What happened
On the evening of 7 February 2008, a pilot was conducting a solo navigation exercise from Gothenburg City Airport to obtain a night-time endorsement. Approximately ten minutes into the flight, while operating at 1,500 feet, the engine of the DA 40D, registration SE-LTF, suddenly stopped.
With limited time and visibility constraints, the pilot attempted emergency restart procedures without success. Seeking the only available illuminated area, the pilot opted to land on the E45, a four-lane motorway. During the approach, the aircraft's right wing struck a lighting column. Upon touchdown, the aircraft collided with a private car, causing damage to the vehicle's windscreen. The aircraft then slid off the roadway into the grass, where it struck a second lighting column and caused debris to strike another passing vehicle. The pilot escaped the wreckage without injury, and no occupants in the involved cars were harmed.
The investigation
Investigators from the Swedish Accident Investigation Board (SHK) examined the wreckage and the engine's digital control unit (FADEC). The data revealed that fuel pressure downstream of the high-pressure pump had dropped to near zero at the moment of the engine failure.
Technical analysis of the fuel system identified a break in the outlet pipe from the high-pressure pump. Microscopic examination of the fractured surface revealed approximately 60 beach marks, indicating that the metal had succumbed to fatigue. The investigation also noted that this specific component failure had occurred in at least three other aircraft prior to this event.
Findings
- The engine failure was caused by the fatigue failure of a fuel pipe due to a design deficiency.
- The pipe, which was only secured by collar nuts at its ends, was subjected to vibration-induced stresses.
- The risk of fuel pipe breakage was known to the engine manufacturer and EASA prior to the accident.
- The pilot's decision to land on the motorway was a reasonable choice given the lack of other illuminated landing sites in the darkness.
Safety action
Following the investigation, SHK recommended that EASA re-evaluate its airworthiness assessment criteria to ensure that aircraft with known, serious design flaws are not permitted to continue flying.