Recommendation

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.