Document ID: FAA-2020-0894-0015
Agency: faa
Document Type: Rule
Title: Special Conditions: magniX USA, Inc., magni350 and magni650 Model Engines; Electric Engine Airworthiness Standards
Posted Date: 2021-09-27T04:00Z

[Federal Register Volume 86, Number 184 (Monday, September 27, 2021)]
[Rules and Regulations]
[Pages 53508-53534]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2021-19926]

[[Page 53507]]

Vol. 86

Monday,

No. 184

September 27, 2021

Part III

 Department of Transportation

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Federal Aviation Administration

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14 CFR Part 33

Special Conditions: magniX USA, Inc., magni350 and magni650 Model 
Engines; Electric Engine Airworthiness Standards; Final Rule

  Federal Register / Vol. 86, No. 184 / Monday, September 27, 2021 / 
Rules and Regulations  

[[Page 53508]]

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DEPARTMENT OF TRANSPORTATION

Federal Aviation Administration

14 CFR Part 33

[Docket No. FAA-2020-0894; Special Conditions No. 33-022-SC]

Special Conditions: magniX USA, Inc., magni350 and magni650 Model 
Engines; Electric Engine Airworthiness Standards

AGENCY: Federal Aviation Administration (FAA), DOT.

ACTION: Final special conditions.

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SUMMARY: These special conditions are issued for the magniX USA, Inc., 
(magniX), magni350 and magni650 model engines, which operate using 
electrical technology installed on the aircraft for use as an aircraft 
engine. These engines have a novel or unusual design feature when 
compared to the state of technology envisioned in the airworthiness 
standards applicable to aircraft engines. This design feature is an 
electric motor, controller, and high-voltage systems as the primary 
source of propulsion for an aircraft. The applicable airworthiness 
regulations do not contain adequate or appropriate safety standards for 
this design feature. These special conditions contain the additional 
safety standards that the Administrator considers necessary to 
establish a level of safety equivalent to that established by the 
existing airworthiness standards.

DATES: Effective October 27, 2021.

FOR FURTHER INFORMATION CONTACT: Mark Bouyer, AIR-624, Propulsion and 
Energy, Technical Innovation Policy Branch, Aircraft Certification 
Service, 1200 District Avenue, Burlington, Massachusetts 01803; 
telephone (781) 238-7755; mark.bouyer@faa.gov.

SUPPLEMENTARY INFORMATION:

Background

    On April 18, 2019,\1\ magniX applied for a type certificate for its 
magni350 and magni650 model electric engines.\2\ The FAA has not 
previously type certificated an engine that primarily uses electrical 
technology for propulsion of the aircraft. Electric propulsion 
technology is substantially different from the technology used in 
previously certificated aircraft engines that operate using aviation 
fuel; therefore, these engines introduce new safety concerns that need 
to be addressed in the certification basis.
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    \1\ The Notice of Proposed Special Conditions, published on 
November 19, 2020 (85 FR 73644), inaccurately indicated June 4, 
2019, as magniX's type certificate application date.
    \2\ magniX submitted a comment which notified the FAA that the 
magniX engine model numbers were changed from magni250 and magni500 
to magni350 and magni650, respectively. The model number change does 
not represent a change in the certification requirements of the 
engine.
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    As noted in the Notice of Proposed Special Conditions, the FAA used 
technical criteria from ASTM F3338-18, Standard Specification for 
Design of Electric Propulsion Units for General Aviation Aircraft,\3\ 
along with engine information from magniX and other information, to 
develop these special conditions. These special conditions establish a 
level of safety that is equivalent to the level of safety required by 
title 14, Code of Federal Regulations (14 CFR) part 33.
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    \3\ https://www.astm.org/DATABASE.CART/HISTORICAL/F3338-18.htm.
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Type Certification Basis

    Under the provisions of 14 CFR 21.17(a)(1), generally, magniX must 
show that magni350 and magni650 model engines meet the applicable 
provisions of 14 CFR part 33 in effect on the date of application for a 
type certificate.
    If the Administrator finds that the applicable airworthiness 
regulations (e.g., 14 CFR part 33) do not contain adequate or 
appropriate safety standards for the magni350 and magni650 model 
engines because of a novel or unusual design feature, special 
conditions may be prescribed under the provisions of Sec.  21.16.
    Special conditions are initially applicable to the model for which 
they are issued. Should the type certificate for that model be amended 
later to include any other engine model that incorporates the same 
novel or unusual design feature, these special conditions would also 
apply to the other engine model under Sec.  21.101. The FAA issues 
special conditions, as defined in 14 CFR 11.19, in accordance with 
Sec.  11.38, and they become part of the type certification basis under 
Sec.  21.17(a)(2).

Novel or Unusual Design Feature

    The magni350 and magni650 model engines will incorporate the 
following novel or unusual design feature:
    An electric motor, controller, and high-voltage systems is used as 
the primary source of propulsion for an aircraft.

Discussion

14 CFR Part 33 Developed for Aircraft Engines That Operate Using 
Aviation Fuel

    Aircraft engines make use of an energy source to drive mechanical 
systems that provide propulsion for the aircraft. The turbine and 
reciprocating aircraft engines certified under part 33 use aviation 
fuel as an energy source. The technology that the FAA anticipated in 
the development of 14 CFR part 33 converts oxygen and fuel to generate 
energy through an internal combustion system, which generates heat and 
mass flow of combustion products for turning shafts attached to 
propulsion devices such as propellers and ducted fans. Part 33 
regulations set forth standards for these engines and mitigate 
potential hazards resulting from failures and malfunctions. The nature, 
progression, and severity of engine failures are tied closely to the 
technology that engine manufacturers use in designing and manufacturing 
aircraft engines. These technologies involve chemical, thermal, and 
mechanical systems. Therefore, the existing engine regulations in 14 
CFR part 33 address certain chemical, thermal, and mechanically induced 
failures specific to air and fuel combustion systems operating with 
cyclically loaded high-speed, high-temperature, highly-stressed 
components.

magniX's Electric Engines Are Novel or Unusual

    The FAA's current airworthiness standards for aircraft engines, 14 
CFR part 33, date back to 1964.\4\ The FAA based these airworthiness 
standards on aircraft engines that operate using aviation fuel; such 
engines have mechanical systems that provide propulsion for aircraft. 
However, the magniX magni350 and magni650 model engines have a novel or 
unusual design feature which uses an electrical energy source instead 
of aviation fuel to drive the mechanical systems. The electric engine 
is exposed to chemical, thermal, and mechanical operating conditions 
that are unlike those observed in internal-combustion systems. 
Therefore, 14 CFR part 33 does not contain adequate safety standards 
for the magniX magni350 and magni650 model engines' novel or unusual 
design feature.
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    \4\ 29 FR 7452.
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    The two models of electric engine that have been proposed by magniX 
will use electrical power instead of air and fuel combustion to propel 
the aircraft. These electric engines will be designed, manufactured, 
and controlled differently than aircraft engines that operate using 
aviation fuel. They will be built with an electric motor, controller, 
and high-voltage systems that draw energy from electrical storage or

[[Page 53509]]

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.
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    \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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    In addition, the technology required to produce these high-voltage 
and high-current electronic components introduces potential hazards 
that do not exist in aircraft engines that operate using aviation fuel. 
For example, high-voltage transmission lines, electromagnetic fields, 
magnetic materials, and high-speed electrical switches form the 
electric engine's 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.

magniX's Electric Engines Require a Mix of 14 CFR Part 33 Standards and 
Special Conditions

    Although magniX's 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 
engine's safety and reliability.
    14 CFR part 33 does not fully address aircraft engines like 
magniX's, 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 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. 33-19-01-
SC (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 FAA's 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, 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 33.5(a) does not 
explicitly require electrical bonding instructions to be included in 
the engine installation manual.
    FAA Response: Special Condition no. 10(e) addresses environmental 
limits for the magniX engines, which include electromagnetic 
interference, high-intensity 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 Sec.  33.5(a), which addresses all physical 
and functional interfaces with the aircraft, including TCCA's 
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 Sec.  23.2525(a) 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

[[Page 53510]]

apply only to the magniX engine designs, which do not include the power 
systems addressed in 14 CFR 23.2525. These power systems are normally 
approved as part of the airplane. Therefore, any other relevant part 23 
airplane requirements would also be addressed during the airplane 
certification program. The FAA did not change this special condition as 
a result of this comment.
    Comment Summary: Wisk acknowledged that the high voltage and 
current electrical system is analogous to the traditional fuel system. 
As such, omitting regulations that are equivalent to all, or parts of 
14 CFR 33.67 from these special conditions may result in a loss of a 
critical interface boundary, resulting in a lack of clear ownership 
between the airframe and engine OEM. Wisk requested that the FAA 
clarify within the proposed SC the analogous aspects of Sec.  33.67 for 
the interface between the engine controller and the airframe electrical 
system as it relates to voltage and current.
    FAA Response: 14 CFR 33.67 includes requirements for features that 
do not exist in the magniX engine electrical system. However, the 
analogous aspects of Sec.  33.67 are included Special Condition no. 2, 
which requires magniX to establish and declare ratings and operating 
limits based on power-supply requirements for the engine. Therefore, 
Special Condition no. 2 addresses Wisk's comment. The FAA did not 
change this special condition as a result of this comment.

Special Condition No. 2, Engine Ratings and Operating Limits

    The FAA proposed that Special Condition no. 2 would require magniX, 
in addition to compliance with 14 CFR 33.7(a), to establish engine 
operating limits related to the shaft horsepower, torque, speed, and 
duty cycle(s). The duty cycle is an engine rating that declares a 
performance capability for the load(s) that will be imposed on the 
engine, including, if applicable, starting, no-load and rest, and de-
energized periods, including their durations or cycles and sequence in 
time.
    Comment Summary: Wisk recommended that the FAA expand the ratings 
and operating limits required by Special Condition no. 2 to include 
maximum temperature, maximum and minimum voltage, current, and power; 
and, if applicable, coolant and/or lubrication temperatures & pressures 
for safe operation.
    FAA Response: It is not necessary to impose voltage and current 
limits to ensure that these magniX engines achieve the same level of 
safety intended by 14 CFR part 33. The FAA has changed final Special 
Condition no. 2 to add temperature and power (power-supply) 
requirements to the engine ratings and operating limits.
    Comment Summary: Wisk stated that proposed Special Condition no. 
2(a)(1) (Rated Maximum Continuous Power) should not have a time limit 
as it is continuous. Wisk suggested deleting the word ``time'' from 
proposed Special Condition no. 2(a).
    FAA Response: The FAA agrees that the power at the ``Rated Maximum 
Continuous Power'' rating is not time limited. The FAA has modified 
final Special Condition no. 2 to remove the time constraint from the 
rating.
    Comment Summary: Wisk suggested that the FAA specify coolant and 
lubrication temperatures and pressures for safe operation.
    FAA Response: The FAA does not agree with Wisk's suggestion. A 
special condition is not required for coolant and lubrication 
(operating) temperatures. Special Condition nos. 6 (Engine cooling) and 
14 (Lubrication system) address Wisk's suggestion. No changes were made 
to this special condition as a result of Wisk's comment.
    Comment Summary: Rolls-Royce commented that, by placing a duty 
cycle on the engine's type certificate data sheet, proposed Special 
Condition no. 2 would be overly prescriptive when compared to the FAA's 
requirements for aircraft engines that operate using aviation fuel. 
Rolls-Royce stated that Special Condition no. 2(b) should be removed, 
and the FAA should require the applicant to define a duty cycle in the 
Airworthiness Limitations Section of the Operating Manual.
    FAA Response: The magni350 and magni650 electric engines have 
different operating characteristics than conventional reciprocating or 
turbine engines. The performance capability of electric engine designs 
is defined, in part, by a duty cycle. Therefore the FAA did not change 
this special condition as a result of this comment.
    Comment Summary: GE recommended that the FAA modify Special 
Condition no. 2 to require the applicant to list the engine's cooling 
fluid as an engine operating limitation, similar to 14 CFR 33.7(b)(3), 
which requires, for reciprocating engines, established ratings and 
operating limitations related to oil grade or specification.
    FAA Response: The FAA agrees with the comment and has modified 
final Special Condition no. 2 to require a cooling fluid grade or 
specification as an operating limit.
    Comment Summary: Ampaire commented that the term ``power,'' as used 
in proposed Special Condition no. 2, is not the most relevant metric 
for electric machinery and power electronics. Ampaire stated that it 
understood ``power,'' as used in that condition, to be the electrical 
power output delivered by the magniX engine. Ampaire recommended that 
the FAA change the requirement to specify current and voltage.
    FAA Response: The FAA does not agree with the comment. As used in 
Special Condition no. 2, ``power'' describes the mechanical shaft 
horsepower supplied by the engine to propel the aircraft and not the 
electrical power delivered by the engine. The FAA made no changes to 
the special condition as a result of the comment.
    Comment Summary: Ampaire asked that the FAA include more details 
from ASTM F3338-18, such as those listed in sections 5.3.1-5.3.8, EPU 
Operating Limitations and Ratings, in Special Condition no. 2.
    FAA Response: The FAA does not agree with the comment. ASTM F3338-
18 contains technical criteria that the FAA used in developing these 
special conditions. The airworthiness requirements for these engines 
include paragraphs from the ASTM specification and from 14 CFR part 33. 
The FAA made no changes to the special condition as a result of this 
comment.
    Comment Summary: Textron recommended that the FAA add engine 
temperature to the ratings and operating limits mandated by Special 
Condition no. 2.
    FAA Response: The FAA agrees with the comment. The FAA has changed 
final Special Condition no. 2 to add temperature to the engine ratings 
and operating limits.
    Comment Summary: Textron stated the term ``speed,'' as used in 
Special Condition no. 2(a), could be misleading and mistaken for 
aircraft speed or gearbox output-shaft speed. Textron stated the term 
``speed'' should instead be ``RPM.''
    FAA Response: The FAA does not agree with the comment. Engine speed 
is typically measured in units that describe a rate of mechanical 
rotation. In Special Condition no. 2, the word ``speed,'' used in the 
context of ``rotational speed,'' applies to the output-shaft rotation 
rate. The applicant can express engine speed using various units, so 
the measurement unit of the engine shaft rotation does not need to be 
prescribed in Special Condition no. 2. The FAA did not change the 
special condition based on the comment.

