Cold Weather Operations - Boeing
AAVA – FLIGHT OPERATIONS MANUAL
COLD WEATHER OPERATIONS – BOEING 737 SERIES (73x)
FOR FLIGHT SIMULATION USE ONLY
1.0 GENERAL
This section defines cold weather operational standards for all AAVA Boeing 737 series aircraft (including 737-700/800/900 variants). Procedures reflect Boeing FCOM/FCTM guidance and simulation-appropriate best practices.
Cold weather operations apply when any of the following exist:
– OAT/TAT at or below 10°C
– Visible moisture (rain, snow, ice crystals, fog)
– Frost or ice present on aircraft surfaces
– Operations from contaminated taxiways or runways
The Clean Aircraft Concept applies at all times.
2.0 CLEAN AIRCRAFT CONCEPT
An aircraft must not depart unless all critical surfaces are free from contamination.
The Captain is responsible for confirming the aircraft is clean after deicing/anti-icing and prior to takeoff.
2.1 CRITICAL SURFACES
The following must be free of frost, ice, snow, or slush:
– Wing leading edges, upper wing surfaces
– Horizontal stabilizer, elevators
– Vertical stabilizer, rudder
– Slats, flaps, flap tracks
– Engine inlets, spinner, fan blades
– AoA vanes, pitot probes, static ports
– Flight controls and fairings
2.2 CLEAN AIRCRAFT VERIFICATION
A Clean Aircraft Check is required when:
– Frozen precipitation continues after deicing
– Holdover time is near expiration
– A delay occurs after deicing
– Fluid effectiveness is uncertain
Verification may be completed from:
– Flight deck (within HOT)
– Cabin overwing windows (HOT expired or heavy precipitation)
Left wing root is used as the reference point (first area sprayed, oldest fluid).
3.0 GROUND DEICING / ANTI-ICING
3.1 OVERVIEW
Deicing removes contamination.
Anti-icing protects against further accumulation.
Clear coordination between Flight Crew and Ground Deicing Personnel is required.
3.2 APPROVED FLUID TYPES
Type I Fluid
– Hot glycol mixture
– Used primarily for deicing
– Short holdover time
– Smooth glossy appearance indicates active protection
Type IV Fluid
– Thickened, long-lasting anti-ice fluid
– Applied after Type I
– Provides extended protection before takeoff
– Designed to shear off during takeoff roll
3.3 HOLDOVER TIME (HOT)
Holdover Time begins when the final anti-icing application starts.
HOT expires when the fluid can no longer prevent frozen contamination.
Precipitation anticipated at application time affects HOT selection.
3.4 ENGINE & AIRFRAME CONFIGURATION
Engines Running Deicing
– May be conducted only when the spray zone is safe
– Crew and Ground Team must coordinate carefully
– If APU is inoperative, crew may shut down the engine on the side being sprayed
– Perform crossbleed start after completion
Flaps During Deicing
The Boeing 737 uses flap angles (1°, 5°, 10°, 15°, 25°, 30°, 40°).
– For uniform protection, extend flaps to 15° prior to deicing when contamination on flap areas exists
– If contamination is present on upper wing surfaces, extending to 15° does not risk damage
– If flaps remain at 15° for flap-area contamination removal, do not retract until contamination is removed
CAUTION:
Retracting flaps below 15° with contamination present can cause flap track damage.
4.0 IN-FLIGHT ICING OPERATIONS
4.1 WING ANTI-ICE OPERATION
Boeing WAI may be used in two ways:
Primary Method — Deicer Mode
Activate WAI when ice is observed on:
– Window frames
– Wiper arms
– Side window posts
– Wing leading edges
This method:
– Produces clean leading edges
– Minimizes runback ice
– Reduces fuel and thrust penalties
Secondary Method — Anti-Icer Mode
Use WAI before ice accumulation during prolonged exposure in moderate or severe icing.
General Notes
– WAI is unnecessary below –40°C SAT
– Turn WAI OFF when clear of icing
– Avoid prolonged icing operation with flaps extended
5.0 ENGINE ANTI-ICE (EAI)
EAI must be used when:
– OAT/TAT ≤ 10°C and visible moisture exists
– Ice is detected or suspected
– Conditions conducive to icing exist
Indicators of engine icing:
– Fan vibration
– Increasing EGT at constant thrust
– N1/N2 instability
– Engine spool-up sluggishness
Use ENGINE ANTI-ICE switches ON as required.
6.0 DESCENT IN ICING CONDITIONS
When descending or holding in moderate or severe icing with low thrust:
Every ~15 minutes:
– Increase thrust on each engine separately to a minimum of 70–80% N1
– Maintain increase for several seconds
This sheds ice from:
– Spinner
– Fan blades
– Inlet lips
7.0 APPROACH, LANDING & CONTAMINATED RUNWAY OPERATIONS
7.1 FLAP RETRACTION AFTER LANDING (BOEING 737)
If ice accumulation is present after landing:
– Do not retract flaps below 15°
– Maintain flaps at 15° until ice is removed from:
– Flap surfaces
– Tracks
– Fairings
Once contamination is removed, flaps may be retracted to UP.
7.2 REVERSE THRUST USE
On slippery or contaminated runways:
– Use reverse thrust as required for a safe stop
– Reduce reverse thrust smoothly below 60 kt, depending on deceleration rate
7.3 TAKEOFF FROM CONTAMINATED RUNWAYS
– Use maximum takeoff thrust
– Within 5 minutes of takeoff:
– Perform an engine run-up to ~50% N1 for at least 5 seconds
– Confirm stable engine operation
– During a rejected takeoff, rudder provides primary directional control to approximately 60 kt
7.4 SAFETY PRIORITY
During landing or a rejected takeoff in contamination:
Stopping the aircraft is always the highest priority.