A recent Jetstream 31 gear failure at Doncaster Airport, U.K., resulted from stress corrosion cracking in the landing gear leg, according to a preliminary report issued by the AAIB.
The Jetstream 31 took off from Belfast City Airport (BHD) at 17:45 hrs operating a scheduled air service to Doncaster with one passenger and a crew of two pilots on board. The captain was the Pilot Flying (PF) and the co-pilot was the Pilot Monitoring (PM).
The departure, cruise and approach to Doncaster Sheffield Airport were uneventful. The aircraft touched down at 19:36 hrs with an IAS of 102 kt and a peak normal acceleration of 1.3 g, and the commander moved the power levers aft to ground idle followed by reverse. As the aircraft decelerated, the commander moved the power levers forward to ground idle and asked the co-pilot to move the rpm levers to taxi. At an IAS of 65 kt, eight seconds after touchdown, the left wing dropped suddenly, the aircraft began to yaw to the left and the commander was unable to maintain directional control with either the rudder or the nosewheel steering tiller. The aircraft ran off the left side of the runway and stopped on the grass having turned through approximately 90º. The left landing gear had collapsed and the aircraft had come to a halt resting on its belly, right landing gear and left wing.
The captain pulled both feather levers, to ensure that both engines were shut down, and switched the electrics master switch to emergency off. The co-pilot radioed for emergency services.
A review of the previous 82 landings recorded on the FDR has not identified any of concern but it was noted that a peak normal acceleration of 1.72g was recorded during the eighteenth landing prior to the accident. However, this was within the landing gear limit load.
Preliminary findings indicate that the failure was initiated as a result of stress corrosion cracking in the forward yoke pintle at the top of the left landing gear leg.
Incidently, this same aircraft (Jetstream 31 msn 785) suffered a failure of the right hand main landing gear while landing at Isle Of Man-Ronaldsway Airport (IOM), March 8, 2012. It was determined that in that case the landing gear had failed as a result of intergranular corrosion / stress corrosion cracking of the forward yoke pintle.
A preventive measure taken following this accident involved a modification to install a protective washer on the forward face of the yoke pintle. It appears that this washer could rotate out of position, negating the protection. The AAIB issued two safety recommendations to EASA , among others mandating an effective inspection regime for the Jetstream 31 that will detect cracking and prevent failure of the yoke pintle of main landing gear legs.
- AAIB Bulletin S5/2014 (PDF)