The emergency landing of a light aircraft on a beach in Wexford three-and-a-half years ago was probably due to separate interruptions to the fuel supply of both engines while operating with low fuel levels, an investigation has concluded.
A pilot and three passengers were on board the Partenavia P68 Victor aircraft when it made a forced landing on a beach near Carnsore Point, Co Wexford on 23 September 2021.
The incident occurred after the pilot encountered problems with both engines a few minutes apart as a gauge indicated there was a sudden, abnormal loss of fuel.
The French–registered twin-engine aircraft with a group of researchers from University College Cork on board had left Waterford Airport to record sightings of various marine wildlife.
A report by the Air Accident Investigation Unit concluded the probable cause of the incident was interruptions to the fuel supply of each engine while operating at or below a quarter of the aircraft's fuel tank capacity.
AAIU inspectors said a contributory factor was a lack of clarity in the aircraft’s flight manual limitations regarding operations with fuel tanks less than a quarter full.
They claimed the configuration of the fuel selector panel - which allows the pilot to select which fuel tank feeds which engine - was also potentially misleading and its operation was "not intuitive."
The AAIU report observed that an in-flight loss of power from both engines in a twin-engine aircraft is "a very uncommon occurrence."
The pilot and one of the passengers sustained serious injuries, while the aircraft was destroyed with part of the wreckage washed away by the tide.
The other two passengers sustained minor injuries, despite their seatbelt brackets becoming detached from the aircraft floor panels as a result of the forced landing.
One said he was thrown diagonally across the cabin and into the back of the pilot’s seat by the impact.
The plan for the flight was to fly at low altitude along 16 predefined survey lines - each about 45km - along the south coast between Tramore and Carnsore Point.
When the planned survey was completed after four-and-a-half hours flying, the pilot determined that there was enough fuel to complete two more survey lines before returning to Waterford Airport.
The AAIU report revealed that the right engine stopped suddenly shortly after the aircraft started the final additional survey line when it was travelling at a speed of 105 knots and at a height of 300ft.
The pilot reported that the aircraft then struggled to climb while operating only on the left engine.
It then experienced a significant loss of power before recovering and losing power again in a sequence which was repeated several times.
The pilot carried out a forced landing on a beach after the left engine lost power again as it approached land.
The nose of the aircraft impacted with the loose shale surface of the beach which resulted in substantial structural damage to the forward cabin area.
The pilot reported that the left engine ran briefly at full power while the aircraft was on the beach before he shut it down.
He exited the aircraft through the windscreen which had broken on impact, while the passengers exited by the door.
The pilot and front seat passenger who sustained serious injuries were airlifted to hospital by an Irish Coast Guard helicopter, while the other two passengers were brought to hospital by ambulance.
The pilot told AAIU inspectors that he estimated there was approximately one hour and 45 minutes of fuel left in the tanks at the start of the extra two survey lines.
However, he said the right engine stopped a few minutes into the additional part of the flight after the fuel gauge began to show an abnormally low indication which led him to suspect there was a fuel leak.
The report revealed that a loose connection which had caused a similar problem with the same engine during a flight five days earlier between Rennes in France and Waterford was found to be secure.
The pilot reported that the left engine suddenly lost power when there was still close to a quarter tank of fuel remaining after he had declared a Mayday and informed air traffic controllers that he was heading back directly to Waterford Airport.
The passengers said they knew their role was to stay calm and prepare for either a ditching or forced landing including ensuring their immersion suits were properly fastened.
An inspection of the wreckage found no mechanical problems with either aircraft engine that could have caused the forced landing.
The remaining fuel was drained from the aircraft’s two tanks and measured a total of 74 litres.
AAIU inspectors found pre-existing damage to the fuel level transmitters, which they said could have resulted in false fuel gauge readings during the flight.
Although not considered factors which affected the problems with the engines, they said the installation of an unapproved tachometer and auxiliary fuel pumps had rendered the aircraft’s certificate of airworthiness invalid.
The report also noted that testimonies from other pilots experienced in operating the same type of aircraft indicated that fuel supply interruptions were possible when flying in an uncoordinated manner with less than one quarter tank of fuel.
Following the incident, the operator of the aircraft amended its standard operating procedures and instructed all pilots to have a minimum fuel quantity of 100 litres at all times for a high-risk flight.
The AAIU, which issued three safety recommendations as a result of its investigation, acknowledged that the changes would provide a greater margin of safety during flight operations and greater clarity on the minimum fuel levels for safe flights.
