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Accelerated stalls

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rexinator(at)gmail.com
Guest

Posted: Wed Oct 31, 2007 6:38 am Post subject: Accelerated stalls

I decided to add a little to what Leonard has written. A wing stall 

occurs any time the Angle of Attack exceeds the lift a wing can generate 

regardless of airspeed. Accelerated stalls are demonstrated specifically 

by putting the airplane in a 60 degree bank at a specific airspeed 

(usually a slow cruise speed - Va?) while holding altitude. Properly 

done this creates a 2G force which we know all aircraft should be 

capable of sustaining normally. In this maneuver the aircraft should be 

in balance (ball centered otherwise you can snap roll into a spin) while 

the throttle is slowly decreased until stall entry is felt, then recover 

from the stall. It is a  maneuver taught to CFI pilots and is intended 

to impress on the pilot that an airplane can stall at higher than the 

airspeed published for straight and level flight. So don't try this 

without an instructor or maybe a competent aerobatic check pilot.

 In aerobatics the technique is used for snap rolls and other maneuvers 

where you want a dramatic and quick change of attitude. Both literally 

and figuratively. 



 So Leonard was taught part of a aerobatic technique which has probably 

saved his life. This is the kind of instruction we all should have.

ref: http://en.wikipedia.org/wiki/V_speeds

      http://www.auf.asn.au/groundschool/umodule2.html



-- 

Rex Hefferan

SE Colorado / K-II / 582-C / still waiting repairs





akflyer wrote:



 	  Quote: 	
		  



accelerated stall is getting the plane to stall at well over stall speed.. say in a cub or something of that nature that stalls at 40-45.. you think that flying along at 75 or 80 you are safe.  You see something on the ground that happens to catch your eye so you bank over and yank it around and fall out of the sky.  Put your plane into a nice steep bank and start hauling the stick in your lap slowly tightening your circle, add power to keep the speed up and keep pulling the stick just like you were intently looking at something on the ground.  Keep pulling the stick into your lap till you break and fall out of the sky..



A "moose hunter" stall is basically the same, but normally you are un-coordinated as you as stomping on the rudder trying to bring the nose around to so you can keep the "moose" you are looking at in view.  Normally guys are low and slow out spotting and we all know what happens when you stall uncoordinated.... you will spin and are to low to recover... alot of the time guys are low enough that they hit the ground at a fairly low speed and survive the impact... only to burn up in the fire afterward.  It kills ALOT of guys up here so my instructor hammered the hell out of me on both accelerated stalls and uncoordinated "moose hunter" stalls as he was well aware of the type of flying I would be doing the second he turned me loose to solo (the guy is a genius).  I can tell you with a straight face that he saved my life more than once as I was doing exactly what I was trained not to do, and caught it a split second before it broke into a full spin.  Had I not know what it felt l!

 ike (not just "incipient") and had it burned into my brain how to recover with very minimal loss of altitude I bet I would not be typing this right now.



Whew didn't mean to get that long winded, just a subject I don't think gets put across to student pilots the way it should..



--------

Leonard Perry

Soldotna AK

Avid &quot;C&quot; / Mk IV 

582 IVO IFA

Full Lotus 1260

95% complete





Read this topic online here:



http://forums.matronics.com/viewtopic.php?p=142902#142902

Michel

Joined: 10 Jan 2006
Posts: 966
Location: Norway

Posted: Wed Oct 31, 2007 7:46 am Post subject: Accelerated stalls

On Oct 31, 2007, at 3:36 PM, Rexinator wrote:

 	  Quote: 	
		   an airplane can stall at higher than the airspeed published for 

 straight and level flight. So don't try this without an instructor or 

 maybe a competent aerobatic check pilot.


	


If I am not mistaking, at 60 degrees coordinated bank you endure 2 Gs 

and your stall speed is increased by the square root of 2, or 1.4 times 

the published straight level flight. Does that make sense?



