What happened
On September 8, 1989, the aircraft LN-PAA, a Boeing 737 operated by Partnair, was scheduled for a charter flight to Hamburg. The departure was delayed by nearly one hour because of financial disputes between the operator and the Norwegian Civil Aviation Administration and a catering provider. During the days leading up to the flight, the aircraft had encountered issues with its left AC power system; although an AC generator was replaced, the underlying malfunction persisted, leading the crew to rely on the APU generator for that system during the flight.
The aircraft departed at 15:59:50 hrs. After climbing through FL 180, the crew received a suggestion from Oslo ACC to adjust their heading by 100 degrees to the right due to strong westerly winds. As the flight approached Danish airspace, the crew was instructed to transition contact to Copenhagen ACC. By 16:23 hrs, the aircraft had reached its cruising altitude of FL220 and successfully established communication with Copenhagen controllers.
Shortly after this final radio transmission, radar operators at Copenhagen ACC noticed the aircraft performing an unexpected right turn before it vanished from radar coverage. Despite repeated attempts by air traffic services to re-establish contact, the aircraft could not be reached. Search and rescue operations were initiated by authorities in both Denmark and Norway, but it was later confirmed that a major accident had occurred. There were 55 fatalities and 0 survivors.
Findings
The investigation determined that the aircraft suffered a total loss of control following the destruction of primary control surfaces in the tail section. This failure was triggered by aeroelastic oscillations stemming from improper clearances in the vertical stabilizer attachments to the fuselage. The structural integrity was compromised because the pins and sleeves used in these joints were of inferior quality, failing to meet required hardness and tensile strength standards. Furthermore, sub-standard maintenance procedures were used during the installation and inspection of these components. Undamped oscillations within the elevator also played a role in the eventual structural failure of the empennage.