What happened
On April 6, 2000, at 19:35 local time, a Cessna 172-N, registration EC-EOT, was performing a flight training mission from Cuatro Vientos airport to Son Bonet airport in the Balearic Islands. The aircraft was operated as a general aviation instruction flight with a crew consisting of a commercial pilot and two student pilots.
During the flight, the pilot noticed a discrepancy between the fuel level readings in the two tanks. After performing a manual calculation, the crew determined they had sufficient fuel to reach their destination or an alternate airport. However, as the aircraft approached the coast of Mallorca, the fuel gauge for the right tank indicated it was empty. Despite this, the crew decided not to divert to an alternative airfield.
While near Portals Nous, the engine began to fail and eventually stopped, causing the aircraft to lose altitude. The crew notified Palma de Mallorca tower of their engine problems and their uncertain ability to reach Son Bonet. After passing over Son Moix at 300 feet, the aircraft performed a forced landing in the Can Valero industrial estate, near an electrical transformer station. The aircraft struck treetops and impacted the ground nose-first, causing significant damage to the engine mount, firewall, and landing gear. The three occupants sustained minor injuries and required two days of hospitalization.
The investigation
The investigation examined the aircraft's maintenance history, which showed a recent 200-hour inspection completed one week prior to the accident. No fuel leaks were found in the tanks, lines, or engine during the post-crash inspection. Upon disassembly of the wings, the tanks were found to be empty, with only a small amount of fuel remaining in the carburetor.
A review of the company's fuel management policy revealed a discrepancy between the flight plan's declared endurance and the required endurance according to the operator's manual. While the crew's calculations were theoretically sufficient, the investigation found that the actual flight time was 18 minutes longer than estimated due to a slight headwind or route deviation.
Findings
- The primary cause of the accident was fuel exhaustion.
- The crew failed to visually verify the actual fuel quantity in the tanks before departure, likely operating under the incorrect assumption that the tanks were full.
- The crew relied on unreliable fuel gauges to estimate remaining fuel, despite being aware that the gauges provided inaccurate readings.
- The crew decided to continue the flight toward the destination even after the right tank indicated it was empty, rather than diverting to an alternative airfield.