Aviation safety investigations & reports

Loss of control and collision with terrain involving Cessna R172K, registered VH-DLA near Sutton, New South Wales, on 13 April 2021

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


Download Final report
[Download  PDF: 1.34MB]

What happened

In the early afternoon of 13 April 2021, a Cessna R172K aircraft registered VH-DLA (DLA) departed Canberra Airport, Australian Capital Territory, with a pilot and observer onboard to conduct powerline survey work to the north of Sutton township, New South Wales.

About 3 hours into the flight, while conducting powerline inspection in the vicinity of Tallagandra Lane, nearby witnesses observed the aircraft flying low above the trees before commencing a left turn that continued in to a steep descent and collision with terrain. The pilot and the observer were fatally injured, and the aircraft was destroyed.

What the ATSB found

The ATSB found that while manoeuvring to align the aircraft to inspect a powerline, the aircraft aerodynamically stalled and entered a spin at a height that was insufficient for recovery prior to the collision with terrain.

What has been done as a result

Following the accident, the operator amended the training and checking section of their Operations Manual to incorporate Threat and Error Management (TEM) and Situational Awareness (SA) training modules for powerline low‑level survey operations. The amendments enhanced existing topics in the operator’s crew resource management training and stipulated learning outcomes and assessment criteria specific to TEM and SA.

The operator also advised that they intended to introduce an airspeed ‘manoeuvre margin’ to take in to account the increased stall speed associated with steep turns.

Finally, the operator plans to modify their aircraft to include an angle of attack indicator to supplement the installed stall warning and a g‑meter with recording and data download capability to enable post flight review.

Safety message

This accident highlights the need for pilots to manage airspeed and bank angle to minimise the risk of an aerodynamic stall. This is particularly important when operating in close proximity to the ground, such as during take-off, landing and when conducing low-level air work, as recovery may not be possible.

Download Final report
[Download  PDF: 1.34MB]

The investigation


This preliminary report details factual information established in the investigation’s early evidence collection phase and has been prepared to provide timely information to the industry and public. Preliminary reports contain no analysis or findings, which will be detailed in the investigation’s final report. The information contained in this preliminary report is released in accordance with section 25 of the Transport Safety Investigation Act 2003.


The occurrence

On 13 April 2021 at about 1324 Eastern Standard Time,[1] the pilot of a Cessna R172K aircraft registered VH-DLA (DLA), departed Canberra Airport, Australian Capital Territory with an observer on board to conduct power line survey work to the north of Sutton, New South Wales.

At 1622 DLA crossed Tallagandra Lane (Figure 1) and proceeded with survey work concentrating on power lines servicing properties to the east of the lane. Following the completion of two orbits, at 1624, the pilot initiated a right turn, and tracked to the north‑east.

Witnesses in the area described the aircraft flying low above the trees before commencing a left banking turn followed by a steep descent and collision with terrain. The witness reports indicated that a loss of control and entry into a spin preceded the ground impact. The pilot and the observer were fatally injured.

Analysis of recorded Garmin GPS and OzRunways flight data identified that the last Garmin GPS data point at 1624:48 showed the height of the aircraft to be about 164 feet above ground level and about 115 metres from the wreckage. The final OzRunways data point at 1624:50 was about 80 metres from the accident site.

Figure 1: Garmin GPS and OzRunways flight tracks shown relative to the accident site

Garmin GPS and OzRunways flight tracks shown relative to the accident site

Image description: DLA flight paths – Garmin data is primarily referenced due to its higher sample rate and increased vertical accuracy. The final segment of OzRunways data is included as it provided the closest data point to the accident site. Source: Google, with Garmin GPS and OzRunways data, annotated by the ATSB



Wreckage and impact information

The wreckage was located in an open field about 30 metres east of Tallagandra Lane, and about 10 km to the north-west of Sutton. There was little spread of wreckage with few parts liberated in the accident sequence. Larger items, including the propeller and the right undercarriage leg were found next to the fuselage. Items from the luggage locker were located within 5 metres of the initial impact point. The most distant item from the main wreckage was the aircraft battery which was found near the edge of Tallagandra Lane.

Examination of the wreckage showed that the aircraft impacted the ground in a near vertical, nose down attitude.

Aircraft information

DLA was a single engine, Cessna R172K aircraft. It was manufactured in the United States in 1977 with serial number R1722809 and first registered in Australia in 1978.

Further investigation

To date, the ATSB has:

  • examined the wreckage
  • collected items for further examination
  • interviewed witnesses
  • retrieved flight‑related electronic data
  • collected weather data from the Bureau of Meteorology
  • interviewed the operator.

The investigation is continuing and will include further examination and analysis of:

  • the aircraft flight path, including analysis of recorded flight data
  • pilot qualifications, experience and medical history
  • pilot flight and duty periods
  • aircraft weight and balance
  • aircraft maintenance records
  • flight survey operational procedures.

Should a critical safety issue be identified during the course of the investigation, the ATSB will immediately notify relevant parties so appropriate and timely safety action can be taken.

A final report will be released at the conclusion of the investigation.


The ATSB acknowledges the assistance of the New South Wales Police Force in supporting the ATSB on‑site investigation team through the evidence collection phase of the operation.



    1. Eastern Standard Time (EST): Coordinated Universal Time (UTC) + 10 hours.


The Australian Transport Safety Bureau (ATSB) is investigating a collision with terrain involving Cessna R172K, VH-DLA, near Sutton, NSW, on 13 April 2021.

The aircraft was conducting a powerline inspection when witnesses reported seeing the aircraft depart controlled flight before colliding with the ground. Both occupants were fatally injured.

Transport safety investigators with experience in aircraft operations and aircraft maintenance will examine the wreckage and map the accident site using a drone and other site survey equipment.

The ATSB will also analyse available recorded data and interview witnesses and other involved parties.

A preliminary report is expected to be released in a number of weeks, while a final report will be published at the conclusion of the investigation.

However, should any critical safety issues be identified at any stage during the course of the investigation, the ATSB will immediately notify relevant parties so appropriate safety action can be taken.

General details
Date: 13 April 2021   Investigation status: Completed  
Time: 16:25 EST   Investigation level: Short - click for an explanation of investigation levels  
Location   (show map): near Canberra Airport (Sutton)   Investigation phase: Final report: Dissemination  
State: Australian Capital Territory   Occurrence type: Collision with terrain  
Release date: 25 February 2022   Occurrence category: Accident  
Report status: Final   Highest injury level: Fatal  

Aircraft details

Aircraft details
Aircraft manufacturer Cessna Aircraft Company  
Aircraft model R172K  
Aircraft registration VH-DLA  
Serial number R1722809  
Operator Oberon Air Pty Ltd  
Type of operation Aerial Work  
Sector Piston  
Damage to aircraft Destroyed  
Departure point Canberra, Australian Capital Territory  
Destination Canberra, Australian Capital Territory  
Last update 09 March 2022