53508 Federal Register / Vol. 86, No. 184 / Monday, September 27, 2021 / Rules and Regulations 

1The 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. 

3https://www.astm.org/DATABASE.CART/ 

HISTORICAL/F3338-18.htm. 4 29 FR 7452. 

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. 

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 highvoltage 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. 

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. 

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 

§ 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 § 21.101. The FAA issues 

special conditions, as defined in 14 CFR 

11.19, in accordance with § 11.38, and 

they become part of the type 

certification basis under § 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, hightemperature, 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. 

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 


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5Sometimes this entire system is referred to as an 

inverter. Throughout this document, the controller 

and inverter will be referred to as the controller. 

generating systems. The magniX motor, 

in both models, is a device that converts 

electrical energy into mechanical energy 

by electric current flowing through wire 

coils in the motor, producing a magnetic 

field that interacts with magnets on the 

rotating shaft. The controller is a system 

that consists of two main functional 

elements: the motor controller and an 

electric power inverter to drive the 

motor.5 The high-voltage system is a 

combination of wires and connectors 

that couple the motor and the controller. 

In addition, the technology required 

to produce these high-voltage and highcurrent electronic components 

introduces potential hazards that do not 

exist in aircraft engines that operate 

using aviation fuel. For example, highvoltage transmission lines, 

electromagnetic fields, magnetic 

materials, and high-speed electrical 

switches form the electric 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, highintensity radiated fields, and lightning. 

The assessments that verify 

environmental limits account for the 

effects of electrical bonding. A special 

condition for electrical bonding is not 

required to establish proper electrical 

bonding. Special Condition no. 1 

mandates compliance with § 33.5(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 

§ 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 


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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 § 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 § 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 (powersupply) 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. 


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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 

§§ 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 

§ 33.7(a),’’ and then proceeds to replace 

all of the § 33.7 details with Special 

Condition no. 2 requirements. TCCA 

stated the replacement of § 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 § 33.7, combined with 

§ 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 

§§ 33.7(a), 33.7(d), and 33.8. Special 

Condition no. 2 provides requirements 

in addition to those in § 33.7(a). The 

concern stated by TCCA is remedied by 

the inclusion of §§ 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 powersupply 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 § 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. 


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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 

(§ 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 highvoltage 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 § 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 

§§ 35.21, 35.23, 35.42 and 35.43.’’ 

TCCA provided a similar comment, 

asking why § 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 § 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 


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provided in Special Condition no. 1, 

§ 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 § 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 § 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 § 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 


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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 § 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 

§ 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 


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6https://my.rtca.org/NC__Product?id=

a1B36000001IcjTEAS. 

7https://my.rtca.org/NC__Product?id=

a1B36000001IcnSEAS. 

8https://www.faa.gov/documentLibrary/media/ 

Advisory_Circular/AC_33_28-3.pdf. 

Hardware, dated April 19, 2000,6

distinguishes between complex and 

simple electronic hardware. 

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. 

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 § 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. 

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 aircraftsupplied 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 aircraftsupplied 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 highvoltage components of this engine. 

TCCA suggested that the FAA modify 

Special Condition no. 10(e) to require 


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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 highvoltage 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 highvoltage 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 powersupply 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 


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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 

§ 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 § 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 

§ 33.28(f)(1), but the requirements of 

§ 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. 


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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 enginelevel safety analysis. The engine-level 

safety analysis does not go into enough 

detail to address the effects of control 

system failures and malfunctions. The 

FAA did not modify this special 

condition as a result of this comment. 

Comment Summary: Textron stated, 

Special Condition no. 11 mandates 

compliance with 14 CFR 33.29(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 

§ 33.29(f). 

FAA Response: Special Condition no. 

10(g) corresponds to § 33.28(e), which 

requires an engine control systems 

safety assessment. However, § 33.29(f) 

requires that, as part of the System 

Safety Assessment of § 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 § 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 

§ 33.75(d) and § 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 § 33.62 

Stress analysis. The corresponding part 

33 airworthiness requirement for 

Special Condition no. 9 (Overspeed) is 

§ 33.27, Turbine, compressor, fan, and 

turbosupercharger rotor overspeed. 

These special conditions are intended to 

apply similar requirements to the 

magniX engines but with additional 

provisions to account for electric engine 

technology. The additional analysis 

suggested in 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 


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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 postcertification 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 lifelimited parts, is consistently produced 

and preserved over the lifetime of those 

parts. The manufacturing plan includes 

special processes and production 

controls to prevent manufacturinginduced 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 lifelimited 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 


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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 lifelimited 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 


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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 § 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 § 33.73, so all requirements of 

§ 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 oncondition 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 § 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 


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dfu/sc_e-18_electric_propulsion_units_for_cs-23_

normal-category_aeroplanes_u.pdf. 

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. 

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 § 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. 


