History of the Flight
On 6 June 2001 at 0551 UTC, a Cessna 310R (registration G-BGTT) was taxiing at Bournemouth International Airport for a cargo flight to Guernsey. The pilot felt a sensation he described as a tyre deflation. After a ground check by airport personnel, nothing abnormal was found, and the pilot continued. During takeoff from Runway 08, no issues were noted. However, after selecting landing gear up, the red 'in transit' light remained on, indicating the gear was not locked. The pilot selected gear down but only obtained green lights for the nose and port main gears. Multiple attempts to cycle the gear failed to lock the starboard main gear.
The pilot entered a holding pattern and performed two flypasts for visual inspection. The tower reported the starboard main wheel was at 90 degrees to the fore/aft direction and the gear was not locked down. The pilot chose Runway 26 for an emergency landing due to its length and the sun position. With gear selected down and flaps/lights up, the starboard engine was shut down over the threshold; the port engine was shut down after touchdown. Upon touchdown, the starboard wing dropped as the landing gear collapsed. The pilot used left brake and swerved onto grass, stopping safely. The pilot evacuated unharmed.
Engineering Investigation
Inspection revealed that the starboard main landing gear upper and lower torque links had become disconnected at the centre hinge point, allowing the wheel to rotate laterally. During retraction, the misaligned wheel contacted the gear bay structure, overloading and fracturing the actuating bellcrank. This prevented gear extension or retraction. The bolt (AN175-20) connecting the torque links had pulled through the upper torque link, with the nut and split pin intact but the washer under the bolt head missing. The bushing (P/N 5041013-2) had also pulled out. A washer found under the nut had an indentation indicating it had previously been under the bolt head, suggesting it was inadvertently transferred during maintenance on 21 February 2000, when the torque links were disconnected for component replacement. This washer was the incorrect size (9/16" O.D.) instead of the correct 0.75" washer (P/N 5045018-1). A visual inspection on 22 May 2001 (seven flight hours prior) found no defects.
Examination of the port landing gear revealed it had also been assembled with incorrect 9/16" washers under both bolt head and nut, but in that configuration, the bolt was still retained. A replacement starboard landing gear from an approved supplier also had incorrect 9/16" washers, which were corrected before installation.
The Cessna 310/310R Illustrated Parts Catalogue (IPC) lists correct washer part numbers, but diagrams and maintenance manual instructions do not clearly indicate washer locations, allowing misinterpretation.
Safety Recommendations
The AAIB issued two safety recommendations: 2001-71, urging the manufacturer to issue an All Operators Letter for inspection of main landing gear torque link assemblies for correct washer installation; and 2001-72, calling for amendments to the IPC and Maintenance Manual to clearly identify washer locations to reduce assembly errors.