737 Flight Crew Operations Manual
Supplementary Procedures -
Adverse Weather
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D6-27370-866-EGP SP.16.11
Note: Engine vibration can reduce to a low level before 80%
N1 is reached, however, thrust increase must continue
to a minimum of 80% N1 to remove ice from the fan
blades.
Note: Engine vibration can indicate full scale before
shedding ice, however, this has no adverse effect on
the engine.
If vibration does not decrease, accomplish the Engine High
Vibration checklist “If not in icing conditions.”
Wing Anti-ice Operation - In Flight
Ice accumulation on the flight deck window frames, windshield center
post, or on the windshield wiper arm may be used as an indication of
structural icing conditions and the need to turn on wing anti-ice.
In flight, the wing anti-ice system may be used as a de-icer or as an
anti-icer. The primary method is to use it as a de-icer by allowing ice to
accumulate before turning wing anti-ice on. This procedure provides the
cleanest airfoil surface, the least possible runback ice formation, and the
least thrust and fuel penalty. Normally it is not necessary to shed ice
periodically unless extended flight through icing conditions is necessary
(holding).
The secondary method is to use wing anti-ice before ice accumulation.
Operate the wing anti-ice system as an anti-icer only during extended
operations in moderate or severe icing conditions, such as holding.
CAUTION: Do not use wing anti-ice when TAT is above 10°C.
CAUTION: Use of wing anti-ice above approximately FL350 may
cause bleed trip off and possible loss of cabin
pressure.
Note: Prolonged operation in icing conditions with the leading edge
and trailing edge flaps extended is not recommended. Holding
in icing conditions with flaps extended is prohibited.
When wing anti-ice is needed:
WING ANTI-ICE switch ..................................... ON PM
Verify that the L and R VALVE OPEN lights illuminate
bright, then dim.
September 15, 2016
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