8.42.2 Turbulence.
a.
Recommended maximum turbulence penetration air-speeds. For moderate turbulence, limit airspeed to the MAX RANGE (Chapter 7) or Vne minus 15 knots, whichever is less.
b.
In turbulent air -Maintain constant collective and use the vertical situation indicator as the primary pitch instru-ment. The altimeter and vertical velocity indicator may vary excessively in turbulence and should not be relied upon. Airspeed indication may vary as much as 40 KIAS. By maintaining a constant power setting and a level-.ight at-titude on the vertical situation indicator, airspeed will re-main relatively constant even when erroneous readings are presented by the airspeed indicator.
8-24 Change 4
8.42.3 Ice and Rain Operation.
Operation in rain will result in signi.cant damage to the blade erosion kit materials and should be avoided.
At airspeeds greater than 120 KIAS or during periods of reduced rain intensity the windshield wipers may slow notice-ably. If this occurs, wipers must be parked immediately to avoid wiper motor failure.
8.42.4 In-Flight Icing.
Activation of anti-ice systems after entry into potential icing conditions creates the possibility of engine FOD caused by ice shedding. The ice detector has been de-signed primarily as a sensor to indicate the requirement for activation of the blade deice system.
a.
All anti-ice systems must be turned on prior to enter-ing visible moisture at ambient temperatures of 4°C (39°F) or less.
b.
If icing conditions are encountered, turn on all anti-icing equipment immediately. If torque required increases 20% above that required for level .ight at the airspeed being maintained before entering icing, exit the icing envi-ronment or land as soon as possible. A 20% torque increase indicates that normal autorotational rotor rpm may not be possible, should dual-engine failure occur.
c.
When the helicopter is equipped with an operating blade deice, and icing conditions are encountered, a recur-ring torque increase up to 14% per engine may be experi-
TM 1-1520-253-10
enced during normal operation of the blade deice system because of ice build-up. The crew should closely monitor engine instruments to prevent exceeding limits and/or rotor droop. Signi.cant power losses and increased fuel con-sumption will occur with the activation of engine inlet anti-icing systems. Refer to Chapter 7 for torque available. The main rotor hub and the blades collect ice before initiation of a deice cycle. When enough ice has collected on the blades, moderate vibration levels of short duration can be expected in controls and airframe during normal deicing cycles. If the blade deice system is not operating, unbalanced loads of ice, resulting from asymmetric shedding, may cause severe vibrations. However, these vibrations normally subside af-ter 30 to 60 seconds when ice from other blades is shed.
d.
When helicopter is equipped with external extended range fuel system turn on pressure to OUTBD fuel tanks. This will prevent ice accumulation and assure pneumatic pressure for fuel transfer.
NOTE
After pressurizing the external extended range fuel tanks, DO NOT TURN OFF if ambient temperature is below 4°C.
8.42.5 Ground Operations.
a.
Strong gusty winds may cause increased .apping of the main rotor blades during shutdown following an icing encounter, because the anti-.ap restrainers may be frozen in the .y position.
b.
During .ight in icing conditions when droop stop heaters are not installed or fail to operate properly, the droop stop hinges may become iced, resulting in the droop stops not returning to the static position during rotor coast down. When the droop stops do not return to the static position, the main rotor blades may droop to within 4 feet of the ground during shutdown. Strong gusty winds may also cause excessive .apping of the main rotor blades, pre-senting the additional hazard of potential contact with the aft fuselage. If the droop stops are suspected to be stuck in the .y position, caution must be taken during shutdown to be sure personnel remain clear of the helicopter.
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