Sequence of events
On 25 July 2005, at about 1835 Eastern Standard Time, a Piper
Aircraft Corporation PA-31-350 (Chieftain) aircraft, registered
VH-PRJ, overran runway 27 at Nhill aerodrome following a rejected
night takeoff. The aircraft was being operated on an instrument
flight rules charter flight to Charlton, Vic, with the pilot and
three passengers on board. The pilot and passengers sustained
injuries during the overrun and the aircraft was substantially
damaged (Figure 1).
Figure 1: Wreckage of aircraft with runway in the
background
Earlier that day, the pilot had flown the aircraft from Essendon
to Ouyen and then to Nhill, arriving at about 1500. During the
stopover at Nhill, the pilot secured the flight controls by
inserting a lock pin in the control column.
The pilot stated that, when he started and warmed the engines at
about 1700, he removed the lock from the control column and that it
was reinserted after the engines were shut down. The passengers
arrived at the aerodrome at about 1820 and boarded soon
afterwards.
The pilot reported that, during the pre-flight preparation at
Nhill, he set the elevator trim to the take-off position by winding
the trim wheel to about three rotations back from the full
nose-down position. The pilot recalled removing the lock from the
control column prior to starting the engines for departure.
The pilot stated that he usually checked the flight controls for
full and free movement while backtracking on a runway but he could
not recall whether he performed that check when backtracking on
runway 27 at Nhill. Part B of the operator's Operations
Manual included a series of checklists to be used during
operation of the aircraft. The 'Start Up' and 'Pre takeoff'
checklists included checking full and free movement of the flight
controls.
A witness, located in a house adjacent to the western perimeter
of the aerodrome, reported that he observed the aircraft taxi to
the eastern end of the runway and commence the take-off roll but
lost sight of the aircraft as it moved along the runway.
The pilot stated that the take-off roll was from a rolling start
with power being slowly applied until engine turbo-charger output
stabilised. At about 90 kts indicated air speed, the pilot
attempted to rotate the aircraft but encountered resistance to
rearward movement of the control column. He decided to reject the
takeoff because the aircraft speed at the time was below his
nominated decision speed of 100 kts. The pilot reported that he
then reduced the engine power to idle and applied maximum
braking.
The aircraft overran the runway, passed through the airport
boundary fence, continued across a public road, and passed through
another fence before coming to a stop in a paddock about 162 m
beyond the end of the runway. An inspection of the runway revealed
a skid mark from the aircraft's right tyre, which commenced 65 m
before the end of the runway.
After the aircraft came to a stop, the pilot exited the aircraft
via the crew door, assisted the passengers to evacuate the aircraft
through the rear cabin door and marshalled them to an area away
from the aircraft. A passenger then used a mobile phone to contact
emergency services, who attended the scene soon after.
The aircraft
A subsequent inspection of the aircraft revealed that there were
no pre-existing defects in the elevator control system and elevator
trim system or evidence of interference with the elevator surfaces.
The elevator trim setting was found to be three and a half
rotations of the trim wheel from the full nose-down position.
Between flights, the aircraft elevators and ailerons were locked
with a removable control lock (Figure 2). The lock was a 10 cm long
pin with a red plastic warning tag which was inserted through the
control column and a locking collar that was attached to the
instrument panel. There were no external control locks fitted.
The Australian Transport Safety Bureau was advised that the
control lock was found in a cockpit stowage pocket after the
accident. An inspection of the lock shaft did not reveal any
witness marks or deformation caused by the lock being left in the
locking collar during the impact sequence.
Figure 2: View of control lock partially removed from
control column
The aircraft was fitted with a Bendix Altimatic V FD-1 autopilot
system. The autopilot controller panel was located on the centre
cockpit pedestal behind the engine controls. Engagement of the
autopilot system was accomplished by pressing the AP ENGAGE BUTTON,
located on the left side of the controller panel. The button would
illuminate when the autopilot was engaged.
The pilot could not recall whether any buttons were illuminated
on the autopilot controller prior to, or during, the take-off roll.
The system was designed to allow a pilot to momentarily override an
autopilot input to the flight controls.
The main landing gear wheel brakes were serviceable and did not
exhibit any indications of overheating.
Aircraft performance
The take-off weight and centre of gravity of the aircraft were
within limits for the flight.
The approved Aircraft Flight Manual (AFM) contained
take-off distance and accelerate-stop distance performance charts
for both normal and short field takeoffs. The investigation
calculated the take-off performance of the aircraft using the
following aerodrome and meteorological information:
- runway length 1,000 m with a bitumen surface
- runway slope 0.8 per cent down to the west
- wind 300 degrees true, 10 kts gusting to 13 kts
- no rainfall recorded during the previous three hours.
The normal take-off distance chart indicated that with take-off
power being set before brakes release, the prevailing weather
conditions and a take-off weight estimated by the investigation to
be 2,941 kg, the aircraft would have a take-off distance of about
644 m from brakes release to 50 ft. With application of the 1.24
factor specified in Civil Aviation Order 20.7.4 for charter
operations, the take-off distance required was 799 m, which was
within the length of runway 27.
The normal accelerate-stop distance charts were based on
take-off power being set before brakes release, wing flaps
retracted, a paved, level and dry runway surface, and an 'abort'
(reject) speed of 88 kts indicated air speed. The chart allowed for
a failure recognition time of 3 seconds. If the pilot technique in
applying take-off power differed from that stated on the
accelerate-stop chart, the distance to perform the accelerate-stop
manoeuvre would be more than the chart derived figure. Provided the
takeoff was rejected at 88 kts, the chart indicated that, under the
conditions prevailing at the time of the accident, the
accelerate-stop distance was about 845 m, which was within the
length of runway 27.
The aircraft manufacturer's procedure for a rejected takeoff was
included in the emergency procedure for an engine failure during a
normal takeoff at or below 85 kts. That procedure specified that
the engine throttles were to be immediately closed and brakes
applied as required to stop straight ahead.