What happened
On 5 April 2008, a Beech B58 Baron, registration G-OSDI, was returning to Leicester Airport following a flight from Guernsey. During the approach, the pilot noticed that the landing gear indication was abnormal; while the left main and nose gears showed green 'down and locked' lights, the right gear indicated as unsafe, accompanied by a warning horn.
After several unsuccessful attempts to reselect the gear, the pilot opted to land on Runway 28, requesting the presence of fire crews. The aircraft touched down at approximately 85 knots. During the landing roll, the right main gear collapsed, causing the aircraft to slew approximately 80 degrees before coming to a halt. The pilot, who was the sole occupant, escaped the aircraft uninjured after the crew had to force open the jammed right-side door.
The investigation
The AAIB investigation focused on the landing gear mechanism and the condition of the aircraft's components. Examination of the G-OSDI revealed that the right main gear actuator rod had buckled, which had disconnected it from the actuator and damaged the inboard door.
Testing of the landing gear system demonstrated that the main gear uplock rollers on both sides, as well as a roller in the nose gear, had seized. When the gear was manually extended, the seized rollers caused the mechanism to jam. The investigation also noted that the aircraft's maintenance records showed no evidence of lubrication for the right roller, and considerable corrosion was present on various main landing gear components.
Findings
- The right main gear collapsed because the extension/retraction rod was unable to move the gear into the downlock position.
- Seized uplock rollers on both main gears and the nose gear prevented the gear from fully extending and locking.
- The contact between the seized roller and the uplock caused a transient jam that distorted the actuator rod.
- The landing gear system was improperly rigged, meaning the rollers were positioned such that a pilot's pre-flight inspection would not easily reveal the lack of free rotation.