[[Page 53511]]

    Comment Summary: Textron recommended that the FAA add rated takeoff 
power to the required engine ratings and operating limits in Special 
Condition no. 2.
    FAA Response: The FAA agrees and has added ``rated takeoff power'' 
to the engine ratings and operating limits in final Special Condition 
no. 2.
    Comment Summary: TCCA suggested that the engine ratings and 
operating limits not be limited to those proposed in Special Condition 
no. 2(a). TCCA recommended adding a statement that requires magniX to 
include any other ratings or limitations that are necessary for the 
safe operation of the engine.
    FAA Response: The engine ratings and operating limits that Special 
Condition no. 2 requires are based on existing aircraft engine 
technologies. However, electric engine technology is new to aviation. 
The FAA has modified Special Condition no. 2 to require additional 
ratings if they are determined to be necessary for the safe operation 
of the engine.
    Comment Summary: TCCA asked why the FAA did not mandate that the 
applicant comply with 14 CFR 33.7(d) within Special Condition no. 2. 
Similarly, AIAB commented that Special Condition no. 2 should mandate 
compliance with 14 CFR 33.7(d), since the electric motor can be 
affected by the accuracy of the engine control system and 
instrumentation.
    FAA Response: The FAA does not agree with the comment. Special 
Condition no. 1 requires that the proposed design complies with 
Sec. Sec.  33.7(a), 33.7(d), as those requirements are not expressly 
and explicitly applicable only to reciprocating and turbine engines. 
The FAA did not change Special Condition no. 2 as a result of these 
comments.
    Comment Summary: TCCA stated that Special Condition no. 2, as 
proposed, provided requirements ``in addition to Sec.  33.7(a),'' and 
then proceeds to replace all of the Sec.  33.7 details with Special 
Condition no. 2 requirements. TCCA stated the replacement of Sec.  33.7 
with Special Condition no. 2, as proposed, removes the determination by 
the FAA, as well as the concept of ``any other information found 
necessary for the safe operation of the engine.'' TCCA indicated that 
Sec.  33.7, combined with Sec.  33.8, should be referenced in the 
special condition to provide the essential cornerstone for establishing 
aircraft performance based on installed rated power.
    FAA Response: The FAA does not agree with the comment. Special 
Condition no. 1 requires that the proposed design complies with 
Sec. Sec.  33.7(a), 33.7(d), and 33.8. Special Condition no. 2 provides 
requirements in addition to those in Sec.  33.7(a). The concern stated 
by TCCA is remedied by the inclusion of Sec. Sec.  33.7(a), 33.7(d), 
and 33.8 within Special Condition no. 1. No change was made to this 
special condition as a result of the comment.
    Comment Summary: Regarding the reference to ``duty cycle'' in 
proposed Special Condition no. 2(b), and the rating (singular) at that 
duty cycle, TCCA recommended that the FAA clarify whether the duty 
cycle corresponds to a flight cycle, a series of flights, or an engine 
test cycle.
    FAA Response: The term duty cycle in Special Condition no. 2 is an 
engine rating that declares a performance capability for the load(s) 
that will be imposed on the magniX engines. These capabilities are 
determined by tests that may include starting, no-load and rest, de-
energized periods and their durations (or cycles), and sequence. The 
FAA made no changes to the special condition as a result of the 
comment.
    Comment Summary: TCCA commented that proposed Special Condition no. 
2 omitted consideration of electric engines' capability to regenerate 
electrical power. TCCA recommended that the special conditions provide 
design, construction, and testing that demonstrate this new capability, 
while acknowledging that this issue is partially addressed by Special 
Condition no. 31 (Operation with a variable pitch propeller).
    FAA Response: Although electric engines are capable of regenerating 
electrical power, these special conditions apply only to the magniX 
engine designs, which are not intended to provide electrical power to 
an aircraft. Therefore the FAA did not change these special conditions 
as a result of this comment.
    Comment Summary: TCCA suggested that the Special Condition no. 10 
should be modified to include the following: ``If any electrical power 
is supplied from the aircraft to the engine control system for powering 
on and operating the engine, the need for and the characteristics of 
this electrical power, including transient and steady-state voltage 
limits, must be identified and declared in the engine installation 
manual.''
    FAA Response: The FAA modified Special Condition no. 2 as a result 
of Wisk's comment and TCCA's comment for Special Condition no. 10. The 
change requires the applicant to establish ratings and operating limits 
for power-supply requirements, which include voltage and current, to be 
included in the type certificate data sheet.
    Comment Summary: TCCA stated that Special Condition nos. 2(a)(1) 
and 2(a)(2) address power and time limits and asked if the limits are 
based on an expected power supply and whether the power supply will be 
part of the baseline configuration. TCCA recommended including another 
special condition explaining how the power-supply characteristics will 
be addressed in the declaration of power ratings and operational 
limits.
    FAA Response: The term ``power,'' as used in Special Condition nos. 
2(a)(1) and 2(a)(2), refers to engine shaft horsepower. Special 
Condition no. 2 has been modified to include the terms ``shaft power'' 
and ``rated takeoff power.''
    Comment Summary: TCCA suggested that the FAA modify Special 
Condition no. 2 to require the propeller overspeed limit to be defined 
in the engine installation manual for situations involving propeller 
control malfunctions. TCCA recommended that the FAA add a special 
condition that requires a ``get-home'' capability.
    FAA Response: The FAA does not agree with the comment. The 
propeller has its own type certificate, documented ratings, and 
operating limits, including an overspeed limit. These engines will also 
have their own ratings and operating limits, including an overspeed 
limit. Propeller overspeed protection will be managed using the engine 
and propeller installation manuals' declared ratings and operating 
limits. The FAA made no changes to the special condition as a result of 
the comment.
    Comment Summary: TCCA recommended incorporating the following text 
to the special conditions: ``Each selected rating must be for the 
lowest power that all engines of the same type may produce under the 
conditions used to determine that rating at all times between overhaul 
periods or other maintenance.''
    FAA Response: Special Condition no. 1 includes a requirement for 
magniX to comply with 14 CFR 33.8, so the existing requirement in part 
33 is applicable to these engines. Special Condition no. 29 (Teardown 
inspection) requires the engine to be within service limits and 
eligible for continued operation in accordance with the information 
submitted for showing compliance with Sec.  33.4, Instructions for 
Continued Airworthiness. Therefore, these special conditions address 
the recommendation by TCCA. The FAA made no changes to the special 
condition as a result of the comment.

[[Page 53512]]

Special Condition No. 3, Materials

    The FAA proposed that Special Condition no. 3 would require the 
design of these engines to comply with 14 CFR 33.15, which sets 
requirements for the suitability and durability of materials used in 
the engine, and which would otherwise be applicable only to 
reciprocating and turbine aircraft engines.
    Comment Summary: Textron highlighted the potential hazards from 
certain electronic components, such as aging electrolytic capacitors. 
Textron recommended that the FAA require periodic testing of 
electrolytic capacitors to determine an appropriate replacement 
interval to avoid hazardous effects at altitude such as breakdown, 
corona, flashover, creep, strike distance, and cooling.
    FAA Response: These special conditions address the hazards that may 
result from failure or malfunction of electronic components. Special 
Condition no. 27 (System and component tests) is a performance-based 
requirement in which the applicant must show that systems and 
components will perform their intended functions in all declared 
environmental and operating conditions. This requirement addresses all 
types of component failures, including those referenced in Textron's 
comment. Special Condition no. 13 (Critical and life-limited parts) 
requires the applicant to show, by a safety analysis or means 
acceptable to the Administrator, whether rotating or moving components, 
bearings, shafts, static parts, and non-redundant mount components 
should be classified, designed, manufactured, and managed throughout 
their service life as critical or life-limited parts, including 
electronic parts and components. Special Condition no. 10(g) (Engine 
control systems) requires the applicant to conduct a control system 
safety assessment to identify the hazards resulting from control system 
failures and malfunctions, such as those in Textron's comment. The FAA 
made no changes to these special conditions as a result of this 
comment.
    Comment Summary: TCCA recommended that these special conditions 
address the potential for manufacturing errors by appending the 
following text: ``In addition, manufacturing methods and processes must 
be such as to produce sound structure and mechanisms, and electrical 
systems that retain the design properties under assumed service 
conditions declared in the engine installation manual. This includes 
the effects of deterioration over time, e.g., corrosion.''
    FAA Response: The 14 CFR part 33 airworthiness requirement for 
materials (Sec.  33.15) applies to these engines. The existing part 33 
materials requirement is adequate and appropriate for the certification 
basis for these engines. The FAA made no changes to the special 
condition as a result of the comment.

Special Condition No. 4, Fire Protection

    The FAA proposed that Special Condition no. 4 would require the 
design of these engines to comply with 14 CFR 33.17, which sets 
requirements to protect the engine and certain parts and components of 
the airplane against fire, and which would otherwise be applicable only 
to reciprocating and turbine aircraft engines. Additionally, this 
special condition proposed to require magniX to ensure the high-voltage 
electrical wiring interconnect systems that connect the controller to 
the motor are protected against arc faults. An arc fault is a high 
power discharge of electricity between two or more conductors. This 
discharge generates heat, which can break down the wire's insulation 
and trigger an electrical fire. Arc faults can range in power from a 
few amps to thousands of amps and are highly variable in strength and 
duration.
    Comment Summary: GE proposed that the special conditions include a 
provision for non-protected electrical wiring interconnects that 
requires the applicant to conduct an analysis to show that arc faults 
do not cause hazardous engine effects. GE stated that if electrical 
wiring interfaces with aircraft parts or components, the potential for 
arc faults should be communicated to the aircraft manufacturer. In 
addition, GE recommended that the FAA require the applicant to declare 
potential arc faults in the engine installation manual.
    FAA Response: This special condition has provisions to prevent arc 
faults in high-voltage wire interconnecting systems from causing 
hazardous engine effects. Additionally, Special Condition no. 17 
(Safety analysis) will have the effect of requiring magniX to account 
for the intended aircraft application in the engine installation 
manual. 14 CFR 33.5(c), ``Instruction manual for installing and 
operating the engine,'' applies to the two magniX engines. These 
requirements will generate the recommended documentation, such as 
installation instructions. The FAA made no changes to the special 
condition as a result of the comment.
    Comment Summary: TCCA stated that no special conditions provide 
standards for the electrical connectors supplied with the motor. TCCA 
requested clarification of the FAA's intent.
    FAA Response: The special condition is a performance-based 
requirement, which allows flexibility for magniX to design and 
substantiate components (such as connectors) that they use in their 
engine design. The FAA made no changes to the special condition as a 
result of the comment.

Special Condition No. 5, Durability

    The FAA proposed that Special Condition no. 5 would require the 
engine design and construction to ensure safe engine operation between 
maintenance intervals, overhaul periods, and mandatory actions 
described in the applicable ICA.
    Comment Summary: Textron noted that the proposed wording of Special 
Condition no. 5 matched the intent of 14 CFR 33.19(a) but omitted the 
requirements of Sec.  33.19(b). Textron suggested that Special 
Condition no. 5 include the following: ``Each component of the 
propeller-blade pitch control system which is part of the engine type 
design must meet the requirements of Sec. Sec.  35.21, 35.23, 35.42 and 
35.43.''
    TCCA provided a similar comment, asking why Sec.  33.19(b) was 
omitted and seeking its inclusion in Special Condition no. 5.
    FAA Response: These special conditions apply only to the two magniX 
engine designs, which do not include a propeller-blade pitch control 
system. The FAA made no changes to the special condition as a result of 
the comments.
    Comment Summary: TCCA recommended that the FAA include the 
requirements from 14 CFR 33.5(b) into these special conditions, as the 
controller may include propeller control functions.
    FAA Response: These special conditions apply only to the proposed 
magniX engine designs, which do not include propeller controls and 
controllers. In addition, Special Condition no. 1 mandates compliance 
with Sec.  33.5(b), Instruction manual for installing and operating the 
engine, which addresses this comment. The FAA made no changes to the 
special condition as a result of the comment.
    Comment Summary: TCCA stated the requirements from 14 CFR 33.4 are 
missing from these special conditions, but noted that including all 
instructions for off-wing maintenance that were contained in the ICA, 
would not be appropriate.
    FAA Response: These special conditions are not intended for all 
electric engine certification projects. As

[[Page 53513]]

provided in Special Condition no. 1, Sec.  33.4, Instructions for 
continued airworthiness, and its appendix, apply to the magniX engines. 
The FAA made no changes to the special condition as a result of the 
comment.

Special Condition No. 6, Engine Cooling

    The FAA proposed that Special Condition no. 6 would require the 
engine design and construction to comply with 14 CFR 33.21. That 
regulation requires the engine design and construction to provide 
necessary cooling under conditions in which the airplane is expected to 
operate and would otherwise be applicable only to reciprocating and 
turbine aircraft engines. Additionally, this special condition proposed 
to require the applicant to document the cooling system monitoring 
features and usage in the engine installation manual, if cooling is 
required to satisfy the safety analysis described in Special Condition 
no. 17. Loss of adequate cooling to an engine that operates using 
electrical technology can result in rapid overheating and abrupt engine 
failure with critical consequences to safety.
    Comment Summary: GE suggested that Special Condition no. 6 is 
redundant to Special Condition no. 17 (Safety analysis) because it 
includes 14 CFR 33.75(d) Safety analysis, and should be deleted.
    FAA Response: The FAA does not agree with the suggested change. The 
reference to Sec.  33.75(d) in Special Condition no. 17 does not 
explicitly address cooling systems that are necessary for the engine to 
comply with the safety analysis. Special Condition no. 6 requires 
additional information about the cooling system that is not specified 
in Sec.  33.75(d). The FAA made no change to Special Condition no. 6 as 
a result of this comment.
    Comment Summary: Ampaire suggested that, given certain assumptions, 
the electric engine manufacturer may need to specify cooling limits 
that cannot be exceeded at the aircraft and engine interface to ensure 
safe operation.
    FAA Response: The FAA does not agree with the comment. These 
special conditions are applicable only to the magniX magni350 and 
magni650 model engines. The FAA made no changes to the special 
condition as a result of the comment.
    Comment Summary: Rolls-Royce stated that the cooling system 
monitoring and documentation requirements in proposed Special Condition 
no. 6 are already covered in 14 CFR 33.29(h), ``Instrument 
connection.'' Rolls-Royce recommended that the FAA modify Sec.  
33.29(h) to include a statement of applicability to electric engines.
    TCCA recommended adding, ``The cooling system monitoring must be 
made available to enable the flight crew or the automatic control 
system to monitor the functioning of the engine cooling system.''
    FAA Response: The FAA does not agree to amend 14 CFR 33.29(h) as a 
result of Rolls-Royce's comment, as these special conditions are of 
particular applicability to the magni350 and magni650 model engines 
only. However, as a result of Rolls-Royce's and TCCA's comments that 
recommend applying cooling system monitoring to the magniX engines, the 
FAA has added paragraph (b) to final Special Condition no. 11 to 
incorporate the requirements of 14 CFR 33.29(h), except for those 
provisions specifically applicable to turbine aircraft engines.
    Comment Summary: TCCA recommended adding, ``If aspects of the 
engine cooling system require the installer to ensure that the 
temperature limits are met, those limits must be specified in the 
installation manual.''
    FAA Response: The FAA does not agree with TCCA's comment. Special 
Condition no. 24 requires magniX to establish a temperature limit. If 
the temperature limit is necessary for the safe operation of the 
engine, these special conditions require the limit to be documented in 
the installation manual. Therefore, a special condition is not needed 
to mandate information specified in TCCA's comment.
    Comment Summary: TCCA recommended adding, ``Any reliance placed 
upon the assumed installed conditions, or installation requirements 
must be declared in the instructions for installation.''
    FAA Response: The FAA does not agree with TCCA's comment. Special 
Condition no. 1 requires magniX to comply with 14 CFR 33.5. Therefore, 
these special conditions already require the information specified in 
TCCA's comment to be documented in the instructions for installing the 
engine.
    Comment Summary: TCCA recommended adding ``magniX must prepare and 
make available to the Agency prior to the issuance of the type 
certificate, and to the installer at the time of delivery of the 
engine, approved instructions for installing and operating the 
engine.''
    FAA Response: The FAA does not agree with TCCA's comment. Special 
Condition no. 1 requires magniX to comply with 14 CFR 33.4, which 
requires magniX to prepare Instructions for Continued Airworthiness in 
accordance with appendix A to that part. Appendix A requires the 
Instructions for Continued Airworthiness include instructions for 
installing and operating the engine. Special Condition no. 1 also 
mandates compliance with 14 CFR 33.5, which requires magniX to prepare 
and make available to the Administrator, prior to the issuance of the 
type certificate, and to the owner at the time of delivery of the 
engine, approved instructions for installing and operating the engine. 
The FAA made no changes to the special condition as a result of the 
comment.

Special Condition No. 7, Engine Mounting Attachments and Structure

    The FAA proposed that Special Condition no. 7 would require these 
engines to comply with 14 CFR 33.23, which requires the applicant to 
define the proposed design to withstand certain load limits for the 
engine mounting attachments and related engine structure. These 
requirements would otherwise be applicable only to reciprocating and 
turbine aircraft engines.
    Comment Summary: Textron stated that a propeller could be a much 
higher percentage of the total propulsion system mass in electric 
systems than for reciprocating or turbine engine propulsion systems and 
suggested that an electric motor's rotating components can be nearly 
instantly coupled to the non-rotating components due to FOD, internal 
failure, rotor growth, and commutation errors. Textron proposed 
additional requirements to Special Condition no. 7 related to sudden 
stoppage and bearing protection to ensure the engine mounting system 
can absorb the load or mitigate the effect of the load on aircraft.
    FAA Response: The FAA does not agree with the comment. The 
certification basis for the proposed engines includes 14 CFR 33.23, 
Engine mounting attachments and structure, which is a performance-based 
requirement. The regulation doesn't specify how maximum and ultimate 
loads are determined because these load conditions are determined by 
magniX. Also, Special Condition no. 2 requires magniX to establish a 
torque limit and Special Condition no. 21 requires magniX to establish 
a maximum overtorque limit. These requirements address the conditions 
described in Textron's comment. magniX's engines must be designed to 
accommodate the load at these limit values. These special conditions 
address high engine mount load conditions, including the conditions 
described in Textron's comment, except for loads from the

[[Page 53514]]

failure considerations that are normally addressed by Special Condition 
no. 17 (Safety Analysis). The FAA made no changes to the special 
condition as a result of the comment.
    Comment Summary: Textron recommended adding a requirement for 
bearing protection that states, ``Engine bearings must be protected 
from rotor voltage or a periodic replacement interval shall be 
determined as defined in Special Condition no. 13.''
    FAA Response: The FAA agrees with the technical content of this 
comment, but there is no requirement in these special conditions to add 
rotor shaft grounding technology in the magniX engines. Bearings could 
experience accelerated wear-out from ungrounded shafts, but the failure 
should not present a safety issue because the failure is predictable 
with sufficient testing. Requirements such as Sec.  33.4, Instructions 
for Continued Airworthiness, Special Condition no. 3 (Materials), 
Special Condition no. 5 (Durability), Special Condition no. 13 
(Critical and life-limited parts), and Special Condition no. 29 
(Teardown inspection) will all have a role in managing the consequences 
of potential bearing wear from electrical effects. magniX may assess 
the impact to product support at the predicted bearing replacement 
frequency and decide to include rotor shaft grounding technology.
    Comment Summary: TCCA recommended that the FAA add a requirement to 
this special condition, requiring the applicant to demonstrate that the 
engine mounts and mounting features are fireproof if flammable fluids 
are used within the engine.
    FAA Response: The FAA does not agree with the comment. The fire 
protection requirements in 14 CFR 33.17 apply to the magniX engines. 
The FAA made no changes to the special condition as a result of the 
comment.

