Incident Overview
On July 22, 2009, about 1400 Pacific daylight time, a Piper PA-30, registration N7504Y, suffered a landing gear collapse during the landing roll at Walla Walla, Washington. Walla Walla University operated the airplane under 14 Code of Federal Regulations Part 91. The pilot, who held a commercial pilot certificate with a certified flight instructor certificate, and one passenger were not injured. The aircraft sustained substantial damage to the airframe.
Flight Details
The local maintenance test flight departed Walla Walla about 1345. Visual meteorological conditions prevailed, and no flight plan had been filed. The pilot remained in the airport traffic pattern and completed one takeoff and landing. Prior to the second landing, the landing gear was down, and all indications appeared normal. After reducing power for landing, the pilot did not hear an audible alert warning horn. As the airplane touched down, the gear collapsed. The pilot noticed smoke coming from the circuit breaker panel on the floor and exited the airplane.
Observations
Air traffic control tower personnel reported that they thought the landing gear appeared to be down prior to touchdown.
Maintenance History
The operator reported previous trouble with the landing gear circuit breaker popping during gear extension and retraction. Six flight hours before the accident, they replaced the right main landing gear push/pull retraction/extension cable, the gear motor control contactor, and the gear motor circuit breaker. Ground and flight tests were successfully completed without a recurrence. The operator stated that the airplane had about 8 to 10 landing gear cycles prior to the accident flight with no anomalies noted, leading them to believe the issue had been resolved.
Post-Accident Examination
Post-accident examination revealed that the landing gear motor circuit breaker had tripped. The landing gear warning horn circuit, powered by the gear motor circuit, would not activate with the circuit breaker tripped.