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Federal Register / Vol. 86, No. 184 / Monday, September 27, 2021 / Rules and Regulations
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rain conditions. No changes were made to this special condition as a result of this comment.
Special Condition No. 19, Liquid Systems The FAA proposed that Special Condition no. 19 would require magniX
to ensure that liquid systems used for lubrication or cooling of engine components are designed and constructed to function properly. Also, the FAA proposed that, if a magniX
engine liquid system is shared with an aircraft liquid system, the interfaces between the engine and aircraft systems must be defined in the engine installation manual.
Comment Summary: Wisk recommended that these special conditions address the risk of a liquid system freezing after an engine shutdown and preserve the ability for engine restart.
FAA Response: These special conditions already account for the concerns expressed by Wisk. Special Condition no. 19 requires magniX to ensure the liquid system operates appropriately in all atmospheric conditions in which the engine is expected to operate. The FAA did not change Special Condition no. 19 as a result of this comment.
Comment Summary: Rolls-Royce noted that the FAA did not propose to require the design to comply with 14
CFR 33.64, Pressurized engine static parts. The commenter stated that it anticipated electric engine configurations with pressurized cooling systems and pressurized lubrication systems and recommended that this requirement be included in these special conditions.
FAA Response: These special conditions are not generally applicable to all electric engines and apply only to these proposed magniX electric engines.
However, magniX may choose to pressurize the liquid systems in their engines. Therefore, the FAA has changed final Special Condition no. 19
to require magniX to account for pressurized static engine parts.
Comment Summary: Textron recommended that these special conditions require that the engine installation manual prescribe the cooling and lubricating fluids used on these engines.
FAA Response: The FAA has modified Special Condition no. 19 in these final special conditions to require magniX to list eligible lubricants and coolants in the engine installation manual.
Comment Summary: Textron recommended that the FAA add a
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requirement that prevents magnetically attracted engine debris from accumulating in passages that could block or limit coolant flow.
FAA Response: The potential for magnetic debris in the magniX engine liquid cooling system would likely be a consequence of an engine failure or inadequate maintenance. If this were a characteristic of the type design, the magniX engines would not likely meet the requirements established in these special conditions, such as Special Condition nos. 5 Durability and 7
Safety Analysis. The FAA did not change Special Condition no. 19 as a result of this comment.
Comment Summary: TCCA noted the possibility that the magniX electric engine liquid system might rely on aircraft systems. In that case, TCCA
recommended that these special conditions require that reliance be declared in the engine installation manual.
FAA Response: Special Condition no.
1 requires magniX to comply with 14
CFR 33.5, Instruction manual for installing and operating the engine. The requirements in 33.5a5 and 33.5c address the safety concern raised in this comment. The FAA did not change Special Condition no. 19 due to this comment.
Special Condition No. 20, Vibration Demonstration The FAA proposed that Special Condition no. 20 would require magniX
to ensure 1 the engine is designed and constructed to function throughout its normal operating range of rotor speeds and engine output power without inducing excessive stress caused by engine vibration, and 2 the engine design undergoes a vibration survey.
Comment Summary: Wisk recommended that the FAA incorporate the requirements from 14 CFR 33.83f, Vibration test, instead of proposed Special Condition no. 20b, when the installation can be assessed by analysis to match an approved engine installation because the existing 14 CFR
part 33 regulation does not appear to require a vibration survey.
FAA Response: This special condition combines the requirements of 33.63, Vibration, and 33.83, Vibration test.
Special Condition no. 20a corresponds to 33.63, Subpart E, which has provisions for the design and construction of the electric engine.
Special Condition no. 20b corresponds to 33.83, Subpart F, which applies to the block tests. This 33.83, Vibration test, reference explains why a vibration survey is specified in Special Condition no. 20b and not in 20a. In addition,
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the special condition requires magniX
engines to undergo a vibration survey using test, validated analysis, or a combination of both. Therefore, this special condition addresses Wisks comment. The FAA did not change this special condition as a result of this comment.
Comment Summary: Ampaire suggested the terminology used in the title of proposed Special Condition no.
20 described a vibration demonstration, and the term used in the ASTM document referred to the requirement as a test ref. ASTM
F333818, section 5.20.4.
FAA Response: A demonstration is a test, but this special condition also allows validated analysis to show compliance. A test is required to validate an analysis, so the requirement is grounded in a test. The FAA did not change this special condition as a result of this comment.
Comment Summary: TCCA stated that paragraph a of proposed Special Condition no. 20 is similar to 14 CFR
33.83b, which has a demonstration element. TCCA asked that the FAA
clarify when to use representative propeller loads during engine testing.
TCCA also recommended the FAA add clarification within Special Condition no. 20 to explain when propeller loads are required during the engine demonstrations.
FAA Response: Special Condition no.
20 has a demonstration element. Special Condition no. 20a corresponds to 14
CFR 33.63 in Subpart E, Design and Construction; Turbine Aircraft Engines, and Special Condition no. 20b corresponds to 33.83 in Subpart F, Block Tests; Turbine Aircraft Engines.
TCCAs comment also relates to Special Condition no. 31, Operation with a variable pitch propeller, which corresponds to 33.95, Engine-propeller systems tests. As a result of TCCAs comment, the FAA modified final Special Condition no. 31 to enable magniX to run their engines with a variable pitch propeller during the operation demonstration.
Comment Summary: TCCA
recommended that the FAA add a requirement for magniX to evaluate the vibration effects from sustained engine unbalance to protect the engine and aircraft from vibration effects caused by engine failures that result in windmilling or propeller pitch or propeller feathering issues. TCCA
recommended adding a paragraph that states, The effects on vibration characteristics of excitation forces caused by fault conditions must be evaluated by test or analysis, or by reference to previous experience and
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