That 3% factor on the TO distance, queried by FoolCorsePich, can only be due to the aerodynamic drag of the open separator.
How do you figure that. If anything the drag will be less not more.
This extra required length in takeoff is consistant of every aircraft I know off fitted with a separator.
The reason for this is simple. Please read.
It's the loss of ram air effect. Nothing more nothing less. And like I said. In a b200 if you fit a raisebeck ram
Air recovery you don't loose any engine preformance with the inertia separator in the open position. If there was a case of drag then this would not make any difference.
This the separator open you loose toque. By memory in a b200 it's around 40lbs. Hence the lose of preformance.