The pilot of the Cessna 172R had planned a private flight, with
three friends, from Moorabbin via Williamstown, Laverton, Melton
and Torquay before returning to Moorabbin. Before departure, the
pilot arranged for the fuel load on the aircraft to be adjusted in
order to ensure that the aircraft did not exceed its maximum
allowable weight limit. The aircraft departed Moorabbin at about
1350 Eastern Summer Time.
Witnesses, including some with relevant aviation experience,
reported seeing the aircraft conducting steep turns south of Melton
township, north-east of Melton aerodrome, north of Gisborne and in
the vicinity of the accident site. This information is consistent
with photographs taken from the aircraft during the flight.
Radar information indicated that between 1432 and 1435, the
aircraft was flown in a sequence of left turns through 360 degrees
in the vicinity of the accident site. These turns were conducted at
an altitude of between 1,900 ft and 2,300 ft above mean sea level
(approximately 550 to 950 ft above ground level).
Witnesses reported that after completing two 360 degree left
turns in the vicinity of the accident site, the aircraft headed
north and adopted a nose-high attitude before entering a steep turn
to the left. Most of the witnesses, including an experienced pilot,
described seeing the aircraft's bank angle steepen as it passed a
westerly heading and then the nose dropped such that the aircraft
was heading approximately south in a near vertical, nose-down
attitude. However, one witness described seeing the aircraft roll
in a right-wing-over-left manoeuvre before it pitched
nose-down.
One witness reported seeing the aircraft spiral to the ground
however most witnesses saw it descend straight to the ground in a
nose-down, near vertical attitude. Witness reports and wreckage
evidence indicated that the aircraft impacted the ground heading
approximately south and in a nose-down, right wing low attitude.
The aircraft, which was destroyed by the impact, came to rest
approximately 27 m from the initial impact point. There was no
fire. The occupants received fatal injuries.
The wreckage was located in a paddock approximately 400 m north
of the Gisborne-Kilmore Road, approximately half-way between
Gisborne and Riddells Creek. The residence of one of the passengers
was less than 1 km from the accident site. The elevation of the
accident site was about 1,350 ft and Mount Macedon (3,284 ft) was
11 km to the north-north-west. The damage indicated that the engine
was producing power and that the flaps were extended to
approximately 10 degrees at the time of impact. The investigation
did not identify any pre-existing defects that could have affected
the operation of the aircraft.
Coordinated use of aileron, elevator and rudder controls will
ensure that an aircraft maintains balanced flight. Discussions with
the US Federal Aviation Authority (FAA) indicated that the Cessna
172 aircraft will exhibit mild stall characteristics if the
aircraft stalls during balanced flight, and a pilot can regain
control of the aircraft with a minimal loss of height. Most
aircraft would require significantly more height above the ground
to allow a pilot to recover control following a stall during
unbalanced flight.
The Cessna Integrated Flight Training System Manual of Flight
stated that a stall during a steep turn will result in a sharp nose
and wing drop and that recovery actions must be prompt and
precise.
The pilot held a private pilot licence and was endorsed on the
aircraft type. He had completed spin recovery training, however the
training was conducted in a different aircraft type. The pilot had
accrued approximately 68 hours total flying experience. The
post-mortem and toxicological examination did not identify any
pre-existing conditions that could have affected the pilot's
ability to fly the aircraft.
At the time of the accident the prevailing weather conditions
were fine with scattered high level cloud. The Kilmore Gap
automatic weather observation taken at 1430 indicated that the wind
was 340 degrees at 19 kts gusting to 27 kts. The observation taken
at Melbourne's Tullamarine airport at 1431 indicated that the wind
was 360 degrees at 15 kts gusting to 27 kts and that the
temperature was 33 degrees Celcius. During strong, gusting wind
conditions such as existed at the time of the accident, hills and
mountains can induce severe turbulence and downdraughts.
The aircraft was probably operating in turbulent conditions at
the time of the accident, given the location of Mount Macedon
upwind of the accident site. The manoeuvre described by witnesses
was consistent with the aircraft stalling during the steep left
turn. It is likely that the aircraft's reduced performance in the
ambient temperature and the gusty and turbulent conditions
contributed to the stall. In addition, the turbulent conditions
would have made it very difficult for the pilot to maintain the
aircraft in balanced flight during the sequence of steep turns. The
loss of control following the stall and the pilot's failure to
recover control in the height available was consistent with the
stall occurring during unbalanced flight.