Simviation Forums

WOW. Okay there buddy, the 477 kts is most likely refering to ground speed, not KIAS! The 737s KIAS cruisng pseed is something more like 290-310 kts, but you should be using Mach anyway (.76 to .80)

Actually that's probably true airspeed. Airspeed is measured by the force the air moving over the aircraft exerts into the pitot tube. As the aircraft flies higher, there is less air, so less pressure is exerted.  If the airspeed indicator has a 'barber pole' redline marker, stay about 10-20 knots below it, and that should give you a good balance between speed and economy.

Crap! Gimme a break, it's friday (4 day-weekend). that's what I meant

WOW. Okay there buddy, the 477 kts is most likely refering to ground speed, not KIAS! The 737s KIAS cruisng pseed is something more like 290-310 kts, but you should be using Mach anyway (.76 to .80)

why should we be using mach anyway. after all, the aircraft gives us the CHOICE to use either. most flight simmers (including me) don't know the mach system on aircraft.

lol drumline, real pilots use it and for very good reasons.

KIAS will change a great deal, but mach will not. Many cruise specifications are based on a mach speed. Also, you just plain old shouldn't be cruisng on KIAS-it's less fuel efficient then using a nice, constant, mach speed.

Also, it causes mix-ups like the aforementioned overspeed problem.  An aircraft will never, ever have one KIAS speed that it cruises on-you can't say "a 737 cruises at 310 KIAS"-you can say "a 737 cruises between approximately .77-.80, and .76 for long range."

Cruisng at an IAS setting will get you a different speed each time, and mach keeps you nice and regular. Just like metamucil.

As jknight said, Indicated Air Speed reads low at high altitude due to reduced air pressure.