42278 Federal Register / Vol. 65, No. 132 / Monday, July 10, 2000 / Rules and Regulations shipments; and (5) this rule provides a FOR FURTHER INFORMATION CONTACT: Jay materials introduce fatigue 60-day comment period, and any Turnberg, FAA, Engine and Propeller characteristics and failure modes that comments received will be considered Standards Staff, Engine and Propeller differ from metallic materials. prior to finalization of this rule. Directorate, Aircraft Certification The requirements of part 35 were Service, ANE–110, 12 New England established to address the airworthiness List of Subjects in 7 CFR Part 947 Executive Park, Burlington, considerations associated with metal Marketing agreements, Potatoes, Massachusetts, 01803–5229; telephone propeller blades. Propeller blades Reporting and recordkeeping (781) 238–7116; fax (781) 238–7199. constructed using composite material requirements. SUPPLEMENTARY INFORMATION: may be subject to damage due to the For the reasons set forth in the high impact forces associated with a preamble, 7 CFR Part 947 is amended as Background bird strike. Thus, composite propellers follows: On February 9, 1999, Hamilton must demonstrate propeller integrity Sundstrand applied for type following a bird strike. PART 947ÐIRISH POTATOES GROWN certification for a new model NP2000 Part 35 does not require a IN MODOC AND SISKIYOU COUNTIES, propeller. The NP2000 propeller uses a demonstration of propeller integrity CALIFORNIA, AND IN ALL COUNTIES digital electro-hydraulic control system following a lightning strike. Composite IN OREGON, EXCEPT MALHEUR and blades that are constructed of blades may not safely conduct or COUNTY composite material. dissipate the electrical current from a Conventional propellers on turboprop lightning strike. Severe damage can 1. The authority citation for 7 CFR aircraft use a mechanical governor in result if the propellers are not properly Part 947 continues to read as follows: the propeller control system that senses protected. Therefore, composite blades Authority: 7 U.S.C. 601–674. propeller speed and adjusts the pitch by must demonstrate propeller integrity 2. In Part 947, §§ 947.120, 947.123, directing hydraulic oil to the propeller following a lightning strike. 947.125, 947.130, 947.132, 947.133, actuator to increase or decrease pitch to The existing certification 947.134, 947.141, 947.180, 947.247, and maintain the propeller at the correct requirements only address structural 947.340 are suspended in their entirety revolutions per minute (RPM). When and fatigue evaluation of metal effective July 1, 2000. the mechanical governor fails, the propeller blades or hubs, and those metal components of non-metallic blade Dated: July 5, 2000. propeller pitch is controlled by a backup mechanical overspeed governor. assemblies. Allowable design stress Robert C. Keeney, The Hamilton Sundstrand model limits for composite blades must Deputy Administrator, Fruit and Vegetable NP2000 propeller uses a digital consider the deteriorating effects of the Programs. electronic governor in the propeller environment and in-service use, [FR Doc. 00–17415 Filed 7–6–00; 9:48 am] control system. The digital electronic particularly those effects from BILLING CODE 3410±02±P governor is designed to operate a hydro- temperature, moisture, erosion and mechanical interface to direct hydraulic chemical attack. Composite blades also oil to the propeller actuator to increase present new and different DEPARTMENT OF TRANSPORTATION or decrease pitch. The digital electronic considerations for retention of the governor logic commands speed blades in the propeller hub. Federal Aviation Administration governing, synchrophasing, failure The applicable airworthiness monitoring and provides beta requirements do not contain adequate or 14 CFR Part 35 scheduling. The digital electronic appropriate safety standards for these [Docket No. NE±120; Special Conditions No. governor introduces potential failures novel and unusual design features. 35±001±SC] associated with electrical power, Type Certification Basis software commands, data, and Special Conditions: Hamilton environmental effects that can result in Under § 21.17, Hamilton Sundstrand Sundstrand, Model NP2000 Propeller hazardous propeller effects. In addition must show that the model NP2000 to these features, the system has a propeller meets the applicable AGENCY: Federal Aviation provisions of § 21.21 and part 35. Administration (FAA), DOT. backup mechanical overspeed governor. The special conditions address the If the Administrator finds that the ACTION: Final special conditions. following airworthiness issues for the applicable airworthiness regulations (i.e. part 35), do not contain adequate or SUMMARY: These special conditions are Hamilton Sundstrand model NP2000 propeller: appropriate safety standards for the issued for the Hamilton Sundstrand model NP2000 propeller because of a model NP2000 constant speed propeller. 1. Safety assessment; 2. Propeller control system; novel or unusual design feature, special This eight-bladed propeller uses a dual 3. Centrifugal load tests; conditions are prescribed under the acting digital electro-hydraulic propeller 4. Fatigue limits and evaluation; provisions of § 21.16. control system and has blades 5. Bird impact; and Special conditions, as appropriate, are constructed of composite materials. 