Thanks all,
I did some calculation with meril's performance charts,
For example:
All engines operative
weight 14300kg
pa 0ft
temp 10°
hover height 10ft
torque required 90%
One engine inoperative (twin eng condition)
weight 14300kg
pa 0ft
temp 10°
hover height 10ft
more than 125% (out of chart range!!!)
For the rule of 1/3 with a 3 engines 90% Trq in case of engine loss it has a 30% trq increase....but it seems not correct
On Merlin comunity i heard about this rule trq x 3:2, this means 90% x 3 divided by 2 so 135%.....but this one look to me a rough method.
I think is very important for a pilot in command know precisely about this numbers because it change a lot the resolution of an emergency.
What you think??