(3)
Check landing gear and wheel wells for packed ice or snow.
(4)
Check that all inlets are free from ice, snow.
(5)
Check that all drains are clear and free from obstructions.
(6)
Check engine compressor rotation. Also check the backside of the fan blades for ice.
NOTE: Extensive damage may result during an engine start if fan (N1) rotation is prevented by ice. N1 rotation must be checked prior to any engine start whenever water may have accumulated in the engine at freezing temperatures. Rotation of the low pressure (LP) rotor fan blades can be seen from the ground. If wind does not rotate the fan, it may be turned by hand. If rotation is to be checked by motoring the engine, follow the procedure for motoring given in Chapter 71, Maintenance Practices.
(7)
Make sure all of the doors, including the doors to the off-wing escape compartments, are clear of ice.
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8. Parking
A. The area in which an airplane is to be parked must be cleared of ice and snow. Chapter 10 provides detail parking procedures if weather conditions and length of parking duration warrant additional steps.
WARNING: IF SEVERE WINDS ARE EXPECTED, REFER TO CHAPTER 10 - MOORING, FOR STABILIZER POSITIONING.
B. When possible, face the airplane into the prevailing wind. Set the airplane control surfaces so that melting snow and rain will not run into balance bay areas where subsequent freezing can lock the control (Fig. 202).
(1)
Position wing flaps to full up.
(2)
Position stabilizer at 4 units.
C. Install all plugs and covers, where available, for intake or exhaust ducts and various appendages such as pitot tubes. Covers can be prevented from freezing to airplane by a light brush application of anti-icing fluid to the airplane surface before installing the cover.
CAUTION: EXAMINE ENGINE INTAKE AREAS IMMEDIATELY AFTER SHUTDOWN FOR PRESENCE OF ICE FORMATION WHICH SHOULD BE REMOVED WHILE ENGINE IS COOLING AND BEFORE ENGINE PROTECTIVE PLUGS AND COVERS ARE INSTALLED. IF PLUGS ARE INSTALLED BEFORE THE ENGINE HAS COOLED, RESIDUAL HEAT WITHIN THE ENGINE WILL MELT THE ICE TO WATER WHICH RUNS TO THE BOTTOM OF THE FAN SECTION. THIS REFREEZES AS THE ENGINE COOLS AND LOCKS THE FAN LOWER BLADE TIPS IN ICE.
9. Engine Operation
A. Detailed operation of the engines, in cold weather conditions, is given in Chapter 71 of the Maintenance Manual.
B. Chunks of ice and/or snow entering the engine inlet may damage internal engine parts. Remove all ice or snow from engine inlet ducts prior to starting engines.
C. Engine icing conditions may be anticipated when visible moisture such as clouds, fog, rain, snow, sleet or ice crystals are present during ground operations with static air temperature below 50°F. The engine/nacelle thermal anti-icing system should be used when these conditions exist.
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D. Check that no ignitable accumulation of fluids exists around exhaust areas prior to starting engines.
10. Fuel Icing
A. Percentage of water in aviation fuels depends largely on fuel storage and handling conditions. Fuels exposed to dampness or ordinary atmospheric conditions contain a larger percentage of water than those kept in tightly sealed containers. This water content, under high humidity and fluctuating temperature conditions, may be several gallons in every thousand gallons of fuel. As temperatures are reduced, solubility of water in fuel is also reduced resulting in water separating from fuel. This water will collect at the lowest point in the tank and freeze if temperature is low enough. If water has collected and frozen in sumps (indicated by a lack of flow from drain valves), heat (explosion proof hot air) should be applied to underside of wing in area of tank sumps until fuel drained is free of water.
CAUTION: IF YOU CAN DRAIN FUEL FROM DRAIN VALVE AFTER YOU APPLIED HOT AIR TO THE EXTERIOR FOR 3 TO 5 MINUTES, DO NOT THINK THAT ALL THE ICE IS MELTED. ICE ADJACENT TO THE DRAIN VALVE UNIT CAN MELT AND LET SOME WATER AND FUEL FLOW FROM THE DRAIN. BUT A PIECE OF ICE CAN STAY BEHIND. IF FUEL DOES NOT FLOW FROM THE DRAIN, CONTINUE TO APPLY HOT AIR FOR A SHORT TIME, AND FREQUENTLY DO A CHECK OF FLOW FROM THE DRAIN. CATCH FUEL IN A CONTAINER AND MAKE SURE ALL WATER IS REMOVED.
HEAT APPLIED TO THE SUMP DRAIN VALVES FOR OUTBOARD MAIN AND RESERVE TANKS WILL NOT REMOVE ICE WHICH HAS COLLECTED IN THE TANK SUMP OR IN DRAIN LINE BETWEEN TANK SUMP AND VALVE. TO REMOVE THIS ICE, YOU MUST PUT THE AIRPLANE IN A WARM HANGAR FOR SUFFICIENT TIME TO MELT ICE. THEN DRAIN SUMPS UNTIL THE WATER IS REMOVED.
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