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product-certification-consultations/final-specialcondition-sc-e-19-electric. 

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. 

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, § 33.77, Foreign 

object ingestion—ice, and § 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 nonsealed 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 


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rain conditions. No changes were made 

to this special condition as a result of 

this comment. 

Special Condition No. 19, Liquid 

Systems 

The FAA proposed that Special 

Condition no. 19 would require magniX 

to ensure that liquid systems used for 

lubrication or cooling of engine 

components are designed and 

constructed to function properly. Also, 

the FAA proposed that, if a magniX 

engine liquid system is shared with an 

aircraft liquid system, the interfaces 

between the engine and aircraft systems 

must be defined in the engine 

installation manual. 

Comment Summary: Wisk 

recommended that these special 

conditions address the risk of a liquid 

system freezing after an engine 

shutdown and preserve the ability for 

engine restart. 

FAA Response: These special 

conditions already account for the 

concerns expressed by Wisk. Special 

Condition no. 19 requires magniX to 

ensure the liquid system operates 

appropriately in all atmospheric 

conditions in which the engine is 

expected to operate. The FAA did not 

change Special Condition no. 19 as a 

result of this comment. 

Comment Summary: Rolls-Royce 

noted that the FAA did not propose to 

require the design to comply with 14 

CFR 33.64, Pressurized engine static 

parts. The commenter stated that it 

anticipated electric engine 

configurations with pressurized cooling 

systems and pressurized lubrication 

systems and recommended that this 

requirement be included in these 

special conditions. 

FAA Response: These special 

conditions are not generally applicable 

to all electric engines and apply only to 

these proposed magniX electric engines. 

However, magniX may choose to 

pressurize the liquid systems in their 

engines. Therefore, the FAA has 

changed final Special Condition no. 19 

to require magniX to account for 

pressurized static engine parts. 

Comment Summary: Textron 

recommended that these special 

conditions require that the engine 

installation manual prescribe the 

cooling and lubricating fluids used on 

these engines. 

FAA Response: The FAA has 

modified Special Condition no. 19 in 

these final special conditions to require 

magniX to list eligible lubricants and 

coolants in the engine installation 

manual. 

Comment Summary: Textron 

recommended that the FAA add a 

requirement that prevents magnetically 

attracted engine debris from 

accumulating in passages that could 

block or limit coolant flow. 

FAA Response: The potential for 

magnetic debris in the magniX engine 

liquid cooling system would likely be a 

consequence of an engine failure or 

inadequate maintenance. If this were a 

characteristic of the type design, the 

magniX engines would not likely meet 

the requirements established in these 

special conditions, such as Special 

Condition nos. 5 (Durability) and 7 

(Safety Analysis). The FAA did not 

change Special Condition no. 19 as a 

result of this comment. 

Comment Summary: TCCA noted the 

possibility that the magniX electric 

engine liquid system might rely on 

aircraft systems. In that case, TCCA 

recommended that these special 

conditions require that reliance be 

declared in the engine installation 

manual. 

FAA Response: Special Condition no. 

1 requires magniX to comply with 14 

CFR 33.5, Instruction manual for 

installing and operating the engine. The 

requirements in §§ 33.5(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 §§ 33.63, 

Vibration, and 33.83, Vibration test. 

Special Condition no. 20(a) corresponds 

to § 33.63, Subpart E, which has 

provisions for the design and 

construction of the electric engine. 

Special Condition no. 20(b) corresponds 

to § 33.83, Subpart F, which applies to 

the block tests. This § 33.83, Vibration 

test, reference explains why a vibration 

survey is specified in Special Condition 

no. 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 § 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 § 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 


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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 § 33.85 only apply to the endurance 

test specified in § 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 § 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 inservice, 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 


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11https://www.easa.europa.eu/certificationspecifications/cs-e-engines. 

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 leastcapable engine allowed by the type 

design from failing due to temperaturerelated 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 § 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. 

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 inflight 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 inflight 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 


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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 enginereplacement 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 offwing 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 § 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 § 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 § 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 


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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 § 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, subassemblies, 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 longterm 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 


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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 §§ 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 posttest 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 § 33.94(a), Blade 

containment and rotor unbalance tests, 

and § 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 lifelimited 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 

§ 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. 


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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 § 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 § 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 nonprotected 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 § 33.21. In addition, 

if cooling is required to satisfy the safety 


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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 inservice. 

(i) Aircraft-supplied data. 

Any single failure leading to loss, 

interruption, or corruption of aircraftsupplied 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, 


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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 serviceinduced 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 

§ 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 § 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 

§ 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 § 33.28(b)(1)(i), 

§ 33.28(b)(1)(iii) and § 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 § 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 


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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 § 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 § 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 


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53534 Federal Register / Vol. 86, No. 184 / Monday, September 27, 2021 / Rules and Regulations 

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 § 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 


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