SurClaro Flight Simulator Resources

whyareyoualive · Joined: 04 Oct 2007 Posts: 27

hi, ive become curious of the fact that despite it saying an aircraft has, for instance, a cruising speed of 550kts, you cant generaly go above 340kts airspeed without the overspeed alarms going off. i then thought well maybe its 550kts groundspeed, but at 32000ft travelling at an airspeed of 330kts, the groundspeed is in the area of 500kts. this doesnt make sense to me, and was wondering if there was a perfectly obvious answer to this oddness?

tropicalfish · Joined: 04 Oct 2005 Posts: 860

Usually cruise speed is dependent on mach speed. Typically, it's Mach 0.80 or mach 0.85.
The knots will vary in number even with the same mach number.

jaeger52 · Joined: 28 Sep 2005 Posts: 442 Location: Minneapolis, MN

I've been forever scratching my head over this conundrum myself for time out of mind. Thanks for your cryptic reply T-Fish, but it doesn't really qualitatively answer the question in the least degree (at least for me). Some might be able to interpret textbook gobbledygook, which assumes that the end user is learned in terminology, gauges, etc.

Poke all the fun you want to in my direction, but I pound nails for a living. And that's why I depend heavily on SurClaro to assist me when I encouter some FS component that I don't understand.

I can't even tally the number of fine aircraft that I've trashed over the years because of my lack of knowledge on this very subject. I suppose that part of the answer is aircraft specific in nature. But isn't there some kind of a conversion chart or rule of thumb that would help a guy determine mach -vs- IAS?

At the very least, provide a link which easily explains the problem at hand (not more endless pages of technobabble. :cry:

Jaeg-

rd · Posted: Sat May 31, 2008 5:03 am Post subject:

Read First:

http://www.aerospaceweb.org/question/instruments/q0210.shtml

Read Second:

http://www.aerospaceweb.org/question/instruments/q0251.shtml

RD

mel wilson · Posted: Sat May 31, 2008 8:10 am Post subject:

Thanks for the links RD, cleared up a few questions of my own also.. :wink:

Mel.

rd · Posted: Sat May 31, 2008 8:26 am Post subject:

Glad to be of service.

And to think that all I do, is beat up, or out do, or over manipulate the sim.
sheeesh.

RD

whyareyoualive · Joined: 04 Oct 2007 Posts: 27

thanks. having read that im now slightly clearer about what is going on. however im still a bit uncertain about why that means the indicated airspeed in for instance my 737 400 always has a limit of 340kts. surely this would vary depending on the wind ?

whyareyoualive · Joined: 04 Oct 2007 Posts: 27

thanks. having read that im now slightly clearer about what is going on. however im still a bit uncertain about why that means the indicated airspeed in for instance my 737 400 always has a limit of 340kts. surely this would vary depending on the wind ?

KA0014 · Joined: 06 Nov 2007 Posts: 424 Location: usa

are you guys meaning the barber pole thats in the speed indicator? cause yes if you pass that ya get the over speed warning. cause when i flew for a virtual airline. the guys i once flew with who was my copilot/ boss :oops: said that once ya go past the barber pole ya have to slow the plane down fast. other wise ya can burn out the engines. and cause damage to the plane. :oops: . now if this is not the subject. i'll feel like a bafoon :lol:

Cat1 · Posted: Tue Jun 03, 2008 9:35 pm Post subject:

whyareyoualive wrote: thanks. having read that im now slightly clearer about what is going on. however im still a bit uncertain about why that means the indicated airspeed in for instance my 737 400 always has a limit of 340kts. surely this would vary depending on the wind ?

Actually it doesn't always have a indicated limit of 340 knots, that speed is reduced by altitude. The higher you fly the slower your max indicated airspeed is. Think of indicated airspeed as "calibrated" airspeed.

KA0014 · Joined: 06 Nov 2007 Posts: 424 Location: usa

huh? i thought the higher ya went the more the airspeed increased not decreased. cause i wathced the barber pole. and about 10,000 feet it was at the 450mph range. but i never passed it

Cat1 · Posted: Tue Jun 03, 2008 9:45 pm Post subject:

Go and fly a 737 and let me know what you see?

KA0014 · Joined: 06 Nov 2007 Posts: 424 Location: usa

a rusty pilots nightmare. cause i haven't flown that thing in ages sorry :oops:

Then try another one, just notice that as the altitude increases the max indicated airspeed goes down

capt.PropwashKCHS · Posted: Wed Jun 04, 2008 9:43 pm Post subject:

heres another way of thinking about it....

at sealevel, the NORMAL atmospheric pressure is (i believe) 7.5 lbs / square inch (29.92 inches of mercury -- barometric pressure) because there is so much air that is above you and being pressed down and around you.

ok, now what is the air pressure / barometric pressure in outer space?? ummm .. 0 zero. Thus, the higher in altitude you go, the less air there is.

ok, so what the hell does that have to do with flying?? umm, you need AIR in an internal combustion engine, so the more air there is at 5,000 feet you will go faster than if you were at 50,000 feet with the same craft. LESS AIR = LESS SPEED