TM 1-1520-238-10 8-20 Change 8 f.  Based on an applied force of 75 lbs, the blade must be cycled one time at –32 C (–25 F), five times at –42 C (–44 F), and ten times at –54 C (–65 F). 8.38 ENGINE STARTING. NOTE During cold weather operations, FDLS 19 should be monitered during engine start and warm-up. The power control levers should remain at the idle position until the tempera- ture of the engine nose gearboxes indicates 20 C or above. When starting in cold weather below –40 C (–40 F), if light-off does not occur within 10 seconds after placing the PWR lever to IDLE, quickly move engine PWR lever for the affected engine to OFF and then to IDLE three times. Then, leave the PWR lever in IDLE. If light-off still does not occur within 40 seconds, abort start and do the follow- ing: 1. Engine PWR lever (affected engine) – Hold at LOCKOUT. 2. Fuel CROSSFEED switch – AFT TK. 3. Fuel BOOST switch ON. Check that ground crew verifies fuel flow from upper drain. 4. Engine PWR lever (affected engine) – OFF. 5. Attempt another start. 6. After engine start – CROSSFEED switch – NORM. 8.39 WARMUP AND GROUND TESTS. It is normal for engine oil pressure to be high during initial starts when oil is cold. Run engine at idle until oil pressure is within normal operating limits. Oil pressure should re- turn to the normal range within five minutes. However, time required for warmup will depend on temperature of the engine and lubrication system before start. During starts in extremely cold weather (near –54 C, –65 F), the following engine oil pressure characteristics are typical: a. Oil pressure may remain at zero from 20 to 30 sec- onds after initiating the start. Abort start if oil pressure does not register within one minute of initiating start. b. Once oil pressure begins to indicate on the gauge, it will increase rapidly and go over the 100 psig limit. The pressure will decrease as oil temperature rises and return to within the green band on the gauge. This condition is considered normal. The time for oil pressure to decrease to 100 psig or below will depend on the severity of the am- bient temperature, but it should be inside the green band within five minutes of starting the engine. c. Oil pressure may increase above the maximum pressure limit of 100 psig if the engine is accelerated above idle while oil temperature is below normal operating range. The pressure will decrease to within the normal op- erating range as oil temperature increases. d. The OIL BYP ENG 1 or 2 caution light normally goes on when starting an engine with oil below normal op- erating temperatures because of the relatively high oil vis- cosity and the amount of contamination in the oil filter. When oil temperature reaches about 38 C (100 F) dur- ing engine warmup, the light should go off. e. At temperatures between –17 C and –43 C (1 F and –45 F), warmup engines during engine run-up for three minutes. To eliminate any possibility of main rotor droop stop wear should the main rotor blades move through a pitch change angle while resting on the droop stop, the flight crew should observe the following: At a temperature of –42 C (–44 F) or below, and with a rotor speed of 100% N_r, maintain neutral cyclic position for one minute. Then move the cyclic forward one inch and hold for one minute. Move the cyclic forward one addition- al inch and hold for one minute. The total procedure re- quires three minutes after reaching normal rotor RPM and can be accomplished simultaneously with the engine war- mup procedures. 8.40 DESERT AND HOT WEATHER OPERATIONS. a. In sandy or dusty conditions, it is advisable to per- form the HIT check while airborne. b. Refer to FM 1-202, Environmental Flight. c. Refer to para 4.11 for FCC restrictions, when air- craft has been heat soaked in direct sunlight for more than an hour. 8.41 TURBULENCE AND THUNDERSTORM OPERATION. 8.41.1 Turbulence Operation: a. For moderate turbulence, airspeed should be less than 150 knots. b. For light turbulence, reduce airspeed, if desired, to minimize vibration.