TM 1-1510-223-10
Change 2 5-10.1
Section VII.
ENVIRONMENTAL RESTRICTIONS
5-30. ALTITUDE LIMITATIONS.
The maximum altitude that the aircraft may be oper-
ated at is 35,000 feet. When operating with inoperative
yaw damp, the altitude limit is 17,000 feet.
5-31. TEMPERATURE LIMITS.
a. The aircraft shall not be operated when the ambi-
ent temperatures are warmer than ISA +37 C at sea
level to 25,000 feet, or ISA +31 C above 25,000 feet.
b. Engine ice vanes shall be extended for operations
in ambient temperatures of +5 C or below when flight
free of visible moisture cannot be assured.
c. Minimum free air temperature for operation of de-
icing boots shall be -40 C.
5-32. FLIGHT UNDER IMC (INSTRUMENT METEO-
ROLOGICAL CONDITIONS).
This aircraft is qualified for operation in instrument
meteorological conditions.
5-33. ICING LIMITATIONS (TYPICAL).
WARNING
While in icing conditions, if there is an unex-
plained 30% increase of torque needed to
maintain airspeed in level flight, a cumulative
total of two or more inches of ice accumula-
tion on the wing, an unexplained decrease of
15 knots IAS, or an unexplained deviation
between pilot’s and copilot’s airspeed indi-
cators, the icing environment should be ex-
ited 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 accu-
mulation of ice on the pitot tube assemblies and unpro-
tected airplane surfaces. If any of these conditions are
observed, the icing environment should be exited as
soon as practicable.
a. 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 1/2-inch accu-
mulation.
b. A 30 percent increase in torque per engine re-
quired to maintain a desired airspeed in level flight (not
to exceed 85 percent torque) when operating at recom-
mended holding speed.
c. 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 sur-
face and antenna deice cycle is completed.
d. Any variations from normal indicated airspeed be-
tween the pilot’s and copilot’s airspeed indicators.
