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Casualties unknown

Flap Locking Pin Dislodgement During Flight (N1793J)

Bethel, AK, US

On July 18, 1998, a Piper PA-28-140 (registration N1793J) was involved in an aviation accident near Bethel, AK. Investigators recorded the probable cause as: The fracture of the flap handle position locking pin, which resulted in an uncommanded raising of the flaps during takeoff. A factor was the pilot's decision to takeoff with a suspected problem in the flap system. 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 2026-07-04Data APIEditorial standards

A pilot experienced flap binding during landing and later took off. During climb, the flaps retracted abruptly, and the airplane struck trees. Investigators found a flap locking pin had fallen from its hole.

Incident Overview

A pilot encountered binding in the flaps while landing. After inspecting the aircraft and finding no apparent problem, he decided to proceed with the return flight. During the initial climb, the manually operated flaps retracted suddenly. The pilot was unable to maintain the flaps in the extended position to sustain a climb, and the airplane subsequently contacted trees located in the departure path.

Investigation Findings

Examination after the event revealed that the flap position locking pin, part number 480-715 (59-040-187-1500), had fallen from its designated hole. The retaining roll pin, however, remained in place. According to the investigation, the only way to remove the locking pin from the hole is to first remove the retaining pin or fracture the locking pin into two pieces. The missing locking pin was not recovered, but a photograph taken during the investigation shows a similarly dimensioned pin lying below the flap handle assembly.

Frequently asked questions

What happened in the 18 Jul 1998 Piper PA-28-140 accident near Bethel, AK?

A pilot experienced flap binding during landing and later took off. During climb, the flaps retracted abruptly, and the airplane struck trees. Investigators found a flap locking pin had fallen from its hole.

What aircraft was involved and where did it happen?

The accident on 18 Jul 1998 involved a Piper PA-28-140, registration N1793J, at Bethel, AK.

What was the probable cause of the accident?

The fracture of the flap handle position locking pin, which resulted in an uncommanded raising of the flaps during takeoff. A factor was the pilot's decision to takeoff with a suspected problem in the flap system.

More accident analyses

Investigation report by the U.S. National Transportation Safety Board (NTSB) historical archive. Original record: https://carol.ntsb.gov/event/20001211X10454. This page is a structured re-presentation; facts and quotes are in the National Transportation Safety Board (NTSB), United States.