What happened
On 6 August 1998, a Rockwell Commander 114, registration G-BFAI, was performing a private flight approaching Leicester Airport. During the downwind leg of the landing circuit, the pilot attempted to deploy the landing gear but observed that the three green indicators failed to illuminate, signaling that the gear had not locked down.
Following the failure, the pilot exited the circuit and spent approximately 8 to 80 minutes attempting to manually extend the gear. After several unsuccessful attempts to use the primary electro-hydraulic system, the pilot attempted to utilize the emergency extension mechanism, but found the handle was jammed in the up position. Consequently, the pilot opted to land on a grass area parallel to Runway 28 with the gear only partially extended. The landing resulted in damage to the propeller, engine shock-load, and the nosewheel doors and right wing tip, but there were no injuries to the two occupants.
The investigation
Investigators examined the aircraft's hydraulic and mechanical systems to determine why the gear failed to deploy. The inspection of the electro-hydraulic power pack revealed that a long-term hydraulic fluid leak had contaminated the electric drive motor's carbon brushes. This contamination had softened the carbon, leading to accelerated wear and the eventual failure of the motor.
Regarding the jammed emergency handle, the investigation focused on the cockpit pedestal. It was discovered that the plastic trim panel surrounding the emergency handle had been installed upside-down. Furthermore, the three self-tapping screws used to secure this panel were 5/8 inch long, rather than the required 3/8 inch. One of these excessively long screws had protruded into the space beneath the lever arm, physically obstructing the movement of the handle and preventing it from being moved to the down position.
Evidence suggested that during recent interior refurbishment, including the replacement of carpets and seats, the trim components had been incorrectly reinstalled. The investigation found that the shorter, correct screws had been mistakenly used to attach the footwell air vent trim, while the longer, incorrect screws were used on the emergency handle trim.
Findings
- The primary failure of the landing gear deployment was caused by a failure of the electro-hydraulic power pack due to hydraulic fluid contamination of the motor's carbon brushes.
- The emergency extension system was rendered inoperable because the emergency handle was physically blocked by an oversized screw.
- The installation of the cockpit trim panel was incorrect, as it was mounted upside-down and secured with screws of an incorrect length.
- Discrepancies were noted in the maintenance records regarding the responsibility for the reinstallation of internal aircraft trim following carpet and seat refurbishment.