WINDSHEAR Flashcards
Define Windshear?
Sudden change of airs direction, speed or both in combination.
How do you detect in Windshear without sophisticated instruments?
- Indicated airspeed variations in excess of 15 kt
- 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
What is “Predictive Windshear”?
The predictive windshear system uses the weather radar to detect where there is a doppler shift in the precipitation ahead of the airplane. If there is a
shift measured, it warns the pilots.
Is sometimes refered to as GPWS mode 7
What is Doppler shift?
Doppler shifts happen when due to the velocity of an object, the return signals change frequency. When the object moves away, the frequency of the signal is lower. When the object moves towards you, the frequency of the signal is higher.
The famous example of this effect is when an ambulance moves past you. The sound is high pitched (higher frequency) when it moves towards you and it changes to a low pitch (lower frequency) when it passed you and moves away. This is not only valid for sound but also for electromagnetic radiation, which is used by the weather radar.
Within what ranges does Predictive Wind Shear usually work?
Within 5 nm up to 1’500 ft
Procedures when encounting Wind Shear?
You will call out “WINDSHEAR TOGA”, advance thrust levers to TOGA and follow SRS orders, preferably
wings level, without changing configuration until out of the WS. With AP ON, you can keep it on, but keep in mind it will disconnect if you reach angle of attack protection and alpha floor activates. You may need full aft sidestick.
If you supect WS use a lower flap setting of runway will allow. If you hit WS you have less drag and also your 20 kts margin over Vref can be higher, so you carry more speed and less drag
What does “SRS” do at a go-around on the Airbus and how is it engaged?
Move thrust levers to TOGA and SRS will arm if a FD is on and flaps are NOT selected UP. SRS will give you the speed at engagement or minimum Vapp
What conditions may cause windshear?
Windshear conditions usually are associated with the following weather situations: • Jet streams • Mountain waves • Frontal surfaces • Thunderstorms and convective clouds • Microbursts.
What speeds can be reached in the downdraughts and that horizontal airflow?
6’000 ft/min vertically
Up to 45 kts horizontally
What is LLWAS?
Low Level Windshear Alert System consists of a central wind sensor (sensing wind velocity and direction) and peripheral wind sensors. It enables controllers to warn pilots of existing or impending windshear conditions. An alert is generated whenever a difference in excess of 15 kt is detected. LLWAS may not detect downbursts with a diameter of 2 nm or less.
What is Terminal Doppler Weather Radar (TDWR).
Terminal Doppler Weather Radar (TDWR) enables to detect approaching windshear areas and, thus, to provide pilots with more advance warning of windshear hazard
Difference between “Reactive” and “Predictive” windshear warnings?
Reactive:
Detects in the windshear and gives guidance to escape
Works by comparing Inertial data and aerodynamic data
Predictive:
Detects ahead and give guidance to avoid the WS
Uses doppler weather radar
