23.1111 Turbine engine bleed air system (Amendment 23-17)
CAR 3 Cross-reference: None
ADC Cross-reference: 5.49
Paragraph 23.1111(a)
ADC Cross-reference: 5.49(a)
No specific policy is available as of December 31, 2002.
Paragraph 23.1111(b)
ADC Cross-reference: 5.49(b)
How can the bleed air effects on the engine and airplane be established?
The engine manufacturer provides information on the engine bleed air limits. This information should be used as a starting point for determining the effects on the installed engine and the airplane that are usually established through testing. It is important not to exceed the certificated engine limits as this could invalidate the engine certification for the installation required in § 23.903(a)(1).
Paragraph 23.1111(c)
ADC Cross-reference: 5.49(c)
No specific policy is available as of December 31, 2002.
EXHAUST SYSTEM
23.1121 General (Amendment 23-51)
CAR 3 Cross-reference: 3.615
ADC Cross-reference: 5.50
Are there any general guidelines for exhaust system installations?
Use the following guidelines for exhaust system installations:
1. Provide sufficient clearance and/or heat shielding between exhaust components and spark plugs, plug leads, mount isolators, induction systems, engine controls, fuel systems, and other heat-sensitive airframe components.
2. The exhaust system should be accessible for inspections. Adequately support all exhaust components such as tail pipes, heat exchangers, and mufflers.
3. Provide slip joints or other suitable components in the exhaust system to address thermal expansion and engine movement. Locate any such components so minor leakage does not impinge on components or contaminate the cabin air.
Related Material
AC 20-135, Powerplant Installation and Propulsion System Component Fire Protection Test Methods, Standards, and Criteria
Paragraph 23.1121(a)
ADC Cross-reference: 5.50(a)
What are acceptable means of compliance with § 23.1121(a)?
Compliance with § 23.1121(a) should be demonstrated through testing using any acceptable carbon monoxide detection method. The test should be conducted with the airplane’s heater system in operation if there is any possibility of the system containing carbon monoxide and with aircraft thermal deicing systems, if installed, in full operation.
The effect of different airplane configurations and flight and ground conditions on the induction of carbon monoxide into the passenger cabin should be considered in establishing the test procedures. Flight test guidance is provided in chapter 166 of AC 23-8B.
Is a system that employs a carbon monoxide (CO) detector to warn the pilot of unsafe concentrations during normal operations acceptable to show compliance with § 23.1121(a)?
No, a system with a CO detector to warn the pilot of unsafe concentrations is not sufficient to show compliance. Section 23.1121(a) requires that the system be designed to prevent CO contamination of the personnel compartment in the first place.
Related Material
AC 20-32B, Carbon Monoxide (CO) Contamination in Aircraft—Detection and Prevention
AC 23-8B, Flight Test Guide for Certification of Part 23 Airplanes
Paragraph 23.1121(b)
ADC Cross-reference: 5.50(b)
No specific policy is available as of December 31, 2002.
Paragraph 23.1121(c)
ADC Cross-reference: 5.50(c)
No specific policy is available as of December 31, 2002.
Related Material
AC 23-2, Flammability Tests
AC 20-107A, Composite Aircraft Structure
Paragraph 23.1121(d)
ADC Cross-reference: 5.50(d)
No specific policy is available as of December 31, 2002.
Paragraph 23.1121(e)
ADC Cross-reference: 5.50(f)
No specific policy is available as of December 31, 2002.
Paragraph 23.1121(f)
ADC Cross-reference: 5.50(e)
No specific policy is available as of December 31, 2002.
Paragraph 23.1121(g)
ADC Cross-reference: 5.50(g)
No specific policy is available as of December 31, 2002.
Paragraph 23.1121(h)
ADC Cross-reference: 5.50(h)
No specific policy is available as of December 31, 2002.
Paragraph 23.1121(i)
ADC Cross-reference: None
No specific policy is available as of December 31, 2002.
