Strange Crash today

[Kilrah]

I think your prop blade failed in flight due to internal stresses caused by possible prior damage, and stress caused by windchill. Crashing into soft snow would not do the damage shown on your prop blade.

You were kind of pushing the limits in flying in that cold of temperature.

People have been flying Mavics in -40°C temps, -2 is nothing uncommon.

 

[sar104]

I think your crash was caused by “Windchill.” I don’t think your blades “iced up.” I think they “froze up” due to windchill. Even though the ambient temperature was -2 C, the blades were probably about -10 C. Windchill is caused by moisture in the air. More moisture, more windchill. Windchill doesn’t only apply to skin. It can be applied to any material, be it plastic or metals.

I had a similar experience about three or four years ago when I was flying a Quad at my RC Clubs annual “Freeze Fly” on New Years Day. It had snowed the day before about 4” and the air temperature was about 35 F. Clear and sunny. The snow was melting some due to sunshine.

I had taken off and have the Quad in a hover at about 10 feet. After about two minutes, it just fell out of the sky, did a couple flips on the way down and landed upside down in the snow. Turns out that it had thrown a prop blade. Replace the prop and it flew fine after that. Had flown the Quad several times before, but at warmer temperatures. I’m thinking that particular prop had some internal stresses that caused it to fail due to the extra cold conditions.

I think your prop blade failed in flight due to internal stresses caused by possible prior damage, and stress caused by windchill. Crashing into soft snow would not do the damage shown on your prop blade.

You were kind of pushing the limits in flying in that cold of temperature. Keep in mind that Lipo Batteries do not perform well at temperatures less that 10 C.

It's possible that these props become more brittle with decreasing temperature, but they are unlikely to become weaker in terms of tensile or shear strength, and so that is not a likely explanation.

Additionally, you may have misunderstood the process of wind chill, which refers to the cooling of a warmer surface exposed to a colder airstream, in which the cooling rate is a function of wind speed. If the surface is wet then it can be cooled by evaporation to the wet-bulb temperature of the surrounding air, which is lower than its actual (dry-bulb) temperature. The props on a UAV, however, do not have any available water to evaporate unless the air is already saturated, at which point the wet-bulb temperature is (obviously) equal to the dry-bulb temperature. In this case the props very rapidly equilibrate to the dry-bulb temperature of the surrounding air, and so wind chill is not a factor.