The two gliders were taking part in the Australian National
Gliding Championships at Narromine NSW. One, a German registered
Rolladen Schneider LS8A glider, registered D-1003 was flown by a
British national, while the other, an Australian registered
Rolladen Schneider LS6B glider, VH-HDT, was flown by a Japanese
national. Both pilots complied with the Gliding Federation of
Australia (GFA) requirements for foreign nationals operating in
Australia.
Although some gliders in the competition had self-launch
capability, both gliders involved in the accident were launched by
aero-tow. The 52 gliders competing on the day were launched in
approximately 45 minutes. Launching commenced at mid-day with
D-1003 being launched at 1225. After release at 2,000 ft AGL the
pilot manoeuvred to take up a position near start point "Charlie"
from where he would start the day's task. Shortly before the
accident D-1003 was observed to be steadily banking to the right in
a thermal at approximately 6,000 ft AMSL, in the company of at
least six other gliders.
VH-HDT was launched at 1230 and at approximately 1315 was
observed to be approaching from the south-west, flying fast, and
manoeuvring to join those gliders circling near start point
"Charlie". HDT was seen to bank to the right to conform to the
established circling direction within the thermal. Concurrent with
banking to the right HDT pulled up sharply, directly below D-1003.
Immediately prior to the collision, HDT's angle of bank was
observed to rapidly reduce. The cabin section of HDT was observed
to collide with the lower centre and forward fuselage of D-1003.
The structural integrity of the forward fuselage of HDT was
destroyed and the forward fuselage was observed hanging
approximately 20 degrees below the normal fuselage line. The glider
descended vertically, rotating to the right, before impacting the
ground and coming to rest inverted. The pilot did not survive the
collision.
The post mortem examination did not disclose any abnormalities
that may have contributed to the accident.
The pilot of D-1003 advised that he had not sighted HDT
approaching the thermal. He felt and heard a huge impact concurrent
with D-1003 pitching violently nose down. The pilot immediately
released the canopy and seat harness before parachuting clear.
D-1003 descended in a flat spin to impact inverted 200 metres from
HDT. The pilot landed a further 200 metres away, sustaining back
injuries during the landing.
The wreckage of both gliders was examined and no pre-impact
fault was found in either glider. The examination confirmed that
HDT had impacted the lower fuselage of D-1003. There was some
evidence of intermeshing of the wings during the collision
sequence, however the structural integrity of the wings was
probably not greatly compromised by the collision.
The on-board data recorders were recovered and examined. Because
of impact damage to security switches within the units, all
recorded data had been lost.
Both pilots involved in the accident had been assigned to start
the task at start point "Charlie". Start point Charlie was
approximately 15 km north of the town of Narromine and had been
allocated to 13 of the competing gliders on the day of the
accident. A start point is a GPS position based on a geographical
feature that the pilot must transit in order to register a start
for the day's task. After passing though the start point the pilot
reports the start time and allocated point to the competition
organisers by radio. An on-board recorder that is interrogated for
verification by the competition organisers also records the start
time and position.
The organisers had nominated four start areas for the day. The
four start areas were dispersed at locations up to 20 km from the
airfield. Within each start area were five geographical start
points. Each pilot was issued with a randomly selected list of four
valid start points, one from each area. The pilot could use any
one, but only one, of these four start points. This created a
double dispersion: a scatter of start areas, and a scatter of start
points within those areas. The use of multiple start areas and
start points was introduced to eliminate the overcrowding of
airspace that occurred when just one start point was used.
Approximately 20 minutes after the last glider is launched the
organisers declare the points open which signals to the pilot's
that they can, in their own time, commence the day's task. The
start points were not open at the time of the accident. The system
of multiple start points has been deemed successful in reducing the
incidence of congestion within the start area and on the
competition task.
The pilot of HDT was wearing sunglasses and was looking through
four facets when observing features and events outside of the
canopy. At the time of the accident the sun was essentially
overhead, the sky was clear and visibility was unlimited. There
would not have been an impediment to the vision of the pilot of HDT
as he approached the thermal from the south-west. Neither the
pilot's visual acuity nor the weather were considered to be factors
in the accident.
The pull up when entering a thermal is a manoeuvre used by
glider pilots to convert forward speed to height. There are certain
etiquette's surrounding the approach to an occupied thermal and
these form part of the training undertaken by all glider pilots.
The pilot of HDT was highly experienced; he was a gliding
instructor in Australia and Japan, and he had taken part in many
national and international gliding competitions. Accordingly he
would have been aware of the factors to be considered when joining
the thermal. It is not known why the pilot of HDT did not observe
the position and flight path of D-1003 while approaching the
thermal. D-1003 was essentially on a consistent flight path within
the thermal and should have been visible to the pilot of HDT.
HDT was equipped with reasonably sophisticated navigation and
communications systems. It may be that the pilot was attending to
this equipment while approaching the thermal and did not notice
D-1003 until after initiating the pull up. The rapid change to the
angle of bank observed just before impact was probably the
initiation of an unsuccessful avoidance manoeuvre by the pilot of
HDT.
