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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.


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.

General details
Date: 19 August 2004 Investigation status: Completed 
Time: 0829 hours EST  
Location   (show map):50 km E Tamworth, Aero. Investigation type: Occurrence Investigation 
State: New South Wales Occurrence type: Abnormal engine indications 
Release date: 14 April 2005 Occurrence class: Technical 
Report status: Final Occurrence category: Incident 
 Highest injury level: None 
Aircraft details
Aircraft manufacturer: Piper Aircraft Corp 
Aircraft model: PA-31 
Aircraft registration: VH-BSM 
Serial number: 31-7405407 
Type of operation: Charter 
Damage to aircraft: Nil 
Departure point:Port Macquarie, NSW
Departure time:0805 hours EST
Destination:Tamworth, NSW
Crew details
RoleClass of licenceHours on typeHours total
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Last update 13 May 2014