Sec. 23.903 - Engines.
(a) Engine type certificate. (1)
Each engine must have a type certificate and must meet the applicable
requirements of part 34 of this chapter.
(2) Each turbine engine and its
installation must comply with one of the following:
(i) Sections 33.76, 33.77 and 33.78 of
this chapter in effect on December 13, 2000.
(ii) Sections 33.77 and 33.78 of this
chapter in effect on April 30, 1998, or as subsequently amended before
December 13, 2000; or
(iii) Section 33.77 of this chapter in
effect on October 31, 1974, or as subsequently amended before April 30,
1998, unless that engine's foreign object ingestion service history has
resulted in an unsafe condition; or
(iv) Be shown to have a foreign object
ingestion service history in similar installation locations which has not
resulted in any unsafe condition.
Note: §33.77 of this chapter in effect on
October 31, 1974, was published in 14 CFR parts 1 to 59, Revised as of
January 1, 1975. See 39 FR 35467, October 1, 1974.
(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
(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
(c) Engine isolation. 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. Means must be provided for --
(i) Restarting any engine of a
multiengine airplane in flight, and
(ii) Stopping any engine in flight,
after engine failure, if continued engine rotation would cause a hazard to
(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) There must be means for stopping
combustion within any engine and for stopping the rotation of any engine
if continued rotation would cause a hazard to the airplane. Each component
of the engine stopping system located in any fire zone must be fire
resistant. If hydraulic propeller feathering systems are used for stopping
the engine, the hydraulic feathering lines or hoses must be fire
(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 envelope. An altitude
and airspeed envelope must be established for the airplane for in-flight
engine restarting and each installed engine must have a restart capability
within that envelope.
(g) Restart capability. For
turbine engine powered airplanes, if the minimum windmilling speed of the
engines, following the in-flight 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 in-flight engine ignition for restarting.
[Amdt. 23-14, 38 FR 31822, Nov. 19, 1973, as
amended by Amdt. 23-17, 41 FR 55464, Dec. 20, 1976; Amdt. 23-26, 45 FR
60171, Sept. 11, 1980; Amdt. 23-29, 49 FR 6847, Feb. 23, 1984; Amdt.
23-34, 52 FR 1832, Jan. 15, 1987; Amdt. 23-40, 55 FR 32861, Aug. 10, 1990;
Amdt. 23-43, 58 FR 18970, Apr. 9, 1993; Amdt. 23-51, 61 FR 5136, Feb. 9,
1996; Amdt. 23-53, 63 FR 14798, Mar. 26, 1998; Amdt. 23-54, 65 FR 55854,
Sept. 14, 2000]