4. LESSON 20 - LANDING IN STRONG WINDS

Key points of attention:
  • Strong wind is often less strong near the ground: "the wind gradient"
  • Expect turbulence and sudden decreases in windspeed when landing next to or over obstacles (trees, buildings or small hills)
  • Monitor the airspeed regularly and apply a wind additive on the speed
  • Avoid using the airbrakes fully extended in strong wind conditions
  • Do not round-out too high

Landing in strong wind conditions is very different to landing in calm wind conditions. In strong winds, you fly the circuit as usual, but you will have to turn to the diagonal and base-leg earlier. Be ready to turn in time; the strong tailwind on the downwind-leg will make your ground speed much higher and you will pass the reference point much faster. After turning to the base-leg apply a firm drift correction angle. On the final approach you will face a strong headwind, which will result in a lower ground speed. To make sure you make it to the airfield, you need sufficient airspeed. If you are in doubt whether your position on final approach is high enough, resist pulling the stick towards you to trade airspeed for altitude. This will decrease the distance you can travel under these circumstances even more. If in doubt, close the airbrakes and increase your airspeed by lowering the glider’s nose, to optimize your glide path.

Turbulence caused by trees

TURBULENCE
If you fly the final approach over obstacles, buildings, tall trees or bushes on the windward side, you should expect strong turbulence. After wind encounters an obstacle, the direction and strength of the wind can suddenly change. It is therefore important to increase the approach speed and to monitor your speed regularly. Be aware that the airspeed can drop quickly on the lee side of an obstacle.
 
WIND GRADIENT
At an altitude of 300 ft above the ground, the windspeed can be significantly higher than the windspeed on the ground. The windspeed near the ground decreases because the friction, caused by the earth’s surface, slows the wind down. Pilots call this phenomenon “wind gradient.” Wind gradient causes your airspeed to suddenly decrease during the last part of your approach. You can see this happening on your airspeed indicator, which does not display your groundspeed but indicates your speed relative to the incoming air. To compensate for the decrease in airspeed close to the ground, you need to increase your airspeed during final approach. Increase your airspeed with at least half the windspeed, or even more to compensate for wind gusts (if these have been reported).

In strong wind conditions you usually do not fly with the airbrakes fully extended, as this would make the approach very steep and the round-out very difficult.

 
 Wind gradient in km/h
 
Wind gradient in knots
The illustration shows:
1.The wind gradient
2. Airspeed on final approach increased for the strong windspeed
3. Final approach flown with the following errors:
- insufficient airspeed, no wind additive
- airspeed indicator not regularly monitored / no pitch atitude corrections
- too high round-out / hard landing

If you end up in a situation with insufficient airspeed on final approach (3), immediately close the airbrakes and lower your pitch attitude (lower the nose) to gain extra airspeed and avoid a hard landing.