Weather-related general aviation accidents remain one of the most significant causes for concern in aviation safety; the often-fatal outcomes of these accidents are usually all the more tragic because they are avoidable.

In the 5 years 2006–2010, there were 72 occurrences of visual flight rules (VFR) pilots flying in instrument meteorological conditions (IMC) reported to the ATSB. Seven of these resulted in fatal accidents, causing 14 fatalities. That is, about one in ten VFR into IMC events result in a fatal outcome.

Flying into IMC can occur in any phase of flight. However, a 2005 ATSB research publication General Aviation Pilot Behaviours in the Face of Adverse Weather concluded that the chances of a VFR into IMC encounter increased as the flight progressed, with the maximum chance occurring during the final 20 per cent of the flight distance.

The dangers of flying VFR into IMC have been recognised for a long time, yet VFR pilots still fly into deteriorating weather and IMC. This publication describes recent weather-related general aviation accidents and incidents that show that weather alone is never the only factor affecting pilot decisions that result in inadvertent IMC encounters. It has been produced solely with the intention of encouraging all pilots, no matter what their experience level, to develop the knowledge and skills required to avoid unintentional operations in IMC.

It should be accepted that flying under the VFR will not always enable you to reach your planned destination. Weather often does not act as the forecast predicts.

Key messages

  • Avoiding deteriorating weather or IMC requires thorough pre-flight planning, having alternate plans in case of an unexpected deterioration in the weather, and making timely decisions to turn back or divert.
  • Pressing on into IMC conditions with no instrument rating carries a significant risk of severe spatial disorientation due to powerful and misleading orientation sensations in the absence of visual cues. Disorientation can affect any pilot, no matter what their level of experience.
  • VFR pilots are encouraged to use a ‘personal minimums’ checklist to help control and manage flight risks through identifying risk factors that include marginal weather conditions.


It should be noted that pilot decision making, particularly weather-related decision making, is complex and there is no single solution to the problem of VFR into IMC occurrences. However, there are a number of measures which can be used to reduce the significant risk inherent in the operation of VFR into IMC.

The ATSB Report Improving the odds: Trends in fatal and non-fatal accidents in private flying operations, found that problems with pilots’ assessing and planning were contributing factors in about half of all fatal accidents in private operations. The report encourages all pilots to consider the following strategies to ‘improve the odds’:

  • make decisions before the flight
  • continually assess the flight conditions (particularly weather conditions)
  • evaluate the effectiveness of their plans
  • set personal minimums
  • assess their fitness to fly
  • set passenger expectations by making safety the primary goal
  • seek local knowledge of the route and destination as part of their pre-flight planning.

Also, becoming familiar with the aircraft’s systems, controls and limitations may alleviate poor aircraft handling during non-normal flight conditions. Finally, pilots need to be vigilant about following rules and regulations that are in place — they are there to prevent errors being made before and during flight. Violating these regulations only removes these ‘safety buffers’.

The Civil Aviation Safety Authority has produced media discs to address weather-related decision making. Weatherwise is an interactive presentation to enhance the ability of pilots to identify hazardous weather conditions. The Weather to Fly disc features interviews with senior pilots and human factors experts, and in-flight footage of specific locations. Some of the points covered are:

  • pre-flight preparation is importantobtain all the available weather information and update it regularly
  • make decisions early — when in doubt, turn about
  • VFR into IMC usually occurs in the last half of the flight
  • above all, do not close the back or side door (i.e. always leave an ‘out’)
  • talk to Air Traffic Control if possible
  • slow the aircraft down in precautionary mode to give more time and reduce the radius of turn
  • experience of marginal weather with an instructor is valuable
  • learn from mistakes (our own and others’).
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