Eight years after a Swiss Saab 2000 was written off while landing at a German air base, investigators have detailed the extraordinary circumstances that led the crew to divert five times to escape surrounding storms.
Forced to land by rapidly diminishing fuel reserves - the Saab had just 420kg (925lb) in its tanks - it struck a 0.7m (2.3ft) earthen berm across a restricted part of the runway at Werneuchen, snapping off its undercarriage.
While the accident in July 2002 was serious, it was non-fatal, and German investigation agency BFU lowered its priority to concentrate on the mid-air collision over Lake Constance, which had taken place nine days earlier.
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BFU says that this was partly responsible for the long time-lapse to produce its conclusions, but adds: "The work on this report was possibly a little more than with the [collision]. There were a lot of facets we had to investigate - it was not easy to do this."
Initially bound for Hamburg, the crew, with a 600kg fuel reserve in case of storm delays, aborted the first approach and after holding for about 15min opted to divert to Hanover.
Critically, the BFU says this first diversion was made without using available information and "without first obtaining a comprehensive weather overview of those airfields within range and as yet unaffected by the front".
As the pilots manoeuvred to avoid thunderstorms at Hanover, the information on their weather radar prompted them to make a second diversion to Berlin Tegel 20min later.
Although the flight was operating at low altitude - below 5,000ft (1,520m) - during the diversions, BFU says this did not lead to higher fuel consumption.
But a low-fuel warning, indicating just 40min flight time remaining, sounded as the Saab vectored for Berlin, having been airborne for 2h 9min. Ten minutes later the aircraft was forced to find another destination as storms closed on the German capital, and air traffic control suggested Eberswalde-Finow, 27nm (50km) away.
En route to Eberswalde, with the flight being treated as an emergency case, the pilots abandoned this course owing to the weather, and briefly turned towards Neubrandenburg - 46nm away - before similarly scrapping this plan.
Controllers suggested Werneuchen, 20nm distant. Owing to the fuel situation the crew did not visually inspect the runway from the air. The pilots could not see the berm blocking off the western section of the 2,400m runway on approach, and closure markings were too unclear to be made out. After 2h 33min of flight the Saab hit the berm and slid 350m before coming to rest.
Given the circumstances of the crash, the BFU has not made any safety recommendations. The investigator in charge of the inquiry says the situation was "most interesting", but adds: "I don't believe the accident at Werneuchen is something that will happen again."
Source: Flight International
