CONTENTS
Subpart E⎯Powerplant
GENERAL
Section P AGE
23.901 Installation1
23.903 Engines10
23.904 Automatic power reserve system17
23.905 Propellers18
23.907 Propeller vibration23
23.909 Turbocharger systems25
23.925 Propeller clearance35
23.929 Engine installation ice protection37
23.933 Reversing systems39
23.934 Turbojet and turbofan engine thrust reverser systems tests41
23.937 Turbopropeller-drag limiting systems42
23.939 Powerplant operating characteristics43
23.943 Negative acceleration45
FUEL SYSTEM
23.951 General46
23.953 Fuel system independence49
23.954 Fuel system lightning protection50
23.955 Fuel flow51
23.957 Flow between interconnected tanks63
23.959 Unusable fuel supply64
23.961 Fuel system hot weather operation71
23.963 Fuel tanks: General77
23.965 Fuel tank tests78
23.967 Fuel tank installation80
23.969 Fuel tank expansion space82
23.971 Fuel tank sump83
23.973 Fuel tank filler connection85
23.975 Fuel tank vents and carburetor vapor vents87
23.977 Fuel tank outlet89
23.979 Pressure fueling systems90
xiii
FUEL SYSTEM COMPONENTS
23.991 Fuel pumps91
23.993 Fuel system lines and fittings93
23.994 Fuel system components95
23.995 Fuel valves and controls97
23.997 Fuel strainer or filter99
23.999 Fuel system drains101
23.1001 Fuel jettisoning system102
OIL SYSTEM
23.1011 General104
23.1013 Oil tanks108
23.1015 Oil tank tests110
23.1017 Oil lines and fittings111
23.1019 Oil strainer or filter112
23.1021 Oil system drains113
23.1023 Oil radiators114
23.1027 Propeller feathering system115
COOLING
23.1041 General116
23.1043 Cooling tests117
23.1045 Cooling test procedures for turbine engine powered airplanes119
23.1047 Cooling test procedures for reciprocating engine powered airplanes120
LIQUID COOLING
23.1061 Installation121
23.1063 Coolant tank tests122
INDUCTION SYSTEM
23.1091 Air induction system123
23.1093 Induction system icing protection124
23.1095 Carburetor deicing fluid flow rate135
23.1097 Carburetor deicing fluid system capacity136
23.1099 Carburetor deicing fluid system detail design137
23.1101 Induction air preheater design138
23.1103 Induction system ducts139
23.1105 Induction system screens140
xiv
23.1107 Induction system filters141
23.1109 Turbocharger bleed air system142
23.1111 Turbine engine bleed air system143
EXHAUST SYSTEM
23.1121 General144
23.1123 Exhaust system147
23.1125 Exhaust heat exchangers149
POWERPLANT CONTROLS AND ACCESSORIES
23.1141 Powerplant controls: General150
23.1142 Auxiliary power unit controls152
23.1143 Engine controls153
23.1145 Ignition switches156
23.1147 Mixture controls157
23.1149 Propeller speed and pitch controls158
23.1153 Propeller feathering controls159
23.1155 Turbine engine reverse thrust and propeller pitch settings below the
flight regime160
23.1157 Carburetor air temperature controls162
23.1163 Powerplant accessories163
23.1165 Engine ignition systems165
POWERPLANT FIRE PROTECTION
23.1181 Designated fire zones; regions included167
23.1182 Nacelle areas behind firewalls169
23.1183 Lines, fittings, and components170
23.1189 Shutoff means172
23.1191 Firewalls174
23.1192 Engine accessory compartment diaphragm176
23.1193 Cowling and nacelle177
23.1195 Fire extinguishing systems179
23.1197 Fire extinguishing agents182
23.1199 Extinguishing agent containers183
23.1201 Fire extinguishing systems materials184
23.1203 Fire detector system185
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POWERPLANT GUIDE FOR CERTIFICATION OF PART 23 AIRPLANES
Subpart E⎯Powerplant
GENERAL
23.901 Installation (Amendment 23-53)
CAR 3 Cross-reference: 3.411
ADC Cross-reference: 5.1
What guidance is there for the certification of powerplant electronic systems installations?
