Abstract
Purpose :
Anticipated air travel demand is expected to exacerbate the ongoing global pilot shortage. Pilots must maintain valid medical certificates to validate their licenses. Although visual standards within medical certifications are imperative, their foundation lacks concrete evidence, potentially unnecessarily limiting candidate pools and influencing pilot retention. We examine how visual function influences flight performance.
Methods :
Twenty-six participants (12 female, 13 male), with various piloting experience (0-400 flight hours) flew simulated flight circuits in an ALSIM AL250 Flight Simulator. Flights were completed in three weather conditions (high wind, heavy rain, or a combination of the two) and 5 vision degradation levels (0, 1.0, 1.3, 1.6, and 1.8 logMAR) for a total of 15 trials per participant. Visual acuity, contrast sensitivity and stereoacuity were measured at all levels of visual degradation. Participants were divided into two groups. Group 1 had their vision degraded by scatter using the Cambridge Simulation Glasses. For Group 2 vision was degraded using defocus lenses. Trials stopped when pilots completed the flight either by landing, crashing the plane, or reaching the 5-minute time limit. Outcome measures included slope of altitude descent, variability of vertical speed, airspeed, pitch, and roll. Data were analyzed using mixed model ANOVAs followed by Fisher’s LSD post hoc test.
Results :
There was an effect of vision degradation on the variability of vertical speed, pitch, roll, and the slope of altitude descent. Results showing the main effect of level of vision degradation are summarized in figure 1. There was a significant main effect of vision degradation type on slope of altitude descent in heavy rain (F(1,24) =6.03,p=0.02). There was a significant interaction between degree and type of vision degradation for the slope of altitude descent during high wind conditions (F (4,96)=5.64, p=0.0004). There were no other significant main effects or interactions. Post hoc analysis revealed that flight performance was first affected at 1.0 logMAR and 1.3 logMAR degradation with scattering and defocusing lenses respectively.
Conclusions :
In poor weather conditions, pilots can successfully land an aircraft with considerable visual degradation. There is opportunity to update visual medical standards for pilot licensing.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.