What happened
On 14 November 2007, at 15:10Z, a Tornado GR4, registration ZA554, was conducting a post-maintenance flight test at RAF Marham. The aircraft, which was under the responsibility of the BAE Systems Combined Maintenance and Upgrade Facility (CMU), was performing a negative-g loose article check using an inverted flight manoeuvre.
While flying at 5,900 feet and 400 knots, a loud bang occurred, followed by rapid depressurisation of the cockpit. The pilot managed to recover the aircraft to straight and level flight. Upon inspection, it was discovered that the rear cockpit transparency had shattered and the rear cockpit was unoccupied. Both the Weapons Systems Officer (WSO) and the rear ejection seat were missing from the aircraft. An in-flight inspection by a USAF F-15E confirmed the absence of the seat and crew member. The WSO was later located on the ground in the ejection seat; the individual had sustained fatal injuries.
The investigation
The Board of Inquiry examined the maintenance history of ZA554, noting that significant unscheduled work had been performed prior to the flight. Due to pressure to meet schedules, a recovery plan involving 24-hour shifts had been implemented.
The investigation focused on the Aircraft Assisted Escape System (AAES). While the Board could not definitively trace the exact sequence of engineering events due to inconsistencies in maintenance documentation and logs, they examined the status of the Top Latch Plunger (TLP) and the seat installation process.
Findings
- The primary cause of the accident was that the Top Latch Plunger (TLP) was not correctly engaged to lock the rear ejection seat in place.
- This failure allowed the seat to exit the aircraft during the inverted negative-g manoeuvre.
- The TLP and spring assembly were not recovered from the accident site.
- The investigation identified that a properly conducted TLP check should have detected the incorrect fitment.
- Contributing factors included shortcomings in both aircrew and groundcrew training regarding the TLP locked check, as well as a lack of clarity in certain maintenance procedures.
- Procedural and human factors during the maintenance phase increased the likelihood of the error occurring.