What happened
On 30 September 2015, a Saab 340 was involved in a runway excursion incident. During the flight, a failure occurred within the hydraulic system. While the aircraft was able to complete a safe landing, the excursion occurred after the aircraft had already come to a complete stop on the runway.
The investigation
Investigators determined that the mechanical failure originated in the right main landing gear. The investigation focused on the integrity of the hydraulic components and the crew's adherence to established shutdown procedures. It was established that the aircraft's behavior during the landing phase remained consistent with its type design, but the subsequent movement on the runway was linked to how the engines were managed following the stop.
Findings
- The primary cause of the hydraulic leakage was a broken lock swivel located in the right main landing gear.
- The specific swivel involved had been in service for 29 years and did not meet the improved standard outlined in Service Bulletin Saab 340-32-142.
- The crew did not follow the published engine shutdown procedures as specified in the aircraft manuals.
- While the emergency hydraulic hand pump was capable of supporting a safe landing, the fluid levels were limited, making unnecessary braking or nose wheel steering risky.
Safety action
Following safety recommendations, Saab AB updated the Expanded Abnormal Checklist within the Aircraft Operation Manual (AOM). The revised checklist, effective June 2017, provides specific guidance for hydraulic fluid loss, including:
- Confirming the adequacy of the emergency hand pump for a safe landing.
- Warning against unnecessary use of braking or nose wheel steering due to limited fluid.
- Recommending the use of fire handles as the safest method for engine shutdown.
- Instructing the crew to stop on the runway and request towing services.