Standard aerotow release procedures provide safety benefits for both the glider and the towing aircraft. When the aerotow reaches release position, the glider pilot should clear the area for other aircraft in all directions, especially to the right. Prior to release, the towline should be under normal tension for a normal release. Depending on the hook, some tension is required to extract the ring from the hook. The hook-type towing attachments may need pressure to make the hook swing open to release the hook. When ready to release, the glider pilot pulls the release handle completely out to ensure the towline hook is fully open to allow the release of the towline and hold the hook release open until it is verified that the towline is free of the glider. Generally, the release of the towline is felt as the forward motion begins to decelerate, but the glider pilot should always visually confirm the towline release prior to the 90° right clearing turn. [Figure 7-10A] Next, the glider pilot banks to the right, accomplishing 90° of heading change, then in level flight flies away from the release point while observing the towplane actions.
Shown in Figure 7-10B, this 90° change of heading achieves maximum separation between towplane and glider in minimum time. After confirming glider release and 90° turn away from the towplane, the tow pilot turns left away from the release point, achieving safe maximum separation.
Shown in Figure 7-10C, once clear of the glider and other aircraft, the tow pilot then begins a descent. The tow pilot should continue to observe the glider’s actions as the glider pilot may have started his/hers thermalling procedure with the possibility of the glider pilot losing sight of the towing aircraft. Common errors in aerotow release include:
- Lack of normal tension on towline or slack in towline.
- Failure to clear the area prior to release.
- Failure to make a 90° right turn after release.
- Release in close proximity of other aircraft.
- Glider pilot and tow pilot losing sight of each other’s aircraft.
Maintaining proper release procedures is important to ensure proper aircraft separation in case pilots lose sight of each other’s aircraft. It is imperative for the tow pilot to exit the immediate area of the glider release. If the glider releases in a thermal or other lift, the glider must stay in that lift to gain altitude, whereas the tow pilot has the ability to completely clear the glider’s area before returning to the airport. Both the tow pilot and glider pilot should be aware of other gliders near areas of lift.
Slack line is a reduction of tension in the towline. If the slack is severe enough, it might entangle the glider or cause damage to the glider or towplane. The following situations may result in a slack line:
- Abrupt power reduction by the towplane
- Aerotow descents
- Glider turns inside the towplane turn radius [Figure 7-8]
- Updrafts and downdrafts
- Abrupt recovery from a wake box corner position [Figure 7-11]
When the towplane precedes the glider into an updraft, the glider pilot first perceives that the towplane is climbing much faster and higher than it actually is. Then, as the glider enters the updraft, it is lighter and more efficient than the towplane. It climbs higher and faster than the towplane did in the same updraft. As a result, the glider pilot pitches the glider over to regain the proper tow altitude but gains airspeed more quickly than the towplane, hence the slack towline. The glider pilot must be ready to control the descent and closure rate to the towplane.
Slack line recovery procedures should be initiated as soon as the glider pilot becomes aware of the situation. The glider pilot should try slipping back into alignment with the towplane. In the event that slipping fails to reduce the slack sufficiently, careful use of spoilers/dive brakes can decelerate the glider and take up the slack. When the towline tightens, stabilize the tow and gradually resume the desired aerotow position. When slack in the towline is excessive, or beyond the pilot’s capability to safely recover, the glider pilot should immediately release from the aerotow.
Common errors regarding a slack line include:
- Failure to take corrective action at the first indication of a slack line.
- Use of improper procedure to correct slack line causing excessive stress on the towline, towplane, and the glider.