Special Conditions: Airbus Helicopters Model H160-B Helicopter; Extended Duration of Flight After Loss of Main Gearbox Lubrication

<RULE> DEPARTMENT OF TRANSPORTATION <SUBAGY>Federal Aviation Administration</SUBAGY> <CFR>14 CFR Part 29</CFR> <DEPDOC>[Docket No. FAA-2021-1143; Special Conditions No. 29-055-SC]</DEPDOC> <SUBJECT>Special Conditions: Airbus Helicopters Model H160-B Helicopter; Extended Duration of Flight After Loss of Main Gearbox Lubrication</SUBJECT> <HD SOURCE="HED">AGENCY:</HD> Federal Aviation Administration (FAA), DOT. <HD SOURCE="HED">ACTION:</HD> Final special conditions. <SUM> <HD SOURCE="HED">SUMMARY:</HD> These special conditions are issued for the Airbus Helicopters (Airbus) Model H160-B helicopter. This helicopter has a novel or unusual design feature when compared to the state of technology envisioned in the airworthiness standards for helicopters. This design feature is the extended duration of continued safe flight and landing beyond 30 minutes after indication to the flightcrew of the loss of main gearbox lubrication. The applicable airworthiness regulations do not contain adequate or appropriate safety standards for this design feature. These special conditions contain the additional safety standards that the Administrator considers necessary to establish a level of safety equivalent to that established by the existing airworthiness standards. </SUM> <EFFDATE> <HD SOURCE="HED">DATES:</HD> Effective June 6, 2024. </EFFDATE> <FURINF> <HD SOURCE="HED">FOR FURTHER INFORMATION CONTACT:</HD> Kamron Dowlatabadi, Mechanical Systems, AIR-623, Technical Policy Branch, Policy and Standards Division, Aircraft Certification Service, 10101 Hillwood Parkway, Fort Worth, TX 76177; telephone (817) 222-5219; email <E T="03">Kamron.M.Dowlatabadi@faa.gov.</E> </FURINF> <SUPLINF> <HD SOURCE="HED">SUPPLEMENTARY INFORMATION:</HD> <HD SOURCE="HD1">Background</HD> On July 10, 2023, Airbus applied for an amendment to Type Certificate No. R00009RD for the Model H160-B helicopter to include continued safe flight and landing beyond 30 minutes after indication to the flightcrew of the loss of main gearbox lubrication. The Airbus Model H160-B helicopter is a transport-category, twin-turboshaft-engine helicopter certificated under 14 CFR part 29. This helicopter has a maximum takeoff weight of 13,436 lbs. with seating for 12 passengers and 2 flightcrew members. The Airbus Model H160-B helicopter is also characterized by the integration of composite materials in its airframe, five main rotor blades (Blue Edge technology), a Fenestron tail rotor, and a Helionix avionics suite. <HD SOURCE="HD1">Type Certification Basis</HD> Under the provisions of 14 CFR 21.101, Airbus must show that the Model H160-B helicopter meets the applicable provisions of the regulations listed in Type Certificate No. R00009RD, or the applicable regulations in effect on the date of application for the change, except for earlier amendments as agreed upon by the FAA. If the Administrator finds that the applicable airworthiness regulations ( <E T="03">i.e.,</E> 14 CFR part 29) do not contain adequate or appropriate safety standards for the Airbus Model H160-B helicopter because of a novel or unusual design feature, special conditions are prescribed under the provisions of § 21.16. Special conditions are initially applicable to the model for which they are issued. Should the type certificate for that model be amended later to include any other model that incorporates the same or similar novel or unusual design feature, the special conditions would also apply to the other model under § 21.101. In addition to the applicable airworthiness regulations and special conditions, the Airbus Model H160-B helicopter must comply with the noise certification requirements of 14 CFR part 36. The FAA issues special conditions, as defined in 14 CFR 11.19, in accordance with § 11.38, and they become part of the type-certification basis under § 21.101. <HD SOURCE="HD1">Novel or Unusual Design Features</HD> The Airbus Model H160-B helicopter will incorporate the following novel or unusual design feature: Extended duration of continued safe flight and landing beyond 30 minutes after indication to the flightcrew of the loss of main gearbox lubrication. <HD SOURCE="HD1">Discussion</HD> Current regulations do not prescribe a duration for continued safe flight and landing to be specifically called out in the rotorcraft flight manual when a loss of main gearbox lubrication is indicated to the flightcrew. Although § 29.927(c)(1) requires a 30-minute test to show that the rotor drive system, which is defined in § 29.917(a) and includes the main gearbox, is operational for 30 minutes following the indication to the flightcrew of a loss of lubrication, the associated bench test conditions may not be representative of aircraft flight conditions because a 30-minute bench test of the main gearbox may not translate to 30 minutes of continued safe flight and landing. The novel or unusual design feature of the Airbus Model H160-B helicopter is intended to enable the helicopter to continue