Vol. 79 Tuesday, No. 213 November 4, 2014
Part III
Department of Transportation
Federal Aviation Administration 14 CFR Parts 25 and 33 Airplane and Engine Certification Requirements in Supercooled Large Drop, Mixed Phase, and Ice Crystal Icing Conditions; Final Rule
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DEPARTMENT OF TRANSPORTATION and Policy Branch, ANE–111, Engine operation of those airplanes, and for and Propeller Directorate Standards other practices, methods, and Federal Aviation Administration Staff, Aircraft Certification Service, 12 procedures relating to those airplanes New England Executive Park, and engines. 14 CFR Parts 25 and 33 Burlington, MA 01803; telephone (781) Overview of Final Rule [Docket No. FAA–2010–0636; Amendment 238–7149; facsimile (781) 238–7199; Nos. 25–140 and 33–34] email [email protected]. The FAA is adopting this final rule to For part 25 legal questions contact revise certain regulations in Title 14, RIN 2120–AJ34 Douglas Anderson, FAA, Office of the Code of Federal Regulations (14 CFR) Regional Counsel, ANM–7, Northwest Airplane and Engine Certification part 25 (Airworthiness Standards: Mountain Region, 1601 Lind Avenue Requirements in Supercooled Large Transport Category Airplanes) and part SW., Renton, WA 98057–3356; Drop, Mixed Phase, and Ice Crystal 33 (Airworthiness Standards: Aircraft telephone (425) 227–2166; facsimile Icing Conditions Engines) related to the certification of (425) 227–1007; email transport category airplanes and turbine AGENCY: Federal Aviation [email protected]. airplane engines in icing conditions. We Administration (FAA), DOT. For part 33 legal questions contact are also creating the following new Vince Bennett, FAA, Office of the ACTION: Final rule. regulations: § 25.1324—Angle of attack Regional Counsel, ANE–007, New systems; § 25.1420—Supercooled Large SUMMARY: The Federal Aviation England Region, 12 New England Drop Icing Conditions; Appendix O to Administration is amending the Executive Park, Burlington, MA 01803; Part 25—Supercooled Large Drop Icing airworthiness standards applicable to telephone (781) 238–7044; facsimile Conditions; Appendix C to Part 33 (this certain transport category airplanes (781) 238–7055; email vincent.bennett@ is intentionally left blank as a certified for flight in icing conditions faa.gov. placeholder for potential future and the icing airworthiness standards SUPPLEMENTARY INFORMATION: rulemaking unrelated to icing); and applicable to certain aircraft engines. Authority for This Rulemaking Appendix D to Part 33 Mixed Phase and The regulations will improve safety by Ice Crystal Icing Envelope (Deep addressing supercooled large drop icing The FAA’s authority to issue rules on Convective Clouds). To improve the conditions for transport category aviation safety is found in Title 49 of the safety of transport category airplanes airplanes most affected by these icing United States Code. Subtitle I, Section operating in supercooled large drop conditions; mixed phase and ice crystal 106 describes the authority of the FAA (SLD), mixed phase, and ice crystal conditions for all transport category Administrator. Subtitle VII, Aviation icing conditions, these regulations will: Programs, describes in more detail the airplanes; and supercooled large drop, • Require airplanes most affected by mixed phase, and ice crystal icing scope of the agency’s authority. This rulemaking is under the SLD icing conditions to meet certain conditions for all turbojet, turbofan, and safety standards in an expanded turboprop engines. authority described in Subtitle VII, Part A, Subpart III, Section 44701, ‘‘General certification icing environment that DATES: Effective January 5, 2015. requirements.’’ Under that section, the includes freezing drizzle and freezing ADDRESSES: For information on where to FAA is charged with promoting safe rain. These safety standards include obtain copies of rulemaking documents flight of civil aircraft in air commerce by airplane performance and handling and other information related to this prescribing minimum standards qualities requirements. • final rule, see ‘‘How To Obtain required in the interest of safety for the Expand the engine and engine Additional Information’’ in the design and performance of aircraft; installation certification, and some SUPPLEMENTARY INFORMATION section of regulations and minimum standards in airplane component certification this document. the interest of safety for inspecting, regulations (for example, angle of attack FOR FURTHER INFORMATION CONTACT: For servicing, and overhauling aircraft; and and airspeed indicating systems) to part 25 technical questions contact regulations for other practices, methods, include freezing drizzle, freezing rain, Robert Hettman, FAA, Propulsion/ and procedures the Administrator finds mixed phase, and ice crystal icing Mechanical Systems Branch, ANM–112, necessary for safety in air commerce. conditions. Transport Airplane Directorate, Aircraft This regulation is within the scope of Summary of the Costs and Benefits of Certification Service, 1601 Lind Avenue that authority because it prescribes— the Final Rule SW., Renton, WA 98057–3356; • New safety standards for the design telephone (425) 227–2683; facsimile and performance of certain transport The benefits and costs are (425) 227–1320; email robert.hettman@ category airplanes and aircraft engines; summarized in the table below. As faa.gov. and shown in the table, the total estimated For part 33 technical questions • New safety requirements necessary benefits exceed the total estimated costs contact John Fisher, FAA, Rulemaking for the design, production, and for this final rule.
2012$ 7% Present value Benefit Cost Benefit Cost
Part 33 Engines ...... Qualitative ...... $13,936,000 Qualitative ...... $11,375,927 Large Part 25 Airplanes ...... $362,319,857 ... 14,126,333 $76,861,295 ..... $11,531,295 Other Part 25 Airplanes ...... $220,570,582 ... 33,198,788 $50,028,690 ..... $19,385,401
Total ...... $582,890,439 ... 61,261,121 $126,889,985 ... $42,292,624
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Background • Devise requirements to assess the and use of aircraft. Also, expand the Safety concerns about the adequacy of ability of an airplane to either safely appendix C icing certification envelope the icing certification standards were operate without restrictions in SLD and to include freezing drizzle/freezing rain brought to the forefront of public and mixed phase conditions or safely and mixed water/ice crystal conditions, governmental attention by a 1994 operate until it can exit these as necessary (A–96–54 supersedes A– accident in Roselawn, Indiana, conditions. 81–116 and –118). • Study the effects icing requirement involving an Avions de Transport 2. A–96–56 Re´gional (ATR) ATR 72 series airplane. changes could have on §§ 25.773, Pilot The National Transportation Safety compartment view; 25.1323, Airspeed Revise the icing certification testing Board (NTSB), with assistance from indicating system; and 25.1325, Static regulation to ensure that airplanes are pressure systems. properly tested for all conditions in ATR, the FAA, the French Direction • Ge´ne´ral de l’Aviation Civile, Bureau Consider the need for a regulation which they are authorized to operate, or D’Enquetes et D’Analyses, the National on ice protection for angle of attack are otherwise shown to be capable of Aeronautics and Space Administration probes. safe flight into such conditions. If safe (NASA), and others, conducted an The FAA ultimately determined that operations cannot be demonstrated by extensive investigation of this accident. the revised icing certification standards the manufacturer, operational This investigation determined that should include SLD, mixed phase, and limitations should be imposed to freezing drizzle-sized drops created a ice crystal icing conditions. This rule is prohibit flight in such conditions, and ridge of ice on the wing’s upper surface based on ARAC’s recommendations to flightcrews should be provided with the aft of the deicing boots and forward of the FAA. means to positively determine when the ailerons. The investigation further A. Related Actions they are in icing conditions that exceed concluded that this ridge of ice the limits for aircraft certification. ARAC’s IPHWG submitted additional contributed to an uncommanded roll of icing rulemaking recommendations to C. Summary of the Notice of Proposed the airplane. Based on these findings, the FAA that led to the Part 25 and Part Rulemaking the NTSB recommended changes to the 121 Activation of Ice Protection final The notice of proposed rulemaking icing certification requirements. 3 The atmospheric icing conditions for rules. For certain airplanes certificated (NPRM), Notice No. 10–10, published in certification are specified in part 25, for flight in icing, those rulemaking the Federal Register on June 29, 2010 appendix C. The atmospheric condition actions revise the certification and (75 FR 37311), is the basis for this final (freezing drizzle) that contributed to the operating rules for flight in icing rule. After receiving several requests to Roselawn accident is outside the icing conditions by requiring either extend the public comment period, the envelope currently used for certifying installation of ice detection equipment FAA extended the comment period by transport category airplanes. The term or changes to the airplane flight manual 30 days to September 29, 2010, with a ‘‘icing envelope’’ is used in part 25, (AFM) to ensure timely activation of the document published in the Federal appendix C, and in this rule to refer to airframe ice protection system. Register on August 16, 2010 (75 FR the environmental icing conditions Although those rulemaking actions 49865). within which the airplane must be address flight in icing conditions, they To improve the safety of transport shown to be able to safely operate. The do not directly impact this final rule. category airplanes operating in SLD, mixed phase, and ice crystal icing term ‘‘transport category airplanes’’ is B. NTSB Recommendations used throughout this rulemaking conditions, the FAA proposed new The NTSB issued NTSB Safety document to include all airplanes type- regulations in the NPRM to: Recommendation Numbers A–96–54 • certificated to part 25 regulations. Expand the certification icing Another atmospheric icing and A–96–56 as a result of the Roselawn environment to include freezing drizzle accident previously discussed. This and freezing rain environments. environment outside the current icing • envelope is freezing rain. The FAA has rulemaking partially addresses those Require airplanes most affected by not required airplane manufacturers to NTSB recommendations. The FAA is SLD icing conditions to meet certain show that airplanes can operate safely considering separate rulemaking safety standards in the expanded in a freezing drizzle or freezing rain activities associated with revisions to 14 certification icing environment, icing environment. CFR part 23 regulations for small including airplane performance and airplanes and 14 CFR part 121 handling qualities requirements. As a result of this accident and • consistent with related NTSB operational regulations to complete the Expand the engine and engine recommendations,1 the FAA tasked the FAA response to these NTSB installation certification regulations, Aviation Rulemaking Advisory recommendations. The NTSB and some airplane component Committee (ARAC),2 through its Ice recommendations are as follows: certification regulations (for example, angle of attack and airspeed indicating Protection Harmonization Working 1. A–96–54 Group (IPHWG), to do the following: systems), to include freezing rain • Define an icing environment that Revise the icing criteria published in environments, freezing drizzle includes SLD conditions. 14 CFR parts 23 and 25, in light of both environments, mixed phase, and ice • Consider the need to define a mixed recent research into aircraft ice crystal icing conditions. For certain phase icing environment (supercooled accretion under varying conditions of regulations, we proposed using a subset liquid and ice crystals). liquid water content (LWC), drop size of these icing conditions. distribution, and temperature, and D. General Overview of Comments 1 NTSB Safety Recommendations A–96–54 and recent developments in both the design A–96–56 are available in the rule Docket No. FAA– The FAA received comments from 31 2010–0636 and on the Internet at http:// 3 Part 25 Activation of Ice Protection, Docket No. commenters during the public comment www.ntsb.gov/doclib/recletters/1996/A96_48_ FAA–2007–27654, published in the Federal period: Five private citizens, the 69.pdf. Register on August 3, 2009 (74 FR 38328). Part 121 2 Published in the Federal Register on December Activation of Ice Protection, Docket No. FAA–2009– Aerospace Industries Association (AIA), 8, 1997 (62 FR 64621). http://www.gpo.gov/fdsys/ 0675, published in the Federal Register on August Airbus Industrie (Airbus), AirDat LLC, pkg/FR-1997-12-08/pdf/97-32034.pdf. 22, 2011 (76 FR 52241). the Airline Pilots Association (ALPA),
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American Kestrel Company, LLC, Discussion of Public Comments and finding of which icing conditions the (AKC), The Boeing Company, Final Rule airplane was in, unless on-board droplet size and LWC measurement means and Bombardier, Cessna, Dassault Aviation, Proposed Appendix O to Part 25 Embraer, Eurocopter, the European droplet data processing are provided. Aviation Safety Agency (EASA), Foster In the NPRM, the FAA proposed to Regarding the flight research project’s Technology, LLC, the General Aviation expand the existing icing conditions lack of on-board ability to document identified in appendix C of part 25 to Manufacturers Association (GAMA), GE aircraft performance degradation from include new SLD icing conditions Aviation, Gulfstream, Goodrich Sensors icing, we agree. However, obtaining defined in a new appendix O. The FAA measurements of aircraft performance and Integrated Systems (GSIS), made changes to appendix O as a result within icing conditions was the lowest Honeywell Engines, the National of comments received, but the general priority objective of the flight research Research Council (NRC), the NTSB, format remains unchanged. Appendix O project. The primary objectives of the Pratt & Whitney Canada, the Regional is structured like part 25, appendix C, test were to identify icing conditions Airline Association (RAA), the Swiss with part I defining icing conditions and beyond those covered in appendix C of Federal Office of Civil Aviation (FOCA), part II defining airframe ice accretions part 25, and to identify a method for Snecma, Transport Canada Civil for showing compliance with the presenting the data in a way that could Aviation (TCCA), and Turbomeca. Each airplane performance and handling be used as an engineering standard. commenter submitted multiple qualities requirements of part 25, Specific aircraft performance and comments. subpart B. handling degradations in icing Twelve commenters stated specific Three private citizens provided conditions are unique for each aircraft comments related to the flight data support for the rulemaking, recognized design. Performance degradation and collection approach used to acquire the efforts made by the ARAC working handling qualities criteria for appendix information about SLDs, the flight data group, and suggested specific changes C and appendix O icing encounters will used, and the analysis approach to need to be determined by the design intended to clarify the regulations or to generate the SLD engineering standards approval holder for each aircraft design clarify the intent. The NTSB and two in part 25, appendix O. We will address based on the applicable regulations, private citizens were disappointed that these three commenters as a group. guidance materials, and testing as the rulemaking took so long. One concern was with the methods necessary to demonstrate compliance. Fourteen commenters stated neither related to collecting and evaluating SLD This final rule specifies the expanded support nor opposition, but suggested icing conditions. One commenter stated environmental icing conditions for specific changes or identified areas for that the research aircraft were well consideration during the certification clarification. equipped to document the environment; process as well as the performance and however, both research aircraft had Two commenters, a rotorcraft handling qualities that must be serious deficiencies regarding their on- demonstrated. manufacturer and a rotorcraft engine board ability to document aircraft Regarding the sufficiency of the flight manufacturer, opposed the proposed performance degradation from icing. test data to form a statistically reliable changes to §§ 33.68 and 33.77. These Two commenters were concerned that database, we disagree. In developing commenters suggested the FAA make only the database jointly created by appendix O, we used all historically provisions to exclude rotorcraft from the Environment Canada and NASA was available flight research data on SLD, revised regulations. used to define the SLD icing conditions. not just the Environment Canada-NASA Two private citizens expressed Another commenter was concerned flight test data. This broad collection of concern for the data and methods used about the statistical significance of the data is statistically similar to the data to define the SLD conditions proposed data collected and did not think there that was used to develop appendix C. in part 25, appendix O. was enough flight test evidence Regarding the comments about our collected to provide the same level of proposed definition of SLD in appendix One commenter suggested that the probability established for part 25, O, we also disagree. The University of FAA should begin a certification appendix C, icing conditions. Two Wyoming data were included in the process toward use of a new commenters stated that the flight test FAA master database on SLD icing methodology for detecting ice over a campaign failed to relate their data conditions. However, these data were pitot inlet, for which the commenter has collection results to previously not used to support the final filed a provisional patent. published results, such as those determinations for the LWC values for The FAA received additional published by the University of the appendix O engineering standards. comments in a letter dated June 21, Wyoming. Specifically, the commenters The University of Wyoming aircraft was 2011, signed by four private citizens. noted that appendix O does not contain not equipped with two-dimensional The letter provided additional data for a LWC greater than 0.45 grams optical array probes, which were explanation for previously submitted per cubic meter. deemed essential by the IPHWG. comments. The FAA also considered One commenter also stated that other Without the probes, it was not possible this additional information while published analysis methods for an SLD to distinguish between cloud drops and drafting this final rule. encounter, such as the University of ice particles. Therefore, the University Wyoming LWC/drop size technique, of Wyoming cloud data were not The FAA made changes to the final result in the most adverse icing considered usable for supporting the rule in response to the public conditions and are not contained within analysis of SLD LWC/drop size comments. Summaries of the issues appendix O. The commenter also noted properties for appendix O. As a result, raised by the public comments and FAA that a clear distinction does not exist the Environment Canada-NASA responses, including explanations of between the icing conditions defined in database was used to determine the changes, are provided below. The full part 25, appendix C, and the conditions engineering standards because of the text of each commenter’s submission is defined in part 25, appendix O. This quality of the data contained therein available in the docket for this uncertainty would leave the pilot with and the analysis methods used in that rulemaking. the responsibility of making a scientific database. Both the quality of the data
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and the analysis method used by the the effect of greatly increasing power report DOT/FAA/AR–09/10.5 Figure 11 database ensured the accuracy of the requirements for electro-thermal deicing of that report shows a plot of definition for appendix O icing systems. Several commenters also temperature versus LWC for appendix O conditions. suggested that figures 1, 3, 4, and 6 of freezing drizzle environments that is Regarding the comment that the appendix O would be easier to use if the valid for the reference distance of 17.4 University of Wyoming LWC/drop size corner data points were defined in the nautical miles (32.2 km). Appendix C technique results in the most adverse figures. and appendix O define environmental icing conditions and are not contained We agree. We reviewed the figures conditions that overlap one another as within appendix O, we disagree. That proposed in the NPRM and the data the conditions transition from appendix analysis technique suggests that one used by the IPHWG to generate the C to appendix O. Therefore, there is not type of icing condition would be severe figures. We revised figures 1 and 4 to a clear mass distribution boundary that for all airplanes, regardless of the type reflect the lower water content values can be defined. of ice protection system used, or the proposed by the IPHWG, but the water One commenter, a private citizen, extent of the protection. Appendix O content in appendix O is still higher noted that the NPRM did not identify contains a variety of icing conditions, than within appendix C at the same the vertical extent for part 25, appendix not just those deemed most severe using temperature. The higher water content O, figure 6. We disagree. The pressure the University of Wyoming analysis may increase the power requirements altitude range and vertical extent for technique. for some electro-thermal deicing system freezing rain were provided in appendix In response to other comments, designs, but not to the extent that may O, part I, paragraph (b) in the NPRM figures 1 and 4 of appendix O have been have been necessary with the water located under figure 3. We clarified revised in this final rule to reflect the contents proposed in the NPRM. The appendix O, part I, by moving all of the LWC proposed by the IPHWG. As a environmental conditions defined in general text describing the result, freezing drizzle conditions with appendix O are valid conditions that meteorological parameters, including a median volume diameter (MVD) will need to be considered for vertical extent, ahead of the figures. greater than 40 microns fall within the applicable future designs. Our review of One commenter suggested that the adverse region that would be identified the data used to generate the scaling icing conditions in appendix O should using the University of Wyoming LWC/ factor curve in figure 7 indicates that the be revised to reflect water drop drop size technique. No changes to figure 7 proposed by the IPHWG in the distribution as a function of mean appendix O were made as a result of task 2 working group report was effective diameter (MED) as opposed to these comments. 4 With regard to the comment incorrect; figure 7 in the NPRM was MVD. We do not agree. MED is the term suggesting that the pilot will have to correct. Therefore, figure 7 in this final used in part 25, appendix C. make a scientific finding to determine rule remains as proposed in the NPRM. Examination of National Advisory which icing conditions the airplane is Figures 1, 3, 4, and 6 of appendix O in Committee for Aeronautics (NACA) 6 in, we disagree. For those types of this final rule have been revised to references shows that MED is the same airplanes most vulnerable to SLD icing identify the corner data points for as MVD if certain assumptions are made conditions, the level of operations in clarity. about the drop distribution, namely that SLD icing conditions for which the GSIS asked if there is a scientific basis it is one of the Langmuir distributions. airplane is approved will be determined for applying the horizontal extent of MVD, as the more general term, is during the airplane certification process 17.4 nautical miles. GSIS also noted that applicable to any drop distribution. in accordance with § 25.1420. If the same MVD, temperature, and LWC Since the drop distribution described in approval is requested for operations in at altitude exist in both appendix O and appendix O does not follow a Langmuir a portion of the icing conditions defined appendix C and asked the FAA to distribution, MVD is more appropriate. in appendix O, then the airplane clearly define the mass distribution We did not change the final rule or manufacturer will have to show that the boundary between appendix O and appendix O as a result of this comment. pilot can determine if the operational appendix C. A private citizen commented that envelope for which the airplane is Our application of the 17.4 nautical appendix O should define a time to use certified has been exceeded as required mile horizontal extent in appendix O for delayed recognition of entry into by § 25.1420(a)(2). Since part of the was made on a practical basis and not icing conditions and the time to exit certification will be evaluating the on a purely scientific basis; it was icing conditions. We do not agree. The means used to distinguish when the selected for consistency with the responsibility for proposing delayed airplane is in icing conditions outside appendix C continuous maximum icing recognition times, delayed ice the certified envelope, the pilot will not conditions with which designers are protection system activation times, or be faced with the ambiguity of trying to already familiar. We are unaware of any times required to exit icing conditions, determine the distribution of water scientific reasons for not applying the based on unique operational procedures drops in the environment in which he 17.4 nautical mile horizontal extent in or performance characteristics of the ice or she is flying. this manner. protection system, rests with the Several commenters said that The LWC values in appendix O are applicant. We did not change the rule proposed figures 1, 4, and 7 in appendix based on an analysis of the data from based on this comment. O of the NPRM were different than what the jointly created Environment Canada- Boeing suggested a change to was proposed by the IPHWG, and that NASA flight research SLD database, appendix O, part I, paragraph (c), to add the FAA did not provide an explanation an equation to determine the LWC for for those differences. The commenters 4 The data used to complete the IPHWG report is also noted that the higher LWC detailed in report DOT/FAA/AR–09/10, Data and 5 A copy of the report is in the rule Docket No. contained in the figures proposed in the Analysis for the Development of an Engineering FAA–2010–0636. NPRM could have a significant impact Standard for Supercooled Large Drop Conditions, 6 National Advisory Committee for Aeronautics dated March 2009. A copy of the report is available Technical Note 2738, A Probability Analysis of the on an applicant’s design. GSIS in the rule Docket No. FAA–2010–0636. The data Factors Conducive to Aircraft Icing in the United specifically noted that the higher water used for figure 7 are described on pages 34–39 of States, by William Lewis and Norman R. Bergrun, content defined in appendix O will have that report. July 1952.
