What happened
On 7 September 2003, a Boeing 757-236, registration G-CPER, operated by British Airways, was performing a scheduled passenger flight from London Heathrow to Paris. Shortly after departure, the flight crew noticed a smell of hot oil and electrical burning in the cockpit, a sensation that had been present during engine startup.
As the aircraft climbed, the crew encountered significant difficulties with roll control. The investigation later revealed that during a major maintenance check completed 26 days prior, several access panels on the right wing trailing edge had not been correctly secured. Furthermore, the aircraft's engines had been overfilled with oil, contributing to the persistent burning smells experienced by the crew.
The investigation
The AAIB investigation focused on several technical areas, including the roll control malfunction, the source of the burning smells, and the autothrottle system. Investigators examined the maintenance history of the aircraft, specifically looking at the work performed during the recent heavy maintenance check.
Technical analysis of the wing trailing edge flap system was conducted to understand the roll control problem. The investigation also scrutinized the engine oil storage and quantity indication procedures, as well as the engine bearing sealing and venting mechanisms. The investigators reviewed the maintenance records, job cards, and the specific procedures used by technicians for engine oil servicing and the installation of wing access panels.
Findings
- Maintenance personnel failed to properly secure two specific flap access panels (666AR and 666BR) following maintenance work on the right wing.
- The engine oil had been overfilled beyond the recommended limits, which caused the hot oil smell in the cockpit.
- There were inconsistencies in how engine oil servicing was performed, with technicians not always adhering to the required time intervals after engine shutdown.
- The maintenance organization's quality oversight was found to be insufficient in monitoring day-to-day practices in the hangar environment.