326
14 CFR Ch. I (1–1–24 Edition)
§ 25.1027
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.
§ 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 lubri-
cating 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 ac-
complish 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 pre-
vent 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]
C
OOLING
§ 25.1041
General.
The powerplant and auxiliary power
unit cooling provisions must be able to
maintain the temperatures of power-
plant 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 shut-
down, or both.
[Amdt. 25–38, 41 FR 55467, Dec. 20, 1976]
§ 25.1043
Cooling tests.
(a)
General. Compliance with § 25.1041
must be shown by tests, under critical
ground, water, and flight operating
conditions. For these tests, the fol-
lowing apply:
(1) If the tests are conducted under
conditions deviating from the max-
imum ambient atmospheric tempera-
ture, the recorded powerplant tempera-
tures must be corrected under para-
graphs (c) and (d) of this section.
(2) No corrected temperatures deter-
mined 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 § 25.1045.
(b)
Maximum ambient atmospheric tem-
perature. A maximum ambient atmos-
pheric temperature corresponding to
sea level conditions of at least 100 de-
grees F must be established. The as-
sumed temperature lapse rate is 3.6 de-
grees F per thousand feet of altitude
above sea level until a temperature of
¥
69.7 degrees F is reached, above which
altitude the temperature is considered
constant at
¥
69.7 degrees F. However,
for winterization installations, the ap-
plicant may select a maximum ambi-
ent atmospheric temperature cor-
responding to sea level conditions of
less than 100 degrees F.
(c)
Correction factor (except cylinder
barrels). Unless a more rational correc-
tion applies, temperatures of engine
fluids and powerplant components (ex-
cept cylinder barrels) for which tem-
perature limits are established, must
be corrected by adding to them the dif-
ference between the maximum ambient
atmospheric temperature and the tem-
perature of the ambient air at the time
of the first occurrence of the maximum
component or fluid temperature re-
corded during the cooling test.
(d)
Correction factor for cylinder barrel
temperatures. Unless a more rational
correction applies, cylinder barrel tem-
peratures must be corrected by adding
to them 0.7 times the difference be-
tween the maximum ambient atmos-
pheric temperature and the tempera-
ture of the ambient air at the time of
the first occurrence of the maximum
cylinder barrel temperature recorded
during the cooling test.
[Doc. No. 5066, 29 FR 18291, Dec. 24, 1964, as
amended by Amdt. 25–42, 43 FR 2323, Jan. 16,
1978]
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