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Airspeed at sea level (ASL) is a constant. The same as groundspeed.
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You seem to be indicating your ASL as the same as IAS. So, would your definition be true at high tide, or low tide? What about on a day with a really low pressure front moving through?
Really simplified. Purists, please forgive me.
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...the SR-71 looks to me like it can go through the air at better than 220 mph IAS at sea level and better than 220 IAS at 85,000 feet....
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This is a classic mistake of confusing speed with pressure. You should ask yourself "just what is that gage measuring"?
Aircraft measure their speed by air pressure - IAS is really a measurement pressure.
To the pilot, IAS (especially Mach) is more important because it tells you when you are going to stall, compress, or be happy. Stall speed is always IAS. To the navigator, TAS is more useful because they want to know position. Fortunately (in the pre GPS days) there were lots of nifty tables you could use to convert the two, based on altitude (which is another measure of pressure..[img]/phpBB/images/smiles/icon_wink.gif[/img]).
As you climb you have to keep increasing your TAS to maintain speed because as the pressure drops, your IAS drops. There comes a point in your climb where you can't increase your TAS anymore and that little IAS needle hits the rated stall speed. At this point you are no longer flying; gravity has reclaimed your sorry a**.
If the SR-71 was reporting an IAS speed of 2200mph at 85,000ft, that would be suspicious for a number of reasons.
Firstly, because (you are correct on this, though grossly misinterpretated) the aircraft would be traveling at an ungawdly TAS speed. Secondly, because supersonic aircraft report their speed as a Mach number at an altitude. Thirdly, the pressures and frictions generated by an IAS value of 2200mph would fry an aircraft (remember, IAS is a measure of PRESSURE not speed). And, finally, the TAS as cited by the time over distance records (note that there's refueling lags in those data...those guys sure can refuel quiclkly!) is incontrovertible.
When you actually examine the data, you will find that the 2200mph value is a "civilian" number converted to TAS; a value given to the great unwashed public who are used to automobiles, and only understand TAS. At no point does any data report an IAS value of 2200 mph.
<font size=-1>[ This Message was edited by: bozola on 2002-08-22 11:48 ]</font>