Cheers,

Michel Verheughe

Norway

Kitfox 3 - Jabiru 2200

_________________
Kitfox 3 - Jabiru 2200

akflyer

Joined: 07 May 2007
Posts: 574
Location: Soldotna AK

Posted: Wed Oct 31, 2007 8:27 am Post subject: Re: Accelerated stalls

 	  rexinator(at)gmail.com wrote: 	
		  I decided to add a little to what Leonard has written. A wing stall 

occurs any time the Angle of Attack exceeds the lift a wing can generate 

regardless of airspeed. Accelerated stalls are demonstrated specifically 

by putting the airplane in a 60 degree bank at a specific airspeed 

(usually a slow cruise speed - Va?) while holding altitude. Properly 

done this creates a 2G force which we know all aircraft should be 

capable of sustaining normally. In this maneuver the aircraft should be 

in balance (ball centered otherwise you can snap roll into a spin) while 

the throttle is slowly decreased until stall entry is felt, then recover 

from the stall. It is a  maneuver taught to CFI pilots and is intended 

to impress on the pilot that an airplane can stall at higher than the 

airspeed published for straight and level flight. So don't try this 

without an instructor or maybe a competent aerobatic check pilot.

 In aerobatics the technique is used for snap rolls and other maneuvers 

where you want a dramatic and quick change of attitude. Both literally 

and figuratively. 



 So Leonard was taught part of a aerobatic technique which has probably 

saved his life. This is the kind of instruction we all should have.

ref: http://en.wikipedia.org/wiki/V_speeds

      http://www.auf.asn.au/groundschool/umodule2.html



-- 

Rex Hefferan

SE Colorado / K-II / 582-C / still waiting repairs





akflyer wrote:



 	  Quote: 	
		  



accelerated stall is getting the plane to stall at well over stall speed.. say in a cub or something of that nature that stalls at 40-45.. you think that flying along at 75 or 80 you are safe.  You see something on the ground that happens to catch your eye so you bank over and yank it around and fall out of the sky.  Put your plane into a nice steep bank and start hauling the stick in your lap slowly tightening your circle, add power to keep the speed up and keep pulling the stick just like you were intently looking at something on the ground.  Keep pulling the stick into your lap till you break and fall out of the sky..



A "moose hunter" stall is basically the same, but normally you are un-coordinated as you as stomping on the rudder trying to bring the nose around to so you can keep the "moose" you are looking at in view.  Normally guys are low and slow out spotting and we all know what happens when you stall uncoordinated.... you will spin and are to low to recover... alot of the time guys are low enough that they hit the ground at a fairly low speed and survive the impact... only to burn up in the fire afterward.  It kills ALOT of guys up here so my instructor hammered the hell out of me on both accelerated stalls and uncoordinated "moose hunter" stalls as he was well aware of the type of flying I would be doing the second he turned me loose to solo (the guy is a genius).  I can tell you with a straight face that he saved my life more than once as I was doing exactly what I was trained not to do, and caught it a split second before it broke into a full spin.  Had I not know what it felt l!

 ike (not just "incipient") and had it burned into my brain how to recover with very minimal loss of altitude I bet I would not be typing this right now.



Whew didn't mean to get that long winded, just a subject I don't think gets put across to student pilots the way it should..



--------

Leonard Perry

Soldotna AK

Avid &quot;C&quot; / Mk IV 

582 IVO IFA

Full Lotus 1260

95% complete





Read this topic online here:



http://forums.matronics.com/viewtopic.php?p=142902#142902

  

	
	




on the bold... it used to be that you were taught full on fall out of the sky stalls and spins... The government in their infinite wisdom decided that this was not good and now you are only taught to recover at the first signs of a buffet not letting it get into a full stall.  I think this is a HUGE mistake as I think every pilot out there should be taught, at a bare minimum spin recovery techniques.  I bet alot of guys would still be around that spun in a kitfox if they knew without hesitation that they had to take the stick outa their lap to recover.  When you are low to the ground the first instinct is to try and pull the nose up...so they spin all the way in, when in fact, they could have recovered, change shorts then gone and had a beer to calm the nerves.

_________________
DO NOT ARCHIVE
Leonard Perry aka SNAKE
Soldotna AK
Avid "C" / Mk IV
582 (147 hrs and counting on the rebuild)
IVO IFA
Full Lotus 1450
#1 snake oil salesman since 1-22-2009

I would rather die trying to live, than to live trying not to die....

rexinator(at)gmail.com
Guest

Posted: Wed Oct 31, 2007 10:39 am Post subject: Accelerated stalls

I totally agree with Leonard that all pilots ought to know how to 

recover from a spin. Some pilots are afraid to be in unusual attitudes 

and perhaps would not become pilots if it were a requirement. That may 

be the reason it was decided it was better not to require such training 

and just the avoidance. Plus from what I was told there were more 

training crashes years ago when it was included.

