What happened
On 31 October 2014, a Boeing 757-300, registration G-JMAB, was performing a scheduled passenger flight from London Gatwick to Hurghada, Egypt. During the takeoff roll, a 'wing slide' advisory message appeared on the cockpit's Engine Indication and Crew Alerting System. The crew elected to continue the departure, later deciding to return to Gatwick after consulting with company operations. Because the aircraft was approximately nine tonnes above its permitted landing weight, the crew entered a holding pattern to burn off fuel.
While descending on final approach, passengers and cabin crew reported loud bangs and a sensation of airframe shuddering. Some passengers observed a white object detaching from the right side of the aircraft. The commander noted that the autopilot was struggling to maintain wings level and required significant left aileron input to counteract an uncommanded roll. The aircraft landed safely at Gatwick, but a subsequent inspection revealed that the right over-wing slide had detached from its carrier and the fuselage had sustained scuff marks.
The investigation
The AAIB examined the aircraft's over-wing escape system, which uses a gas-powered actuator to deploy the slide. Investigators found that the right slide carrier had deployed and rotated outwards, causing damage to the fuselage wing root upper fairing and bending the actuator rod. The investigation also looked into recent maintenance, noting that the aircraft's gas bottle had been replaced the previous night.
Furthermore, the investigation identified a discrepancy in how aircraft doors were designated between the airline's cabin crew and the airport fire and rescue service. It was also noted that the aircraft lacked certain updated safety markings and that a mechanical issue with a flap screw jack had been causing significant vibrations in the area of the slide release handle.
Findings
- The right over-wing slide carrier deployed in flight, allowing the slide to unravel in the slipstream.
- The primary cause was the gradual movement of the slide release crank handle into an unsafe position.
- This movement was likely facilitated by reduced breakout friction in the handle mechanism and high-frequency vibrations caused by a loose flap system component.
- The lack of updated alignment markings on the maintenance panel made it difficult for engineers to identify that the handle was not correctly secured.
- The aircraft had not yet been updated with a Service Bulletin designed to provide more positive locking and clearer visual indicators for the handle position.