3 things that cause a stall?

[toothdr]

I agree with all that the only way to cause a stall is to exceed the critical angle of attack. However the "gist" of the question is probably what factors the pilot do or experience that would change the stall speed. Not a trick question at all IMHO. There are several of them listed below. I have probably forgot something, but this is an off the cuff answer. BTW, the FAA FSDO in this region is really expecting CFI initial canditidates to have a working knowledge of these factors. Here they are:
1. Bank angle ( Load factor)
2. CG location
3. Congiguation (flaps, gear)
4. Power Setting
5. Turbulence
6. Gross Weight
7. Ice
8. Other atmospheric conditions

 

[FlyJordan]

I dunno

 

[nosehair]

Wow! Avbug, Great humor (LMAO)

But actually, and I may be wrong*, but I seem to remember way, way back about "stalls at the one (and only one) critical angle of attack" is actually a little bit of a simplification. I think I remember airspeed, weight/cg, AND AoA. I think the AoA changes very slightly depending on airspeed and weight/cg. An insignificant amount, at least on small, slow speed airplanes, like less than one degree, but still has an effect which might be larger at much higher speeds.

Like, at really higher speeds, airflow seperation occurs at slightly lower angles of attack.

Anybody?

 

[FlyJordan]

Wow! Avbug, Great humor (LMAO)

But actually, and I may be wrong*, but I seem to remember way, way back about "stalls at the one (and only one) critical angle of attack" is actually a little bit of a simplification. I think I remember airspeed, weight/cg, AND AoA. I think the AoA changes very slightly depending on airspeed and weight/cg. An insignificant amount, at least on small, slow speed airplanes, like less than one degree, but still has an effect which might be larger at much higher speeds.

Like, at really higher speeds, airflow seperation occurs at slightly lower angles of attack.

Anybody?

That makes since and I think I remember hearing that before too.

 

[EMB170Pilot]

if not 3 things...is it 3 types of stalls?

1. Primary Stall

2. Secondary Stall

3. CrossControl Stall

???

 

[JAFI]

I tend to agree with the "Pixie Dust" explination, It reminds me of the "PFM" reason.

JAFI

(PFM - Pure Fu#$ing Magic)

 

[A Squared]

But actually, and I may be wrong*, but I seem to remember way, way back about "stalls at the one (and only one) critical angle of attack" is actually a little bit of a simplification. I think I remember airspeed, weight/cg, AND AoA. I think the AoA changes very slightly depending on airspeed and weight/cg.

You are probably right about airspeed, at a higher airspeed there would be a higher Reynolds number, and the behavior of turbulent vs laminar flow changes with the Reynolds number, so it would seem that this might also affect the stall characteristics. I'd be surprised if stalling AoA didn't change a little at high airspeeds.

The other (weight and cg) though, I do not agree with, all the air knows is how it is flowing around the airfoil. These factors obviously affect the stall *speed*, but I don't see any way that they would *directly* affect the stalling AoA. Now, I suppose you could say that weight and cg affect the stall speed, and if AoA is affected by airspeed, then there's a connection. However I think this sort of reasoning starts to get a little fuzzy.

A couple of people have mentioned that stall speed changes with Cg. I agree that it does, but htis got me to wondering how much if changes stall speed. SO, I did the math for a Cessna 180 (just happened to have a manual for that airplane handy) What I found was that at max gross weight, moving the cg from the aft limit to the forward limit (about 5 inches) increases the amount of force required from the horizontal stab by about 75 lb, so that shift forward would be approximately the same as addng 75 lb to the weight of the aircraft. Digging out Aerodynamics for Naval Aviators, I calculated that the additional weight would increase hte stall speed by about 3/4 of a knot. So yes it is true, cg affects stall speed, but for GA aircraft, the difference is pretty small.

 

[SiuDude]

if not 3 things...is it 3 types of stalls?

1. Primary Stall

2. Secondary Stall

3. CrossControl Stall

???

You forgot about the tertiary stall.

 

[VNugget]

Now, I suppose you could say that weight and cg affect the stall speed, and if AoA is affected by airspeed, then there's a connection.

You're naughty

 

[Stifler's Mom]

Came across this question on AviationInterviews.com.

What are the 3 things that cause a stall?

Am i missing something here?

A stall occurs when the ccritical Angle of Attack had been exceeded. I can't think of anythig else that causes a stall.

I guess i'm not sure what they are looking for with the question.

The question is worded wrong, it should read.....

What is a "stall"???

 

[FlyJordan]

The question is worded wrong, it should read.....

What is a "stall"???

Yup, I agree