 This way more certified pilots are created and it's been left up to the 

individual to advance their training. Probably more of a political 

decision than a wise one. I would encourage all pilots to learn how 

handle unusual attitudes or at least continue training and include 

commercial manuevers which would increase their feel for the aircraft 

they fly. However, probably spins are something only risk taking 

personalities want to persue, but it should not be that way. Properly 

done in the proper airplane it's safe and gentle, although seeing the 

ground fill the view out of your windshield while spinning will shock 

most people at first it's just something to get used to. Once you know 

what to expect and can correct it on your own it can become just another 

skill.



Michel Verheughe wrote:

If I am not mistaking, at 60 degrees coordinated bank you endure 2 Gs 

and your stall speed is increased by the square root of 2, or 1.4 times 

the published straight level flight. Does that make sense?



 Michel, the link below addresses the formula and states it to be 1.41 x 

Vs (the published straight level flight stall), but you are close enough.

 http://www.auf.asn.au/groundschool/umodule2.html#accel_stall



-- 

Rex Hefferan

SE Colorado / K-II / 582-C / still waiting repairs

akflyer wrote:



 	  Quote: 	
		  on the bold... it used to be that you were taught full on fall out of the sky stalls and spins... The government in their infinite wisdom decided that this was not good and now you are only taught to recover at the first signs of a buffet not letting it get into a full stall.  I think this is a HUGE mistake as I think every pilot out there should be taught, at a bare minimum spin recovery techniques.  I bet alot of guys would still be around that spun in a kitfox if they knew without hesitation that they had to take the stick outa their lap to recover.  When you are low to the ground the first instinct is to try and pull the nose up...so they spin all the way in, when in fact, they could have recovered, change shorts then gone and had a beer to calm the nerves.



--------

Leonard Perry

Soldotna AK

Avid &quot;C&quot; / Mk IV 

582 IVO IFA

Full Lotus 1260

95% complete



  




	


-- 

Rex Hefferan

SE Colorado / K-II / 582-C / still waiting repairs

Michel

Joined: 10 Jan 2006
Posts: 966
Location: Norway

Posted: Wed Oct 31, 2007 12:01 pm Post subject: Accelerated stalls

On Oct 31, 2007, at 7:37 PM, Rexinator wrote:

 	  Quote: 	
		   Michel, the link below addresses the formula and states it to be 1.41 

 x Vs (the published straight level flight stall), but you are close 

 enough.


	


Yes Rex, but I prefer to remember it as I wrote it: The square root of 

the Gs.

1.4, 1.41 or 1.414213562373 are all the square root of two, but at 

different resolutions.



Cheers,

Michel Verheughe

Norway

Kitfox 3 - Jabiru 2200



Do not archive

_________________
Kitfox 3 - Jabiru 2200

dave

Joined: 22 Sep 2006
Posts: 1382

Posted: Wed Oct 31, 2007 12:24 pm Post subject: Re: Accelerated stalls

Ok i recall talking about stalls and spins last year so I looked it up.  

Here you go this will save me from typing it all in again    



Cheers

http://forums.matronics.com/viewtopic.php?t=12156



dave(at)cfisher.com

Guest



 Posted: Fri Jul 28, 2006 7:27 pm    Post subject: Stall in a side slip   



--------------------------------------------------------------------------------

 

Good info there Dave. 



I have had spin training and I am not sure why it is not part of every 

flight test anymore. 

In Canada you only have to demonstrate spins for commerical and instructor 

rating. 

Private pilot license you used to have to as well. Why not now ? I have no 

idea. 



Personally I think all pilots should be tested on their flight reviews and 

on flight tests the following, 

Stalls,(stall on take off and approach) Spins ( fully developed) , Spirals, 

unusual attitudes and alot of slow fight. 

And of course recovery from all the above. 

And how about turning final at approach speed and going inverted ? There 

are deaths from the above every year that could be prevented. 



Dave  

 



dave(at)cfisher.com

Guest



 Posted: Fri Jul 28, 2006 10:00 pm    Post subject: Stall in a side slip   



--------------------------------------------------------------------------------

 

Wake turbulence is one way but you usually have enough separation on final 

.( I did have this one during IFR training under the hood) One scenario is 

if one was on base turning final and you are tight and wide. So you add 

more rudder and get more turn and more bank and use opposite aileron to 

lessen the bank and you are low and give aft stick then see what happens 

before you splat into ground. 



