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RWetterholt
02-09-2005, 06:24 PM
Hello all...

I posted earlier today about changing speeds from KMH to MPH...needless to say...I feel like a darn noob some of the time.

I was, however, wondering, if these speeds are totally accurate. I was in a Hellcat tonight at 3,500 feet and I was only doing roughly 270-300 miles per hour. Is this accurate? Sea level was slightly slower. Now I understand that as you go up the speeds decrease with less air for the prop/wing to grab, but it seemed as though I should be moving a little faster than 300 miles per hour at sea level.

Suggestions...if I am just being stupid, tell me...but anything to explain this would be greatly appreciated! Thanks in advance!

RWetterholt
02-09-2005, 06:24 PM
Hello all...

I posted earlier today about changing speeds from KMH to MPH...needless to say...I feel like a darn noob some of the time.

I was, however, wondering, if these speeds are totally accurate. I was in a Hellcat tonight at 3,500 feet and I was only doing roughly 270-300 miles per hour. Is this accurate? Sea level was slightly slower. Now I understand that as you go up the speeds decrease with less air for the prop/wing to grab, but it seemed as though I should be moving a little faster than 300 miles per hour at sea level.

Suggestions...if I am just being stupid, tell me...but anything to explain this would be greatly appreciated! Thanks in advance!

3.JG51_BigBear
02-09-2005, 06:27 PM
I would check your rudder trim. Its become a big issue after the last patch. Proper trim is crucial or else you will crab through the air instead of flying straight.

Tooz_69GIAP
02-09-2005, 06:34 PM
The difference you are talking about is the difference wetween True Air Speed (TAS) and Indicated Air Speed (IAS).

TAS is the ground speed(I think) at which your aircraft is really travelling through the air.

IAS is speed indicated by your instruments.

As you increase your altitude, the difference between the two becomes greater with TAS being the higher number.

For example, at 50m above sea level, if you are travelling at 350kmh IAS, your TAS will be approx 351kph. At 3,000m, at 350kph IAS, your TAS is approx 419kph. At 6,000m, for 350kph IAS, TAS is 488kph.

This is to do with the lower air density at higher altitudes, and your instruments work from measuring how much/fast(not sure which) air travels through the pitot (the sticky outy thing on most aircraft wings), but when air is at a lower density, the pitot doesn't pick up the flow as well, so it puts your airspeed lower that it actually is, or something like that.

I'm sure others can give you a better (or rather, a correct) explanation!!

VW-IceFire
02-09-2005, 07:05 PM
Yep, you got it Tooz.

The long and short is this: IAS (indicated) is what your aircraft instruments are telling you is the air passing your plane. TAS (true) is what you're actually managing in speed over the ground.

You're IAS is going to be the same at sea level and changing quite a bit by the time you reach 10,000 meters (or about 32,000 feet). TAS is always going to be higher than IAS (above sea level) and thus you shouldn't worry too much when it seems like you're going pretty slow up at high altitude. Its a bit disconcerting but you'll get used to it.

MrMoonlight
02-10-2005, 02:06 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by VW-IceFire:
Yep, you got it Tooz.

The long and short is this: IAS (indicated) is what your aircraft instruments are telling you is the air passing your plane. TAS (true) is what you're actually managing in speed over the ground.
<HR></BLOCKQUOTE>

Well, that's almost correct. TAS is your IAS corrected for temperature and pressure relative to the surrounding air. Groundspeed is your speed relative to the earth's surface.

If you're flying with an TAS of 200 knots into a 20 knot headwind, your groundspeed is actually 180 kts...with a 20 knot tailwind, you'd have a 220 knots groundspeed. But your TAS would still be 200 knots in either case.

Yeah, in the sim you can generally say that TAS is your groundspeed at altitude, since the sim does not model winds at altitude. However, closer to the ground (e.g. during takeoffs and landings) in certain weather conditions, winds are modeled. Like when you're sitting still on the carrier deck chugging along at 20 kts sailing into a 20 kt wind. Your airspeed indicates 40 kts. That's when your groundspeed and TAS can differ. In such a case, your TAS is 40 kts, but your groundspeed is actually only 20 kts (speed of the ship).