TM 55-1510-219-10
SECTION VII. ENVIRONMENTAL RESTRICTIONS
5-29. ALTITUDE LIMITATIONS.
The maximum altitude that the aircraft may be operated
at is 31,000 feet. When operating with inoperative yaw
damp, the altitude limit is 17,000 feet.
5-30. TEMPERATURE LIMITS.
a The aircraft shall not be operated when the ambient
temperatures are warmer than ISA +37°C at SL to 25,000
feet, or ISA +31°C above 25,000 feet.
b. Engine ice vanes shall be retracted at +15°C and
above.
5-31. FLIGHT UNDER IMC (INSTRUMENT
METEOROLOGICAL CONDITIONS).
This aircraft is qualified for operational in instrument
meteorological conditions.
5-31A. ICING LIMITATIONS (TYPICAL).
W A R N I N G
While in icing conditions, if there is an
unexpected 30% increase of torque needed
to maintain airspeed in level flight, a
cumulative total of two or more inches of ice
accumulation on the wing, an unexplained
decrease of 15 knots IAS, or an unexplained
deviation between pilot’s and copilot’s
airspeed indicators, the king environment
should be exited as soon as practicable. Ice
accumulation on the pitot tube assemblies
could cause a complete loss of airspeed
indication.
The following conditions indicate a possible
accumulation of ice on the pitot tube assemblies and
unprotected airplane surfaces. If any of these conditions
are observed, the icing environment should be exited as
soon as practicable.
1. Total ice accumulation of two inches or more on the
wing surfaces. Determination of ice thickness can be
accomplished by summing the estimated ice thickness on
the wing prior to each pneumatic boot deice cycle (e.g. four
cycles of minimum recommended ½-inch accumulation.
2. A 30 percent increase in torque per engine required
to minimum an desired airspeed in level flight (not to
exceed 85 percent torque) when operating at recommended
holding speed.
3. A decrease in indicated airspeed of 15 knots after
entering the icing condition (not slower than 1.4 power off
stall speed) if maintaining original power setting in level
flight. This can be determined by comparing pre-icing
condition entry speed to the indicated speed after a surface
and antenna deice cycle is completed.
4. Any variations from normal indicated airspeed
between the pilot’s and copilot’s airspeed indicators.
5-8.2
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