Factual Information
On 5 August 2022, at approximately 14:30 local time, an Aquila AT01, registration OE-CYY, was involved in an accident near Lesce Airfield (LJBL), Slovenia. The aircraft, a two-seat single-engine airplane manufactured by Aquila Aviation International GmbH, was owned and operated by Austrian Aviation Training GmbH. The flight was a technical ferry flight from Lesce to the home base in Graz, Austria, following maintenance.
Sequence of Events
The pilot, accompanied by one passenger, took off from Lesce at 14:20 local time after a pre-flight inspection and receipt of a Certificate of Release to Service from the maintenance organization. After takeoff, the pilot performed a touch-and-go landing to check engine operation, then continued the flight as planned. During climb at an altitude of 3200 feet above mean sea level, the engine suddenly failed. The pilot turned the aircraft back toward the departure airfield and informed the air traffic controller of the engine problem and intention to return. Shortly thereafter, the pilot declared an emergency and performed a forced landing on a section of a nearby road.
Aircraft Damage and Injuries
The aircraft sustained major structural damage to the wings, fuselage, and landing gear. Equipment was not damaged. The pilot and passenger sustained minor or no injuries, as reported in the final report.
Investigation Findings
The investigation determined that the engine failure was caused by a lack of fuel in the tanks, leading to an interruption of fuel flow to the engine. The fuel quantity indicator in the cockpit was found to have shown an incorrect reading, which misled the pilot regarding the actual fuel quantity. The aircraft had been refueled prior to the flight, but the amount of fuel on board was insufficient for the intended flight.
The fuel selector was found in the correct position, and manual fuel measurement using a "deep-stick" was possible. The fuel indicator on the instrument panel was of the type Westach (P/N 2840-122), and testing of a comparable instrument on another general aviation aircraft revealed similar indication errors under certain conditions.
Probable Cause
The direct cause was insufficient fuel in the tanks, resulting in fuel supply interruption to the engine. The indirect cause was an incorrect fuel quantity indication on the cockpit instrument, which misled the pilot about the actual fuel level.