Aviation Accident Summaries

Aviation Accident Summary ANC03LA126

Skwentna, AK, USA

Aircraft #1

N9006A

Cessna 170A

Analysis

The commercial certificated pilot was landing on a remote gravel area that was about 1,000 feet long, and 30 feet wide. The pilot said that during the landing roll, the airplane's right main landing gear suddenly collapsed. As the airplane slid on the gravel, the right gear strut was torn out of the fuselage, and the airplane received additional damage to the fuselage and right wing. After the accident, the pilot said he examined the right gear strut and discovered the right axle and wheel assembly were missing from the outboard end of the gear strut. After a search, the pilot located the wheel assembly and discovered that the nuts utilized to secure the attaching axle bolts to the gear strut, were stripped from their respective bolts. The pilot said he decided to wait until the next day before activating his airplane's emergency locator transmitter. He further said he decided to destroy his airplane by setting it on fire, as it would have been economically unfeasible to pay for repairs and helicopter transportation charges to remove the airplane from its remote location. The airplane was observed by search personnel as having burned.

Factual Information

On September 25, 2003, about 1400 Alaska daylight time, a tundra tire-equipped Cessna 170A airplane, N9006A, sustained substantial damage when the right main landing gear strut collapsed during the landing roll at a remote area, about 57 miles west-southwest of Skwentna, Alaska. The airplane was being operated as a visual flight rules (VFR) local area personal flight under Title 14, CFR Part 91, when the accident occurred. The airplane was operated by the pilot. The commercial certificated pilot, the sole occupant, was not injured. Visual meteorological conditions prevailed. No flight plan was filed, nor was one required. During a telephone conversation with the National Transportation Safety Board (NTSB) investigator-in-charge (IIC), on September 30, the pilot reported that he landed toward the east on a gravel site in an area known as Hellsgate. The landing area was oriented east/west, and was about 1,000 feet long, and 30 feet wide. The pilot said that during the landing roll, the airplane's right main landing gear suddenly collapsed. As the airplane slid on the gravel, the right gear strut was torn out of the fuselage, and the airplane received additional damage to the fuselage and right wing. After the accident, the pilot said he examined the right gear strut, and discovered the right axle and wheel assembly were missing from the outboard end of the gear strut. After a search, the pilot located the wheel assembly and discovered that the nuts utilized to secure the attaching axle bolts to the gear strut, were stripped from their respective bolts. The pilot said he decided to wait until the next day, September 26, before activating his airplane's emergency locator transmitter. He further said he decided to destroy his airplane by setting it on fire, as it would have been economically unfeasible to pay for repairs and helicopter transportation charges to remove the airplane from its remote location. Search personnel located the accident site on September 26, and alerted a friend of the pilot's, who picked up the pilot on September 27. According to search personnel, the accident site was located along the South Fork of the Kuskokwim River, at Ptarmigan Pass, in the Alaska Mountain Range. The airplane was observed by search personnel as having burned.

Probable Cause and Findings

An overload failure of the axle retaining nut/bolt assembly, which resulted in the separation of the axle/wheel assembly, and subsequent collapse of the right main landing gear strut during the landing roll.

 

Source: NTSB Aviation Accident Database

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