6. Lightning strike. issued in accordance with § 11.49 after These design features are novel and The Hamilton Sundstrand model public notice, as required by §§ 11.28 unusual. The applicable airworthiness NP2000 propeller incorporates propeller and 11.29(b), and become part of the regulations do not contain adequate or blades constructed of composite type certification basis in accordance appropriate safety standards for these material. This material has fibers that with § 21.17(a)(2). design features. These special are woven or aligned in specific Special conditions are initially conditions contain the additional safety directions to give the material applicable to the model for which they standards that the Administrator directional strength properties. These are issued. Should the type certificate considers necessary to establish a level properties depend on the type of fiber, for that model be amended later to of safety equivalent to that established the orientation and concentration of include any other model that by the existing airworthiness standards. fiber, and the resin matrix material that incorporates the same novel or unusual DATES: Effective date August 9, 2000. binds the fibers together. Composite design features, the special conditions

VerDate 112000 16:51 Jul 07, 2000 Jkt 190000 PO 00000 Frm 00004 Fmt 4700 Sfmt 4700 E:\FR\FM\10JYR1.SGM pfrm02 PsN: 10JYR1 Federal Register / Vol. 65, No. 132 / Monday, July 10, 2000 / Rules and Regulations 42279 would also apply to the other model electronic control components perform Propeller blade and spinner under the provisions of § 21.101(a)(1). the same basic function but use construction now use composite software, electronic circuitry, and materials that have a higher potential for Novel or Unusual Design Features electro-hydraulic actuators. The damage from bird impact. The NP2000 propeller will electronic control systems may also The need for bird impact incorporate the following novel and incorporate additional functions such as requirements was recognized when unusual design features: dual acting failure monitoring, synchrophasing and composite blades were introduced in digital electro-hydraulic propeller beta scheduling. This addition of the 1970’s; the safety issue has been control system and blades constructed electronics to the control system may addressed by special tests and special of composite materials. Special introduce new failure modes that can conditions for composite blade conditions for a safety assessment, the result in hazardous propeller effects. certifications. These special conditions propeller control system, centrifugal Centrifugal Load Tests were unique for each propeller and load tests, fatigue limits and evaluation, effectively stated that the propeller will bird impact, and lightning strike address Section 35.35 currently requires that withstand a four-pound bird impact the novel and unusual design features. the hub and blade retention without contributing to a hazardous The special conditions are discussed arrangement of propellers with propeller effect. These special tests and below. detachable blades be tested to a special conditions have been effective centrifugal load of twice the maximum Safety Assessment for over four million flight hours. There centrifugal force to which the propeller have not been any accidents attributed The special conditions require the would be subjected during operation. applicant to conduct a safety assessment to bird impact on composite propellers. This requirement is limited to the blade The selection of a four-pound bird has of the propeller in conjunction with the and hub retention capacity and does not requirements for evaluating the digital been substantiated by the extensive address composite materials and service history of blades that have been electro-hydraulic control system. A composite construction of the propeller safety assessment is necessary due to designed using the four-pound bird assembly or changes in materials due to criteria. the increased complexity of these service degradation and environmental propeller designs and related control factors. Lightning Strike systems. The ultimate objective of the safety assessment requirement is to Fatigue Limits and Evaluation Currently there are no lightning strike ensure that the collective risk from all The current requirement does not requirements in part 35. The need for propeller failure conditions is adequately address composite materials lightning strike requirements was acceptably low. The basis is the concept and is limited to metallic hubs and recognized when composite blades were that an acceptable total propeller design blades and primary load-carrying metal first introduced in the 1970’s; the safety risk is achievable by managing the components of non-metallic blades. The issue has been addressed by special individual risks to acceptable levels. special conditions expand the tests and special conditions for each This concept emphasizes reducing the requirements to include all materials design using composite