What happened
On 31 January 2006, a Rockwell Commander AC11, registration N115TB, was conducting a test flight following significant maintenance work involving a crankshaft replacement. During the flight, the pilot noticed that the green 'down and locked' indication for the nose landing gear failed to illuminate. After attempting several gear re-selections and performing maneuvers to encourage extension, the pilot utilized the emergency gravity-extension system. Despite this, air traffic control observed that the nose gear remained only partially extended.
During the landing approach at Oxford Airport, the pilot shut down the engine just before touchdown. As the aircraft transitioned onto the runway, the nose gear collapsed. The impact caused damage to the propeller, the nose landing gear doors, and the nose landing and actuator. Both crew members exited the aircraft without injury.
The investigation
Investigators examined the aircraft and found that the nose gear had been pushed toward the retracted position during the ground roll. A review of the nose gear microswitch revealed a missing attachment screw nut, which was found loose; while this could cause intermittent light failures, it was not considered the primary cause of the collapse.
Upon disassembling the nose gear actuator, investigators discovered a small piece of metallic debris, likely a crushed rivet head, trapped on the shaft side of the piston. Additionally, the investigation noted that a flexible fuel drain pipe was loose around the front of the nose leg. It was noted that if this pipe were to become loose enough, it could potentially jam the down spring lever arm, preventing full extension.
Findings
- The nose landing gear failed to reach the fully extended and locked position during landing.
- Metallic debris was found inside the nose gear actuator, which may have interfered with the piston movement.
- A loose fuel drain pipe was identified as a potential factor that could cause the gear to jam by fouling the down spring lever arm.
- It could not be conclusively determined which factor, the internal debris or the external fuel pipe, was responsible for the failure of the gear to extend fully.