What happened
On March 10, 2018, a Beechcraft King Air B250 was performing a flight from Bolzano (LIPB) to Katowice Pyrzowice (EPKT). Upon reaching a cruising altitude of FL310, the crew observed an imbalance in fuel consumption between the left and right tanks, noting increased usage in the left tank. Following a visual inspection, the crew identified a fuel leak originating from the left engine nacelle.
After evaluating the operational situation, weather conditions, and available landing sites, the crew decided to divert to the nearest suitable airport, Brno (LKTB). The crew notified air traffic control in both Austria and the Czech Republic and proceeded to shut down the left engine. The aircraft landed at Brno without incident, remaining within the maximum allowable weight limits. However, during taxiing with the left engine inoperative and amidst crosswinds, the left tire sustained damage.
The investigation
An inspection of the aircraft following the landing revealed that the middle section of the left engine drain valve was missing. The investigation established that the material at the attachment points of the valve's external components had been torn away, which had facilitated the fuel leak from the left tank.
Findings
- The direct cause of the incident was the failure of the middle section of the left engine drain valve, which resulted in a fuel leak.
- A contributing factor was the insufficiently secure fastening of the valve's middle section, which relied on a method of crimping the material at six specific points to prevent the components from separating.
Safety action
Following the incident, the operator implemented the following preventive measures:
- The crew is now required to inspect the technical condition of the valves before every flight, specifically checking the security of the middle section's attachment.
- The operator met with a manufacturer representative, who confirmed that investigations are underway to address this recurring issue, which has affected other aircraft of this model. New valves are currently being secured at eight points instead of the previous six.