Special Condition No. 8, Accessory Attachments

    The FAA received no comments for Special Condition no. 8, and it is 
adopted as proposed. It requires the engine to comply with 14 CFR 
33.25, which sets certain design, operational, and maintenance 
requirements for the engine's accessory drive and mounting attachments, 
and which would otherwise be applicable only to reciprocating and 
turbine aircraft engines.

Special Condition No. 9, Overspeed

    The FAA proposed that Special Condition no. 9 would require magniX 
to establish by test, validated analysis, or a combination of both, 
that: (1) The rotor overspeed not result in a burst, rotor growth, or 
damage that results in a hazardous engine effect; (2) rotors possess 
sufficient strength margin to prevent burst; and (3) operating limits 
of the engine not be exceeded in-service.
    Comment Summary: GE stated that proposed Special Condition no. 9(c) 
was duplicative of Special Condition no. 10(b) and (h) (Engine control 
systems), and requested the special condition be removed.
    FAA Response: The FAA does not agree with the comment. The special 
conditions referenced by GE accomplish different safety objectives. 
Special Condition no. 9(c) requires that the engine must not exceed the 
rotor speed operational limitations that could affect rotor structural 
integrity. This requirement results in an overspeed limit. Special 
Condition no. 10(b) requires the engine control system must ensure the 
engine does not experience any unacceptable operating characteristics 
or exceed its operating limits, 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, if applicable. The FAA made no changes to the special 
condition as a result of the comment.
    Comment Summary: Ampaire stated that Special Condition no. 9 
(Overspeed) should include more information from ASTM F3338-18.
    FAA Response: The FAA does not agree with the comment. ASTM F3338-
18 section 5.9, EPU Rotor Overspeed, contains technical criteria that 
the FAA used in developing these special conditions. It also contains 
information that the applicant can use to propose means of compliance 
to these special conditions. The FAA did not change this special 
condition as a result of this comment.
    Comment Summary: Textron recommended that the FAA modify Special 
Condition no. 9, paragraphs (a) and (c), replacing ``speed'' with 
``RPM.'' Textron reasoned that the term ``speed'' could be misleading.
    FAA Response: The units used for rotational speed in the 
limitations section of the engine manual can be expressed using various 
units. The FAA recognizes that ``rpm'' is used in 14 CFR 33.88, Engine 
overtemperature test and Sec.  33.201, Design and test requirements for 
Early ETOPS eligibility, but speed units are not specified in all 
regulations that mention engine rotor speed. Therefore, the FAA will 
maintain the term ``speed'' in these special conditions. The FAA did 
not change this special condition as a result of this comment.
    Comment Summary: TCCA stated that proposed Special Condition no. 9 
suggested that the controller will provide the engine overspeed 
protection and commented that the FAA should ensure that the overspeed 
protection will function as intended when exposed to high-intensity 
radiated fields (HIRF), lightning environments, and threats. TCCA 
stated that verification of this protection might require the electric 
motor and engine control system to be included in the test setup when 
conducting the HIRF and lightning transient system tests and 
recommended that these special conditions clarify this topic in the 
discussion section of these special conditions.
    FAA Response: This special condition is a performance-based 
requirement, and test details will be established as part of the 
demonstration of compliance. The FAA made no changes to the special 
condition as a result of the comment.
    Comment Summary: TCCA recommended that the FAA modify ``Rotors must 
possess'' as stated in Special Condition no. 9(b), to ``Rotors, 
including any integral fan rotors used for cooling, must possess.''
    FAA Response: These special conditions are not generally applicable 
to all electric engines; they apply only to the applicant's proposed 
engines. The magniX engines do not use integral fan rotors to cool the 
engine. The FAA did not change this special condition as a result of 
the comment.

Special Condition No. 10, Engine Control Systems

    The FAA proposed that Special Condition no. 10 would impose several 
requirements.
    Special Condition no. 10(a) proposed that the requirements of that 
special condition apply to any engine system or device that controls, 
limits, monitors, or protects engine operation and is necessary for the 
continued airworthiness of the engine.
    Special Condition no. 10(b) proposed to require that an engine 
control system ensure that the engine does not experience any 
unacceptable operating characteristics (such as unstable speed or 
torque control) or exceed any of its operating limits.
    Special Condition no. 10(c) proposed to require magniX to 
systematically design, develop, and verify the software and complex 
electronic hardware, including programmable logic devices. RTCA DO-254, 
Design Assurance Guidance for Airborne Electronic

[[Page 53515]]

Hardware, dated April 19, 2000,\6\ distinguishes between complex and 
simple electronic hardware.
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    Special Condition no. 10(d) proposed to require the applicant to 
substantiate all functional aspects of the control system to show that 
it performs its intended functions throughout the declared operational 
envelope.
    Special Condition no. 10(e) proposed to require the system and 
component tests in Special Condition no. 27 to demonstrate the control 
will function as intended at environmental limits that magniX cannot 
otherwise substantiate. These limits include temperature, vibration, 
HIRF, and other limits addressed in RTCA DO-160G, Environmental 
Conditions and Test Procedures for Airborne Electronic/Electrical 
Equipment and Instruments \7\ (DO-160G) or other appropriate industry 
standards for airborne environmental-conditions testing, such as Mil-
STD-810 ``Environmental Engineering Considerations and Laboratory 
Tests,'' Mil-STD-202 ``Test Method Standard for Electronic and 
Electrical Component Parts,'' Mil-461 ``Requirements for the Control of 
Electromagnetic Interference Characteristics of Subsystems and 
Equipment,'' and those listed in Advisory Circular 21-16G, RTCA 
Document DO-160 versions D, E, F, and G, ``Environmental Conditions and 
Test Procedures for Airborne Equipment,'' Special Condition no. 10(e) 
also requires magniX to document the environmental limits to which the 
system has been qualified in the engine installation manual.
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    \7\ https://my.rtca.org/NC__Product?id=a1B36000001IcnSEAS.
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    Special Condition no. 10(f) proposed to require the engine control 
system not to exceed a maximum rate of Loss of Power Control (LOPC) for 
the aircraft types that will use the magniX engines, be single-fault 
tolerant in the full-up configuration, not have any single failure that 
results in hazardous engine effects, and not have any likely failure or 
malfunction that lead to local events in the intended installation.
    The FAA issued Advisory Circular AC 33.28-3, Guidance Material For 
14 CFR 33.28, Engine Control Systems, on May 23, 2014.\8\ Paragraph 6-2 
of this AC provides applicants with guidance about defining an engine 
control system failure when showing compliance with the requirements of 
Sec.  33.28. It also explains the safety objectives of the 
requirements, provides criteria for a loss of thrust control (LOTC)/
LOPC events for reciprocating and turbine engines. However, the 
guidance in AC 33.28-3 may not have sufficient information to identify 
failure modes and establish acceptable LOTC/LOPC rates for the magniX 
electric engines because electric engines did not exist when the FAA 
issued this AC.
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    The phrase ``in the full-up configuration'' used in Special 
Condition no. 10(f)(2) refers to a system without any fault conditions 
present. When in the full-up configuration, the electronic control 
system must be single fault tolerant for electrical, electrically 
detectable, and electronic failures involving LOPC events.
    The term ``local events'' used in Special Condition no. 10(f)(4) 
means failures or malfunctions that could lead to hazardous effects 
such as fire, overheat, or failures causing damage to engine control 
system components.
    Special Condition no. 10(g) proposed to require magniX to conduct a 
system safety assessment to support the safety analysis in Special 
Condition no. 17.
    Special Condition no. 10(h) proposed to require that the design and 
function of the engine control devices and systems, together with the 
engine instruments, operating instructions, and maintenance 
instructions, ensure that engine operating limits will not be exceeded 
in-service.
    Special Condition no. 10(i) proposed to protect the airplane and 
engine from single failures relating to the aircraft-supplied data by 
mandating that the control system is able to detect and accommodate 
such failures, and not result in a hazardous engine effect.
    The term ``independent,'' as it is used in ``fully independent 
engine systems,'' means that the controllers should be either self-
sufficient and isolated from other aircraft systems or provide 
redundancy. In the case of loss, interruption, or corruption of 
aircraft-supplied data, the engine must continue to function without 
hazardous engine effects.
    The term ``accommodated'' means that when a fault has been 
detected, the system must continue to function safely.
    Special Condition no. 10(j) proposed to require magniX to show that 
the loss, malfunction, or interruption of the control system electrical 
power source will not result in a hazardous engine effect, the 
unacceptable transmission of erroneous data, or continued engine 
operation in the absence of the control function.
    Comment Summary: Rolls-Royce asked that the FAA clarify the 
requirements contained in Special Condition nos. 10(f)(1) and (f)(2). 
The commenter expressed concern that the single fault tolerance 
requirement in Special Condition no. 10(f)(2) would be applied to both 
historical electrical elements of the engine control system and to the 
new high-voltage electrical/electronic elements required to motivate an 
electric motor. Rolls-Royce commented that it was possible the wording 
of this condition would be extended to cover loss of power (LOP) events 
due to the difficulties of establishing the boundary between the 
control and the motor drive in an electric engine. Rolls-Royce asked 
the FAA to modify this special condition to clarify that the degree of 
fault tolerance in the high-voltage electrical/electronic elements will 
be governed by the LOP reliability requirement of Special Condition no. 
10(f)(1), and not the single fault tolerance requirement of LOPC of 
Special Condition no. 10(f)(2). AIAB articulated a similar concern and 
recommended the FAA delete Special Condition no. 10(f)(2) in these 
final special conditions. AIAB stated a loss of thrust control (LOTC)/
LOPC event could be considered minor in aircraft with distributed 
propulsion, and therefore may not require electrical redundancy.
    FAA Response: The comments from Rolls-Royce and AIAB describe the 
potential dependency between the electric engine safety analysis and 
certain aircraft configurations, and the potential effect the aircraft 
design could have on the need for engine design redundancy. However, 
magniX designed these engines for certain aircraft configurations that 
do not have special flight control capabilities, which is why the LOPC 
and single fault tolerance criteria from 14 CFR part 33 are adopted in 
these special conditions. The FAA also included ``suitable for the 
intended aircraft application'' in Special Condition no. 10(f)(1), and 
``as determined by the Administrator'' in Special Condition no. 
10(f)(2) ``Engine control system failures'' to constrain the use of 
these engines to aircraft that are designed with compatible engine 
safety assumptions. Therefore, the FAA did not change these special 
conditions as a result of this comment.
    Comment Summary: TCCA commented that the FAA's introductory text to 
proposed Special Condition no. 10(e), ``Environmental limits,'' 
indicated that the environmental limits are addressed in DO-160G. 
However, TCCA suggested that some of the test specifications, methods, 
and categories in DO-160G might not be adequate for high-voltage 
systems such as the high-voltage components of this engine. TCCA 
suggested that the FAA modify Special Condition no. 10(e) to require

[[Page 53516]]

that the applicant establish and demonstrate the environmental limits 
of the engine for those circumstances when the standards in DO-160G may 
not be adequate.
    FAA Response: These special conditions are applicable to this 
applicant's project and are not generally applicable requirements. As 
such, the FAA will evaluate the approach that the applicant proposes to 
substantiate the compliance of their design's high-voltage systems. The 
FAA made no changes to these special conditions as a result of this 
comment.
    Comment Summary: TCCA noted that in the introduction to proposed 
Special Condition no. 10(f), the FAA stated that ``As with other topics 
within these proposed special conditions, the failure rates that apply 
to electric engines were not established when the FAA issued this AC'' 
[referring to AC 33.28-3]. TCCA stated that the referenced FAA guidance 
document might not have sufficient data to allow an applicant to 
substantiate the selected failure modes and failure rates applicable to 
the electrical engine and associated high-voltage systems. TCCA 
recommended that the FAA clarify the statement in the discussion and 
note that the applicant has the responsibility to substantiate the 
failure modes and rates to show compliance to these special conditions.
    FAA Response: The FAA added clarification to the discussion of 
Special Condition no. (10)(f).
    Comment Summary: TCCA asked the FAA to clarify whether the engine 
cockpit controls are part of the configuration discussed in Special 
Condition no. 10. TCCA also recommended that the FAA require the 
applicant to conduct a human error assessment to mitigate the effects 
of crew mistakes due to electric engine cockpit controls if they are 
different from conventional engine cockpit controls.
    FAA Response: The engine cockpit controls are not part of the 
engine configuration. No changes to these final special conditions are 
required to address TCCA's comment.
    Comment Summary: TCCA requested that Special Condition no. 10(a) 
use similar wording as 14 CFR 33.28(a). TCCA stated that such wording 
could affect the applicant's understanding of the requirement because 
the proposed words indicate Special Condition no. 10(a) could also be 
applicable to a system or a device that is not part of the engine type 
design.
    FAA Response: In these final special conditions, the FAA has 
modified Special Condition no. 10(a) to incorporate the purpose of 14 
CFR 33.28(a).
    Comment Summary: TCCA stated proposed Special Condition no. 10(j) 
requires that the loss, malfunction, or interruption of the electrical 
power to the engine control system not result in a hazardous engine 
effect, the unacceptable transmission of erroneous data, or continued 
engine operation in the absence of the control function. TCCA stated 
that this special condition does not require the engine control system 
to be capable of resuming normal operation when the electrical power 
returns to a normal state. TCCA commented that the electrical power 
source could be subject to transients resulting in a temporary effect 
on the output power and shut down the control system and/or engine. 
TCCA explained once the temporary transients cease, the engine control 
system should be capable of resuming normal operation when the power 
characteristics return to the normal range (similar to the requirements 
of (14 CFR) 33.28(i)(4). TCCA proposed adding a subparagraph to Special 
Condition no. 10(j) to require, ``Voltage transients outside the power-
supply voltage limitations declared in SC 10(j)(2) must meet the 
requirements of SC no. 10(j)(1). The engine control system must be 
capable of resuming normal operation when electrical power returns to 
within the declared limits.''
    FAA Response: A special condition is not required to specify 
requirements for voltage transients that are outside the power-supply 
voltage limitations declared in Special Condition no. 10(j)(2), 
``Engine control system electrical power'' because exceedances to these 
limitations are addressed by Special Condition no. 10(h), ``Protection 
systems.'' Special Condition no. 10(j)(1) corresponds to 14 CFR 
33.28(i), which includes the additional requirement TCCA recommended. 
The FAA added, ``The engine control system must be capable of resuming 
normal operation when aircraft-supplied power returns to within the 
declared limits'' to Special Condition no. 10(j)(1) as a result of this 
comment.
    Comment Summary: TCCA stated Special Condition no. 10 is similar to 
the current 14 CFR 33.28 requirement. TCCA suggested modifying Special 
Condition no. 10 to state, ``The engine design must comply with 14 CFR 
33.28.''
    FAA Response: 14 CFR 33.28 is applicable to reciprocating and 
turbine aircraft engines. The airworthiness regulations in 14 CFR 33.28 
do not contain adequate or appropriate safety standards for the 
magni350 and magni650 model engines because of a novel or unusual 
design feature (use of electrical energy source instead of aviation 
fuel to drive the mechanical systems). Section 33.28 contains design 
requirements that do not apply to the proposed engines. The FAA did not 
change these special conditions as a result of this comment.
    Comment Summary: TCCA recommended that Special Condition no. 10(j) 
require the applicant to define and declare, in the engine installation 
manual, the characteristics of the electrical power supplied to the 
engine control system, as required by 14 CFR 33.28(i)(3).
    FAA Response: The FAA has added a subparagraph to Special Condition 
no. 10(j) ``Engine control system electrical power,'' which requires 
magniX to identify and declare the characteristics of any electrical 
power supplied from the aircraft to the engine control system for 
starting and operating the engine, including transient and steady-state 
voltage limits, and any other characteristics necessary for the safe 
operation of the engine in the engine installation manual.
    Comment Summary: TCCA recommended that Special Condition no. 10 
require a means to shut the engine down rapidly.
    FAA Response: Special Condition no. 17(d)(2) incorporates 14 CFR 
33.75(g)(2)(vii), which includes, as a hazardous engine effect, the 
complete inability to shut the engine down. The FAA made no changes to 
these special conditions as a result of this comment.
    Comment Summary: TCCA commented that the proposed special 
conditions do not address the emerging issue of cybersecurity. Since 
the FAA is currently addressing this issue with an issue paper, TCCA 
recommended incorporating the issue paper into Special Condition no. 10 
by reference.
    TCCA also recommended that the FAA address cybersecurity by adding 
a special condition that states, ``Information system security 
protection. Engine control systems, including networks, software, and 
data, must be designed and installed so that they are protected from 
intentional unauthorized electronic interactions (IUEI) that may result 
in adverse effects on the safety of the aircraft. The security risks 
and vulnerabilities must be identified, assessed, and mitigated as 
necessary. The applicant must make procedures and instructions for 
continued airworthiness (ICA) available that ensure that the security 
protections of the engine controls are maintained.''
    FAA Response: The FAA does not agree with the comment. A special 
condition for cybersecurity is not

