PENSACOLA, FL, USA
N781SL
Cessna 421B
After takeoff the landing gear would not retract and the landing gear warning horn sounded. The pilot continued to the destination airport and when weather prevented a landing, he returned to the departure airport. After landing the aircraft swerved to the left and the left main gear tire could be heard squealing. The aircraft went off the side of the runway and the left main gear collapsed and separated. Post crash examination of the aircraft showed the washer, which retains the bolt in the left main gear scissors, had failed and the scissors had separated. This allowed the gear to turn and prevented the gear from retracting due to the ground switch on the scissors not being able to open during takeoff. The failed washer was the subject of Cessna Aircraft Company, Service Information Letter ME83-37, dated November 23, 1983. This letter called for replacement of this washer with a thicker washer at the next routine 100-hour inspection.
On December 13, 2000, about 2227 central standard time, a Cessna 421B, N781SL, registered to Silver Lining Leasing, Inc., and operated by Lifeguard Air Ambulance, Inc., as a Title 14 CFR Part 135 air medical transport flight, from Pensacola, Florida, to Valparaiso, Florida, ran off the side of the runway during landing, while returning to Pensacola Regional Airport. Instrument meteorological conditions prevailed at the time and an instrument flight rules flight plan was filed. The aircraft received substantial damage and the airline transport-rated pilot, second pilot, and two flight nurses were not injured. The flight originated from Pensacola Regional Airport, about 2130. The pilot stated that the landing gear would not retract after takeoff from Pensacola Regional Airport, en route to Valparaiso. He continued to Valparaiso, and after flying a localizer approach, they were unable to see the runway. He then elected to return to Pensacola. During landing, the aircraft swerved to the left and he could hear the left main landing gear tire squealing. He used right brake and differential engine power to attempt to correct the swerve to the left. The aircraft ran off the runway and as it slowed, it swerved violently to the left and the left main landing gear separated. The aircraft came to rest and they evacuated the aircraft. The copilot stated that during taxi for takeoff at Pensacola, they felt a very brief sliding or skipping sensation as they turned into the engine run-up area at the end of the runway. They attributed the sensation to the aircraft sliding while turning on the wet taxiway. He and the pilot agreed that they would be alert for any unusual sensations during the takeoff run, and if there were any, they would abort the takeoff and return to the hangar to check the cause. During taxi onto the runway and during the takeoff run, everything was normal. After takeoff, when they raised the gear handle to retract the landing gear, the landing gear did not retract. The gear warning horn also sounded. They tried again with the same results. They elected to continue to their destination with the gear down, because the destination airport had long, wide runways. On approach to the destination, they could not see the runway and performed a missed approach. They then returned to Pensacola. As they touched down, the aircraft began pulling to the left and there was a squealing sound, like the left main gear brake was locked. They attempted to correct the left turn but the aircraft continued to pull to the left and departed the runway. When the aircraft came to a stop they evacuated the aircraft. Company maintenance personnel stated the bolt, which connects the left main landing gear scissors, was pulled through the washer and the scissors was disconnected. They stated they believe this happened during takeoff and prevented the ground switch from opening during liftoff, thus preventing the landing gear from retracting. The washer that failed was the subject of Cessna Aircraft Company, Service Information Letter ME83-37, dated November 23, 1983. The title of this letter was "Main Landing Gear Scissor Washer Replacement". The purpose of this letter was "to recommend replacement of the two outer washers on the main landing gear scissors link for improved service life and main gear wheel alignment retention". The compliance period was during the next routine 100-hour inspection. See Service Information Letter.
The failure of the left main landing gear scissors washer during taxi for takeoff, and collapse of the left main landing gear. A factor in the accident was the failure of unknown maintenance personnel to comply with a manufacturers service letter concerning the scissors washers.
Source: NTSB Aviation Accident Database
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