Casualties unknown

1985-12-06: Piper PA-20 (N97MM) — Shageluk, AK

Shageluk, AK, US

On December 6, 1985, a Piper PA-20 (registration N97MM) was involved in an aviation accident near Shageluk, AK. Investigators recorded the probable cause as: The pilot's failure to maintain visual reference due to distraction from manually clearing a frosted windscreen, which resulted in an inadvertent descent below safe altitude and collision with trees. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.

Sourcesthe U.S. National Transportation Safety Board (NTSB) historical archivePrimary reportUpdated 1781061362Data APIEditorial standards

A pilot attempting to land at a lake reduced altitude unintentionally while manually clearing frost from the windshield, resulting in a collision with nearby trees.

What happened

The aircraft was conducting an approach to a lake when it descended and struck trees before reaching the ground. The pilot reported that the windscreen began to frost up during the flight, requiring him to repeatedly wipe the glass clean to maintain visibility. While engaged in this manual clearing process, the pilot lost track of his altitude and approached the landing area lower than intended. The aircraft subsequently impacted a line of trees approximately 60 feet tall.

The investigation

Examination of the incident revealed that the pilot had purchased a windscreen heater but had not yet installed it in the aircraft. This lack of an active heating system likely contributed to the rapid frosting of the windshield, necessitating the manual intervention that distracted the pilot from monitoring his flight path.

Findings

The primary factor in this accident was the pilot's distraction caused by the need to manually clear frost from the windscreen. This task diverted attention away from altitude awareness during a critical phase of flight. The absence of an installed windscreen heater meant that the pilot had to rely on manual methods to maintain visibility, which proved ineffective for maintaining situational awareness.

Safety message

Pilots should ensure all available anti-icing and de-icing systems are functional and installed before flight. Relying on manual methods to clear windows during approach can severely degrade situational awareness and lead to controlled flight into terrain.

Probable cause

The pilot's failure to maintain visual reference due to distraction from manually clearing a frosted windscreen, which resulted in an inadvertent descent below safe altitude and collision with trees.

Investigation report by the U.S. National Transportation Safety Board (NTSB) historical archive. Original record: https://carol.ntsb.gov/event/20001214X38330. This page is a structured re-presentation; facts and quotes are in the National Transportation Safety Board (NTSB), United States.