Need some help with flightplans

[Guest HepburnUGA]

I have a pretty solid understanding of the waypoints/airways involved in flightplanning. My question revolves around the speed/altitude information provided with so many of these flight plans. Let's use the following example:SWA2226 KSJC-KLAX B733/MN0438F330 SJC9 MOONY DCT AVE SADDE6Question #1... Why is the speed given in knots above FL270? Wouldn't mach number make more sense? When is knots used above mach number?Question #2... Is this speed given the ground speed?Question #3... If this is ground speed, how can I use that when entering the route information into the FMC? Or is it more used for fuel burn, enroute time calculations??Thanks for any help.Jeff

[Guest Koen]

Hi Jeff,#1: Pilots usually use mach numbers to set a given speed in the aircraft (at high altitude), but normally all flightplans are filed in knots (even if you're flying at FL430). There are a few places in the world where mach numbers are filed, like the North Atlantic and Pacific Ocean (to ensure seperation between the aircraft). Thereby, some countries use km/h as unit for speed (e.g. Russia and China).#2/3: No, it's the true airspeed. :)Kind regards,http://home.planet.nl/~duijn181/cu2/koen.jpg