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On 28 July 2004, a Piper PA-31T Cheyenne, VH-TNP, with one pilot and five passengers, on a private, instrument flight rules flight from Bankstown to Benalla, collided with terrain 34 km south-east of Benalla. All occupants were fatally injured and the aircraft was destroyed by impact forces and fire. Instrument meteorological conditions existed at the time and the pilot had reported commencing a Global Positioning System (GPS) non-precision approach (NPA) to Benalla.

The experienced pilot was familiar with the aircraft and its navigation and autoflight systems. The flight did not follow the usual route to Benalla, but diverted south along the coast before tracking to the northernmost initial approach waypoint BLAED of the Benalla Runway 26L GPS NPA. While tracking to BLAED the aircraft diverged left of track, without the pilot being aware of the error. The air traffic control Route Adherence Monitoring (RAM) system triggered alerts, but controllers believed the aircraft was tracking to a different waypoint and did not question the pilot about the aircraft's position. The destruction of the aircraft navigation and flight control systems did not permit verification of their operational status. The investigation found that instructions to controllers relating to RAM alerts could be ambiguous. Actions were taken by Airservices Australia to enhance alerts and clarify controllers' responses to them.

The occurrence drew pilots' attention to the need to pay careful attention to the use of automated flight and navigation systems and also demonstrated the need for effective communication between controllers and pilots to clarify any apparent tracking anomalies. The Australian Transport Safety Bureau's (ATSB) final report was released on 7 February 2006.

In July 2008, during the subsequent coronial inquest, additional information about the possibility of dead reckoning navigation by the GPS receiver was provided. The ATSB investigation was reopened to examine that possibility and an amended report issued. That investigation found that dead reckoning navigation could not be positively established as there were inconsistencies between dead reckoning principles and the recorded radar data. Neither could it reconcile how a pilot would continue navigation by GPS with the alerts and warnings provided by the GPS receiver and the instrument indications. As a result of the reopened investigation, the ATSB issued a safety advisory notice alerting users of GPS navigation receivers to take appropriate action to ensure familiarity with dead-reckoning operation and any associated receiver-generated warning messages.

Media release and Audio Grab of Media Conference

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Preliminary Report released February 2006

On 28 July 2004, a Piper PA-31T Cheyenne, VH-TNP, with one pilot and five passengers, on a private, instrument flight rules flight from Bankstown to Benalla, collided with terrain 34 km south-east of Benalla. All occupants were fatally injured and the aircraft was destroyed. Instrument meteorological conditions existed at the time and the pilot had reported commencing a Global Positioning System (GPS) non-precision approach (NPA) to Benalla.

The experienced pilot was familiar with the aircraft and its systems and used the GPS satellite navigation system for tracking. The flight did not follow the usual route to Benalla, but diverted south along the coast before tracking to the northernmost initial approach waypoint BLAED of the Benalla Runway 26L GPS NPA. While tracking to BLAED the aircraft diverged between 3.5 and 4 degrees left, without the pilot being aware of the error.

The possibility of an error within the aircraft's navigation equipment or incorrect manipulation of the aircraft's navigation and automatic flight control systems could not be determined. Destruction of navigation and other components limited the usefulness of any testing and examination.

The air traffic control Route Adherence Monitoring (RAM) system triggered alerts, but controllers believed the aircraft was tracking to a different waypoint and did not question the pilot about the aircraft's position.

The occurrence drew pilots' attention to the risk of relying on single-source information and the need to pay careful attention to the use of automated flight systems. It also demonstrated the need for effective communication between
controllers and pilots to clarify any apparent tracking anomalies.

The investigation found that instructions to controllers relating to RAM alerts could be ambiguous. Actions taken by Airservices Australia to enhance alerts and clarify controllers' responses to them, should avoid a recurrence.

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Fatal aircraft accident raises ongoing safety issues

A Victorian Coroner recently released findings into a 2004 fatal Piper aircraft crash near Benalla, Victoria.  The findings highlight a number of safety concerns that require review by the aviation industry in relation to the safety issues raised by the ATSB in its reports released on 7 February 2006 and 2 March 2009.

These issues cover:

  • communications between pilots and air traffic control
  • terrain awareness warning systems
  • awareness of GPS in dead reckoning mode and the use of automated flight systems.

 

Circumstances of the accident

On 28 July 2004, a Piper PA31T Cheyenne crashed with six people on board, travelling from Bankstown to Benalla.  Prior to the accident the pilot reported commencing a Global Positioning System (GPS) non-precision approach (NPA) to Benalla in instrument meteorological conditions.

