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  #21  
Old 11-05-2013, 12:59 PM
Aryana Aryana is offline
 
Join Date: Jul 2012
Location: Western US
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Quote:
Originally Posted by flyeyes View Post
What he said.


The wing stalls (potentially causing a fatal loss of control) at the same AOA, independent of weight, density altitude, loading, bank angle, or any of a zillion other variables.

The only reason we have an "approach speed" is because it is a rough proxy for AOA. If you know your weight (or are flying an airplane where it doesn't vary much) you can pretty much calculate the airspeed where you will reach the critical AOA.

Bank angle really has nothing to do with stalling speed or "g-loading," except that you have to load the wing to maintain level (turning) flight and if you do the g-loading required can be calculated from the bank angle. This is independent of the airplane, and the exact same chart can be used for any aircraft.

It's possible to stall the airplane from level flight at any speed up to the maneuvering speed by loading the wing (pulling back on the stick). That's how snap rolls work, if you add some rudder at the same time so one wing stalls first.
You can even stall the plane when you are pointing straight down, perpendicular to the earth.

Inverted is also interesting. Pulling back to recover from the stall is weird at first.
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  #22  
Old 11-05-2013, 01:00 PM
sandifer sandifer is offline
 
Join Date: Jan 2007
Location: NC
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Quote:
Originally Posted by flyeyes View Post
It's possible to stall the airplane from level flight at any speed up to the maneuvering speed by loading the wing (pulling back on the stick). That's how snap rolls work, if you add some rudder at the same time so one wing stalls first.
Totally OT, but just wanted to point out that the idea that snap rolls are initiated by first stalling the airplane is widespread...and also wrong. This idea will lead to lots of terrible, slow, "buried" snap rolls that put unnecessary stress on the airplane. Proper snap rolls involve only a slight, but sharp AOA change, sufficient to cause the full rudder input to then stall one wing only. This is the key to the high rotation rate associated with snap rolls (along with a timely unloading of the stick after the snap breaks). Both wings do not stall, and the single wing stall is caused by the rudder input, not the elevator input. Yes, you can do what's essentially a "horizontal spin" by pulling the stick fully aft, stalling the airplane, and applying rudder, but it'll be so energy-killing, slow, and ugly that I would not classify it as a "snap roll". Sorry, I'm an acro nut to the bone.

And for those who might actually be interested - some snap clips I shot, showing the elevator inputs - which are fairly small compared to the full deflection range of the elevator: http://www.youtube.com/watch?v=g5et7jj2SiA

Last edited by sandifer : 11-05-2013 at 01:10 PM.
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  #23  
Old 11-05-2013, 01:12 PM
flyinga flyinga is offline
 
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"You can even stall the plane when you are pointing straight down, perpendicular to the earth."

I'm curious about this one. If you're going straight down and increase AOA toward a stall you will no longer be going straight down. What am I missing here?
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  #24  
Old 11-05-2013, 01:15 PM
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agirard7a agirard7a is offline
 
Join Date: Aug 2009
Location: Newport, RI
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Default Numbers

These were the numbers I was looking for Vso being 50 mph.
Which are a formula from the load factor.
Obviously the variable of weight and CG changes the Vso.
Flight testing with various weights and CG
would be great data to see in a POH.

30 Deg Bank ~ Vso*1.07 = Stall appx 54kts
45 Deg Bank ~ Vso*1.19 = Stall appx 60kts
60 Deg Bank ~ Vso*1.41 = Stall appx 71kts
75 Deg Bank ~ Vso*2.00 = Stall appx 100kts

Great info here. Thanks.
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  #25  
Old 11-05-2013, 01:18 PM
Aryana Aryana is offline
 
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Location: Western US
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Quote:
Originally Posted by flyinga View Post
"You can even stall the plane when you are pointing straight down, perpendicular to the earth."

I'm curious about this one. If you're going straight down and increase AOA toward a stall you will no longer be going straight down. What am I missing here?
Point the plane straight down and pull the stick back (or push forward towards the panel) in your lap hard. You'll continue to fall straight down and the wing will be stalled.

I agree with you though. If you point straight down and pull back without stalling the wing, the plane won't stall. I'm referring to something else entirely.

Last edited by Aryana : 11-05-2013 at 01:23 PM.
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  #26  
Old 11-05-2013, 01:23 PM
sandifer sandifer is offline
 
Join Date: Jan 2007
Location: NC
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Quote:
Originally Posted by Aryana View Post
How do you figure? Point the plane straight down and pull the stick back in your lap hard. You'll continue to fall straight down and the wing will be stalled.
Well, your flight path will change (shallow out a little) for as long as you hold the stick back, but the point still stands that you can stall the airplane in any attitude.
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  #27  
Old 11-05-2013, 01:25 PM
Aryana Aryana is offline
 
Join Date: Jul 2012
Location: Western US
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Quote:
Originally Posted by sandifer View Post
...but the point still stands that you can stall the airplane in any attitude.
That's my point. The rest is semantics, but you're observation is quite astute and noted. I think for the purposes of understanding or teaching someone how/when stalls can happen, that slight change in flight path is moot.

Last edited by Aryana : 11-05-2013 at 01:30 PM.
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  #28  
Old 11-05-2013, 02:18 PM
Toobuilder's Avatar
Toobuilder Toobuilder is offline
 
Join Date: Jul 2009
Location: Mojave
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Quote:
Originally Posted by agirard7a View Post
These were the numbers I was looking for Vso being 50 mph.
Which are a formula from the load factor.
Obviously the variable of weight and CG changes the Vso.
Flight testing with various weights and CG
would be great data to see in a POH.

30 Deg Bank ~ Vso*1.07 = Stall appx 54kts
45 Deg Bank ~ Vso*1.19 = Stall appx 60kts
60 Deg Bank ~ Vso*1.41 = Stall appx 71kts
75 Deg Bank ~ Vso*2.00 = Stall appx 100kts

Great info here. Thanks.

This is good info as a reference, but it doesn't even begin to scratch the surface in a practical sense. For example, it is possible to fly an approach at 60 in an RV-9 and roll into a 60+ degree bank without stalling the wing. The key to understanding why this is possible is far more valuable than memorizing a load factor chart.

?But this level of understanding is not going to come from debate on an Internet forum.
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WARNING! Incorrect design and/or fabrication of aircraft and/or components may result in injury or death. Information presented in this post is based on my own experience - Reader has sole responsibility for determining accuracy or suitability for use.

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