2:30 pm on a scorching Saturday. 38 °C on the tarmac, 10 °C more under the canopy.
The student is due out on a solo navigation. He’s motivated, he doesn’t want to fall behind.
And everyone looks at each other. Do we go or not?
Let’s be honest: nobody wants to be the one who says stop.
The solo student? He’ll never cancel on his own initiative. He’ll say he’ll be fine.
The young instructor? Hard to be the only one cancelling while colleagues fly.
The supervisor? He doesn’t necessarily feel what the tarmac feels like.
In aviation we have limits for everything: crosswind, visibility, ceiling, duty time. Written limits, decided with a cool head. Thermal stress, however, is often forgotten, or left to the pilot-in-command’s judgement.
Yet the science is clear:
→ Working in full sun, at equal heat, cuts attention by 45% and vigilance by up to 67% compared with the same effort in the shade (study by the universities of Ottawa, Copenhagen and Thessaly).
→ Even in healthy young adults, each additional degree cuts learning by nearly 2% without air conditioning (NBER, 10 million students, USA).
→ Patience, so precious to an instructor, drops too: heat and irritability go hand in hand (meta-analysis, British Journal of Social Psychology).
→ And a recent study measures +18.7% workplace accidents in extreme temperatures (Risk Analysis).
And that’s just the pilot — not counting our aircraft’s performance, degraded as well.
That’s why Cumulus now includes the UTCI heat stress index, combining temperature, humidity, wind and solar radiation to estimate as closely as possible the physiological impact on your crews, hour by hour, at your airfields.
The index is advisory. The school writes its own rules, with a cool head. For example:
→ orange stress: no more solo flights
→ red stress: no more instruction flights
→ black stress: no flights at all
→ weighted per aircraft: air-conditioned or not, bubble canopy, shelter available for start-up…
On the day, nobody looks around anymore. The limit existed before the heatwave. It’s no longer a person saying stop, it’s a rule the school gave itself.
In the screenshot: this week’s heat stress table in Andalusia. It speaks for itself.
And in your school: who says stop when it’s 40 °C outside?
🔗 cumulus.aero
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