Paragraph 23.993(e)
ADC Cross-reference: 5.25(e)
How is § 23.993(e) related to the powerplant cooling requirements?
Section § 23.1041 specified that there be provisions for maintaining the temperatures of powerplant components and fluids within their limits during various operations including shutdown. One such provision, as specified in § 23.993(e), is to not locate these items in areas exposed to unacceptable temperatures.
23.994 Fuel system components (Amendment 23-29)
CAR 3 Cross-reference: None
ADC Cross-reference: 5.26
What is considered a hazardous quantity of fuel in § 23.994?
For the purpose of this section, “hazardous quantity” is defined as one quart, except a greater amount may escape if that greater amount can be substantiated as non-hazardous.
What other sections of the regulations are related to § 23.994?
The following sections are related to § 23.994 and may help determine the acceptability of the design.
§ 23.561 Emergency Landing Conditions, General
§ 23.721 Landing Gear, General
§ 23.863 Flammable fluid fire protection
§ 23.967(e) Fuel tank installation
§ 23.1189 Shutoff means
What are some typical methods used in complying with this rule?
The release of fuel from damaged fuel system components is the most likely cause of fire during a wheels-up landing on a paved runway. Therefore, the location and routing of fuel system components in the engine nacelle(s) and fuselage should be evaluated with respect to runway scraping and the resultant structural deformation. Particular attention should be paid to the release of fuel in areas with possible ignition sources such as electrical arcing and hot components. The following guidelines should be considered.
1. Design the fuel system to minimize the spilling or leaking of fuel and migration of the fuel into areas with likely ignition sources.
2. Locate and route the fuel system components as far as practicable from likely impact areas and areas where structural deformation may cause crushing, severing, punctures, rupture of frangible fittings, or high tensile loads in the lines.
3. Construct fuel lines to protect their integrity during and after a wheels-up landing.
The lines should allow stretching or movement with the deformed structure.
4. Isolate, separate, and route fuel lines and electrical wiring to the maximum extent practicable to minimize hazardous fuel spillage in these potential ignition source areas.
5. Shield and drain areas of potential fuel spillage away from potential ignition source areas.
6. Locate fuel shutoff valves outside areas of potential damage, such as engine nacelles, and design the valve support structures to maintain their integrity during and after the event.
7. Install auxiliary fuel tanks and systems based on the guidance in AC 23-10, Auxiliary Fuel Systems for Reciprocating and Turbine Powered Part 23 Airplanes.
23.995 Fuel valves and controls (Amendment 23-29)
CAR 3 Cross-reference: 3.551
ADC Cross-reference: 5.27
What rules are related to § 23.995?
See § 23.1189 Powerplant Fire Protection, Shutoff Means.
Paragraph 23.995(a)
ADC Cross-reference: 5.27(a)
No specific policy is available as of December 31, 2002.
Paragraph 23.995(b)
ADC Cross-reference: 5.27(b)
No specific policy is available as of December 31, 2002.
Paragraph 23.995(c)
ADC Cross-reference: 5.27(c)
What is a typical means of compliance for § 23.995(c)?
Compliance with this rule is usually accomplished by designing the fuel valve installation such that the valve is supported by primary or secondary airframe structure.
Paragraph 23.995(d)
ADC Cross-reference: 5.27(d)
No specific policy is available as of December 31, 2002.
Paragraph 23.995(e)
ADC Cross-reference: 5.27(e)
No specific policy is available as of December 31, 2002.
Paragraph 23.995(f)
ADC Cross-reference: 5.27(f)
No specific policy is available as of December 31, 2002.
Paragraph 23.995(g)
ADC Cross-reference: 5.27(g)
No specific policy is available as of December 31, 2002.
23.997 Fuel strainer or filter (Amendment 23-43)
CAR 3 Cross-reference: 3.552
ADC Cross-reference: 5.28
Does the powerplant installation require a fuel filter if the engine has one according to its type certificate?
Turbine engines certificated to 14 CFR part 33, § 33.67, Fuel system, Amendment 33-6 or subsequent, will include a fuel filter complying with § 23.997, and no airframesupplied filter is required. Turbine engines certificated prior to § 33.67, Amendment 33- 6, may require an airframe-supplied filter.
Reciprocating engines certificated to 14 CFR part 33, § 33.35 are not required to have a fuel filter as part of their certificated fuel system. The engine manufacturer is required only to specify the degree of filtering necessary and to verify that particles passing through the specified filter will not adversely affect the engine fuel system operation.
Because of this, an engine with a fuel filter certified to § 33.35 is not sufficient to meet all the requirements of § 23.997. To show compliance to § 23.997 for an engine with a filter, an airplane manufacturer would have to coordinate with the engine manufacturer on the filter installation to provide compliance data or add an airframe filter.
Paragraph 23.997(a)
ADC Cross-reference: 5.28(a)
No specific policy is available as of December 31, 2002.
Paragraph 23.997(b)
ADC Cross-reference: 5.28(b)
No specific policy is available as of December 31, 2002.
Related Material
AC 23-15, Small Airplane Certification Compliance Program
Paragraph 23.997(c)
ADC Cross-reference: 5.28(c)
No specific policy is available as of December 31, 2002.
Paragraph 23.997(d)
ADC Cross-reference: 5.28(d)
Is there any requirement for a pilot indication system relative to the fuel filter?
Section 23.1305 requires fuel flow indicators for both reciprocating and turbine-powered airplanes and a means to warn the pilot of fuel strainer or filter blockage before it reaches the capacity specified in § 23.997(d).
Paragraph 23.997(e)
ADC Cross-reference: None
No specific policy is available as of December 31, 2002.
