TM 1-1520-240-108-4-1SECTION IV. ADVERSE ENVIRONMENTAL CONDITIONS8-4-1. Cold Weather Operation.Refer to FM 1-202, Environmental Flight.8-4-2. General.Operating the helicopter in an environment of extremelow temperature and the associated weather phenome-na requires that certain techniques and operating proce-dures be implemented in addition to the normal operatingprocedures in Section II. The following operating tech-niques and procedures have been developed from actu-al arctic flight testing and other pertinent information.8-4-3. Preparation for Flight.The following additional exterior checks are to be per-formed during cold weather operation.a. Check that all ice, snow, and frost have been re-moved from the exterior surfaces, particularly the rotorblades.CAUTIONIce removal should never be accom-plished by chipping or scraping. Deicingfluid should be used.b. Landing gear shock struts, wheel brakes and flightcontrol system actuators should be checked to makecertain that exposed piston areas are free of dirt, ice,etc.c. While checking the engines, the compressorshould be manually checked for freedom of rotation.Heat must be applied if the compressor is frozen.d. When operating the ramp, it may be necessary tocycle it once or twice to achieve proper closure.e. Ensure that the manually operated vent valves onthe rotary-wing shock absorbers are open at tempera-tures below –18_C.At temperatures between –18_Cand–1_C, the vent valves may be opened or closed.At tem-peratures above–1_C, the vent valves must be closed.f. If seasonal temperatures are +4_C and below, theaft rotor droop stop shrouds should be installed.g. At temperatures below –18_C, preheating aircraftis recommended for a minimum of1–1/2 hours. Empha-sis should be placed on engine fuel control units.h. Refer to Chapter 5 for icing limitations.8-4-4. Heater Normal Operation.CAUTIONCycling of the heater blower may disablepower steering control.a. Starting.1. Inlet and outlet coverers — Remove.2. BATT switch — ON.3. APU — Start (para. 8-2-18).4. APU GEN switch — ON. RECT OFF cautioncapsule extinguishes.5. R (right) MAIN FUEL PUMP switches — ON(only if heater is to started).CAUTIONPull the cockpit air knobs slowly to pre-clude dirt and debris from being blastedinto the air and pilot’s eyes.6. Push in the air control knobs.7. Heater function switch — As desired (BLWR ONLY or HTR ON if BLWR only, steps 8 and 9 below donot apply).8. HTR START switch — Press.NOTEIf the left side of the helicopter is exposed tothe sun, the cabin thermostat may be heatedto 34_C which is sufficient to prevent startingthe heater.9. CABIN TEMP SEL switch — As desired.b. Heat Distribution.1. For maximum cockpit heat proceed as fol-lows:(a) Pilot and copilot cockpit air control knobs— Pull.(b) DEFOG or DEFROST handle — Pull.(c) CABIN AIR handle — Push.(d) CABIN TEMP SEL switch — Full clock-wise.2. For maximum cabin heat proceed as follows:(a) Pilot and copilot cockpit air control knobs— Push.(b) DEFOG or DEFROST handle — Push.
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