23.1123 Exhaust system (Amendment 23-43)
CAR 3 Cross-reference: 3.616
ADC Cross-reference: 5.51
Related Material
AC 20-135, Powerplant Installation and Propulsion System Component Fire Protection Test Methods, Standards, and Criteria
Paragraph 23.1123(a)
ADC Cross-reference: 5.51(a)
What are the general considerations relative to compliance with § 23.1123(a)?
Exhaust components are typically constructed of stainless steel or steel alloys of appropriate wall thickness to withstand the highly corrosive high temperature exhaust gases in order to comply with § 23.1123(a). Proper material selection and corrosion protective design should be performed and validated during certification. Analysis and validation tests are done to ensure thermal and structural integrity and to ensure thermal expansion does not cause structural overload, failure, unintentional contact of adjacent components, or hazardous heating of surrounding components. The thermal expansion analysis and test should be done at the maximum in-service temperature excursions expected for the installation.
Related Material
AC 23-2, Flammability Tests
Paragraph 23.1123(b)
ADC Cross-reference: 5.51(b)
What loading cases are typically considered?
Typically, the worst-case static design load conditions are either the inertia loads from an emergency impact, such as that specified in § 23.561, or combined loading from thermal expansion, in-flight deflections, and internal exhaust gas flow. The exhaust system components should be designed and supported to avoid critical frequencies and to minimize the effects of the vibration environment. Flight test vibration surveys may be necessary to properly define or validate the critical modes and vibration environment. In addition, the strength reduction in the system materials at the operating and worst-case 145
temperatures should be properly accounted for during the design and structural substantiation.
Paragraph 23.1123(c)
ADC Cross-reference: 5.51(c)
What should be considered in the design of an exhaust system with components having relative motion between them?
Section 23.1123(c) requires that exhaust system components with relative motion between them have a means for flexibility. This is typically provided by different types of flexible joints employing metal bellows, metal rings, or carbon rings. These components typically have limited lives because of the high temperatures and corrosive nature of the exhaust gases. For this reason, experience has shown that it is good to design the system to avoid relative motion between components to eliminate the use of these failure prone components.
23.1125 Exhaust heat exchangers (Amendment 23-17)
CAR 3 Cross-reference: 3.617, 3.618
ADC Cross-reference: 5.52
Paragraph 23.1125(a)
ADC Cross-reference: 5.52(a)
Does the heat exchanger require constant cooling airflow?
Yes, the intent of § 23.1125(a)(3) is to require cooling airflow when and where the exhaust gasses are in contact with the heat exchanger.
Paragraph 23.1125(b)
ADC Cross-reference: 5.52(b)
No specific policy is available as of December 31, 2002.
POWERPLANT CONTROLS AND ACCESSORIES
23.1141 Powerplant controls: General (Amendment 23-51)
CAR 3 Cross-reference: 3.627
ADC Cross-reference: 5.53
Related Material
AC 20-135, Powerplant Installation and Propulsion System Component Fire Protection Test Methods, Standards, and Criteria
AC 23-8B, Flight Test Guide for Certification of Part 23 Airplanes
Paragraph 23.1141(a)
ADC Cross-reference: 5.53(a)
Do single-lever power controls comply with § 23.1141?
Airplanes may be equipped with single-lever power controls (a control arrangement allowing the engine throttle, propeller pitch control, and possibly mixture control to operate via one lever) where the propeller pitch varies with engine r.p.m. by means of a mechanical cam or slider device as a function of throttle position. Any such propeller control system must be shown to have the level of integrity and reliability of a typical installation with independent propeller and throttle controls. Specific guidance for this is contained in the related material listed below under § 23.777.
Related Material
AC 23-17A, Systems and Equipment Guide for Certification of Part 23 Airplanes
Paragraph 23.1141(b)
ADC Cross-reference: 5.53(b)
No specific policy is available as of December 31, 2002.
