I bring you a weekly bite-sized chunk of the science behind helicopter human factors and CRM in practice, simplifying the complex and distilling a helicopter related study into a summary of less than 500 words.
TITLE:
Helicopter pilots encountering fog: an analysis of 109 accidents from 1992 to 2016.
WHAT?
Retrospective analysis examining helicopter accidents in which pilots encountered fog. It focuses on fatality rates and the role of intentional versus inadvertent flights into IMC.
WHERE?
USA, with accident reports from 28 states.
WHEN?
Published 2020. Accidents occurred over a 25-year period (1992–2016), based on NTSB reports.
WHY?
Although helicopters can manoeuvre or land to avoid IMC, fog-related accidents remain prevalent. The study aimed to clarify why fog encounters are so dangerous, and which behavioural and operational factors most strongly predict fatal outcomes, to inform training and operational decision-making.
HOW?
Researchers extracted and analysed 109 reports from the NTSB database that explicitly mentioned fog. Accidents were coded for fatality outcome, pilot experience, instrument rating, type of operation, whether entry into IMC was intentional or inadvertent, and whether pilots were reported as being under pressure.
FINDINGS:
- 67% of fog-related helicopter accidents were fatal (73 of 109).
- Intentional flights into IMC were significantly more likely to be fatal than inadvertent IMC encounters.
- Pilots who reported being under pressure were significantly more likely to be involved in fatal accidents.
- Total flight hours and instrument rating were not significantly associated with reduced fatality risk.
- Most accidents occurred under VFR, reinforcing the danger of visual flight into fog.
SO WHAT?
The findings challenge assumptions that experience and additional qualifications reduce the likelihood of fog-related accidents. Higher flight hours were not associated with reduced fatality risk, indicating that experience alone does not prevent pilots from either intentionally or inadvertently entering IMC. This suggests that decision-making in degraded visual environments is driven less by experience than by situational, cognitive, and organisational factors.
Perceived pressure remains central to the human factors in these incidents. Pilots who reported being under pressure were significantly more likely to be involved in fatal accidents, reinforcing that many are the consequence of decision-making under stress, rather than failures of skill alone. Addressing how pressure influences decisions, through training, procedures, and organisational culture, appears at least as important as increasing experience or technical qualifications.
For example, despite the additional training and theoretical capability to fly IFR, IR pilots were no less likely to be involved in fatal fog encounters. This could reflect the fact that some helicopters are not equipped or authorised for IFR flight, and pilots—despite IR training—remain operationally constrained when flying VFR aircraft into IMC. In effect, the capability to fly IFR does not translate into protection from IMC risk if the aircraft, procedures, or operational context do not support it.
Although unsurprising that most accidents occurred under VFR, the findings raise an important operational question: whether reliance on VFR alone is adequate for certain helicopter missions such as EMS and SAR? The results support further exploration of low-level IFR solutions, including PBN and PinS approaches, to provide structured, predictable options for helicopter flight in cloud.
REFERENCE:
de Voogt, A., Kalagher, H., & Diamond, A. (2020). Helicopter pilots encountering fog: An analysis of 109 accidents from 1992 to 2016. Atmosphere, 11(9), 994. https://doi.org/10.3390/atmos11090994
competentaviators.com 