Occurrence
On 6 December 1999, at approximately 1800 UTC, a Boeing 757-236 (registration G-BMRC) was en route from London Heathrow to Manchester on a public transport flight. As the aircraft climbed through FL100 near Woburn, the flight crew felt a slight jolt. Shortly thereafter, cabin crew reported that a passenger near row 22 had heard a thud from the right side of the aircraft. All aircraft systems and handling remained normal, and due to darkness, a visual inspection was not possible.
Post-Flight Inspection
Upon arrival at Manchester, an engineering inspection was conducted to determine the cause of the thud. No defect was found, and it was initially assumed that baggage had shifted. The first officer performed a walk-around check, again finding no defect. After boarding, there was an ATC delay and the aircraft remained on stand. Another engineer passing the aircraft noticed a missing 3-foot-square panel and notified the crew. The missing panel was from the wing-to-body fairing area; its absence was difficult to spot in the dark and rain. The operator subsequently publicised the need for vigilance.
Panel Details
The panel had separated just above its lower edge, which remained fastened to the aircraft. The panel itself was not recovered, so the condition of its fasteners could not be assessed. However, two of the anchor nuts for the leading edge fasteners were found to be cross-threaded; all other anchor nuts were serviceable with satisfactory rundown torques. The operator concluded that the panel detached along its forward edge, and that the top and rear side attachments failed in overload. The panel had last been removed in April 1999 and was routinely checked for security in October 1999.
Aircraft and Crew Information
The aircraft was a Boeing 757-236, manufactured in 1988, powered by two Rolls-Royce RB211-535C turbofan engines. The commander held an Airline Transport Pilot's Licence, was 51 years old, and had 12,000 total flying hours (2,000 on type). There were 9 crew members and 125 passengers on board; no injuries were sustained by any persons.