Mount Vernon, WA, USA
N6582P
CESSNA P210N
The commercial pilot configured the airplane for a straight-in approach when it was about 8 nautical miles from the destination airport. He verified that both main landing gear were down and locked by seeing that the landing gear indicator light had illuminated and by looking in a mirror mounted on the right wing and seeing that the gear were down. After a normal touchdown and during the landing roll, the airplane began to veer right, which the pilot believed was likely due to a flat tire. He then shut down the engine and steered the airplane to a grassy area adjacent to the runway. Postaccident examination of the airplane revealed that the right main landing gear (MLG) had collapsed and that the right aileron and right elevator had sustained substantial damage. Postaccident examination of the landing gear system revealed that the right MLG's down-lock hook exceeded the airplane manufacturer's maximum tolerance and that it was not over center, which is required for the landing gear to remain in the locked position. Based on the evidence, it is likely that the out-of-tolerance down-lock hook prevented the right MLG from locking after the pilot deployed the landing gear and resulted in the right MLG collapsing during the landing roll. The airplane service manual states that the proper rigging of the MLG down-lock mechanism should be verified every 200 hours. A review of the maintenance logbooks revealed no entries related to the rigging, which is not always documented in the maintenance logbook following each service. Therefore, it could not be determined whether a maintenance event led to the out-of tolerance right MLG down-hook or if it became out of tolerance over time.
On October 28, 2017, about 1250 Pacific daylight time, a Cessna P210N airplane, N6582P, was substantially damaged following a collapse of its right main landing gear at Skagit Regional Airport (BVS), Burlington, Washington. The commercial pilot and two passengers were not injured. The airplane was registered to Insurance Solutions, Inc. and operated by the pilot under the provision of Title 14 Code of Federal Regulations Part 91 as a personal flight. Visual meteorological conditions prevailed and no flight plan was filed for the flight, which departed Snohomish County Airport (PAE), Everett, Washington at 1150. According to the pilot, after an uneventful flight, he began a descent for a straight in approach to land on runway 29 and deployed the landing gear about 8 nautical miles from the airport. He verified that the landing gear down indicator light had illuminated and then observed the landing gear in the down position through a mirror mounted to the radar on the right wing. The pilot subsequently checked the gear position again when the airplane was about 4 nm from the airport and then configured the airplane for a normal landing with 10° of wing flaps. Moments before the airplane touched down, the pilot deployed 30° of wing flaps. The airplane touched down normally and transitioned into a landing roll; however, the right main landing gear collapsed, which the pilot perceived as a loss of tire pressure to the right main landing gear wheel. He subsequently retarded the mixture control to the full lean position and shut off the engine while he steered the airplane until it came to rest in a grass area to the right of the runway. Photographs of the accident airplane furnished by the Federal Aviation Administration inspectors showed substantial damage to the right aileron and right elevator. The 6 seat, high-wing, retractable gear airplane was manufactured in 1978 and had been registered to the accident pilot since August 8, 2016. At the time of the accident, the airplane had accumulated a total of 3 flight hours since the airplane's most recent annual inspection, which was completed on October 9, 2017 at a recorded airframe total time of 4,342 flight hours. The logbook entry showed that the right main landing gear saddle screws were tightened, but did not indicate that a landing gear swing was accomplished. The pilot did not recall experiencing any landing gear problems before the accident flight nor had the previous owner, who owned the airplane from 1999 to 2016, disclose any landing gear anomalies to him at the time of purchase. The airplane's main landing gear system was hydraulically powered with electrical circuits to control and indicate landing gear position. During normal operation, gear selection is accomplished by moving a gear selector handle located in the switch panel. Once the landing gear position is selected, hydraulic fluid is supplied to the main landing gear actuators by an electrically-powered power pack assembly, which then drives the main landing gear into the desired position. A representative of the airframe manufacturer reported that the landing gear deployment system uses a down lock hook that locks the landing gear in the deployed position, but added that the hook needs to be over center to remain locked. The over center must be rigged periodically, which can be accomplished with a special down lock tool, as the hook can wear out over numerous cycles or when the system is not rigged properly. However, this cannot be completed if the down lock hook is out of tolerance. According to an excerpt from the airplane service manual, proper rigging of the downlock should be verified every 200 flight hours. The airframe and powerplant mechanic that recovered the airplane reported that he was unable to force the right main landing gear to free fall after the accident from its retracted position. A subsequent examination of the landing gear system was performed by the same mechanic with oversight from a representative of the Federal Aviation Administration. The examination team removed the fuselage floor panels and completed two full landing gear retractions and extensions, but were unable to replicate the landing gear failure. During both extensions, the landing gear downlock tube seated within the saddle as designed and the landing gear instrument panel indicator showed the landing gear in the down and locked position. The right main landing gear down lock hook appeared worn when compared to the left main landing gear hook. The right landing gear up lock rigging was tested at a later date and indicated that the down lock hook over center exceeded the prescribed maximum tolerance when compared to the left main landing gear using a tool specifically designed to verify the over center position of the down lock hook.
The failure of the right main landing gear (MLG) down-lock mechanism due to an out-of-tolerance down-lock hook, which resulted in the collapse of the right MLG during the landing roll.
Source: NTSB Aviation Accident Database
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