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horizontal distances other than 17.4 paragraph (b)(2), and not just to the fashion that duplicates either the flight nautical miles. transit time through one appendix O or ground test environment. We agree that adding such an cloud and one appendix C cloud The NRC of Canada’s comments equation could be beneficial. The specified in paragraph (b)(2)(ii). reflected concerns about how the water equation proposed by Boeing, however, Embraer commented that it would be drop distribution curves in appendix O expressed horizontal distance in clearer to describe the total holding time are to be used. Further, a private citizen kilometers, which would be in a separate paragraph (b)(2)(iii) that commented that the droplet diameters inconsistent with other figures in says: ‘‘The total exposure to the icing for appendix O conditions can only be appendix O. Instead of the equation conditions need not exceed 45 reproduced in a few icing wind tunnels. proposed by Boeing, we added to minutes.’’ We agree, and changed We do not agree that available appendix O, part I, paragraph (c), a appendix O, part II, paragraph (b)(2), to engineering tools (icing wind tunnels similar equation that uses units of indicate that the total exposure time for and tankers, ice accretion prediction nautical miles. holding ice does not need to exceed 45 codes, and other analysis methods) are Several commenters noted that minutes. inadequate for showing compliance appendix O, part II, paragraph (b)(5)(ii), with the new rule. We recognize that the in the NPRM made reference to Availability of Engineering Tools To current engineering tools available to §§ 25.143(k) and 25.207(k). However, Show Compliance With the Rule show compliance with the new SLD §§ 25.143(k) and 25.207(k) do not exist Several commenters stated that rule have not been validated in every in the current part 25 and were not available engineering tools (icing wind aspect, and also have some limitations. added by the NPRM. tunnels and tankers, ice accretion We also recognize that for freezing rain, We agree. The references to those prediction codes, and other analysis few validated engineering tools are sections were inadvertently included in methods) are inadequate for showing available. However, methods are the NPRM. We revised appendix O to compliance with the new rule. available to simulate freezing drizzle. delete the statement referencing Bombardier commented that without Further, we recognize that relying upon §§ 25.143(k) and 25.207(k). validated tools, it is not practical to available simulation methods, combined Airbus noted that part II, paragraph implement the requirements proposed with engineering judgment, will be (c)(7)(v) of appendix O states that crew in the NPRM. Bombardier believed that required for finding compliance with activation of the ice protection system is efforts should be focused on the appendix O requirements of part 25, in accordance with a normal operating implementing incremental regulatory especially for freezing rain conditions. procedure provided in the AFM, except changes in parallel with the appropriate After reviewing the current state of that after beginning the takeoff roll, it technological developments to meet that available compliance methods and must be assumed that the crew does not regulatory change. engineering tools, the FAA has take any action to activate the ice Boeing commented similarly, stating determined that there is sufficient protection system until the airplane is at that the FAA and NASA had developed capability for applicants to effectively least 400 feet above the takeoff surface. a plan several years ago to align the demonstrate compliance with this final Airbus commented that this appears to timing of the new regulations with the rule. The IPHWG evaluated the current be a direct cut and paste from the availability of validated engineering capabilities of these tools in 2008–2009 appendix C regulations and tools and test capabilities for SLD during a review requested by industry recommended removing the sentence. conditions. Boeing added that the tools members through ARAC. The IPHWG Airbus claimed that while this is and test facilities necessary to evaluation of SLD engineering tools, perhaps understandable for appendix C effectively demonstrate compliance which proposed methods of compliance icing conditions, it would seem with the regulations are not available, based on the current state of the reasonable to expect the crew to activate and that this lack of availability will be available engineering tools, supports the the wing anti-ice system (WAIS) prior to particularly problematic for applicants FAA conclusion. The FAA considered takeoff if there are SLD icing conditions desiring to operate within appendix O estimates provided by industry and has within 400 feet of the runway, whether conditions. Boeing noted that the made adjustments to the proposed the AFM specifically states that it is current situation will require applicants economic evaluation, which is required or not. to either use highly conservative incorporated in the economic evaluation We do not agree. The rule addresses approaches, build new icing wind for this final rule. This adjustment flightcrew actions occurring after tunnel facilities, or expend great efforts increases the cost for complying with beginning the takeoff roll, while Airbus’ to conduct extensive flight testing in the requirements of this final rule; comment refers to actions that the search of a meteorological condition, however, this final rule remains cost flightcrew would take before beginning which occurs very infrequently. Boeing beneficial. A summary of the final the takeoff. Nevertheless, the FAA does said that this was not the approach regulatory evaluation is provided in the not expect flightcrews to be aware of all anticipated by industry, and that it will ‘‘Regulatory Notices and Analyses’’ SLD icing conditions that may exist up impose a severe burden on many section of this final rule and the to a height of 400 feet above the takeoff applicants beyond that established in complete document is included in the surface, nor do we agree that it would the economic evaluation of the public docket. be reasonable to expect the flightcrew to proposed regulation, without adding As to freezing drizzle, the current activate the WAIS prior to takeoff if any commensurate safety benefit. icing wind tunnel test capabilities for there was no procedure telling them to AKC also commented that current test SLD icing conditions have been do so. We did not change the rule based facilities are limited in their ability to demonstrated. However, we recognize on this comment. produce freezing drizzle, in particular that some limitations exist: Icing wind Embraer commented that the last drop distributions greater than 40 tunnel spray systems evaluated during sentence in appendix O, part II, microns MVD. The water drop the IPHWG’s review do not support bi- paragraph (b)(2)(ii), which proposed to distribution curves provided in modal mass distributions (mass ‘‘peaks’’ define the holding ice conditions in part appendix O are not produced by any for two different drop sizes) provided in 25, appendix O, part II, paragraph (b)(2), facility known to AKC, and there are no appendix O and do not produce realistic should be applicable to the whole of facilities that produce freezing rain in a freezing rain simulations for the
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majority of those conditions. NASA O. However, the IPHWG task 2 report technical justification used to exclude examined alternate spray methods to and the NPRM only addressed airplane airplanes with a MTOW of 60,000 simulate portions of a bi-modal spray accidents and incidents; it did not pounds or greater. Airbus, AIA, Boeing, using spray sequencing techniques to include rotorcraft. Eurocopter and and GAMA provided comments in approximate drop distributions found in Turbomeca proposed provisions to response to the NPRM to support the natural conditions (reference: American exclude rotorcraft from the new engine proposed applicability based on MTOW Institute of Aeronautics and requirements. The FAA did not receive because airplanes with a MTOW of Astronautics report AIAA 2005–76, any comments providing specific 60,000 pounds or greater have not Simulation of a Bimodal Large Droplet support for the proposed applicability to previously experienced accidents or Icing Cloud in the NASA Icing Research rotorcraft. incidents associated with flight in SLD. Tunnel 7). NASA demonstrated the We agree. The IPHWG did not review Embraer and Pratt & Whitney Canada water spray sequencing technique for an rotorcraft accidents or incidents in icing comments to the NPRM specifically airfoil with unprotected surfaces and conditions and did not propose noted support for AIA’s position. the results showed rougher ice accretion rulemaking associated with rotorcraft. textures than appendix C ice shapes. As a result, we revised the proposed A review of the IPHWG analysis Experience indicates that SLD icing § 33.68 to separate the icing indicates that airplanes with a MTOW conditions generally result in rougher requirements for turboshaft engines of 60,000 pounds or greater have not ice accretion textures. NASA has also used for rotorcraft from turbojet, experienced accidents or incidents developed preliminary scaling methods turbofan, and turboprop engines used associated with flight in SLD. The FAA for SLD test applications and has for airplanes. The icing requirements originally considered including all new developed large droplet algorithm pertaining to turboshaft engines are airplanes in the applicability for improvements to its ice accretion unchanged and require that turboshaft § 25.1420, regardless of MTOW; prediction code by adding SLD engines operate safely throughout the however, the projected costs of subroutines. Other ice accretion code icing conditions defined in part 29, extending the rule to include airplanes developers have incorporated SLD appendix C. Section 33.68 now requires with a MTOW of 60,000 pounds or capabilities in their respective that turbojet, turbofan, and turboprop greater exceeded the projected benefits computational tools. A number of icing engines not installed on rotorcraft due to the positive in-service history wind tunnel owners have tested SLD operate safely throughout the icing (i.e., lack of accidents) of these airplanes icing conditions in their facilities and conditions defined in part 25, appendix in SLD. C, the SLD conditions defined in part are capable of performing tests for at The commenters did not present any 25, appendix O, and the mixed phase least a portion of the appendix O new data or information that was not environments. and ice crystal conditions defined in discussed within the IPHWG, or Regarding flight testing, § 25.1420 part 33, appendix D. discussed within the NPRM. The requires that applicants provide analysis Applicability of Proposed § 25.1420 to establish that ice protection for the commenters that opposed limiting the various airplane components is In the NPRM, the FAA proposed to applicability of the rule suggested that adequate, taking into account the add a new § 25.1420. Proposed lift and control surface size, or wing various operational configurations. § 25.1420 would have required specific chord length, are important parameters Section 25.1420 also describes flight airplanes certified for flight in icing affecting sensitivity to a given ice testing in natural or simulated icing conditions to be capable of either: (1) accretion. They based their opposition conditions, as necessary, to support the Operating safely within the new SLD on airplane weight, in part, because the analysis. The IPHWG acknowledged the icing conditions defined in part 25, ratio of wing and control surface sizes difficulties in flight testing in natural appendix O; (2) operating safely in a to airplane weight varies between SLD, and agreed it would not be portion of the new appendix O airplane designs. specifically required under § 25.1420. conditions, with the capability to detect We agree that design features such as We concur, and have left flight testing when conditions beyond those used for control surface size and wing chord as an option in the regulation. Until the certification have been encountered, length are important parameters, which engineering tools become more mature, and then safely exit all icing conditions; can affect the sensitivity of a wing to the flight tests in natural appendix O icing or (3) have a means to detect when icing conditions described in part 25, conditions may be necessary to achieve appendix O icing conditions are appendix O. As proposed in the NPRM, certification for unrestricted flight in encountered, and be capable of safely in order to issue a rule with estimated appendix O conditions in accordance exiting all icing conditions. The FAA costs commensurate with the estimated with § 25.1420(a)(3). proposed to limit the applicability of benefits, the applicability of § 25.1420 is § 25.1420 to airplanes that have a limited based on airplane weight due to Proposed Revisions to § 33.68 Should maximum takeoff weight (MTOW) of the positive service histories of certified Not Apply to Engines Installed on less than 60,000 pounds, or airplanes airplanes. Rotorcraft equipped with reversible flight controls Eurocopter and Turbomeca noted the regardless of MTOW. If future designs for larger airplanes proposed part 33 changes would apply The applicability of § 25.1420 was contain novel or unusual design features to all turbine engines, including discussed within the IPHWG and that affect this successful in-service turboshaft engines intended for consensus could not be reached. A history, and those design features make installation in rotorcraft. The proposed discussion of this issue was provided in the airplane more susceptible to the revision to § 33.68 would require all the NPRM under the heading effects of flight in SLD icing conditions, turbine engines to be capable of ‘‘Differences from the ARAC the FAA can issue special conditions to operating in the extended icing Recommendations.’’ Bombardier, ALPA, provide adequate safety standards. The conditions defined in part 25, appendix EASA, Goodrich, Gulfstream, the NTSB, FAA issues special conditions in and the TCCA provided comments to accordance with § 21.16. No changes 7 A copy of this report is available in the rule the NPRM that supported the majority have been made to the applicability of Docket No. FAA–2010–0636. position of the IPHWG, questioning the § 25.1420 as a result of these comments.
