Overview
During a flight, a fuel leak occurred due to the migration of a fuel transfer tube. The subsequent investigation identified the root cause as a missing locking plate, which had likely not been reinstalled during previous maintenance.
Investigation Findings
Examination of the fuel transfer tube assembly showed no damage to the locking plate mounts. The locking plate itself was entirely missing, while the fasteners were found installed in place. This configuration indicated that the locking plate did not fail during operation, but was probably not reinstalled when the fuel transfer tubes and nozzles were replaced.
Incident Sequence
Over the course of 86 flight hours following the replacement, the unsecured fuel transfer tube slowly migrated out of the nozzle adaptor. On the incident flight, the migration had progressed to the point where fuel under pressure was able to escape from the adaptor, as documented in an annotated figure from the operator.