Aviation occurrence briefs

VFR into IMC and collision with terrain involving a Cessna 150, near Mount Mercer, Victoria on 23 November 2020

Status: Completed
Investigation completed


Occurrence Briefs are concise reports that detail the facts surrounding a transport safety occurrence, as received in the initial notification and any follow-up enquiries. They provide an opportunity to share safety messages in the absence of an investigation.

What happened

On the morning of 23 November 2020, a Cessna 150 departed Peterborough, Victoria on a private flight to Deniliquin, New South Wales, with the pilot and one passenger on board. The en-route weather forecast obtained prior to flight indicated a band of marginal weather moving to the east followed by clearing weather behind. The pilot assessed that the conditions on the route chosen would be initially suitable for flight under VFR[1] with conditions improving during the day.

During the flight, the weather began to deteriorate approaching the Ballarat area. The pilot observed increasing overcast cloud on the intended track and was forced to descend to stay in VMC.[2] Approximately 15 NM south of Ballarat airfield, at 800 ft and now several miles right of track, the pilot received the weather from the aerodrome weather information service which was indicating a cloud ceiling at Ballarat of 5,000 ft. After the sudden appearance of wind turbines off to the right of track, the instrument-rated pilot decided to commence a climb to get above the cloud, which was believed to be 1,000 ft thick. Passing 3,500 ft the airspeed indicator became unreliable and was fluctuating significantly despite the pitot heat being on. The decision to reverse course and descend out of cloud was made. The pilot became visual with the ground about 200 ft above the trees and began searching for a suitable landing area.

As the pilot searched, it became increasingly difficult to maintain visual reference with the ground and they decided to immediately land in a paddock. Selecting a paddock, the pilot lined up on approach and on short final a wire fence was sighted which required an adjustment just prior to touchdown. This adjustment increased the ground roll and the aircraft passed through another fence before the wing tip collided with a small shed and the aircraft came to rest on an embankment.

Figure 1: Aircraft in situ post collision

Source: Operator

  • Pilot comments – In hindsight the pilot suggested they could have either delayed the departure of the flight until the marginal weather had passed or planned a route further to the west to remain clear of it altogether.

Safety message

The ATSB continues to investigate weather-related general aviation accidents. VFR into IMC remains one of the most significant causes for concern in aviation safety; the often-fatal outcomes of these accidents are usually avoidable. In the 5 years prior to the occurrence, there were 57 reported VFR into IMC occurrences, 7 of which resulted in accidents, with 10 fatalities.

The ATSB SafetyWatch highlights the broad safety concerns that come out of our investigation findings and from the occurrence data reported to us by industry. One of the safety concerns is inflight decision-making.

The decision whether to proceed is the first decision the VFR pilot faces when confronted with less than visual meteorological conditions. Flight Safety Australia article '178 seconds to live' illustrates the stark reality of attempting to fly in IMC conditions without adequate training.

About this report

Decisions regarding whether to conduct an investigation, and the scope of an investigation, are based on many factors, including the level of safety benefit likely to be obtained from an investigation. For this occurrence, no investigation has been conducted and the ATSB did not verify the accuracy of the information. A brief description has been written using information supplied in the notification and any follow-up information in order to produce a short summary report, and allow for greater industry awareness of potential safety issues and possible safety actions.


  1. Visual flight rules (VFR): a set of regulations that permit a pilot to operate an aircraft only in weather conditions generally clear enough to allow the pilot to see where the aircraft is going.
  2. Visual Meteorological Conditions (VMC): an aviation flight category in which visual flight rules (VFR) flight is permitted – that is, conditions in which pilots have sufficient visibility to fly the aircraft while maintaining visual separation from terrain and other aircraft.
General details
Date: 23 November 2020   Investigation status: Completed  
Time: 1030 EDT    
Location   (show map): Near Mount Mercer, Victoria    
State: Victoria    
Release Date: 23 December 2020   Occurrence category: Accident  
Report status: Final   Highest injury level: None  

Aircraft details

Aircraft details
Aircraft manufacturer Cessna Aircraft Company  
Operator Private  
Type of operation Private  
Sector Piston  
Damage to aircraft Substantial  
Departure point Peterborough, Victoria  
Destination Deniliquin, New South Wales  
Last update 23 December 2020