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Clarification of Definitions 23 airplanes to the applicability, as that reports of dual engine flameouts in high Embraer noted that § 25.1420(b) uses is beyond the scope of this rulemaking. altitude icing conditions believed to the terms ‘‘simulated icing tests’’ and However, we chartered an Aviation include ice crystals. AIA, Airbus, ‘‘simulated ice shapes’’ in various Rulemaking Committee (ARC) to review Boeing, and GAMA supported the subparagraphs. Embraer suggested that the IPHWG’s rulemaking addition of mixed phase and ice crystal subparagraphs § 25.1420(b)(1) and (b)(2) recommendations for part 25 and to conditions, such as those defined in part use the phrase ‘‘artificial ice’’ as defined make similar recommendations for part 33, appendix D. Honeywell commented that the in Advisory Circular (AC) 25–28, 23. The ARC transmitted a report current lack of and/or immature state of Compliance of Transport Category detailing part 23 rulemaking engine test facilities to demonstrate Airplanes with Certification recommendations to the FAA in a letter compliance to part 33, appendix D, Requirements for Flight in Icing dated February 19, 2011, and provided could result in a significant increase in Conditions, instead of ‘‘simulated icing supplemental recommendations in a an applicant’s activities to show tests.’’ letter dated April 27, 2011. The ARC We do not agree. Section transmitted its recommendations for a compliance because of the additional 25.1420(b)(1) and (b)(2) describe test final task in early 2012. We are studying flight testing required to locate the ice crystal conditions. Honeywell also methods, not the resulting ice shapes. these recommendations and may pursue noted that flying in actual ice crystal The terminology ‘‘simulated icing tests’’ additional rulemaking for part 23 conditions would put the flightcrew at is used in § 25.1420 consistently with airplanes. considerable risk. Honeywell § 25.1419. We added definitions for We agree that severe icing conditions, recommended that appendix D be ‘‘Simulated Ice Shape’’ and ‘‘Simulated including SLD, can create dangerous removed until test facilities have Icing Test’’ to § 25.1420 that are flight conditions for both current and developed the capabilities to run tests consistent with previously issued future airplanes. However, we do not for ice crystal conditions. Honeywell guidance. agree that the part 25 and part 33 rule also suggested that the FAA make AIA, Boeing, and GAMA suggested a changes discussed in this amendment research funds available to facilities to clarification to the definition of should apply to existing airplanes. Such develop this capability. ‘‘reversible flight controls.’’ AIA and a retroactive application would, in We agree, in part. We agree that only GAMA suggested that the addition of effect, be changing the certification basis limited capability exists for testing servo tab inputs in the examples of operational airplanes to correct an engines in ice crystal conditions. We provides a more complete and accurate unsafe condition, something generally also agree that flightcrews unnecessarily description. done by airworthiness directive (AD). operating in icing conditions puts them We agree and have clarified the To address the unsafe condition, we at risk. We do not agree, however, that definition of ‘‘reversible flight controls’’ have already issued ADs to mandate appendix D should be removed until to include the example of servo tab procedures to activate the ice protection test facilities develop the capabilities to inputs. In addition, since the definition equipment at the first sign of ice run tests for ice crystal conditions, or of ‘‘reversible flight controls’’ is accretion, and to incorporate procedures that FAA make funds available for necessary to determine the applicability into the AFM so the flightcrew can research to develop these capabilities. of § 25.1420, we added the definition to identify when they are in severe icing Section 33.68(e) allows for certification § 25.1420. conditions that exceed certificated limitations, and safely exit. demonstration by test, analysis, or Applicability of Proposed Appendix O New airworthiness standards are not combination of the two. Consistent with Icing Conditions to Part 23 Airplanes intended to correct an unsafe condition; ARAC Engine Harmonization Working and Previously Certified Part 25 rather, they are intended to improve the Group (EHWG) recommendations, until Airplanes level of safety for new airplane designs. ice crystal tools and test techniques The NTSB and a private citizen In the context of SLD, we are have been developed and validated, the commented that the icing conditions considering operational rules to engine manufacturer may use a proposed in appendix O should be mandate certain elements of the comparative analysis to specific field applicable to part 23 airplanes because airworthiness standards adopted in this events. This analysis should show that they are the type of airplanes most rulemaking for previously certified the new engine cycle or design feature, affected by flight into icing conditions. airplanes. However, those requirements or both, would result in acceptable The NTSB also stated that the proposed are beyond the scope of this rulemaking engine operation when operating in the rule should be expanded beyond newly and require separate rulemaking action. ice crystal environment defined in certified airplanes to include all deice appendix D to part 33. This comparative boot-equipped airplanes currently in Applicability of Part 33, Appendix D, to analysis should also take into account service that are certified for flight in § 25.1093, Induction System Icing both suspected susceptible design icing conditions (reference NTSB Safety Protection, and § 33.68, Induction features, as well as mitigating design Recommendation A–07–16).8 The NTSB System Icing features. We did not change the rule pointed out SLD is an atmospheric The NTSB supported changes to based on this comment. condition that can create dangerous §§ 33.68 and 33.77, noting that since we GSIS suggested that provisions be flight conditions for both the current issued an icing-related AD for the made for a detect-and-exit strategy for fleet of aircraft and newly certified Beechjet 400A no additional reports of part 33, appendix D, conditions; similar aircraft. unsafe icing conditions on that airplane to what was proposed in the NPRM for Regarding the applicability of have been noted. The FAA infers that part 25, appendix O, conditions. proposed appendix O to part 23 the NTSB was referring to AD 2006–21– We disagree. We do not believe part 33, appendix D, conditions can be airplanes, we disagree with adding part 02.9 That AD was issued following detected with enough time to exit before 8 NTSB Safety Recommendation A–07–16 is 9 AD 2006–21–02, Docket No. FAA–2006–26004, damage occurs. Therefore, a detect-and- available in the rule Docket No. FAA–2010–0636 published in the Federal Register on October 10, and on the Internet at http://www.ntsb.gov/doclib/ 2006 (71 FR 29363), is applicable to Raytheon airplanes; and Raytheon (Mitsubishi) Model MU– recletters/2007/A07_12_17.pdf. (Beech) Model 400, 400A, and 400T series 300 airplanes.
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exit strategy for part 33, appendix D, loss. Although these nine events are of category airplanes. In addition, the conditions is inappropriate. As concern, the EHWG did not judge them engine requirements in §§ 33.68 and proposed in the NPRM, the mixed phase to be safety significant. 33.77 for operation in all icing and ice crystal icing conditions defined An additional 14 in-flight events were conditions still apply to engines in part 33, appendix D, have been added not clearly identifiable as SLD events installed on part 25 airplanes regardless to §§ 25.1093(b)(1) and 33.68(a). but were described as heavy icing below of the airplanes’ MTOW. The 22,000 feet and resulted in fan damage applicability of appendix O conditions Applicability of Proposed Appendix O and/or high vibrations. These events did in § 25.1093(b) as a function of airplane to § 25.1093, Induction System Icing not clearly fall within conditions weight is consistent with the revised Protection, and § 33.68, Induction defined in either appendix C or applicability of § 25.1420, which System Icing appendix O. However, the general establishes minimum airworthiness AIA, Airbus, Boeing, and GAMA description of the icing conditions and standards for detection and safe provided comments that there are no engine damage is consistent with operation in appendix O conditions. known events that support a safety reports of engine damage that occurred Airplanes that have been susceptible to concern due to engine induction system within the icing conditions defined in performance issues while operating in icing in SLD aloft. In particular, the appendix O, so those might have been SLD icing conditions have been smaller EHWG evaluated known icing-related SLD events. airplanes with a MTOW less than engine events since 1988 and found no After reviewing the data, the EHWG 60,000 pounds. events in SLD aloft. The EHWG credited clearly identified SLD as a threat for Section 25.1093(b) was revised to this result to the current rigorous engine damage during ground provide relief for larger airplanes compliance to part 25, appendix C, operations. Furthermore, the EHWG because of the successful in-service conditions for engines. The commenters could not rule out SLD as a potential in- history of existing larger airplane believe that the safety of these systems flight safety threat, and decided to designs and larger airplane engine inlet for flight in appendix O conditions has include it as part of its designs. As previously discussed, the already been proven by service history. recommendations to the FAA. As changes to the requirements in §§ 33.68 The commenters state that continuing to proposed in the NPRM, the part 25, and 33.77 are intended to improve the certify future systems to the appendix O, SLD icing conditions have level of safety for turbine engines used requirements for appendix C icing been added to § 33.68. Also, as proposed on all airplanes, including large conditions, in conjunction with in the NPRM, § 33.77 contains airplanes, while operating in SLD consideration of excellent service requirements to demonstrate engine conditions. If future designs for larger history of similar designs in appendix O capability to ingest the applicable airplanes contain novel or unusual conditions, should be acceptable minimum ice slab defined in Table 1 of design features that affect this assurance of the safety of future designs. § 33.77. The ice slab sizes defined in successful in-service history, and those The commenters suggested that Table 1 of § 33.77 are a function of the design features make the airplane more consideration of the icing conditions engine inlet diameter. Turbojet, susceptible to the effects of flight in SLD defined in appendix O be removed from turbofan, and turboprop engine icing conditions, the FAA can issue § 25.1093. manufacturers must demonstrate, in special conditions to provide adequate We agree that there are no known part, that the engine will continue to safety standards. events that support a safety concern due operate throughout its power range in Boeing, AIA, and GAMA also to engine induction system icing in SLD the icing conditions defined in part 25, provided comments on the results of an aloft. However, there have been reports appendix O, and following ingestion of SLD analysis, including the use of the of engine fan damage or high vibration an ice slab that is a function of the NASA Lewis Ice Accretion Program, while operating in SLD icing conditions. engine inlet diameter. The changes to commonly referred to as LEWICE. The The ARAC database on engine events the requirements in §§ 33.68 and 33.77 analysis yielded overly conservative contains 231 icing events reported by are intended to improve the level of accreted ice mass calculations resulting engine manufacturers from safety for turbojet, turbofan, and in large amounts of ice on the radome. approximately 1988 through 2003, and turboprop engines used on transport The results from this analysis indicated includes part 25, appendix C; part 25, category airplanes in icing conditions, to Boeing that radome ice shedding appendix O; and part 33, appendix D in part because of reports of engine would be a concern, and it would events. Although the intent of the event damage or high engine vibrations while require ice protection on the currently database was to focus on icing events operating in SLD conditions. unprotected radome surfaces to reduce outside of appendix C, there are several We agree large airplanes that have ice build-up to acceptable limits. The appendix C events included in this likely encountered appendix O weight increase for radome ice database. The event database does not conditions have had a successful in- protection equipment would result in include any accidents. service history with no clearly increased fuel burn and increased The EHWG identified 46 part 25, identifiable safety significant events. operational costs that were not included appendix O (SLD) events. All events After considering the comments in the IPHWG economic analysis. occurred on the ground and resulted in received, we revised § 25.1093(b), Boeing also stated that most large fan damage and/or high vibrations so a compared to what was proposed in the airplanes are operating without precise effect on the safety of these NPRM, so consideration of the icing restrictions today and are safely events was not discernible. conditions described in appendix O encountering SLD conditions. Additionally, the EHWG identified does not apply to airplanes with a Analytical methods used by Boeing to nine additional events that it thought MTOW equal to or greater than 60,000 determine SLD ice accretions on might have been related to operations in pounds. As proposed in the NPRM, the radomes show considerably higher ice SLD icing conditions: Four were in- applicability of the icing conditions mass accretions than either past flight and all nine were on tail mounted described in part 25, appendix C; part calculations or past experience has engine configurations. Again, the events 33, appendix D; and falling and blowing indicated for other icing conditions. resulted in fan damage and/or high snow remain applicable to all turbine These analyses were never presented to vibrations, with indeterminable power engine installations on transport the IPHWG and details were not
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included with Boeing’s comments to Section 25.773 does not require the one suspected SLD event 10 included in support the FAA’s evaluation of windshield to be completely free of ice the IPHWG list of applicable events, the Boeing’s methods. As previously in all icing conditions. Therefore, this NTSB Performance Group reported that discussed, we revised § 25.1093(b) requirement does not preclude using ice the flight data recorder derived drag compared to what was proposed in the accreting in certain locations on the increment was much higher than an NPRM. For the purposes of compliance windshield as an indication that the increment measured in flight test with with § 25.1093(b), the icing conditions airplane is in icing conditions beyond intercycle ice (by a factor of 2 near the defined in appendix O are not those in which it is approved to operate. time where the pilot lost control of the applicable to airplanes with a MTOW We did not change the rule based on airplane). The NTSB report does not equal to or greater than 60,000 pounds. these comments. speculate what caused the large drag To show compliance with § 25.1093(b), Applicability of Proposed Appendix O increment, but it could have been analysis may be used for the radome as to § 25.1323, Airspeed Indicating airframe SLD ice accretion, propeller a potential airframe ice source. For System, § 25.1324, Angle of Attack SLD ice accretion, or a combination of compliance with § 25.1093(b), System, and § 25.1325, Static Pressure both. In addition, appendix J in AC 20– applicants may use qualitative analysis Systems 73A, Aircraft Ice Protection, dated supported by similarity to a previous August 16, 2006, documents a flight test design with a successful service history AIA, Airbus, Boeing, and GAMA commented that there are no known encounter in which suspected SLD to show that ice accretions ingested into caused a severe performance penalty the engine from the new airplane design events that support an in-flight safety concern for angle of attack systems in due to propeller ice accretion. FAA will be less than the ice slab size research tests, documented in report presented in § 33.77 Table 1, ‘‘Minimum SLD aloft. They believe the safety of these component systems for flight in DOT/FAA/AR–06/60, Propeller Icing Ice Slab Dimensions Based on Engine Tunnel Test on a Full-Scale Turboprop Inlet Size.’’ appendix O conditions has already been proven by service history. The Engine,11 have duplicated the event Applicability of Proposed Appendix O commenters recommended the reference discussed in the AC, and showed that to § 25.773, Pilot Compartment View to appendix O be removed from the propeller ice accretion and resulting requirements in §§ 25.1323, 25.1324, propeller efficiency loss is greater in AIA, Airbus, Boeing, and GAMA and 25.1325. SLD compared to appendix C commented that there are no known We do not agree. If certification for conditions. events that support a safety concern due flight in icing is desired, part 25 to windshield icing in SLD aloft. The After further consideration, we have requires the airplane to be capable of revised § 25.929 to require a means to commenters state the safety of these safely operating in icing conditions. The systems for flight in appendix O prevent or remove hazardous ice airplane and its components are taken accumulations that could form in the conditions has been proven by service into account during flight in icing history. They believe that continuing to icing conditions defined in appendix C certification programs. For these and the portions of appendix O for certify future systems to the reasons, all icing conditions should be requirements for appendix C icing which the airplane is approved for considered. Sections 25.1323, 25.1324, flight. As compared to the NPRM, the conditions, in conjunction with and 25.1325 include considerations for consideration of excellent service phrase ‘‘defined in appendices C and O’’ the SLD icing environment defined in has been replaced with ‘‘defined in history of similar designs in appendix O part 25, appendix O. conditions, should be an acceptable appendix C and in the portions of assurance of the safety of future designs. Applicability of Proposed Appendix O appendix O of this part for which the One commenter, an individual, to § 25.929, Propeller Deicing airplane is approved for flight.’’ commented that § 25.773 should not be AIA and GAMA commented that A private citizen commented that the changed, as ice accretion on the there are no known events that support words ‘‘would jeopardize engine windshield is one of the few indications a safety concern with propeller icing in performance’’ in the last portion of used to recognize the condition. SLD. In particular, AIA and GAMA § 25.929(a) makes this requirement We do not agree. Section 25.773 is noted the EHWG evaluated all known specific to engine performance. The intended to ensure that a clear portion icing-related events since 1988 and commenter requested that the words be of the windshield is maintained in icing found no events in SLD aloft. The stricken from the regulation. The conditions, which enhances safety in commenters credit the current rigorous commenter did not provide justification icing conditions. For airplanes certified compliance using appendix C to substantiate his proposed change. to detect appendix O conditions, or a conditions for this result. The We do not agree. First, we did not portion of appendix O conditions, and commenters believe the safety of these propose a change to this portion of the required to exit all icing conditions systems for flight in appendix O rule. Second, we reviewed the wording when the icing conditions used for conditions has already been proven by presented by the IPHWG and agree with certification have been exceeded, the service history. They further believe that its intent and its phrasing. Its pilot must have a clear view out the continuing to certify future systems to applicability is broader than just an windshield; not only when the airplane the requirements for appendix C icing engine rule. We did not change the rule is in appendix O icing conditions, but conditions, in conjunction with based on this comment. also during the time it takes to detect consideration of excellent service and exit all icing conditions within history of similar designs in appendix O 10 NTSB Investigation No. DFCA01MA031, which the airplane is not approved to conditions, should be acceptable Embraer EMB–120 Zero Injury Incident Near West operate. For airplanes not certified with assurance for the safety of future Palm Beach, Florida on March 19, 2001, http:// the detect-and-exit strategy, appendix C designs. www.ntsb.gov. and appendix O conditions need to be We do not agree. Propeller icing is 11 FAA Data Report DOT/FAA/AR–06/60, typically not implicated in events Propeller Icing Tunnel Test on a Full-Scale considered for the entire time the Turboprop Engine, dated March 2010. A copy of airplane is in the applicable icing because ice accretion on the propeller is this report is available in the rule Docket No. FAA– conditions. usually not visible in flight. However, in 2010–0636.
