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Old 10-09-2018, 05:05 PM   #11
The Integrator
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Quote:
Originally Posted by jojo View Post
In fact, the real limit for a supersonic aircraft is temperature.
These speeds are just guidelines for the pilot, and the Mirage HUD display CAS.

Have you looked for the definition of Calibrated Air Speed ?
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Calibrated airspeed is the same as Indicated airspeed but corrected for position error (it’s “true indicated airspeed” if you will). You’re right that that is the number you should be looking for with regards to structural limits...
Is it not the case that calibrated (or true) airspeed, TAS, is the IAS accounted for calibration errors, air density, temperature etc. and wind? In other words, in zero wind conditions, it is the same as GS. This means that even if I am in a region of very low air pressure my TAS will not change compared to a region of very high air pressure, my IAS will. Surely then IAS is the best measure of dynamic pressure (which is what the pitot tubes and hence IAS are really measuring) and hence of airframe stress?
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Old 10-09-2018, 06:18 PM   #12
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I don't see it that way.

Yes, IAS is better limit than TAS for airframe stress.
But IAS still has instrumental error.
CAS is corrected of these errors.

Anyway, as I said above, the limit isn't speed but temperature (airframe & engine).
This isn't your Cessna.

Mirage IV was famous for being able to melt her antennas...
After some threshold speed, the plane would accelerate in supersonic without AB, and the pilot had to throttle back.

I bet it's the case for many supersonic aircrafts in high altitude (at least with clean airframe)
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Old 10-10-2018, 02:32 PM   #13
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Quote:
Originally Posted by The Integrator View Post
Is it not the case that calibrated (or true) airspeed, TAS, is the IAS accounted for calibration errors, air density, temperature etc. and wind?

No. Calibrated airspeed is not true airspeed. CAS is IAS corrected only for instrument and position errors, not for air density, temperature, and wind.
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Old 10-10-2018, 10:40 PM   #14
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Alright, I think the main issue here is that I have assumed that CAS and TAS are the same, it seems I misread a few definitions. If that's the case then we are discussing a semantics issue and not anything really fundamental. If we take the definition as given by Fishbreath above then sure CAS is a better measurement to use. I think we are all fundamentally agreeing with each other but using different terminology for the same thing.

P.S. of course the real limit is temperature, this isn't my first rodeo :p , but that's not really the issue I'm getting at.
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Old 10-10-2018, 10:58 PM   #15
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Ok, so back to message #2: you were in over speed by 93kt.
Maybe the “punishment” is excessive, yet you have to want it to go that fast. Easy to avoid...
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Old 10-10-2018, 11:32 PM   #16
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You’re probably right. But how would you simulate the burning smell in DCS ?
By somehow making the hardware burn through

You'd probably never ever won't exceed Vne after that
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Old 10-11-2018, 09:47 AM   #17
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Wow "true" indicated airspeed sounds funny. It's like objective, subjective opinion.

I thought CAS was a more precise TAS. Now I know better.

I heard the Mig23 was limited to 2.3 Mach because the canopy would implode! I wonder who found that out?!
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