TM 55-1510-222-10
5-32B. ICING LIMITATIONS (SEVERE).
W A R N I N G
Severe icing may result from environmental
conditions outside of those for which the
airplane is certificated. Flight in freezing
rain,
freezing drizzle, or mixed icing
conditions (supercooled liquid water and ice
crystals) may result in a build-up on
protective surfaces exceeding the capability of
the ice protection system, or may result in ice
forming aft of these protected surfaces. This
ice may not shed using ice protection systems,
and may seriously degrade the performance
and controllability of the airplane.
a. During flight, severe icing conditions that exceed
those for which the airplane is certificated shall be
determined by the following visual cues. If one or more of
these visual cues exists, immediately request priority
handling from air traffic control to facilitate a route or an
altitude change to exit the icing conditions:
(1) Unusually extensive ice accreted on the
airframe in areas not normally observed to collect ice.
(2) Accumulation of ice on the upper (or lower, as
appropriate) surface of the wing aft of the protected area.
(3) Accumulation of ice on the propeller spinner
farther aft than normally observed.
b. Since the autopilot may mask tactile cues that
indicate adverse changes in handling characteristics, use of
the autopilot is prohibited when any of the visual cues
specified above exist,
or when unusual lateral trim
requirements or autopilot trim warnings are encountered
while the airplane is in icing conditions.
NOTE
All icing detection lights must be operative prior
to flight into icing conditions at night. This
supersedes any relief provided by the master
minimum equipment list (MMEL) or equivalent.
5-33. OXYGEN REQUIREMENTS.
a. Oxygen requirements will be in accordance with AR
95-1.
b. Oxygen system data/duration tables are found in
Chapter 2.
5-34. CABIN PRESSURE LIMITS.
Maximum cabin differential pressure is 6.5 PSI.
5-35. CRACKED CABIN WINDOW / WIND-
SHIELD.
If a crack occurs in a single ply of a cabin exterior
window, the aircraft is limited to unpressurized flight. If a
crack occurs in both outer and inner plys of the cabin
exterior window, the aircraft shall not be flown unless
proper authorization is obtained for an unpressurized ferry
flight. If an outer ply crack occurs in a windshield, no
action is required in flight.
If an inner ply crack occurs in a windshield, or if
either/both plys of a cabin window becomes cracked in
flight, refer to Chapter 9, Emergency Procedures.
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