Kazan Helicopters Mi-17-1V Flight Manual page 106

MI1·17-1B. Flight manual
from the ridge summit in case of sudden loss of altitude caused by in-
gress In downdraft.
The main indication of presence of severe down - and updrafts which
may constitute a flight safety hazard the heavy cumulus clouds occuring
over the mountains in day time. The most appropriate conditions for flying
in mountains are noted In morning and evening time.
(8) Crossing of mountain ridges in wind is accompanied by pronounced
bumpiness near the mountain slope.
When crossing the mountain ridge into the wind this bumpiness begins to
be percepted at higher distances from the ridge than when crossing it
downwind. The intensity of bumpiness increases as the helicopter ap-
proaches the mountain slope and if the height clearance above the ridge
summit in inadequate, flying may become unsafe due to severe down-
drafts.
(9) Lack of even fields and unobstructed clearways to them is a characteris-
tic feature of flying over highlands, therefore takeoffs and landings in
mountains on fields of limited dimensions require excellent piloting tech-
nique from the pilot and firm knowledge of peculiarities of flying in moun-
tains.
In determining the possibility to takeoff from and land on the selected field
the pilot should skilfully assess the situation and take a correct decision
proceeding from the specific terrain, dimension of the field and condition
of its surface, altitude above sea level, the nature of obstacles under
takeoff or landing flight path, as well as the wind direction and speed.
(10) Before flight in a ravine calculate the radii ofturns at various air-speeds at
the maximum bank angles for the actual conditions of flight,
Fly at a height of 50 to 100m above the ravine bottom keeping close to
one side of the ravine, better illuminated, to ensure possibility of turn in
the event of egress from ravine in the opposite direction.
Depending on the ravine width maintain such an airspeed that allows
execution a 180-degree turn at any moment of flight.
(11) In flight over highland area the radio altimeter gives unstable readings.
Reference
-totbe
radio altimeter readings only in flight over shallow even
slopes and when hovering over fields.
(12) Usage of the ADF involves difficulties due to mountain reflection effect.
The ADF errors in mountains are as high as +25 to
30°
and even more in
some cases.
The error magnitude depends on the height of the mountains, distance to
them, frequency at which a radio station transmits, absolute altitude of
the helicopter, and mutual position of mountains, helicopter and radio sta-
tion. To improve the accuracy of taking the bearing of the radio station
tune to radio stations transmitting at shorter waves (higher frequencies).
If the ADF readings are unstable abstain from determination of naviga-
tional elements by means of this instrument.
(13) Prepare and execute enroute flying in mountains following the recom-
m~ndations
covered In the Air Navigation Manual.
Determine the ground speed and drift angles by referring to the ground
speed and drift angle indicator of theAVlCC-15 doppler system.
In the highland areas there is the lack of reference objects required for
detailed orientation. Use mountain valleys, plateaus, characteristic moun-
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