What happened
On February 8, 1988, a Fairchild SA 227-AC, Metro 111, registration D-CABB, operated by Nürnberger Flugdienst, was performing a scheduled passenger flight from Hannover to Düsseldorf. The flight was carrying 19 passengers and 2 crew members. As the aircraft was approximately 7 nautical miles from the runway threshold on final approach, it encountered severe weather conditions including snow, hail, and lightning.
During the approach, the aircraft was struck by lightning, which resulted in a total failure of the electrical power supply. This failure caused the loss of cockpit and instrument lighting and rendered the operation of the flaps and trim tabs impossible. Following the strike, the aircraft entered an uncontrolled descent. For approximately two minutes, the aircraft flew through a thunderstorm environment. Witnesses on the ground observed the aircraft emerging from the clouds in a steep descent, attempting to climb to avoid terrain, before the aircraft broke up in mid-air at approximately 07:58 local time. The aircraft struck the north side of the Ruhr river near Kettwig. All 21 people on board were killed, and the aircraft was destroyed.
The investigation
The BFU investigation examined the aircraft wreckage, engine and propeller components, and the electrical system. Investigators analyzed the cockpit voice recorder (CVR) and flight data recorder (FDR) to reconstruct the sequence of events. The investigation also reviewed meteorological reports, radar data, and witness accounts. Microscopic analysis of electrical components, specifically a high-voltage-damaged diode, confirmed that the lightning strike caused significant damage to the aircraft's electrical network. The investigation also reviewed the crew's flight preparation, including their review of weather information and the aircraft's maintenance and equipment status.