What happened
On 23 November 2009, a Beech 200 Super Kingair, registration G-BGRE, was performing a private flight from Langford Lodge in Northern Ireland to Chalgrove Airfield in Oxfordshire. Following the retraction of the landing gear after takeoff, the crew observed that the red gear unsafe warning light remained illuminated. During the approach, the crew attempted to extend the gear again, which resulted in the main gear legs locking into place, but the nose gear failed to fully deploy.
As the aircraft touched down, the pilot shut down the engines just before the nose gear made contact. Upon touchdown, the nose landing gear collapsed, causing the propellers to strike the ground and the aircraft to come to a stop off the runway centreline. There were no injuries to the two crew members on board, though the aircraft sustained damage to the nose, propellers, and gear doors.
The investigation
Investigators examined the aircraft's landing gear system, which is driven by an electric motor and a gearbox. Upon removing the cabin floor, the team discovered that the nose gear drive chain had separated. Detailed inspection of the recovered parts revealed that a connecting master link had failed; specifically, one pin had fractured and several plates were distorted.
Metallurgical analysis of the fractured pin confirmed the failure was caused by a single overload event rather than fatigue. The investigation also found that the pins may not have been fully pressed through the rear cover plate. Furthermore, the maintenance staff were unaware of a manufacturer's communiqué regarding a specific modification to the master link assembly, which recommended using a 'press-fit' plate to prevent such detachments.
Findings
- The nose gear collapse was caused by the failure of the nose gear drive chain.
- The failure of the chain pin was due to an overload event, potentially caused by shock loads generated when the electric motor brake activates during gear retraction.
- The master link was not configured with the recommended 'press-fit' cover plate, which may have allowed the failed link to become completely detached.
- The loss of the chain rendered the emergency gear extension system ineffective, as the system relies on a serviceable drive chain to lower the gear leg.