Author Topic: What is a STALL?  (Read 1458 times)

Offline Terror

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What is a STALL?
« on: January 22, 2003, 10:19:11 AM »
As a side note to the "AHII FM" thread.  Some people seem to have a misunderstanding of what a stall is....  (and I didn't want to hijack the thread.)

A Stall can occur at any speed, attitude, or altitude .  A stall is defined as "the angle of attack exceeding the critical angle of attack of the wing."  A roll or spin induced from a stall is an effect of one wing stalling before the other.  If you stall both wings at the same time (ie. you are "coordinated") there will be no roll or spin, the nose will drop and you will gain airspeed.  As you get slower, it is easier to force the angle of attack past the critical angle of attack, because at slower speeds, you need more angle of attack to create enough lift to keep you airborne.

An "Accellerated Stall" is just a stall that is "accellerated" due to control surface inputs (Elevator, aileron, or rudder) at speed.  A "snap roll" is an example of a "accelerated stall" manuever.  Essentially, the pilot, through control inputs, stalls one wing before the other to maximize a roll manuever.

Each plane has it's unique stall characteristics.  This is due mostly to differences in weight and balances, engine torque, p-factor, slipstream, gyroscopic precession, and wing shape.  But all planes in AH can and will stall, all can spin.  Just some are more forgiving in the amount of time it takes to recover a bad stall.

Terror

PS.  Just in case:  Angle of Attack is the angle of "wind" to the chord of the wing.  Critical Angle of Attack is the angle at which the "wind" can no longer flow smoothly over a wing.

Offline ra

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What is a STALL?
« Reply #1 on: January 22, 2003, 10:47:25 AM »
Good explaination.  But some people already understand stalls but question the tameness of AH stalls.  You can usually recover from an AH stall by just letting go of the stick.  This was true for some WWII fighters, but not all.  Some were very difficult to recover from, like the P-40.

ra

Offline Terror

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What is a STALL?
« Reply #2 on: January 22, 2003, 11:22:26 AM »
Quote
Originally posted by ra
Good explaination.  But some people already understand stalls but question the tameness of AH stalls.  You can usually recover from an AH stall by just letting go of the stick.  This was true for some WWII fighters, but not all.  Some were very difficult to recover from, like the P-40.

ra


Some planes are very rough to recover from, if you let the stall get past the "incipient spin" stage.  (Though, just a tad bit of opposite rudder just as you "feel" the spin start almost always stops it from turning into a full spin.)  Tough planes to recover a "full" spin that come to mind:  F4u-1, YAK9t, TA152, SPIT14, and the P40.  Though almost all the planes will come out of a spin with opposite rudder and forward stick, just gotta be careful that you don't over-recover and invert the spin.

The only time I have read about really difficult recoveries in most WWII planes was when CG was shifted backwards due to an aft tank being full.

Terror

Offline CyranoAH

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What is a STALL?
« Reply #3 on: January 22, 2003, 11:58:53 AM »
Thought you'd like this video. I posted it some time ago, but it's relevant to the topic, so here it is.

http://casal.upc.es/~danig27/barrena.wmv

It's a spin recorded from a CAP-10B aerobatic trainer.

Three full rotations with a loss of altitude of 1000 ft.

Daniel

Offline WldThing

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What is a STALL?
« Reply #4 on: January 22, 2003, 12:41:56 PM »
I can remeber a Stall that i did a WHILE back.  One of the strangest to date...

I went up after a con and when i stalled back my cockpit was turned towards the ground and there was no way of getting out of it.  I am decent when it comes to stall recovery but this time it was impossible.  Was pretty cool tough :)

Plane was a P51.. I stalled her out at about 45 MPH when it happened.

Offline mosgood

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What is a STALL?
« Reply #5 on: January 22, 2003, 12:52:47 PM »
That's when my girlfriend says " I have a headache"

Offline Shane

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What is a STALL?
« Reply #6 on: January 22, 2003, 02:26:06 PM »
Quote
Originally posted by ra
Good explaination.  But some people already understand stalls but question the tameness of AH stalls.  You can usually recover from an AH stall by just letting go of the stick.  This was true for some WWII fighters, but not all.  Some were very difficult to recover from, like the P-40.
ra


says who?  from all i understand about teh p-40 is that it was very easy to recover from a stall - all you had to do was let go of the stick.

the hogs and ponys, otoh...
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Offline ccvi

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What is a STALL?
« Reply #7 on: January 22, 2003, 02:28:20 PM »
From http://www.hitechcreations.com/forums/showthread.php?s=&threadid=74518&pagenumber=2


Quote
Originally posted by F4UDOA
I have run several test today. The question I have about the FM is what do you consider a stall? The AH FM tends to mush forward and loose altitude before stalling or wing break. I believe the stall begins when you can no longer hold the horizon. Correct?


