(b)
Snow and ice must not collect in the engine inlet and must be removed.
(c)
During very cold weather operations, the covers will slow the heat loss from the engine and prevent the engine oil temperature from decreasing too fast.
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71-00-00
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BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
////////////////////////A / PW4000 SERIES /747-400 / ENGINES/MAINTENANCE MANUAL ////////////////////////
WARNING:_______ DO NOT GO NEAR THE INLET DURING THE OPERATION OF THE ENGINE.
STAND AT THE NOSE LANDING GEAR AND TALK TO THE FLIGHT
COMPARTMENT WITH THE INTERPHONE WHEN YOU MONITOR THE DANGEROUS
AREAS OF THE INLET FOR ICE. INJURY TO PERSONS AND DAMAGE TO
EQUIPMENT CAN OCCUR.
(5)
A quantity of ice that collects in the engine inlet is one of the dangerous conditions during cold weather engine operation.
(a)
Snow blown in the engine can become ice if it melts and then freezes again.
(b)
This ice can lock the rotor blades to the stator case.
(c)
If the ice becomes a layer on the rotor blades, the engine rotors will not be balanced.
(6)
Ice can collect on the engine parts (i.e. stators, guide vanes, fan blades, spinner, etc.) during the engine operation because of the large quantity of air that is moved by suction into the engine.
(a)
This condition is dangerous when you operate the engine at high power and static conditions on the ground.
(b)
The suction decreases the air pressure which decreases the air temperature.
(c)
The ice can collect in the inlet when water droplets hit the fan blades, the guide vanes, and the spinner and become cool during evaporation.
(7)
After the engine is shutdown, you must immediately install the inlet cover and thrust reverser plugs to prevent windblown snow or rain in the engines, and in very cold conditions, to keep the heat in the engine.
(a) You must install the turbine exhaust cover as soon as the engine is sufficiently cool to prevent damage to the cover.
(8)
It is recommended that the airplane is pointed in the wind when parked for a long time.
(9)
During heavy snowstorms, you must always shutdown the engine in forward thrust.
(a) This will prevent ice layers on the cascade vanes, the blocker doors, and linkages of the thrust reverser.
(10)
Usually, it is not necessary to heat the engine before you start the engine. Reliable starts can be done with the normal start procedures.
(a)
You must heat the engine to free rotors locked with snow and ice.
(b)
You must remove all the ice and snow from these areas: 1) The engine inlet panels. 2) The fan cowl panels. 3) The external surfaces and joints of the thrust reverser. 4) The acoustic panels of the inlet cowl. 5) The fan and turbine exhaust ducts.
(c)
You must heat the engine if the engine oil temperature is colder than -40°C (-40°F).
EFFECTIVITYùùùùùùùùùùùùùùùùùùùùùùùùùùùùùù. ú
71-00-00
ALL ú ú N01A Page 274 ú Feb 15/98
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
(11)
When it is very cold, the high viscosity oil in the thrust reverser opening system can cause the thrust reverser to close very slowly or cause a hydraulic lock in a check valve in the quick disconnect. If the thrust reverser closes slowly, apply hot air to the opening actuators and tubes and at the quick disconnect for the hand pump. To clear a hydraulic lock, pump the thrust reverser open a little, then try to close it again. Continue to apply hot air to warm the opening system and to open and close the thrust reverser a little until the thrust reverser is fully closed.
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