Paragraph 23.1141(c)
ADC Cross-reference: 5.53(c)
No specific policy is available as of December 31, 2002.
Paragraph 23.1141(d)
ADC Cross-reference: 5.53(d)
No specific policy is available as of December 31, 2002.
Paragraph 23.1141(e)
ADC Cross-reference: 5.53(e)
Are there any special considerations for special purpose, restricted category, singleengine agricultural airplanes using the normal category requirements of part 23 as a certification basis?
It is acceptable for special purpose, restricted category, single-engine agricultural airplanes using the normal category requirements of part 23 as a certification basis to delete the phrase “or probable combination thereof” when demonstrating compliance with the rule as restated below.
This regulation currently reads as follows:
For turbine engine powered airplanes, no single failure or malfunction, or probable combination thereof, in any powerplant control system, may cause the failure of any powerplant function necessary for safety.
Paragraph 23.1141(f)
ADC Cross-reference: 5.53(f)
No specific policy is available as of December 31, 2002.
Related Material:
AC 23-2, Flammability Tests
Paragraph 23.1141(g)
ADC Cross-reference: 5.53(g)
No specific policy is available as of December 31, 2002.
23.1142 Auxiliary power unit controls (Amendment 23-43)
CAR 3 Cross-reference: None
ADC Cross-reference: None
No specific policy is available as of December 31, 2002.
23.1143 Engine controls (Amendment 23-51)
CAR 3 Cross-reference: 3.628
ADC Cross-reference: 5.54
Paragraph 23.1143(a)
ADC Cross-reference: 5.54(a)
No specific policy is available as of December 31, 2002.
Paragraph 23.1143(b)
ADC Cross-reference: 5.54(c)
No specific policy is available as of December 31, 2002.
Paragraph 23.1143(c)
ADC Cross-reference: 5.54(b)
No specific policy is available as of December 31, 2002.
Paragraph 23.1143(d)
ADC Cross-reference: 5.54(a)
No specific policy is available as of December 31, 2002.
Paragraph 23.1143(e)
ADC Cross-reference: None
This guidance may be used for Airship Certification as applicable.
No specific policy is available as of December 31, 2002.
Related Material:
AC 20-136, Protection of Aircraft Electrical/Electronic Systems Against the Indirect Effects of Lightning
Paragraph 23.1143(f)
ADC Cross-reference: 5.54(d)
No specific policy is available as of December 31, 2002.
Paragraph 23.1143(g)
ADC Cross-reference: None
This guidance may be used for Airship Certification as applicable.
What is the origin of this requirement?
This regulation was introduced with Amendment 23-43 on May 10, 1993, and originated as a proposal in response to the Small Airplane Airworthiness Review conducted in 1983 and 1984. This proposal was forwarded by the National Transportation Safety Board as a response to a study of single-engine aircraft accidents involving separation of the throttle linkages with subsequent loss of propulsive power. The original wording of the proposal stated the following:
“(f) A means must be provided to assure that if throttle linkage separation occurs in a single engine airplane, the fuel control will be automatically positioned at:
(1) The full throttle position for agricultural airplanes.
(2) An intermediate throttle position for other airplanes which will allow the pilot to maintain level flight in the cruise configuration.”
A review of the minutes of the Small Airplane Airworthiness Review Conference held in St. Louis, Missouri on October 22-26, 1984, reveals that the discussion was centered around the appropriate settings for different airplane classifications.
The rule as proposed and subsequently accepted in Amendment 23-43 states the following:
“(g) For reciprocating single-engine airplanes, each power or thrust control must be designed so that if the control separates at the engine fuel metering device, the airplane is capable of continued safe flight and landing.”
The generally accepted definition of “engine fuel metering device” is a device that controls the amount of fuel flow (fuel control in the original proposal) to the engine based on throttle position. The throttle refers to the device the pilot uses to set the desired engine power level.