Electronic systems are increasingly used to control different airplane systems including powerplant systems. During certification of these installations, § 23.1309 must be used to determine the potential failure modes and the resulting severity of a failure event. A safety analysis is generated during the engine certification that covers engine and engineairplane interfaces. This engine level safety analysis should be used as input to the airplane level safety analysis. Software level requirements for the installed engine should be determined early in the process to ensure the software level certificated for the engine, according to part 33, is compatible with the installation. The engine manufacturer and the Airplane Certification Office should be coordinated with early in the project.
According to § 11.19, special conditions, may be required for powerplant systems installations to comply with the requirements of § 23.1309. These special conditions should not require retesting of the engine or its certificated components except as part of the airplane.
What may be required by special conditions?
Examples of special condition requirements may include, but are not limited to, the following:
1. Lightning test;
2. High Intensity Radiated Fields (HIRF) testing;
3. Software level validation testing; and
4. Environm ental testing.
What are some examples of powerplant electronic systems?
Examples of powerplant electronic systems may include, but are not limited to, the following:
1. Electronic Engine Controls (EEC);
2. Full Authority Digital Engine Controls (FADEC);
3. Electronic turbocharger wastegate controls; and
4. Electronic propeller speed, pitch, and feathering controls.
Related Material
AC 23.1309-1C, Equipment, Systems, and Installations in Part 23 Airplanes
AC 23.1311-1A, Installation of Electronic Displays in Part 23 Airplanes
AC 33.28-1, Compliance Criteria for 14 CFR § 33.28 Aircraft Engines, Electrical and Electronic Engine Control Systems
AC 33.28-2, Guidance Material for 14 CFR § 33.28, Reciprocating Engines, Electrical and Electronic Engine Control Systems
Policy Memorandum ANE-2001-35.31-R0, Policy for Bird Strike, Lightning, and Centrifugal Load Testing for Composite Propeller Blades and Spinners
Paragraph 23.901(a)
ADC Cross-reference: 5.1(a)
What components should be included as part of the powerplant installation?
Examples of powerplant installation components may include, but are not limited to, the following:
1. Engines;
2. Propellers;
3. Gearboxes and engine driven accessories;
4. Nacelles and inlets;
5. Engine oil systems;
6. Fuel tanks, lines, manifolds, and controls;
7. Ignition system components;
8. Propulsion control and monitoring devices;
9. Exhaust nozzles, mufflers, plenums, etc.;
10. Fluid collectors and drain lines;
11. Pneumatic bleed valves and ducting;
12. Engine fire protection systems;
13. Engine and propeller icing protection systems; and
14. Thrust attenuating or reversing installations
Components that are part of an engine or propeller type design certificated under parts 33 or 35, respectively, are considered part of the powerplant installation. Any findings of compliance with part 23 requirements should take maximum advantage of the relevant findings made in support of part 33 or 35.
What regulations should be considered for powerplant installations using technologies other than the typical spark ignition reciprocating and turbine engines?
In the future, designs using engines other than the typical spark ignition reciprocating and turbine engine cycles, such as fuel cell/electric motor, diesel cycle, or even rocket or jet assisted take-off, may be proposed. These designs will require careful selection of the applicable powerplant rules and may require special conditions depending on how similar they are to the typical engines.
Related Material
PS-ACE100-2002-004, Diesel Engine Installation
Paragraph 23.901(b)
ADC Cross-reference: 5.1(b)
What are examples of potential inspection and maintenance items?
Examples of potential powerplant inspection and maintenance items may include, but are not limited to, the following:
1. Oil reservoir fill and quantity sight glasses;
2. Engine control linkages;
3. Oil, fuel, air filters;
4. Oil system chip detectors;
5. Engine mount inspections;
6. Engine exhaust system components; and
7. Firewalls.
What are the typical methods for showing compliance?