[[Page 53517]]

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. 10(b).
    Comment Summary: Wisk asked what the FAA meant by ``be single fault 
tolerant, as determined by the Administrator'' in proposed Special 
Condition no. 10(f)(2).
    FAA Response: The term ``single fault tolerant'' describes an 
engine control system's 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. 10(f)(2) 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. 10(f)(4) 
``Engine control system failures.''
    FAA Response: The term ``local events'' used in Special Condition 
no. 10(f)(4) 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. 10(g), ``System safety assessment.'' Wisk stated 
that the condition was unnecessary and could lead to uncertainty 
because 14 CFR 33.75(a), Safety analysis, is more rigorous. Wisk 
suggested incorporating Sec.  33.75(a)(1) into Special Condition no. 
10, or linking Special Condition no. 17 to Special Condition no. 10(g).
    FAA Response: Special Condition no. 17 (Safety Analysis), 
incorporates 14 CFR 33.75(a)(1), which requires the 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 
Sec.  33.28(i) 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. 10(j) 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 F3338-18 section 5.10, EPU Controls, into Special 
Condition no. 10(g), system safety assessment, and Special Condition 
no. 10(h), protection systems.
    FAA Response: ASTM F3338-18 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 
14 CFR 33.28(h)(2). AIAB stated that the accommodation strategy could 
depend on the aircraft that use the engines because the aircraft's 
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. (10)(g) 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 applicant's fault accommodation strategies will need to account for 
the aircraft's 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. 10(e), 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. 
10(h) matches the requirements of Sec.  33.28(f)(1), but the 
requirements of Sec.  33.28(f)(2) and (f)(3) 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 10(h) 
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.

[[Page 53518]]

    Comment Summary: Textron recommended that the FAA add the following 
to the end of Special Condition no. 10(b), ``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 
33.28(c) 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. 10(b) 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 33.29(a), (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. 10(g)'' 
and recommended that the FAA replace the citation in Special Condition 
no. 11 with reference to Special Condition no. 17 or 14 CFR 
33.75(a)(1).
    FAA Response: Special Condition no. 10(g) 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 33.75(a)(1), which requires an engine-level 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 33.29(f), thereby requiring the applicant to 
assess the possibility and subsequent effects of incorrect fit of 
instruments, sensors, or connectors. Textron considered this 
requirement to repeat the assessments required by Special Condition no. 
10(g) (Engine control systems). For this reason, Textron recommended 
removing the provisions in Special Condition no. 11 that are adopted by 
reference to Sec.  33.29(f).
    FAA Response: Special Condition no. 10(g) corresponds to Sec.  
33.28(e), which requires an engine control systems safety assessment. 
However, Sec.  33.29(f) requires that, as part of the System Safety 
Assessment of Sec.  33.28(e), 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 10(g). After reviewing Textron's 
comment, the FAA removed reference to Sec.  33.29(f) because the 
content of that regulation is captured within Special Condition no. 
11(a). 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 33.29(a) to the magniX engines, so this 
special condition already requires that the connections meet the 
criteria specified in TCCA's 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 33.5(a)(6), 33.5(c), and Special Condition no. 17(c), 
which encompasses Sec.  33.75(d) and Sec.  33.75(e). 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 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 Sec.  33.62 Stress analysis. 
The corresponding part 33 airworthiness requirement for Special 
Condition no. 9 (Overspeed) is Sec.  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 Wisk's 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. 12(a).
    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

[[Page 53519]]

TCCA. In addition, design margins are also required by Special 
Condition nos. 9 (Overspeed), 12 (Stress Analysis), 19 (Liquid 
Systems), 24 (Temperature Limit), and 30 (Containment). No changes have 
been made to this special condition as a result of this comment.

Special Condition No. 13, Critical and Life-Limited Parts

    The FAA proposed that Special Condition no. 13 would require magniX 
to show whether rotating or moving components, bearings, shafts, static 
parts, and non-redundant mount components should be classified, 
designed, manufactured, and managed throughout their service life as 
critical or life-limited parts.
    Special Condition no. 13 corresponds to 14 CFR 33.70, Engine life-
limited parts, which is a complex requirement. Accordingly, additional 
information is provided in this discussion. In this context, the 
engineering plan referenced in Special Condition no. 13(b)(1) requires 
magniX to establish activities for managing documents, practices, and 
procedures that govern essential design criteria essential to part 
airworthiness. The engineering plan contains methods for verifying the 
characteristics and qualities assumed in the design data. The methods 
must be suitable for the part criticality. The engineering plan 
communicates information from engineering to manufacturing about the 
criticality of design features that affect airworthiness. In accordance 
with 14 CFR 21.137, Quality system, the plan must include a reporting 
system that flows problematic issues that develop while operating in-
service so the applicant's design process can address them. The 
engineering plan is established during pre-certification activities and 
executed during post-certification activities.
    For example, the effect the environment has on engine performance 
might not be consistent with the design assumptions. The impact of ice 
slab ingestion on engine parts might not be fully understood until the 
engine response is evaluated during testing the specific ice quantities 
and shapes that the airplane sheds.
    The term ``low-cycle fatigue,'' as referenced in Special Condition 
no. 13(a)(2), is a decline in material strength from exposure to cyclic 
stress at levels beyond the stress threshold the material can sustain 
indefinitely. This threshold is known as the material endurance limit. 
Low-cycle fatigue typically causes a part to sustain plastic or 
permanent deformation during the cyclic loading and can lead to cracks, 
crack growth, and fracture. Engine parts that operate at high-
temperatures and high-mechanical stresses simultaneously can experience 
low-cycle fatigue coupled with creep. Creep is the tendency of a 
metallic material to permanently move or deform when exposed to the 
extreme thermal conditions created by hot combustion gasses and 
substantial physical loads such as high rotational speeds and maximum 
thrust. Conversely, high-cycle fatigue is caused by elastic 
deformation, small strains caused by alternating stress, and a much 
higher number of load cycles compared to the number of cycles that 
cause low-cycle fatigue.
    The term ``manufacturing definition,'' as referenced in Special 
Condition no. 13(b)(2), means the collection of data required to 
translate documented engineering-design criteria into physical parts 
and verify that the parts comply with the design data properties. 
Because FAA regulations do not require parts to fail during a 
certification program, the documents and processes have outcome 
expectations, required by 14 CFR 21.137, Quality system and 14 CFR 
21.138, Quality manual, to result in parts with the integrity and 
reliability assumed in the design data. These production and quality 
systems limit the potential manufacturing outcomes to parts that are 
consistently produced within physical design constraints.
    The manufacturing plan and service management plan ensure essential 
information from the engineering plan, such as the design 
characteristics that ensure the integrity of critical and life-limited 
parts, is consistently produced and preserved over the lifetime of 
those parts. The manufacturing plan includes special processes and 
production controls to prevent manufacturing-induced anomalies, which 
can degrade the part's structural integrity. Examples of manufacturing-
induced anomalies are material contamination, unacceptable grain 
growth, heat affected areas, and residual stresses. The service 
management plan has provisions for enhanced detection and reporting of 
service-induced anomalies that can cause the part to fail before 
reaching its life-limit or service limit. Abnormalities can develop in-
service from improper handling, unforeseen operating conditions, and 
long-term environmental effects. The service management plan ensures 
important information that might affect the design process's 
assumptions is incorporated into the design process to remove 
unforeseen potential unsafe features from the engine.
    Comment Summary: Wisk stated it is more appropriate to use ``The 
Applicant'' than the Company name ``magniX'' in Special Condition no. 
12(b)(1). Wisk recommended changing the reference to the engine 
manufacturer reference from ``magniX'' to ``the applicant.''
    FAA Response: The FAA understands Wisk's comment to be relevant to 
Special Condition no. 13(b)(1) because Special Condition no. 12(b)(1) 
does not exist. These special conditions are not applicable to all 
electric engine manufacturers. As stated in this preamble, these 
special conditions apply to the magniX magni350 and magni650 model 
engines. No change to this special condition is necessary as a result 
of this comment.
    Comment Summary: Textron recommended that the post-certification 
activities described in the Discussion section of the proposed special 
conditions be included in the text of Special Condition no. 13.
    FAA Response: The Discussion for this special condition is based on 
its similarity to 14 CFR 33.70, Engine life-limited parts. No change to 
this special condition is necessary as a result of this comment.
    Comment Summary: An individual commenter suggested there might be 
unique questions regarding low-cycle fatigue (LCF) of components used 
in electric engines. The commenter explained that if the core rotor 
speed is low, the risk of a rotor burst might not be significant. 
However, a core rotor assembly that uses windings or embedded permanent 
magnets (if applicable) may have some LCF/thermal/electrical (refer to 
corona effect on motor windings) cycling challenges and the 
electrically powered electronics driving the motor. The individual also 
stated that they have learned through experience about the significance 
of thermal effects resulting from a broad range of operating 
conditions, especially during quick power transients.
    FAA Response: Special Condition no. 13 requires magniX to determine 
the parts and components that should be classified designed, 
manufactured and managed throughout their service life as critical or 
life-limited parts. Therefore, Special Condition no. 13 provides the 
requirements for magniX to address the unique issues that arise when 
identifying and managing life-limited and critical electric engine 
parts. The FAA made no changes to these special conditions as a result 
of this comment.
    Comment Summary: TCCA stated that 14 CFR 33.70 is similar enough to 
proposed Special Condition no. 13 that the FAA should replace the 
proposed special condition with reference to the 14 CFR part 33 
requirement and modify it. EASA suggested the FAA remove the

[[Page 53520]]

term ``Critical Parts'' from this special condition.
    FAA Response: Section 33.70 prescribes a mandatory replacement 
interval for turbine engine parts that are likely to fail from fatigue 
if they are not removed from service. The failure can cause a hazardous 
engine effect. Section 33.70 does not address parts that have a 
different primary failure mode than fatigue but can still fail in a way 
that causes a hazardous engine condition. Electric engine technology 
operates using electromagnetic technology and physical properties that 
are different than those of turbine engines. This is why the special 
condition has requirements for ``critical'' parts. Therefore, there is 
a need for a special condition that addresses failures of parts and 
components caused by the properties related to the novel technology 
used in these proposed engines. Further, the FAA currently uses the 
term ``critical parts'' to describe certain parts approved under 14 CFR 
part 21 subpart K, Parts Manufacturer Approval and in 14 CFR part 35, 
Airworthiness Standards: Propellers. The use of the term ``critical 
parts'' in these special conditions is consistent with the FAA's use of 
the term as it applies to conventional engines. The FAA did not change 
these special conditions as a result of these two comments.
    Comment Summary: TCCA asked that these special conditions define 
``primary failure'' as failures that are not the result of a prior 
failure of another part or system.
    FAA Response: The term ``primary failure'' is used in 14 CFR 33.70, 
and this special condition is based on the requirements in that 
section. The FAA did not change these special conditions as a result of 
this comment, but the suggested clarification is adopted in the 
discussion to Special Condition no. 17.
    Comment Summary: AIAB proposed that the FAA require the assumptions 
used by the applicant in the life-limited parts analysis to be declared 
in the engine installation manual, should the FAA certify the engine 
with no associated aircraft.
    FAA Response: Final Special Condition nos. 10(g) and 17(e) require 
magniX to account for the intended aircraft application for the engine 
safety analysis and engine control systems safety assessment to be 
valid, so there will be no need to account for engines with no 
associated aircraft. Special Condition no. 13, Critical and life-
limited parts, requires magniX to show, by safety analysis or means 
acceptable to the Administrator, whether rotating or moving components, 
bearings, shafts, static parts, and non-redundant mount components 
should be classified, designed, manufactured, and managed throughout 
their service life as critical or life-limited parts. The assumptions 
used by magniX in the life-limited parts analysis are design data that 
provide information for compliance to Special Condition no. 13. The 
installers and operators of the magniX engines do not use these 
assumptions, and therefore, the assumptions do not need to be included 
in the installation manual. The FAA made no changes to this special 
condition as a result of this comment.

Special Condition No. 14, Lubrication System

    The FAA proposed that Special Condition no. 14 would require that 
the lubrication system of these engines be designed to function 
properly between scheduled maintenance intervals and prevent engine 
bearing and lubrication system contamination. The FAA also proposed to 
require magniX to demonstrate the unique lubrication attributes and 
functional capability of the magni350 and magni650 Model engines.
    Comment Summary: Wisk recommended removing the reference to 
``particle debris'' from Special Condition no. 14(b), and replacing it 
with ``The lubrication system must be designed to prevent unacceptable 
contamination of the engine bearings.''
    FAA Response: The FAA has changed Special Condition no. 14 to 
specify the lubrication system must prevent any unacceptable 
contamination of the engine bearings. The FAA has changed the special 
condition as a result of this comment.
    Comment Summary: TCCA recommended that Special Condition no. 14 
require magniX to declare, in the engine installation manual, any 
reliance upon assumed installation conditions or installation 
requirements.
    FAA Response: Special Condition no. 1 requires magniX to comply 
with14 CFR 33.5, Instruction manual for installing and operating the 
engine. Section 33.5(a)(5) includes the additional requirement 
recommended by TCCA. The FAA made no changes to the special condition 
as a result of the comment.

