soar,. .. .as for your second Q, the T/O distance required for a particular takeoff is dependent on its' weight for a set of ambient condition.. .. .for our normal operations, we work things 'backwards'. we know the ambient conditions and the runway length. from that we work out what is our max. TO weight. thus, we know we can takeoff safely from any weights right up to the max. TO weight which we called Regulated TOW.. .. .hope this helps.... .. .SR