Compliance is typically shown using the following methods either alone or in combination:
1. Review of drawings, schematics, system descriptions, and safety analyses;
2. Mock-up inspections and demonstrations;
3. Laboratory and aircraft testing;
4. Comparison with the service experience on similar designs; and
5. Comparison with accepted design standards.
Related Material
AC 23-10, Auxiliary Fuel Systems for Reciprocating and Turbine Powered Part 23 Airplanes
Paragraph 23.901(c)
ADC Cross-reference: 5.1(c)
What are some of the considerations for complying with this rule?
To comply with this rule, the powerplant installation should be designed to provide access (cowling that is easily opened and closed) for the pilot to visually check the following:
1. Engine oil level;
2. Flammable fluid leaks;
3. If applicable, the exterior condition of the turbocharger and wastegate installation;
4. If applicable, tail pipe, multi-segmented V-band clamps, and firewalls;
5. Electrical wiring;
6. Fuel and oil lines and fittings; and, otherwise, make a cursory inspection of the engine installation; and
7. Other items as defined by the engine, propeller, or airplane manufacturer.
For more information refer to § 23.611, Accessibility provisions.
Paragraph 23.901(d)
ADC Cross-reference: None
This guidance may be used for Airship Certification as applicable.
What special considerations are there for turbine engine installations?
Paragraph 23.901(d) requires that carcass vibration and rain, hail, ice, and bird ingestion be considered for all turbine engine installations. This requirement ensures the installation does not degrade the certificated capability of the engine.
What considerations and methods of compliance are typical for the vibration requirements?
Compliance with rules concerning vibration usually involves instrumentation and testing.
These tests may consist of a combination of bench vibration tests and full-scale airplane tests. Analysis can be used to support the placement of instrumentation and to identify the critical test conditions. Coordination with the engine manufacturer may be necessary to understand the engine vibration limits and to design the tests to show the installation vibration characteristics are within the engine certification limits throughout the airplane flight envelope.
What considerations and methods of compliance are typical for the ingestion requirements?
Compliance with the rain ingestion requirements of § 23.901(d)(2) is typically shown with design analysis that identifies areas of concern and tests for those areas of concern.
Part 33 engine certification testing may be used for part 23 compliance if the engine certification testing addressed the areas of concern identified by the installation design analysis (for example, use of an installation representative test inlet system). Part 33 5
engine certification testing may also be used for part 23 compliance if specific conditions addressed in the rule were addressed during engine certification testing. For airplanes with a certification basis before Amendment 23-53, a test is typically required if the specific operating considerations contained in the part 23 rule were not addressed during engine certification.
When evaluating areas of concern with the installation, consider areas where water pooling with resulting ingestion or shed of localized “slugs” of water normally not addressed during engine certification might occur. Some examples are inlet system channels, indentations, and so forth. These are typical of turbopropeller or S-duct type inlets that have complex geometry that can allow water pooling. This consideration is usually not a concern with simple pitot style inlets typical of part 23 turbofan/jet engine installations. Part 23 turbine engine installations typically require testing since most of these are turbopropeller installations. However, if design analysis shows the installation will not affect the water ingestion characteristics and engine certification addressed the specific conditions addressed in the part 23 rule, this analysis combined with engine certification testing may be enough to demonstrate rain ingestion compliance. Because of the large diversity of turbine engine installations in part 23 airplanes, all installations should be evaluated to determine whether areas of concern exist. Since the rain ingestion requirements in part 33 were not added until Amendment 33-6, the airplane applicant needs to evaluate the engine's certification basis to determine whether the engine has been subjected to part 33 rain ingestion testing. If the engine does not have Amendment 33-6 or a later amendment as part of the certification basis, the engine must have a safe service history of rain ingestion in similar installations, under § 23.903(a)(2)(iv).
