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Federal Register / Vol. 86, No. 184 / Monday, September 27, 2021 / Rules and Regulations needed for the magniX engine design.
Cybersecurity issues are not specific to these magniX engines and will be addressed by other compliance determinations. The FAA made no changes to these special conditions as a result of this comment.
Comment Summary: Wisk stated that the change in wording from 14 CFR
33.28 from Operating limits to Operating limitations could have uncertain impacts, as limits are typically parametric-based and mostly achievable by a control system if so required. Wisk noted that operating limitations are more aligned to what is found in an airplane flight manual, so this expands the scope of what the control system may be expected to do.
FAA Response: The FAA has changed operating limitations to operating limits in Special Condition no. 10b.
Comment Summary: Wisk asked what the FAA meant by be single fault tolerant, as determined by the Administrator in proposed Special Condition no. 10f2.
FAA Response: The term single fault tolerant describes an engine control systems ability to experience single failures and not result in a hazardous engine effect while operating without any fault conditions present and in all dispatchable configurations. Special Condition no. 10f2 requires the engine control system to be single fault tolerant for electrical, electrically detectable, and electronic failures involving LOPC events. The FAA made no changes to these special conditions as a result of this comment.
Comment Summary: Wisk asked that the FAA clarify the meaning of local events as used in proposed Special Condition no. 10f4 Engine control system failures.
FAA Response: The term local events used in Special Condition no.
10f4 means failures or malfunctions that could lead to hazardous effects such as fire, overheat, or failures causing damage to engine control system components. The FAA made no changes to these special conditions as a result of this comment.
Comment Summary: Wisk suggested that the FAA not impose proposed Special Condition no. 10g, System safety assessment. Wisk stated that the condition was unnecessary and could lead to uncertainty because 14 CFR
33.75a, Safety analysis, is more rigorous. Wisk suggested incorporating 33.75a1 into Special Condition no.
10, or linking Special Condition no. 17
to Special Condition no. 10g.
FAA Response: Special Condition no.
17 Safety Analysis, incorporates 14
CFR 33.75a1, which requires the
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applicant to analyze the engine, including the control system, to assess the likely consequences of all failures that can reasonably be expected to occur. Special Condition no. 10, which is adopted as proposed, contains a separate requirement for the engine control, including the frequency of occurrence of faults or failures. The linkage requested by Wisk between the engine safety analysis and control system safety assessment exists in these special conditions. The FAA made no changes to these special conditions as a result of this comment.
Comment Summary: Wisk stated they understood the initial intent of 33.28i around engine controllers being reliant on electrical power for function, whereby fuel was used for the production of useful thrust/power. Wisk commented that by stating the engine control must accommodate any malfunction of the electrical supply forces the engine control to accommodate overvoltage, overcurrent, etc., that may drive unnecessary cost and weight on the engine manufacturer.
Wisk recommended consideration is given to the high-voltage electrical source used for thrust/power generation such that it is treated more like fuel, which is under the control of the airframe OEM.
FAA Response: Special Condition no.
10j does not require the magniX engine controller to accommodate malfunctions of the electrical supply. The special condition requires the engine control system to be designed such that a loss, malfunction, or interruption of the control system electrical power source will not result in hazardous engine effects. However, Special Condition no.
2 requires magniX to establish and declare ratings and operating limits based on power-supply requirements for the engine, which addresses the suggestion proposed by Wisk. The FAA
did not change this special condition as a result of this comment.
Comment Summary: Ampaire asked the FAA to incorporate additional information from ASTM F333818
section 5.10, EPU Controls, into Special Condition no. 10g, system safety assessment, and Special Condition no.
10h, protection systems.
FAA Response: ASTM F333818
contains technical criteria that the FAA
incorporated in these special conditions. It also contains information that the applicant can use to develop a means of compliance to these special conditions. The FAA did not change these special conditions as a result of this comment.
Comment Summary: AIAB proposed that the FAA mandate compliance with
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14 CFR 33.28h2. AIAB stated that the accommodation strategy could depend on the aircraft that use the engines because the aircrafts response to a change to thrust or power will determine if the accommodation strategy is acceptable. AIAB asked that the FAA require the applicant to evaluate the effects of aircraft-supplied data failures and document them in the engine installation manual.
FAA Response: As a result of this and other comments, the FAA modified Special Condition no. 10g by adding, The intended aircraft application must be taken into account to assure the assessment of the engine control system safety is valid. Therefore, the applicants fault accommodation strategies will need to account for the aircrafts capabilities. If the accommodation strategy meets any criteria in 14 CFR 33.5, that regulation will prompt magniX to document the details in the Instruction manual for installing and operating the engine. The FAA has changed the special condition to include additional requirements for aircraft-supplied data consistent with the recommendation.
Comment Summary: An anonymous commenter inquired if these special conditions would address electromagnetic interference potential, which, the commenter states, has caused issues with onboard radios and equipment.
FAA Response: Special Condition no.
10e, Environmental limits, addresses potential engine effects from HIRF and lightning, as well as electromagnetic compatibility between the engine and aircraft systems. This special condition also requires the applicant to document the environmental limits to which the system has been qualified and the electromagnetic emissions from the engine. The FAA made no changes to these special conditions as a result of this comment.
Comment Summary: Textron stated the proposed Special Condition no.
10h matches the requirements of 33.28f1, but the requirements of 33.28f2 and f3 are not included.
Textron also stated there is no obvious reason why the same requirements for overspeed protection would not also apply to an electric engine, so those requirements should be added to the proposed special condition.
FAA Response: These special conditions are applicable only to the magniX magni350 and magni650 model engines. Special condition 10h ensures the magniX operating limits will not be exceeded in-service. The FAA made no changes to these special conditions as a result of this comment.

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