Incident Overview
On 12 May 2001 at 1330 hours UTC, a Piper PA-25-235 (registration G-ASLK) was operating as a glider tug from Nympsfield Airfield, Gloucestershire. The aircraft, manufactured in 1963, was powered by a single Lycoming O-540-B2C5 piston engine. The flight was classified as training, with one crew member (the pilot) and no passengers. The pilot held a Private Pilot's Licence, was 46 years old, and had 118 hours of total flying experience, 52 of which were on type. The weather was fine with visibility estimated at 20 km in bright hazy sunshine and a cloudless inversion at 2,700 feet. Surface wind was 080°/12 knots.
Flight Details
The glider/tug combination climbed out to the east before the glider was released at 2,200 feet QFE approximately one mile east of the airfield. Three other gliders were airborne: two were soaring on the ridge north of the airfield, and one was thermalling to the south. The tug pilot noted the position of the two gliders on the north ridge. Following a right turn after glider release, the pilot began a descent at about 120 MPH while streaming the 60-metre tow rope. The intention was to carry out a right-hand circuit, keeping clear of the activity on the north ridge, and drop the tow rope at the glider launch point before making an abbreviated left-hand circuit to land.
Collision Sequence
A KA13 glider was in a right-hand orbit to the south of the airfield conducting a familiarisation flight, with an instructor in the front seat and a passenger in the rear. The tug was making a gentle left turn, with the pilot monitoring the progress of the two gliders on the north ridge and positioning to turn right base. The tug speed was reduced to 100 MPH, and the pilot estimated that the metal ring on the end of the tow rope was trailing approximately 5 metres below the tug aircraft. As the tug pilot levelled the aircraft wings, she immediately saw the KA13 glider about 200 metres ahead on a collision course at high closing speed. Simultaneously, the glider pilot saw the tug approaching from slightly above. Both pilots took immediate avoiding action: the glider dived and continued its right turn, while the tug pilot turned hard left and applied full power to climb. The Pawnee pilot felt a slight tug on the tow rope and realised it had contacted the glider. The end of the rope struck the port wing of the KA13, smashed the cockpit canopy, and then struck the starboard wing.
Injuries and Damage
The rear-seat passenger in the glider received minor cuts and scratches from the broken perspex of the canopy. The glider sustained damage to both wings and a broken canopy. No injuries were reported for the tug pilot.
Pilot Observations
The pilot of the tug aircraft considered that, while concentrating on maintaining separation from the gliders on the north ridge, she had not seen the KA13 to the south. The long nose of the Pawnee possibly obscured the glider, and with both aircraft turning south, their relative positions remained unchanged. Additionally, a white paper placard on top of the black instrument coaming was noted to reflect on the perspex, creating a blind spot. The placard has since been removed, and the club is considering fitting a device to reel in and stow the tow rope for descent and landing.