Maule M-6-235 N56517 accident near Tyonek, Alaska

Probable cause

The pilot’s selection of unsuitable terrain for landing, which resulted in the airplane encountering deep snow and coming to rest inverted.

NTSB analysis

The pilot initially reported that before landing on a snow-covered glacier, he intended to fly a low pass over the snow-covered site and briefly touchdown to determine the condition of the snowpack, a maneuver commonly known as dragging the landing site. He said that during a second downhill pass over the site, he inadvertently allowed the tailwheel-ski equipped airplane to slow while attempting to “set the track more fully”. He added that, he mis-judged the snow depth and allowed the airplane to slow too much. Subsequently, the ski tips dug into the snow and the airplane came to rest inverted.

The airplane sustained substantial damage to the fuselage, the wings, and the empennage.

The pilot initially reported there were no preimpact mechanical failures or malfunctions with the airframe and engine that would have precluded normal operation. The pilot later reported that he believed the brake calipers had obstructed the movement of the skis. Two witness marks were observed on the skis that indicated the brake calipers had impacted the skis.

A Federal Aviation Administration (FAA) aviation safety inspector (airworthiness) examined the airplane and stated that there were no preimpact mechanical failures or malfunctions found with the airplane.

Based on the available evidence, it is likely that the damage to the skis from the brake calipers were from impact damage.

Text from the NTSB. Open the NTSB docket for ANC21LA017 for the full record.