Vy vs Vx

[baobab72]

hello folks

i am a bit puzzled, maybe at one point in my career i knew this but know i dont really remember it, i guess that is what reviews are for!!
anyway i know for a fact that Vy the best rate of climb speed decreases with altitude while Vx the best climb angle speed increases with altitude.
What is the reason behind that?

many thanks even though i am not positive this is the right section where to post my question!!

baobab

[oggers]

Hi

Was subject of recent thread

[VLADKO]

Max angle/rate of climb speeds vary with altitude.True Air Seed(TAS) increases with altitude, that same Indicated Speed(IAS) you had at the sea level will not be enough to sustain given angle/rate of climb up at the high altitude. Wing senses only the TAS, however as pilots our primary reference is IAS.

[michelda]

Hi all,

could vx and vy be same speed? It is that possible?
How do they change with altitude?

Thanks
Michelda

[VLADKO]

could vx and vy be same speed?

Theoretically they should be @ same speed at the airplane's aboslute ceiling.

[Lyman]

At that altitude, "Quick" and "Fast" have the same meaning, eh?

[michelda]

Hi vladko,

And what about at mean sea level?
Is it possibile?

Michelda

[Tinstaafl]

Yes - if Sea Level happens to be the aircraft's absolute altitude. Although if that were the case you'd have greater worries such as trying to get airborne first.

[michelda]

Take a look of p2006 flight manual and you get a surprise......

[VLADKO]

michelda, I guess Tinstaafl answered the question for me Well that would be major engineering mishap!

[JIC]

Vladko, don't the wings senses pressure (IAS) and not speed (TAS) or am I confussed here?

And don't you have to increase your TAS to maintain the same IAS not the other way around or...?

[VLADKO]

Yes. Excuse me for phrasing it wrong. Wing senses pressure, and to maintain that same pressure at higher altitudes TAS has to be increased.