A fatal plane crash that killed a 44-year-old pilot at Maitland two years ago was most likely caused by a damaged oil cooler that starved the engine of oil leading to a loss of power and eventual engine stall, an Australian Transport Safety Bureau investigation has found.
In a statement released Monday, the transport safety authority revealed that the required, and the majority of the recommended build inspections of the amateur-built plane were not conducted prior to the crash, and that the oversight had not been detected when the plane was issued with a certificate of airworthiness that permitted the fatal flight to take off.
While investigators admitted that the inspections would probably not have found the damaged oil cooler that most likely sparked the series of events that caused the crash, they might have identified that the engine's oil supply hose was in poor condition, and would have had the opportunity to improve the aircraft's overall build quality.
The ATSB's transport safety director, Stuart Macleod, said the crash highlighted the importance of adhering to the design specifications and good engineering practices when building experimental aircraft.
Witnesses to the moment the privately-constructed Osprey 2 plane plummeted into a West-Maitland paddock on the morning of May 17, 2020 said the plane was flying "low and slow" with a stationary propeller on approach to a runway it would never reach.
The ATSB found that the engine lost power and aerodynamically stalled in the final moments before the crash, at an altitude from which the aircraft could not be recovered.
Its pilot, 44-year-old Andy Shepherd, who Police described at the time as "very experienced", had taken off under a special certificate of airworthiness allowing the plane to be flight tested.
The planned journey involved flying to 3000 ft to conduct testing over the Maitland airfield, but just minutes into the climb, as Mr Shepherd passed through 2400 ft, he was advised from the ground that white smoke was coming from the engine.
The transport safety authority said Mr Shepherd then radioed his plan to land on runway 23 at Maitland Airport, but during descent turned to join the reciprocal runway 05. As the aircraft turned onto the base leg of the circuit, the engine failed completely, and Mr Shepherd attempted to conduct a forced landing on the closer runway 08.
"During the final stage of the glide approach, the aircraft was observed to abruptly roll, pitch down and collide with the ground," Mr Macleod said.
Mr Shepherd was fatally injured, and the aircraft was destroyed.
Video from the cockpit showed that the plane's airspeed decreased to between 60 and 65 kt prior to the roll, and examination of the scene confirmed the aircraft hit the ground with low forward airspeed while rolling to the left, consistent with an aerodynamic stall.
Investigators found the use of a damaged engine oil cooler fitting, which was not compatible with the fitted oil hose, most likely resulted in the hose disconnecting from the oil cooler during the climb. The extended airborne duration, and need for increased engine power, resulted in the engine failing due to oil starvation, the ATSB said.
"A partial engine failure often precedes a complete loss of power," Mr Macleod said, adding that a partial loss of power can often be a more complex situation for a pilot of deal with than a complete power loss.
"Pilots can be strongly influenced by the fact the engine is still providing some power, and often by the strong desire to return the aircraft to the runway to avoid damaging the aircraft in a forced landing," he said.
"In this case the pilot's decision to change from runway 23 to runway 05 meant the aircraft needed to stay airborne longer, necessitating more power from the damaged engine to maintain height."
Mr Shepherd has been remembered as a skilled and experienced pilot and a highly regarded aeronautical engineer.
His aircraft crashed into a paddock between Denton Close and Beacon Hill Road about 10.15am on May 17, 2020, as residents of the area rushed to help. He was pulled from the plane and witnesses performed CPR until paramedics arrived, but he could not be saved.
