The unassisted takeoff is basically conducted in the same manner as a normal takeoff, but the glider is positioned slightly off the runway heading (runway centerline) by approximately 10–20° with one wing on the ground. If the glider is canted to the right, then the right wing would be resting on the ground. To the left, the left wing would be resting on the ground. When the glider pilot is ready for takeoff, he or she advises the tow pilot either by radio, which is the preferred method, or by signaling the tow pilot with the “ready for takeoff” rudder waggle signal, as in the assisted takeoff. As the towplane accelerates, the wing on the ground (trailing wing) accelerates at a slightly faster rate as it is pulled in a slight arc, allowing that wing to rise quickly with little dragging.
If the glider is aligned with the towplane during the takeoff, the wing that is on the ground has a tendency to be dragged and a ground loop may occur (or severe swerving). After the wings are level, proceed as in the normal takeoff configuration.
Crosswind takeoff procedures are a modification of the normal takeoff procedure. The following are the main differences in crosswind takeoffs:
- The glider tends to weathervane into the wind any time the main wheel is touching the ground. The stronger the crosswind is, the greater the tendency of the glider is to turn into the wind.
- After lift-off, the glider tends to drift downwind off the runway centerline. The stronger the crosswind is, the greater the tendency of the glider is to drift downwind.
Prior to takeoff, the glider pilot should coordinate with the launch crewmember to hold the upwind wing slightly low during the initial takeoff roll. If a crosswind is indicated, full aileron should be held into the wind as the takeoff roll is started. This control position should be maintained while the glider is accelerating and until the ailerons become effective for maneuvering the glider about its longitudinal (roll) axis. With the aileron held into the wind, the takeoff path must be held straight with the rudder. This requires application of downwind rudder pressure, since the glider tends to weathervane into the wind while on the ground. [Figure 7-4] As the glider’s forward speed increases, the crosswind becomes more of a relative headwind; the mechanical application of full aileron into the wind should be reduced. It is when increasing pressure is being felt on the aileron control that the ailerons are becoming more effective. Because the crosswind component effect does not completely dissipate, some aileron pressure must be maintained throughout the takeoff roll to prevent the crosswind from raising the upwind wing. If the upwind wing rises, exposing more wing surface to the crosswind, a skipping action may result, as indicated by a series of small bounces occurring when the glider attempts to fly and then settles back onto the runway. This side skipping imposes side loads on the landing gear. Keeping the upwind wingtip slightly lower than the downwind wingtip prevents the crosswind from getting underneath the upwind wing and lifting it. If the downwind wingtip touches the ground, the resulting friction may cause the glider to yaw in the direction of the dragging wingtip. This yaw could lead to a loss of directional control and runway departure.
While on the runway throughout the takeoff, the glider pilot uses the rudder to maintain directional control and alignment behind the towing aircraft. Yawing back and forth behind the towplane should be avoided, as this affects the ability of the towplane pilot to maintain control. If glider controllability becomes a problem, the glider pilot must release and stop the glider on the remaining runway. Remember, as the glider slows, the crosswind may cause it to weathervane into the wind.
Prior to the towplane becoming airborne, and after the glider lifts off, the glider pilot should turn into the wind and establish a wind correction angle to remain behind the towplane. This is accomplished by using coordinated control inputs to turn the glider. Once the towplane becomes airborne and establishes a wind correction angle, the glider pilot repositions to align behind the towplane.
Just as in the unassisted takeoff with no wind, the unassisted crosswind takeoff is conducted slightly differently with regard to wing positioning and glider alignment. The glider should be placed on the upwind side of the runway or take area; if unable, the towplane should try to angle into the wind as best as possible to reduce the crosswind component for the glider. Most gliders have a crosswind limit up to approximately 10–12 knots. See the Glider Flight Manual/ Pilot’s Operating Handbook (GFM/POH) for information specific to your glider. Again, the unassisted launch should be attempted only by highly experienced pilots.
The glider should be placed with the upwind wing on the ground and the glider angled approximately 20–30° into the wind. [Figure 7-5] If the upwind wing is permitted to be up during the takeoff run, the glider pilot finds it very difficult to level the wings. A ground loop usually results since the downwind wing is being dragged along the ground. With the upwind wing on the ground during the early stages of the takeoff, the glider pilot finds it easier to level the wings early in the takeoff. As in the unassisted takeoff, the upwind wing is swung forward at a faster rate than the downwind wing, aiding the pilot in leveling the wings. The crosswind strikes the fuselage of the glider, tending to push it downwind, making it necessary to place the glider on the upwind side of the runway. Execute a crosswind takeoff from this point after both wings are level.
Common errors in aerotow takeoffs include:
- Improper glider configuration for takeoff,
- Improper initial positioning of flight controls,
- Improper alignment of the glider (unassisted takeoff),
- Improper use of visual launch signals,
- Failure to maintain alignment behind towplane before towplane becomes airborne,
- Improper alignment with the towplane after becoming airborne, and
- Climbing too high after lift-off and causing a towplane upset.