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Recommendation issued to: Gliding Federation of Australia

Recommendation details
Output No: R19970094
Date issued: 03 July 1997
Safety action status:
Background:

SUBJECT

Lack of formal collision-avoidance procedure for gliders during competitions.

OCCURRENCE SUMMARY

During a competition, several high-performance single-seat gliders were flying on a triangular cross-country exercise, in loose formation at between 2,500 ft and 3,000 ft above ground level. One of the gliders near the front of the group began a left turn in search of rising air. At the same time, another glider that had recently joined the group attempted to overtake the first glider approaching from the left rear quarter of the leading glider. The pilot of the leading glider became aware of the overtaking glider just before impact but was unable to avoid a collision.

The impact destroyed the right wing of the leading glider, resulting in a loss of control. The pilot jettisoned the canopy and abandoned the aircraft at low level, receiving serious injuries in the subsequent parachute landing. The pilot of the overtaking glider was wearing a parachute but did not abandon his aircraft and sustained fatal injuries.

SAFETY DEFICIENCY

The Gliding Federation of Australia (GFA) has published 'Rules of the Air' that address right of way when aircraft are overtaking others but these rules do not directly address collision avoidance during gliding competitions where several gliders may be flying close together in loose formation for considerable distances.

ANALYSIS

The glider formations, known as gaggles, are very fluid as the pilots continually manoeuvre their aircraft in search of rising air. Aircraft relative positions change frequently and different gliders may lead as the whole gaggle manoeuvres in search of the best lift while generally progressing along the planned track. Other gliders may catch up and join the gaggle from behind and others may be overtaken by the whole gaggle.

There is a danger area behind each glider in which there may not be sufficient manoeuvring room to avoid a collision. The semi-reclining seating position of the pilot restricts the visibility to the rear of high performance gliders and pilots may only be able to effectively see to about 90 degrees left and right. The visibility ahead and above is very good through the one-piece canopies, and pilots of overtaking gliders should have sufficient warning that their aircraft is approaching the danger area behind another glider to avoid a collision.

Because of the visibility limitations and the considerable manoeuvring area needed by large, high-performance gliders with wingspans up to 24 m, only the pilot of the overtaking glider has the ability to avoid the danger area behind the glider ahead.

Pilots of overtaking gliders should be responsible for ensuring that there is sufficient manoeuvring room to avoid a collision, irrespective of any manoeuvres performed by the glider they are overtaking.

The Rules of the Air published by the Gliding Federation of Australia (GFA) state that when "One glider (is) overtaking another - the faster glider passes to the right of the slower glider".

This rule addresses the preferred passing side but does not assign responsibility for collision avoidance.

Discussions have been held with both CASA and the GFA who support the following recommendation.

Output text

The Bureau of Air Safety Investigation recommends that the GFA advise its members that the responsibility for collision avoidance when one glider is overtaking another rests primarily with the pilot of the overtaking glider. Information regarding the responsibility for collision avoidance, especially during competitions, should be published as a gliding Rule of the Air in GFA publications and brought to the attention of pilots by GFA instructors.

Initial response
Date issued: 02 December 1997
Response from: Gliding Federation of Australia
Action status: Closed - Accepted
Response text:

I refer to Air Safety Recommendation No 970094 on the midair collision which occurred on 24th January, 1997 between two gliders in the National Gliding Championships. I apologise for the delay in replying to the ASR and I thank you for the reminder on the phone today.

BASI has recommended in the ASR that GFA advise its members that the responsibility for collision avoidance in an overtaking situation rests primarily with the pilot of the overtaking glider.

We were under the impression that we had addressed the overtaking problem, both in our Operational Regulation 8.16, itself an extract from CAR 162 (3) and (4), and in our booklet "Airways and Radio Procedures for Glider Pilots". Given that pilots cannot see behind them, except to a very limited degree in very few types, it is strongly inferred in the regulatory requirements that the responsibility for collision avoidance cannot sensibly be assigned to a pilot who cannot see the threat.

Therefore it has always seemed to us to be quite adequate to mandate the overtaking side, with due allowance for hill soaring, the inference being that the pilot wishing to overtake is responsible for maintaining adequate separation. It would of course be possible to spell out the actual responsibility of the overtaking pilot for collision avoidance, but if this involves any changes to the CARs it might be more trouble than it's worth, especially with the present turmoil within CASA . Your advice would be appreciated on this matter.

I trust this clarifies the GFA position. We remain, as always, willing to discuss the matter further if you so wish.

ATSB response:

ATSB Note: Following a meeting with [name supplied] on 13 January 1998 it was agreed that the wording of the GFA Operational Regulations be changed to include the intent of car 162(3) which states:"...the overtaking aircraft.....shall keep out of the way of the other aircraft......"

 
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Last update 01 April 2011