Visual Flight into Instrument Meteorological Condition: A Post Accident Analysis

Abstract

The phenomenon of encountering instrument meteorological conditions (IMCs) while operating an aircraft under visual flight rules (VFRs) remains a primary area of concern. Studies have established that pilots operating under VFRs that continue to operate under IMCs remains a significant cause of accidents in general aviation (GA), resulting in hundreds of fatalities. This research used the Australian Transport Safety Bureau (ATSB) database, which contained a total of 196 VFR to IMC occurrences, from 2003 to 2019, with 26 having formal reports. An explanatory design was adopted, commencing with a qualitative study of the 26 occurrences with reports followed by a quantitative study of all 196 occurrences. Factors investigated included the locations and date of the occurrences, involved aircraft (manufacturer, model, type), pilot details (licenses, ratings, h, and medical), number of fatalities, and causal factors. Fisher’s exact tests were used to highlight significant relationships. Results showed occurrences were more likely to end fatally if (1) they involved private operations, (2) pilots only had a night VFR rating, (3) the pilot chose to push on into IMCs, (4) the pilot did not undertake proper preflight planning consulting aviation weather services, and (5) the pilot had more than 500 h of flight experience. Further results showed occurrences were less likely to end fatally if the meteorological condition was clouds without precipitation, if the pilot held a full instrument rating, or the pilot was assisted via radio. Analysis of the data using the Human Factors Analysis and Classification System (HFACS) framework revealed that errors and violations occur with slightly greater frequency for fatal occurrences than non-fatal occurrences. Quantitative analyses demonstrated that the number of VFR to IMC occurrences have not decreased even though initiatives have been implemented in an attempt to address the issue.

A Preliminary Investigation of Maintenance Contributions to Commercial Air Transport Accidents

“…For RQ2, given the small sample size, 35 accidents with maintenance contributions, testing was limited to utilizing Fisher's exact test [26]. This type of testing with small sample sizes has previously been utilized in other post-accident analyses [27]; as with that work, Fisher's exact tests were undertaken in MATLAB to determine the p-values. Specifically, in the testing of the various characteristics or features coded, the observed (O) data were the 35 accidents with maintenance contributions, while the expected (E) are those of the complete set of 1277 official accidents.…”

Airbus A32x Versus Boeing 737 Safety Occurrences

“…The data presentation here utilized the observed count relative to the expected proportion, because each manufacturer is being compared to itself. For very small sample sizes (in cases violating the requirements to use a chi squared test), a Fisher Exact test was needed [25]. The data utilized in this work has been used previously for similar studies [26], and is publicly available from ICAO [27].…”

Helicopter Pilots Encountering Fog: An Analysis of 109 Accidents from 1992 to 2016

“…A study of aviation accidents in Australia concerning visual flight into IMC conditions found that pilots were more likely to be in a fatal accident when they had more than 500 total flight hours, chose to continue into IMC, did not undertake proper preflight planning, only had night VFR rating and were involved in private operations [10]. Although this study was not exclusively concerned with helicopters, the results provide a useful benchmark for our study of helicopters encountering fog.…”