In April 2010, after a base maintenance check at Exeter, England, a Bombardier DHC-8-102 was flown uneventfully to East Midlands Airport to be repainted. During the return ferry flight to Exeter, the right engine developed a significant oil leak and lost oil pressure, so the flight crew shut the engine down. Subsequently, the crew noticed the left engine also leaking oil, with a fluctuating oil pressure, so they diverted to Bristol, where they landed safely.
The oil leaks were traced to damaged O-ring seals within the oil cooler fittings on both engines. Both oil coolers had been removed and refitted during the maintenance at Exeter. It was probably during re-installation that the O-ring seals were damaged.1
During the investigation carried out by the U.K. Air Accidents Investigation Branch (AAIB), it was found that over the 17-week period leading up to the end of a C-check, one of the maintenance technicians working on the aircraft had worked an average of 57 hours per we…
