What happened
On 19 August 2009, a Rockwell Commander 112TC, registration G-BLTK, was performing a private flight when the pilot identified a malfunction during the landing sequence. While joining the crosswind leg at approximately 110 kt, the landing gear was selected down. Although the green lights for the main landing gear indicated they were locked, the indicator for the nose gear remained unlit.
In an attempt to rectify the issue, the pilot performed several maneuvers at different g-loads to encourage the nose gear to extend. These efforts included cycling the gear using both the manual gravity drop system and the standard hydraulic extension system. After a low pass by the control tower failed to resolve the problem, the pilot declared a Mayday and prepared for an emergency landing.
During the approach, the pilot utilized full flaps and maintained a speed slightly above the minimum approach speed. To mitigate the impact, the pilot turned off the fuel selector, leaned the mixture, and deactivated the battery master switch prior to touchdown. The aircraft landed on its main gear, and the pilot applied back pressure to keep the nose elevated. However, the nose eventually descended, causing the 3-bladed propeller to strike the ground, resulting in damage to the propeller and potential engine shock-loading.
The investigation
An examination of the aircraft by a licensed engineer established that the nose gear failed to extend because the right nose gear door had jammed near its hinge. The investigation also revealed that a screw connecting the right lower engine cowling to the nose gear structure had failed in shear.
It was noted that the hinge for the door operates within a narrow slot with sharp edges. This design allowed for the possibility that the door could jam. The investigation considered whether the screw failure was the primary cause or a secondary effect of the door's failure and the subsequent force exerted by the nose gear actuator.
Findings
- The primary cause of the gear failure was the jamming of the right nose gear door at its hinge.
- The door hinge design, featuring a narrow slot with sharp edges, created a risk of the door becoming stuck.
- A screw attaching the engine cowling to the nose gear structure had sheared, which may have been caused by the mechanical stress of the gear actuator attempting to operate against the jammed door.