blades. The risk of an event proportionally with the and components whose failure would special tests and special conditions, severity of the hazard it represents. cause a hazardous propeller effect and which were unique for each propeller, The special conditions are written at to take into account material effectively stated that the propeller must the propeller level for a typical aircraft. degradation expected in service, be able to withstand a lightning strike The typical aircraft may be the aircraft material property variations, without contributing to a hazardous intended for installation of the manufacturing variations, and propeller effect. These special tests and propeller. It is advised that the propeller environmental effects. The special special conditions have been effective applicant have an understanding of the conditions clarify that the fatigue limits for over four million flight hours. There intended aircraft, not to show may be determined by tests or analysis have not been any accidents attributed compliance with this requirement, but based on tests. The components whose to a lightning strike on composite to design a propeller that will be failure may cause a hazardous propeller propellers. acceptable for the intended aircraft. For effect include control system Discussion of Comments example, a part 25 aircraft may require components, when applicable. different failure effects and probability The special conditions require the Interested persons have been afforded of failure than a part 23 aircraft. applicant to conduct fatigue evaluation the opportunity to participate in the Showing compliance with the on a typical aircraft or on an aircraft making of these special conditions. No requirement without consideration of used during aircraft certification to comments were received on the special the intended aircraft may result in a conduct the vibration tests and conditions as proposed. After careful propeller that cannot be installed on the evaluation required by either §§ 23.907 review of the available data, the FAA intended aircraft. or 25.907. The typical aircraft may be has determined that air safety and the one used to develop design criteria for public interest require the adoption of Propeller Control System the propeller or another appropriate the special conditions without change. Currently, part 35 does not adequately aircraft. Applicability address propellers with combined mechanical, hydraulic, digital, and Bird Impact As discussed above, these special electronic control systems. Propeller Currently there are no bird impact conditions are applicable to the mechanical control systems certified requirements in part 35. The existing Hamilton Sundstrand model NP2000 under the existing requirements requirements only address the propeller. Should Hamilton Sundstrand incorporate a mechanical governor that airworthiness considerations associated apply at a later date for a change to the senses propeller speed and adjusts the with propellers that use wood and metal type certificate to include another pitch to absorb the engine power to blades. Propeller blades of this type model incorporating the same or novel maintain the propeller at the selected have demonstrated good service or unusual design features, the special rotational speed. Propellers with digital experience following a bird strike. conditions would apply to that model as

VerDate 112000 09:57 Jul 07, 2000 Jkt 190000 PO 00000 Frm 00005 Fmt 4700 Sfmt 4700 E:\FR\FM\10JYR1.SGM pfrm08 PsN: 10JYR1 42280 Federal Register / Vol. 65, No. 132 / Monday, July 10, 2000 / Rules and Regulations well under the provisions of (iv) A significant uncontrollable (4) If reliance is placed on a system or § 21.101(a)(1). torque or speed fluctuation. device, such as safety devices, (b) Safety analysis. feathering and overspeed systems, Conclusion (1)(i) An analysis of the propeller instrumentation, early warning devices, This action affects only certain novel system must be carried out to assess the maintenance checks, and similar or unusual design features on one model likely consequence of all failures that equipment or procedures, to prevent a of propellers. It is not a rule of general can reasonably be expected to occur. failure from progressing to hazardous applicability, and it affects only the This analysis must consider the propeller effects, the possibility of a applicant who applied to the FAA for following: safety system failure in combination approval of these features on the (A) The propeller system in a typical with a basic propeller failure must be propeller. installation. When the analysis depends covered. If items of a safety system are on representative components, assumed List of Subjects in 14 CFR Part 35 outside the control of the propeller interfaces, or assumed installed manufacturer, the assumptions of the Air transportation, Aircraft, Aviation conditions, the assumptions must be safety analysis with respect to the safety, Safety. stated in the analysis. reliability of these parts must be clearly The authority citations for these (B) Consequential secondary failures stated in the analysis and identified in special conditions are as follows: and latent failures. the installation and operation Authority: 49 U.S.C. 106(g), 40113, 44701– (C) Multiple failures referred to in instructions required under § 35.3. 