Special Condition No. 15, Power Response

    The FAA proposed that Special Condition no. 15 would require the 
design and construction of these engines and their control systems to 
enable an increase (1) from the minimum power setting to the highest-
rated power without detrimental engine effects and (2) from the minimum 
obtainable power while in-flight and on the ground to the highest-rated 
power within a time interval for the safe operation of the aircraft.
    Comment Summary: Wisk recommended including the engine control 
system as part of the engine in these requirements. They suggest adding 
``and its control system'' to this special condition to read, ``The 
design and construction of the engine and its control system must 
enable an increase.''
    FAA Response: The FAA has modified Special Condition no. 15 in 
these final special conditions to incorporate ``including its control 
system'' in response to the comment.
    Comment Summary: Ampaire recommended that the FAA add a requirement 
to these special conditions that correspond to ASTM F3338-18, section 
5.20.9.
    FAA Response: The FAA added Special Condition no. 15(c) in the 
final special condition, which incorporates criteria from ASTM F3338-
18, section 5.20.9.
    Comment Summary: Textron commented that electrical motors could 
produce significantly more torque than reciprocating or turbine 
engines. Textron said that unregulated application of torque could be 
detrimental to the flight characteristics of the aircraft or the 
structural components of the aircraft. Textron recommended 
supplementing this special condition with the following requirement: 
``(c) of torque without detrimental engine or aircraft effects. 
Aircraft components must be designed to withstand the unregulated 
application of torque, or the application of torque should be 
controlled to ensure aircraft structural integrity or aircraft 
aerodynamic characteristics are not exceeded.''
    FAA Response: The FAA agrees that electric engines produce torque 
differently than turbine engines. The potential for high torque values 
is attributable to the novel technology used in magniX's proposed 
engines. Therefore, final Special Condition no. 15 has changed to 
include a requirement that prevents engine torque from causing 
detrimental aircraft effects.
    Comment Summary: TCCA recommended that the FAA revise Special 
Condition no. 15(b), from ``a time interval for the safe operation of 
the aircraft'' to ``a time interval that is determined to be safe for 
aircraft operation.''
    FAA Response: The FAA finds that the recommended revision would be 
beneficial and consistent with the

[[Page 53521]]

change the FAA made to Special Condition no. 10(g) and the addition to 
Special Condition no. 17(e), which requires magniX to take into account 
the intended aircraft application in the engine installation manual. 
The FAA has changed final Special Condition no. 15(b) 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 Sec.  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 Sec.  33.73, so all requirements of Sec.  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 33.75(a)(1), (a)(2), and (a)(3), 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 on-condition 
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 part's 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. 17(e) and 10(g) require magniX to account for the 
intended aircraft application in the engine installation manual to 
ensure the 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. 17(d)(3), 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. 17(d)(1) use the existing words of Sec.  33.75(g)(1), 
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. 10(f)(1) requires the 
LOPC rate to be suitable for the intended aircraft application; and 
Special Condition no. 10, including 10(f)(2), 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. 17(b). 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. 17(b) 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

[[Page 53522]]

necessary requirements to achieve the safety analysis goals. EASA 
provided a similar comment and recommendation.
    FAA Response: In response to these comments, the FAA has changed 
final Special Condition no. 17(b) to ensure all the applicable 
integrity requirements are applied to magniX engine parts that can fail 
and are likely to result in hazardous engine effects.
    Comment Summary: GE commented that the definitions of ``major'' and 
``minor'' engine effects, as mentioned in Special Condition nos. 
17(d)(1), 17(d)(2), and 17(d)(3) are ambiguous, leaving a wide gap in 
the failure types that could be classified as hazardous or major engine 
effects. GE also commented that there is no probability requirement for 
major engine effects like there is in 14 CFR 33.75(a)(4). GE 
recommended that the FAA clarify the definitions of major and minor 
engine effects, and include a probability requirement to ensure a level 
of safety commensurate with the current regulations.
    FAA Response: These special conditions are not generally applicable 
to all electric engines. They apply only to these proposed magniX 
engines. The FAA acknowledges many possible outcomes to the engine 
safety analysis, including the failure classifications. Failure 
classification and probabilities for the engine and certain electronic 
components are still needed, but the failure classifications and 
reliability thresholds will account for the aircraft's capabilities. 
Special Condition no. 17 does not specify the engine failure effects 
that could be classified as major because aircraft's capabilities can 
affect the failure classification.
    As a result of this comment, the FAA modified final Special 
Condition nos. 17(d)(1) and 17(d)(3) to clarify the differences between 
major and minor engine failure effects. The FAA also added final 
Special Condition no. 17(e) to account for the potential influence 
aircraft capabilities may have on the engine safety analysis.
    Comment Summary: Ampaire recommended adding criteria from the 
industry standard ASTM F3338-18, sections 5.18.1 through 5.18.6, to 
Special Condition no. 17.
    FAA Response: ASTM F3338-18 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: Textron stated that electrical-component 
manufacturers typically do not know how their components will be used 
or the implications to safety when changes are made to the design and 
manufacturing process. Textron recommended modifying Special Condition 
no. 17(c) to state: ``In addition, if electrical components of a safety 
system are outside the control of the engine manufacturer, then the 
manufacturer must implement a component tracking system to monitor 
component revisions, change of manufacture, counterfeit parts, and 
component end of life (EOL).''
    FAA Response: Textron's comment identified a need for engine-level 
configuration control. The FAA acknowledges that a product's end-user 
could affect the intended engine configuration through parts 
manufacturer approvals and supplemental type certificates. However, the 
FAA imposed Special Condition no. 1, which mandates magniX's compliance 
with14 CFR 33.5(a)(5), 33.5(c), and 33.75 (d) to manage non-OEM engine 
configurations. The FAA made no changes to the special condition as a 
result of the comment.
    Comment Summary: Safran noted that Special Condition no. 17(a) 
requires magniX to comply with 14 CFR 33.75(a)(3), which establishes a 
fixed numerical value of 10-7 per flight hour for 
``extremely remote;'' a number that might exceed the aircraft safety 
objectives. For example, ``extremely remote'' for a part 23/Level 1 
aircraft application is rated at 10-5 per flight hour, not 
10-7. EASA shared Safran's concern and recommended that the 
FAA use the EASA SC E-18 \9\ to establish engine safety objectives that 
are proportional to the safety objectives of the intended aircraft when 
they are equipped with the magniX engines.
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    FAA Response: Both comments presume the general applicability of 
the proposed special conditions. These special conditions apply only to 
magniX's two proposed engine models. The aircraft that will use the 
magniX engines do not include Part 23/Level 1 aircraft. However, the 
FAA acknowledges that acceptable engine failure rates could vary 
depending on the aircraft's configuration and capabilities. Therefore, 
the FAA removed reference to Sec.  33.75(a)(3) from Special Condition 
no. 17(a). Also, The FAA changed final Special Condition no. 10(g) and 
added Special Condition no. 17(e) to require magniX to account for the 
intended aircraft application.
    Comment Summary: TCCA stated the term ``electrocution'' is defined 
as ``to kill with electricity'' and recommended that the FAA change the 
term ``electrocution'' in this special condition to ``electric shock'' 
or ``injury from electric shock.''
    FAA Response: The FAA does not agree with the comment. The term 
``electrocution,'' as used in these special conditions, is consistent 
with the risk of serious injury or fatality caused by electric shock.
    Comment Summary: TCCA asked the FAA to explain why proposed Special 
Condition no. 17 did not include the requirement for major failure 
rates in 14 CFR 33.75(a)(4).
    FAA Response: To account for the potential dependency between the 
electric engine safety analysis and the aircraft capabilities, the FAA 
did not prescribe failure rates for major engine failures. Special 
Condition no. 10(g) and Special Condition no. 17(e) require magniX to 
account for the intended aircraft application. magniX will still need 
to classify major failures for the engine and certain electronic 
components, but the failure rates will account for aircraft 
capabilities. The FAA has changed the special condition as a result of 
this comment.
    Comment Summary: TCCA asked the FAA to consider requiring the 
applicant's safety analysis to analyze uncontrollable high thrust and 
potential physical separation of the engine from the aircraft.
    FAA Response: The FAA understands TCCA's reference to 
``uncontrollable'' high thrust to mean a higher thrust than the 
commanded thrust or a thrust that is above a limit value. Special 
Condition no. 10(f)(1) requires a maximum LOPC rate for the intended 
aircraft that will use the magniX engines, and magniX will need to show 
how they comply with those rates. Special Condition no. 17(d)(2) 
requires magniX to comply with 14 CFR 33.75(g)(2)(v), which addresses 
the physical separation of the engine from the aircraft. The FAA did 
not change this special condition as a result of this comment.
    Comment Summary: TCCA suggested that the FAA require magniX to show 
that a cooling loss will not result in a hazardous engine effect or 
that blockage cannot lead to a cooling failure. TCCA's comment was 
directed to Special Condition no. 18 in the context of protecting the 
cooling inlet from ingestion.
    FAA Response: In response to TCCA's comment, the FAA has included a 
requirement in Special Condition no.

[[Page 53523]]

17(d)(2)(ii) to prevent hazardous engine effects from cooling blockage.
    Comment Summary: EASA commented that the special condition has no 
proposed safety objectives for major failure conditions. EASA 
recommended that the FAA use the approach of EASA SC E-19 \10\ that 
requires the propulsion system to have a level of safety that allows 
the intended aircraft to meet its safety objectives defined in the 
aircraft type certification basis.
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    FAA Response: There are many possible outcomes to the magniX engine 
safety analysis, including the failure classifications. Failure 
classification and probabilities for the engine and certain electronic 
components are needed, but the failure classifications and reliability 
thresholds will account for aircraft capabilities. The FAA has changed 
final Special Condition no. 10(g) and added Special Condition no. 17(e) 
to require magniX to account for the intended aircraft application.
    The additions to Special Condition nos. 10(g) and 17(e) allow for 
the aircraft safety objectives to be considered when establishing the 
engine failure classifications and failure rates.
    Comment Summary: EASA noted the reference to Special Condition no. 
9 in Special Condition no. 17(b): ``If the failure of such elements is 
likely to result in hazardous engine effects, then the applicant may 
show compliance by reliance on the prescribed integrity requirements of 
14 CFR 33.15, Special Condition no. 9, or Special Condition no. 13, as 
determined by analysis.''
    EASA stated that proposed Special Condition no. 9 is insufficient 
for hazardous failure conditions. EASA said that a rotor growth margin 
is a design margin, but it does not preclude any other failure root 
cause of a failure, such as a production issue. EASA suggested that the 
FAA change these special conditions to remove this possibility.
    FAA Response: The FAA agrees with the comment. There might be a 
need to consider additional integrity requirements to account for the 
potential root causes for failures of the magniX electric engine parts. 
The FAA has changed final Special Condition 17(b) to add ``such as'' 
before the list of integrity requirements.

Special Condition No. 18, Ingestion

    The FAA proposed that Special Condition no. 18 would require magniX 
to ensure that these engines will not experience unacceptable power 
loss or hazardous engine effects from ingestion. For example, the 
current bird-ingestion airworthiness regulation for turbine engines, 14 
CFR 33.76, is based on potential damage from birds entering a turbine 
engine with an inlet duct that directs air into the engine for 
combustion, cooling, and thrust. In contrast, these electric engines do 
not use an inlet duct for those purposes. Instead, the electric engine 
inlet duct is primarily used to streamline the air entering the inlet 
for efficient cooling of internal engine components.
    An ``unacceptable'' power loss, as stated in Special Condition no. 
18(a), refers to a situation in which the power or thrust required for 
safe flight of the aircraft becomes unavailable to the pilot. The 
specific amount of power loss necessary for a safe flight depends on 
the aircraft configuration, speed, altitude, attitude, atmospheric 
conditions, phase of flight, and other circumstances, where the demand 
for thrust is critical to the aircraft's safe operation.
    This special condition also requires magniX to declare the 
ingestion sources that are not evaluated in the engine installation 
manual.
    Comment Summary: Textron recommended that this special condition 
quantify the ingestion threats in a manner similar to the way they are 
quantified for turbine engines in 14 CFR 33.76, Bird ingestion, Sec.  
33.77, Foreign object ingestion--ice, and Sec.  33.78, Rain and hail 
ingestion. The commenter suggested that bird numbers and sizes, ice, 
rain, and hail concentrations should be provided.
    FAA Response: The FAA does not agree with Textron's recommendation. 
A special condition is not required to quantify ingestion threats. The 
FAA did not change this special condition as a result of this comment.
    Comment Summary: Airbus stated that while detailed means of 
compliance (test, analysis, etc.) need not be part of this special 
condition, the FAA should specify the ingestion conditions, such as 
icing environments, that magniX must consider in showing compliance.
    FAA Response: The FAA has changed final Special Condition no. 18 to 
require ingestion sources, that are not evaluated by magniX, to be 
declared in the engine installation manual.
    Comment Summary: Textron recommended that this special condition 
include a provision to prevent the accumulation of ferromagnetic 
material in the air-cooled passages, and to prevent blockages and short 
circuits between the rotor and the stator for non-sealed engines.
    FAA Response: The FAA does not agree with this comment. The special 
condition requires magniX to consider ingestion of material originating 
from outside the engine, not from within it. The potential for 
ferromagnetic contamination of engine bearings from sources within the 
engine would not likely meet the requirements established in these 
special conditions, such as Special Condition nos. 5 (Durability) and 7 
(Safety Analysis). The contamination is more likely a consequence of an 
engine failure or inadequate maintenance. The FAA made no changes to 
these special conditions as a result of this comment.
    Comment Summary: EASA stated rain conditions are a normal flight 
condition, even in VFR, and should be distinguished from other 
ingestion phenomena. EASA recommended incorporating EASA Special 
Condition E-18 issue 2: ``operation under rain conditions must not 
result in any abnormal operation (i.e., shutdown, power loss, erratic 
operation, power oscillations, failures . . .) throughout the EPU 
operating range.''
    FAA Response: The FAA has modified Special Condition no. 18 in 
response to this comment to require the magniX engine to operate safely 
in rain environments. The word ``rain'' was removed from Special 
Condition no. 18(a). The following special conditions were added: 
Special Condition no. 18(b), which provides that rain ingestion must 
not result in an abnormal operation such as shutdown, power loss, 
erratic operation, or power oscillations throughout the engine 
operating range, and Special Condition no. 18(d), which requires the 
applicant to declare, in the engine installation manual, ingestion 
sources that are not evaluated.
    Comment Summary: EASA asked the FAA to verify the proposed Special 
Condition no. 18 might result in a limitation that could be established 
at the aircraft-level for operation in icing conditions.
    FAA Response: These special conditions are not intended for all 
electric engine certification projects. They are intended for the 
magni350 and magni650 electric engines. magniX intends to pursue a type 
certificate for their electric engine. If magniX elects to omit likely 
sources of ingestion (foreign objects, birds, ice, hail) from their 
evaluations, Special Condition no. 18(d) requires magniX to declare 
ingestion sources that are not evaluated in the engine installation 
manual, except for rain. Special Condition no. 18(b) was added as a 
result of EASA's comment to implement performance requirements in

[[Page 53524]]

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 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 Sec. Sec.  33.5(a)(5) and 33.5(c) 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 33.83(f), Vibration test, instead of proposed 
Special Condition no. 20(b), 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 
Sec. Sec.  33.63, Vibration, and 33.83, Vibration test. Special 
Condition no. 20(a) corresponds to Sec.  33.63, Subpart E, which has 
provisions for the design and construction of the electric engine. 
Special Condition no. 20(b) corresponds to Sec.  33.83, Subpart F, 
which applies to the block tests. This Sec.  33.83, Vibration test, 
reference explains why a vibration survey is specified in Special 
Condition no. 20(b) and not in 20(a). In addition, 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 Wisk's 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 F3338-18, 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 33.83(b), 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. 20(a) corresponds to 14 CFR 33.63 in Subpart E, 
Design and Construction; Turbine Aircraft Engines, and Special 
Condition no. 20(b) corresponds to Sec.  33.83 in Subpart F, Block 
Tests; Turbine Aircraft Engines. TCCA's comment also relates to Special 
Condition no. 31, Operation with a variable pitch propeller, which 
corresponds to Sec.  33.95, Engine-propeller systems tests. As a result 
of TCCA's 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

[[Page 53525]]

shown not to result in a hazardous engine effect.''
    FAA Response: Special Condition no. 16 (Continued rotation) 
corresponds to 14 CFR 33.74, which precludes hazardous engine effects 
from continued rotation of engine main rotating systems after the 
engine is shut down for any reason while in flight. This includes the 
effects of vibration from failures that result in a rotor unbalance. 
Therefore, Special Condition no. 16 addresses the failure effects TCCA 
identified in their comment. The FAA did not change these special 
conditions as a result of this comment.
    Comment Summary: TCCA recommended requiring an evaluation of 
vibration effects that result from excitation forces caused by fault 
conditions or to address these effects by reference to experience with 
engine failures that did not result in a hazardous engine effect. TCCA 
also recommended addressing the vibration effects from sustained engine 
unbalance.
    FAA Response: Special Condition no. 16 (Continued rotation) 
precludes hazardous engine effects from continued rotation after the 
engine is shut down for any reason while in flight, including fault 
conditions. These special conditions are applicable to the magniX 
engines, which are new to aviation. Therefore, engine experience is not 
relevant to the magniX engine certification project. The FAA did not 
change this special condition as a result of this comment.

Special Condition No. 21, Overtorque

    The FAA proposed that Special Condition no. 21 would require magniX 
to demonstrate that the engine is capable of continuous operation 
without the need for maintenance if it experiences a certain amount of 
overtorque.
    Comment Summary: TCCA suggested that the FAA add the teardown 
inspection requirement of Special Condition no. 29 for each engine part 
or individual groups of components after conducting the overtorque 
test.
    FAA Response: The additional requirement suggested by TCCA 
corresponds to 14 CFR 33.84(a)(2), Engine overtorque test. The engines 
proposed by magniX may require a transient maximum overtorque rating. 
The FAA has changed final Special Condition no. 21 to require 
compliance to Special Condition no. 29 (Teardown inspection) after 
conducting an overtorque test.

Special Condition No. 22, Calibration Assurance

    The FAA received no comments for Special Condition no. 22, and it 
is adopted as proposed. It requires magniX to subject the engine to 
calibration tests, to establish its power characteristics and the 
conditions both before and after the endurance and durability 
demonstrations specified in proposed Special Condition nos. 23 and 26. 
The calibration test requirements specified in Sec.  33.85 only apply 
to the endurance test specified in Sec.  33.87, which is applicable 
only to turbine engines. The methods used for accomplishing those tests 
for turbine engines are not the best approach for electric engines. The 
calibration tests in Sec.  33.85 have provisions applicable to ratings 
that are not relevant to the magniX magni350 and magni650 model 
engines. Special Condition no. 22 allows magniX to demonstrate the 
endurance and durability of the electric engine either together or 
independently, whichever is most appropriate for the engine qualities 
being assessed. Consequently, this special condition applies the 
calibration requirement to both the endurance and durability tests.

