'CARBURETTOR icing' has been blamed as the most likely cause of a light aircraft crash near Prestwick Airport earlier this year.

The Piper PA-28-181 suffered a loss of engine power and was forced to land 1.5 miles from the airport, hitting a tree and causing serious injuries for those on board.

The Air Accident Investigation Branch (AAIB) has now published its report into the accident on April 23, 2024.

Emergency services were called to Ladykirk House at Monkton, and a nearby stretch of road was closed as a result of the incident, with police asking people to avoid the area.

The injuries sustained by the two men, aged 65 and 75, on board the plane were described as "serious".

HM Coastguard airlifted the two men to Queen Elizabeth University Hospital in Glasgow, while the Scottish Fire and Rescue Service sent two pumps and two specialist appliances to the scene.

The AAIB blamed 'carburettor icing' as the most likely cause of the accident, which led to the forced landing.

Carburettor icing occurs when water vapor freezes on the internal surfaces of an engine's carburettor, reducing the airflow to the engine. 

This can happen when the temperature in the carburettor drops below freezing, and when carburettor heat is not turned on.

The report states: "While the aircraft was on a right base leg for an approach to Runway 30 at Prestwick Airport, air traffic control lost visual and radio contact.

"The aircraft had suffered a power loss and established a glide descent. The aircraft hit a tree during the latter stages of the forced landing, and subsequently struck the ground vertically nose-down. Both of those on board sustained serious injuries."

The AAIB found that the weather conditions at the time led to a "serious risk of carburettor icing". 

The carburettor air inlet valve was found in the full cold position, indicating that carburettor heat was not selected.

Investigators confirmed that the valve could not have changed position when the aircraft struck the ground.

The report continued: "The general handling portion of the flight was carried out without incident and neither pilot recalled any precursor symptoms that would have suggested any issues with the engine.

"During this phase of the flight they conducted several PFLs that involved sustained descents
at idle power.

"The use of carburettor heat in these descents would have been appropriate and is suggested in the aircraft check list. Both pilots were sure it was used during these exercises.

"On returning to the right hand circuit the aircraft made a successful stop and go. Both pilots believed that the downwind checks had been completed and that a carburettor heat check was carried out as a part of those.

"Neither was absolutely certain about the carburettor heat setting during the orbits made from downwind.

"At this point the aircraft would have been at a power setting where the risk for carburettor icing was severe."

The pilot in charge (PIC) of the aircraft was 75 at the time of the accident, with 307 hours of flying experience, but none in the three months before the incident.

The pilot's rating had lapsed in July 2023, and the flight was an attempt to recover his currency by flying with a chief flying instructor (CFI) of a flying club based at Prestwick. 

The report added: "The PIC had not flown since November 2023 and believed that he was taking appropriate action to recover his currency by flying with the CFI, and that the CFI was acting as an instructor during the accident flight.

"The CFI stated that he took notes of the PIC’s performance to facilitate a post-flight debrief."

It was found that because the CFI's medical was suspended at the time of the accident, the flight did not comply with rules stating that passengers should not have been carried.

The full report can be found on the Air Accident Investigation Branch website.