page_title: Partnair Flight 394
section_title: Investigation
hierarchical_section_title: Partnair Flight 394 / Investigation
caption_attribution_description: English: Partnair LN-PAA wreckage
context_page_description: Partnair Flight 394 was a chartered flight which crashed on 8 September 1989 off the coast of Denmark, 18 km north of Hirtshals. All 50 passengers and 5 crew members on board the aircraft died, and it is the deadliest aviation disaster in Denmark. The crash was caused by use of counterfeit aircraft parts in repairs and maintenance.
context_section_description: Accident Investigation Board Norway (AIBN) investigated the disaster and were able to recover 50 of the 55 bodies before sending them through autopsies in Denmark. Investigators used side-scan sonar to plot positions of wreckage. The pieces had settled over an area 2 kilometres (1.2 mi) wide, leading the investigators to believe that the aircraft disintegrated in the air. Luckily, 90% of the aircraft could be reconstructed.
  In an accident flight, the cockpit voice recorder (CVR) can usually record its final minutes. In the Partnair crash, however, it had recorded the start of the flight and stopped shortly before the aircraft took off. From the maintenance records investigators found that, 10 years prior to the accident flight, the cockpit voice recorder's power supply had been re-wired to connect to the aircraft's generator instead of the aircraft's battery if full power was applied for takeoff. As the generator was inoperative on this flight, power to the CVR shut off as the aircraft took off.
  Some initial speculation stated that explosives brought down Flight 394. Indeed, in December 1988, a bomb had brought down Pan Am Flight 103. In addition, Norwegian Prime Minister Gro Harlem Brundtland had used that particular Partnair aircraft on her campaign trips. The Norwegian press believed that the crash was an assassination attempt. Witnesses of the crash said that they heard a loud noise as they saw the aircraft fall. The fact that the aircraft had disintegrated in the air gave credibility to the bomb theory. The speculation in the press later included a scenario where the plane had been shot down, possibly by the NATO war exercise "Operation Sharp Spear," which took place on the day of the accident flight near the flight path, as investigators had found small traces of high explosives on parts recovered from the sea bed. However, investigators found that the residue was not from a bomb or a warhead, as there was not enough of it present. Finn Heimdal, an AIBN investigator, said in an interview that the residue appeared to be more like a contamination than any other possibility. The sea had old munitions as many battles had been fought off the coast of Denmark. Investigators concluded that the aircraft pieces acquired residue from the bottom of the sea or that the traces of explosives were accumulated from contamination before the accident or due to storage.
  Metallurgist Terry Heaslip of the Canadian company Accident Investigation and Research Inc. examined the aircraft skin from the tail and found signs of overheating, specifically that the skin had been repeatedly flexed, through a phenomenon known as flutter. This caused investigators to further scrutinize the tail of the aircraft. Furthermore, the investigation team found that the Auxiliary Power Unit (APU), which was in the tail, generated heat which melted certain plastic parts, indicating that the APU was operating during the flight even though it normally would not be. The mechanic who had inspected the aircraft on the day of the accident flight told the investigators that one of the aircraft's two main generators had failed and that he was not able to repair the faulty generator. The investigators discovered that the pilots had noted in the flight log that they would operate the APU throughout the flight, since two power sources are required for flight. They also discovered that the front APU mount was broken, which allowed it to vibrate excessively.
  The two shroud doors on the aircraft tail were not present in the recovery. They were constructed with an aluminium honeycomb liner, and aluminium's reflective properties allowed the doors to appear on radar when floating free. This led the AIBN to conclude that the unidentified objects tracked at a high altitude by Swedish radar for 38 minutes were likely the shroud doors, which had separated from the aircraft tail. From this, the AIBN found that the tail failed at 22,000 feet. If the rudder moved in a violent manner, the weights behind the doors would also move violently and hit the shroud doors. Therefore, the rud
caption: Reconstruction of the wreckage
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