Plane & Pilot
Tuesday, February 11, 2014

Understanding VFR Into IMC Accidents


A study of situational and pilot-related factors


While there are many factors and influences that can cause pilots trouble in flight, weather is one of the most pervasive and prominent. Pilots who don't give Mother Nature the proper respect often find themselves humbled, scared and, in the worst of cases, injured or dead. According to AOPA's Nall Report, approximately 4% of general aviation accidents are weather related, yet these accidents account for more than 25% of all fatalities.

The lethality rate of weather accidents, in other words the chances a fatality will occur in such an event, is around 63%, one of the highest among all accident types. Of these weather-related accidents, half involved attempts to continue to fly under Visual Flight Rules (VFR) into Instrument Meteorological Conditions (IMC). Among these continued VFR into IMC accidents, more than 72% were fatal versus 17% among other types of general aviation events.

A prominent study by human factor and weather accident experts Juliana Goh and Douglas Wiegmann stated VFR into IMC accidents are "a major safety hazard within general aviation," a fact clearly supported by accident statistics.

Another reason why there appears to be so much interest in these types of accidents is they're highly preventable, because as is often the case, the pilot intentionally presses on with a flight that clearly should be terminated due to deteriorating weather conditions.

And, of course, in order to have a good plan for prevention, we need to better understand the phenomenon. Thus, Embry-Riddle Aeronautical University-Worldwide (ERAU-WW) recently conducted a study to attempt to better inform pilots about VFR into IMC and offer suggestions for prevention.

Causes And Factors
Because of the extraordinary incidence and high lethality of VFR into IMC, numerous other studies have been conducted by academia, FAA, AOPA and the NTSB on the subject in an effort to better understand causes and factors related to these accidents, all of which guided the current ERAU-WW inquiry.

Of particular interest has been the relationship between flight time and accident occurrence, as well as between pilot certification and accident occurrence. Evidence supports the fact that pilots with low flight time (less than 500 hours) are involved in nearly half of all general aviation accidents. Private pilots make up around 38% of pilots, yet are involved in 49% of accidents. Commercial pilots make up 21% of the pilot population, yet are involved in 28% of accidents. Other types of pilots actually are involved in lower percentages of accidents in relation to their percentage of the population. Interestingly, student pilots make up 15% of pilots, but are involved in only 6% of accidents.

Among studies specifically focusing on weather and VFR into IMC, it has been identified that pilots often misunderstand weather or don't receive adequate education on how to interpret weather reports. According to a study by Coyne, "Despite its importance for flight safety, manypilots believe weather is the most difficult and least understood subject in their pilot training." While VFR into IMC is often assumed an unintentional digression by pilots, human factors expert Wiegmann noted that the cause of such occurrences is "often found to be a willful disregard for the regulations and cues that dictated an alternative and safer course of action."



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