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Aviation History
1990
1990 - 0022.PDF
NEWS ANALYSIS SOLVING THE LOCKERBIE The main wreckage reassembly of the port, forward lower fuselage On 21 December, 1988, Pan Am's night PA 103, a Boeing 747-100, was destroyed by a ter rorist bomb at 31,000ft over southern Scotland. All 259 pas sengers and crew on board were killed, as were 11 persons on the ground when the bulk of the Boeing 747's wreckage landed in the small town of Lockerbie. Within days it was apparent that the cause of the crash was an improvised explosive device (1ED) and not a fatigue failure, but the police faced a daunting task in bringing to book those responsible for planting the weapon. The first priority on the night of the crash was to save life and restrict the spread of the fires in the town. Recovery of bodies started the next day, and police and the military began the im mense task of locating, marking and logging the wreckage which fell in a large swathe, covering some 2,900km2, with some lighter items drifting as far away as the east coast. The aircraft, N739PA, was the 15th 747 built, having entered service in 1970 and logged 72.000h and 16,500 flight cyles before the crash. The aircraft had received section 41 rein forcing and also had a beefed-up main deck floor and deck mountings as part of the USA's Civil Reserve Air Fleet modifica tion programme. The explosion ripped out a large section of the cargo bay hull, and debris is likely to have been ingested by both port en gines. Simultaneously, the air craft was subjected to an explosive decompression as hull pressure vented. The breakup was immediate and catastrophic; the cockpit section was found some 5km short of the Lockerbie impact site, where the centre section wing and engines im pacted. The lighter tail assembly was also some distance away. Investigator Mick Charles, from the Department of Transport's Aircraft Accidents Investigation Branch (AAIB) cannot comment yet on the exact breakup se quence: "The report will be re leased next year and, until then, I am legally bound not to com ment on the interpretation of the post-explosion breakup se quence", he says. Following initial examination in the field, thousands of pieces of wreckage were recovered and taken to the Army's Central Ammunition Depot at Longtown, 37km south of Lockerbie. Initially, the wreck age was laid out on the floor in a flatplan corresponding to the aircraft layout. From this it was pos sible for the AAIB to deter mine the loca tion of the bomb and to form an initial view of the se quence of disintegration of the aircraft. The flat layout neverthe less made it difficult to analyse in detail the remaining structure and to determine why the explo sion should have resulted in the catastrophic breakup of the aircraft. A portion of the front fuselage, including the forward cargo hold area, was transported to the AAIB's hanger at Farnborough, where it was re-assembled in three-dimensional form on a scaffolding framework. The larg est reconstructed section is 20m long, 8m high and 8m wide, and shows the "petalling" effect of the aircraft skin produced by the explosion. The tailplane was also reconstructed to assess the impact damage inflicted on it by wreckage shed by the disintegration of the forward fuselage area. The forward upper deck and roof area of the aircraft was built alongside the main fuselage area because the hangar was too low to accommodate it in its natural position. The container which con tained the IED also exhibited obvious signs of explosive deformation before bursting outwards. The container was minutely examined by a Royal Armament Research and Development Establishment forensic science team led by Alan Feraday, who specialises in IEDs. Feraday's team found a small charred fragment of a printed circuit board lodged in the con tainer's framework. This was traced back to a type used by Toshiba in its model 8016 radio/ cassette player. A fragment of charred loudspeaker grill con firmed the suspicion that the radio housed the IED. Gas spectrometry on traces of explosive residue in the con tainer showed the IED to have contained Semtex H, an odourless and powerful commer cial plastic explosive favoured by terrorists. A combined timer/ barostatic fuze was used. Several internally scorched fragments of suitcase were recovered, and these were identified as being part of a Samsonite case wich contained the Toshiba radio. Test explosions were carried out on similar cargo containers and from these it was established that the suitcase containing the IED was stacked on top of the bottom layer of baggage in the container. "The wreckage fell in a large swathe, covering some 2,900km2" tri I/~_UT IMTPPMATTONAI ~\-Q lanuarv 1990
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