What happened
On 15 August 2014, a Jetstream 31, registration G-GAVA, was performing a scheduled passenger flight from Belfast City Airport to Doncaster Sheffield Airport. The flight, carrying two crew members and one passenger, proceeded normally through departure, cruise, and approach.
Upon touchdown on Runway 20 at 1836 hrs, the aircraft decelerated normally. However, as the groundspeed reached approximately 65 kt, the left wing suddenly dropped. The aircraft began to yaw left, and the pilot was unable to maintain directional control using the rudder or nosewheel steering. The left main landing gear detached from its mounts, causing the aircraft to slide along the runway on its remaining gear, left wingtip, and baggage pannier. The aircraft eventually veered off the paved surface and came to rest on the adjacent grass. There were no injuries to the crew or the single passenger.
The investigation
The AAIB examined the wreckage and reviewed flight data from the FDR and TAWS. The investigation focused on the structural failure of the left main landing gear. Investigators found that the forward pintle housing at the top of the left landing gear cylinder had failed.
Crucially, the investigation looked into a previous accident involving the same aircraft (then registered G-CCPW) in 2012, which had suffered a similar right-side gear failure. A design modification had been implemented following that event to install a protective washer and a liquid gasket to prevent corrosion. However, investigators discovered a fouling condition where the protective washer was able to rotate. This rotation caused the washer to rub against the housing, degrading the surface protection and allowing moisture to penetrate.
Findings
- The primary cause of the landing gear failure was stress corrosion cracking in the forward pintle housing.
- A previously implemented design solution intended to prevent such cracking failed because a fouling condition allowed the protective washer to move.
- This rotational movement destroyed the liquid gasket and the surface protection on the housing, creating an environment where corrosion pits could form and cracks could propagate.
- The landing gear cylinder material (DTD 5094) is inherently susceptible to this type of cracking.