If it is determined that testing for rain ingestion should be performed, flight test is not required. The intent of the part 23 rule is to ensure the engine installation has not deteriorated the rain ingestion tolerance of the certificated engine. Since a ground static engine test normally demonstrates engine certification compliance, use of installation ground tests at the required power/thrust settings has been commonly accepted as a means of compliance. The applicant can use design analysis to determine critical configurations and conditions of the installation. This might reduce required installation tests to the critical configurations and conditions instead of repeating the entire part 33 test conditions. Engine certification should address the results of the critical point analysis for the engine; therefore, it is important for the engine installer to research the conditions and requirements used for engine certification.
What are some other examples of issues not addressed by engine certification that need to be addressed for installation compliance with § 23.901(d)?
Amendment 23-53 added requirements for ice, hail, and birds similar to those in part 33.
Examples of installation issues normally not addressed by engine certification, but that should be addressed for installation compliance, include the following:
1. Ice build-up on areas where ice shed may be ingested by the engines (for example, ice shed from wings and airframe sources into aft mounted engines); and 6
2. Consideration of items such as inlet splitters, acoustic liners, and so forth, that may be damaged by impact with ice, hail, and birds.
Paragraph 23.901(e)
ADC Cross-reference: 5.1(d)
What instructions are typically provided under the engine and propeller type certificates?
Sections 33.5 and 35.3 list the requirements for engine and propeller installation instruction manuals. Examples of subjects typically provided under the engine and propeller type certificates may include, but are not limited to, the following:
1. Engine and propeller operating limitations;
2. Engine and propeller mounting provisions;
3. Allowable fuel and oil specifications;
4. Allowable fuel and oil temperatures;
5. Fuel inlet pressures;
6. Allowable accessory temperature limits;
7. Vibration limits;
8. Accessibility requirements;
9. Turbine engine inlet distortion limits; and
10. Abnormal engine failure load conditions such as turbine engine fan blade failure.
It is important to identify and accommodate all engine and propeller certification dependencies with the aircraft installation to ensure compatibility of the hardware and operational limitations.
Is it possible to certificate an airplane to use a fuel other than one certificated for use on the engine?
No, the fuel used in the airplane must be certificated for use in the engine as well as the airplane to comply with § 23.901(e). Other fuels such as automobile gasoline have been certificated for use in an airplane with a separate certification for using the fuel in the 7
engine. All applicable sections of 14 CFR part 33 and part 23 must be considered when certificating a fuel for use in an engine and in an airplane, respectively.
Related Material
AC 23.1521-1B, Type Certification of Automobile Gasoline in Part 23 Airplanes with Reciprocating Engines
AC 23.1521-2 with Change 1, Type Certification of Oxygenates and Oxygenated Gasoline Fuels in Part 23 Airplanes with Reciprocating Engines
AC 20-24B, Qualification of Fuels, Lubricants and Additives for Aircraft Engines
AC 20-122A, Anti-misfueling Devices: Their Availability and Use
Paragraph 23.901(f)
ADC Cross-reference: None
This guidance may be used for Airship Certification as applicable.
What should be considered when determining the applicable parts of these regulations as applied to Auxiliary Power Units (APU)?
The typical Auxiliary Power Unit (APU) is a combustion cycle powerplant operated primarily to generate electrical, pneumatic, and hydraulic power for ground and limited flight operations and not thrust for flight. Each of the rules applicable to powerplant installations must be considered carefully relative to the design features and operating requirements for a given APU. Below are three examples.
1. APUs typically do not have propellers connected to them and, in such a case, it is obvious, the portions of this part that apply to propellers should not be considered for such an installation.
2. APUs generally have a much smaller operating envelope than do thrust producing powerplants and, as such, due consideration should be given to the requirements in areas such as induction system icing (§ 23.1093).
3. An APU that is used to provide emergency power to meet the requirements of § 23.1351 would be considered differently than an APU intended only for ground use.
What regulations should be considered for Auxiliary Power Units using technologies other than the typical combustion cycles?
In the future, designs using exotic technologies to produce auxiliary electrical, pneumatic, and hydraulic power, such as fuel cells, may be proposed. These designs will 8