Instrument flying infrequency and weather decision-making for general aviation pilots -implications for flight safety in degraded visibility

Abstract

IntroductionInstrument-rated private pilots (PPL-IFRs) are trained to fly in degraded visibility (where visual references are lost) and, towards maintaining proficiency, required to complete 6 instrument approaches in as many months. Nevertheless, operations in such weather carry an elevated risk of a fatal accident. Two hypotheses were advanced: (i) the majority of PPL-IFRs complete fewer than 6 instrument approaches/6 months and (ii) that a subset of such aviators still depart into such weather. Methods: Instrument approaches for a group of light aircraft in single PPL-IFR ownership (aircraft/owners) in the state with the largest count of single piston engine aircraft (Texas) was determined using Automatic Dependent Surveillance-Broadcast (ADS-B) data. Departure aerodrome weather flight category was per the Iowa State University database. IMC accidents were identified from the National Transportation Safety Board database and rates determined using GA fleet time. Statistical testing used Poisson Distribution, Chi-Square and Mann-Whitney U tests. Results: Over the Aug 2020-Mar 2021 period, 1,684 flights involving 106 aircraft/owners were ADS-B-tracked. Of these aircraft/owners, 81.2% completed < six approaches (median = 1.5). Importantly, for aircraft/owners completing < six approaches in the preceding 6 months, 24% departed into obscuration. Conclusions: This study demonstrates that, for the state most populous for reciprocating engine aircraft, the majority of aircraft in single PPL-IFR ownership fail to complete 6 in-flight instrument approaches/6 months. Nevertheless, some of these aircraft/owners elect to undertake flights in degraded visibility. From a practical perspective, PPL-IFRs unable to maintain instrument currency should be cautioned on the risks of operating in degraded visibility.