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Engine and Engine Installation §§ 25.1093(b)(2) and 25.1521(c)(3) based A private citizen suggested a word Requirements on these comments, to reflect these change to our proposed wording of The RAA commented that current changes and recent developments with § 33.68(d). In the NPRM, we proposed to facilities lack the capability to test large EASA. change § 33.68(d) to state that the engine AIA, GAMA, and a private citizen turbofans at very cold temperatures, should be run at ground idle speed for commented that the MVD for high LWC and, while new sites may come on-line a minimum of 30 minutes in each of the in Table 2 of § 33.68 may be difficult to in the future, such facilities could not be icing conditions shown in Table 2. The achieve in practice due to icing facility constructed to comply with the commenter suggested replacing the constraints, and may result in repetitive proposed test conditions. The RAA also phrase ‘‘should be run’’ with ‘‘must equivalent level of safety (ELOS) pointed out that future airplanes would demonstrate the ability to acceptably findings. Expanding the upper limits of not be certified for operations below operate.’’ The commenter noted that use droplet size ranges will allow flexibility zero degrees Fahrenheit when ‘‘freezing of the word ‘‘should’’ is ambiguous and in test demonstrations. An upper limit contrary to existing § 33.68, which uses fog’’ is present, so it would create a of 30 microns for glaze ice conditions the word ‘‘must.’’ Furthermore, the restriction to what is currently (points 1 and 3 in Table 1) and 23 commenter suggested that eliminating considered a safe operating condition. microns for rime ice conditions (point 2 Airbus, AIA, Boeing, GAMA, GE, and in Table 1) can be accepted if the critical the word ‘‘run’’ would be more a private citizen suggested that the point analysis shows that the engine is consistent with the demonstration choice of ambient temperature for the tested to equivalent or greater severity. methods for snow, ice, and large drop ground freezing fog rime icing AIA, GAMA, and a private citizen glaze ice conditions (i.e., test, analysis, demonstration should be driven by also suggested changes to the drop or combination of both) shown in Table critical point analysis, as required by diameters in Table 1 of § 33.68, noting 2 of § 33.68. § 33.68(b)(1). This analysis could also be that practical application of the required We agree and have clarified used to show that a more critical point conditions dictates a wider acceptable §§ 25.1093(b)(2) and 33.68(d) to state does not exist at temperatures below the droplet diameter range, without that the engine must operate at ground Table 1, condition 2, test temperatures measurably impacting the severity of the idle speed in the specified icing in § 33.68. Airbus, AIA, Boeing, GAMA, intended engine test demonstration. conditions. GE, a private citizen, and RAA further We agree. Although the commenters suggested that the applicant should be did not provide any data to validate the Alternatives to Rulemaking permitted to use analysis to demonstrate suggested change in drop diameters, we safe operation of the engine at are aware of test facility limitations, and Several commenters said that temperatures below the required test concur that the upper tolerance of drop operational solutions have proven to be demonstration temperature. If safe size is limiting for some test facilities. extremely effective in managing weather operation is shown by this analysis, a As a result, the proposed ±3 micron related risks (e.g., thunderstorms and temperature limitation would not be droplet tolerance has been removed and windshear). They suggested that the required for the AFM. a range for the MVDs is specified FAA should have been, or should start, Airbus also suggested a further change instead. This will still provide an placing at least as much emphasis on to § 25.1093(b)(2) to ensure that the test adequate safety margin. Likewise, the advancing alternatives to rulemaking as is performed in accordance with aircraft upper drop size limit has also been it does on creating new certification procedures to provide adequate increased to represent current test requirements. ALPA encouraged conservatism. These procedures are facility capabilities while preserving an continuous research and development defined in collaboration with the engine adequate safety margin. Section 33.68, of technical systems that would manufacturer and may be defined on the Table 1, has been revised to reflect these automatically detect the presence of basis of engine certification or changes. hazardous ice, measure the rate of development test results. AIA and GAMA also suggested that accumulation, and then alert the crew as EASA and the FAA have recently the ground test conditions in Table 1, appropriate to take action in order to addressed cold ground fog conditions. condition (iii), of § 25.1093 and Table 2, avoid a potentially unsafe flight Specifically, the choice of ambient condition 4, of § 33.68(d) should have a condition. AirDat, LLC, commented that temperature for the ground freezing fog consistent range of droplet sizes based the FAA may have overlooked state-of- rime icing demonstration should be on the values from part 25, appendix O. the-art meteorological tools, including driven by critical point analysis (as We agree. We changed Table 2, airborne sensors, that are commercially required by § 33.68(b)(1)). We condition 4, in § 33.68 by removing the available today, fully deployed, and in determined this analysis may also be maximum drop diameter so it is operation. AIA, Airbus, Boeing, and used to show that at colder temperatures consistent with Table 1, condition (iii), GAMA commented that the IPHWG did below the Table 1, condition 2, test in § 25.1093. Table 2 in § 33.68 was also not thoroughly consider any alternatives temperatures in § 33.68, a more critical revised to correct the conversion of to new rulemaking because the tasking point does not exist. The analysis may degrees Centigrade to degrees statement did not include this option. also be used to demonstrate safe Fahrenheit. operation of the engine at temperatures A private citizen remarked that We agree in part. We agree that below the required test demonstration. including parenthetical examples in the careful operations and new technologies If an applicant does not show unlimited rule text of § 33.68(a)(3) was not helpful may often enhance safety. However, we cold temperature operation, then the and may be construed to be note that rulemaking is at the discretion minimum ambient temperature that was exclusionary of other pertinent, topical of the agency, and we have exercised demonstrated through test and analysis considerations. Furthermore, their our discretionary rulemaking authority should also be a limitation. Finally, the absence does not diminish the clarity or in this instance. This rule provides acceleration to takeoff power or thrust understanding of the requirement. additional safety for the flying public should be accomplished in accordance We agree. We removed the when icing conditions are encountered, with the procedures defined in the parenthetical examples from the and it will improve the level of safety AFM. As a result, we changed regulatory text in § 33.68. of future airplane designs.
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Applicability of Mixed Phase and Ice stream. Airbus mentioned that one test Foster Technology, LLC (Foster), is an Crystal Conditions to Airspeed facility has made significant engineering consulting firm that has Indicating Systems improvements in its capability to filed a provisional patent that includes We received several comments reproduce icing conditions but it is a methodology for detecting ice over a suggesting that the mixed phase and ice limited by the size of the test article it pitot inlet, providing a corrected crystal environment in part 33, can accommodate. However, no test airspeed, and removing ice deposits. appendix D, should be used instead of facilities are currently capable of Foster suggested that the FAA should the mixed phase and ice crystal reproducing the full range of icing certify its new methodology. conditions and flight conditions environment that was proposed in Table We agree that existing regulations 1 of § 25.1323. AIA, Airbus, Boeing, and required by part 33, appendix D. Considering the state of the art of the would allow certification of a new pitot GAMA stated the NPRM acknowledged probe with ice detection capability. new information is available to guide engineering tools, there is a need for an agreed means of compliance. However, we would certify a new pitot development of an ice crystal envelope probe as part of a product’s type design appropriate for evaluation of airspeed We agree that the mixed phase and ice crystal environment in part 33, to be approved for installation, not the indication systems. They also noted that methodology described by Foster. If proposed Table 1 of § 25.1323 does not appendix D, should be used instead of the mixed phase and ice crystal Foster seeks independent certification of reflect the current understanding of the a new pitot probe, we suggest Foster ice crystal environment, nor does it environment proposed in Table 1 of complete and submit an application for include known pitot icing events, which § 25.1323. Therefore, §§ 25.1323 and a supplemental type certificate, at are published in ‘‘Interim Report no. 2,’’ 25.1324 have been revised to add a which time we will evaluate the new Bureau D’Enquetes et D’Analyses pour requirement to prevent malfunctions in la securite d’aviation civile (BEA) F– the mixed phase and ice crystal probe. environment defined in part 33, GZCP.12 GSIS recommended that Table Heavy Rain Requirements for Airspeed 1 of § 25.1323, which defines a subset of appendix D. With regard to comments suggesting Indication and Angle of Attack Systems part 33, appendix D, conditions, should that testing at sea level atmospheric be removed. Instead, the rule should Airbus and EASA fully supported a conditions may not be a conservative require that airspeed indication systems new requirement to cover the heavy rain assumption, or that ice crystal must not malfunction in any of the conditions being considered in the concentrations at an exterior mounted conditions specified in appendix D. NPRM. Airbus commented that some probe could be higher than the free EASA stated that the proposed testing at high LWCs, such as those stream conditions, we agree. The environment in Table 1 of § 25.1323 proposed in the NPRM, would help to would not address known events of conditions defined in part 33, appendix D, are atmospheric conditions. These ensure that water drainage in rain airspeed indicating system conditions, especially at takeoff, is malfunctions. EASA also fully atmospheric conditions include parameters for total water content as a adequate. A private citizen commented supported including in part 25, the that the maximum freezing rain static proposed mixed phase and ice crystal function of temperature, altitude, and horizontal extent. We also agree that temperature under consideration would parameters in proposed part 33, be unlikely to result in ice accretion and appendix D. TCCA suggested that the altitude may be an important parameter. Altitude is a parameter identified in part is not in line with figure 4 of appendix FAA reconsider the icing conditions for O. AIA, Boeing, and GAMA commented the airspeed indicating system proposed 33, appendix D, and must be considered when developing the test conditions that the proposed expanded parameters, in the NPRM within Table 1 of the source of which was not provided, § 25.1323 and include the ¥60 °C and supporting analysis necessary to do not appear congruous with hard data conditions described in part 33, show compliance. We also agree that depending on from extensive icing research. GSIS appendix D, instead. Airbus supported the application of airplane size and the location of the commented that it wanted to appendix D icing conditions to pitot and probe, the ice water content at the probe understand how the specific values for pitot-static probes, but pointed out it is may be higher than the ice water LWC, horizontal extent, and mean necessary to develop an acceptable content values defined in part 33, droplet diameter were determined and means of compliance that takes into appendix D. Since part 33, appendix D, what the technical justifications are for account the capabilities of the existing describes atmospheric conditions, the these levels. potential for higher ice crystal engineering tools (for example, models We consider analysis of heavy rain concentrations at the probe location and icing tunnels) and provide guidance conditions as proposed in the NPRM to compared to the atmospheric on these new requirements. GSIS also concentrations defined in part 33, be necessary to substantiate that water commented that recent testing suggests appendix D, must be considered when drainage from the airspeed indication testing at sea level atmospheric developing the test conditions and and angle of attack systems is adequate. conditions may not be a conservative supporting analysis necessary to show If the water drainage is inadequate, then assumption for ice crystal testing. compliance. Installation effects could be the residual water may freeze as the NRC noted the requirements of pitot probes or angle of attack sensors § 25.1323 do not appear to take into evaluated with a combination of computational fluid dynamics codes are subjected to below freezing account the effects of displacing the free and icing tunnels. Devices mounted on temperatures as the airplane climbs stream ice water content around the smaller surfaces could be assessed in an following takeoff. The heavy rain fuselage of the airplane. If the probe is icing tunnel. However, if the device is conditions are not intended as an icing in a region affected by this, then the mounted on the fuselage and tunnel condition as described in the NPRM. concentration detected by the probe blockage effects would preclude a The heavy rain LWC is based on heavy would be higher than that of the free meaningful icing tunnel test, then codes rainfall data documented in MIL–STD– 210C, Military Standard: Climatic 12 that adequately predict the shadowing This report can be found on the BEA Web site Information to Determine Design and at http://www.bea.aero/docspa/2009/f- and concentration effects may be cp090601e2.en/pdf/f-cp090601e2.en.pdf. acceptable compliance methods. Test Requirements for Military Systems
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and Equipment.13 The same rain data on the airplane. As a result, failure to nautical miles. Based on these facts, was used for the AIA Propulsion provide proper pitot probe deicing may Airbus concluded that short cloud Committee Study, Project PC 338–1 not be detected. EASA suggested that a exposures are the most critical. documented in part 33, appendix B. new regulation be created to explicitly However, the new appendix D Heavy rain conditions have been added cover abnormal functioning of the definition implies that the longest to §§ 25.1323 and 25.1324. However, the heating system for externally mounted clouds are the most critical for engines conditions have been revised compared probes. and auxiliary power units (APUs), and to the conditions proposed in the NPRM We do not agree. If insufficient adds a factor of 2 to the conservatism of by removing temperature as a functioning of an externally mounted the definitions already defined in EASA parameter. probe creates an unsafe operating documents CS–E 780, Tests in Ice- condition, then warning information Forming Conditions, and AMC 25.1419, Applicability of the Icing Requirements must be provided to the flightcrew in Ice Protection.14 Airbus commented that in Part 25, Appendix O, and Part 33, accordance with § 25.1309(c). Since we it is inappropriate to add an additional Appendix D, to All Airspeed Indicating did not propose warning information factor of 2 to the icing conditions for Systems specific to failure modes for certain long exposures in appendix D icing EASA and TCCA suggested that externally mounted probes in the NPRM conditions considering the uncertainty §§ 25.1323 and 25.1324 be revised to and the public did not have the in the new rule. include the icing certification of all opportunity to comment, we consider We do not agree. We acknowledge external probes for flight instruments. the EASA proposal to be beyond the that a TAT sensor anomaly may be one EASA proposed a specific regulation scope of this rulemaking. No changes to indicator of ice crystals; however, it is including, but not limited to, pitot, the final rule have been made as a result not a very reliable indicator. The pitot-static, static, angle-of-attack, of EASA’s proposal. amount and concentration of ice crystals sideslip angle, and temperature sensors. required to create a TAT sensor anomaly Expand the Parameters for Part 33, The regulation proposed by EASA is not understood. Also, the TAT sensor Appendix D would require addressing the icing anomaly was only present in a portion conditions in part 25, appendix C; part AIA, Boeing, and GAMA commented of the engine events in the EHWG 25, appendix O; and part 33, appendix that part 33, appendix D, should be database. Therefore, the TAT anomaly D. Similarly, since total air temperature expanded to reflect new engine power data cannot accurately show cloud (TAT) is an input to calculating true loss and airspeed data loss events in ice extent. Additionally, detailed review of airspeed, Goodrich requested crystal conditions. Appendix D is based the event data indicated that once the clarification of whether or not TAT on a theoretical model, and Airbus TAT probe iced over enough to cause an sensors should be considered part of the agreed that the conditions in appendix indication anomaly, the engine often airspeed indicating system when D should be applied. would demonstrate a power upset very addressing ‘‘preventing malfunction’’ in We do not agree that appendix D soon after the TAT probe anomaly. This part 25, appendix O, and part 33, should be expanded in this final rule. period of time was insufficient for the appendix D, environments as described The majority of recent airspeed data pilot to take action since the ice in § 25.1323(i). anomalies occurred within the altitude accretion within the engine had already We do not agree with the commenters’ and temperature range described in part progressed to an advanced stage. suggestions to include icing 33, appendix D. We know of only one Therefore, we concluded that TAT requirements for all external probes and temporary loss of airspeed data event probe anomalies are poor precursor sensors in §§ 25.1323 and 25.1324. just outside or at the perimeter of the indications of the ice crystal threat to Section 25.1323(i) has traditionally altitude and temperature range in part engines, in terms of reliability of the applied to pitot probes (indicated 33, appendix D. Other conditions indication and the time period in airspeed), and the FAA did not propose described in appendix D, such as what advance of power loss. When a change to this applicability in the the ice water content actually was establishing the cloud extent factor in NPRM. As such, we did not intend to during the loss of airspeed data event, part 33, appendix D, the EHWG and include TAT sensors, or other externally are unknown because it was not FAA did take into account EASA CS–E– mounted instrument probes in measured. We agree that appendix D is 780 cloud definition requirements. § 25.1323(i). In addition, § 25.1324 was based on a theoretical atmospheric However, the EHWG was not able to proposed specifically for angle-of-attack model. We are continuing to support the validate the analysis used to develop the sensors. Revising §§ 25.1323 and research necessary to validate the part cloud extent factor in EASA CS–E–780. 25.1324 so that all externally mounted 33, appendix D, conditions with flight The cloud extent factor proposed by the flight instrument probes and sensors test data, and it would be premature to EHWG for part 33, appendix D, must operate in the various icing expand the appendix D environment at represents the most accurate cloud conditions is beyond the scope of this this time. Expansion of part 33, extent factor that can be established rulemaking. We did not change the rule appendix D, is out of scope of the using the available data. No changes in response to these comments. originally proposed rulemaking. We did were made as a result of these not change appendix D based on these Proposal To Add Indication System for comments. comments. External Probes Snecma commented that the y-axis Airbus commented that using the value in proposed part 33, appendix D, EASA advised that some failures of EHWG event database and referring to figure D3, was incorrect. The value the pitot probe heating resistance may the flight distance between a TAT should be 0.6 but the NPRM showed the not be seen by the flightcrew due to the sensor anomaly and the engine event, value as zero. low current detection system installed one can see that almost half of the We concur. We also found that both engine events occurred at a flight the x- and y-axis values proposed in the 13 A copy of MIL–STD–210C, dated January 9, distance equal to or less than 10 1987, is available in the rule Docket No. FAA– NPRM were incorrect. We changed part 2010–0636. MIL–STD–210 has since been nautical miles from the occurrence of superseded by MIL–HDBK–310, dated June 23, the TAT anomaly, with the majority of 14 Both of these documents are available on the 1997, which is also available in the rule docket. events happening within less than 4 EASA Web site at http://www.easa.europa.eu.
