Copyright . The Boeing Company. See title page for details.
Supplementary Procedures -Adverse Weather 737 Flight Crew Operations Manual
WING ANTI–ICE switch ..................................... As needed PM The wing anti–ice system may be used as a de–icer or anti–icer in flight only. 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. The secondary method is to use wing anti––ice prior to 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.
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.
Normally it is not necessary to shed ice periodically unless extended
flight through icing conditions is necessary (holding.)
CAUTION: Use of wing anti-ice above approximately FL350 may cause bleed trip off and possible loss of cabin pressure.
When wing anti–ice is needed:
WING ANTI-ICE switch.......................................ON PM
Verify that the R and L VALVE OPEN lights illuminate bright, then dim.
When wing anti–ice is no longer needed:
WING ANTI–ICE switch .....................................OFF PM
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.
Approach and Landing
Use normal procedures and reference speeds unless a flaps 15 landing is planned.
If a flaps 15 landing will be made:
Set VREF 15
Copyright . The Boeing Company. See title page for details.
Supplementary Procedures -Adverse Weather 737 Flight Crew Operations Manual
If any of the following conditions apply, set VREF ICE = VREF
15 + 10:
.
engine anti–ice will be used during landing
.
wing anti–ice has been used any time during the flight
.
icing conditions were encountered during the flight and the landing temperature is below 10° C.
Taxi–In
Do the following steps:
If prolonged operation in icing conditions with the leading and trailing edge flaps extended was needed:
Flaps ............................................................................. 15 F/O Retraction to less than flaps 15 is not recommended until ice has been removed or a ground inspection has been made.
Engine anti–ice ......................................................As needed F/O If icing conditions exist, engine anti–ice must be ON.
If taxi-in is delayed and icing conditions exist, do the following:
Engine run-up ...................................................As needed
Run-up to as high a thrust setting as practical (70% N1 recommended) at 30 minute intervals for approximately 30 seconds duration.
If airport surface conditions and the concentration of aircraft do not permit the engine thrust level to be increased to 70%, then set a thrust level and time at that thrust level as high as practical.
Note: When operating in conditions of freezing rain, freezing drizzle, freezing fog or heavy snow, additional momentary run-ups to 70% N1 at intervals of 10 minutes or less should be considered.
Shutdown Procedure
Do the following step before starting the normal Shutdown Procedure:
Copyright . The Boeing Company. See title page for details.
Supplementary Procedures -Adverse Weather 737 Flight Crew Operations Manual
After landing in icing conditions:
Stabilizer trim............................................Set 0 to 2 units Prevents melting snow and ice from running into balance bay areas and prevents the stabilizer limit switch from freezing. With flaps retracted, this requires approximately eight hand wheel turns of manual trim.
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