems may not exceed those not be less than 2.1 percent for two- this section. specified by the brake manufacturer; engine airplanes, 2.4 percent for three- * * * * * (2) The brakes may not be used so as engine airplanes, and 2.7 percent for 10. Revise § 25.125 to read as follows: to cause excessive wear of brakes or four-engine airplanes, with— tires; and (i) The critical engine inoperative, the § 25.125 Landing. (3) Means other than wheel brakes remaining engines at the go-around (a) The horizontal distance necessary may be used if that means— power or thrust setting; to land and to come to a complete stop (i) Is safe and reliable; (ii) The maximum landing weight; (or to a speed of approximately 3 knots (iii) A climb speed established in (ii) Is used so that consistent results for water landings) from a point 50 feet can be expected in service; and connection with normal landing above the landing surface must be procedures, but not exceeding 1.4 VSR; (iii) Is such that exceptional skill is determined (for standard temperatures, not required to control the airplane. and at each weight, altitude, and wind (d) For seaplanes and amphibians, the (iv) Landing gear retracted. within the operational limits established (2) The requirements of paragraph landing distance on water must be by the applicant for the airplane): determined on smooth water. (d)(1) of this section must be met: (1) In non-icing conditions; and (i) In non-icing conditions; and (e) For skiplanes, the landing distance (ii) In icing conditions with the (2) In icing conditions with the landing ice accretion defined in on snow must be determined on holding ice accretion defined in smooth, dry, snow. appendix C if VREF for icing conditions appendix C. The climb speed selected (f) The landing distance data must exceeds VREF for non-icing conditions for non-icing conditions may be used if include correction factors for not more the climb speed for icing conditions, by more than 5 knots CAS. (b) In determining the distance in (a): than 50 percent of the nominal wind computed in accordance with paragraph components along the landing path (d)(1)(iii) of this section, does not (1) The airplane must be in the landing configuration. opposite to the direction of landing, and exceed that for non-icing conditions by not less than 150 percent of the nominal more than the greater of 3 knots CAS or (2) A stabilized approach, with a calibrated airspeed of not less than wind components along the landing 3 percent. path in the direction of landing. 9. Amend § 25.123 by revising VREF, must be maintained down to the 50-foot height. (g) If any device is used that depends paragraphs (a) introductory text and (b) on the operation of any engine, and if to read as follows: (i) In non-icing conditions, VREF may not be less than: the landing distance would be § 25.123 En route flight paths. (A) 1.23 VSR0; noticeably increased when a landing is (a) For the en route configuration, the (B) VMCL established under made with that engine inoperative, the flight paths prescribed in paragraph (b) § 25.149(f); and landing distance must be determined and (c) of this section must be (C) A speed that provides the with that engine inoperative unless the determined at each weight, altitude, and maneuvering capability specified in use of compensating means will result ambient temperature, within the § 25.143(h). in a landing distance not more than that operating limits established for the (ii) In icing conditions, VREF may not with each engine operating. airplane. The variation of weight along be less than: 11. Amend § 25.143 by revising the flight path, accounting for the (A) The speed determined in paragraphs (c), (d), (e), (f), and (g), and progressive consumption of fuel and oil paragraph (b)(2)(i) of this section; by adding new paragraphs (h), (i), and by the operating engines, may be (B) 1.23 VSR0 with the landing ice (j) to read as follows: included in the computation. The flight accretion defined in appendix C if that § 25.143 General. paths must be determined at a speed not speed exceeds VREF for non-icing * * * * * less than VFTO, with— conditions by more than 5 knots CAS; and (c) The airplane must be shown to be * * * * * safely controllable and maneuverable (b) The one-engine-inoperative net (C) A speed that provides the with the critical ice accretion flight path data must represent the maneuvering capability specified in appropriate to the phase of flight actual climb performance diminished by § 25.143(h) with the landing ice defined in appendix C, and with the a gradient of climb of 1.1 percent for accretion defined in appendix C. critical engine inoperative and its two-engine airplanes, 1.4 percent for (3) Changes in configuration, power or propeller (if applicable) in the minimum three-engine airplanes, and 1.6 percent thrust, and speed, must be made in drag position:— for four-engine airplanes— accordance with the established (1) In non-icing conditions; and procedures for service operation. (1) At the minimum V2 for takeoff; (2) In icing conditions with the en (4) The landing must be made without (2) During an approach and go- route ice accretion defined in appendix excessive vertical acceleration, tendency around; and C, if: to bounce, nose over, ground loop, (3) During an approach and landing. (i) A speed of 1.18 VSR with the en porpoise, or water loop. (d) The following table prescribes, for route ice accretion exceeds the en route (5) The landings may not require conventional wheel type controls, the speed selected for non-icing conditions exceptional piloting skill or alertness. maximum control forces permitted by more than the greater of 3 knots CAS (c) For landplanes and amphibians, during the testing required by paragraph or 3 percent of VSR; or the landing distance on land must be (a) through (c) of this section:

