Jumbo Recovery

A Boeing 747 Jumbo-jet crashed in bad weather whilst trying to land at Hong Kong's international airport on the 4^th November 1993. Miraculously, there were no fatalities nor even any serious injuries when the jet overshot the runway and ploughed into the harbour water.

The subsequent salvage operation, unprecedented in flying history, became a race against time. This was mainly because the presence of the Jumbo was preventing the operations on one runway and restricting those on another. A large number of heavy-lift buoyancy bags were suddenly needed to carry out a rapid recovery. Where on earth could such a large number be acquired at such short notice?

The Hong Kong Salvage and Towage Co Ltd contacted Seaflex on the Isle of Wight to provide the desperately needed lifting equipment. The order arrived on Mark Board's desk at Seaflex at 1535hours and by 1930 hours the same evening, 304 tons of fully enclosed lift, packed for air freight on pallets, were on their way to Heathrow airport.

The first job, to help get the airport operational again, was to remove the aircraft's high tail fin. It was found impractical and unsafe to unbolt the fin or to cut it off with oxy-acetylene. So explosives experts from the Royal Hong Kong Police were quickly enlisted to blast the fin away using linear shaped charges. These controlled explosions were to be very carefully planned and executed in order to minimize damage to the remaining structure and to avoid prejudicing the subsequent accident investigation. Following the successful removal of the tail fin, the airport operations were returned to near normal within 6 hours of the crash.

Assessment

The next urgent job was to stabilize the aircraft in preparation for the recovery operation. Divers were employed to carry out the damage assessment in zero visibility conditions. In order to help the divers to work effectively in the nil-visibility conditions, they were given special training and familiarization on an operational 747. Once back in the harbour, the divers found that one of the four engines had dropped off completely and another was hanging precariously from its wing. They later found the lost engine in the total darkness on the sea bed when a search diver unwittingly swam inside it (fortunately it was stopped at the time and the diver was unharmed). The landing gear, which was deployed, appeared intact and no major structural damage was found on the aircraft. There was some skin damage, and this was mainly around the underside of the nose. The aircraft was effectively still floating but the nose was grinding on the rocks in shallow water. The conclusion of the insurance underwriters was that the aircraft was beyond repair. It was a total constructive loss and would have to be scrapped after recovery.

Remarkably, the aircraft's pressure hull was still almost completely watertight. It did not take very long to effect the few additional seals to enable the hull to be pumped dry. The stability of the aircraft was ultimately guaranteed when divers attached the Seaflex lift bags on both sides of the fuselage and under both wings. Further lightening of the hull was achieved by the removal of fuel, cargo, seating and the engine which was only loosely connected.

Undercarriage

The lift of the remaining 190 tonnes was carried out using two floating sheer-legs which were securely lashed together. The larger one, the Proteus and the largest in Hong Kong harbour, took the main load. Special strops were connected to the wing, main undercarriage trunion lifting points. These were attached via a 5 tonne, 11m spreader bar to the Proteus' main lifting hook. The smaller lift barge took the weight of the nose of the aircraft using a purpose-built body sling.

Three tugs, on ahead and two astern, towed the barges, together with the under-slung Jumbo, into the harbour. The whole towing operation took only 40 minutes. The aircraft was then lowered onto a taxi-way bridge section, the weight being taken by its main undercarriage. The nose undercarriage was found to be insecure so a special nose trailer element which formed part of the airport's Disabled Aircraft Recovery Transport System ("DARTS") was brought in to take it's weight. The whole aircraft was then towed away for detailed inspection and investigation.

It is a measure of the great efficiency of the salvage operation that the entire operation was completed within 14 days of the original incident. The operation also serves to emphasize the international nature of such complex tasks and the major significance of UK expertise and products, such as those of Seaflex, in this important role.