Aviation safety investigations & reports

Flight below minimum altitude involving Pilatus PC-12, VH-FDJ, near Adelaide, South Australia, on 18 July 2017

Investigation number:
Status: Completed
Investigation completed
Phase: Final report: Dissemination Read more information on this investigation phase

Final Report

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What happened

On the 18 July 2017, Pilatus PC‑12, registered VH-FDJ departed Alice Springs, Northern Territory for Adelaide, South Australia, on a routine single-pilot aeromedical patient transfer flight. During the approach into Adelaide, the pilot noted that the aircraft’s autopilot system failed to intercept the localiser for the Adelaide runway 23 instrument landing system (ILS) approach.

Unaware of why the autopilot did not intercept the localiser, the pilot then became focussed on determining the cause of the autopilot tracking issue while attempting to re-establish the aircraft back on the ILS to continue the approach. The pilot reported this resulted in high workload that was further increased by the tracking information displayed on the aircraft’s course deviation indicator not reflecting the position information being communicated by ATC.

The pilot continued the approach and commenced further descent after observing that the aircraft was close to becoming established on the localiser and that the glideslope was becoming active. Soon after, ATC notified the pilot that the aircraft was below the minimum permitted altitude for the aircraft’s position and instructed the pilot to climb the aircraft to a safe altitude. The pilot then conducted another ILS approach and landed.

What the ATSB found

The unexpected failure of the autoflight system to intercept and track the localiser resulted in the aircraft deviating from the surveyed instrument approach path and significantly increased the pilot’s workload.

The pilot’s focus on resolving the aircraft's lateral tracking and perceived autoflight issues during the localiser intercept decreased his attention on managing the aircraft’s approach profile. That led to the aircraft descending off-track below the minimum safe altitude.

Detection of the off‑track descent and subsequent intervention by the air traffic controller restored safe operation.

What's been done as a result

Following this incident, the operator amended their descent, arrival, and approach procedures, and training and checking procedures to be more prescriptive. In addition, the operator introduced dual global positioning systems, with moving map and chart overlay displays into their legacy aircraft, to improve pilot situation awareness.

Safety message

Adequate approach preparation, and management of aircraft flight profile and automation is vital to ensure pilots maintain manageable workloads and positional awareness during an approach. Additionally, pilots should not hesitate to conduct a go-around or a missed approach should the functionality of the aircraft’s automation, or the validity of positional information, be in doubt.

Download final report
[Download  PDF: 1.77MB]
Alternate: [Download  DOCX: 337KB]

The occurrence

Safety analysis


Safety issues and actions

Sources and submissions

General details
Date: 18 July 2017   Investigation status: Completed  
Time: 1240 CST   Investigation level: Defined - click for an explanation of investigation levels  
Location   (show map): 19 km north east of Adelaide Airport   Investigation phase: Final report: Dissemination  
State: South Australia   Occurrence type: Flight below minimum altitude  
Release date: 18 December 2018   Occurrence category: Incident  
Report status: Final   Highest injury level: None  

Aircraft details

Aircraft details
Aircraft manufacturer Pilatus Aircraft Ltd  
Aircraft model PC-12/47  
Aircraft registration VH-FDJ  
Serial number 861  
Operator Royal Flying Doctor Service of Australia Central Operations  
Type of operation Medical Transport  
Sector Turboprop  
Damage to aircraft Nil  
Departure point Alice Springs, NT  
Destination Adelaide, SA  
Last update 18 December 2018