Special Condition No. 23, Endurance Demonstration

    The FAA proposed that Special Condition no. 23 would require magniX 
to subject the engine to an endurance demonstration test, acceptable to 
the Administrator, to demonstrate the engine capabilities at the 
declared limits.
    The FAA proposed to evaluate the extent to which the test exposes 
the engine to failures that could occur when the engine is operated at 
its rated values, to determine if the test is sufficient to show that 
the engine design will not exhibit unacceptable effects in-service, 
such as significant performance deterioration, operability 
restrictions, and engine power loss or instability, when run for 
sustained periods at extreme operating conditions.
    Comment Summary: Rolls-Royce stated that the second sentence of the 
proposed special condition contained a typographical error and 
suggested that it should read, ``The endurance demonstration elevates 
and increases the engine's power settings, and dwells at the power 
settings for durations that produce the extreme physical conditions. . 
. .'' Rolls-Royce recommended replacing ``decreases'' with 
``increases'' in the special condition.
    FAA Response: Final Special Condition no. 23 has been changed. The 
FAA considered the change proposed by Rolls-Royce and changed the term 
``elevates'' to ``increases.''
    Comment Summary: TCCA recommended that the FAA add the following 
three sentences to Special Condition no. 23: (1) ``The severity of the 
demonstration should consider the design and intended use of the 
engine, and include the demonstration of safe operation under all 
operational limits to be applied during service operation of the 
engine.'' (2) ``When approval is sought for Normal Transient engine 
exceedances, it must be substantiated that the engine is capable of 
operation at the maximum engine transient condition of the affected 
engine parameter(s) without maintenance action.'' (3) ``When approval 
is sought for Inadvertent Transient engine exceedances, it must be 
substantiated that the engine is capable of operation at the maximum 
engine transient condition of the affected engine parameter(s) without 
maintenance action other than to correct any failure that led to the 
exceedances.''
    FAA Response: The FAA does not agree to include the additions 
recommended by TCCA. Regarding TCCA sentence (1), adding a definition 
for severity in this special condition is unnecessary because this 
special condition is intended to achieve the same objectives as 14 CFR 
33.87, Endurance test, but for the magniX electric engines. The test 
will be different for the magniX engines because those engines use 
electrical technology for propulsion. Whether the engine is turbine or 
electric, the endurance test achieves a severity that demonstrates the 
engine is safe to operate at its certificated limits.
    Regarding TCCA sentence (2), Special Condition no. 32 requires the 
engine and its components to be within serviceable limits, safe for 
continued operation, and capable of operating at declared ratings while 
remaining within limits upon completing all demonstrations and testing 
specified in these special conditions. If the magniX engine ratings 
include maximum transients, the engines must demonstrate that they 
operate safely during the maximum transients and meet the post-test 
engine requirements specified in these special conditions.
    Regarding TCCA sentence (3), Special Condition no. 23 is intended 
to assess the magniX engine's capabilities. It is not intended to show 
the engine can accommodate failures and malfunctions that lead to 
inadvertent transients that exceed the engine's certificated limits. 
Special Condition no. 17 (Safety analysis) addresses potential effects

[[Page 53526]]

from exceeding maximum limits and transients. Results from the safety 
analysis are used to decide how to manage the consequences of all 
failures that can reasonably be expected to occur.

Special Condition No. 24, Temperature Limit

    The FAA proposed that Special Condition no. 24 would require magniX 
to ensure the engine can endure operation at its temperature limits, 
plus an acceptable margin. An ``acceptable margin,'' as used in this 
special condition, is the amount of temperature above that required to 
prevent the least-capable engine allowed by the type design from 
failing due to temperature-related causes when operating at the most 
extreme thermal conditions.
    Comment Summary: Textron recommended that the FAA require the 
applicant to consider environmental conditions and that the engine 
temperature limit be substantiated at the worst-case environmental 
conditions to ensure the engine cooling system performance is adequate 
when the engine operates at the declared temperature limit.
    FAA Response: The FAA has changed final Special Condition no. 24 
with a requirement for magniX to account for operating environments 
when they establish a value for the engine temperature limit.
    Comment Summary: TCCA recommended that Special Condition no. 24 
include the following footnote: ``Acceptable margin, as used in the 
proposed special condition, is the amount of temperature above that 
required to prevent the least-capable engine allowed by the type design 
from failing due to temperature-related causes when operating at the 
most extreme thermal conditions.'' TCCA also recommended that Special 
Condition no. 24 includes: ``Upon completion of the demonstration, the 
engine must be within serviceable limits.''
    FAA Response: The FAA does not agree with this comment. The 
following special conditions already incorporate the technical criteria 
proposed by TCCA:
    Special Condition no. 1 requires magniX to comply with 14 CFR 33.8, 
Selection of engine power and thrust ratings, for the proposed engines. 
Section 33.8(b) requires that each selected rating must be for the 
lowest power or thrust that all engines of the same type may be 
expected to produce under the conditions used to determine that rating. 
This requirement will address the temperature margins required for the 
least (thermally) capable engine the type design allows.
    Special Condition no. 32(c) (General conduct of tests) has 
provisions that require the engine and its components to be within 
serviceable limits, safe for continued operation, and capable of 
operating at the declared ratings without exceeding limits after 
completing the tests identified in these special conditions.
    Special Condition no. 24 requires the engine design to demonstrate 
its capability to endure operation at its temperature limit plus an 
acceptable margin.
    Special Condition no. 12 (Stress analysis) includes a requirement 
for a thermal stress analysis to show a sufficient design margin to 
prevent unacceptable operating characteristics and hazardous engine 
effects.
    Therefore, Special Condition nos. 12, 24, 32(c), and Sec.  33.8 
address TCCA's recommendation. The FAA made no changes to the special 
condition as a result of the comment.
    Comment Summary: EASA commented that the temperature limit is a new 
requirement compared to the requirements in 14 CFR part 33, EASA CS-
E's,\11\ and the technical criteria in ASTM F3338-18. EASA stated that 
the applicant demonstrates operation up to the limits as part of the 
endurance test. EASA further commented that the engine's serviceability 
after the endurance test is sufficient proof that the engine has been 
designed and manufactured with margins compared to the limits declared 
in the engine installation manual. Therefore EASA recommended removing 
this requirement from this special condition.
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    FAA Response: The FAA does not agree with this comment. The FAA 
included a temperature limit because it is directly related to a 
primary failure mechanism associated with the novel technology used in 
magniX's proposed electric engine designs. The FAA did not change this 
special condition as a result of this comment.

Special Condition No. 25, Operation Demonstration

    The FAA proposed that Special Condition no. 25 would require that 
the engine demonstrate safe operating characteristics throughout its 
declared flight envelope and operating range. The engine performance 
data magniX will use to certify each engine must account for 
installation loads and effects.
    Comment Summary: Ampaire stated that the terminology used in the 
proposed special condition uses the term ``demonstration,'' and the 
term used in the ASTM document refers to the requirement as a ``test'' 
(ref. ASTM F3338-18, section 5.20.8).
    FAA Response: As used in these special conditions, a demonstration 
is a test, but the special condition also allows validated analysis to 
show compliance. A test is required to validate an analysis, so the 
requirement is always grounded in a test. The FAA made no changes to 
the special condition as a result of this comment.
    Comment Summary: Ampaire suggested that in-flight restart 
characteristics are a critical capability of electric engines and 
recommended that the FAA require this capability as part of the engine 
demonstration test. Airbus and TCCA also recommended that the FAA 
require a demonstration of in-flight restart capability. In addition, 
TCCA recommended that the special conditions require these 
demonstrations to be conducted with a representative propeller.
    FAA Response: The FAA does not agree with the comments. Engine in-
flight restart capabilities are established at the aircraft level in 
accordance with 14 CFR 23.2425(b), 25.903(e), 27.903(d), and 29.903(e). 
These regulations also require installed engines to have a restart 
capability within the aircraft's flight envelope. Therefore, a 
requirement for magniX to verify the in-flight restart capability of 
their engines during the engine certification program is not within the 
bounds of these special conditions. No changes were made to final 
Special Condition no. 25 as a result of this comment.
    Comment Summary: TCCA asked if a gearbox assembly is considered as 
a single ``part'' of the engine.
    FAA Response: A gearbox assembly is not considered to be a single 
part of the magniX engine. Gearboxes used in the magniX engines are 
treated as an engine accessory. The 14 CFR part 33 requirements imposed 
by Special Condition no. 1 that address engines with gearboxes and 
apply to magniX engines are 14 CFR 33.3, 33.5, 33.25, and Appendix 
A33.3. The special conditions that correspond to 14 CFR part 33 
requirements that address gearboxes used in the magniX engines are 
Special Condition nos. 2, 15, 20, 22, 23 and 26. No changes were made 
to these special conditions as a result of TCCA's comment.

Special Condition No. 26, Durability Demonstration

    The FAA proposed that Special Condition no. 26 would require magniX 
to subject the engine to a durability

[[Page 53527]]

demonstration. The durability demonstration must show that each part of 
the engine is designed and constructed to minimize any unsafe condition 
of the system between overhaul periods or between engine-replacement 
intervals if the overhaul is not defined.
    Comment Summary: TCCA commented that these special conditions do 
not contain a modified 14 CFR 33.4 description of ICA for the intended 
electric engine applications. TCCA suggested that ICA should represent 
all the instructions required for the magniX engines to remain 
airworthy, but that instructions for off-wing maintenance instructions 
in the ICA would not be appropriate.
    FAA Response: These special conditions are not intended for all 
electric engine certification projects. As required by Special 
Condition no. 1, magniX must comply with Sec.  33.4, Instructions for 
Continued Airworthiness, and its appendix. These requirements are 
appropriate to address the maintenance requirements for these proposed 
engine designs. The FAA made no changes to the special condition as a 
result of the comment.
    Comment Summary: TCCA recommended adding 14 CFR 33.19(b), Propeller 
pitch control design requirements, to Special Condition no. 26, with an 
opt-out option if the magniX engines do not have propeller-blade pitch 
control systems.
    FAA Response: These special conditions apply to the magni350 and 
magni650 model engines. These magniX engines do not have a propeller-
blade pitch control system. The FAA made no changes to the special 
condition as a result of the comment.
    Comment Summary: TCCA recommended revising this special condition 
to state, ``The engine must be subjected to a durability demonstration 
to show that each part of the engine has been designed and constructed 
to minimize any unsafe condition of the system and subsystem between 
overhaul periods or between engine components/parts replacement 
intervals. . . .''
    FAA Response: magniX's proposed engines must meet Special Condition 
no. 29 (Teardown inspection) requirements after completing the 
durability demonstration specified in this special condition. In 
addition, magniX must meet the requirements of Special Condition no. 32 
(General conduct of tests). These special conditions, in combination 
with the demonstration tests required by these magniX special 
conditions, achieve the objectives identified by this comment. The FAA 
made no changes to the special condition as a result of the comment.
    Comment Summary: TCCA suggested that the FAA modify Special 
Condition no. 26 in a manner that results in the following revision: 
``This test must simulate the conditions in which the engine is 
expected to operate in-service, including typical start-stop cycles and 
scheduled maintenance actions and must be of sufficient duration in 
order to provide confidence in the durability of the engine.''
    FAA Response: The FAA does not agree with the comment. The required 
durability demonstration provides information for compliance to 14 CFR 
33.4, Instructions for continued airworthiness, which is imposed by 
Special Condition no. 1. If maintenance is required to complete the 
test, the specific maintenance actions could become part of the 
mandatory ICA. The discussion for Special Condition no. 32 contains 
more information about maintenance conducted during a test. Special 
Condition no. 32 (General conduct of tests) has criteria that permit 
some maintenance to be accomplished during the test without incurring 
additional mandatory ICA. The FAA agrees that the test duration can 
provide confidence in the engine's durability. However, whether the 
test duration is long or short, magniX will develop a maintenance plan 
based on the test that magniX creates for their program, in accordance 
with Sec.  33.4. The FAA made no changes to the special condition as a 
result of the comment.

Special Condition No. 27, System and Component Tests

    The FAA proposed that Special Condition no. 27 would require magniX 
to show that the engine's systems and components would perform their 
intended functions in all declared engine environments and operating 
conditions.
    Comment Summary: TCCA recommended that the FAA require magniX to 
establish temperature limits for each component that requires 
temperature-controlling provisions in the aircraft installation to 
assure satisfactory functioning, reliability, and durability.
    FAA Response: Other special conditions address TCCA's concern. 
Special Condition no. 2 (Engine ratings and operating limits) requires 
magniX to establish a temperature limit that is necessary for safe 
operation of the engine. Whether or not a temperature limit is 
established for a component depends on the outcome of Special Condition 
no. 17 (Safety analysis), which examines the consequence of engine 
failure from high-temperature. If cooling is required to satisfy 
Special Condition no. 17 (Safety analysis), the cooling system 
monitoring features and usage are documented in accordance with Sec.  
33.5(c), Safety analysis instructions. The FAA did not change this 
special condition as a result of this comment.
    Comment Summary: TCCA recommended that the FAA require magniX to 
establish voltage and current limits ``for each component that requires 
voltage or current controlling provisions, or both, in the aircraft 
installation to assure satisfactory functioning, reliability, and 
durability.''
    FAA Response: Other special conditions address TCCA's concern. 
Regarding voltage and current limits, Special Condition no. 2 requires 
magniX to establish ratings and operating limitations based on power-
supply requirements for the engine. Whether or not voltage and current 
limits are established for a component depends on the outcome of 
Special Condition no. 17 (Safety analysis), which examines the 
consequence of the component's failure from high temperature. The FAA 
did not change this special condition as a result of this comment.

Special Condition No. 28, Rotor Locking Demonstration

    The FAA proposed that Special Condition no. 28 would require the 
engine to demonstrate reliable rotor locking performance and that no 
hazardous engine effects will occur if the engine uses a rotor locking 
device to prevent shaft rotation.
    Comment Summary: Wisk stated that this special condition does not 
contain a requirement that ensures the rotor lock feature cannot be 
enabled with a motor power set and also that its inadvertent activation 
is sufficiently unlikely that no major engine effect can occur. Wisk 
recommended that the FAA clarify if the term ``hazardous'' is being 
used in the context of system safety or in general terms.
    Textron also requested that the FAA clarify the definition of 
``hazardous effects'' and use that term consistently and recommended 
the following be added to Special Condition no. 28: ``. . . that no 
hazardous effects as specified in Special Condition no. 17(d)(2) will 
occur.''
    FAA Response: If magniX implements a rotor locking device in their 
engine design, Special Condition no. 28 will ensure the device exhibits 
reliable rotor locking performance and will not cause hazardous engine 
effects to preserve system safety. Special Condition no. 17 (Safety 
analysis) examines the

[[Page 53528]]

consequence of accidental rotor locking while the aircraft is in-flight 
and classifies the failure as either hazardous or major. The magniX 
engine will need to meet the requirements of this special condition and 
those of the safety analysis, which provide protection from inadvertent 
rotor locking.
    The FAA clarified the terms ``hazardous'' and ``hazardous engine 
effects'' as they are used in Special Condition no. 28 by adding a 
reference to Special Condition no. 17(d)(2). The FAA changed final 
Special Condition no. 28 as a result of this comment.
    Comment Summary: Textron requested that Special Condition no. 28 
require magniX to consider the potential hazards from an automatic 
rotor locking system. Textron stated that if the engine is shut down 
during flight, and the locking device is automatic, the flight crew 
needs to have a means to remove the locking device and restart the 
engine without creating a hazard. The commenter recommended adding the 
following to Special Condition no. 28: ``(b) When the locking device is 
in place, an indication shall be provided so that the crew will be able 
to retract the device while in flight.''
    FAA Response: The FAA does not agree with the comment. magniX 
verifies rotor lock performance and reliability using the tests 
required by Special Condition no. 28. Typically, only rotorcraft have 
cockpit indications for locking devices. Those rotorcraft cockpit 
indications for locking devices are for main rotor transmissions, which 
are aircraft-level components. If an engine lock position indication is 
required to meet the aircraft safety objectives, the devices that 
notify the crew are part of the aircraft safety system. The FAA did not 
change these special conditions as a result of this comment.
    Comment Summary: TCCA commented that this special condition should 
allow additional techniques to verify rotor locking performance. TCCA 
also suggested that the special condition requires a demonstration of 
reliable rotor ``unlocking'' performance.
    FAA Response: Final Special Condition no. 28 has been changed to 
add rotor unlocking performance to the demonstration. However, allowing 
the use of a validated analysis would render the demonstration 
optional.

