What happened
On January 19, 2010, a Fairchild Dornier SA 227-DC Metroliner was on final approach to runway 07 at Stuttgart Airport, arriving from Brno, Czech Republic. Upon deploying the landing gear, the crew observed that while the nose gear and left main gear indicators showed green, the right main gear indicator remained red.
The crew attempted to extend and lock the gear twice without success. They subsequently initiated a missed approach and followed radar vectors to the approach course. During this time, the crew performed multiple attempts to extend the gear using emergency procedures. To verify the gear configuration, the crew requested the tower perform a visual inspection via a low flyover; the tower confirmed the right main gear was indeed not extended.
A second missed approach was performed, during which the crew entered airspace north of the airport to attempt gear extension through maneuvers involving positive and negative G-loads. After nine minutes of unsuccessful attempts, the crew declared an emergency and decided to land using only the nose gear and the left main gear. Following touchdown, the aircraft could not maintain the left wing; the crew steered the aircraft into the grass to allow the right wing to settle on soft ground. The engines were shut down and propellers feathered immediately upon touchdown. There were no fatalities or injuries, though the aircraft sustained light damage.
The investigation
The BFU examined the aircraft's landing gear components and the flight path. Investigators found that the right main gear was stuck in a partially extended position. During post-accident testing, the gear could be manually locked into the position it held during the approach. The investigation also noted that the flight data recorder (FDR) and cockpit voice recorder (CVR) had not recorded data since January 11, 2010, because the power supply had been inadvertently disconnected during a previous flight, a fact that went unnoticed by the crew.
Findings
- The primary cause of the landing gear failure was the outer gear door jamming against the gear bay edge.
- The investigation identified a notch and waviness in the gear bay edge, caused by the hinge arm of the door pressing against the structure over an extended period.
- The outer gear door was found to be misaligned, with a 2 cm gap at the forward edge of the bay.
- The crew correctly followed the emergency checklist, including the use of the emergency gear release and the use of aerodynamic forces to attempt extension.