A SLINGSBY T67C Firefly had been engaged on a training detail and was returning to its base airfield at low level when it crashed into rising ground at Mow Cop Castle, Staffordshire.

The instructor was a French test pilot who had been working as the chief pilot of a Woodford based test pilot school. His student was an officer in the Spanish air force who was about to complete a five-week performance flight test course. The student's flying experience was 1,744 hours of which 200 were in flight-testing. The day before the accident the instructor and student had traveled by road to collect the aircraft from the aircraft manufacturer's facility, since the one normally used by the school was undergoing routine maintenance. The flight back to Woodford, which lasted a little over two hours, was used to conduct some climbing performance tests as part of the training syllabus.

The following morning the instructor briefed two of his students on the planned spinning performance exercises, which were to be flown later in the day. This briefing also included safety considerations including aircraft egress, engine air starting and emergency landings. The instructor was to fly with his Spanish student in the morning and his other student that afternoon. The entry in the 'daily flight authorisation' record sheet showed that the flight had been authorised by the instructor with the flight detail entered as 'SPIN'.

The aircraft took off from Woodford and flew to the east of controlled airspace in the vicinity Gamston, Lincolnshire. Here the crew carried out the briefed spinning exercises before returning towards Woodford. The only information available on their progress was that provided by recorded radio and radar information until the aircraft was observed by witnesses in the area around the village of Mow Cop. The village is situated on high ground that forms part of the southwestern Pennine Hills. To the north and west of the village is the lower lying ground of the Cheshire Plain.

Children (aged between nine and ten years) in the playground of a local school, approximately two kilometers south of the crash site, saw an aircraft "flying low" and maneuvering above the school at low level. Some described the aircraft "bumping around in the turbulence" and carrying out three orbits of the school. Others saw it "flying up and down" before disappearing in the direction of Mow Cop. Adults supervising the children did not pay particular attention to the aerial activity.

A witness south of the crash sight heard the aircraft as it approached him. He described it as "flying straight and level" at a height estimated to be 300 feet. As it flew from his right to left it carried out a roll to the right, with a high rate of rotation in the rolling plane. When it reached the level attitude again the wings "waggled" and almost immediately the aircraft "pulled up into a loop". The witness estimated that "at the start of the loop the aircraft was below the level of the top of the ridge. After almost completing the loop, which was inclined slightly to the left of the vertical, the aircraft hit the ground with 20' nose down banked slightly to the left."

A further witness, walking his dogs close to the ruins of an old monument (known as the Old Man of Mow) on the highest point of Mow Cop, noticed the aircraft as it approached him from the southeast. He saw the aircraft pass close to trees and church in a slight descent. He estimated that the aircraft cleared the church tower by an estimated 25 feet. At that point the aircraft was heading directly towards him. The witness could, "...clearly hear the engine; the sound was uniform; there was no coughing or spluttering and no indication of any engine malfunction." It then flew over nearby houses, narrowly missing electric cables standing some twelve feet above ground level then, within half to one second it rapidly pitched nose up and rolled to the left before impacting with the ground in a right wing down attitude.

This witness arrived on the scene within thirty seconds. As he approached, the fuel ignited. Through the dense smoke from the fire the witness was able to see one of the pilots lying on the ground some ten feet from the fuselage. He dragged the pilot clear of danger and, using his own jacket, extinguished the pilot's smouldering clothing. Unfortunately it soon became apparent to him that the pilot had already sustained fatal injuries. He did not see the other pilot because of the smoke and flames.

A paramedic who lived locally had been alerted by pager and attended the scene almost immediately. Ambulance, fire vehicles and a police aircraft arrived within six minutes of the accident. The second pilot was found fatally injured in the remains of the fuselage.

On completion of the spinning exercise north and west of Gamston, the aircraft had commenced its return flight to Woodford descending below radar cover. Throughout its return flight heights (mode C corrected) of between 1,000 and 1,400 feet amsl were recorded by the radar. Study of the terrain beneath the flight path showed that generally the aircraft was flying at 400 to 500 feet agl. On occasions however the aircraft was as low as 200 feet agl and, for a short period, only 100 feet agl. As it approached Mow Cop the recorded height at the last radar position was 428 feet agl.

Where the aircraft impacted, the ground had a 20' upward slope. The initial impact was made by the right wing tip followed by the leading edge of the right wing, the right landing gear and the propeller and engine. The front of the aircraft penetrated the ground to a depth of about twenty inches whereupon the uphill slope forced the wreckage upwards causing it to become airborne again. Following the initial impact the wreckage rolled to the left, yawed to the right and came to rest inverted approximately seventy feet further into the field. There was an intense post-impact fire.

The comprehensive briefing, given by the instructor to both his students before the first flight, covered all aspects of the spinning exercises, which were planned to be flown that day. He covered the safety aspects but did not discuss low-level flying. His entry in the authorisation documentation confirmed that, at the time of signing, he intended only to carry out spinning.

The departure from Woodford and the spinning exercises were apparently carried out successfully in a routine manner. The homeward flight to Woodford, however, included flying at lower than normal heights.

Reports from witnesses in the area of Mow Cop gave, in some instances, conflicting evidence. The schoolchildren described the aircraft as circling the school several times before departing towards Mow Cop. Recorded radar information however showed that, immediately before the accident, the aircraft turned onto a northwest track with no deviation. Several witnesses described the final maneuver before impact as a 'loop'. The time taken and the height reached during the maneuver however is more consistent with the execution of a flick-roll, which can be, brought about, in this instance, by aggressive pitch control inputs.

There were no pre-impact failures or evidence of restrictions to the flying controls or aircraft systems of those parts of the wreckage that survived the post-impact fire. The cockpit engine controls showed that a setting of nearly full power was set prior to impact and evidence from the propeller showed that it was rotating.

It could not be determined why the aircraft was flown at low level for some 28 minutes before the accident or why it was flown on a track towards the rising ground at Mow Cop.