Special Condition No. 29, Teardown Inspection

    The FAA proposed that Special Condition no. 29 would require magniX 
to perform either a teardown evaluation or a non-teardown evaluation 
based on the criteria of Special Condition no. 29(a) or (b).
    The FAA proposed that Special Condition no. 29(a) would require 
that the engine be disassembled after the endurance and durability 
demonstrations to verify each component remained within its service 
limits and in a condition for continued operation in accordance with 
Sec.  33.4, Instructions for Continued Airworthiness.
    The FAA proposed that Special Condition no. 29(b) would require 
magniX, for ``non-teardown evaluations,'' to establish life limits 
based on endurance and durability demonstrations.
    In final Special Condition no. 29(b), magniX is required, for non-
teardown evaluations, to account for engines, sub-assemblies, and 
components that cannot be disassembled without destroying the 
components. If teardown and inspection are not accomplished for 
components or assemblies after testing, the maintenance requirements 
for the engine are contingent on the demonstrated capabilities 
exhibited during the certification tests.
    Comment Summary: GE recommended that the FAA clarify how life 
limits will be established if magniX cannot complete the teardown 
inspection of parts or components after the endurance and durability 
demonstrations. GE stated that the life limits should be documented in 
the engine's airworthiness limitations or the engine's ICA. TCCA also 
requested clarification about how life limits are established for parts 
and components that are not torn down after testing.
    FAA Response: Special Condition no. 29 can have an effect on life 
limits. In the foregoing discussion of this condition, the FAA provided 
additional information to clarify how maintenance (such as life limits) 
is established for parts and components that are not torn down and 
inspected after testing. Also, the FAA changed final Special Condition 
no. 29 to require life limits resulting from this special condition to 
be documented in the ICA, in accordance with 14 CFR 33.4.
    Comment Summary: Textron recommended that the FAA require 
inspections of electrical components in the controller after the 
endurance and durability demonstrations. Textron stated that, at a 
minimum, the FAA should require inspection of the controller's 
fasteners, heat transfer components, dissimilar metallic junctions, and 
age or use affected electrical components.
    FAA Response: The preamble of these special conditions explains 
that the magniX engine consists of an electric motor, controller, and 
high-voltage systems. Special Condition no. 29(a) requires the engine 
to be completely torn down and inspected. Special Condition no. 29(b) 
contains provisions for engine components that are not disassembled for 
inspection. The FAA did not change these special conditions as a result 
of this comment.
    Comment Summary: An individual commenter suggested potential long-
term issues with main bearing lubrication related to grease life. The 
commenter stated that these issues might not be evident after 
completing a certification program.
    FAA Response: In response to this comment, the FAA has changed 
final Special Condition no. 29(b) to require a life limit for the 
bearing lubricant if the bearing is not disassembled after testing. The 
FAA has changed the special condition as a result of this comment.
    Comment Summary: TCCA recommended that the FAA mandate additional 
tests if the teardown inspection shows that part replacement is 
necessary.
    FAA Response: The FAA does not concur with the comment. Special 
Condition nos. 32(b) and (b)(4) (General conduct of tests) already have 
the requested provisions for additional testing of parts that require 
replacement during a test or based on their condition at teardown 
inspection. The FAA made no changes to the special condition as a 
result of the comment.
    Comment Summary: EASA commented that this Special Condition no. 
29(b) was proposed to define the life limits of the tested components 
based on the endurance and durability tests. EASA stated this special 
condition was not aligned with ASTM F3338-18 and asked the FAA to 
elaborate on whether the selected limit is the highest or lowest one 
and how limits are compared if they are based on different test 
conditions.
    FAA Response: ASTM F3338-18, section 5.22.1.5 establishes life 
limits for an electric engine based on the length of an endurance test 
if the engine is not torn down for inspection after the test. These 
special conditions require individual life limits to be established, 
based on endurance and durability demonstrations if individual 
components are not torn down and inspected after the tests. This 
special condition is consistent with the ASTM document EASA referenced 
in their comment. Because these special conditions apply to the magniX 
engine, the life limits will be based on the test conditions magniX 
uses to assess their engines. The FAA made no changes to

[[Page 53529]]

the special condition as a result of the comment.
    Comment Summary: TCCA recommended that Special Condition no. 29 
apply the non-teardown requirement to those components that need 
additional testing in accordance with Sec. Sec.  33.53(a), Engine 
system and component tests or 33.91(a), Engine system and component 
tests. TCCA commented that, as the special condition is currently 
worded, some might apply the requirement only to internal engine parts. 
TCCA also requested that the FAA modify the special condition to 
require some post-test assessments for non-torn down components. TCCA 
also asked that the FAA clarify the requirement that ``then the life 
limits for these components must be established based on the endurance 
and durability demonstrations.'' TCCA contended that, as this 
requirement is currently worded, magniX could interpret it to mean that 
all internal parts of the electric engine would not need to be 
examined, including (Non-Destructive Testing) NDT, especially if there 
is no overhaul.
    FAA Response: Special Condition no. 27 ensures that magniX 
addresses electric engine components that cannot be torn down for 
inspection. If the condition of these parts is questionable, then the 
requirements in Special Condition nos. 32(b) and 32(b)(4) can be 
applied for additional data to substantiate the life limit. These 
special conditions address TCCA's comments. The FAA did not change the 
special condition as a result of this comment.

Special Condition No. 30, Containment

    The FAA proposed that Special Condition no. 30 would require the 
engine to provide containment features that protect against likely 
hazards from rotating components, unless magniX can show, by test or 
validated analysis, that the margin to rotor burst does not justify the 
need for containment features. The intent of this special condition is 
to prevent hazardous engine effects from structural failure of rotating 
components and the rotating parts that are built into them.
    Comment Summary: Textron stated that the wording in Special 
Condition no. 30(a) relating to the required burst margin for the rotor 
is vague. Textron suggested that the FAA incorporate the following 
change to Special Condition no. 30(a): ``The design of the case 
surrounding rotating components must provide for the containment of the 
rotating components in the event of failure unless the applicant shows 
that the margin to rotor burst unconditionally rules out the 
possibility of a rotor burst.''
    FAA Response: The FAA agrees with the proposed change and has 
modified Special Condition no. 30(a) to incorporate Textron's 
suggestion.
    Comment Summary: Airbus stated that experience with electrical 
generators has shown that axial ejection of debris might induce severe 
damage to surroundings. Airbus stated that an axial containment 
demonstration is feasible for electric engines and generators, and 
therefore should be required by the FAA. Airbus said that this special 
condition should require magniX to show full containment capability, 
eliminating the need to identify forward- and aft-ejected debris in the 
engine installation manual. Airbus recommended that the FAA modify 
Special Condition no. 30(a) to state, ``The design of the engine must 
provide for axial and radial containment of the rotating components . . 
.'' Airbus also recommended the FAA modify Special Condition no. 30(b) 
to state, ``If the margin to burst shows the case must have containment 
features in the event of failure, the case must provide axial and 
radial containment of the failed rotating components.''
    FAA Response: These special conditions apply only to the magniX 
engine designs. Special Condition no. 30(b) is similar to Sec.  
33.94(a), Blade containment and rotor unbalance tests, and Sec.  
33.19(a), Durability, except this special condition includes the engine 
rotors. This special condition allows magniX to approach containment 
like turbine engines or provide full containment, as suggested in the 
comment. If a magniX engine design cannot contain the rotors, life 
limits will be applied in accordance with Special Condition no. 13 
(Critical and life-limited parts). Therefore the FAA did not change 
this special condition as a result of this comment.
    Comment Summary: EASA stated that the intent of the proposed 
Special Condition no. 30(b) is not clear, since that paragraph requests 
the case to provide containment of the failed rotating component while 
requesting that the applicant define the energy level, the trajectory, 
and the size of the released fragments. EASA asked the FAA to rewrite 
Special Condition no. 30(b) to be differentiated from Special Condition 
no. 30(a). EASA commented that Special Condition no. 30(b) should be 
dedicated to those cases where containment is not ensured.
    FAA Response: Special Condition no. 30(b) provides a level of 
protection similar to that provided by FAA regulations that manage 
turbine engine blade failures, except it includes the engine rotors. It 
precludes the release of high-energy debris radially outward of the 
rotors. If the magniX engines qualify for the provisions in Special 
Condition no. 30(b), fragments resulting from rotor damage, and that 
travel forward or aft of the containment plane, must have their energy 
levels and trajectories defined. The magniX engine configuration and 
declared containment capabilities would determine if compliance with 
Special Condition no. 30(b) is required. The FAA made no change to this 
special condition as a result of this comment.

Special Condition No. 31, Operation With a Variable Pitch Propeller

    The FAA proposed that Special Condition no. 31 would require magniX 
to conduct functional demonstrations, including feathering, negative 
torque, negative thrust, and reverse thrust operations, as applicable, 
based on the propeller or fan's variable pitch functions that are 
planned for use on these electric engines, with a representative 
propeller. Also, since these electric engines may be installed with a 
variable pitch propeller, the special condition associated with the 
operation with a variable pitch propeller or fan is necessary.
    Comment Summary: TCCA commented that, in addition to the propeller 
control, there is a risk that an electric engine controller could fail 
and result in reverse engine rotation. TCCA suggested that the FAA add 
a special condition that considers and minimizes the potential for 
engine controller failures that could result in reverse engine 
rotation.
    FAA Response: The FAA does not agree with the comment. Section 
33.75(g)(2) provides a list of hazardous engine effects. The list 
includes thrust in the opposite direction. Special Condition no. 
17(d)(2) defines hazardous engine effects as those in Sec.  
33.75(g)(2), with several additions specifically applicable to these 
electric engines. These special conditions address the failure 
described in the comment.
    Comment Summary: TCCA recommended revising the Special Condition 
no. 31 text to read, ``. . . with a representative propeller or fan. 
These demonstrations may be conducted in a manner acceptable to the 
Administrator as part . . .''.
    FAA Response: The FAA has modified final Special Condition no. 31 
to allow the Administrator to determine if a test is acceptable.

[[Page 53530]]

Special Condition No. 32, General Conduct of Tests

    The FAA proposed that Special Condition no. 32 would require magniX 
to (1) include scheduled maintenance in the engine ICA before 
certification; (2) include any maintenance, in addition to the 
scheduled maintenance, that was needed during the test to satisfy the 
requirement; and (3) conduct additional tests that the Administrator 
finds necessary, warranted by the test results.
    The term ``excessive,'' as it is used in proposed Special Condition 
nos. 32(b)(1) and (2), describes the frequency of unplanned engine 
maintenance and the frequency of unplanned test stoppages that are 
needed to address engine issues that prevent the engine from completing 
the tests. Deciding if unplanned maintenance or test stoppages are 
excessive requires an objective assessment of the reasons for the test 
interruptions. For example, magniX may not be able to simulate a 
realistic engine operating environment and may need to integrate test-
enabling equipment to achieve the test goals. The test facility 
equipment may fail or cause an engine to fail during a test. Therefore, 
unplanned maintenance might not affect the certification test results, 
but if the FAA considers the maintenance or test stoppages to be 
``excessive,'' additional testing or unforeseen ICA may be required to 
comply with the certification requirements.
    Comment Summary: Rolls-Royce stated that it supports the 
clarifications in Special Condition no. 32(b) with the understanding 
that the term ``excessive'' in Special Condition nos. 32(b)(1) and 
32(b)(2) allows for the rectification of some failures while the test 
continues. Rolls-Royce suggested that aircraft engines that operate 
using aviation fuel, operating at the extreme physical conditions 
required by the endurance tests, sometimes suffer a failure that is 
unrelated to the test conditions. The ability to review the failure 
with the FAA, rectify the failure, and continue the test is an 
important aspect of conducting these tests.
    FAA Response: The FAA's assessment of whether unplanned service and 
maintenance during testing are ``excessive'' could include a variety of 
factors, such as the causes of the stoppage, the effects of test 
facility equipment, difficulties in simulating a realistic engine 
operating environment, and whether the engine requires modifications to 
complete the test. The applicant could also show that unplanned 
maintenance did not affect the certification test results. The FAA did 
not change this special condition as a result of this comment.
    Comment Summary: TCCA commented that these special conditions do 
not address the emerging issue of single event effects, which the FAA 
is currently addressing via issue papers. TCCA recommended 
incorporating those issue papers into the special condition.
    FAA Response: The FAA does not agree with the comment. The issue 
paper that TCCA referenced is applicable to engines that operate at 
high altitudes and high latitudes. Special Condition nos. 10 and 17 
require magniX to account for the intended aircraft application. If 
magniX engines can operate at high altitudes and high latitudes, they 
could apply the referenced issue paper to the certification program. 
The FAA made no changes to these special conditions as a result of this 
comment.
    Comment Summary: TCCA recommended that the FAA clarify the 
requirement in Special Condition no. 32(a) by including a reference to 
14 CFR 33.4, Instructions for continued airworthiness.
    FAA Response: The FAA has modified the special condition to add the 
requested reference to Sec.  33.4 to clarify that magniX must provide 
the service and maintenance instructions in accordance with the ICA.

Applicability

    As discussed above, these special conditions are applicable to the 
magniX magni350 and magni650 Model engines. Should magniX apply at a 
later date for a change to the type certificate to include another 
model on the same type certificate incorporating the same novel or 
unusual design feature, these special conditions would apply to that 
model as well.

Conclusion

    This action affects only magniX magni350 and magni650 model 
engines. It is not a rule of general applicability.

List of Subjects in 14 CFR Part 33

    Aircraft, Aviation safety, Reporting and recordkeeping 
requirements.

Authority Citation

    The authority citation for these special conditions is as follows:

    Authority: 49 U.S.C. 106(f), 106(g), 40113, 44701, 44702, 44704.

The Special Conditions

    Accordingly, pursuant to the authority delegated to me by the 
Administrator, the following special conditions are issued as part of 
the type certification basis for magniX USA, Inc., (magniX), magni350 
and magni650 model engines. The applicant must also comply with the 
certification procedures set forth in title 14, Code of Federal 
Regulations (14 CFR) part 21.

1. Applicability

    Unless otherwise noted in these special conditions, the design must 
comply with the airworthiness standards for aircraft engines set forth 
in 14 CFR part 33, except those airworthiness standards specifically 
and explicitly applicable only to reciprocating and turbine aircraft 
engines.

2. Engine Ratings and Operating Limits

    In addition to Sec.  33.7(a), the design must comply with the 
following:
    Ratings and operating limits must be established and included in 
the type certificate data sheet based on:
    (a) Shaft power, torque, rotational speed, and temperature for:
    (1) Rated takeoff power;
    (2) Rated maximum continuous power; and
    (3) Rated maximum temporary power and associated time limit.
    (b) Duty Cycle and the rating at that duty cycle. The duty cycle 
must be declared in the engine type certificate data sheet.
    (c) Cooling fluid grade or specification.
    (d) Power-supply requirements.
    (e) Any other ratings or limitations that are necessary for the 
safe operation of the engine.

3. Materials

    The engine design must comply with 14 CFR 33.15.

4. Fire Protection

    The engine design must comply with 14 CFR 33.17.
    In addition, high-voltage electrical wiring interconnect systems 
must be protected against arc faults. Any non-protected electrical 
wiring interconnects must be analyzed to show that arc faults do not 
cause a hazardous engine effect.

5. Durability

    The engine design and construction must minimize the development of 
an unsafe condition of the engine between maintenance intervals, 
overhaul periods, or mandatory actions described in the applicable 
Instructions for Continued Airworthiness (ICA).

6. Engine Cooling

    The engine design and construction must comply with Sec.  33.21. In 
addition, if cooling is required to satisfy the safety

[[Page 53531]]

analysis as described in Special Condition no. 17, the cooling system 
monitoring features and usage must be documented in the engine 
installation manual.

7. Engine-Mounting Attachments and Structure

    The engine-mounting attachments and related engine structures must 
comply with 14 CFR 33.23.

8. Accessory Attachments

    The engine must comply with 14 CFR 33.25.

9. Overspeed

    (a) A rotor overspeed must not result in a burst, rotor growth, or 
damage that results in a hazardous engine effect, as defined in Special 
Condition no. 17(d)(2). Compliance with this paragraph must be shown by 
test, validated analysis, or a combination of both. Applicable assumed 
rotor speeds must be declared and justified.
    (b) Rotors must possess sufficient strength with a margin to burst 
above certified operating conditions and above failure conditions 
leading to rotor overspeed. The margin to burst must be shown by test, 
validated analysis, or a combination thereof.
    (c) The engine must not exceed the rotor speed operational 
limitations that could affect rotor structural integrity.

