TM 55-1520-228-10
Change 11 8-15
4
If exhaust covers are missing or improperly
installed, rain or snow may enter the engine through the
exhaust stacks and subsequently freeze, causing the
N
1
and N
2
turbine blades to be imbedded in ice. If the
starter is activated under these circumstances, serious
engine damage may result. Visually inspect inside of the
exhaust collector (with a flashlight, if necessary) to en-
sure that no ice is present. Apply external heat to engine
until all visible ice in the exhaust collector is melted,
before attempting start.
(c) Oil tank compartment – Check free of ice,
frost, and snow.
(2) Interior check – All flights 0 degrees C (32
degrees F) to -54 degrees C (-65 degrees F). Perform
check as specified in Section II.
(3) Interior check – Night flights 0 degrees C (32
degrees F) to -54 degrees C (-65 degrees F). External
power connected. Perform check as specified in Section
II.
(4) Engine starting check 0 degrees C (32 de-
grees F) to -54 degrees C (-65 degrees F). Perform as
outlined in Section II.
CAUTION
In the fuel system, condensation and
freezing of moisture in pneumatic
circuits can occur when weather
conditions of low temperature and
high relative humidity are encoun-
tered. This condition can cause auto
acceleration of engine.
NOTE
Auto acceleration resulting from frozen
moisture in fuel system air circuits does
not repeat unless aircraft is again sub-
jected to cold soak. To prevent icing/
auto acceleration, make a 10 minute
ground warm-up run at idle before flight.
This warm-up is recommended when
aircraft has been allowed to cold soak in
low ambient temperatures of -12_C
(10_F) or below and high relative humid-
ity of 45% or greater.
If auto acceleration occurs, close the
throttle and shut down the engine. Sub-
sequently, restart the engine and re-
sume the warm-up.
NOTE
Due to the variation in types of jet fuel,
in cold weather the engine may experi-
ence a short delay before lightoff after
the throttle is advanced to idle position.
This delay should be less than three
seconds, regardless of the type of fuel
used.
NOTE
During cold weather, starting the engine
oil pressure gage may exceed 130 PSI.
The engine should be warmed up at en-
gine idle until the engine oil pressure
indication is below 130 PSI.
(5) Engine runup check. Perform the Check as
outlined in Section II. To prevent the possibility of auto-
acceleration after takeoff, the engine shall be operated
at idle for the times specified below before completing
runup procedures.
FAT (_C)
TIME (MINUTES)
-30 to -21 10
-20 to -11 7
-10 to -1 5
0 to +9 3
WARNING
Control system checks should be
performed with extreme caution
when helicopter is parked on snow
and ice. There is reduction in ground
friction holding the helicopter sta-
tionary; controls are sensitive and
response is immediate.
c. Engine Starting Without External Power Sup-
ply. If a battery start must be attempted when the heli-
copter and battery have been cold-soaked at
temperatures between -26 degrees C to -37 degrees C
(-15 degrees F to -35 degrees F), preheat the engine
and battery, if equipment is available and time permits.
Preheating will result in a faster starter cranking speed
which tends to reduce the hot-start hazard, by assisting
the engine to reach a self-sustaining speed.
d. Engine Anti-Icing. The ENG DEICE switch
should be in ENG DEICE position in visible moisture
below 5_ C FAT.
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