UK investigators have disclosed that a trailing-edge panel shed by a One Air Boeing 747-400 freighter was discovered adjacent to runway 27L at London Heathrow two months later.
The 1m-long panel, normally located on the upper left wing surface next to the high-speed aileron, was found to be missing after the jet arrived at Heathrow on 6 January last year.
Possible damage to this panel was the subject of a Boeing service letter in November 2010, which linked it to cracking in trailing edge ribs.
While the letter mentioned the panel could be damaged if the ribs fractured, it added: “Damage to the ribs and panel, including the partial departure of the panel during flight, is not considered safety-related and does not significantly affect the controllability of the airplane.”
This indication that no safety issue was posed led the carrier to file a regulatory occurrence report but not report the event to the Air Accidents Investigation Branch.
Heathrow’s runways have foreign-object detection capabilities but the panel – probably lost on landing – fell into grass to the south of 27L about 600m from the threshold, outside of the detection area.
The aircraft involved, G-UNET, was the first to be introduced by One Air, a newly-established UK freight carrier which had begun customer operations about six months beforehand.
Boeing provided the UK inquiry with information on 10 instances of panel detachment, but the manufacturer’s analysis had considered such events to have a low probability of causing damage or injury, and that the primary concern was runway debris – mitigated by airport measures and aircraft design standards.