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Force, in pounds, applied to the control wheel or rudder pedals Pitch Roll Yaw

For short term application for pitch and roll control—two hands available for control ...... 75 50 ...... For short term application for pitch and roll control—one hand available for control ...... 50 25 ...... For short term application for yaw control ...... 150 For long term application ...... 10 5 20

(e) Approved operating procedures or long term application that are inadvertently. Changes of gradient that conventional operating practices must prescribed in paragraph (d) this section, occur with changes of load factor must be followed when demonstrating the airplane must be in trim, or as near not cause undue difficulty maintaining compliance with the control force to being in trim as practical. control of the airplane, and local limitations for short term application (g) When maneuvering at a constant gradients must not be so low as to result that are prescribed in paragraph (d) of airspeed or Mach number (up VFC/MFC), in a danger of overcontrolling. this section. The airplane must be in the stick forces and the gradient of the trim, or as near to being in trim as stick versus maneuvering load factor (h) The maneuvering capabilities in a practical, in the preceding steady flight must lie within satisfactory limits. The constant speed coordinated turn at condition. For the takeoff condition, the stick forces must not be so great as to forward center of gravity, as specified in airplane must be trimmed according to make excessive demands on the pilot’s the following table, must be free of stall the approved operating procedures. strength when maneuvering the warning or other characteristics that (f) When demonstrating compliance airplane, and must not be so low that might interfere with normal with the control force limitations for the airplane can easily be overstressed maneuvering:

Maneuvering bank angle in Configuration Speed a coordinated Thrust/power setting turn

1 Takeoff ...... V2 ...... 30° Asymmetric WAT-limited. 2 3 Takeoff ...... V2 + XX ..... 40° All-engines-operating climb. 1 En route ...... VFTO ...... 40° Asymmetric WAT-limited. Landing ...... VREF ...... 40° Symmetric for ¥3° flight path angle. 1 A combination of weight, altitude, and temperature (WAT) such that the thrust or power setting produces the minimum climb gradient speci- fied in § 25.121 for the flight condition. 2 Airspeed approved for all-engines-operating initial climb. 3 That thrust or power setting which, in the event of failure of the critical engine and without any crew action to adjust the thrust or power of the remaining engines, would result in the thrust or power specified for the takeoff condition at V2, or any lesser thrust or power setting that is used for all-engines-operating initial climb procedures.

(i) When demonstrating compliance (2) For other means of activating the paragraphs (c) and (d) of this section. with § 25.143 in icing conditions— ice protection system, it must be Except for the stall warning prescribed (1) Controllability must be demonstrated in flight with the ice in paragraph (h)(2)(ii) of this section, the demonstrated with the ice accretion accretion defined in appendix C, part stall warning for flight in icing defined in appendix C that is most II(e) that: conditions prescribed in paragraph (e) critical for the particular flight phase; (i) The airplane is controllable in a of this section must be provided by the (2) It must be shown that a push force pull-up maneuver up to 1.5 g load same means as the stall warning for is required throughout a pushover factor; and flight in non-icing conditions. maneuver down to a zero g load factor, (ii) There is no longitudinal control (c) * * * or the lowest load factor obtainable if force reversal during a pushover limited by elevator power. It must be maneuver down to 0.5 g load factor. (d) * * * possible to promptly recover from the 12. Amend § 25.207 by revising (e) In icing conditions, the stall maneuver without exceeding 50 pounds paragraph (b), revising paragraphs (e) warning margin in straight and turning pull control force; and and (f), and adding paragraphs (g) and flight must be sufficient to allow the (3) Any changes in force that the pilot (h) to read as follows: pilot to prevent stalling (as defined in must apply to the pitch control to § 25.207 Stall warning. § 25.201(d)) when the pilot starts a maintain speed with increasing sideslip recovery maneuver not less than three angle must be steadily increasing with * * * * * (b) The warning must be furnished seconds after the onset of stall warning. no force reversals. When demonstrating compliance with (j) For flight in icing conditions before either through the inherent aerodynamic this paragraph, the pilot must perform the ice protection system has been qualities of the airplane or by a device the recovery maneuver in the same way activated and is performing its intended that will give clearly distinguishable as for the airplane in non-icing function, the following requirements indications under expected conditions conditions. Compliance with this apply: of flight. However, a visual stall warning (1) If activating the ice protection device that requires the attention of the requirement must be demonstrated in system depends on the pilot seeing a crew within the cockpit is not flight with the speed reduced at rates specified ice accretion on a reference acceptable by itself. If a warning device not exceeding one knot per second, surface (not just the first indication of is used, it must provide a warning in with— icing), the requirements of § 25.143 each of the airplane configurations (1) The en route ice accretion defined apply with the ice accretion defined in prescribed in paragraph (a) of this in appendix C for the en route appendix C, part II(e). section at the speed prescribed in configuration;