Quote
Originally posted by hitech
When you can no longer maintain 0 decent.

HiTech



Or try this definition:
http://www.monmouth.com/~jsd/how/htm/vdamp.html#sec-stall-definition

Offline hitech

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What is a STALL?
« Reply #8 on: January 22, 2003, 02:34:47 PM »
Terror is 100% correct with his definition of a stall infact it's almost directly out of the FAR/AIM manual.

What im refering to is whats normaly called stall speed.


HiTech

Offline Karnak

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What is a STALL?
« Reply #9 on: January 22, 2003, 03:35:34 PM »
According the RAF tests I am familiar with the Spitfire Mk XIV had to be held in a stall otherwise it would recover itself.
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Offline GPreddy

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What is a STALL?
« Reply #10 on: January 22, 2003, 04:42:23 PM »
Quote
Originally posted by WldThing
I can remeber a Stall that i did a WHILE back.  One of the strangest to date...

I went up after a con and when i stalled back my cockpit was turned towards the ground and there was no way of getting out of it.  I am decent when it comes to stall recovery but this time it was impossible.  Was pretty cool tough :)

Plane was a P51.. I stalled her out at about 45 MPH when it happened.


WldThing I believe that was probably an inverted flat spin. It is possible to recover a pony from this but it takes a lot of altitude. The procedure is quite similar to the recovery process of an F16 in a deep stall.

1) release controls
2) throttle to idle
3) rudder opposite to yaw direction
4) Override (in the P51 you dont have a manual pitch override)
5) cycle stick in phase to nose oscillation or pitch bobbing

When the nose stays down and airspeed starts to climb your out. Dont get heavy handed again :)

Quote
Originally posted by Shane
says who?  from all i understand about teh p-40 is that it was very easy to recover from a stall - all you had to do was let go of the stick.

the hogs and ponys, otoh...


Stall maybe but this beast would kill in a low altitude spin. Ive forgotten who the test pilot was but he was sent to Curtiss by Chenault to try the P40 out before leaving for Burma and eventual assignment to the Flying Tigers. During his first flight he spun the P40 from under 3k and only recovered at about 20ft. It was written in the book up until that time that a spin that low was impossible to recover from. It was he that learned you had to fly the plane out and that normal spin recovery methods would not work. I want to say Don Anderson or maybe Tex Hill. Maybe WideWing knows.

Offline mason22

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What is a STALL?
« Reply #11 on: January 22, 2003, 04:44:22 PM »
I think we also take it for granted what happens in nature vs. trying to repeat that in code. That's gotta blow some minds.

nice post Terror.

Offline rv6

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What is a STALL?
« Reply #12 on: January 23, 2003, 09:22:23 AM »
I think it'd all become much clearer and remove any misconceptions, if you'd purchase 1 hr of "spin training" in a Super-Decathlon (or other inline aerobat).

Stalling a wing in uncoordinated flight, angle of attack, etc,, will take on a whole new meaning (other than clinically written descriptions) when that nose snaps over, you float off the seat only held in by the harness, and the ground fills the windscreen, as it whirls in a living collaidascope of blur'd colors..  The altimiter unwinding like the crazy clock in "Alice in Wonderland" on drugs..

Well worth the $150.  You'll have no more question about AOA, Stalls, etc.

:-)

Offline Bodhi

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What is a STALL?
« Reply #13 on: January 23, 2003, 09:34:53 AM »
RV-6, spin a T-6 sometime...  you will learn the true meaning as to why they placard the darn beasty with "Intentional Spins Prohibited"  It is one hair and blood pressure raising ride.
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Offline hitech

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What is a STALL?
« Reply #14 on: January 23, 2003, 09:35:11 AM »
Spinning the SD is great fun, snaps are wild. Got where I could come out withing 5 degs of heading with 3 turn spins.

Not looking forward to inverted spin training thow, but want to get it under my belt for safty.

HiTech