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Federal Register / Vol. 86, No. 184 / Monday, September 27, 2021 / Rules and Regulations
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Comment Summary: Textron recommended that the FAA add the following to the end of Special Condition no. 10b, including in failure conditions where the fault or failure results in a change from one control mode to another, from one channel to another, or from the primary system to the back-up system. Textron reasoned that 14 CFR 33.28c addresses failures resulting in changes to the operation of the engine and that regulatory requirements should be applicable to electric engines.
FAA Response: Special Condition no.
10 Engine control systems addresses the potential for all control system failures and failure effects, including failure or malfunction during control system transitions during a rotor overspeed. However, in these final special conditions, the FAA has changed Special Condition no. 10b as a result of this comment to include failure conditions where the fault or failure results in a change from one control mode to another, from one channel to another, or from the primary system to the back-up system, if applicable.
Special Condition No. 11, Instrument Connection The FAA proposed that Special Condition no. 11 would require magniX
to comply with 14 CFR 33.29a, e, f, and g, and, as part of the required system safety assessment, assess the possibility and subsequent effect of incorrect fit of instruments, sensors, or connectors.
Comment Summary: Wisk referred to the statement, In addition, as part of the system safety assessment of Special Condition no. 10g and recommended that the FAA replace the citation in Special Condition no. 11 with reference to Special Condition no. 17 or 14 CFR
33.75a1.
FAA Response: Special Condition no.
10g requires a separate safety assessment for the engine control system. The engine control system safety assessment is not addressed by Special Condition no. 17 or 14 CFR
33.75a1, which requires an enginelevel safety analysis. The engine-level safety analysis does not go into enough detail to address the effects of control system failures and malfunctions. The FAA did not modify this special condition as a result of this comment.
Comment Summary: Textron stated, Special Condition no. 11 mandates compliance with 14 CFR 33.29f, thereby requiring the applicant to assess the possibility and subsequent effects of incorrect fit of instruments, sensors, or connectors. Textron considered this
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requirement to repeat the assessments required by Special Condition no. 10g Engine control systems. For this reason, Textron recommended removing the provisions in Special Condition no.
11 that are adopted by reference to 33.29f.
FAA Response: Special Condition no.
10g corresponds to 33.28e, which requires an engine control systems safety assessment. However, 33.29f requires that, as part of the System Safety Assessment of 33.28e, the applicant must assess the possibility and subsequent effect of incorrect fit of instruments, sensors, or connectors.
Therefore, Special Condition no. 11
does not repeat the requirements in Special Condition 10g. After reviewing Textrons comment, the FAA removed reference to 33.29f because the content of that regulation is captured within Special Condition no. 11a. The FAA made no changes to the special condition as a result of the comment.
Comment Summary: TCCA
recommended that the FAA add a provision requiring that instrument or sensor connections be designed or labeled to ensure a correct connection.
FAA Response: The FAA does not agree with the comment. Special Condition no. 11 applies 14 CFR
33.29a to the magniX engines, so this special condition already requires that the connections meet the criteria specified in TCCAs comment. The FAA
made no changes to the special condition as a result of the comment.
Comment Summary: TCCA
recommended adding the following to Special Condition no. 11: Any instrumentation on which the Safety Analysis see special condition no. 17
depends must be specified and declared mandatory in the engine installation manual.
FAA Response: The certification basis for the proposed engines includes 14
CFR 33.5a6, 33.5c, and Special Condition no. 17c, which encompasses 33.75d and 33.75e. These requirements will achieve the desired results recommended in this comment.
The FAA did not change these special conditions as a result of this comment.
Special Condition No. 12, Stress Analysis 14 CFR 33.62 requires a stress analysis be performed on each turbine engine. The requirement is applicable only to turbine engines and turbine engine components, and therefore, is not appropriate for the magni350 and magni650 Model engines. The FAA
proposed this special condition due to the need for a stress analysis of similar
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components used in these proposed engines.
The FAA proposed that Special Condition no. 12 would require a mechanical, thermal, and electromagnetic stress analysis that showed a sufficient design margin to prevent unacceptable operating characteristics. Also, the condition proposed to require the applicant to determine the maximum stresses in the engine by tests validated analysis, or a combination thereof and show that they do not exceed minimum material properties.
Comment Summary: Wisk asked the FAA to clarify this special condition by declaring the types of failure effects that the special condition addresses. Wisk stated that Special Condition no 12
refers to unacceptable operating characteristics and that this term, coupled with Special Condition no. 9, may leave a gap where no analysis is required for static structural components mounts, casings, etc., which would not affect operating characteristics but could still be hazardous.
FAA Response: The corresponding 14
CFR part 33 airworthiness requirement for this special condition is 33.62
Stress analysis. The corresponding part 33 airworthiness requirement for Special Condition no. 9 Overspeed is 33.27, Turbine, compressor, fan, and turbosupercharger rotor overspeed.
These special conditions are intended to apply similar requirements to the magniX engines but with additional provisions to account for electric engine technology. The additional analysis suggested in Wisks comment is already required by Special Condition no. 13
Critical and life-limited parts. It requires a stress analysis of static engine parts, so no changes were made to this special condition as a result of this comment.
Comment Summary: TCCA
recommended that the FAA require the applicant to provide an analysis of electromagnetic stresses.
FAA Response: The FAA concurs with this comment. The FAA has modified Special Condition no. 11 to require the analysis to assess the impact of electromagnetic interference on stress.
Comment Summary: TCCA
recommended adding, The sufficient design margin must be established in the means of compliance to Special Condition no. 12a.
FAA Response: Design margin is already required by Special Condition no. 12 Stress Analysis, which will require magniX to develop the compliance documents suggested by
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