Dg-Flugzeugbau Gmbh DG-500MB N505JL accident near Richland, Washington

Probable cause

The failure of the spoilers to retract because the right wing spoiler’s lower plate became jammed, which resulted in the glider not having enough lift to make it to the runway surface.

NTSB analysis

In a written statement, the pilot reported that the accident flight was his second flight of the day. After conducting a series of practice maneuvers, he was returning to the airport. The pilot entered a right traffic pattern and configured the glider for landing. With the landing gear extended and the flaps set at 10 degrees, he opened and tested the spoilers. While on the base leg of the traffic pattern, he noticed that the glider was low, and, as he maneuvered onto final approach, he closed the spoilers (forward activation of the lever). The glider’s sink rate was excessive and he observed that the spoilers visually appeared to be deployed although the control lever was in the full-forward (closed) position. He manipulated the lever back and forth, which had no effect on the spoiler position. The glider impacted railroad tracks about 1,000 feet from the approach end of the runway and sustained substantial damage to the fuselage and wings in the accident sequence.

A postaccident examination of the glider revealed that the right wing spoiler’s lower plate appeared to have been rubbing the aft spoiler bay wall until it scraped off the resin. It appeared to have scraped enough material off that it caught on a fabric seam (once sealed in the resin) and would not retract. In other words, the spoiler’s lower plate would not push past the catch due to the exposed fabric edge. The location of the scrape marks and the fabric seam put the spoilers at half extension, which is consistent with the lack of performance the pilot reported. The left wing spoiler’s lower plate bushings were tight, with no play.

Text from the NTSB. Open the NTSB docket for WPR12CA288 for the full record.