Sequence of events
The pilot of a Pitts aerobatic aircraft arranged to fly to a
training area to the south of Archerfield in company with a friend
in a Yak aerobatic aircraft. They planned to practise aerobatics
for about 30 minutes. The area selected was over a pine forest with
a duplicated high-tension power line traversing the forest. North
of the power lines the trees had been cleared and grass to about
500 mm high was the only significant vegetation in the area. The
terrain was gently sloping up towards the north-west. The pilots
agreed to operate on either side of the power line with the Pitts
operating to the north of the line.
When the pilot of the Yak aircraft completed his sequence he
attempted, unsuccessfully, to contact the Pitts pilot by radio. He
also could not see the aircraft. When he flew closer to the power
line he observed a small fire and realised that the Pitts aircraft
had crashed. The pilot then contacted the Archerfield Air Traffic
Controller to alert emergency services.
A resident located north-east of the accident site had observed
the Pitts aircraft flying manoeuvres parallel to the power line.
During one manoeuvre conducted to the north-west and away from the
observer, the aircraft appeared to be flying straight, with the
wings vertical, as if in a manoeuvre known as a "knife-edge". The
upper side of the fuselage was directed away from the power line.
The aircraft appeared to be descending but the person was aware
that the aircraft was moving away and thought that the apparent
descent may have been an illusion. After a vertical climb and
descent involving rolling manoeuvres, the aircraft again flew in a
straight line with the wings vertical. On that occasion the
aircraft was tracking to the south-east and toward the observer,
and the upper fuselage was again oriented away from the power line.
The observer stated that the aircraft appeared to be descending,
and passed from sight behind a low ridge. He did not see the
aircraft again and some time later saw smoke rising from behind the
ridge.
Aircraft examination
The aircraft impacted the ground in a wings-level attitude at a
speed estimated at more than 100 kts, while travelling in a
north-westerly direction. At the time the aircraft was descending
at about 30 deg nose down, and appeared to have been in balanced
flight and at a low "g" loading. The impact was considered not
survivable. The aircraft did not bounce, coming to an extremely
rapid stop in the sandy soil. The fire would have broken out
immediately, as a result of the ruptured fuel tank and disruption
of the electrical system. The aircraft was destroyed by impact
forces and the post-impact fire.
The engine was dissassembled and inspected. The crankshaft had
moved rearward by about 6 mm relative to the crankcase, a further
indication of an abrupt stop. The lack of damage to the cylinders
indicated that the propeller and crankshaft had taken most of the
deceleration loads, transmitting them through the crankcase to the
airframe. There was no indication of mechanical failure prior to
impact. The available information suggested that the engine was
operating at low to moderate power at impact.
The Pilot
The pilot held a private pilot's licence to fly aeroplanes. His
Class Two medical certificate was valid until June 2001. He had
commenced flying training in January 1983 and obtained an aerobatic
rating in March 1995. The rating was progressively upgraded, and in
November 2000 the pilot was approved to conduct aerobatics to a
minimum height of 100 ft.
The pilot purchased the Pitts aircraft in September 1997 and had
flown it almost exclusively since then. His most recent biennial
flight review, which included aerobatic flying, was conducted in
May 1999.
Although he normally flew without a parachute, on the accident
flight the pilot was wearing a new parachute pack for the first
time. The pack thickness was about 4 cm.
Weather conditions
At the time of the accident the sky was clear of cloud, and the
wind was a light south-westerly. The pilot of the Yak aircraft
assessed that the temperature was in the mid-thirties [Celsius].
The temperature and humidity at the accident site were considered
by an experienced pilot to be such that conditions in the cockpit
of the Pitts aircraft would have been oppressive.
Aerobatic manoeuvres
One of the manoeuvres the pilot was intending to practise was a
"knife-edge" manoeuvre where the aircraft was flown straight and
level while banked 90 degrees left or right. That manoeuvre was
referred to as a stick-position manoeuvre, because the positioning
of the control column and rudder pedals must be precise to place
the aircraft in the correct attitude and flight path. Practice and
familiarity are the primary means of ensuring accuracy.
In the immediate vicinity of the crash site there were no
prominent visual indicators for the pilot to judge the height of
the aircraft above the ground. The vegetation was low and devoid of
trees, and the terrain was not sufficiently sloping to provide the
pilot with good height cues.
Examination of terrain contours and the location of the observer
indicated that the aircraft was probably below 30 ft above ground
level at the time it was lost from sight behind a ridge.
