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This section informs the crewmembers of the special
precautions and procedures to be followed during the
various weather and climatic conditions that may be
encountered. This material will be additional to that
already covered in other chapters regarding the operation
of various helicopter systems.
8.36 COLD WEATHER OPERATION.
Helicopter operation in cold weather or an arctic environment
presents no unusual problems if the flight
crew is aware of the various changes that occur in low
temperature conditions.
8.37 PREPARATION FOR FLIGHT.
Ice removal shall never be done by
scraping or chipping. Remove ice by
applying heat or de-ice liquid
(TM 1-1500-204-23).
In addition to doing a normal preflight in Section 11, the
rotor head, main rotor blades, tail rotor, and flight controls
should be free of all ice and snow. Failure to remove
snow and ice accumulations while on the ground
can result in serious aerodynamics and structural effects
in flight. Check that all fuel tank vents, static
ports, pitot tubes, engine inlet, APU inlet, ENCU inlet,
and heat exchangers are free of snow and ice; and that
tires, landing gear struts, and the hydraulic accumulator
are properly serviced.
a. If ice or snow is found in engine inlets and exhaust,
remove as much as possible by hand and thaw
engine out with hot air before attempting to start. Actuate
PWR levers for freedom of movement before starting
main engine.
b. Attempt to turn rotor system by rotating APU
drive shaft by hand in the direction of rotation. If rotor
cannot be turned, apply heat to main transmission
area.
c. As long as fuel will flow freely from the drains in
the tanks, it can be assumed that the system is free of
Fuel draining from the affected component
after several minutes of heat
application does not necessarily indicate
that all ice has been melted. Ice
may still remain in the unit, and it
could be a serious hazard to flight operations.
Heat should be applied for a
short time after fuel begins to flow
from the drain, and the drainage
should be checked frequently until it
is evident that all water has been removed.
d. If water collected in sumps has frozen (indicated
by a lack of flow from drain), apply heat liberally and
open drain frequently. Catch all drainage in a clear container
and inspect for water globules in the fuel. Continue
sampling until fuel is free of water globules.
Due to an elapsed time requirement,
it is recommended that the tail rotor
teetering bearings warmup procedure
be accomplished as the last item
of the exterior check during the
flight crew preflight inspection. At
-31 °C (-24 °F), the helicopter must be
started and the tail rotor must be
turning within 5 minutes of teeter
bearing warmup. Below -32 °C (-25
°F), elapsed time is reduced to 2 minutes.
At a temperature of -32 °C (-25
°F) or below, the tail rotor must be
cycled by an applied force no greater
than 75 lbs.
The tail rotor teetering bearings are made of elastomeric
material which prior to certain cold weather flights
require special warmup procedures as follows:
e. One crewmember should apply a teetering motion
by manually pushing back-and-forth at the tip of
the tail rotor blade until the blade has reached its teetering
stops. When the blade can be pushed to the top,
the bearing has been sufficiently warmed up.
8-19
TM 1-1520-238-10
f. Based on unapplied force of 75 lbs, the blade
must be cycled one time at -32 °C (-25 °F), five times at
-42 °C (-44 °F), and ten times at -54 °C (-65 °F).
8.38 ENGINE STARTING.
When starting in cold weather below -40 °C (-40 °F), if
light-off does not occur within 10 seconds after placing
the PWR lever to IDLE, quickly move engine PWR lever
for the affected engine to OFF and then to IDLE
three times. Then, leave the PWR lever in IDLE. If
light-off still does not occur within 40 seconds, abort
start and do the following:
1.
2.
3.
4.
5.
6.
Engine PWR lever (affected engine) - Hold at
LOCKOUT.
Fuel CROSSFEED switch - AFT TK.
Fuel BOOST switch ON. Check that ground
crew verifies fuel flow from upper drain.
Engine PWR lever (affected engine) - OFF.
Attempt another start.
After engine start - CROSSFEED switch -
NORM. -
8.39 WARMUP AND GROUND TESTS.
It is normal for engine oil pressure to be high during
initial starts when oil is cold. Run engine at idle until
oil pressure is within normal operating limits. Oil pressure
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