Investigation Summary
The incident highlighted a unique and hazardous design characteristic of the Saab 2000's flight control system. Unlike most modern airliners, the Saab 2000's autopilot did not automatically disengage when the pilot applied force to the control column. During the event, the captain applied significant nose-up pressure, but the autopilot, programmed to maintain 2,000 feet, countered this by trimming the horizontal stabilizer to its full nose-down limit. Because the pitch trim had more authority than the elevators at high speeds, the pilots were unable to stop the descent despite pulling the control column to its aft limit. The situation was further complicated by the captain's prior experience on the Saab 340, where lightning strikes typically caused autopilot disengagement, leading to a false assumption that he was in manual control. The dive was only arrested when invalid data from an Air Data Computer (ADC) triggered a system-level autopilot disconnect, returning full control to the crew just seconds before impact.
Final Conclusions
The UK Air Accidents Investigation Branch (AAIB) concluded that the primary cause was the crew's failure to recognize that the autopilot remained engaged after the lightning strike. This led to a 'dual control' conflict where the autopilot's nose-down trim authority exceeded the pilots' nose-up elevator authority. The investigation identified 'cognitive tunnelling' as the reason the crew missed visual and aural mistrim warnings. The AAIB issued five safety recommendations, specifically targeting the redesign of autopilot systems that allow opposite trimming against pilot inputs and those that do not disengage upon manual override.
Photographic Evidence (1)
Video Analysis
Struck By Lightning (Loganair Flight 6780) - DISASTER AVERTED — A detailed breakdown of how a lightning strike triggered a near-fatal conflict between a Saab 2000's autopilot and its flight crew over the North Sea.
If playback is blocked, the owner has disabled embedding — use the link above.
Airframe & Maintenance
Crew Experience
Captain
Transitioned from Saab 340 to Saab 2000 in August 2014.
First Officer
Qualified on Saab 2000 in May 2014.
Systems & Failure Modes
Autopilot (AP)
On the Saab 2000, the AP did not disengage when pilots moved the control column or used the main pitch trim switches, leading to a conflict where the system trimmed against the pilot.
Pitch Trim
The autopilot's nose-down trim authority was greater than the pilots' manual nose-up elevator authority at high speeds, making the dive unrecoverable while the AP was active.
Air Data Computer (ADC)
Invalid data from the ADC, likely resulting from the extreme flight conditions or the lightning strike, eventually triggered a system-level autopilot disconnect, which allowed the crew to recover.
Interesting Facts
- 01The Saab 2000 was the only aircraft of 22 surveyed types where the autopilot would not disengage when the pilot applied override force to the column.
- 02The aircraft reached a maximum speed of 330 knots, significantly exceeding the Vmo of 250 knots.
- 03The minimum height reached during the dive was approximately 1,100 feet above sea level.
- 04The autopilot disengaged only because it received invalid data from an Air Data Computer, not because of pilot action.
- 05The captain had 143 hours of experience on the Saab 2000 at the time of the incident.
- 06The Cockpit Voice Recorder (CVR) data for the start of the event was overwritten because the device only had a 30-minute recording loop.
Safety Actions & Advisories
Autopilot Design Review
The AAIB recommended that EASA and the FAA review the design of autopilot systems to ensure they disengage when a pilot applies a significant override force.
Saab 2000 Operations Newsletter
The manufacturer issued Operations Newsletter No. 6 to clarify autopilot behavior and override procedures for all Saab 2000 operators.
Location
APPROXIMATE POSITION · AIRPORT LEVEL · Coordinates are the estimate published in the entered by an editor. The ring shows the accuracy the record supports, not the point of impact.