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Federal Register / Vol. 86, No. 184 / Monday, September 27, 2021 / Rules and Regulations
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provided in Special Condition no. 1, 33.4, Instructions for continued airworthiness, and its appendix, apply to the magniX engines. The FAA made no changes to the special condition as a result of the comment.
Special Condition No. 6, Engine Cooling The FAA proposed that Special Condition no. 6 would require the engine design and construction to comply with 14 CFR 33.21. That regulation requires the engine design and construction to provide necessary cooling under conditions in which the airplane is expected to operate and would otherwise be applicable only to reciprocating and turbine aircraft engines. Additionally, this special condition proposed to require the applicant to document the cooling system monitoring features and usage in the engine installation manual, if cooling is required to satisfy the safety analysis described in Special Condition no. 17. Loss of adequate cooling to an engine that operates using electrical technology can result in rapid overheating and abrupt engine failure with critical consequences to safety.
Comment Summary: GE suggested that Special Condition no. 6 is redundant to Special Condition no. 17
Safety analysis because it includes 14
CFR 33.75d Safety analysis, and should be deleted.
FAA Response: The FAA does not agree with the suggested change. The reference to 33.75d in Special Condition no. 17 does not explicitly address cooling systems that are necessary for the engine to comply with the safety analysis. Special Condition no. 6 requires additional information about the cooling system that is not specified in 33.75d. The FAA made no change to Special Condition no. 6 as a result of this comment.
Comment Summary: Ampaire suggested that, given certain assumptions, the electric engine manufacturer may need to specify cooling limits that cannot be exceeded at the aircraft and engine interface to ensure safe operation.
FAA Response: The FAA does not agree with the comment. These special conditions are applicable only to the magniX magni350 and magni650 model engines. The FAA made no changes to the special condition as a result of the comment.
Comment Summary: Rolls-Royce stated that the cooling system monitoring and documentation requirements in proposed Special Condition no. 6 are already covered in 14 CFR 33.29h, Instrument connection. Rolls-Royce recommended
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that the FAA modify 33.29h to include a statement of applicability to electric engines.
TCCA recommended adding, The cooling system monitoring must be made available to enable the flight crew or the automatic control system to monitor the functioning of the engine cooling system.
FAA Response: The FAA does not agree to amend 14 CFR 33.29h as a result of Rolls-Royces comment, as these special conditions are of particular applicability to the magni350 and magni650 model engines only.
However, as a result of Rolls-Royces and TCCAs comments that recommend applying cooling system monitoring to the magniX engines, the FAA has added paragraph b to final Special Condition no. 11 to incorporate the requirements of 14 CFR 33.29h, except for those provisions specifically applicable to turbine aircraft engines.
Comment Summary: TCCA
recommended adding, If aspects of the engine cooling system require the installer to ensure that the temperature limits are met, those limits must be specified in the installation manual.
FAA Response: The FAA does not agree with TCCAs comment. Special Condition no. 24 requires magniX to establish a temperature limit. If the temperature limit is necessary for the safe operation of the engine, these special conditions require the limit to be documented in the installation manual.
Therefore, a special condition is not needed to mandate information specified in TCCAs comment.
Comment Summary: TCCA
recommended adding, Any reliance placed upon the assumed installed conditions, or installation requirements must be declared in the instructions for installation.
FAA Response: The FAA does not agree with TCCAs comment. Special Condition no. 1 requires magniX to comply with 14 CFR 33.5. Therefore, these special conditions already require the information specified in TCCAs comment to be documented in the instructions for installing the engine.
Comment Summary: TCCA
recommended adding magniX must prepare and make available to the Agency prior to the issuance of the type certificate, and to the installer at the time of delivery of the engine, approved instructions for installing and operating the engine.
FAA Response: The FAA does not agree with TCCAs comment. Special Condition no. 1 requires magniX to comply with 14 CFR 33.4, which requires magniX to prepare Instructions for Continued Airworthiness in
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accordance with appendix A to that part. Appendix A requires the Instructions for Continued Airworthiness include instructions for installing and operating the engine.
Special Condition no. 1 also mandates compliance with 14 CFR 33.5, which requires magniX to prepare and make available to the Administrator, prior to the issuance of the type certificate, and to the owner at the time of delivery of the engine, approved instructions for installing and operating the engine. The FAA made no changes to the special condition as a result of the comment.
Special Condition No. 7, Engine Mounting Attachments and Structure The FAA proposed that Special Condition no. 7 would require these engines to comply with 14 CFR 33.23, which requires the applicant to define the proposed design to withstand certain load limits for the engine mounting attachments and related engine structure. These requirements would otherwise be applicable only to reciprocating and turbine aircraft engines.
Comment Summary: Textron stated that a propeller could be a much higher percentage of the total propulsion system mass in electric systems than for reciprocating or turbine engine propulsion systems and suggested that an electric motors rotating components can be nearly instantly coupled to the non-rotating components due to FOD, internal failure, rotor growth, and commutation errors. Textron proposed additional requirements to Special Condition no. 7 related to sudden stoppage and bearing protection to ensure the engine mounting system can absorb the load or mitigate the effect of the load on aircraft.
FAA Response: The FAA does not agree with the comment. The certification basis for the proposed engines includes 14 CFR 33.23, Engine mounting attachments and structure, which is a performance-based requirement. The regulation doesnt specify how maximum and ultimate loads are determined because these load conditions are determined by magniX.
Also, Special Condition no. 2 requires magniX to establish a torque limit and Special Condition no. 21 requires magniX to establish a maximum overtorque limit. These requirements address the conditions described in Textrons comment. magniXs engines must be designed to accommodate the load at these limit values. These special conditions address high engine mount load conditions, including the conditions described in Textrons comment, except for loads from the
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