3 things that cause a stall?

[wmuflyguy]

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.

 

[VNugget]

Maybe they are looking at a deeper level... like deenergized boundary layer, adverse pressure gradient, etc.

 

[mattpilot]

perhaps they are looking for simple obvious things...?

Like Low air speed, Abrubt control maneuvers, and ...whateveryacanthinkof

 

[qmaster3]

They are not looking for departure, approach, and trim? Too me those are types, but maybe they need to re-phrase the question.

 

[mattpilot]

Maybe its a trick question. Perhaps they want to find out if you BS your way through the answer by coming up with wierd stuff.

If i were at an interview and i got that question, i'd probably go "I'm sorry, 3?" and then go with the explanation wmuflyguy gave. Then say, "Unless you ment three flight conditions.... then yadaya".

 

[qmaster3]

It's a comair question I believe. You should post something on regionals, and see if any Comair guys bite.

 

[bobbysamd]

Stalls

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

Nor can I. Exceeding the critical AOA is the only cause for a stall that I learned and taught.

??

 

[paulsalem]

perhaps they are looking for simple obvious things...?

Like Low air speed, Abrubt control maneuvers, and ...whateveryacanthinkof

You can stall at any airspeed and at any attitude. Its all about the Angle of Attack

 

[mattpilot]

You can stall at any airspeed and at any attitude. Its all about the Angle of Attack

yes i know that.... but things that can cause you to exceed the AoA are some of the conditions i listed....


Edit: i still think its a trick question

 

[JRSLim]

I'm with Vnugget, they must be looking for more detailed aerodynamic explainations -- the flow seperation moving forward as the critical angle of attack is reached, causing the low pressure effect above the wing to go away.. good question to study up on

 

[minitour]

...
Edit: i still think its a trick question

I'm with you on this one

 

[Tinstaafl]

Maybe they're after what can affect the critical angle? Things like damage, ice, LED/TEDs.

 

[avbug]

Many things cause a stall, but clearly three are at the top of the list:


1. Any woman asking if she looks fat in a dress. Gauranteed source of stalling, stuttering, stammering, and freezing, which occurs when one is relegated to fighting the dog for a piece of the blanket in his leaky backyard house.

2. Arriving on the freeway behind the LA chapter of Hells Angels, one's horn gets stuck blaring. One attempts to extricate one's self from the situation, and outrun the bikers. One's car bogs down; gauranted to stall at a time like this.

3. Drinking caffiene and flying for any period of time, particularly over barren country where no chance of landing is offered. Exiting the airplane enroute to the gentleman's (or ladies) facility provides the appearance of a cross between a bad day at the superbowl and a delicate rendition of the nut cracker meets swann lake, while humming "anchor's aweigh" in falsetto and uttering obscenities to the end of "get the #!!@X?!!X@# out of my way!" This act, enroute from the cockpit to the restroom, out of deference to the ultimate destination when one leave the cockpit, is called quite simply, "stalling."


Angle of attack is far down the list. Airplanes stall when surface friction divests the wing boundary layer surface of it's requisite coating of pixie dust. The soloution involves counting to ten in latin and eating a roasted turnip while praying for change. It could work.

 

[PropsForward]

1. Any woman asking if she looks fat in a dress. Gauranteed source of stalling, stuttering, stammering, and freezing, which occurs when one is relegated to fighting the dog for a piece of the blanket in his leaky backyard house.

Talk about needing to be ready with the emergency procedures, a stall in this situation is almost always fatal if your not ready and paying proper attention.

 

[msuspartans24]

Trick question

 

[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