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Federal Register / Vol. 86, No. 184 / Monday, September 27, 2021 / Rules and Regulations
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generating systems. The magniX motor, in both models, is a device that converts electrical energy into mechanical energy by electric current flowing through wire coils in the motor, producing a magnetic field that interacts with magnets on the rotating shaft. The controller is a system that consists of two main functional elements: the motor controller and an electric power inverter to drive the motor.5 The high-voltage system is a combination of wires and connectors that couple the motor and the controller.
In addition, the technology required to produce these high-voltage and highcurrent electronic components introduces potential hazards that do not exist in aircraft engines that operate using aviation fuel. For example, highvoltage transmission lines, electromagnetic fields, magnetic materials, and high-speed electrical switches form the electric engines physical properties. However, this technology also exposes the aircraft to potential failures that are not common to aircraft engines that operate using aviation fuel, which could adversely affect safety.
magniXs Electric Engines Require a Mix of 14 CFR Part 33 Standards and Special Conditions Although magniXs proposed electric engines incorporate a novel or unusual design feature that the FAA did not envisage during the development of its existing 14 CFR part 33 airworthiness standards, these engines share some basic similarities, in configuration and function, to engines that use the combustion of fuel and air, and therefore they require similar provisions to prevent common hazards e.g., fire, uncontained high-energy debris, and loss of thrust control. However, the primary failure concerns and the probability of exposure to common hazards are different for the electric engines. This probability creates a need to develop special conditions to ensure the engines safety and reliability.
14 CFR part 33 does not fully address aircraft engines like magniXs, which use electrical technology as the primary means of propelling the aircraft. This necessitates the development of special conditions to provide adequate airworthiness standards for these aircraft engines.
The requirements in 14 CFR part 33, subparts B through G, apply to aircraft engines that operate using aviation fuel.
Subpart B applies to reciprocating and turbine aircraft engines. Subparts C and 5 Sometimes this entire system is referred to as an inverter. Throughout this document, the controller and inverter will be referred to as the controller.

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D apply to reciprocating aircraft engines. Subparts E through G apply to turbine aircraft engines. As such, subparts B through G do not adequately address aircraft engines that operate using electrical technology. This necessitates the development of special conditions to ensure a level of safety commensurate with these subparts, as those regulatory requirements do not contain adequate or appropriate safety standards for aircraft engines that primarily use electrical technology to propel the aircraft.
Discussion of Special Conditions and Comments The FAA issued Notice of Proposed Special Conditions No. 331901SC
the Notice for these proposed engines.
This document was published in the Federal Register on November 19, 2020
85 FR 73644. The FAA received comments from eleven organizations and two individuals.
The organizations that commented were Wisk Aero Wisk, Rolls-Royce North America Rolls-Royce, GE
Aviation GE, Ampaire Inc. Ampaire, Textron Aviation Textron, Associacao Das Industrias Aeroespaciais Do Brasil AIAB, Safran Electrical & Power Safran, Airbus Commercial Aircraft Airbus, magniX USA, Inc. magniX, Transport Canada Civil Aviation TCCA, and European Union Aviation Safety Agency EASA.
The following summarizes each special condition proposed by the FAA;
the pertinent comments, and the FAAs response, including whether the FAA
made any changes in these final special conditions.
Special Condition No. 1, Applicability The FAA proposed that Special Condition no. 1 would require magniX
to comply with 14 CFR part 33, except for those airworthiness standards specifically and explicitly applicable only to reciprocating and turbine aircraft engines.
Comment Summary: TCCA
commented that proposed Special Condition no. 1 could be read in different ways regarding which sections of 14 CFR part 33 apply directly to electric engines and that applicants might disagree when assessing the appropriate airworthiness requirements for their engine designs. TCCA also suggested a manner in which to reformat this special condition.
FAA Response: These special conditions are not intended for all electric engine projects, only for the two models of engine proposed by magniX.
Addressing the 14 CFR, part 33
applicability portion of the comment,
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the requirements in part 33, subpart B, are applicable to reciprocating and turbine aircraft engines. Subparts C and D are applicable to reciprocating aircraft engines. Subparts E through G are applicable to turbine aircraft engines. As the magni350 and magni650 model engines are not reciprocating or turbine engines, subparts B through G of part 33
are not applicable to these engines unless these special conditions expressly require compliance, as set forth herein. The FAA did not change the special condition as a result of this comment.
Comment Summary: TCCA requested that Special Condition no. 1 include an additional requirement. TCCA asked that the FAA require the applicant to specify, within the engine installation manual, the electrical bonding for the installation of the engine and its control system. TCCA explained that proper bonding is required to protect the engine and the control system from the effects of lightning and electrostatic electricity, noting that 14 CFR 33.5a does not explicitly require electrical bonding instructions to be included in the engine installation manual.
FAA Response: Special Condition no.
10e addresses environmental limits for the magniX engines, which include electromagnetic interference, highintensity radiated fields, and lightning.
The assessments that verify environmental limits account for the effects of electrical bonding. A special condition for electrical bonding is not required to establish proper electrical bonding. Special Condition no. 1
mandates compliance with 33.5a, which addresses all physical and functional interfaces with the aircraft, including TCCAs recommendation to specify electrical bonding details in the engine installation instructions. The FAA made no changes to the special condition as a result of this comment.
Comment Summary: Wisk stated the inclusion of the high voltage and high current electrical system within the system covered by the engine OEM
introduces aspects of 14 CFR 23.2525
that have not typically been addressed by engine OEMs before. Wisk added that consideration within the proposed SC
for these aspects would ensure a safer product during the development, flight test, and service lifecycle. Wisk proposed the FAA consider applying 23.2525a and b, and possibly other relevant regulations to the components between the controller and motor in the engine system.
FAA Response: The requirements Wisk identifies in their comment apply to system power generation, storage, and distribution. These special conditions
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