PHOEBUS N112AJ accident near Alvord Desert, Oregon

Probable cause

Pilot’s failure to properly respond to a slack towline during takeoff, which resulted in a loss of control of the glider.

NTSB analysis

The glider pilot took off utilizing the auto launch (vehicle-tow) method. Photos taken by a witness revealed that the glider overran the towline, which resulted in a slack towline. The glider then pitched up and, after reaching about 100-150 ft above ground level, rolled to the left and impacted terrain in a near vertical attitude. The tow vehicle driver stated that the truck had not yet accelerated to 60-65 mph needed for the release of the tow cable from inside the cockpit; instead, the truck had only accelerated to 55 mph before the spotter told the driver to stop as the glider impacted the terrain.

A slack towline can be caused by a change in speed of either the glider or tow vehicle. If not corrected, a slack towline can result in the loss of control in flight. Also, a change in wind gradient can have a noticeable effect on a glider’s speed during ground launches. When a slack towline is encountered, a pilot should communicate with the tow vehicle to change speed, adjust pitch to control airspeed, or release the tow rope and land straight ahead.

The investigation could not determine why the slack towline occurred. Nevertheless, the pilot did not follow recommended procedures for responding to a slack towline and subsequently lost control of the glider.

Text from the NTSB. Open the NTSB docket for WPR19LA191 for the full record.