Accident Details
On March 16, 2025, at 1424 mountain daylight time, a Beech C90A, registration N513JM, was substantially damaged during a landing at Helena Regional Airport (HLN), Helena, Montana. The two pilots on board were not injured. The flight was conducted under Title 14 Code of Federal Regulations Part 91 as an other work use flight, intended for one pilot to undergo the flying portion of a checkride.
Sequence of Events
During the flight, the landing gear was raised and lowered several times without incident. While conducting a simulated instrument approach to HLN, the pilots extended the landing gear but the nose landing gear did not indicate down and locked. They performed a missed approach to troubleshoot. Initially unable to raise the gear, they noticed the landing gear relay circuit breaker had tripped. After resetting it and cycling the gear, the landing gear indicator circuit breaker tripped. They reset that breaker and cycled the gear again.
Further troubleshooting showed the nose and right main landing gear indicated down and locked, but the left main did not. Noting the red gear in-transit lights were off and the gear unsafe horn was silent, the pilots believed they had only a gear indication issue and did not complete the manual extension checklist, which includes a hydraulic hand pump.
The pilots performed a low approach near the air traffic control tower. The controller reported the gear appeared extended. They landed on runway 27. During the landing roll at about 30 knots, the left main landing gear collapsed and the left wing impacted the runway, causing substantial damage to the left wing and fuselage.
Postaccident Examination
An FAA inspector and the operator's Director of Maintenance examined the airplane. Visual inspection of the left main landing gear revealed several wires to the downlock switch were broken, and the Up position switch had been torn from its mount and was not located.
The airplane was jacked and the landing gear cycled multiple times. When selected down, the left main landing gear did not fully extend and lock; the green down light did not illuminate by the time the hydraulic pump stopped. After the pump stopped, the red in-transit lights extinguished and the warning horn did not sound. During some cycles, the broken switch wires shorted against the structure until the gear relay circuit breaker tripped, stopping the gear mid-transit.
When the manual extension hydraulic hand pump was used after selecting gear down, three pumps caused the left main gear to fully extend and lock, and the green light illuminated.
Textron Aviation technical data indicate that landing gear extension and retraction are powered by hydraulic pump actuators. When fully extended, the nose gear actuator internal lock and main gear drag brace downlock hooks hold the gear. Downlock switches interrupt current to the pump motor and illuminate green lights. The broken downlock switch wires (2-20, 5-20, 8-20, 9-20, 10-20, 11-20, 12-20) had specific functions: 2-20 to the unsafe horn, 5-20 to red in-transit lights, 8-20 to the pump motor; the others were spare.
Maintenance History
The FAA inspector provided photos of an exemplar Beech C90A at HLN showing the left main gear downlock switch wire bundle routed differently than on the accident airplane. Although the maintenance manual and illustrated parts catalog depict routing, no specific instructions for installation and routing were present. The airplane had operated over 860 hours and 754 landings since maintenance in 2021 that may have required the downlock switch removal and reinstallation. No other downlock switch maintenance was recorded.