The flight did not follow the usual route to Benalla, but diverted south along the coast before tracking to the northernmost initial approach waypoint BLAED of the Benalla Runway 26L GPS NPA.  While tracking to BLAED the aircraft diverged left of track, without the pilot being aware of the error.  The air traffic control Route Adherence Monitoring (RAM) system triggered alerts, but controllers believed the aircraft was tracking to a different waypoint and did not question the pilot about the aircraft's position.  The pilot commenced the landing at an incorrect location.

The destruction of the aircraft navigation and flight control systems did not permit verification of their operational status.

Safety Issues

The ATSB found the following safety issues as part of the investigation:

1. Communication between Pilots and Air Traffic Controllers

The Investigation found that instructions to controllers relating to RAM alerts could be ambiguous.  Actions were taken by Airservices Australia to enhance alerts and clarify controllers' responses to them.  The occurrence demonstrated the need for effective communication between controllers and pilots to clarify any tracking anomalies.

2. Terrain Awareness Warning Systems

The ATSB made a recommendation to CASA to review the requirements for Terrain Awareness Warning Systems (TAWS) for Australian registered turbine-powered aircraft below 5,700kg with the aim of reducing the potential for Controlled Flight Into Terrain accidents.

In a recent notice of proposed rule making for Part 135 of the Civil Aviation Safety Regulations 1998, CASA included a proposed regulation that would require aircraft carrying six or more passengers, operating in instrument conditions, to be equipped with a TAWS.  This would address they type of operation in which the accident aircraft was engaged.

3. GPS in DR Mode

The ATSB and the Coroner differed in their views as to whether or not the GPS may have been in Dead Reckoning (DR) mode without the pilot being aware.[1] The ATSB considered there was an absence of technical and factual evidence to allow a positive finding to be made but acknowledged the possibility.  Further, the ATSB proposed that a fault within the aircraft's navigation or autoflight systems, mis-selection of those systems, or some combination of those factors may have contributed to the accident.

Despite not making a positive finding with respect to the GPS being in DR mode, the ATSB noted that users of satellite navigation receivers have very little explanatory information about in-flight dead reckoning navigation.  They may not appreciate that in-flight dead-reckoning navigation can provide navigation guidance along preselected routes, including the tracks of the instrument approach, without any user interaction.

The ATSB issued Safety Advisory Notice AO-2008-050-SAN-008 advising users of GPS navigation receivers to note the safety issue, and take appropriate action to ensure familiarity with dead-reckoning operation and any associated receiver-generated warning messages.

The occurrence also draws the attention of pilots to the need to pay careful attention to the use of automated flight and navigation systems.

The Coroner reinforced the need for pilots to be aware of this safety issue.

ATSB Investigations and Coronial Inquiries

Inquests are separate to ATSB investigations.  There are differences in the ATSB's and the Coroner's conclusions with respect to this accident.  However, as outlined above, the respective authorities largely agree on what the safety issues are that the industry needs to take account of.

The ATSB's report can be downloaded by clicking on the link: AO-2008-050.  Feedback can be provided via the website.

The Coroner's report can be downloaded by clicking on the link: Coroner's Report.  Queries regarding the Coroner's findings should be directed to the Coroner's Court of Victoria.

 



[1] In DR mode, signals are not being interpreted from satellites, instead the computer estimates the position based upon a calculation using the aircraft's speed and a wind component established at the last verified position.

 
General details
Date: 28 July 2004 Investigation status: Completed 
Time: 1048 hours EST Investigation type: Occurrence Investigation 
Location:34 km SE Benalla, Aero. Occurrence type:CFIT 
State: Victoria Occurrence class: Operational 
Release date: 02 March 2009 Occurrence category: Accident 
Report status: Final Highest injury level: Fatal 
 
Aircraft details
Aircraft manufacturer: Piper Aircraft Corp 
Aircraft model: PA-31T 
Aircraft registration: VH-TNP 
Serial number: 31T-7920026 
Damage to aircraft: Destroyed 
Departure point:Bankstown, NSW
Departure time:0906 hours EST
Destination:Benalla, VIC
Crew details
RoleClass of licenceHours on typeHours total
Pilot-in-CommandCommercial310014017
 
Injuries
 CrewPassengerGroundTotal
Fatal: 1506
Total:1506
 
 
 
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Last update 23 April 2014