Originally Posted by
tuaapache
my question is what would be the speed(ias tas Mach or groundspeed) or the correct way to find the speed in order to find the radius that we can fly for 60 mins. I am aware that the speed is non linear due to weight, so the speed varies day to day. I thought that the diversion speed can be tas ias or mach but normally Mach/ias is used rather than tas based on icao.
The speed is whatever is written on the table in the FCOM. often this is MMo/Vmo or Vmo-10.
The rule distance for the airline is normally the worst case scenario for the airlines route network assuming maximum weight the aircraft could expect on the relevant route in its network (which maybe MTOW/MLW/MZFW limited).
Different airlines can have different rule distance fir the same type.
The speeds flown on the day is entirely the pilots decision, they are not required to fly the speeds the rule distance table is based on or to land within 60 minutes.