The Australian Transport Safety Bureau did not conduct an
on-scene investigation of this occurrence. The report presented
below was prepared principally from information supplied to the
Bureau.
REPORTED INFORMATION
The pilot of a Piper PA-31-350 aircraft, registered VH-BSM,
reported that on 19 August 2004, the aircraft had been chartered
for a flight from Port Macquarie to Gunnedah, NSW with nine
passengers. The weather forecast indicated that instrument
meteorological conditions would exist throughout the flight.
Shortly after departure from Port Macquarie, the pilot noticed
light aerodynamic shuddering through the airframe, but discounted
this as just an idiosyncrasy of this particular aircraft.
About 75 NM from Tamworth, the pilot noticed the right engine
RPM fluctuating and the engine began to misfire. The pilot
readjusted the propeller lever for the right engine, checked the
fuel flow, and commenced a climb to a higher altitude. At
approximately 9,000 ft the right engine misfiring increased. He
then checked the right engine instruments and noticed that the
exhaust gas temperature gauge was indicating above the red line and
in excess of normal operating parameters, while the fuel flow
indication was decreasing. The pilot shut down the right engine and
feathered the right propeller, then transmitted a PAN call (urgency
alert) to air traffic control informing the controller that he `was
shutting down one engine' and diverting to Tamworth.
However, because the aircraft would not maintain altitude, the
pilot asked the controller to provide track guidance to the Walcha
airstrip. The pilot reported that during the diversion to Walcha he
was unable to prevent the aircraft from descending below the lowest
safe altitude. The controller informed the pilot that the aircraft
was deviating from the track towards an area of higher terrain. The
pilot reported that he checked the flight instruments and found
that the vertical speed indicator was indicating an increasing rate
of descent and the altimeter was decreasing, while the airspeed was
increasing. He instinctively applied corrective pitch and roll
action with reference to the attitude indicator, but the situation
worsened. He looked across at the copilot's attitude indicator and
saw that it was indicating a 45 degree angle of bank descending
turn. He levelled off with reference to that instrument and the
aircraft returned to a wings level attitude.
At about 6 NM from Walcha, the pilot saw the ground through a
hole in the cloud and he estimated that the aircraft was about 400
ft above ground level. Shortly after, he landed the aircraft at the
Walcha airstrip.
A maintenance engineering inspection revealed that a fuel line
on the right engine had come loose resulting in fuel starvation of
the right engine. The pilot also noticed that the wing flaps were
extended about 5 degrees, even though the flap selector was in the
retracted position. The pilot believed that the aerodynamic drag
produced by the flaps in that position would have contributed to
the inability to maintain altitude with one engine inoperative and
may also have caused the shuddering during the take-off. No fault
could be found with the primary attitude indicator.
After returning to Port Macquarie, the pilot discussed the
incident with the owner of the aircraft who informed him that the
flaps had been in that position for some time. The pilot reported
that the defect had not previously been annotated on the
maintenance release.
The owner later reported to the Bureau that the trailing flaps
issue had been rectified following the return of the aircraft to
Port Macquarie.