跟着AI学ICAO:wind shear

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Question 1: What is wind shear?

Wind shear is a sudden and rapid change in wind speed and (or) wind direction.

Question 2: What kind of weather phenomena may wind shear be associated with?

Low level wind shear is usually associated with the following weather phenomena:

- frontal surfaces,

- jet streams,

- thunderstorms,

- mountain waves,

- microbursts.

Question 3: What are the main effects of wind shear?

The main effects of wind shear are：

- Turbulence；

- Violent air movement (updraft or down-drafts or swirling or rotating air patterns)；

- Sudden increase or reduction of airspeed；

- Sudden increase or decrease of groundspeed and or drift.

Question 4: What are the indications of suspected wind shear conditions?

There are some indications of a suspected wind shear condition:

•        Indicated airspeed variations in excess of 15 knots；

•        Groundspeed variations (decreasing head wind or increasing tail wind, or a shift from head wind to tail wind)；

•        Vertical-speed excursions of 500 feet per minute or more；

•        Pitch attitude excursions of five degrees or more；

•        Glideslope deviation of one dot or more；

•        Heading variations of 10 degrees or more and,

•        Unusual autothrottle activity or throttle lever position.

Question 5: If wind shear conditions are expected during takeoff, what should the flight crew do?

If wind shear conditions are expected during takeoff,

Firstly, the flight crew should select the most favorable runway for departure;

Secondly, the flight crew should select the minimum flaps configuration compatible with takeoff requirements;

Thirdly, the flight crew should use weather radar or the predictive wind shear system before beginning the takeoff to ensure the flight path is clear of hazards;

Fourthly, the flight crew should select maximum takeoff thrust;

Fifthly, after selecting the takeoff-go around (TOGA) mode, the flight crew should select the flight path vector display for the monitoring pilot, to obtain a visual reference of the climb flight path angle;

Sixthly, the flight crew should closely monitor the airspeed and airspeed trend during takeoff roll to detect any evidence of impending wind shear.

Question 6: If wind shear is encountered during takeoff roll, what actions should the flight crew take without delay?

If wind shear is encountered during takeoff roll,

before V1,

the flight crew should reject takeoff if unacceptable airspeed variations occur or if there is sufficient runway remaining to stop the aircraft;

After V1,

the flight crew should disconnect the autothrottle, if available, and maintain or set the throttle levels to maximum takeoff thrust; rotate normally at Vr and follow the flight director pitch command if the flight director provides wind shear recovery guidance or set the required pitch attitude.

Question 7: If wind shear is encountered during initial climb, what actions should the flight crew take without delay?

If wind shear is encountered during initial climb,

Firstly, the flight crew should disconnect the autothrottle, if available, and maintain or set the throttle levels to maximum takeoff thrust;

Secondly, If the autopilot (AP) is engaged and if the FD provides wind shear recovery guidance, the flight crew should keep the AP engaged; or,

•        Follow the FD pitch command, if the FD provides wind shear recovery guidance; or,

•        Set the required pitch attitude;

Thirdly, the flight crew should closely monitor the airspeed, airspeed trend and flight-path angle ;

Fourthly,  the flight crew should allow airspeed to decrease to stick shaker onset (intermittent stick shaker activation) while monitoring the airspeed trend;

Fifthly,  the flight crew should not change the flaps or landing-gear configurations until out of the wind shear condition; and,

6) When out of the wind shear condition, increase airspeed when a positive climb is confirmed, retract the landing gear, flaps and slats, then establish a normal climb profile."

Question 8: If wind shear is encountered during approach or landing, what actions should the flight crew take without delay?

"If wind shear is encountered during the approach or landing, the following recovery actions should be taken without delay:

•        Select the takeoff go-around (Take-off Go-around (TOGA) Mode) mode and set and maintain maximum go-around thrust

•        Follow the Flight Director pitch command (if the FD provides wind shear recovery guidance) or set the pitch-attitude target recommended in the A O M or QRH

•        If the AP is engaged and if the FD provides wind shear recovery guidance, keep the AP engaged; otherwise, disconnect the AP and set and maintain the recommended pitch attitude

•        Do not change the flap configuration or landing-gear configuration until out of the wind shear

•        Level the wings to maximize climb gradient, unless a turn is required for obstacle clearance

•        Allow airspeed to decrease to stick-shaker onset (intermittent stick-shaker activation) while monitoring airspeed trend

•        Closely monitor airspeed, airspeed trend and flight path angle (if flight-path vector is available and displayed for the PNF) and,

•        When out of the wind shear, retract the landing gear, flaps and slats, then increase the airspeed when a positive climb is confirmed and establish a normal climb profile.