TM 1-1520-238-10 Change 8 8-21 8.41.2 Thunderstorm Operation: a. Lightning strikes may result in the loss of the digital automatic stabilization equipment (DASE), stabilator con- trol, engine electronic control units, and helicopter electri- cal power. The high voltages passing through the helicop- ter structure are expected to couple into the helicopter wiring, producing secondary effects which cause degra- dation to the mission equipment. b. If a lightning strike occurs where all helicopter elec- trical power and engine electrical control units are lost, both engines will go immediately to maximum power out- put, as if in LOCKOUT. The flight crew shall have to react immediately to retard the PWR levers to IDLE and enter autorotation. The pilot could then advance the PWR lev- ers, restoring power, relying solely on rotor and engine sounds and general helicopter handling because of the high probability that all engine instruments would be inop- erative. 8.42 ICE AND RAIN. CAUTION Prolonged operation of the anti-ice/de- ice systems while on the ground may re- sult in damage. 8.42.1 Preflight/Runup. Prior to flight in icing condi- tions (visible moisture and below freezing temperatures), special care should be taken to ensure that all necessary anti-ice/de-ice systems are operational. The blade de-ice system may be checked by holding the BLADE de-ice switch, on the pilots ANTI-ICE panel (fig 2-17), to the TEST position. The BLADE ON advisory light, on the same panel, will illuminate for approximately 3 to 4 sec- onds. Additionally, the on-command FD/LS may be used to ensure proper system operation. The engine inlet and nose gearbox anti-ice system may be checked by moving the ENG INLET switch, on the pilots ANTI-ICE panel, to the ON position. The ENG 1 and ENG 2 ANTI-ICE lights on the pilots caution/warning panel will illuminate and re- main on until the fairing heaters reach operating tempera- ture. After approximately 30 to 40 seconds, the ENG 1 and ENG 2 ANTI-ICE lights on the pilots caution/warning panel will extinguish and the ENG 1 and ENG 2 advisory lights, on the pilots ANTI-ICE panel, will illuminate. 8.42.2 Inflight. Anti-ice/de-ice systems should be acti- vated prior to flight in potential icing conditions (visible moisture and below freezing conditions). a. The green BLADE, ENG 1, and ENG 2 advisory lights on the pilots ANTI-ICE panel should be illuminated. When actual icing conditions are encountered, the ENG ICE light on the caution/warning panel will illuminate and remain on during the icing encounter. The main and tail rotor blades will accumulate ice between heating cycles. This will result in approximately 6 to 10% increase in indi- cated torque (without collective movement). When the main and tail rotor blades heat and shed ice, there will be a slight momentary increase in airframe vibrations and the indicated torque will drop to approximately the original reading. b. Particular attention should be devoted to unusual torque rises or persistent airframe vibrations as these may be the first indications of a blade de-ice system malfunc- tion. Icing rates tend to vary, even over short distances, and may result in continuous changes in the indicated ic- ing rate on the ice rate meter. If continuous large erratic rate needle movements of more than 0.3 gm/m3 and/or large indicated torque rises are observed, recommend moving the de-ice mode switch (fig 2-17) to the manual MOD position, and depart the icing conditions. c. Prolonged flight in icing conditions will reduce air- craft maximum range. For fuel consumption, refer to Chapter 7 or Chapter 7A . d. After departing the icing conditions, recommend minimum use of the windshield wipers as shed ice may damage main rotors, tail rotors, and engines. 8.43 GROUND OPERATIONS DURING HIGH WINDS. WARNING The maximum wind velocity for rotor start or stops is 45 knots from any direc- tion. Ground operation of the helicopter in winds greater than 45 knots may cause the main rotor blades to contact the fuselage or the helicopter to roll over. a. If surface winds above 45 knots are anticipated, ground operations should cease and the helicopter should be hangared or moored in accordance with TM 1-1520-238-23. If the helicopter cannot be hangared or moored, and sufficient time exists to shut the