Related Material
AC 23.1419-2B, Certification of Part 23 Airplanes for Flight in Icing Conditions
23.999 Fuel system drains (Amendment 23-43)
CAR 3 Cross-reference: 3.553
ADC Cross-reference: 5.29
Paragraph 23.999(a)
ADC Cross-reference: 5.29(a)
Where are drains typically located?
Usually more than one drain valve is required to drain the entire fuel system. These are typically located in fuel tank sumps, fuel line low spots, and in fuel filter/strainers.
Paragraph 23.999(b)
ADC Cross-reference: 5.29(b)
May a spring-loaded drain valve be used to comply with § 23.999(b)?
Spring-loaded drain valves may be used to comply with the positive locking provision of this paragraph in any region of positive fuel pressure. If a spring-loaded valve is located in a negative fuel pressure region (e.g., upstream of an engine-drive fuel pump providing suction lift), substantiate the installation by a test.
Related Material:
AC 20-119 Fuel Drain Valves
23.1001 Fuel jettisoning system (Amendment 23-51)
CAR 3 Cross-reference: None
ADC Cross-reference: 5.30
Related Material
AC 23-8B, Flight Test Guide for Certification of Part 23 Airplanes
Paragraph 23.1001(a)
ADC Cross-reference: 5.30
What is the definition of maximum weight as used in § 23.1001(a)?
The maximum weight to be used in calculating the fuel jettison rate is the maximum takeoff weight of the airplane. This is supported by Amendment 23-7, which, for the most part, used the requirements of § 25.1001 as a new § 23.1001. At the time, § 25.1001 stated that the calculation was to use maximum takeoff weight.
Paragraph 23.1001(b)
ADC Cross-reference: 5.30(a)
No specific policy is available as of December 31, 2002.
Paragraph 23.1001(c)
ADC Cross-reference: 5.30(a)(1), 5.30(a)(2), 5.30(a)(3), 5.30(a)(4)
What methods are typically used to show compliance with § 23.1001(c)?
Colored fuel or a surface treatment that changes appearance upon contact with fuel or fuel vapor has been used to detect surface impingement. Combustible mixture detectors, scent, or visual inspections have been used to detect fuel or fuel vapor entering portions of the airplane.
Paragraph 23.1001(d)
ADC Cross-reference: None
No specific policy is available as of December 31, 2002.
Paragraph 23.1001(e)
ADC Cross-reference: None
No specific policy is available as of December 31, 2002.
Paragraph 23.1001(f)
ADC Cross-reference: 5.30(b)
No specific policy is available as of December 31, 2002.
Paragraph 23.1001(g)
ADC Cross-reference: 5.30(c)
No specific policy is available as of December 31, 2002.
Paragraph 23.1001(h)
ADC Cross-reference: 5.30(d)
No specific policy is available as of December 31, 2002.
OIL SYSTEM
23.1011 General (Amendment 23-43)
CAR 3 Cross-reference: None
ADC Cross-reference: 5.31
Paragraph 23.1011(a)
ADC Cross-reference: None
This guidance may be used for Airship Certification as applicable.
Can the part 33 certification of oil system components be used to show compliance with § 23.1011?
Oil systems and components certified with the engine may or may not be suitable for use in a specific airplane installation, depending upon the test/analysis performed at the time.
Also, engines may be originally certified with the intention of being installed in different airplanes than where they are eventually used. Consequently, oil systems and components approved during engine type certification are only acceptable for use without further substantiation when they complied with standards that are equal or more stringent than those in this subpart.
Evaluate each pertinent item in the installation to assess the airplane requirements versus the requirements demonstrated during engine certification. Verify the latter with the engine manufacturer or the FAA office controlling the engine type design.
Paragraph 23.1011(b)
ADC Cross-reference: 5.31(a)
What are the requirements for continued safe operation of the engine(s)?
The engine requirements for oil quantities and temperatures are established by the engine manufacturer and may be found on the Type Certification Data Sheet or in the engine installation manual. The airplane installation must not cause the engine limits to be exceeded under normal operations.
Paragraph 23.1011(c)
ADC Cross-reference: 5.31(b)
How much oil must the system contain?
Paragraph 23.1011(c) requires that, “The usable oil tank capacity may not be less than the product of the endurance of the airplane under critical operating conditions and the maximum oil consumption of the engine under the same conditions, plus a suitable margin to ensure adequate circulation and cooling.” In other words, there needs to be enough oil (usable supply) to allow the engine to consume the usable fuel. This should be substantiated by a quantitative analysis.
In addition, a suitable oil quantity margin for system circulation is necessary for all engine installations. The oil system should be capable of maintaining the engine within its operating limitations (i.e., oil temperature with the minimum oil quantity provided for circulation). Cooling tests do not need to be performed with a low usable oil supply provided the oil is properly cooled at all oil levels.
What are the definitions of some of the terms used to determine the required oil quantity?
Usable Oil
Usable oil is defined as the quantity of oil in the oil tank (or sump in the case of wet sump engines) in excess of the minimum quantity of oil required to keep the oil pump inlet feed covered under the most adverse operating condition.
Without any other data, the most severe of the following two conditions may be used as the most adverse operating condition (in both cases, with the airplane at a zerodegree roll angle):
1. The nose-up pitch angle required for the sea level best rate-of-climb speed with maximum continuous power, or
2. The nose-down pitch angle required for the 1.3 V SO power-off landing configuration.
For most wet sump engines, the usable oil quantity for various pitch angles is listed on the appropriate engine Type Certificate Data Sheet (TCDS). This quantity may be used instead of a determination of usable oil as described above. If the usable quantity is not listed, it may be determined by contacting the engine manufacturer or conducting a usable oil test with the critical operating conditions.