4. LESSON 22 – SLIPPING AND SKIDDING
Key point:
- Watch the yaw string to use the rudder properly
- Deliberate side slip can be used to increase the rate of descent
The first part of this chapter deals with unwanted slipping or skidding, the second part deals with deliberate side-slipping.
UNWANTED SLIPPING OR SKIDDING
If your glider is not aligned properly with the airflow, its flight may be inefficient. This is most likely the case in a less than perfect turn, but it can also occur during straight flight.
Unwanted slipping or skidding is generally caused by too little or too much rudder deflection in a turn or by the aileron being used without proper rudder input to compensate for the secondary control effect. A yaw string deflected away from central will show you, pointing at the foot you need to press, how to correct. Cautions:
- Do not let the yaw string distract you from lookout. Your instructor will show you how to combine the two tasks.
- A change in rudder pressure can change your bank angle. You will need to use aileron as normal to maintain the angle of bank you require.
- Gentle pressure needed on the left pedal (or less pressure on the right pedal)
- Gentle pressure needed on the right rudder pedal (or less pressure on the left pedal)
DELIBERATE SIDE-SLIPPING
The airbrakes are very effective for increasing the rate of descent during an approach. But if you need to lose altitude quickly you can also combine the airbrakes with a side-slip. When a side-slip is performed intentionally and correctly, there is no turning motion because the nose is now pointing opposite to the bank angle.
Nowadays, a side-slip approach is considered an advanced gliding technique. In the early days of aviation, gliders were not equipped with proper airbrakes and side-slipping was the only way to lose height on final approach. During approach the heading is opposite to the bank angle, while you maintain the original track.
To enter a side-slip:
- Pick an easy way to tell which way you are tracking; either the approach itself (if that is where you are using the side-slip) or a landmark on the horizon elsewhere. Long and straight roads, railways or runways are perfect.
- Use aileron to lower one wing slightly, and simultaneously apply enough opposite rudder to stop the glider turning and maintain your desired ground track. If you’re sideslipping to your approach to a landing with a crosswind component, lower the inter-wind wing.
- Use the elevator to control the pitch attitude. Be aware of the fact that the airspeed indicator may not be reliable when side-slipping, sometimes the indicated airspeed will even drop to zero!
To recover from a side-slip:
-
Simultaneously release the rudder pressure and level the wings.
-
Adjust the pitch attitude to adjust the speed.
