4. LESSON 14 - WINCH LAUNCHING

Key points:
 
  • Call for the cable only when fully ready and keep hold of therelease
  • Release immediately if you cannot keep the wings level 
  • Control the rate of pitch into the full climb

This impressive launch method requires full concentration from both the pilot and the winch driver throughout the launch. Here your responses have to be rehearsed and decisive. The trajectory of the launch follows the same pattern every time. At first, the pilot ensures that the climb angle is shallow until there is sufficient speed to transition safely into the full climb angle (about 45°). The trajectory is flown this way so that in any eventuality you are able to deal with a launch failure without hazard or hesitation. Due to the high pitch attitude it is hard to see the horizon by looking straight over the nose. The best way to judge your climb angle and position is by looking left or right.

Let’s now look at winching from the start.

CONNECTING THE CABLE

Only when you are happy to launch should you ask for the cable: this is when you announce that you are ready for departure. By accepting it the launch process will be started as soon as the cable connection is complete and the wings are held level.

You should be satisfied that the correct hook is being used; be aware that some gliders have aerotow and winch hooks close together. It is imperative that the correct hook is used as they are not interchangeable and can seriously affect the aircraft’s ability to launch safely. Likewise make sure that the correct weak link is used.

With the launch process started and the wings now level, you should ensure your entire focus is on flying the launch safely. If there is any issue or distraction before the glider starts moving, immediately reject the launch by releasing the cable. Your left hand must hold the cable release from the point the cable is connected until well into the launch.

INITIAL ACCELERATION (1)

You need to fly the glider during the initial acceleration, with several things to do, simultaneously:

  • Lift tail or nose (depending on type of glider) to balance on the mainwheel.
  • Keep the wings level. Initially this may need large deflections of theailerons (moving the control stick left or right).
  • Normally, no rudder input is needed (see the later lesson for crosswinds)

As soon as you have some airspeed, the size of those control deflections can return to normal.
Allow the glider to lift off when it is ready. Never pull the glider off the ground, even if the ground roll appears to be taking longer or you are operating on rough ground. Only when the glider has enough airspeed will it lift off from the ground automatically. Most composite and modern two-seater gliders take off with the stick in the neutral position.
If you cannot keep the wings level, release immediately! This is extremely important. If you wait and the wing tip touches the ground, it could make the glider cartwheel catastrophically before you have time to release. So do not hesitate if you cannot keep them level!

INITIAL CLIMB (2)

Once the airspeed is sufficient, you can gradually increase the climb angle.

Do not attempt any rapid pitch up to the full climb attitude.

Normally, it should take about 5 seconds to get to the climb attitude; many pilots find counting helpful. Caution though: this is a guide and may need adjusting, perhaps for an under-powered winch.
Some gliders have the tendency to automatically ‘over-rotate’ into a steep climb just after lift-off, especially if the winch driver accelerates the cable too quickly. If this happens, push the stick forward immediately. You can also prevent over-rotating by keeping some slight forward pressure on the stick, helped by setting the trim slightly forward of neutral before the launch.

The dangers of climbing too steep at low altitudes are serious. If you exceed the critical angle of attack, the airflow will separate from the wing, the lift will decrease and the drag will increase and you could enter a stall. That is why you slowly increase the climb angle during a winch launch with adequate speed and continued acceleration. If you fly the launch safely, you should always be able to recover from a launch failure regardless of the height or circumstances.

FULL CLIMB (3)

Providing that the speed is correct, the attitude is steeper in the full climb. As you get higher you will need to continue to apply increasing amounts of back-pressure to maintain the climb.

THE PILOT IS RESPONSIBLE FOR A SAFE LAUNCH

While it is the winch driver who has their hand on the throttle, the glider pilot remains responsible for the safety of the launch. Not all winches are fitted with devices for displaying the glider’s airspeed so the driver may need to estimate. You will be taught the procedures and learn the skills for getting things right.

TOO SLOW?

During a winch launch you need more lift than in normal flight. The wings have to support the weight of the glider plus the increased load caused by the force on and the weight of the cable. In other words, the load of the glider is higher during a winch launch. It is not possible for the glider to be overloaded as long as the maximum winch speed is observed and the correct weak link is used. Monitor your airspeed frequently.

If the airspeed becomes too low, reduce the angle of climb. If the winch driver increases power, you may be able to gradually increase your climb angle again. If the airspeed continues to reduce towards the minimum briefed safe launch speed, reduce the angle of climb further to maintain airspeed above the minimum. If you are not climbing, or the speed reaches the minimum, the launch has failed and you should treat it as a launch failure.

TOO FAST?

Extra speed during the first half of the launch will not cause any issues for the glider, but if the speed is far too much in excess, release the cable, even if under tension, and treat as a launch failure. During the second half, however, where the stresses on the glider increase, you can signal the winch driver to slow down by making the glider yaw left-right in a clear signal using the rudder pedals. The signal needs to look deliberate and will need some opposite ailerons to prevent the glider from rolling. Avoid increasing the back-pressure too much because the weak link may break. If there is no response from the winch after signalling, and the glider is still too fast, release the cable and treat it as a launch failure. The time for signalling will have passed.

RELEASING (4)

At the final stage of the winch launch your climb rate decreases and the climb angle becomes shallower. Even though you are still pulling the stick towards you, the pitch attitude becomes lower and you may see the speed reduce as the winch driver reduces or cuts the power. Lower the nose and release the cable by pulling the release knob. Should you not release in time, then the cable will pull backwards and the automatic release mechanism will be activated. Now adopt a normal pitch attitude to fly at your desired airspeed and configure the glider as necessary.