Windshear General
Improper or ineffective vertical flight path control has been one of the primary factors in many cases of flight into terrain. Low altitude windshear encounters are especially significant because windshear can place the crew in a situation which requires the maximum performance capability of the airplane. Windshear encounters near the ground are the most threatening because there is very little time or altitude to respond to and recover from an encounter.

Airplane Performance in Windshear
Knowledge of how windshear affects airplane performance can be essential to the successful application of the proper vertical flight path control techniques during a windshear encounter.
The wind component is mostly horizontal at altitudes below 500 feet. Horizontal windshear may improve or degrade vertical flight path performance. Windshear that improves performance is first indicated in the flight deck by an increasing airspeed. This type of windshear may be a precursor of a shear that decreases airspeed and degrades vertical flight path performance.

737 Flight Crew Training  Manual
Airspeed decreases if the tailwind increases, or headwind decreases, faster than the airplane is accelerating. As the airspeed decreases, the airplane normally tends to pitch down to maintain or regain the in-trim speed. The magnitude of pitch change is a function of the encountered airspeed change. If the pilot attempts to regain lost airspeed by lowering the nose, the combination of decreasing airspeed and decreasing pitch attitude produces a high rate of descent. Unless this is countered by the pilot, a critical flight path control situation may develop very rapidly. As little as 5 seconds may be available to recognize and react to a degrading vertical flight path.
In critical low altitude situations, trade airspeed for altitude, if possible. An increase in pitch attitude, even though the airspeed may be decreasing, increases the lifting force and improves the flight path angle. Proper pitch control, combined with maximum available thrust, utilizes the total airplane performance capability.
The crew must be aware of the normal values of airspeed, altitude, rate of climb, pitch attitude and control column forces. Unusual control column force may be required to maintain or increase pitch attitude when airspeed is below the in-trim speed. If significant changes in airspeed occur and unusual control forces are required, the crew should be alerted to a possible windshear encounter and be prepared to take action.

Avoidance, Precautions and Recovery
Crew actions are divided into three areas: Avoidance, Precautions and Recovery. For more information on avoidance and precautions, see the Windshear supplementary procedure in Volume 1 of the FCOM. For specific crew actions for recovery, see the Non-Normal Maneuvers section in the QRH.
Copyright . The Boeing Company. See title page for details.
7.38 FCT 737 (TM) October 31, 2006

Preface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.1
Non-Normal Situation Guidelines . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.1
Troubleshooting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.2 Approach and Landing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.3 Landing at the Nearest Suitable Airport  . . . . . . . . . . . . . . . . . . . . . . 8.3

Air Systems  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.4
Cabin Altitude Warning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.4

Ditching . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.5
Send Distress Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.5 AdviseCrew and Passengers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.5 Fuel Burn-Off . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.5 Passenger Cabin Preparation  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.5 Ditching Final  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.5 Initiate Evacuation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.6

Electrical  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.6
Approach and Landing on Standby Power  . . . . . . . . . . . . . . . . . . . . 8.6

Engines, APU  . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.6
Engine Failure vs Engine Fire After Takeoff . . . . . . . . . . . . . . . . . . . 8.6 Engine Tailpipe Fire . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.7 Loss of Engine Thrust Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.7 Loss of Thrust on Both Engines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.8 Engine Severe Damage Accompanied by High Vibration . . . . . . . . . 8.9 Recommended Technique for an In-Flight Engine Shutdown . . . . . . 8.9
　
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