Adverse Weather Operations Windshear Awareness 2

Windshear Recognition:  Timely recognition of a windshear condition is vital for the successful implementation of the windshear recovery/escape procedure.
The following deviations should be considered as indications of a possible windshear condition:

• Indicated airspeed variations in excess of 15 kt.

• Ground speed variations

• Analog wind indication variations: Direction and velocity

• Vertical speed excursions of 500 ft/mn

• Pitch attitude excursions of 5 degrees

• Glide slope deviation of 1 dot

• Heading variations of 10 degrees

• Unusual autothrust activity or throttle levers position.

Predictive and Reactive Windshear Warnings :

An optional WINDSHEAR warning is available on most aircraft models. The windshear warning is based on the assessment of current aircraft performance (flight parameters and accelerations). The windshear warning is generated whenever the energy level of the aircraft falls below a predetermined threshold.

The windshear warning system associated to the Speed Reference System (SRS) mode of the flight guidance constitute the Reactive Windshear Systems (RWS), since both components react instantaneously to the current variations of aircraft parameters.

To complement the reactive windshear system and provide an early warning of potential windshear activity, some weather radars feature the capability to detect windshear areas ahead of the aircraft. This equipment is referred to as a Predictive Windshear System (PWS). PWS provides typically a one-minute advance warning. RWS and PWS characteristics

PWS generates three levels of windshear alert, depending on and increasing flight crew awareness by :

• The distance and angular position between the aircraft and the windshear

• The altitude of the aircraft

• The flight phase.
Colored patterns and icons are displayed on the weather radar display (ND) to indicate areas of windshear activity.

HOW IS PWS & RWS INCREASING PILOT AWARENESS ? 

• Unexpected air mass variation via FPV and approach speed variation .
• a significant loss of energy via SPEED ,SPEED ,SPEED and WINDSHEAR aural warning system .
• escape maneuver through ALPHA FLOOR , SRS SYSTEM , AOA PROTECTION and GS MINI.

FPV OR THE BIRD :

FPV associated with GS mini protection is an effective means for informing the flight crew about the wind shifting by Approach speed variation and lateral displacement reflected on the FPV horizontally , vertical flight path FPV reflect the vertical air mass movement . 

LOW ENRGY WARNING SYSTEM : 

The low energy warning system ( speed , speed , speed ) is based on aircraft acceleration and flight path angle . in windshear phenomena the first warning to appear is the low energy warning in case of rapid deceleration which required rapid thrust adjustment before alpha floor activation and reactive windshear RWS triggers WINDSHEAR aural warning.

• IF deceleration rate is (-1KTS and the FPV -3  the Warning will be trigger at VLS-7 KTS) .
• IF deceleration rate is (-1KTS and the FPV -4 the warning will be trigger at VLS -1 KTS.)  

ALPHA FLOOR, SRS AND AOA :

-When the Alpha floor is triggered the A/TH triggers TOGA which changes to TOGA LK when the aircraft AOA has been decreased ,to DESELECT the TOGA LK by turning the A/TH to off.

-SRS mode ensures the best aircraft climb angle with a possibility of full back stick to minimize altitude loss . 

-The AOA protection enables the pilot to pull to the maximum aft stick if required in order to follow the SRS , this will provide maximum lift and minimum drag by automatically retracting the speed brakes if extended . 

. 

`