Tow Positions, Turns, and Release
Glider Tow Positions
The high tow is normally used for glider tow operations. However, a low-tow position may be used in some instances, a cross-country tow for example. The main goal of both positions is to place the glider in a position that avoids the wake of the tow plane. [Figure 12-13]
Turns on Tow
All turns should be performed in a gentle and gradual manner. The pilot of the glider will attempt to fly the exact flightpath of the tow plane. To do this, the pilot points the nose of the glider at the outside wing tip of the tow plane during a turn.
Turns may be initiated upon reaching a safe altitude. Consideration should be given to obstruction clearance, terrain, and wind gradient. Turbulence and differential wing speed of the glider during turns are potential sources of problems.
Due to the length of the wingspan, the roll rate of a glider is typically slower than that of the tow plane. Consequently, the tow pilot should plan all turns with the understanding that the angle of bank determines the turn radius. Since the bank angles of the tow plane and glider must match to fly the same path, normally a maximum of 15–20° of bank is used.
Approaching a Thermal
When approaching a thermal, be vigilant of other gliders. Since the first glider in the thermal establishes the direction of turn, any glider joining the thermal is required to circle in the same direction as the first glider. This requires the tow pilot to position the flight in a manner that allows the glider proper and safe entry to the thermal. Be super alert when approaching thermals with circling gliders. Expect other gliders to be inbound to the thermal from all directions. Give the thermal traffic a wide berth. If the thermal appears to be especially crowded, steer clear of the activity.
Standard glider release procedures are as follows [Figure 12-14]:
- The pilot of the glider should ensure the tow line is relatively tight, with no excessive slack, prior to release. This allows the tow pilot to feel the release of the glider. If the tow rope is visible in the mirror, look for the wrinkle in the tow rope after the glider has released.
- Once it has been confirmed that the glider has released and is clear, the tow pilot should clear the airspace to the left and start a medium bank, descending left turn.
- The glider should turn right after release but may proceed straight ahead a few moments before turning right. Always be alert for non-standard maneuvering by the glider.
When the tow pilot has positively observed and confirmed the release of the tow line (assumption of release is not acceptable), the pilot of the tow plane may begin a left turn and initiate the descent. In some instances, the glider will release with slack in the tow line. This soft release may not be detectable by the tow pilot. If there is any doubt of the release status in the mind of the tow pilot, the tow pilot should continue the tow and confirm the release via radio or visually.
Descent, Approach and Landing
During the descent, proper engine management is essential. Good engine conservation practices require a gradual power reduction and conservative descent airspeeds. In fact, studies indicate that airspeed may be more critical than power reduction. Therefore, every attempt should be made to avoid airspeed acceleration and power reduction for 3 minutes after glider release. Full flaps or slipping turns can be used to obtain a suitable rate of descent. Closing cowl flaps, if available, further reduces the rate of engine cooling. Realize oil temperature is not as reliable as cylinder head temperature for managing temperature change. Each airplane requires slightly different techniques; however, the goal is to keep the engine as warm as possible while descending at a reasonable rate.
Collision avoidance is always a high priority, since descending flight attitudes increase the potential of a mid-air collision. Consider developing and using specific descent corridors that are void of glider and power traffic.
Approach and Landing
A 200-foot tow line hangs down behind the tow plane at a 30 to 40 degree angle. The altitude of the tow plane must be adjusted to ensure the tow line does not become entangled in obstructions at close proximity to the ground.
Ensure you are thoroughly briefed and familiar with the obstructions around the airport, especially obstructions on the approach end of the runway to be used. Briefings should include a minimum above ground level (AGL) obstruction crossing height and any factors that may influence altitude judgment, such as visual illusions or other airport distractions.
Landing with the tow line attached is not prohibited by regulation; however, the following points should be considered:
- Obstructions are cleared by more than the tow line length (altimeter lag considered).
- The field is well turfed. It is simply inviting early tow line failure from abrasion to land with the tow line on hard ground or paved runways. Landing with the tow line should never be attempted unless the field has clear approaches and is at least 2,500 feet in length.
Other situations require the tow line to be dropped, normally in the glider launch area, during short approach to the runway. If the tow line is to be dropped, the tow pilot must be constantly aware of the launch area situation. The tow line drop area must be defined and ground personnel must be briefed and aware of the drop area. Ground personnel must stay clear of the drop area, and the presence of an individual in the drop area requires an immediate go-around by the pilot of the tow plane without dropping the tow line.