MTOM Dry v Wet

[Pilot Positive]

I note that Performance Take Off Mass can increase for Wet runways in the same conditions as Dry runways. Ok the mass increase is modest and in most cases less than 0.5% but still useful. So why does it increase and is this aircraft specific?

I think I need to go back to school for this one


PP

[Max Angle]

Its due to the reduced screen and obstacle clearance heights (15ft rather than 35ft) used for wet runway calculations. You are not allowed to use the extra weight which is why you need to check the dry RTOW as well and use that if its less than the wet figure.

Plenty of threads in the past with more detail if you do a quick search.

[Pilot Positive]

Sigh of relief as the puzzle is solved....

Thanks Max Angle, that makes perfect sense. And just checked in our OPs manual - it has to be the least of the 2 TOMs (dry/wet) that is used - just as you say.





pp