What happened
On the night of 8 August 2003, an ATR 42-300, registration EI-CBK, operated by Aer Arann, experienced an engine failure while cruising at 18,000 feet. The aircraft was traveling from Luton, UK, to Galway, Ireland, when the right-hand engine spontaneously decelerated and stopped. The flight crew immediately issued a PAN call to Shannon Air Traffic Control.
While the crew initially considered returning to Dublin or diverting to Belfast, heavy fog at those locations prevented landing. The crew subsequently decided to divert to Shannon. During the approach, the crew maintained a higher glide slope to ensure sufficient distance in the event of a total loss of power. The aircraft landed safely at Shannon Airport on a single engine and taxied to the ramp without further incident.
The investigation
The investigation focused on the fuel management and the sequence of refueling events leading up to the incident. Investigators examined the aircraft' and found that the fuel gauges for both the left and right tanks were providing unreliable or zero readings.
At a previous stop in Waterford, the captain had personally supervised refueling after encountering issues with the automated system. To ensure the right-hand tank was filled, the captain used a manual toggle ring at the wing refuelling point. Because the captain was positioned near the wing, he could not verify which valve had been opened by the indicator light in the cockpit. Similarly, during a subsequent refueling in Luton, the captain again used the manual trigger to open the right-hand valve after the refueller refused to do so. Because he could not reach the dip points under the wing, no physical verification of the fuel levels was performed before the final leg.
Findings
- The right-hand engine stopped because the fuel tank feeding this engine was empty.
- The crew was operating with unreliable fuel gauges, as the left-hand gauge had been reading zero for some time.
- The captain's reliance on the manual toggle ring at the refueling point, combined with the inability to verify the valve status via cockpit lights, led to an incorrect assumption that the right-hand tank had been replenished.
- A lack of familiarity with the manual refueling valves contributed to the error.
- The decision to proceed without a physical dip-stick check of the fuel levels meant the actual fuel state was unknown.