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B.  To prevent snow or rain from blowing into engines, inlet covers should be fitted as soon as practical after engine operation. Exhaust covers should be fitted as soon as engine cool down permits.
C.  Unlike the reciprocating engine, the jet engine generally does not require preheating and starts can be made normally during cold weather operation. Prolonged cold soaks, however, can cause abnormal starting characteristics, erratic engine pressure ratio indications and restricted fuel flow. These conditions sometimes will require preheating of the engine.
2.  Equipment and Materials
A.  MIL-H-4607 - Heater, type H-1, or equivalent
B.  Generator Set, Power Unit - M32A60A - FSN 611-225-7663
NOTE:  Power unit is primarily for engine starting but is also extremely effective for snow and ice removal.
C.  Engine Inlet Cover - Boeing F72717, or equivalent.
D.  Engine Exhaust Cover -Boeing F80093, or equivalent.
NOTE:  Items C and D are flyaway equipment with each airplane.
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May 15/70  BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.  71-09-111 Page 201 

3.  Prepare for Cold Weather Starts
A.  Before starting an engine, check engine compressor for free rotation by rotating Nl rotor by hand in a counterclockwise direction (viewed from the front). If rotor cannot be turned, install inlet cover and attach a suitable hot air duct from a ground heater. Apply heat until compressor rotor rotates freely.
B.  Check compressor discharge pressure sensing line moisture trap and all sumps, strainers and filters in the fuel and oil systems for the presence of water or ice. As long as fuel will flow freely from the drain cocks in the tank sumps and strainers, it can be surmised that the system is free of ice. Refer to Chapter 12, Fuel Servicing.
4.  Cold Weather Starts
A. Start engine following procedure given in 71-09-100, Power Plant Operating Procedures.
CAUTION:  WHEN STARTING AN ENGINE WHICH HAS BEEN EXPOSED TO LOW TEMPERATURES OVERNIGHT, CAREFULLY OBSERVE FUEL AND OIL PRESSURES. ANY INDICATION BELOW THE NORMAL OPERATING LIMITS IS CAUSE FOR IMMEDIATE ENGINE SHUTDOWN. INSPECT ENGINE SYSTEMS FOR ICE. IF ICE IS PRESENT, SYSTEM SHOULD BE FREED OF ICE BEFORE ANOTHER START IS ATTEMPTED. IF THE AIRPLANE IS PARKED ON ICE OR PACKED SNOW, A LOW PRESSURE GROUND CART OR THE AUXILIARY POWER UNIT SHOULD BE USED FOR ENGINE STARTING SINCE ASYMMETRIC THRUST DURING CROSS-STARTS MAY CAUSE THE AIRPLANE TO SWING AROUND. ICE CHOCKS AND A HIGH GROSS WEIGHT WILL MINIMIZE THIS TENDENCY.
B.  If start is hot or engine hangs up and refuses to accelerate to IDLE, shut engine down and apply heat to fuel control for ten to twenty minutes.
NOTE:  If the compressor discharge pressure sensing line moisture trap, on the engine fuel control, is not drained periodically, moisture may collect in the burner pressure sensing bellows. Freezing of this moisture will restrict fuel flow to a fixed quantity. A low fuel flow will result in a hung start while a high fuel flow will cause a hot start.
CAUTION:  APPLICATION OF HEAT TO FUEL CONTROL SHOULD BE CONTROLLED SINCE EXCESSIVE HEAT MAY DISTORT INTERNAL PARTS OF FUEL CONTROL AND AFFECT FUEL SCHEDULING OF UNIT.
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C.  If no rotation of the N2 compressor is observed, check for seizure of the starter air control valve due to freezing of condensed moisture. The valve may be freed by local application of heat.
D.  When a successful start has been completed on an engine that has cold soaked for a prolonged period at temperatures below -30°F, allow the engine to idle for two minutes before advancing the thrust lever. This procedure is not absolutely necessary, however, it will allow the engine oil to warm up and ensure adequate lubrication of the engine bearings.
CAUTION:  IF THERE IS NO INDICATION OF OIL PRESSURE WITHIN 30 SECONDS OF ENGINE OPERATION OR IF PRESSURE DROPS TO ZERO AFTER A FEW MINUTES OF GROUND RUNNING, SHUT DOWN THE ENGINE AND INVESTIGATE.
E.  It is generally not necessary to preheat the hydraulic pumps, CSD, fuel/oil cooler, or oil tank. However, cold oil in the CSD will make the generator slow to develop steady power. Generator frequency should be allowed to stabilize before applying heavy electrical loads. One minute of operation is usually sufficient to warm up the CSD.
F.  During engine operation in cold weather, ice buildup on the engine inlet guide vanes, nose dome, and nose cowl will be indicated by a large variation in the engine pressure ratio (EPR) indication. This variation is due to ice formation on the Pt2 probe on the engine nose dome and if the icing is severe may also be caused by a distortion of the airflow to the engine inlet. An increase in EGT will become noticeable only in the final stages of inlet icing. When icing conditions are suspected and a large variation in EPR is observed, or the engine begins to surge, reduce power and turn on the thermal anti-icing system. Restore power only after it is reasonably certain that all ice has been eliminated.
　
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