TM 1-1500-204-23-1
(5)
Preheat for accessories. At temperature
below -22°F (-
30oC), apply heat to batteries, feathering
pumps, master brake cylinder, and actuating cylinders.
Aircraft with constant speed drives for alternators should
have drives heated.
(6)
Heater placement. Prevent possible heat
loss during preheat period by placing heaters as close
as possible to aircraft, but avoid areas under fuel and oil
drains, vents, or supplies Inspect heater ducts for leaks.
Cover heater and ducts with noncombustible canvas
covers Provide adequate fire bottles In flight area.
CAUTION
Do not apply heat directly against
plastic or plexi-glass windshields or
windows. Directly applied heat will
cause
crazing,
cracking,
and
discoloration.
Remove
existing
snow deposits before heating crew
compartment. When cabin heat is
applied
on
the
ground
with
temperatures below freezing, the
snow
will
melt
and
cause
accumulation of Ice on top of
fuselage and windshields
(7)
Preheat off light compartment. Apply heat
to flight compartment and cabin to ensure operation of
instruments and equipment, reduce windshield frosting,
soften canopy seals, and Increase crew comfort. Heater
ducts may also be positioned so as to direct heated air
toward any valves found to be sticking. Preheat
vacuum pumps in aircraft employing vacuum-driven
Instruments to ensure low viscosity of oil In and around
pumps and to prevent pump drive shaft from shearing.
c.
Pre flight. The following procedures and
inspections shall be accomplished during preflight for
aircraft operating in arctic conditions.
(1)
During severe weather, delay removal of
engine covers, propeller covers, flight compartment
covers, and miscellaneous covers until just prior to
engine start. Leave wing and empennage covers in
place until just prior to taxiing.
CAUTION
Exercise care to prevent flow of
melted Ice into areas where freezing
would cause restricted movement of
flight controls and restricted flow of
air through vents. Where water flows
toward any of these areas, It shall be
mopped up Immediately.
(2) Inspect entire aircraft for snow, frost, or ice.
Any deposit can cause loss of lift and treacherous
stalling characteristics. Brush off loose snow or frost.
Remove remaining ice by spraying or brushing on a coat
of anti-icing and deicing-defrosting fluid, MIL-A-8243.
Work from upper surfaces downward to prevent
accumulation of ice on previously cleared surfaces.
(3)
When rapid frosting occurs after initial
removal, apply a coat of defrosting fluid to retard
accumulation of frost before taxiing. Also apply a coat
of defrosting fluid after the last flight of the day to help
retard further accumulation of ice, snow, or frost.
(4)
Inspect control surfaces for freedom of
operation. Sudden temperature drops will cause ice to
form on the inside of the surfaces as well as on the
outside. When evident that ice has formed on the inside
restricting control surface movement, remove by
application of heat.
(5)
Inspect windows and windshields for
cracks. To prevent cracking, open all windows before
removing aircraft from heated hanger.
(6)
Inspect fuel and oil tank caps and vents
and crank-case breathers for presence of ice, snow, or
frozen condensate. Plugged lines or vents can cause
collapsing fuel tanks and swelling of oil tanks.
(7)
Inspect wing and fuselage drains and
vents for ice and snow. Thaw clogged drains or vents.
(8) Inspect fuel and oil tank sumps for ice.
Where water condensate has frozen, heat to permit
drainage.
(9)
Inspect
hydraulic
reservoirs
for
evidence of freezing. If evident, apply heat to thaw.
(10)
Inspect cylinder struts and hydraulic
pistons for accumulation of dirt and ice. Ice and grit
which will damage cylinder strut packings shall be
removed. Pistons shall be wiped with a clean cloth
saturated in hydraulic fluid, MIL-H-5606.
(11)
Using an auxiliary power source, check
radios and electrically operated controls and equipment
for proper operation.
(12)
Inspect exposed limit switches and
microswitches for presence of Ice or snow and for
proper operation.
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