Is Vne a true airspeed or a indicated airspeed?

[ackattacker]

Mne is sort of like crossing a bulldog with a schitzu...

A Bullschitz?

 

[avbug]

Harry and Lloyd weren't as dumb as folks thought. Their existence was one of profound, but sublime wisdom.

 

[VNugget]

and altitude and pressure...density altitude, for which temperature is part of the equation.

Nope... it's dependent on temperature only. (http://exploration.grc.nasa.gov/education/rocket/snddrv.html)

 

[mzaharis]

Compressibility effects are a function of air density (temperature and altitude), airspeed, shape, and angle of attack

But ultimately, are you not using density and airspeed to determine the mach number? For a given shape and angle attack, don't compressibility effects start at relatively constant mach number?

and altitude and pressure...density altitude, for which temperature is part of the equation.

Actually, speed of sound is ultimately density and pressure independent. You can use the equation:

Speed of sound (meters/sec) = 331.4 + .6 T (in celsius)

You can write an equation for the speed of sound that uses density, but when you use the Ideal Gas law (PV=NRT, alternatively P="rho"*r*T) other terms cancel out, and you're only left with temperature. This is done by the equation

Speed of sound = SQRT("bulk modulus"/density)

The calculation of "bulk modulus" is a pressure over density calculation. When you plug in the ideal gas law, you can cancel out density and pressure, and you're only left with temperature.

Here's the full derivation (see the "Speed in ideal gases and in air" section in the following link):

http://en.wikipedia.org/wiki/Speed_of_sound

I know that Wikipedia is not always respected, so here it is from NASA, without all the derivation:

http://www.grc.nasa.gov/WWW/K-12/airplane/sound.html

Vne, Mmo. Never Exceed Speed, Maximum Mach Operating limit. Mne is sort of like crossing a bulldog with a schitzu...

A Bullschitz?

Thanks. I never flew a mach-limited aircraft (see to the left). ;-). I must admit that my limited knowlege is more from the theoretical side than the operational.

Actually, we just got a shi-tzu - seeing it crossed with a bulldog would be a truly, ahem, jarring visual. Must admit I missed the wordplay at first.

 

[Axel]

You read it off the airspeed indicator.

 

[Gorilla]

Good discussion. It was always nice when flying certain small .mil jets to not have to worry too much about these speeds. 600 to 800 knots IAS not a problem down low... except you get a new cookie tossed into the mix, high-Q, where you get heating and pressure damage to an airframe.

We had a new guy take a clean, newly painted (and decal'ed) F-15 up and proceeded to burn some of the paint, and all the decals, off during a high mach run.

Without looking it up, I believe the throttle-down of the space shuttle after launch is to avoid this high-Q danger while in the denser atmosphere. When it gets into the thinner air, that's when you hear "Go for throttle-up."

With most transports, you get a paired Velocity/Mach NE speed, such as 340 / 0.84, meaning whichever occurs first, that's your limit.

 

[Rally]

Speed of sound not taken into account. If Vne or Vmo is indicated and not true way do aircraft such as a king air 200 who barely get above 200 need a barberpole?

 

[MAJIC9]

It is TAS... not IAS.

What seems to be disregarded in some of these answers is sure you can use IAS if that will keep you within airplane's envelope.. or if it doesn't, they put a barber pole...

edit:

Just to add, per article, flutter is NOT a function of dynamic pressure, but velocity of air passing by. It's the velocity of the excitation force that is of prime concern. As they mention in the article, what brought down Tacoma Narrows bridge wasn't some gale force wind.. it was "only" about 42 mph.. but it was just the right speed to induce flutter in the bridge... you saw the rest on the video

 

[Rally]

So Vne is TAS?

Its gonna take years for me to understand this one.

 

[FL420]

A Bullschitz?

Thanks! I needed that!