safe flight and landing, for a minimum of 30 minutes, to the intended destination or to a safe landing location after the indication to the flightcrew of a loss of main gearbox lubrication. To meet this minimum 30 minutes of continued safe flight and landing, the Airbus Model H160-B helicopter main gearbox is designed with a redundant lubrication system. This main gearbox redundant lubrication system would allow continued safe operation after the failure of a single lubrication system. Current regulations do not address a redundant lubrication system that allows operation after the failure of a single lubrication system because at the time the existing regulations were issued, the agency did not envision that a flight duration of more than 30 minutes after the indication to the flightcrew of the loss of main gearbox lubrication was needed. Accordingly, these special conditions provide testing criteria to ensure the reliability of the redundant lubrication system to provide an extended period for safe flight and landing beyond 30 minutes after indication to the flightcrew of the loss of the main gearbox lubrication. These special conditions add new requirements in lieu of the existing airworthiness standards in §§ 29.917(a) and 29.927(c) and add a requirement to § 29.1585. At the time of the issuance of the existing regulations, the FAA did not envision the evolving operations for these types of aircraft and the regulations did not include the main gearbox lubrication system components in the required design assessment of the rotor drive system. Accordingly, these special conditions include requirements for addressing “any associated lubrication system components including oil coolers” in the design assessment required by § 29.917(b). These special conditions add a safety margin over the current 30-minute rotor drive system test specified in § 29.927(c)(1) by requiring a test duration of more than 30 minutes to ensure that the rotor drive gearbox system has an in-flight operational endurance capability of at least 30 minutes following a failure of any one pressurized, normal-use lubrication system. The 30-minute test interval starts when the lubrication-failure indication to the flightcrew is triggered and the engine is at maximum continuous power. These special conditions require a bench test of the rotor drive system main gearbox for a minimum of 30 minutes to establish a maximum period of in-flight operation following loss of main gearbox lubrication, and to ensure that the main gearbox continues to operate safely for at least 30 minutes after an indication to the flightcrew of a loss of lubrication. The term “confidence” specified in Category A and B in these special conditions necessitates the applicant provide supporting data with respect to the mechanical behavior of the main gearbox and must reflect the applicant's confidence in the repeatability of the certification test data. Test loading, in the context of these special conditions, refers to the engine, main gearbox, clutch system, and rotors (or similar test apparatus) interconnected and operating in unison, as this combination of mechanical elements pertains to power input transmitted to the main gearbox and subsequent reaction torques simulating operating conditions. These special conditions add a requirement that the maximum duration of operation after a failure, which results in a loss of main gearbox lubrication and an associated indication to the flightcrew, must be furnished in the rotorcraft flight manual, and the duration must not exceed the maximum period of in-flight operational endurance capability substantiated. These special conditions contain the additional safety standards that the Administrator considers necessary to establish a level of safety equivalent to that established by the existing airworthiness standards. <HD SOURCE="HD1">Discussion of Comments</HD> The FAA issued Notice of Proposed Special Conditions No. 29-21-01-SC for the Airbus Model H160-B helicopter, which was published in the <E T="04">Federal Register</E> on May 12, 2023 (88 FR 30680). The FAA received several comments from Leonardo Helicopters regarding the proposed special conditions. Leonardo Helicopters requested the FAA generally maintain harmonization and alignment with the EASA certification specifications (CS) 29 requirements by implementing the same changes to part 29 that were introduced by EASA rulemaking task RMT.0608, following notice of proposed amendment (NPA) 2017-07, <E T="03">Rotorcraft gearbox loss of lubrication,</E> through Amendment 5. This request relating to the pursuit of future rulemaking for part 29 is beyond the scope of these special conditions. No change was made to these special conditions as a result of this comment. Leonardo Helicopters stated that EASA's CS-29 requirements and acceptable means of compliance (AMC) clearly define h ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ Preview showing 10k of 19k characters. Full document text is stored and available for version comparison. ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━