8-4-30. Flight in Thunderstorms.
Flight in or in close proximity to thunderstorms is to be
avoided because of the accompanying severe turbu-
lence and restricted visibility. If a thunderstorm is inad-
vertently encountered during flight, the procedures for
flight in turbulent air are to be followed and the flight path
altered to leave the area. Should a thunderstorm be en-
countered during a night flight, the cockpit dome light
should be turned on with white light selected to minimize
the blinding effect of lightning. Refer to chapter 5 for
8-4-31. Ice and Rain.
The helicopter is equipped with pitot tube, AFCS yaw port
heating, and windshield anti-icing systems to enable safe
flight in light icing conditions. Operation of these systems
is described in Chapter 2. Additional information and
specific procedures are also included in this section un-
der Cold Weather Operations. The greatest damage
caused by ice accumulation is lowered rotor blade effi-
ciency resulting in decreased range and endurance. If
icing is encountered during IMC flight, consideration
must be given to reduced range and endurance due to
increased fuel consumption. Refer to chapter 5 for limita-
8-4-33. Exterior Inspection.
Refer to paragraph 8-2-10.
Taxi at slow speeds to ensure positive braking action
during turns. The forward tilt of the rotors will cause the
helicopter to continue moving forward if icy conditions
8-4-35. Before Takeoff.
When the takeoff is to be accomplished into possible
icing conditions, the following are to be accomplished as
part of the Before Takeoff Check.
ANTI-ICE switches ON. Refer to chapter 5 for limita-
8-4-36. During Flight.
Since all of the systems on this helicopter are of the
anti-icing rather than the de-icing type, always start sys-
tems at least 5 minutes before entering a suspect or
forecast icing area. In addition, engine icing can occur at
temperatures above freezing.
a. Extended flight in light icing conditions may result
in lateral and vertical vibrations caused by asymmetric
self-shedding of ice. Minor rotor blade damage may oc-
cur from ice shedding at 10_C and below. One-per-rev
lateral vibrations from asymmetric shedding at any tem-
perature may occur. If vibrations are encountered, air-
speed should be reduced and the aircraft should be flown
out of the icing area.
b. Extended flight in icing conditions can result in ice
accumulating on the helicopter heater fuel drain. If the
heater shuts down during icing, do not attempt restart
until ice is removed from the heater intake, exhaust, and
heater fuel drain.
8-4-37. Approach and Landing.
Accomplish a normal approach and landing; but if icing
is present, increased power will be required. The forward
and aft wheels accumulate ice, which can result in the
brakes freezing. If icing conditions have been encoun-
tered, a zero forward ground speed landing should be
It is considered that rain will have no detrimental effect on
the flight characteristics or performance of the helicopter.
The windshield wipers should be adjusted to FAST dur-
ing an instrument approach in rain, as rain may present
a restriction to visibility. Pitot heat should be used for
flights in rain to prevent moisture from accumulating in
the pitot tube and AFCS yaw ports and tubing.
8-4-39. Salt Water Operation.
8-4-40. Power Deterioration.
Salt spray ingestion in turbine engines may result in a
loss in performance as well as a loss in compressor stall
margin. This reduction in stall margin makes the engine
susceptible to stalls during acceleration, and more partic-
ularly, under deceleration conditions. As spray is in-
gested and strikes the compressor blades and stator
vanes, salt is deposited. The resulting buildup gradually
changes the airfoil sections, which in turn affects perfor-
mance. This deterioration will be noticed as a decrease
in torque and an increase in PTIT for a given N1. Should
the deterioration reach the point where the compressor
actually stalls, PTIT will increase, while N1 and torque
will decrease. The circumstances under which power
deterioration may occur during salt water operation vary
with a number of factors. The flight regime, gross
weight,wind direction and velocity, pilot technique, dura-
tion of maneuver, salinity of the water, and the relative
density of the salt spray, all have a bearing on perfor-
mance deterioration. Intermittent operation in moderate
salt spray conditions could expose the engines to
enough salt spray to cause noticeable performance de-
terioration. During prolonged operations (such as low
hovering) in heavier spray conditions, power deteriora-
tion will be apparent and is more critical. Maneuvers such
as hovering close to the water in light winds, or low flights
at low speeds will generate maximum rotor downwash
spray conditions. Careful operation, following the proce-
dures and limitations contained herein, in strict adher-
ence to the prescribed maintenance procedures when