A LIGHT aircraft that had to make a forced landing in a field near Coombe Bissett in June had lost one of its propeller blades and a second blade was badly damaged, a report has revealed.

The aircraft's propeller hub had failed due to fatigue cracking, moments after the plane had completed a sequence of aerobatic manoeuvres following a navigation training exercise.

The two men on board walked away unhurt but their plane suffered substantial damage to its engine and airframe.

The incident was investigated by the Air Accidents Investigation Branch and, in its report, published on Friday, said it was immediately apparent that the number one propeller had broken away due to a failure of the hub.

As the blade flew off, it was struck by the second blade, which suffered serious damage.

The report said: "The out-of-balance forces generated prior to engine shutdown caused the canopy to detach from the aircraft and also resulted in significant damage to the engine and its mountings."

The 28-year-old pilot, a Royal Air Force qualified flying instructor, and a second crew man, heard a loud bang as the Grob G115E Tutor plane levelled out after completing a series of aerobatics.

The plane started to vibrate, they saw debris pass the canopy and then the canopy itself started to move backwards and fall away.

At first, the pilot thought there might have been a mid-air collision but, after shutting down the engine, he saw one propeller was missing and the other badly damaged.

The pilot considered abandoning the plane but, as the vibration stopped, he decided to make a forced landing, and did so in a field of standing corn.

As the plane touched down, the nose started to yaw, the plane slid to the left and, as the landing gear collapsed, it finally came to a rest.

The report said the lost blade was found, still attached to part of the fractured hub, about 3.5km from the where the aircraft landed.

The report said investigation to establish the cause of the propeller hub failure was continuing.