Air crash investigators say the reason why the engine of a replica First World War fighter plane failed in mid-air before crash landing upside down in a field remains a mystery.

The pilot of the Albatross DV replica German warplane was returning from France to Headcorn Aerodrome when he was forced to attempt to land in September last year.

On the approach to the ground he clipped a hedgerow which flipped the aircraft upside down before it eventually crashed in the field between Bethersden and Pluckley.

The replica was made in New Zealand and was on loan to a company in the UK to perform in historic displays, and was originally manufactured in 2015.

The Air Accident Investigation Branch report was published on Thursday of last week, and noted that there had been an incident with the aircraft three flights previously which meant it required a new propeller.

The 69-year-old pilot had sent a message on the radio that the engine had began to “run rough” before it cut out. He was unhurt in the crash.

The report looked into why the six-cylinder, liquid-cooled Mercedes engine failed mid-air.

It states: “The pilot reported that sufficient fuel remained in the tanks after the accident and water and fuel temperature and fuel pressure indications were normal throughout the flight.

“A landing incident three flights previously resulted in damage that required a replacement propeller and the aircraft was returned to flight after consulting the manufacturer.

“The cause of the engine failure was not immediately apparent, and the operator advised that the aircraft would be recovered to New Zealand for further examination.”

The report can be read online by visiting the investigation branch's site.