Federal Aviation Administration, DOT
Section 25.1023

Section 25.1043

Oil radiators.

(a) Each oil radiator must be able to
withstand, without failure, any vibration, inertia, and oil pressure load to
which it would be subjected in operation.
(b) Each oil radiator air duct must be
located so that, in case of fire, flames
coming from normal openings of the
engine nacelle cannot impinge directly
upon the radiator.
Section 25.1025

Oil valves.

(a) Each oil shutoff must meet the requirements of Section 25.1189.
(b) The closing of oil shutoff means
may not prevent propeller feathering.
(c) Each oil valve must have positive
stops or suitable index provisions in
the  - on -  and  - off -  positions and must
be supported so that no loads resulting
from its operation or from accelerated
flight conditions are transmitted to
the lines attached to the valve.
Section 25.1027

Propeller feathering system.

(a) If the propeller feathering system
depends on engine oil, there must be
means to trap an amount of oil in the
tank if the supply becomes depleted
due to failure of any part of the lubricating system other than the tank
itself.
(b) The amount of trapped oil must
be enough to accomplish the feathering
operation and must be available only
to the feathering pump.
(c) The ability of the system to accomplish feathering with the trapped
oil must be shown. This may be done
on the ground using an auxiliary
source of oil for lubricating the engine
during operation.
(d) Provision must be made to prevent sludge or other foreign matter
from affecting the safe operation of the
propeller feathering system.
[Doc. No. 5066, 29 FR 18291, Dec. 24, 1964, as
amended by Amdt. 25-38, 41 FR 55467, Dec. 20,
1976]

COOLING

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Section 25.1041

General.

The powerplant and auxiliary power
unit cooling provisions must be able to
maintain the temperatures of powerplant components, engine fluids, and

auxiliary power unit components and
fluids within the temperature limits
established for these components and
fluids, under ground, water, and flight
operating conditions, and after normal
engine or auxiliary power unit shutdown, or both.
[Amdt. 25-38, 41 FR 55467, Dec. 20, 1976]

Section 25.1043 Cooling tests.
(a) General. Compliance with Section 25.1041
must be shown by tests, under critical
ground, water, and flight operating
conditions. For these tests, the following apply:
(1) If the tests are conducted under
conditions deviating from the maximum ambient atmospheric temperature, the recorded powerplant temperatures must be corrected under paragraphs (c) and (d) of this section.
(2) No corrected temperatures determined under paragraph (a)(1) of this
section may exceed established limits.
(3) For reciprocating engines, the fuel
used during the cooling tests must be
the minimum grade approved for the
engines, and the mixture settings must
be those normally used in the flight
stages for which the cooling tests are
conducted. The test procedures must be
as prescribed in Section 25.1045.
(b) Maximum ambient atmospheric temperature. A maximum ambient atmospheric temperature corresponding to
sea level conditions of at least 100 degrees F must be established. The assumed temperature lapse rate is 3.6 degrees F per thousand feet of altitude
above sea level until a temperature of
Section69.7 degrees F is reached, above which
altitude the temperature is considered
constant at Section69.7 degrees F. However,
for winterization installations, the applicant may select a maximum ambient atmospheric temperature corresponding to sea level conditions of
less than 100 degrees F.
(c) Correction factor (except cylinder
barrels). Unless a more rational correction applies, temperatures of engine
fluids and powerplant components (except cylinder barrels) for which temperature limits are established, must
be corrected by adding to them the difference between the maximum ambient
atmospheric temperature and the temperature of the ambient air at the time
of the first occurrence of the maximum

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