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33, appendix D, figure D3, to depict the We proposed to retain the provision better aligns the definition of the takeoff correct axis values. The lowest x-axis from Amendment 25–121 for not and final takeoff ice with that of the value is now 1 and the lowest y-axis requiring compliance with § 25.251(b) takeoff path used for determining value is now 0.6. through (e) in appendix C icing takeoff performance under §§ 25.111, Several commenters noted that the conditions and extend it to include 25.113, and 25.115. appendix O icing conditions. Although horizontal cloud length proposed in the Request To Revise § 25.629 NPRM was stated in statute miles, and Amendment 25–121 only addressed commented it should be provided in appendix C icing conditions, the TCCA commented that for airplanes nautical miles. The commenters conclusion that compliance to exempt from § 25.1420, no evaluation of suggested that changing to nautical § 25.251(b) through (e) need not be aeroelastic stability is required in miles would make the distance shown in icing conditions was based on appendix O icing conditions. For that measurement consistent with other a review of in-service experience in all reason, TCCA recommended that all tables and figures in appendix D. icing conditions, not just appendix C icing considerations be included We agree, and changed Table 1 to icing conditions. Therefore, including directly in § 25.629. We do not agree. Section 25.629(b)(1) identify that the horizontal cloud length § 25.251(b) through (e) within the requires aeroelastic stability evaluations is depicted in nautical miles. exceptions listed in § 25.21(g) for of the airplane in normal conditions. Several commenters asked why we certifications is equally applicable to either appendix C or appendix O For airplanes approved for operation in included the reference to ‘‘Reference 1’’ icing conditions, ice accumulations are in the text immediately following Table conditions. No changes were made to the final rule as a result of this considered a normal condition under 1 in proposed part 33, appendix D, the rule. Since § 25.629 does not especially considering the material comment. Dassault commented that the specifically distinguish between various constituting ‘‘Reference 1’’ was not types of icing conditions, all icing identified anywhere within the NPRM. proposed ice accretion definitions in part II of appendix O did not include an conditions for which the airplane is We agree. We removed the reference ice accretion specific to the flight phase approved are considered normal to ‘‘Reference 1’’ from the final rule. covered by § 25.121(a). Dassault added conditions. For airplanes exempt from Establishing New Operating Limitations that the ice accretion used for showing § 25.1420, or for which approval is not compliance with § 25.121(a)(1) should sought for flight in appendix O icing TCCA stated that it was not clear if be the accretion occurring between conditions, § 25.629(d)(3) requires that the proposed requirements to exit all liftoff and the point at which the ice accumulations due to inadvertent icing conditions were applicable only to landing gear is fully retracted. Dassault icing encounters must be considered for in-flight icing encounters, or if they requested that the FAA add the airplanes not approved for operation in were also applicable to the takeoff phase following definition: ‘‘Takeoff—landing icing conditions. The intent is to of flight. gear extended ice is the most critical ice consider ice accumulations due to We agree that clarification is needed. accretion on unprotected surfaces, and inadvertent icing encounters from any We changed § 25.1533(c) to clarify that any ice accretion on protected surfaces icing conditions for which the airplane the additional limitations apply to all appropriate to normal ice protection is not approved, including appendix O phases of flight. system operation, occurring between conditions. We did not change the rule Additional Requirements for Safe liftoff and the point at which the as a result of this comment. Operation landing gear is fully retracted, assuming Miscellaneous Issues accretion starts at liftoff in the icing AIA, Boeing, and GAMA commented conditions defined in Part I of this After the FAA issued the NPRM to that proposed appendix O, paragraph (b) appendix.’’ this rulemaking, we issued a final rule does not define takeoff ice accretions for Instead of adding a definition for the for Harmonization of Various airplanes not certified for takeoff in ice accretion during the initial takeoff Airworthiness Standards for Transport appendix O conditions. Therefore, they segment covered by § 25.121(a), we have Category Airplanes—Flight Rules suggested that § 25.207(e)(1), which reconsidered this issue and determined (docket number FAA–2010–0310). That defines stall warning requirements for that this flight segment does not last final rule revised § 25.21(g)(1) to add the takeoff with ice accretions, should be long enough for significant ice requirement that the stall warning added to the list of exceptions specified accretions to occur, even in appendix O margin requirements of § 25.207(c) and in § 25.21(g)(3). icing conditions. Therefore, we added (d) must be met in the landing We agree. We added the stall warning § 25.121(a) to the list of requirements in configuration in the icing conditions of requirements in § 25.207(e)(1) to the § 25.21(g)(4) that do not have to be met appendix C. That final rule also revised exceptions listed in § 25.21(g)(3). As a with appendix O ice accretions. We also § 25.253(c) to define the maximum result, applicants will not need to agree that our proposed definition for speeds at which the static lateral- determine the stall warning margin for takeoff ice was inadequate. We did not directional stability requirements of takeoff with appendix O ice accretions intend to require that applicants include § 25.177(a) through (c) and the for airplanes not certified to take off in the small effect (if any) of ice accretion directional and lateral control appendix O icing conditions. from the point of liftoff to the end of the requirements of § 25.147(f) must be met TCCA commented that exposure to takeoff distance in determining the in the icing conditions of appendix C. appendix O icing conditions may result takeoff distance under § 25.113, which We have retained those changes in in icing accretions further aft on the appendix C definition and the §§ 25.21(g)(2) and 25.253(c) of this final fuselage, wing and stabilizer surfaces, proposed appendix O definition may rule. For consistency, we also revised and control surfaces, beyond what have implied. Therefore, we revised the § 25.21(g)(4) to require that § 25.207(c) would normally be obtained in definitions of takeoff ice and final and (d) must be met in the landing appendix C conditions. Therefore, takeoff ice in part 25, appendix C and configuration in the appendix O icing TCCA suggested that compliance to appendix O, such that the ice accretion conditions for which certification is § 25.251(b) through (e) should be shown begins at the end of the takeoff distance, sought. This revision is a logical for appendix O conditions. not at the point of liftoff. This change outgrowth of the notice in this
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rulemaking because the purpose of successful in-service history, and those Regulatory Notices and Analyses § 25.21(g)(4) is to ensure safe operation design features make the airplane more Regulatory Evaluation in appendix O conditions during all susceptible to the effects of flight in SLD phases of flight, including the landing icing conditions, the FAA can issue Changes to Federal regulations must phase. special conditions to provide adequate undergo several economic analyses. The FAA finds that clarifying the safety standards. First, Executive Order 12866 and applicability of the proposed icing A private citizen identified potential Executive Order 13563 direct that each conditions to APU installations is flightcrew training issues associated Federal agency shall propose or adopt a necessary. Section 25.901(d) currently with this rulemaking. The commenter regulation only upon a reasoned requires that each auxiliary power unit noted that while practical test standards determination that the benefits of the installation must meet the applicable for post-stall recovery procedures are intended regulation justify its costs. provisions of the subpart. This clearly related to icing safety, they are Second, the Regulatory Flexibility Act requirement is unchanged by this not regulatory and may be changed of 1980 (Pub. L. 96–354) requires rulemaking. The FAA considers without formal notice. The commenter agencies to analyze the economic § 25.1093(b) to be applicable to APU also remarked that a common pilot impact of regulatory changes on small installations because they are turbine input characteristic to add power and entities. Third, the Trade Agreements engines. An essential APU is used to maintain the pitch angle of the airplane Act (Pub. L. 96–39) prohibits agencies provide air and/or power necessary to has been observed on the flight data from setting standards that create maintain safe airplane operation. A non- recorder time histories related to several unnecessary obstacles to the foreign essential APU is used to provide air icing related accidents. In some cases, commerce of the United States. In and/or power as a matter of convenience nose up pitch input was applied even developing U.S. standards, this Trade and may be shutdown without against the nose down force being Act requires agencies to consider jeopardizing safe airplane operation. applied by the airplane’s ‘‘stick pusher’’ international standards and, where The FAA has traditionally required that that is designed to rapidly reduce the appropriate, that they be the basis of essential APU installations continue to angle of attack. The commenter noted U.S. standards. Fourth, the Unfunded operate in part 25, appendix C, icing that these habit patterns are developed Mandates Reform Act of 1995 (Pub. L. conditions. Non-essential APU and reinforced as the required response 104–4) requires agencies to prepare a installations either have restricted in simulator training in accordance with written assessment of the costs, benefits, operation or are required to demonstrate FAA practical test standards for stall and other effects of proposed or final that operation in icing conditions does identification and recovery for rules that include a Federal mandate not affect the safe operation of the minimum altitude loss. For example, likely to result in the expenditure by airplane. References to part 25, ‘‘Minimum altitude loss’’ is trained as State, local, or tribal governments, in the appendix O, and part 33, appendix D, ‘‘zero altitude loss.’’ aggregate, or by the private sector, of have been added to § 25.1093(b). $100 million or more annually (adjusted As previously discussed, the The flightcrew training issues addressed by the commenter are for inflation with base year of 1995). applicability of appendix O conditions This portion of the preamble in § 25.1093(b) excludes all turbine important safety considerations. However, flightcrew training is beyond summarizes the FAA’s analysis of the engine installations that are used on economic impacts of this final rule. We airplanes with a MTOW equal to or the scope of this rulemaking because this rulemaking addresses design suggest readers seeking greater detail greater than 60,000 pounds. The FAA read the full regulatory evaluation, a still considers APUs to be turbine requirements. On July 6, 2010, the FAA published Safety Alert for Operators copy of which we have placed in the engines that must comply with the docket for this rulemaking. installation requirements in §§ 25.901 (SAFO) 10012. The SAFO discusses the possible misinterpretation of the In conducting these analyses, the FAA and 25.1093; therefore, this rulemaking has determined that this final rule: (1) is not creating separate requirements for practical test standards language ‘‘minimal loss of altitude.’’ 15 Has benefits that justify its costs, (2) is APU installations. Essential APU not an economically ‘‘significant In addition, on September 30, 2010, installations must continue to operate in regulatory action’’ as defined in section the FAA established the Stick Pusher the icing conditions applicable under 3(f) of Executive Order 12866, (3) is ‘‘not and Adverse Weather Event Training § 25.1093(b). Non-essential APU significant’’ as defined in DOT’s Aviation Rulemaking Committee. One of installations must not affect the safe Regulatory Policies and Procedures; (4) the rulemaking committee objectives is operation of the airplane when the icing will not have a significant economic to identify the best goals, procedures, conditions applicable under impact on a substantial number of small and training practices that will enable § 25.1093(b) are inadvertently entities; (5) will not create unnecessary air carrier pilots to accurately and encountered. obstacles to the foreign commerce of the Also as previously discussed, the consistently respond to unexpected United States; and (6) will not impose applicability of appendix O conditions stick pusher activations, icing an unfunded mandate on state, local, or in § 25.1093(b) was revised to provide conditions, and microburst and tribal governments, or on the private relief for larger airplanes because of the windshear events.16 The ARC has sector by exceeding the threshold successful in-service history of existing submitted recommendations to the identified above. These analyses are larger airplane and larger airplane FAA, which are being considered for summarized below. turbine engine inlet designs. If future additional rulemaking activities. Such APU installations contain novel or activities are beyond the scope of this Total Benefits and Costs of This Final unusual design features that affect this rulemaking. Rule
15 This document can be found at http:// 16 A copy of the charter is available at http:// www.faa.gov/other_visit/aviation_industry/airline_ www.faa.gov/about/office_org/headquarters_ operators/airline_safety/safo/all_safos/media/2010/ offices/avs/offices/afs/afs200/media/208_ARC_ SAFO10012.pdf. Charter.pdf.
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TABLE 1—TOTAL BENEFITS AND COSTS OF THIS RULE
2012$ 7% Present value Benefit Cost Benefit Cost
Part 33 Engines ...... Qualitative ...... $13,936,000 Qualitative ...... $11,375,927 Large Part 25 Airplanes ...... $362,319,857 ... 14,126,333 $76,861,295 ..... 11,531,295 Other Part 25 Airplanes ...... $220,570,582 ... 33,198,788 $50,028,650 ..... 19,385,401
Total ...... $582,890,439 ... 61,261,121 $126,889,985 ... 42,292,624 * Details may not add to row or column totals due to rounding.
Persons Potentially Affected by This Both Costs and Benefits are expressed Viewed from a breakeven analysis Final Rule in 2012 dollars. using only preventable fatalities, with each fatality valued at $9.1 million, this Part 25 airplane manufacturers, Benefits of This Final Rule rule has benefits exceeding costs with Engine manufacturers, and only 7 fatalities prevented. Operators of affected equipment. The FAA has analyzed events that would have been prevented if this final Costs of This Final Rule Assumptions rule were in place at the time of The total estimated costs are shown in certification. The events were evaluated The deliveries and affected fleets are Table 1. We obtained the basis of our for applicability and preventability in analyzed over appropriate time periods cost estimates from the industry. Since context with the requirements contained and are customized based upon actual the NPRM, we have modified the in this final rule. historical data. The fleet development is estimates based upon industry customized to the various (and For the categories of airplanes, first, comments and clarifications to those different) airplane types. We we develop casualty rates for fatalities, comments. The compliance costs are conservatively assume that all injuries, investigations, and destroyed analyzed in context of the part 25 and certifications will occur in 2015 and airplanes based on historical ice-related part 33 certification requirements. deliveries will occur in the following accidents. Next, we multiply the total As summarized in Table 2, the cost year. As production time spans differ by annual affected airplanes by the annual categories in the regulatory evaluation size of airplane, it is important for the risk per airplane. Lastly, we multiply incorporate both certification and reader to focus on present value benefits the casualty rates by the projected operational costs. We analyze each cost and costs. number of part 25 newly certificated category separately. The cost categories Present Value Discount rate—7% deliveries. When summed over time, the in this evaluation are the same as those Value of an Averted Fatality—$9.1 total estimated benefits are shown in provided by industry to comply with million in 2012 Table 1. the requirements contained in this rule.
TABLE 2—COST SUMMARY
Nominal cost 7% PV cost
Engine Certification Cost ...... $7,936,000 $6,478,140 Engine Capital Cost ...... 6,000,000 4,897,787
Total Engine Cost ...... 13,936,000 11,375,927
New Large Airplane Certification Cost ...... 14,126,333 11,531,295 Large Airplane Hardware Cost ...... 0 0 Large Airplane Fuel Cost ...... 0 0
Total Large Airplane Cost ...... 14,126,333 11,531,295
Other Airplane Certification Cost ...... 19,066,026 15,563,557 Other Airplane Hardware Cost ...... 2,475,000 1,312,609 Other Airplane Fuel Burn Cost ...... 11,657,762 2,509,236
Total Other Airplane Costs ...... 33,198,788 19,385,401
Total Costs ...... 61,261,121 42,292,624 * Details may not add to row or column totals due to rounding.
Alternatives Considered alternative, the proposed design Alternative 2—Limit the scope of requirements would extend to all applicability to small transport category Alternative 1—Make the entire rule applicable to all airplanes. transport category airplanes. This airplanes. alternative was rejected because this Not all the requirements in this rule Although this alternative would alternative would add significant costs extend to large transport category decrease the estimated cost, the FAA airplanes (those with a MTOW greater without a commensurate increase in believes that medium and large than 60,000 pounds). Under this benefits. airplanes are at risk of an SLD icing
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event. The FAA does not want a Raytheon Aircraft, and Sabreliner commerce of the United States. significant proportion of the future fleet Corporation. Because all U.S. transport- Pursuant to these Acts, the to be disproportionately at risk. category airplane manufacturers have establishment of standards is not more than 1,500 employees, none are considered an unnecessary obstacle to Regulatory Flexibility Determination considered small entities. the foreign commerce of the United The Regulatory Flexibility Act of 1980 United States aircraft engine States, so long as the standard has a (Pub. L. 96–354) (RFA) establishes as a manufacturers include General Electric, legitimate domestic objective, such as principle of regulatory issuance that CFM International, Pratt & Whitney, the protection of safety, and does not agencies shall endeavor, consistent with International Aero Engines, Rolls-Royce operate in a manner that excludes the objectives of the rule and of Corporation, Honeywell, and Williams imports that meet this objective. The applicable statutes, to fit regulatory and International. All but one exceeds the statute also requires consideration of informational requirements to the scale Small Business Administration small- international standards and, where of the businesses, organizations, and entity criteria for aircraft engine appropriate, that they be the basis for governmental jurisdictions subject to manufacturers. Williams International is U.S. standards. regulation. To achieve this principle, the only one of these manufacturers that The FAA has assessed the effect of agencies are required to solicit and is a U.S. small business. this final rule and determined that it consider flexible regulatory proposals The FAA estimated that Williams will not be an unnecessary obstacle to and to explain the rationale for their International engines power the foreign commerce of the United actions to assure that such proposals are approximately four percent of the States as the purpose of this rule is to given serious consideration. The RFA engines on active U.S. airplanes. ensure aviation safety. covers a wide-range of small entities, Assuming that future deliveries of including small businesses, not-for- newly certificated airplanes with Unfunded Mandates Assessment profit organizations, and small Williams International engines will Title II of the Unfunded Mandates governmental jurisdictions. have the same percentage as the active Reform Act of 1995 (Pub. L. 104–4) Agencies must perform a review to fleet, we calculated that this final rule requires each Federal agency to prepare determine whether a rule will have a will add about 0.2 percent of their a written statement assessing the effects significant economic impact on a annual revenue. We do not consider a of any Federal mandate in a proposed or substantial number of small entities. If cost of 0.2 percent of annual revenue final agency rule that may result in an the agency determines that it will, the significant. agency must prepare a regulatory expenditure of $100 million or more (in flexibility analysis as described in the Operators 1995 dollars) in any one year by State, RFA. In addition to the certification cost local, and tribal governments, in the However, if an agency determines that incurred by manufacturers, operators aggregate, or by the private sector; such a rule is not expected to have a will incur fuel costs due to the a mandate is deemed to be a ‘‘significant significant economic impact on a estimated additional impact of weight regulatory action.’’ The FAA currently substantial number of small entities, changes from equipment on affected uses an inflation-adjusted value of section 605(b) of the RFA provides that airplanes. On average, operators affected $143.1 million in lieu of $100 million. the head of the agency may so certify by the final rule will incur no additional This final rule does not contain such a and a regulatory flexibility analysis is annual fuel costs for newly certificated mandate; therefore, the requirements of not required. The certification must large part 25 airplanes, and $189, in Title II do not apply. include a statement providing the present value, in additional fuel costs Paperwork Reduction Act factual basis for this determination, and for other newly certificated part 25 the reasoning should be clear. Our airplanes. This final rule will apply to The Paperwork Reduction Act of 1995 initial determination was that the airplanes that have yet to be designed; (44 U.S.C. 3507(d)) requires that the proposed rule would not have a there will be no immediate cost to small FAA consider the impact of paperwork significant economic impact on a entities. The other airplane annual fuel and other information collection substantial number of small entities. We cost of $189, in present value, is not burdens imposed on the public. The received no public comments regarding significant in terms of total operating information collection requirements our initial determination. As such, this expenses. We do not consider these associated with this final rule have been final rule will not have a significant annual fuel costs a significant economic previously approved by the Office of economic impact on a substantial impact. Management and Budget (OMB) under number of small entities for the This final rule will not have a the provisions of the Paperwork following reasons. significant economic impact on a Reduction Act of 1995 (44 U.S.C. substantial number of airplane 3507(d)) and have been assigned OMB Airplane and Engine Manufacturers manufacturers, engine manufacturers, or Control Number 2120–0018. Airplane and engine manufacturers operators. Therefore, as the FAA International Compatibility and will be affected by the requirements Administrator, I certify that this rule Cooperation contained in this rule. will not have a significant economic For airplane manufacturers, we use impact on a substantial number of small (1) In keeping with U.S. obligations the size standards from the Small entities. under the Convention on International Business Administration for Air Civil Aviation, it is FAA policy to Transportation and Aircraft International Trade Analysis conform to International Civil Aviation Manufacturing specifying companies The Trade Agreements Act of 1979 Organization (ICAO) Standards and having less than 1,500 employees as (Pub. L. 96–39), as amended by the Recommended Practices to the small entities. The current United States Uruguay Round Agreements Act (Pub. maximum extent practicable. The FAA part 25 airplane manufacturers include L. 103–465), prohibits Federal agencies has reviewed the corresponding ICAO Boeing, Cessna Aircraft, Gulfstream from establishing standards or engaging Standards and Recommended Practices Aerospace, Learjet (owned by in related activities that create and has identified no differences with Bombardier), Lockheed Martin, unnecessary obstacles to the foreign these regulations.