10. Engine Control Systems

    (a) Applicability.
    The requirements of this special condition apply to any system or 
device that is part of the engine type design, that controls, limits, 
monitors, or protects engine operation and is necessary for the 
continued airworthiness of the engine.
    (b) Engine control.
    The engine control system must ensure the engine does not 
experience any unacceptable operating characteristics or exceed its 
operating limits, 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, 
if applicable.
    (c) Design assurance.
    The software and complex electronic hardware, including 
programmable logic devices, must be--
    (1) Designed and developed using a structured and systematic 
approach that provides a level of assurance for the logic commensurate 
with the hazard associated with the failure or malfunction of the 
systems in which the devices are located; and
    (2) Substantiated by a verification methodology acceptable to the 
Administrator.
    (d) Validation.
    All functional aspects of the control system must be substantiated 
by test, analysis, or a combination thereof, to show that the engine 
control system performs the intended functions throughout the declared 
operational envelope.
    (e) Environmental limits.
    Environmental limits that cannot be adequately substantiated by 
endurance demonstration, validated analysis, or a combination thereof 
must be demonstrated by the system and component tests in Special 
Condition no. 27.
    (f) Engine control system failures.
    The engine control system must--
    (1) Have a maximum rate of Loss of Power Control (LOPC) that is 
suitable for the intended aircraft application;
    (2) When in the full-up configuration, be single fault tolerant, as 
determined by the Administrator, for electrical, electrically 
detectable, and electronic failures involving LOPC events;
    (3) Not have any single failure that results in hazardous engine 
effects; and
    (4) Not have any likely failure or malfunction that lead to local 
events in the intended aircraft application.
    (g) System safety assessment.
    The applicant must perform a system safety assessment. This 
assessment must identify faults or failures that affect normal 
operation, together with the predicted frequency of occurrence of these 
faults or failures. The intended aircraft application must be taken 
into account to assure the assessment of the engine control system 
safety is valid.
    (h) Protection systems.
    The engine control devices and systems' design and function, 
together with engine instruments, operating instructions, and 
maintenance instructions, must ensure that engine operating limits will 
not be exceeded in-service.
    (i) Aircraft-supplied data.
    Any single failure leading to loss, interruption, or corruption of 
aircraft-supplied data (other than power command signals from the 
aircraft), or aircraft-supplied data shared between engine systems 
within a single engine or between fully independent engine systems, 
must--
    (1) Not result in a hazardous engine effect, as defined in Special 
Condition no. 17(d)(2), for any engine installed on the aircraft; and
    (2) Be able to be detected and accommodated by the control system.
    (j) Engine control system electrical power.
    (1) The engine control system must be designed such that the loss, 
malfunction, or interruption of the control system electrical power 
source will not result in a hazardous engine effect, as defined in 
Special Condition no. 17(d)(2), the unacceptable transmission of 
erroneous data, or continued engine operation in the absence of the 
control function. The engine control system must be capable of resuming 
normal operation when aircraft-supplied power returns to within the 
declared limits.
    (2) The applicant must identify and declare, in the engine 
installation manual, the characteristics of any electrical power 
supplied from the aircraft to the engine control system for starting 
and operating the engine, including transient and steady-state voltage 
limits, and any other characteristics necessary for safe operation of 
the engine.

11. Instrument Connection

    The applicant must comply with 14 CFR 33.29(a), (e), and (g).
    (a) In addition, as part of the system safety assessment of Special 
Condition no. 10(g), the applicant must assess the possibility and 
subsequent effect of incorrect fit of instruments, sensors, or 
connectors. Where practicable, the applicant must take design 
precautions to prevent incorrect configuration of the system.
    (b) The applicant must provide instrumentation enabling the flight 
crew to monitor the functioning of the engine cooling system unless 
evidence shows that:
    (1) Other existing instrumentation provides adequate warning of 
failure or impending failure;
    (2) Failure of the cooling system would not lead to hazardous 
engine effects before detection; or
    (3) The probability of failure of the cooling system is extremely 
remote.

12. Stress Analysis

    (a) A mechanical, thermal, and electromagnetic stress analysis must 
show a sufficient design margin to prevent unacceptable operating 
characteristics and hazardous engine effects.
    (b) Maximum stresses in the engine must be determined by test, 
validated analysis, or a combination thereof and must be shown not to 
exceed minimum material properties.

13. Critical and Life-Limited Parts

    (a) The applicant must show, by a safety analysis or means 
acceptable to the Administrator, whether rotating or moving components, 
bearings, shafts,

[[Page 53532]]

static parts, and non-redundant mount components should be classified, 
designed, manufactured, and managed throughout their service life as 
critical or life-limited parts.
    (1) Critical part means a part that must meet prescribed integrity 
specifications to avoid its primary failure, which is likely to result 
in a hazardous engine effect as defined in Special Condition no. 
17(d)(2) of these special conditions.
    (2) Life-limited part means a rotor and major structural static 
part, the failure of which can result in a hazardous engine effect due 
to low-cycle fatigue (LCF) mechanism or any LCF driven mechanism 
coupled with creep. A life limit is an operational limitation that 
specifies the maximum allowable number of flight cycles that a part can 
endure before the applicant must remove it from the engine.
    (b) In establishing the integrity of each critical part or life-
limited part, the applicant must provide to the Administrator the 
following three plans for approval:
    (1) An engineering plan that establishes and maintains that the 
combination of loads, material properties, environmental influences, 
and operating conditions, including the effects of engine parts 
influencing these parameters, are sufficiently well-known and 
predictable by validated analysis, test, or service experience. The 
engineering plan must ensure each critical part or life-limited part is 
withdrawn from service at an approved life before hazardous engine 
effects can occur. The engineering plan must establish activities to be 
executed both pre- and post-certification. In addition to the 
activities that must be completed prior to certification, including a 
reporting system that flows, back to magniX, problematic issues that 
develop in engines while they operate in-service, to be addressed by 
the design process. magniX must perform appropriate damage-tolerance 
assessments to address the potential for failure from material, 
manufacturing, and service-induced anomalies within the approved life 
of the part. The approved life must be published in the mandatory ICA.
    (2) A manufacturing plan that identifies the specific manufacturing 
definition (drawings, procedures, specifications, etc.) necessary for 
the manufacturer to consistently produce critical or life-limited parts 
with the design attributes required by the engineering plan.
    (3) A service-management plan defines in-service processes for 
maintenance and repair of critical or life-limited parts that maintain 
attributes consistent with those required by the engineering plan. 
These processes must be part of the mandatory ICA.

14. Lubrication System

    (a) The lubrication system must be designed and constructed to 
function properly between scheduled maintenance intervals in all flight 
attitudes and atmospheric conditions in which the engine is expected to 
operate.
    (b) The lubrication system must be designed to prevent 
contamination of the engine bearings and lubrication system components.
    (c) The applicant must demonstrate by test, validated analysis, or 
a combination thereof, the unique lubrication attributes and functional 
capability of (a) and (b).

15. Power Response

    The design and construction of the engine, including its control 
system, must enable an increase--
    (a) From the minimum power setting to the highest-rated power 
without detrimental engine effects;
    (b) From the minimum obtainable power while in-flight and while on 
the ground to the highest-rated power within a time interval determined 
to be safe for aircraft operation; and
    (c) From the minimum torque to the highest-rated torque without 
detrimental engine or aircraft effects to ensure aircraft structural 
integrity or aircraft aerodynamic characteristics are not exceeded.

16. Continued Rotation

    If the design allows any of the engine main rotating systems to 
continue to rotate after the engine is shut down while in-flight, this 
continued rotation must not result in any hazardous engine effects, as 
specified in Special Condition no. 17(d)(2).

17. Safety Analysis

    (a) The applicant must comply with Sec.  33.75(a)(1) and (a)(2) 
using the failure definitions in Special Condition no. 17(d).
    (b) If the failure of such elements is likely to result in 
hazardous engine effects, then the applicant may show compliance by 
reliance on the prescribed integrity requirements such as Sec.  33.15, 
Special Condition no. 9, Special Condition no. 13, or combinations 
thereof, as applicable. The failure of such elements and associated 
prescribed integrity requirements must be stated in the safety 
analysis.
    (c) The applicant must comply with Sec.  33.75(d) and (e) using the 
failure definitions in Special Condition no. 17(d) of these special 
conditions.
    (d) Unless otherwise approved by the Administrator, the following 
definitions apply to the engine effects when showing compliance with 
this condition:
    (1) A minor engine effect does not prohibit the engine from meeting 
its certificated performance requirements and the intended functions in 
a manner consistent with Sec.  33.28(b)(1)(i), Sec.  33.28(b)(1)(iii) 
and Sec.  33.28 (b)(1)(iv), and the engine complies with the 
operability requirements such as Special Condition no. 15 (Power 
response), Special Condition no. 25 (Operation demonstration), and 
Special Condition no. 31 (Operation with a variable pitch propeller), 
as appropriate.
    (2) The engine effects in Sec.  33.75(g)(2) are hazardous engine 
effects with the addition of:
    (i) Electrocution of the crew, passengers, operators, maintainers, 
or others; and
    (ii) Blockage of cooling systems that are required for the engine 
to operate within temperature limits.
    (3) Any other engine effect is a major engine effect.
    (e) The intended aircraft application must be taken into account to 
assure the analysis of the engine system safety is valid.

18. Ingestion

    (a) Ingestion from likely sources (foreign objects, birds, ice, 
hail) must not result in hazardous engine effects defined by Special 
Condition no. 17(d)(2), or unacceptable power loss.
    (b) Rain ingestion must not result in an abnormal operation such as 
shutdown, power loss, erratic operation, or power oscillations 
throughout the engine operating range.
    (c) If the design of the engine relies on features, attachments, or 
systems that the installer may supply, for the prevention of 
unacceptable power loss or hazardous engine effects following potential 
ingestion, then the features, attachments, or systems must be 
documented in the engine installation manual.
    (d) Ingestion sources that are not evaluated must be declared in 
the engine installation manual.

19. Liquid Systems

    (a) Each liquid system used for lubrication or cooling of engine 
components must be designed and constructed to function properly in all 
flight attitudes and atmospheric conditions in which the engine is 
expected to operate.
    (b) If a liquid system used for lubrication or cooling of engine 
components is not self-contained, the

[[Page 53533]]

interfaces to that system must be defined in the engine installation 
manual.
    (c) The applicant must establish by test, validated analysis, or a 
combination of both that all static parts subject to significant gas or 
liquid pressure loads will not:
    (1) Exhibit permanent distortion beyond serviceable limits or 
exhibit leakage that could create a hazardous condition when subjected 
to normal and maximum working pressure with margin.
    (2) Exhibit fracture or burst when subjected to the greater of 
maximum possible pressures with margin.
    (d) Compliance with Special Condition no. 19(c) must take into 
account:
    (1) The operating temperature of the part;
    (2) Any other significant static loads in addition to pressure 
loads;
    (3) Minimum properties representative of both the material and the 
processes used in the construction of the part; and
    (4) Any adverse physical geometry conditions allowed by the type 
design, such as minimum material and minimum radii.
    (e) Approved coolants and lubricants must be listed in the engine 
installation manual.

20. Vibration Demonstration

    (a) The engine must be designed and constructed to function 
throughout its normal operating range of rotor speeds and engine output 
power, including defined exceedances, without inducing excessive stress 
in any engine parts because of vibration and without imparting 
excessive vibration forces to the aircraft structure.
    (b) Each engine design must undergo a vibration survey to establish 
that the vibration characteristics of those components that may be 
subject to induced vibration are acceptable throughout the declared 
flight envelope and engine operating range for the specific 
installation configuration. The possible sources of the induced 
vibration that the survey must assess are mechanical, aerodynamic, 
acoustical, or electromagnetic. This survey must be shown by test, 
validated analysis, or a combination thereof.

21. Overtorque

    When approval is sought for a transient maximum engine overtorque, 
the applicant must demonstrate by test, validated analysis, or a 
combination thereof, that the engine can continue operation after 
operating at the maximum engine overtorque condition without 
maintenance action. Upon conclusion of overtorque tests conducted to 
show compliance with this special condition, or any other tests that 
are conducted in combination with the overtorque test, each engine part 
or individual groups of components must meet the requirements of 
Special Condition no. 29.

22. Calibration Assurance

    Each engine must be subjected to calibration tests to establish its 
power characteristics and the conditions both before and after the 
endurance and durability demonstrations specified in Special Conditions 
nos. 23 and 26.

23. Endurance Demonstration

    The applicant must subject the engine to an endurance 
demonstration, acceptable to the Administrator, to demonstrate the 
engine's limit capabilities.
    The endurance demonstration must include increases and decreases of 
the engine's power settings, and dwellings at the power settings for 
durations that produce the extreme physical conditions the engine 
experiences at rated performance levels, operational limits, and at any 
other conditions or power settings that are required to verify the 
limit capabilities of the engine.

24. Temperature Limit

    The engine design must demonstrate its capability to endure 
operation at its temperature limits plus an acceptable margin. The 
applicant must quantify and justify to the Administrator the margin at 
each rated condition. The demonstration must be repeated for all 
declared duty cycles and associated ratings, and operating 
environments, that would impact temperature limits.

25. Operation Demonstration

    The engine design must demonstrate safe operating characteristics, 
including but not limited to power cycling, starting, acceleration, and 
overspeeding throughout its declared flight envelope and operating 
range. The declared engine operational characteristics must account for 
installation loads and effects.

26. Durability Demonstration

    The engine must be subjected to a durability demonstration to show 
that each part of the engine has been designed and constructed to 
minimize any unsafe condition of the system between overhaul periods or 
between engine replacement intervals if the overhaul is not defined. 
This test must simulate the conditions in which the engine is expected 
to operate in-service, including typical start-stop cycles.

27. System and Component Tests

    The applicant must show that systems and components will perform 
their intended functions in all declared environmental and operating 
conditions.

28. Rotor Locking Demonstration

    If shaft rotation is prevented by locking the rotor(s), the engine 
must demonstrate:
    (a) Reliable rotor locking performance;
    (b) Reliable unlocking performance; and
    (c) That no hazardous engine effects, as specified in Special 
Condition no. 17(d)(2), will occur.

29. Teardown Inspection

    The applicant must comply with either (a) or (b) as follows:
    (a) Teardown evaluation.
    (1) After the endurance and durability demonstrations have been 
completed, the engine must be completely disassembled. Each engine 
component and lubricant must be within service limits and eligible for 
continued operation in accordance with the information submitted for 
showing compliance with Sec.  33.4, Instructions for Continued 
Airworthiness.
    (2) Each engine component having an adjustment setting and a 
functioning characteristic that can be established independent of 
installation on or in the engine must retain each setting and 
functioning characteristic within the established and recorded limits 
at the beginning of the endurance and durability demonstrations.
    (b) Non-Teardown evaluation.
    If a teardown is not performed for all engine components, then the 
life limits for these components and lubricants must be established 
based on the endurance and durability demonstrations and documented in 
the ICA in accordance with Sec.  33.4.

30. Containment

    The engine must provide containment features that protect against 
likely hazards from rotating components as follows--
    (a) The design of the case surrounding rotating components must 
provide for the containment of the rotating components in the event of 
failure, unless the applicant shows that the margin to rotor burst 
precludes the possibility of a rotor burst.
    (b) If the margin to burst shows that the case must have 
containment features in the event of failure, the case must provide for 
the containment of the failed

[[Page 53534]]

rotating components. The applicant must define by test, validated 
analysis, or a combination thereof, and document in the engine 
installation manual, the energy level, trajectory, and size of 
fragments released from damage caused by the main rotor failure, and 
that pass forward or aft of the surrounding case.

31. Operation With a Variable Pitch Propeller

    The applicant must conduct functional demonstrations including 
feathering, negative torque, negative thrust, and reverse thrust 
operations, as applicable, with a representative propeller. These 
demonstrations may be conducted in a manner acceptable to the 
Administrator as part of the endurance, durability, and operation 
demonstrations.

32. General Conduct of Tests

    (a) Maintenance of the engine may be made during the tests in 
accordance with the service and maintenance instructions submitted in 
compliance with Sec.  33.4.
    (b) The applicant must subject the engine or its parts to 
maintenance and additional tests that the Administrator finds necessary 
if--
    (1) The frequency of the service is excessive;
    (2) The number of stops due to engine malfunction is excessive;
    (3) Major repairs are needed; or
    (4) Replacement of a part is found necessary during the tests or 
due to the teardown inspection findings.
    (c) Upon completion of all demonstrations and testing specified in 
these special conditions, the engine and its components must be--
    (1) Within serviceable limits;
    (2) Safe for continued operation; and
    (3) Capable of operating at declared ratings while remaining within 
limits.

    Issued in Kansas City, Missouri, on September 10, 2021.
Patrick R. Mullen,
Manager, Technical Innovation Policy Branch, Policy and Innovation 
Division, Aircraft Certification Service.
[FR Doc. 2021-19926 Filed 9-24-21; 8:45 am]
BILLING CODE 4910-13-P