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(2) The holding ice accretion defined recovery maneuver earlier than one § 25.773 Pilot compartment view. in appendix C for the holding and second after the onset of stall warning. * * * * * approach configurations; (ii) If stall warning is provided by a (b) * * * (3) The landing ice accretion defined different means than for flight in non- (1) * * * in appendix C for the landing and go- icing conditions, the pilot may not start (i) * * * around configurations; and the recovery maneuver earlier than 3 (ii) The icing conditions specified in (4) The more critical of the takeoff ice seconds after the onset of stall warning. § 25.1419 if certification for flight in and final takeoff ice accretions defined Also, compliance must be shown with icing conditions is requested. in appendix C for each configuration § 25.203 using the demonstration * * * * * used in the takeoff phase of flight. prescribed by § 25.201, except that the 16. Amend § 25.941 by revising (f) The stall warning margin must be deceleration rates of § 25.201(c)(2) need paragraph (c) to read as follows: sufficient in both non-icing and icing not be demonstrated. conditions to allow the pilot to prevent 13. Amend § 25.237 by revising § 25.941 Inlet, engine, and exhaust stalling when the pilot starts a recovery paragraph (a) to read as follows: compatibility. * * * * * maneuver not less than one second after § 25.237 Wind velocities. the onset of stall warning in slow-down (c) In showing compliance with turns with at least 1.5 g load factor (a) For landplanes and amphibians, paragraph (b) of this section, the pilot normal to the flight path and airspeed the following applies: strength required may not exceed the deceleration rates of at least 2 knots per (1) A 90-degree cross component of limits set forth in § 25.143(d), subject to second. When demonstrating wind velocity, demonstrated to be safe the conditions set forth in paragraphs (e) compliance with this paragraph for for takeoff and landing, must be and (f) of § 25.143. icing conditions, the pilot must perform established for dry runways and must be 17. Amend § 25.1419 by revising the the recovery maneuver in the same way at least 20 knots or 0.2 VSRO, whichever introductory text to read as follows: as for the airplane in non-icing is greater, except that it need not exceed § 25.1419 Ice protection. conditions. Compliance with this 25 knots. (2) The crosswind component for requirement must be demonstrated in If certification for flight in icing takeoff established without ice flight with— conditions is desired, the airplane must accretions is valid in icing conditions. (1) The flaps and landing gear in any be able to safely operate in the (3) The landing crosswind component normal position; continuous maximum and intermittent must be established for: (2) The airplane trimmed for straight maximum icing conditions of appendix (i) Non-icing conditions, and C. To establish this— flight at a speed of 1.3 VSR; and (ii) Icing conditions with the landing * * * * * (3) The power or thrust necessary to ice accretion defined in appendix C. maintain level flight at 1.3 V . 18. Amend appendix C of part 25 by SR * * * * * (g) Stall warning must also be adding a new part I heading and a new 14. Amend § 25.253 by revising provided in each abnormal paragraph (c) to part I; and adding a new paragraph (b), and adding a new configuration of the high lift devices part II to read as follows: paragraph (c) to read as follows: that is likely to be used in flight Appendix C of Part 25 following system failures (including all § 25.253 High-speed characteristics. Part I—Atmospheric Icing Conditions configurations covered by Airplane * * * * * Flight Manual procedures). (b) Maximum speed for stability (a) * * * (h) For flight in icing conditions characteristics. VFC/MFC. VFC/MFC is the (c) Takeoff maximum icing. The before the ice protection system has maximum speed at which the maximum intensity of atmospheric icing been activated and is performing its requirements of §§ 25.143(g), 25.147(e), conditions for takeoff (takeoff maximum intended function, the following 25.175(b)(1), 25.177, and 25.181 must be icing) is defined by the cloud liquid requirements apply, with the ice met with flaps and landing gear water content of 0.35 g/m3, the mean accretion defined in appendix C, part retracted. Except as noted in § 25.253(c), effective diameter of the cloud droplets II(e): VFC/MFC may not be less than a speed of 20 microns, and the ambient air (1) If activating the ice protection midway between VMO/MMO and VDF/ temperature at ground level of minus 9 ¥ ° system depends on the pilot seeing a MDF, except that for altitudes where degrees Celsius ( 9 C). The takeoff specified ice accretion on a reference Mach number is the limiting factor, MFC maximum icing conditions extend from surface (not just the first indication of need not exceed the Mach number at ground level to a height of 1,500 feet icing), the requirements of this section which effective speed warning occurs. above the level of the takeoff surface. apply, except for paragraphs (c) and (d) (c) Maximum speed for stability of this section. Part II—Airframe Ice Accretions for characteristics in icing conditions. The Showing Compliance With Subpart B (2) For other means of activating the maximum speed for stability ice protection system, the stall warning characteristics with the ice accretions (a) Ice accretions—General. Section margin in straight and turning flight defined in appendix C, at which the 25.21(g) states that if certification for must be sufficient to allow the pilot to requirements of §§ 25.143(g), 25.147(e), flight in icing conditions is desired, the prevent stalling without encountering 25.175(b)(1), 25.177, and 25.181 must be applicable requirements of subpart B any adverse flight characteristics when met, is the lower of: must be met in the icing conditions of the speed is reduced at rates not (1) 300 knots CAS; appendix C. The most critical ice exceeding one knot per second and the (2) VFC; or accretion in terms of handling pilot performs the recovery maneuver in (3) A speed at which it is characteristics and performance for each the same way as for flight in non-icing demonstrated that the airframe will be flight phase must be determined, taking conditions. free of ice accretion due to the effects of into consideration the atmospheric (i) If stall warning is provided by the increased dynamic pressure. conditions of part I of this appendix, same means as for flight in non-icing 15. Amend § 25.773 by revising and the flight conditions (for example, conditions, the pilot may not start the paragraph (b)(1)(ii) to read as follows: configuration, speed, angle-of-attack,

