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Federal Register / Vol. 86, No. 184 / Monday, September 27, 2021 / Rules and Regulations
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change the FAA made to Special Condition no. 10g and the addition to Special Condition no. 17e, which requires magniX to take into account the intended aircraft application in the engine installation manual. The FAA
has changed final Special Condition no.
15b in the manner requested by this comment.
Comment Summary: TCCA
recommended that the special condition should state the power-lever movement interval, and that response times in 14
CFR 33.73 should apply to the magniX
engines, unless magniX substantiates different values for the power-lever movement interval and response times for the aircraft that will use the engines.
TCCA also recommended adapting the existing 33.73 requirement to remove the condition only applicable to the turbine engine, such as surge, stall.
FAA Response: The FAA does not agree with the comment. These special conditions are applicable only to the magniX engines. Special Condition no.
10 Engine control systems and Special Condition no. 17 Safety analysis require magniX to account for the aircraft that can use these engines.
Therefore, the required power-lever movement interval and response times account for the aircraft safety objectives.
Also, Special Condition no. 15 was developed to be a performance-based version of 33.73, so all requirements of 33.73 are not part of the special condition. The FAA did not change these special conditions as a result of this comment.
Special Condition No. 16, Continued Rotation The FAA proposed that Special Condition no. 16 would prohibit any hazardous engine effects to result from the continued rotation of engine rotating systems that the design allows to rotate after the engine is shut down.
Comment Summary: Textron stated that there is potential for electric engines to regenerate electric energy from continuing to freely rotate after the engine is shut down, and recommended an additional requirement to prevent hazardous electrical bus effects.
FAA Response: These special conditions apply only to the subject magniX engines, which are not intended to regenerate or otherwise direct electrical power to the aircraft. The FAA
made no changes to the special condition as a result of the comment.
Special Condition No. 17, Safety Analysis The FAA proposed that Special Condition no. 17 would require magniX
to comply with 14 CFR 33.75a1,
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a2, and a3, which require an applicant to conduct a safety analysis of the engine, and which would otherwise apply only to applications for turbine aircraft engines. Additionally, the proposed special conditions would require magniX to assess its engine design to determine the likely consequences of all failures that can reasonably be expected to occur, and state, in the safety analysis, the failure of such elements and associated prescribed integrity requirements.
As used in Special Condition no. 17, a primary failure is a manner in which a part fails if the engine is installed in the expected aircraft configurations and operated in accordance with operating conditions assumed in the design data such as the expected performance cycles, engine limits, and operating environments, and maintained using the declared instructions for continued airworthiness. A primary failure is not the result of the prior failure of another part or system.
Some engine parts can fail suddenly in their primary failure from prolonged exposure to the physical conditions in a normal engine environment, such as temperature, vibration, and stress. The probability of failure cannot be sensibly estimated in numerical terms, and failure will likely result in a hazardous engine effect. As a result, 14 CFR 33.70, Engine life-limited parts, and 14 CFR
33.75, Safety analysis, do not allow these parts to be managed by oncondition or probabilistic means.
Therefore, requirements such as life limits, scheduled inspections, and inspection techniques are mandated to ensure the essential attributes are preserved throughout the parts service life. For example, if the number of engine cycles to failure is predictable and can be associated with specific design characteristics, such as material properties, then the applicant can manage the engine part with life limits.
The safety analysis requires magniX
to identify hazards that are applicable to the electric technology used in their engine design. All the engine hazards that apply to turbine engines also apply to the magniX electric engines, in addition to possible exceedances of any new engine limits pursuant to Special Condition no. 2 Engine ratings and operating limits to prevent failure of electronic components that have a direct impact on safety.
The outcome of the safety analysis partially depends on the aircraft types that will use these engines. Therefore, final Special Condition nos. 17e and 10g require magniX to account for the intended aircraft application in the engine installation manual to ensure the
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magniX engine is installed only in aircraft with compatible safety assumptions. The term intended aircraft application means the aircraft that are expected to operate with the magniX engines.
Comment Summary: Regarding Special Condition no. 17d3, Wisk recommended that the FAA classify a loss of partial thrust, or a thrust variation of a small amount, as a major effect which should be only considered when the impact is relevant at the aircraft level. Wisk also stated that the applicable 14 CFR part 23, 25, 27, and 29 regulations establish appropriate LOTC/LOPC classifications, so a special condition for 14 CFR 33.75 appears unnecessary. Wisk recommended that Special Condition no. 17d1 use the existing words of 33.75g1, which state, An engine failure in which the only consequence is partial or complete loss of thrust or power and associated engine services from the engine will be regarded as a minor engine effect.
FAA Response: The FAA does not agree with the comment. These special conditions are not generally applicable to electric engines. The requirements only apply to the magniX magni350 and magni650 model electric engines. The safety analysis classifies engine failures, including LOTC/LOPC. The classification LOTC/LOPC events partially depends on the aircraft types that will use these engines, so the existing engine reliability requirements and accepted partial power levels in 14
CFR part 23, 25, 27, and 29 aircraft are not directly applicable without further review of the engine and aircraft capabilities. In addition, Special Condition no. 10f1 requires the LOPC
rate to be suitable for the intended aircraft application; and Special Condition no. 10, including 10f2, requires the Administrator to determine the need for design redundancy relating to LOPC events to ensure the magniX
engine LOPC rate is compatible with the aircraft safety objectives. The FAA made no changes to the special condition as a result of the comment.
Comment Summary: GE directed attention to the integrity requirements listed in Special Condition no. 17b.
The requirement addresses elements engine parts, components, and systems that can fail and are likely to result in hazardous engine effects. GE stated that the integrity requirements in Special Condition no. 17b are not complete and may not achieve a level of safety equivalent to that established in 14 CFR
33.75, Safety analysis, and 33.70, Engine life-limited parts. GE
recommended adding a statement that requires magniX to include any other
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