What happened
On September 29, 2002, a twin-engine Cessna 551 Citation departed Stuttgart for Basel-Mulhouse under IFR conditions. During the approach to Basel, the crew was informed of low visibility, with runway visual range (RVR) values between 200 and 300 meters and a cloud ceiling below 100 feet. Despite the aircraft only being authorized for CAT I approaches—which require a minimum RVR of 600 meters—the crew continued the approach.
At approximately 09:34, the aircraft struck the ground on a grassy area roughly 300 meters before the threshold of runway 16 and about 40 meters north of the approach centerline. The impact caused significant structural damage, including the breakage of an antenna and vital components of the left main landing gear. The crew initiated a missed approach and subsequently decided to return to Stuttgart, noting that the weather was below minimums.
Upon arriving in Stuttgart, the crew reported that the left main landing gear had failed to lock in the down position. To mitigate risks, the pilot elected to land on a grass strip adjacent to the runway, which had been prepared with water by the airport fire service. The aircraft landed at 11:46 with the right main gear and nose gear extended, but the left main gear partially extended. The aircraft remained on course during the rollout but veered slightly to the right just before coming to a halt. There were no injuries to the two crew members.
The investigation
The BFU examined the aircraft's flight path, radar data, and the wreckage found at the Basel site. Investigators recovered pieces of the left main landing gear, parts of the right brake, and the broken antenna from the field near Basel. Analysis of the aircraft's landing gear mechanism revealed that the gear was actually extended and locked at the time of the ground contact in Basel, contradicting the crew's report of a malfunction. The investigation also reviewed the operator's certifications, noting they were only authorized for CAT I operations, and that the aircraft was not equipped for CAT III approaches.