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(2) Executive Order 13609, Promoting Executive Order 13211, Regulations List of Subjects International Regulatory Cooperation, That Significantly Affect Energy Supply, 14 CFR Part 25 promotes international regulatory Distribution, or Use Aircraft, Aviation safety, Reporting cooperation to meet shared challenges The FAA analyzed this final rule involving health, safety, labor, security, and recordkeeping requirements, Safety, under Executive Order 13211, Actions Transportation. environmental, and other issues and to Concerning Regulations that reduce, eliminate, or prevent Significantly Affect Energy Supply, 14 CFR Part 33 unnecessary differences in regulatory Distribution, or Use (May 18, 2001). The Aircraft, Aviation safety. requirements. The FAA has analyzed agency has determined that it is not a this action under the policies and ‘‘significant energy action’’ under the The Amendment agency responsibilities of Executive executive order and it is not likely to In consideration of the foregoing, the Order 13609, and has determined that have a significant adverse effect on the Federal Aviation Administration this action will have no effect on supply, distribution, or use of energy. amends chapter I of title 14, Code of international regulatory cooperation. Federal Regulations as follows: How To Obtain Additional Information Environmental Analysis Rulemaking Documents PART 25—AIRWORTHINESS STANDARDS: TRANSPORT FAA Order 1050.1E identifies FAA An electronic copy of a rulemaking CATEGORY AIRPLANES actions that are categorically excluded document may be obtained by using the from preparation of an environmental Internet— ■ 1. The authority citation for part 25 assessment or environmental impact 1. Search the Federal eRulemaking continues to read as follows: statement under the National Portal (http://www.regulations.gov); Authority: 49 U.S.C. 106(g), 40113, 44701, Environmental Policy Act in the 2. Visit the FAA’s Regulations and 44702 and 44704. absence of extraordinary circumstances. Policies Web page at http:// ■ 2. Amend § 25.21 by revising The FAA has determined this www.faa.gov/regulations_policies/ or paragraphs (g)(1) and (2) and adding rulemaking action qualifies for the 3. Access the Government Printing paragraphs (g)(3) and (4) to read as categorical exclusion identified in Office’s Web page at http:// follows: paragraph 4(j) and involves no www.gpo.gov/fdsys/browse/ extraordinary circumstances. collection.action?collectionCode=FR. § 25.21 Proof of compliance. Copies may also be obtained by Regulations Affecting Intrastate * * * * * sending a request (identified by notice, (g) * * * Aviation in Alaska amendment, or docket number of this (1) Paragraphs (g)(3) and (4) of this Section 1205 of the FAA rulemaking) to the Federal Aviation section apply only to airplanes with one Reauthorization Act of 1996 (110 Stat. Administration, Office of Rulemaking, or both of the following attributes: 3213) requires the FAA, when ARM–1, 800 Independence Avenue (i) Maximum takeoff gross weight is SW., Washington, DC 20591, or by modifying its regulations in a manner less than 60,000 lbs; or calling (202) 267–9680. (ii) The airplane is equipped with affecting intrastate aviation in Alaska, to reversible flight controls. Comments Submitted to the Docket consider the extent to which Alaska is (2) Each requirement of this subpart, not served by transportation modes Comments received may be viewed by except §§ 25.121(a), 25.123(c), other than aviation, and to establish going to http://www.regulations.gov and 25.143(b)(1) and (2), 25.149, appropriate regulatory distinctions. In following the online instructions to 25.201(c)(2), 25.239, and 25.251(b) the NPRM, the FAA requested search the docket number for this through (e), must be met in the icing comments on whether the proposed rule action. Anyone is able to search the conditions specified in Appendix C of should apply differently to intrastate electronic form of all comments this part. Section 25.207(c) and (d) must operations in Alaska. The agency did received into any of the FAA’s dockets be met in the landing configuration in not receive any comments, and has by the name of the individual the icing conditions specified in determined, based on the administrative submitting the comment (or signing the Appendix C, but need not be met for record of this rulemaking, that there is comment, if submitted on behalf of an other configurations. Compliance must no need to make any regulatory association, business, labor union, etc.). be shown using the ice accretions distinctions applicable to intrastate defined in part II of Appendix C of this Small Business Regulatory Enforcement part, assuming normal operation of the aviation in Alaska. Fairness Act airplane and its ice protection system in Executive Order Determinations The Small Business Regulatory accordance with the operating Executive Order 13132, Federalism Enforcement Fairness Act (SBREFA) of limitations and operating procedures 1996 requires FAA to comply with established by the applicant and The FAA has analyzed this final rule small entity requests for information or provided in the airplane flight manual. under the principles and criteria of advice about compliance with statutes (3) If the applicant does not seek Executive Order 13132, Federalism. The and regulations within its jurisdiction. certification for flight in all icing agency determined that this action will A small entity with questions regarding conditions defined in Appendix O of not have a substantial direct effect on this document, may contact its local this part, each requirement of this the States, or the relationship between FAA official, or the person listed under subpart, except §§ 25.105, 25.107, the Federal Government and the States, the FOR FURTHER INFORMATION CONTACT 25.109, 25.111, 25.113, 25.115, 25.121, or on the distribution of power and heading at the beginning of the 25.123, 25.143(b)(1), (b)(2), and (c)(1), responsibilities among the various preamble. To find out more about 25.149, 25.201(c)(2), 25.207(c), (d), and SBREFA on the Internet, visit http:// (e)(1), 25.239, and 25.251(b) through (e), levels of government, and, therefore, _ does not have Federalism implications. www.faa.gov/regulations policies/ must be met in the Appendix O icing rulemaking/sbre_act/. conditions for which certification is not
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sought in order to allow a safe exit from § 25.21(g), from the point where the defined in Appendices C and O of this those conditions. Compliance must be airplane is 400 feet above the takeoff part, as applicable, in accordance with shown using the ice accretions defined surface to the end of the takeoff path. § 25.21(g), if: in part II, paragraphs (b) and (d) of * * * * * * * * * * Appendix O, assuming normal ■ 5. Amend § 25.119 by revising ■ 8. Amend § 25.125 by revising operation of the airplane and its ice paragraph (b) to read as follows: paragraphs (a)(2), (b)(2)(ii)(B), and protection system in accordance with (b)(2)(ii)(C) to read as follows: the operating limitations and operating § 25.119 Landing climb: All-engines- procedures established by the applicant operating. § 25.125 Landing. and provided in the airplane flight * * * * * (a) * * * manual. (b) In icing conditions with the most (2) In icing conditions with the most (4) If the applicant seeks certification critical of the landing ice accretion(s) critical of the landing ice accretion(s) for flight in any portion of the icing defined in Appendices C and O of this defined in Appendices C and O of this conditions of Appendix O of this part, part, as applicable, in accordance with part, as applicable, in accordance with each requirement of this subpart, except § 25.21(g), and with a climb speed of § 25.21(g), if VREF for icing conditions §§ 25.121(a), 25.123(c), 25.143(b)(1) and VREF determined in accordance with exceeds VREF for non-icing conditions (2), 25.149, 25.201(c)(2), 25.239, and § 25.125(b)(2)(ii). by more than 5 knots CAS at the 25.251(b) through (e), must be met in ■ 6. Amend § 25.121 by revising maximum landing weight. the Appendix O icing conditions for paragraphs (b)(2)(ii) introductory text, (b) * * * which certification is sought. Section (c)(2)(ii) introductory text, and (d)(2)(ii) (2) * * * 25.207(c) and (d) must be met in the to read as follows: (ii) * * * landing configuration in the Appendix (B) 1.23 VSR0 with the most critical of O icing conditions for which § 25.121 Climb: One-engine-inoperative. the landing ice accretion(s) defined in certification is sought, but need not be * * * * * Appendices C and O of this part, as met for other configurations. (b) * * * applicable, in accordance with Compliance must be shown using the (2) * * * § 25.21(g), if that speed exceeds VREF ice accretions defined in part II, (ii) In icing conditions with the most selected for non-icing conditions by paragraphs (c) and (d) of Appendix O, critical of the takeoff ice accretion(s) more than 5 knots CAS; and assuming normal operation of the defined in Appendices C and O of this (C) A speed that provides the airplane and its ice protection system in part, as applicable, in accordance with maneuvering capability specified in accordance with the operating § 25.21(g), if in the configuration used to § 25.143(h) with the most critical of the limitations and operating procedures show compliance with § 25.121(b) with landing ice accretion(s) defined in established by the applicant and this takeoff ice accretion: Appendices C and O of this part, as provided in the airplane flight manual. * * * * * applicable, in accordance with (c) * * * ■ 3. Amend § 25.105 by revising § 25.21(g). (2) * * * * * * * * paragraph (a)(2) introductory text to (ii) In icing conditions with the most ■ read as follows: critical of the final takeoff ice 9. Amend § 25.143 by revising paragraphs (c) introductory text, (i)(1), § 25.105 Takeoff. accretion(s) defined in Appendices C and O of this part, as applicable, in and (j) introductory text to read as (a) * * * accordance with § 25.21(g), if in the follows: (2) In icing conditions, if in the configuration used to show compliance configuration used to show compliance § 25.143 General. with § 25.121(b) with the takeoff ice with § 25.121(b), and with the most * * * * * accretion used to show compliance with critical of the takeoff ice accretion(s) (c) The airplane must be shown to be § 25.111(c)(5)(i): defined in Appendices C and O of this safely controllable and maneuverable part, as applicable, in accordance with * * * * * with the most critical of the ice § 25.21(g): (d) * * * accretion(s) appropriate to the phase of (2) * * * flight as defined in Appendices C and * * * * * (ii) In icing conditions with the most O of this part, as applicable, in ■ 4. Amend § 25.111 by revising critical of the approach ice accretion(s) accordance with § 25.21(g), and with the paragraphs (c)(5)(i) and (ii) to read as defined in Appendices C and O of this critical engine inoperative and its follows: part, as applicable, in accordance with propeller (if applicable) in the minimum § 25.21(g). The climb speed selected for § 25.111 Takeoff path. drag position: non-icing conditions may be used if the * * * * * climb speed for icing conditions, * * * * * (c) * * * computed in accordance with paragraph (i) * * * (5) * * * (d)(1)(iii) of this section, does not (1) Controllability must be (i) With the most critical of the takeoff exceed that for non-icing conditions by demonstrated with the most critical of ice accretion(s) defined in Appendices C more than the greater of 3 knots CAS or the ice accretion(s) for the particular and O of this part, as applicable, in 3 percent. flight phase as defined in Appendices C and O of this part, as applicable, in accordance with § 25.21(g), from a ■ 7. Amend § 25.123 by revising accordance with § 25.21(g); height of 35 feet above the takeoff paragraph (b)(2) introductory text to surface up to the point where the read as follows: * * * * * airplane is 400 feet above the takeoff (j) For flight in icing conditions before surface; and § 25.123 En route flight paths. the ice protection system has been (ii) With the most critical of the final * * * * * activated and is performing its intended takeoff ice accretion(s) defined in (b) * * * function, it must be demonstrated in Appendices C and O of this part, as (2) In icing conditions with the most flight with the most critical of the ice applicable, in accordance with critical of the en route ice accretion(s) accretion(s) defined in Appendix C, part
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II, paragraph (e) of this part and defined in Appendix C, part II, ■ 14. Amend § 25.903 by adding a new Appendix O, part II, paragraph (d) of paragraph (e) of this part and Appendix paragraph (a)(3) to read as follows: this part, as applicable, in accordance O, part II, paragraph (d) of this part, as with § 25.21(g), that: applicable, in accordance with § 25.903 Engines. * * * * * § 25.21(g). The stall warning margin in (a) * * * (3) Each turbine engine must comply ■ 10. Amend § 25.207 by revising straight and turning flight must be with one of the following paragraphs: paragraphs (b), (e)(1), (e)(2), (e)(3), (e)(4), sufficient to allow the pilot to prevent (i) Section 33.68 of this chapter in (e)(5), and (h) introductory text as stalling without encountering any effect on January 5, 2015, or as follows: adverse flight characteristics when: * * * * * subsequently amended; or § 25.207 Stall warning. ■ 11. Amend § 25.237 by revising (ii) Section 33.68 of this chapter in * * * * * paragraph (a)(3)(ii) to read as follows: effect on February 23, 1984, or as (b) The warning must be furnished subsequently amended before January 5, either through the inherent aerodynamic § 25.237 Wind velocities. 2015, unless that engine’s ice qualities of the airplane or by a device (a) * * * accumulation service history has that will give clearly distinguishable (3) * * * resulted in an unsafe condition; or indications under expected conditions (ii) Icing conditions with the most (iii) Section 33.68 of this chapter in of flight. However, a visual stall warning critical of the landing ice accretion(s) effect on October 1, 1974, or as device that requires the attention of the defined in Appendices C and O of this subsequently amended prior to February crew within the cockpit is not part, as applicable, in accordance with 23, 1984, unless that engine’s ice acceptable by itself. If a warning device § 25.21(g). accumulation service history has is used, it must provide a warning in * * * * * resulted in an unsafe condition; or each of the airplane configurations ■ 12. Amend § 25.253 by revising (iv) Be shown to have an ice prescribed in paragraph (a) of this paragraph (c) introductory text to read accumulation service history in similar section at the speed prescribed in as follows: installation locations which has not paragraphs (c) and (d) of this section. resulted in any unsafe conditions. § 25.253 High-speed characteristics. Except for the stall warning prescribed * * * * * in paragraph (h)(3)(ii) of this section, the * * * * * ■ (c) Maximum speed for stability 15. Amend § 25.929 by revising stall warning for flight in icing paragraph (a) to read as follows: conditions must be provided by the characteristics in icing conditions. The same means as the stall warning for maximum speed for stability § 25.929 Propeller deicing. characteristics with the most critical of flight in non-icing conditions. (a) If certification for flight in icing is the ice accretions defined in sought there must be a means to prevent * * * * * Appendices C and O of this part, as or remove hazardous ice accumulations (e) * * * applicable, in accordance with that could form in the icing conditions (1) The most critical of the takeoff ice § 25.21(g), at which the requirements of defined in Appendix C of this part and and final takeoff ice accretions defined §§ 25.143(g), 25.147(f), 25.175(b)(1), in the portions of Appendix O of this in Appendices C and O of this part, as 25.177(a) through (c), and 25.181 must part for which the airplane is approved applicable, in accordance with be met, is the lower of: § 25.21(g), for each configuration used for flight on propellers or on accessories in the takeoff phase of flight; * * * * * where ice accumulation would (2) The most critical of the en route ■ 13. Amend § 25.773 by revising jeopardize engine performance. ice accretion(s) defined in Appendices C paragraph (b)(1)(ii) to read as follows: * * * * * and O of this part, as applicable, in § 25.773 Pilot compartment view. ■ 16. Amend § 25.1093 by revising accordance with § 25.21(g), for the en * * * * * paragraph (b) to read as follows: route configuration; (b) * * * (3) The most critical of the holding ice (1) * * * § 25.1093 Induction system icing accretion(s) defined in Appendices C (ii) The icing conditions specified in protection. and O of this part, as applicable, in Appendix C of this part and the * * * * * accordance with § 25.21(g), for the following icing conditions specified in (b) Turbine engines. Except as holding configuration(s); Appendix O of this part, if certification provided in paragraph (b)(3) of this (4) The most critical of the approach for flight in icing conditions is sought: section, each engine, with all icing ice accretion(s) defined in Appendices C (A) For airplanes certificated in protection systems operating, must: and O of this part, as applicable, in accordance with § 25.1420(a)(1), the (1) Operate throughout its flight accordance with § 25.21(g), for the icing conditions that the airplane is power range, including the minimum approach configuration(s); and certified to safely exit following descent idling speeds, in the icing (5) The most critical of the landing ice detection. conditions defined in Appendices C and accretion(s) defined in Appendices C (B) For airplanes certificated in O of this part, and Appendix D of part and O of this part, as applicable, in accordance with § 25.1420(a)(2), the 33 of this chapter, and in falling and accordance with § 25.21(g), for the icing conditions that the airplane is blowing snow within the limitations landing and go-around configuration(s). certified to safely operate in and the established for the airplane for such * * * * * icing conditions that the airplane is operation, without the accumulation of (h) The following stall warning certified to safely exit following ice on the engine, inlet system margin is required for flight in icing detection. components, or airframe components conditions before the ice protection (C) For airplanes certificated in that would do any of the following: system has been activated and is accordance with § 25.1420(a)(3) and for (i) Adversely affect installed engine performing its intended function. airplanes not subject to § 25.1420, all operation or cause a sustained loss of Compliance must be shown using the icing conditions. power or thrust; or an unacceptable most critical of the ice accretion(s) * * * * * increase in gas path operating
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temperature; or an airframe/engine condition, without adverse effect, duration at power), the associated incompatibility; or followed by an acceleration to takeoff minimum ambient temperature, and the (ii) Result in unacceptable temporary power or thrust in accordance with the maximum time interval. These power loss or engine damage; or procedures defined in the airplane flight conditions must be used in the analysis (iii) Cause a stall, surge, or flameout manual. During the idle operation, the that establishes the airplane operating or loss of engine controllability (for engine may be run up periodically to a limitations in accordance with example, rollback). moderate power or thrust setting in a § 25.1521. (2) Operate at ground idle speed for a manner acceptable to the Administrator. (3) For the purposes of this section, minimum of 30 minutes on the ground Analysis may be used to show ambient the icing conditions defined in in the following icing conditions shown temperatures below the tested appendix O of this part, including the in Table 1 of this section, unless temperature are less critical. The conditions specified in Condition 3 of replaced by similar test conditions that applicant must document the engine Table 1 of this section, are not are more critical. These conditions must run-up procedure (including the applicable to airplanes with a maximum be demonstrated with the available air maximum time interval between run- takeoff weight equal to or greater than bleed for icing protection at its critical ups from idle, run-up power setting, and 60,000 pounds.