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and altitude). The following ice (5) Landing ice is the critical ice frost, snow, or ice at the start of the accretions must be determined: accretion on the unprotected surfaces, takeoff; (1) Takeoff ice is the most critical ice and any ice accretion on the protected (2) The ice accretion starts at liftoff; accretion on unprotected surfaces, and surfaces appropriate to normal ice (3) The critical ratio of thrust/power- any ice accretion on the protected protection system operation following to-weight; surfaces appropriate to normal ice exit from the holding flight phase and (4) Failure of the critical engine protection system operation, occurring transition to the final landing occurs at VEF; and between liftoff and 400 feet above the configuration. (5) Crew activation of the ice takeoff surface, assuming accretion (6) Sandpaper ice is a thin, rough protection system is in accordance with starts at liftoff in the takeoff maximum layer of ice. a normal operating procedure provided icing conditions of part I, paragraph (c) (b) In order to reduce the number of in the Airplane Flight Manual, except of this appendix. ice accretions to be considered when that after beginning the takeoff roll, it (2) Final takeoff ice is the most demonstrating compliance with the must be assumed that the crew takes no critical ice accretion on unprotected requirements of § 25.21(g), any of the ice action to activate the ice protection surfaces, and any ice accretion on the accretions defined in paragraph (a) of system until the airplane is at least 400 protected surfaces appropriate to normal this section may be used for any other feet above the takeoff surface. ice protection system operation, flight phase if it is shown to be more (e) Ice accretion before the ice between 400 feet and 1,500 feet above conservative than the specific ice protection system has been activated the takeoff surface, assuming accretion accretion defined for that flight phase. and is performing its intended function. starts at liftoff in the takeoff maximum (c) The ice accretion that has the most The ice accretion before the ice icing conditions of part I, paragraph (c) adverse effect on handling protection system has been activated of this appendix. characteristics may be used for airplane and is performing its intended function is the ice accretion formed on the (3) En route ice is the critical ice performance tests provided any unprotected and normally protected accretion on the unprotected surfaces, difference in performance is surfaces before activation and effective and any ice accretion on the protected conservatively taken into account. operation of the ice protection system in surfaces appropriate to normal ice (d) Ice accretions for the takeoff continuous maximum atmospheric icing protection system operation, during the phase. For both unprotected and conditions. en route phase. protected parts, the ice accretion may be (4) Holding ice is the critical ice determined by calculation, assuming the Issued in Washington, DC, on October 24, accretion on the unprotected surfaces, takeoff maximum icing conditions 2005. and any ice accretion on the protected defined in appendix C, and assuming John J. Hickey, surfaces appropriate to normal ice that: Director, Aircraft Certification Service. protection system operation, during the (1) Airfoils, control surfaces and, if [FR Doc. 05–21793 Filed 11–3–05; 8:45 am] holding flight phase. applicable, propellers are free from BILLING CODE 4910–13–P

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