The forgotten rain effect
Has anyone ever wondered what effect rain has on aircraft performance?
I’m not talking about the effect on braking performance during an RTO or landing, but rather on things like total weight, lift, aerodynamic drag, and energy/momentum losses.
If you calculate how much surface area a B747 has for example, then cover it with 1mm of water, how many litres of water would that equate to? I wouldn’t know how to do those calculations but I can imagine it being quite a lot.
The thin film of water must affect the aircraft’s boundary layer.
And how much momentum is lost as the raindrops pound the aircraft’s surface and instantly accelerate from a horizontal velocity of zero to anywhere from 130 kts to 300 kts?
I imagine that the rate of precipitation is an important consideration too.
Should V2 and Vref be adjusted?
I’ve searched around and have found no reference to these issues.
Any educated thoughts on this?
PS Could someone do the calculations for a B737-800? Thanks.