spaschal on DSK3GDR082PROD with CFR

Section 25.904

14 CFR Ch. I (1-1-19 Edition)

1984, unless that engine-s ice accumulation service history has resulted in an
unsafe condition; or
(iv) Be shown to have an ice accumulation service history in similar installation locations which has not resulted
in any unsafe conditions.
(b) 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
of any system that can affect the engine, will not - 
(1) Prevent the continued safe operation of the remaining engines; or
(2) Require immediate action by any
crewmember for continued safe operation.
(c) Control of engine rotation. There
must be means for stopping the rotation of any engine individually in
flight, except that, for turbine engine
installations, the means for stopping
the rotation of any engine need be provided only where continued rotation
could jeopardize the safety of the airplane. 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. 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.
(d) 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 within 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 engine operating limitations
that adversely affect turbine rotor
structural integrity will not be exceeded in service.
(e) Restart capability. (1) Means to restart any engine in flight must be provided.
(2) An altitude and airspeed envelope
must be established for in-flight engine
restarting, and each engine must have

a restart capability within that envelope.
(3) 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.
(f) Auxiliary Power Unit. Each auxiliary power unit must be approved or
meet the requirements of the category
for its intended use.
[Doc. No. 5066, 29 FR 18291, Dec. 24, 1964, as
amended by Amdt. 25-23, 35 FR 5676, Apr. 8,
1970; Amdt. 25-40, 42 FR 15042, Mar. 17, 1977;
Amdt. 25-57, 49 FR 6848, Feb. 23, 1984; Amdt.
25-72, 55 FR 29784, July 20, 1990; Amdt. 25-73,
55 FR 32861, Aug. 10, 1990; Amdt. 25-94, 63 FR
8848, Feb. 23, 1998; Amdt. 25-95, 63 FR 14798,
Mar. 26, 1998; Amdt. 25-100, 65 FR 55854, Sept.
14, 2000; Amdt. 25-140, 79 FR 65525, Nov. 4,
2014]

Section 25.904 Automatic takeoff thrust control system (ATTCS).
Each applicant seeking approval for
installation of an engine power control
system that automatically resets the
power or thrust on the operating engine(s) when any engine fails during
the takeoff must comply with the requirements of appendix I of this part.
[Amdt. 25-62, 52 FR 43156, Nov. 9, 1987]

Section 25.905

Propellers.

(a) Each propeller must have a type
certificate.
(b) Engine power and propeller shaft
rotational speed may not exceed the
limits for which the propeller is certificated.
(c) The propeller blade pitch control
system must meet the requirements of
SectionSection 35.21, 35.23, 35.42 and 35.43 of this
chapter.
(d) Design precautions must be taken
to minimize the hazards to the airplane
in the event a propeller blade fails or is
released by a hub failure. The hazards
which must be considered include damage to structure and vital systems due
to impact of a failed or released blade

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