44702, 44704. paragraph (b)(4) or that result in (5) If the acceptability of the safety hazardous propeller effects. analysis is dependent on one or more of The Special Conditions (ii) A summary must be made of those the following, it must be identified in failures that could result in major Accordingly, pursuant to the the analysis and appropriately propeller effects or hazardous propeller authority delegated to me by the substantiated. effects, together with an estimate of the Administrator, the following special (i) Performance of mandatory probability of occurrence of those conditions are issued as part of the type maintenance actions at stated intervals certification basis for Hamilton effects. (iii) It must be shown that hazardous required for certification and other Sundstrand model NP2000 propellers. propeller effects are not predicted to maintenance actions. This includes the In addition to the requirements of part verification of the serviceability of items 35, the following requirements apply to occur at a rate in excess of that defined as extremely remote (probability of 10¥7 that could fail in a latent manner. These the propeller. maintenance intervals must be (a) Definitions. Unless otherwise or less per propeller flight hour). The estimated probability for individual published in the appropriate manuals. approved by the Administrator and Additionally, if errors in maintenance of documented in the appropriate manuals failures may be insufficiently precise to enable the total rate for hazardous the propeller system could lead to and certification documents, for the hazardous propeller effects, the purpose of these special conditions the propeller effects to be assessed. For propeller certification, it is acceptable to appropriate procedures must be following definitions apply to the published in the appropriate propeller propeller: consider that the intent of this paragraph has been achieved if the manuals. (1) Propeller. The propeller is defined (ii) Verification of the satisfactory by the components listed in the type probability of a hazardous propeller effect arising from an individual failure functioning of safety or other devices at design. pre-flight or other stated periods. The (2) Propeller system. The propeller can be predicted to be not greater than ¥ details of this satisfactory functioning system consists of the propeller plus all 10 8 per propeller flight hour. It will also be accepted that, in dealing with must be published in the appropriate the components necessary for its manuals. functioning, but not necessarily probabilities of this low order of magnitude, absolute proof is not (iii) The provisions of specific included in the propeller type design. instrumentation not otherwise required. (3) Hazardous propeller effects. The possible and reliance must be placed on (iv) A fatigue assessment. following are regarded as hazardous engineering judgment and previous (6) If applicable, the safety analysis propeller effects: experience combined with sound design must include the assessment of (i) A significant overspeed of the and test philosophies. indicating equipment, manual and propeller. (iv) It must be shown that major (ii) The development of excessive propeller effects are not predicted to automatic controls, governors and drag. occur at a rate in excess of that defined propeller control systems, ¥ (iii) Thrust in the opposite direction as remote (probability of 10 5 or less synchrophasers, synchronizers, and to that commanded by the pilot. per propeller flight hour). propeller thrust reversal systems. (iv) A release of the propeller or any (2) If significant doubt exists as to the (c) Propeller control system. The major portion of the propeller. effects of failures or likely combination requirements of this section are (v) A failure that results in excessive of failures, any assumption of the effect applicable to any system or component unbalance. may be required to be verified by test. that controls, limits or monitors (vi) The unintended movement of the (3) It is recognized that the probability propeller functions. propeller blades below the established of primary failures of certain single (1) The propeller control system must minimum in-flight low pitch position. elements (for example, blades) cannot be designed, constructed and validated (4) Major propeller effects. The be sensibly estimated in numerical to show that: following are regarded as major terms. If the failure of such elements is (i) The propeller control system, propeller effects: likely to result in hazardous propeller operating in normal and alternative (i) An inability to feather. effects, reliance must be placed on operating modes and transition between (ii) An inability to command a change meeting the prescribed integrity operating modes, performs the intended in propeller pitch. requirements of part 35 and these functions throughout the declared (iii) A significant uncommanded special conditions. These instances operating conditions and flight change in pitch. must be stated in the safety analysis. envelope.

