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The plan for the flight was for the tug aircraft to air-launch the glider and then to fly to Tipton to retrieve another glider. The glider pilot indicated to the tug pilot that he wanted to be towed to a thermal to the north west of the strip. Flying conditions in the area were reported to have been moderately turbulent.

Radio communications for the initial tow-rope hook-up were normal, with the tug pilot responding normally to the glider pilot's instructions. After becoming airborne, the tug pilot made a right turn through about 40°, onto a heading of 340°, and continued the climb. When the aircraft were about 1,200 ft AGL they encountered a strong thermal. After both aircraft had stabilised in the thermal, the glider pilot noted that the variometer was indicating lift in excess of 10 kt. He then disconnected the tow and transmitted 'rope gone' over the radio while commencing a right turn. He observed the tug aircraft begin a gentle turn to the left.

The glider pilot completed a turn through 360° and decided to fly another orbit, but at a greater angle of bank to better utilise the thermal. When heading approximately south-west at about 1600 ft, the glider suddenly yawed violently to the right and the control column was torn from the pilot's hand. At the same time, the glider adopted a steep nose down altitude. The pilot was able to regain control of the glider at a height of about 11 00 ft above ground level and saw the tug aircraft below spiralling anti-clockwise towards the ground.

The pilot was able to control the glider by the use of left rudder and almost full right aileron. A right circuit was flown and the glider landed on the departure strip.

A ground witness observed the release of the tow but did not observe the mid-air collision. He and another ground witness observed the tug aircraft spiral and dive vertically into the ground. The tug aircraft impacted the ground at an indicated airspeed of 116 kts and was destroyed.

Damage to the glider was restricted to its left wing. The inboard half of the left aileron had been broken off in a downward motion. The trailing edge of the left wing was split for most of its length, and a small dent was present on the trailing edge about 500 mm from the wing root.

Examination of the impact marks on both aircraft indicated that the left wing of the tug had collided with the trailing edge of the left wing of the glider when it was banked right at about 40°. The strut attachment area on the front spar of the tug's wing had impacted the glider about 300 mm inboard of the aileron while the tug was moving outboard relative to the glider. The leading edge of the tug wing had then broken off part of the glider aileron and become snagged on the wing at the aileron cutout. This tore the wing fabric, destroying the aerofoil shape of the outboard section of the left wing. The top of the tug's left wing was then dragged inboard and rearwards across the lower surface of the glider's left wing. The top left corner of the cockpit roof of the tug probably made light contact with the trailing edge of the left wing of the glider at a point about 500 mm from the wing root. This indicated that the angle of bank of the tug was about 23° greater than that of the glider at the time of collision.

Analysis of the possible flight paths from glider release to the impact point indicated that the tug pilot might not have heard the glider pilot call 'rope gone' and could have been still trying to maintain the glider in the thermal, pending tow release by the glider pilot. It could not be determined why the tug remained in the thermal. It is possible that the tug pilot was aware that the glider pilot had released and was using the strong thermal updrafts in the manner of a glider. Other tug pilots report that it is difficult to determine if the glider is still under tow in turbulent conditions. Thus it is possible that the tug pilot was unaware that the glider pilot had released.

The glider pilot reported that there was a significant amount of radio traffic on the local airstrip frequency at the time he released the tow. This was caused by the number of gliders in the air in both the local and Kingaroy areas. Gliding organisations use one radio frequency for operations at the airstrip and another for area operations. However, it was reported that the airstrip frequency was used almost exclusively while the area frequency received little use. In this instance, the frequency for airstrip operations was also the Kingaroy common traffic advisory frequency (CTAF).

Significant factors

The following factors were considered relevant to the development of the accident:

  1. The tug remained in the thermal for reasons that could not be determined.
  2. The tug pilot did not see the glider in time to avoid a collision.
  3. The tug pilot was unable to regain control of his aircraft due to the damaged wing.


Safety Action

Recommendation

The use of radios and control of glider operations have been the subject of investigation in three recent, fatal, mid-air collisions between gliders and fixed wing aircraft:

  • Tocumwal NSW 2 November 1990 VH-CAG/GXO
  • Tocumwal NSW 8 February 1992 VH-UTKlGOR, and
  • This accident, Jondaryan Old 1 November 1992 VH-SCT/WGR.

The Bureau of Air Safety Investigation therefore recommends that:

  1. The Civil Aviation Authority, in conjunction with the Gliding Federation of Australia, develop and implement national standard operating procedures for radio use in glider operations.
 
General details
Date: 01 November 1992 Investigation status: Completed 
Time: 1420 EST Investigation type: Occurrence Investigation 
Location   (show map):3km NE Jondaryan Occurrence type:Airborne collision 
State: Queensland Occurrence class: Airspace 
Release date: 19 November 1993 Occurrence category: Accident 
Report status: Final Highest injury level: Fatal 
 
Aircraft 1 details
Aircraft manufacturer: Piper Aircraft Corp 
Aircraft model: PA-25 
Aircraft registration: VH-SCT 
Type of operation: Private 
Damage to aircraft: Destroyed 
Departure point:Jondaryan Qld
Departure time:1417
Destination:Tipton Qld
Aircraft 2 details
Aircraft manufacturer: Glaser-Dirks 
Aircraft model: DG-100 
Aircraft registration: VH-WQR 
Type of operation: Gliding 
Damage to aircraft: Substantial 
Departure point:Jondaryan Qld
Destination:Jondaryan Qld
 
 
 
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Last update 13 May 2014