§23.903 Engines.

(a) Engine type certificate. (1) Each engine must have a type certificate. (2) Each turbine engine must either-- (i) Comply with Sec. 33.77 of this chapter in effect on October 31, 1974, or as later amended; or (ii) Be shown to have a foreign object ingestion service history in similar installation locations which has not resulted in any unsafe condition. (b) Turbine engine installations. For turbine engine installations-- (1) Design precautions must be taken to minimize the hazards to the airplane in the event of an engine rotor failure or of a fire originating inside the engine which burns through the engine case. (2) The powerplant systems associated with engine control devices, systems, and instrumentation must be designed to give reasonable assurance that those operating limitations that adversely affect turbine rotor structural integrity will not be exceeded in service. (c) The powerplants must be arranged and isolated from each other to allow operation, in at least one configuration, so that the failure or malfunction of any engine, or the failure or malfunction (including destruction by fire in the engine compartment) of any system that can affect an engine (other than a fuel tank if only one fuel tank is installed), will not-- (1) Prevent the continued safe operation of the remaining engines; or (2) Require immediate action by any crewmember for continued safe operation of the remaining engines. (d) Starting and stopping (piston engine). [(1) The design of the installation must be such that risk of fire or mechanical damage to the engine or airplane, as a result of starting the engine in any conditions in which starting is to be permitted, is reduced to a minimum. Any techniques and associated limitations for engine starting must be established and included in the Airplane Flight Manual, approved manual material, or applicable operating placards. For multiengine airplanes, means must be provided for stopping and restarting each engine in flight. For single engine airplanes, means must be provided for stopping the engine in flight after engine failure if overspeeding might be caused by windmilling of the propeller. (2) In addition, for commuter category airplanes, the following apply: (i) Each component of the stopping system on the engine side of the firewall that might be exposed to fire must be at least fire resistant. (ii) If hydraulic propeller feathering systems are used for this purpose, the feathering lines must be at least fire resistant under the operating conditions that may be expected to exist during feathering.] (e) Starting and stopping (turbine engine.) Turbine engine installations must comply with the following: (1) The design of the installation must be such that risk of fire or mechanical damage to the engine or the airplane, as a result of starting the engine in any conditions in which starting is to be permitted, is reduced to a minimum. Any techniques and associated limitations must be established and included in the Airplane Flight Manual, approved manual material, or applicable operating placards. [(2) A means must be provided for stopping combustion and rotation of any engine. All those components provided for compliance with this requirement, which are within any engine compartment on the engine side of the firewall, must be fire resistant. In addition, for commuter category airplanes, each component of the restarting system on the engine side of the firewall and those components that might be exposed to fire must be at least fire resistant. If hydraulic propeller feathering systems are used for this purpose, the feathering lines must be at least fire resistant under the operating conditions that may be expected to exist during feathering.] (3) It must be possible to restart an engine in flight. Any techniques and associated limitations must be established and included in the Airplane Flight Manual, approved manual material, or applicable operating placards. (4) It must be demonstrated in flight that when restarting engines following a false start, all fuel or vapor is discharged in such a way that it does not constitute a fire hazard. (f) Restart capability. An altitude and airspeed envelope must be established for the airplane for inflight engine restarting and each installed engine must have a restart capability within that envelope. (g) For turbine engine powered airplanes, if the minimum windmilling speed of the engines, following the inflight shutdown of all engines, is insufficient to provide the necessary electrical power for engine ignition, a power source independent of the engine-driven electrical power generating system must be provided to permit inflight engine ignition for restarting.