How does Vne speed vary with altitude?

Landis

Landis

Well-Known Member
I just took my ATP written and I suppose I should just be happy that I passed. But a couple questions that I was asked weren't in my study material (Gleim and ASA books and ASA Prepware). I managed to find one of the questions that I hadn't seen before in the ASA book under the rotorcraft category. But I did the Airplane-135 test. So I thought I'd ask it here as it applies to airplanes.

How does Vne speed vary with altitude?

A–Varies directly with altitude.
B–Remains the same at all altitudes.
C–Varies inversely with altitude.
 
I don't know ... the Barber Pole moves accordingly ...

Remember ... the Barber Pole isn't a limit ...












It's a Goal!
 
I would assume it would decrease due to the lower air density, but assuming is never a wise undertaking in aviation...especially when the FAA is involved.
 
As you climb, it goes up then it comes back down.

...but I think that has to do more with bird strikes on the window than the airframe itself.

Why? I dunno. I stop at the red line.

-mini
 
Landis said:
How does Vne speed vary with altitude?

A–Varies directly with altitude.
B–Remains the same at all altitudes.
C–Varies inversely with altitude.
Click to expand...

ASA has the answer as C with an explanation detailing why this is so in "most helicopters". The source they cite is FAA-H-8083-21, the Rotorcraft Flying Handbook. And the retreating blade stall forward speed limitation on a rotorcraft coming at a lower speed with a higher altitude makes perfect sense.

This question, however, is on the FAA website when you download sample ATP airplane questions. So it's not something I can blame on CATS.

Given they didn't ask about TAS or IAS or Mmo or anything to that effect, I wonder how Vne for an airplane would be considered to vary (or not) with altitude. Can anyone lead me to an FAA source of information saying that Vne varies (or doesn't) with altitude?
 
minitour said:
As you climb, it goes up then it comes back down.

...but I think that has to do more with bird strikes on the window than the airframe itself.

Why? I dunno. I stop at the red line.

-mini
Click to expand...

You should know these things mini. What if you need the lift equation or the 9 factors of Vmc one day to save the day? :beer:
 
400A said:
Admitting the problem is the first step....
:D
Click to expand...
20090902-iceman.jpg


...that's how I roll. :rawk:

-mini
 
Landis said:
C–Varies inversely with altitude.
Click to expand...

I've never seen one that didn't decrease with altitude when it wasn't constant. I presume this is a flutter issue, which tends to be related to high TAS and reduced damping due to a decrease in air density.

The rotorcraft issue appears to be due to a retreating blade stall.
 
I think that it would have to depend on the airframe, and more specifically on what specific part of the aircraft is driving the limit. In general though, since air loads pretty much remain constant with IAS, then Vne should also remain constant (until you get high enough that Mach effects take over, that is) if it is listed in indicated.
 
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