What happened
On May 26, 2000, a Piper PA31-350 Navajo Chieftain, registration HB-LTC, experienced a catastrophic dual engine failure shortly after takeoff from Zurich Airport. The aircraft, which had arrived from Béziers, France, with seven passengers the previous day, was being operated for a flight to Geneva.
During the refueling process on the day of the accident, the aircraft was incorrectly supplied with JET A-1 kerosene rather than the required AVGAS 100LL. As the pilot attempted to execute a turn following takeoff from runway 28, both piston engines failed, causing the aircraft to strike obstacles and crash. The pilot sustained fatal injuries, and the aircraft was destroyed.
The investigation
The Swiss Transportation Safety Investigation Board (SUST) examined the refueling procedures, the fuel quality, and the mechanical state of the aircraft. The investigation focused on why the incorrect fuel type was introduced into the tanks and why the error went undetected by both the ground crew and the pilot. Investigators also reviewed the technical compatibility of the refueling equipment and the training standards of the fueling personnel.
Findings
Multiple contributing factors led to the misfueling of the aircraft:
- A misunderstanding occurred during the initial fuel order.
- The fueling technician failed to recognize the specific quality markings on the aircraft.
- The technician did not notice that the aircraft was equipped with piston engines.
- The pilot failed to identify the fuel type indicated on the tanker truck.
- The pilot did not notice the error on the fuel delivery receipt.
Several systemic issues facilitated the error. The nozzle on the refueling equipment had an outer diameter that allowed it to fit into the aircraft's fuel ports. Furthermore, the investigation found that the training and knowledge levels of the fueling staff were insufficient. At the time, there were no specific regulations from the Federal Office of Civil Aviation regarding the standardization of fueling nozzle dimensions, fuel port markings, or mandatory training for refueling personnel.
Additional factors that worsened the outcome included the pilot's decision to perform a turn that led to the collision with obstacles, and a failure in the shoulder harness restraint mechanism.
Safety action
Following the accident, several safety improvements were implemented:
- The fueling company equipped JET A-1 tankers with nozzles featuring a larger outer diameter to prevent them from entering smaller fuel ports.
- A brake interlock system was introduced to ensure that smaller, specialized nozzles are properly stowed before the tanker can move.
- The Federal Office of Civil Aviation updated regulations to mandate color-coded identification for fuel types: Red for AVGAS, Black for JET A-1, and Green for MOGAS.