TABLE 1—ICING CONDITIONS FOR GROUND TESTS
Water concentration Mean effective particle Condition Total air temperature (minimum) diameter Demonstration
1. Rime ice condition ..... 0 to 15 °F (18 to ¥9 °C) Liquid—0.3 g/m3 ...... 15–25 microns ...... By test, analysis or combination of the two. 2. Glaze ice condition .... 20 to 30 °F (¥7 to ¥1 Liquid—0.3 g/m3 ...... 15–25 microns ...... By test, analysis or combination of °C). the two. 3. Large drop condition 15 to 30 °F (¥9 to ¥1 Liquid—0.3 g/m3 ...... 100 microns (minimum) By test, analysis or combination of °C). the two.
* * * * * conditions as defined in part 33, (2) For airplanes certificated in ■ 17. Amend § 25.1323 by revising Appendix D, of this chapter; the icing accordance with § 25.1420(a)(2), the paragraph (i) to read as follows: conditions defined in Appendix C of icing conditions that the airplane is this part; and the following icing certified to safely operate in and the § 25.1323 Airspeed indicating system. conditions specified in Appendix O of icing conditions that the airplane is * * * * * this part: certified to safely exit following (i) Each system must have a heated (1) For airplanes certificated in detection. pitot tube or an equivalent means of accordance with § 25.1420(a)(1), the (3) For airplanes certificated in preventing malfunction in the heavy icing conditions that the airplane is accordance with § 25.1420(a)(3) and for rain conditions defined in Table 1 of certified to safely exit following airplanes not subject to § 25.1420, all this section; mixed phase and ice crystal detection. icing conditions.
TABLE 1—HEAVY RAIN CONDITIONS FOR AIRSPEED INDICATING SYSTEM TESTS
Altitude range Liquid water Horizontal extent Droplet MVD content μ (ft) (m) (g/m3) (km) (nmiles) ( m)
0 to 10 000 ...... 0 to 3000 ...... 1 100 50 1000 6 5 3 2000 15 1 0.5 2000
* * * * * (a) For airplanes certificated in ■ 19. Amend § 25.1325 by revising accordance with § 25.1420(a)(1), the paragraph (b) to read as follows: ■ 18. Amend part 25 by adding a new icing conditions that the airplane is section § 25.1324 to read as follows: § 25.1325 Static pressure systems. certified to safely exit following § 25.1324 Angle of attack system. detection. * * * * * (b) Each static port must be designed (b) For airplanes certificated in Each angle of attack system sensor and located so that: accordance with § 25.1420(a)(2), the must be heated or have an equivalent (1) The static pressure system icing conditions that the airplane is means of preventing malfunction in the performance is least affected by airflow certified to safely operate in and the heavy rain conditions defined in Table variation, or by moisture or other icing conditions that the airplane is 1 of § 25.1323, the mixed phase and ice foreign matter; and certified to safely exit following crystal conditions as defined in part 33, (2) The correlation between air detection. Appendix D, of this chapter, the icing pressure in the static pressure system conditions defined in Appendix C of (c) For airplanes certificated in and true ambient atmospheric static this part, and the following icing accordance with § 25.1420(a)(3) and for pressure is not changed when the conditions specified in Appendix O of airplanes not subject to § 25.1420, all airplane is exposed to the icing this part: icing conditions. conditions defined in Appendix C of
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this part, and the following icing the components or models of the ■ 22. Amend § 25.1533 by adding a new conditions specified in Appendix O of components. paragraph (c) to read as follows: this part: (2) Laboratory dry air or simulated (i) For airplanes certificated in icing tests, or a combination of both, of § 25.1533 Additional operating limitations. accordance with § 25.1420(a)(1), the models of the airplane. * * * * * icing conditions that the airplane is (3) Flight tests of the airplane or its (c) For airplanes certified in certified to safely exit following components in simulated icing accordance with § 25.1420(a)(1) or (2), detection. conditions, measured as necessary to an operating limitation must be (ii) For airplanes certificated in support the analysis. established to: accordance with § 25.1420(a)(2), the (4) Flight tests of the airplane with (1) Prohibit intentional flight, icing conditions that the airplane is simulated ice shapes. including takeoff and landing, into icing certified to safely operate in and the (5) Flight tests of the airplane in conditions defined in Appendix O of icing conditions that the airplane is natural icing conditions, measured as this part for which the airplane has not certified to safely exit following necessary to support the analysis. been certified to safely operate; and detection. (c) For an airplane certified in (iii) For airplanes certificated in accordance with paragraph (a)(2) or (3) (2) Require exiting all icing conditions accordance with § 25.1420(a)(3) and for of this section, the requirements of if icing conditions defined in Appendix airplanes not subject to § 25.1420, all § 25.1419(e), (f), (g), and (h) must be met O of this part are encountered for which icing conditions. for the icing conditions defined in the airplane has not been certified to * * * * * Appendix O of this part in which the safely operate. ■ 20. Amend part 25 by adding a new airplane is certified to operate. ■ 23. Amend Appendix C to part 25, in § 25.1420 to read as follows: (d) For the purposes of this section, part II, by revising paragraph (a)(1), the the following definitions apply: second sentence of paragraph (a)(2), and § 25.1420 Supercooled large drop icing (1) Reversible Flight Controls. Flight paragraph (d)(2) to read as follows: conditions. controls in the normal operating (a) If certification for flight in icing configuration that have force or motion Appendix C to Part 25 conditions is sought, in addition to the originating at the airplane’s control * * * * * requirements of § 25.1419, an airplane surface (for example, through PART II—AIRFRAME ICE ACCRETIONS with a maximum takeoff weight less aerodynamic loads, static imbalance, or than 60,000 pounds or with reversible FOR SHOWING COMPLIANCE WITH trim or servo tab inputs) that is SUBPART B flight controls must be capable of transmitted back to flight deck controls. operating in accordance with (a) * * * This term refers to flight deck controls (1) Takeoff ice is the most critical ice paragraphs (a)(1), (2), or (3), of this connected to the pitch, roll, or yaw section. accretion on unprotected surfaces and any control surfaces by direct mechanical ice accretion on the protected surfaces (1) Operating safely after encountering linkages, cables, or push-pull rods in appropriate to normal ice protection system the icing conditions defined in such a way that pilot effort produces operation, occurring between the end of the Appendix O of this part: motion or force about the hinge line. takeoff distance and 400 feet above the (i) The airplane must have a means to (2) Simulated Icing Test. Testing takeoff surface, assuming accretion starts at detect that it is operating in Appendix conducted in simulated icing the end of the takeoff distance in the takeoff O icing conditions; and conditions, such as in an icing tunnel or maximum icing conditions defined in part I (ii) Following detection of Appendix of this Appendix. behind an icing tanker. (2) * * * Ice accretion is assumed to start O icing conditions, the airplane must be (3) Simulated Ice Shape. Ice shape capable of operating safely while exiting at the end of the takeoff distance in the fabricated from wood, epoxy, or other takeoff maximum icing conditions of part I, all icing conditions. materials by any construction (2) Operating safely in a portion of the paragraph (c) of this Appendix. technique. icing conditions defined in Appendix O * * * * * of this part as selected by the applicant: ■ 21. Amend § 25.1521 by redesignating (d) * * * (i) The airplane must have a means to paragraph (c)(3) as paragraph (c)(4), (2) The ice accretion starts at the end of the detect that it is operating in conditions revising newly redesignated paragraph takeoff distance. that exceed the selected portion of (c)(4), and adding new paragraph (c)(3) * * * * * to read as follows: Appendix O icing conditions; and ■ 24. Amend part 25 by adding new (ii) Following detection, the airplane § 25.1521 Powerplant limitations. Appendix O to read as follows: must be capable of operating safely while exiting all icing conditions. * * * * * Appendix O to Part 25—Supercooled (3) Operating safely in the icing (c) * * * Large Drop Icing Conditions conditions defined in Appendix O of (3) Maximum time interval between engine run-ups from idle, run-up power This Appendix consists of two parts. Part this part. I defines this Appendix as a description of (b) To establish that the airplane can setting and duration at power for ground supercooled large drop icing conditions in operate safely as required in paragraph operation in icing conditions, as defined which the drop median volume diameter (a) of this section, an applicant must in § 25.1093(b)(2). (MVD) is less than or greater than 40 mm, the show through analysis that the ice (4) Any other parameter for which a maximum mean effective drop diameter protection for the various components limitation has been established as part (MED) of Appendix C of this part continuous of the airplane is adequate, taking into of the engine type certificate except that maximum (stratiform clouds) icing account the various airplane operational a limitation need not be established for conditions. For this Appendix, supercooled large drop icing conditions consist of freezing configurations. To verify the analysis, a parameter that cannot be exceeded during normal operation due to the drizzle and freezing rain occurring in and/or one, or more as found necessary, of the below stratiform clouds. Part II defines ice following methods must be used: design of the installation or to another accretions used to show compliance with the (1) Laboratory dry air or simulated established limitation. airplane performance and handling qualities icing tests, or a combination of both, of * * * * * requirements of subpart B of this part.
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PART I—METEOROLOGY extent standard distance of 17.4 nautical (6) Altitude and temperature envelope: In this Appendix icing conditions are miles. Figure 6. defined by the parameters of altitude, vertical (5) Drop diameter distribution: Figure 2. (c) Horizontal extent. (6) Altitude and temperature envelope: and horizontal extent, temperature, liquid The liquid water content for freezing Figure 3. water content, and water mass distribution as drizzle and freezing rain conditions for (b) Freezing Rain (Conditions with spectra horizontal extents other than the standard a function of drop diameter distribution. maximum drop diameters greater than 500 (a) Freezing Drizzle (Conditions with 17.4 nautical miles can be determined by the mm): value of the liquid water content determined spectra maximum drop diameters from (1) Pressure altitude range: 0 to 12,000 ft from Figure 1 or Figure 4, multiplied by the 100mm to 500 mm): MSL. factor provided in Figure 7, which is defined (1) Pressure altitude range: 0 to 22,000 feet (2) Maximum vertical extent: 7,000 ft. MSL. (3) Horizontal extent: Standard distance of by the following equation: (2) Maximum vertical extent: 12,000 feet. 17.4 nautical miles. S = 1.266 ¥ 0.213 log10(H) (3) Horizontal extent: Standard distance of (4) Total liquid water content. Where: 17.4 nautical miles. Note: LWC in grams per cubic meter (g/m3) S = Liquid Water Content Scale Factor (4) Total liquid water content. based on horizontal extent standard distance (dimensionless) and Note: Liquid water content (LWC) in grams of 17.4 nautical miles. H = horizontal extent in nautical miles per cubic meter (g/m3) based on horizontal (5) Drop Diameter Distribution: Figure 5. BILLING CODE 4910–13–P
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FIGURE 2-Appendix 0, Freezing Drizzle, Drop Diameter Distribution
1 en ~ 0.8 2 .. ·.... !... ,...... Q,) 0.6 .. .;;::: l20.4- ::I E ::I 0.2 ...... - .. •...... : ...... •• !.•I•I•!···· 0 .. i !Freezing Drizzle MVD H40 micron 0 101 102 103 Diameter (microns) 1 en ~ 0.8 2 :: I· . :... ·... : ... Q,) 0.6 .;;::: : : ~ ~ l20.4- ::I E ::I 0.2 . ITII . 0 • .• !Freezing Drizzle MVD :>, 40 micron 0 101 102 103 Diameter (microns)
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FIGURE 3 -Appendix 0, Freezing Drizzle, Temperature and Altitude
-30~------~------~------~------~------~ 0 5 10 15 20 25 Pressure Altitude (1 000-feet)
FIGURE 4-Appendix 0, Freezing Rain, Liquid Water Content
.... Q)
:-2~ 0.1 ::::l C" :.J -25 -20 -15 -10 -5 0 5 Ambient Temperature (degrees Celsius)
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FIGURE 5-Appendix 0, Freezing Rain, Drop Diameter Distribution
en ~ 0.8 ::;?! Q) 0.6 .::::: -cao.4 ::I E ::I 0.2 (.)
en ~ 0.8 ::;?! Q) 0.6 .::::: -cao.4 ::I : : ~ E . . . . ::I 0.2 (.) · !Fr~~~irig Rain MVD ; 4p microns o~~~--~~~~~~----~~~~~LL--~~ 101 102 103 Diameter (microns)
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FIGURE 6 -Appendix 0, Freezing Rain, Temperature and Altitude
5
~ 0 "iii Q) u en -5 Q) ~ C) ,_...~ -10 ~ ~ li! -15 Q) c.. E ~-20 "'E :..cQ) E -25 <(
5 10 15 20 25 Pressure Altitude (1 000-feet)
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BILLING CODE 4910–13–C (3) For an airplane certified in accordance horizontal extent in the most critical of the PART II—AIRFRAME ICE ACCRETIONS with § 25.1420(a)(3), the ice accretions for icing conditions defined in part I of this FOR SHOWING COMPLIANCE WITH each flight phase are defined in part II, Appendix and one cloud with a horizontal SUBPART B OF THIS PART paragraph (c) of this Appendix. extent of 17.4 nautical miles in the (b) Ice accretions for airplanes certified in continuous maximum icing conditions (a) General. accordance with § 25.1420(a)(1) or (2). defined in Appendix C of this part. The most critical ice accretion in terms of (1) En route ice is the en route ice as (iii) Except the total exposure to holding airplane performance and handling qualities defined by part II, paragraph (c)(3), of this ice conditions does not need to exceed 45 for each flight phase must be used to show Appendix, for an airplane certified in minutes. compliance with the applicable airplane accordance with § 25.1420(a)(2), or defined (3) Approach ice is the more critical of the performance and handling qualities by part II, paragraph (a)(3), of Appendix C of holding ice defined by part II, paragraph requirements for icing conditions contained this part, for an airplane certified in (b)(2), of this Appendix, or the ice calculated in subpart B of this part. Applicants must accordance with § 25.1420(a)(1), plus: in the applicable paragraphs (b)(3)(i) or (ii) of demonstrate that the full range of (i) Pre-detection ice as defined by part II, part II, of this Appendix: atmospheric icing conditions specified in paragraph (b)(5), of this Appendix; and part I of this Appendix have been considered, (i) For an airplane certified in accordance (ii) The ice accumulated during the transit with § 25.1420(a)(2), the ice accumulated including drop diameter distributions, liquid of one cloud with a horizontal extent of 17.4 during descent from the maximum vertical water content, and temperature appropriate nautical miles in the most critical of the icing extent of the icing conditions defined in part to the flight conditions (for example, conditions defined in part I of this Appendix I of this Appendix to 2,000 feet above the configuration, speed, angle of attack, and and one cloud with a horizontal extent of altitude). 17.4 nautical miles in the continuous landing surface in the cruise configuration, (1) For an airplane certified in accordance maximum icing conditions defined in plus transition to the approach configuration, with § 25.1420(a)(1), the ice accretions for Appendix C of this part. plus: each flight phase are defined in part II, (2) Holding ice is the holding ice defined (A) Pre-detection ice, as defined by part II, paragraph (b) of this Appendix. by part II, paragraph (c)(4), of this Appendix, paragraph (b)(5), of this Appendix; and (2) For an airplane certified in accordance for an airplane certified in accordance with (B) The ice accumulated during the transit with § 25.1420(a)(2), the most critical ice § 25.1420(a)(2), or defined by part II, at 2,000 feet above the landing surface of one accretion for each flight phase defined in part paragraph (a)(4), of Appendix C of this part, cloud with a horizontal extent of 17.4 II, paragraphs (b) and (c) of this Appendix, for an airplane certified in accordance with nautical miles in the most critical of the icing must be used. For the ice accretions defined § 25.1420(a)(1), plus: conditions defined in part I of this Appendix in part II, paragraph (c) of this Appendix, (i) Pre-detection ice as defined by part II, and one cloud with a horizontal extent of only the portion of part I of this Appendix paragraph (b)(5), of this Appendix; and 17.4 nautical miles in the continuous in which the airplane is capable of operating (ii) The ice accumulated during the transit maximum icing conditions defined in safely must be considered. of one cloud with a 17.4 nautical miles Appendix C of this part.
