NTSB Identification: IAD04LA029.
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Accident occurred Friday, July 02, 2004 in Portland, ME
Probable Cause Approval Date: 12/03/2004
Aircraft: Cessna 421B, registration: N421KS
Injuries: 2 Uninjured.

NTSB investigators may not have traveled in support of this investigation and used data provided by various sources to prepare this aircraft accident report.

Line personnel reported to the pilot that while the airplane had been parked on the ramp, heavy wind and rain "hydroplaned" the airplane across the ramp about 25 feet. After takeoff, the pilot retracted the landing gear and noticed an unfamiliar "clunking" noise during the retraction cycle. During the approach to the destination airport, he extended the landing gear and noted all three of the landing gear down and locked indicator lights were green. Sometime during the rollout he heard the "clunk" noise again, and the right wing began to settle lower than normal. The airplane then began to veer to the right and came to rest in the grass on the right side of runway. Examination of the right main landing gear revealed that two components of the down-lock mechanism had broken. The parts were submitted to the Safety Board Materials Laboratory. Metallurgical examination of the mating fractures revealed features typical of overstress separation. The fractures contained no evidence of fatigue.

The National Transportation Safety Board determines the probable cause(s) of this accident to be:

Failure of the right main landing gear down-lock mechanism resulting in the collapse of the right main landing gear.

Full narrative available

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