What happened
On June 29, 2014, a Diamond DA-20-C1 aircraft, registration TF-KFB, was conducting a flight training mission from Keflavík Airport. The flight crew, consisting of a flight instructor and a student pilot, had planned a flight to Hellu, but due to the aircraft having only roughly half a tank of fuel, the instructor decided to shorten the mission to practice touch-and-go landings at Selfoss and Sandskeið.
During the flight, the crew noted a discrepancy between the fuel level indicated on the cockpit gauge and the manual measurement taken with a dipstick prior to takeoff. Despite this observation, they continued the flight. While flying near Kúagerði, the engine began to lose power and eventually failed. The instructor took control of the aircraft and attempted an emergency landing at the Vatnsleysuströnd golf course.
During the landing sequence, the aircraft struck a depression in the golf course fairway, causing it to bounce and eventually flip onto its back. The impact caused the cockpit canopy to shatter. The instructor sustained minor injuries to the head, while the student pilot was uninjured. Both crew members were able to egress the overturned aircraft safely.
The investigation
The RNSA investigation focused on the fuel levels and the sequence of events leading to the engine failure. Investigators examined the aircraft's fuel system and found that no fuel remained in the tank at the crash site. Technical examinations of the Diamond DA-20-C1 fuel system and engine revealed no mechanical defects; the engine functioned normally when tested with fresh fuel.
Investigators also analyzed the fuel consumption rates using various methods, including flight logs and manufacturer specifications. The investigation confirmed that the engine failure was a direct result of fuel exhaustion. The RNSA also examined the pre-flight procedures used by the flight school, noting that the instructor had arrived late, which impacted the thoroughness of the fuel verification process.
Findings
- The primary cause of the accident was fuel exhaustion.
- The crew misidentified the fuel level on the dipstick, likely misinterpreting the marking for unusable fuel as the first quarter-tank mark. This led them to believe the tank was more than half full when it was actually closer to one-quarter full.
- Expectation bias played a role, as the instructor's belief that the student had reported a half-full tank influenced his interpretation of the fuel gauge.
- The crew chose to disregard the cockpit fuel gauge discrepancy in favor of the manual dipstick reading, which was inaccurate.
- The instructor's observation of the fuel level from a distance (from the right seat) likely contributed to the misreading of the dipstick.