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(ii) For an airplane certified in accordance § 25.1420(a)(1) and (2). It is the pre-existing Appendix, to 2,000 feet above the landing with § 25.1420(a)(1), the ice accumulated ice accretion that may exist from operating in surface in the cruise configuration, plus during descent from the maximum vertical icing conditions in which the airplane is transition to the approach configuration and extent of the maximum continuous icing approved to operate prior to encountering the flying for 15 minutes at 2,000 feet above the conditions defined in part I of Appendix C icing conditions requiring an exit, plus the landing surface; or to 2,000 feet above the landing surface in the ice accumulated during the time needed to (ii) Holding ice as defined by part II, cruise configuration, plus transition to the detect the icing conditions, followed by two paragraph (c)(4), of this Appendix. approach configuration, plus: minutes of further ice accumulation to take (6) Landing ice is the ice accretion on the (A) Pre-detection ice, as defined by part II, into account the time for the flightcrew to unprotected surfaces, and any ice accretion paragraph (b)(5), of this Appendix; and take action to exit the icing conditions, on the protected surfaces appropriate to (B) The ice accumulated during the transit including coordination with air traffic normal ice protection system operation, at 2,000 feet above the landing surface of one control. resulting from the more critical of the: cloud with a horizontal extent of 17.4 (i) For an airplane certified in accordance (i) Ice accretion defined by part II, nautical miles in the most critical of the icing with § 25.1420(a)(1), the pre-existing ice paragraph (c)(5)(i), of this Appendix, plus ice conditions defined in part I of this Appendix accretion must be based on the icing accumulated in the icing conditions defined and one cloud with a horizontal extent of conditions defined in Appendix C of this in part I of this Appendix during a descent 17.4 nautical miles in the continuous part. from 2,000 feet above the landing surface to maximum icing conditions defined in (ii) For an airplane certified in accordance a height of 200 feet above the landing surface Appendix C of this part. with § 25.1420(a)(2), the pre-existing ice with a transition to the landing configuration, (4) Landing ice is the more critical of the accretion must be based on the more critical followed by a go-around at the minimum holding ice as defined by part II, paragraph of the icing conditions defined in Appendix climb gradient required by § 25.119, from a (b)(2), of this Appendix, or the ice calculated C of this part, or the icing conditions defined height of 200 feet above the landing surface in the applicable paragraphs (b)(4)(i) or (ii) of in part I of this Appendix in which the to 2,000 feet above the landing surface, flying part II of this Appendix: airplane is capable of safely operating. for 15 minutes at 2,000 feet above the landing (i) For an airplane certified in accordance (c) Ice accretions for airplanes certified in surface in the approach configuration, and a with § 25.1420(a)(2), the ice accretion defined accordance with §§ 25.1420(a)(2) or (3). For descent to the landing surface (touchdown) by part II, paragraph (c)(5)(i), of this an airplane certified in accordance with in the landing configuration; or Appendix, plus a descent from 2,000 feet § 25.1420(a)(2), only the portion of the icing (ii) Holding ice as defined by part II, above the landing surface to a height of 200 conditions of part I of this Appendix in paragraph (c)(4), of this Appendix. feet above the landing surface with a which the airplane is capable of operating (7) For both unprotected and protected transition to the landing configuration in the safely must be considered. parts, the ice accretion for the takeoff phase icing conditions defined in part I of this (1) Takeoff ice is the most critical ice must be determined for the icing conditions Appendix, plus: accretion on unprotected surfaces, and any defined in part I of this Appendix, using the (A) Pre-detection ice, as defined in part II, ice accretion on the protected surfaces, following assumptions: paragraph (b)(5), of this Appendix; and occurring between the end of the takeoff (i) The airfoils, control surfaces, and, if (B) The ice accumulated during an exit distance and 400 feet above the takeoff applicable, propellers are free from frost, maneuver, beginning with the minimum surface, assuming accretion starts at the end snow, or ice at the start of takeoff; climb gradient required by § 25.119, from a of the takeoff distance in the icing conditions (ii) The ice accretion starts at the end of the height of 200 feet above the landing surface defined in part I of this Appendix. takeoff distance; through one cloud with a horizontal extent (2) Final takeoff ice is the most critical ice (iii) The critical ratio of thrust/power-to- of 17.4 nautical miles in the most critical of accretion on unprotected surfaces, and any weight; the icing conditions defined in part I of this ice accretion on the protected surfaces (iv) Failure of the critical engine occurs at Appendix and one cloud with a horizontal appropriate to normal ice protection system VEF; and extent of 17.4 nautical miles in the operation, between 400 feet and either 1,500 (v) Crew activation of the ice protection continuous maximum icing conditions feet above the takeoff surface, or the height system is in accordance with a normal defined in Appendix C of this part. at which the transition from the takeoff to the operating procedure provided in the airplane (ii) For an airplane certified in accordance en route configuration is completed and VFTO flight manual, except that after beginning the with § 25.1420(a)(1), the ice accumulated in is reached, whichever is higher. Ice accretion takeoff roll, it must be assumed that the crew the maximum continuous icing conditions is assumed to start at the end of the takeoff takes no action to activate the ice protection defined in Appendix C of this part, during a distance in the icing conditions defined in system until the airplane is at least 400 feet descent from the maximum vertical extent of part I of this Appendix. above the takeoff surface. the icing conditions defined in Appendix C (3) En route ice is the most critical ice (d) The ice accretion before the ice of this part, to 2,000 feet above the landing accretion on the unprotected surfaces, and protection system has been activated and is surface in the cruise configuration, plus any ice accretion on the protected surfaces performing its intended function is the transition to the approach configuration and appropriate to normal ice protection system critical ice accretion formed on the flying for 15 minutes at 2,000 feet above the operation, during the en route flight phase in unprotected and normally protected surfaces landing surface, plus a descent from 2,000 the icing conditions defined in part I of this before activation and effective operation of feet above the landing surface to a height of Appendix. the ice protection system in the icing 200 feet above the landing surface with a (4) Holding ice is the most critical ice conditions defined in part I of this Appendix. transition to the landing configuration, plus: accretion on the unprotected surfaces, and This ice accretion only applies in showing (A) Pre-detection ice, as described by part any ice accretion on the protected surfaces compliance to §§ 25.143(j) and 25.207(h). II, paragraph (b)(5), of this Appendix; and appropriate to normal ice protection system (e) In order to reduce the number of ice (B) The ice accumulated during an exit operation, resulting from 45 minutes of flight accretions to be considered when maneuver, beginning with the minimum within a cloud with a 17.4 nautical miles demonstrating compliance with the climb gradient required by § 25.119, from a horizontal extent in the icing conditions requirements of § 25.21(g), any of the ice height of 200 feet above the landing surface defined in part I of this Appendix, during the accretions defined in this Appendix may be through one cloud with a horizontal extent holding phase of flight. used for any other flight phase if it is shown of 17.4 nautical miles in the most critical of (5) Approach ice is the ice accretion on the to be at least as critical as the specific ice the icing conditions defined in part I of this unprotected surfaces, and any ice accretion accretion defined for that flight phase. Appendix and one cloud with a horizontal on the protected surfaces appropriate to Configuration differences and their effects on extent of 17.4 nautical miles in the normal ice protection system operation, ice accretions must be taken into account. continuous maximum icing conditions resulting from the more critical of the: (f) The ice accretion that has the most defined in Appendix C of this part. (i) Ice accumulated in the icing conditions adverse effect on handling qualities may be (5) Pre-detection ice is the ice accretion defined in part I of this Appendix during a used for airplane performance tests provided before detection of flight conditions in this descent from the maximum vertical extent of any difference in performance is Appendix that require exiting per the icing conditions defined in part I of this conservatively taken into account.
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PART 33—AIRWORTHINESS (b) Operate throughout its flight (A) Demonstration in altitude flight STANDARDS: AIRCRAFT ENGINES power range, including minimum simulation test facility: A duration of 10 descent idle rotor speeds achievable in minutes consistent with a simulated ■ 25. The authority citation for part 33 flight, in the icing conditions defined flight descent of 10,000 ft (3 km) in is revised to read as follows: for turbojet, turbofan, and turboprop altitude while operating in Continuous Authority: 49 U.S.C. 106(g), 40113, 44701, engines in Appendices C and O of part Maximum icing conditions defined in 44702, 44704. 25 of this chapter, and for turboshaft Appendix C of part 25 of this chapter for ■ 26. Revise § 33.68 to read as follows: engines in Appendix C of part 29 of this turbojet, turbofan, and turboprop chapter. In addition: engines, and for turboshaft engines in § 33.68 Induction system icing. (1) It must be shown through Critical the icing conditions defined in Each engine, with all icing protection Point Analysis (CPA) that the complete Appendix C of part 29 of this chapter, systems operating, must: ice envelope has been analyzed, and plus 40 percent liquid water content (a) Operate throughout its flight that the most critical points must be margin, at the critical level of airspeed power range, including the minimum demonstrated by engine test, analysis, or and air temperature; or descent idle rotor speeds achievable in a combination of the two to operate (B) Demonstration in ground test flight, in the icing conditions defined acceptably. Extended flight in critical facility: A duration of 3 cycles of for turbojet, turbofan, and turboprop flight conditions such as hold, descent, alternating icing exposure engines in Appendices C and O of part approach, climb, and cruise, must be corresponding to the liquid water 25 of this chapter, and Appendix D of addressed, for the ice conditions content levels and standard cloud this part, and for turboshaft engines in defined in these appendices. lengths starting in Intermittent Maximum and then in Continuous Appendix C of part 29 of this chapter, (2) It must be shown by engine test, Maximum icing conditions defined in without the accumulation of ice on the analysis, or a combination of the two Appendix C of part 25 of this chapter for engine components that: that the engine can operate acceptably turbojet, turbofan, and turboprop (1) Adversely affects engine operation for the following durations: or that causes an unacceptable engines, and for turboshaft engines in permanent loss of power or thrust or (i) At engine powers that can sustain the icing conditions defined in unacceptable increase in engine level flight: A duration that achieves Appendix C of part 29 of this chapter, operating temperature; or repetitive, stabilized operation for at the critical level of air temperature. (2) Results in unacceptable temporary turbojet, turbofan, and turboprop (c) In addition to complying with power loss or engine damage; or engines in the icing conditions defined paragraph (b) of this section, the (3) Causes a stall, surge, or flameout in Appendices C and O of part 25 of this following conditions shown in Table 1 or loss of engine controllability. The chapter, and for turboshaft engines in of this section unless replaced by applicant must account for in-flight ram the icing conditions defined in similar CPA test conditions that are effects in any critical point analysis or Appendix C of part 29 of this chapter. more critical or produce an equivalent test demonstration of these flight (ii) At engine power below that which level of severity, must be demonstrated conditions. can sustain level flight: by an engine test:
TABLE 1—CONDITIONS THAT MUST BE DEMONSTRATED BY AN ENGINE TEST
Supercooled water Condition Total air temperature concentrations Median volume drop Duration (minimum) diameter
1. Glaze ice conditions ...... 21 to 25 °F (-6 to -4 °C) ..... 2 g/m3 ...... 25 to 35 microns ...... (a) 10-minutes for power below sustainable level flight (idle descent). (b) Must show repetitive, stabilized operation for higher powers (50%, 75%, 100%MC). 2. Rime ice conditions ...... -10 to 0 °F (-23 to -18 °C) .. 1 g/m3 ...... 15 to 25 microns ...... (a) 10-minutes for power below sustainable level flight (idle descent). (b) Must show repetitive, stabilized operation for higher powers (50%, 75%, 100%MC). 3. Glaze ice holding condi- Turbojet and Turbofan, Alternating cycle: First 1.7 20 to 30 microns ...... Must show repetitive, sta- tions. only: 10 to 18 °F (-12 to g/m3 (1 minute), Then 0.3 bilized operation (or 45 (Turbojet, turbofan, and tur- -8 °C). g/m3 (6 minute). minutes max). boprop only). Turboprop, only: 2 to 10 °F ...... (-17 to -12 °C). 4. Rime ice holding condi- Turbojet and Turbofan, 0.25 g/m3 ...... 20 to 30 microns ...... Must show repetitive, sta- tions. only: -10 to 0 °F (-23 to bilized operation (or 45 (Turbojet, turbofan, and tur- -18 °C). minutes max). boprop only). Turboprop, only: 2 to 10 °F ...... (-17 to -12 °C).
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(d) Operate at ground idle speed for operation, the engine may be run up minimum ambient temperature a minimum of 30 minutes at each of the periodically to a moderate power or capability in the engine operating following icing conditions shown in thrust setting in a manner acceptable to manual as mandatory in icing Table 2 of this section with the available the Administrator. Analysis may be conditions. The applicant must air bleed for icing protection at its used to show ambient temperatures demonstrate, with consideration of critical condition, without adverse below the tested temperature are less expected airport elevations, the effect, followed by acceleration to critical. The applicant must document following: takeoff power or thrust. During the idle any demonstrated run ups and
TABLE 2—DEMONSTRATION METHODS FOR SPECIFIC ICING CONDITIONS
Supercooled water con- Condition Total air temperature centrations Mean effective par- Demonstration (minimum) ticle diameter
1. Rime ice condition ...... 0 to 15 °F (-18 to -9 °C) ..... Liquid—0.3 g/m3 ...... 15–25 microns ...... By engine test. 2. Glaze ice condition ...... 20 to 30 °F (-7 to -1 °C) ..... Liquid—0.3 g/m3 ...... 15–25 microns ...... By engine test. 3. Snow ice condition ...... 26 to 32 °F (-3 to 0 °C) ...... Ice—0.9 g/m3 ...... 100 microns ...... By test, analysis or com- (minimum) ...... bination of the two. 4. Large drop glaze ice con- 15 to 30 °F (-9 to -1 °C) ..... Liquid—0.3 g/m3 ...... 100 microns (min- By test, analysis or com- dition (Turbojet, turbofan, imum). bination of the two. and turboprop only).
(e) Demonstrate by test, analysis, or (c) Ingestion of ice under the (e) Compliance with the requirements combination of the two, acceptable conditions of this section may not— of this section must be demonstrated by operation for turbojet, turbofan, and (1) Cause an immediate or ultimate engine ice ingestion test under the turboprop engines in mixed phase and unacceptable sustained power or thrust following ingestion conditions or by ice crystal icing conditions throughout loss; or validated analysis showing equivalence Appendix D of this part, icing envelope * * * * * of other means for demonstrating soft throughout its flight power range, body damage tolerance. (d) For an engine that incorporates a including minimum descent idling protection device, compliance with this (1) The minimum ice quantity and speeds. dimensions will be established by the ■ section need not be demonstrated with 27. Amend § 33.77 by adding respect to ice formed forward of the engine size as defined in Table 1 of this paragraph (a) and revising paragraphs protection device if it is shown that— section. (c) introductory text, (c)(1), (d), and (e) (2) The ingested ice dimensions are to read as follows: (1) Such ice is of a size that will not pass through the protective device; determined by linear interpolation § 33.77 Foreign object ingestion ice. (2) The protective device will between table values, and are based on (a) Compliance with the requirements withstand the impact of the ice; and the actual engine’s inlet hilite area. of this section must be demonstrated by (3) The ice stopped by the protective (3) The ingestion velocity will engine ice ingestion test or by validated device will not obstruct the flow of simulate ice from the inlet being sucked analysis showing equivalence of other induction air into the engine with a into the engine. means for demonstrating soft body resultant sustained reduction in power (4) Engine operation will be at the damage tolerance. or thrust greater than those values maximum cruise power or thrust unless * * * * * defined by paragraph (c) of this section. lower power is more critical.
TABLE 1—MINIMUM ICE SLAB DIMENSIONS BASED ON ENGINE INLET SIZE
Engine Inlet Hilite area Thickness Width Length (sq. inch) (inch) (inch) (inch)
0 ...... 0.25 0 3.6 80 ...... 0 .25 6 3.6 300 ...... 0.25 12 3.6 700 ...... 0.25 12 4.8 2800 ...... 0 .35 12 8.5 5000 ...... 0 .43 12 11.0 7000 ...... 0 .50 12 12.7 7900 ...... 0 .50 12 13.4 9500 ...... 0 .50 12 14.6 11300 ...... 0.50 12 15.9 13300 ...... 0.50 12 17.1 16500 ...... 0.5 12 18.9 20000 ...... 0.5 12 20.0
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Appendix C [Added and Reserved] Appendix D to Part 33—Mixed Phase and Ice Crystal Icing Envelope (Deep ■ 28. Amend part 33 by adding and Convective Clouds) reserving a new Appendix C. The ice crystal icing envelope is depicted ■ 29. Amend part 33 by adding a new in Figure D1 of this Appendix. Appendix D to read as follows: BILLING CODE 4910–13–P
Within the envelope, total water content from sea level to higher altitudes and scaled over a range of ambient temperature within (TWC) in g/m3 has been determined based by a factor of 0.65 to a standard cloud length the boundaries of the ice crystal envelope upon the adiabatic lapse defined by the of 17.4 nautical miles. Figure D2 of this specified in Figure D1 of this Appendix. convective rise of 90% relative humidity air Appendix displays TWC for this distance
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Ice crystal size median mass dimension TABLE 1—SUPERCOOLED LIQUID The TWC levels displayed in Figure D2 of (MMD) range is 50–200 microns (equivalent PORTION OF TWC this Appendix represent TWC values for a spherical size) based upon measurements standard exposure distance (horizontal cloud near convective storm cores. Horizontal cloud length) of 17.4 nautical miles that must be The TWC can be treated as completely Temperature length—nautical LWC— adjusted with length of icing exposure. range—deg C g/m3 glaciated (ice crystal) except as noted in the miles Table 1 of this Appendix. 0 to –20 ...... ≤50 ...... ≤1.0 0 to –20 ...... Indefinite ...... ≤0.5 < –20 ...... 0
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Issued under authority provided by 49 U.S.C. 106(f) and 44701(a) in Washington, DC, on October 22, 2014. Michael P. Huerta, Administrator. [FR Doc. 2014–25789 Filed 11–3–14; 8:45 am] BILLING CODE 4910–13–C
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