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(ii) The propeller control system accounting for environmental (i) The intended aircraft, by functionality is not adversely affected degradation expected in service, complying with §§ 23.907 or 25.907 as by the declared environmental complies with paragraphs (d)(1), (d)(2) applicable; or conditions, including temperature, and (d)(3) of these special conditions (ii) A typical aircraft. electromagnetic interference (EMI), high without evidence of failure, (f) Bird impact. It must be intensity radiated fields (HIRF) and malfunction, or permanent deformation demonstrated, by tests or analysis based lightning. The environmental limits to that would result in a major or on tests or experience on similar which the system has been satisfactorily hazardous propeller effect. designs, that the propeller is capable of validated must be documented in the Environmental degradation may be withstanding the impact of a four pound appropriate propeller manuals. accounted for by adjustment of the loads bird at the critical location(s) and (iii) A method is provided to indicate during the tests. critical flight condition(s) of the that an operating mode change has (1) The hub, blade retention system, intended aircraft without causing a occurred if flight crew action is and counterweights must be tested for a major or hazardous propeller effect. required. In such an event, operating period of one hour to a load equivalent (g) Lightning strike. It must be instructions must be provided in the to twice the maximum centrifugal load demonstrated, by tests or analysis based appropriate manuals. to which the propeller would be on tests or experience on similar (2) The propeller control system must subjected during operation at the designs, that the propeller is capable of be designed and constructed so that, in maximum rated rotational speed. withstanding a lightning strike without addition to compliance with paragraph (2) If appropriate, blade features causing a major or hazardous propeller (b), Safety analysis: associated with transitions to the effect. (i) A level of integrity consistent with retention system (e.g., a composite blade Issued in Burlington, Massachusetts on the intended aircraft is achieved. bonded to a metallic retention) may be June 27, 2000. (ii) A single failure or malfunction of tested either during the test required by electrical or electronic components in David A. Downey, paragraph (d)(1) or in a separate the control system does not cause a Assistant Manager, Engine and Propeller component test. hazardous propeller effect. Directorate, Aircraft Certification Service. (iii) Failures or malfunctions directly (3) Components used with or attached [FR Doc. 00–17242 Filed 7–7–00; 8:45 am] affecting the propeller control system in to the propeller (e.g., spinners, de-icing BILLING CODE 4910±13±P a typical aircraft, such as structural equipment, and blade erosion shields) failures of attachments to the control, must be subjected to a load equivalent fire, or overheat, do not lead to a to 159 percent of the maximum DEPARTMENT OF TRANSPORTATION centrifugal load to which the hazardous propeller effect. Federal Aviation Administration (iv) The loss of normal propeller pitch component would be subjected during control does not cause a hazardous operation at the maximum rated 14 CFR Part 39 propeller effect under the intended rotational speed. This must be operating conditions. performed by either: [Docket No. 2000±CE±20±AD; Amendment (v) The failure or corruption of data or (i) Testing at the required load for a 39±11817; AD 2000±14±08] period of 30 minutes; or signals shared across propellers does RIN 2120±AA64 not cause a major or hazardous (ii) Analysis based on test. propeller effect. (e) Fatigue limits and evaluation. (1) Airworthiness Directives; The New (3) Electronic propeller control system Fatigue limits must be established by Piper Aircraft, Inc. PA±42 Series imbedded software must be designed tests or analysis based on tests, for Airplanes and implemented by a method approved propeller: by the Administrator that is consistent (i) Hubs; AGENCY: Federal Aviation with the criticality of the performed (ii) Blades; Administration, DOT. functions and minimizes the existence (iii) Blade retention components; and ACTION: Final rule. of software errors. (iv) Other components that are (4) The propeller control system must SUMMARY: This document adopts a new affected by fatigue loads and that are be designed and constructed so that the airworthiness directive (AD) that shown under paragraph (b), Safety failure or corruption of aircraft-supplied applies to all The New Piper Aircraft, analysis, as having a fatigue failure data does not result in hazardous Inc. (Piper) PA–42 series airplanes that mode leading to hazardous propeller propeller effects. are equipped with pneumatic deicing (5) The propeller control system must effects. boots. This AD requires you to revise be designed and constructed so that the (2) The fatigue limits must take the the Airplane Flight Manual (AFM) to loss, interruption or abnormal following into account: include requirements for activation of characteristic of aircraft-supplied (i) All known and reasonably the airframe pneumatic deicing boots. electrical power does not result in foreseeable vibration and cyclic load This AD is the result of reports of in- hazardous propeller effects. The power patterns that are expected in service; flight incidents and an accident (on quality requirements must be described and airplanes other than the affected Piper in the appropriate manuals. (ii) Expected service deterioration, airplanes) that occurred in icing (6) The propeller control system variations in material properties, conditions where the airframe description, characteristics and manufacturing variations, and pneumatic deicing boots were not authority, in both normal operation and environmental effects. activated. The Piper PA–42 series failure conditions, and the range of (3) A fatigue evaluation of the airplanes have a similar type design (as control of other controlled functions propeller must be conducted to show it relates to airframe pneumatic deice must be specified in the appropriate that hazardous propeller effects due to boots) to the incident and accident propeller manuals. fatigue will be avoided throughout the airplanes. The actions specified by this (d) Centrifugal load tests. It must be intended operational life of the AD are intended to assure that flight demonstrated that a propeller, propeller on either: crews activate the pneumatic wing and

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