I land nearly fully stalled in Kitfox every time on grass, pavement snow,ice 

or water. I will take a high glideslope if landing behind a heavy and land 

beyond their touchdown. In Kitfox I rarely get behind heavies though. I 

most likely fly through my own wake turbulence more than anyone elses when 

horsing around  



And dead stick landings , certainly another good thing to learn. If you 

have not done any well you have not learnt yet. It can happen at anytime. 

i.e. bird strike,engine out , prop failure etc. Failure to leave your 

self an out will not leave you an "out" . 

Dave

_________________
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http://www.youtube.com/user/kitfoxflyer
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MichaelGibbs(at)cox.net
Guest

Posted: Wed Oct 31, 2007 7:38 pm Post subject: Accelerated stalls

Rex sez:



 	  Quote: 	
		  ...from what I was told there were more training crashes years ago 

when [spinning] was included.


	


When I went to get my tail wheel endorsement I started flying with a 

very old fella in an Aeronca Champ.  The first time I talked to him 

he said, "Well, first we'll get you familiar with the plane, go out 

and do some stalls and spins, then come back and work on landing and 

taking off."



I told him one of my instructors had demonstrated one once but that I 

had never done a spin myself.



He said, "You will today!"  And we did.  A whole bunch of them.  It 

was great fun, actually.



When I finished my Kitfox and had run through the gamut of power-on 

and power-off stalls I decided it was time to spin it.  My short-wing 

Model IV would only spin if you held the stick full aft and kept 

rudder into the turn.  If you relaxed either it would accelerate into 

a spiral dive.  Even then, I could only get it to stay in for about 

3/4 turn before it accelerated to flying speed on its own.



I think this was because it didn't have enough elevator authority to 

keep it at stall speed.  It was difficult to get a power-on stall to 

happen at all because it would run out of up elevator--you had to 

pull it sharply up to get a break to occur.



Mike G.

N728KF

Phoenix, AZ

Float Flyr

Joined: 19 Jul 2006
Posts: 2704
Location: Campbellton, Newfoundland

Posted: Thu Nov 01, 2007 6:53 am Post subject: Accelerated stalls

The flight school I trained with teaches mostly  commercial pilots.  It is part of their syllabus that they teach turning  stalls, straight forward departure stalls, arrival stalls and spins up to  insipid ( no more than four turns before correction).



I had done what I  was told was a hammerhead turn  (stall/spin with 180 degree turn only) but  the first time the instructor put me into a spin my heart skipped a  beat...  I hate roller coasters but I loved that.  It is so easy to  see that if you have never been there you can get into a lot of trouble a lot of  fast.  One thing is the first thing coming to most people would be to add  aileron control exaggerating the spin. 



Rules at the flight school  only allowed students to do spins with an instructor in the aircraft with  them.  Even the instructors were supposed to have a second with them while  doing spins.



I agree with teaching full spin recovery!  One less  surprise to have.



On the other hand I fly my Kitfox so far into the  envelope I doubt I'll ever have a spin.  I have yet to stall it.  Only  because I haven't had what I consider enough altitude for  safety. 



 

[img]cid:380144914(at)01112007-2DD1[/img]  

 Noel Loveys, RPP, AME intern

 Campbellton, Newfoundland, 

 Canada

 Kitfox Mod III-A, 582, B box, Ivo IFA

 Aerocet 1100s

 noelloveys(at)yahoo.ca (noelloveys(at)yahoo.ca)

 

 

 

 

 



[quote] > > accelerated stall is getting the plane to  stall at well

 over stall speed.. say in a cub or something of that  nature

 that stalls at 40-45.. you think that flying along at 75  or

 80 you are safe.  You see something on the ground that

  happens to catch your eye so you bank over and yank it around

 and fall  out of the sky.  Put your plane into a nice steep

 bank and start  hauling the stick in your lap slowly

 tightening your circle, add power  to keep the speed up and

 keep pulling the stick just like you were  intently looking at

 something on the ground.  Keep pulling the  stick into your

 lap till you break and fall out of the sky..

  > >

 > > A "moose hunter" stall is basically the same,  but

 normally you are un-coordinated as you as stomping on the

  rudder trying to bring the nose around to so you can keep the

 "moose"  you are looking at in view.  Normally guys are low

 and slow out  spotting and we all know what happens when you

 stall uncoordinated....  you will spin and are to low to

 recover... alot of the time guys are low  enough that they hit

 the ground at a fairly low speed and survive the  impact...

 only to burn up in the fire afterward.  It kills ALOT of  guys

 up here so my instructor hammered the hell out of me on  both

 accelerated stalls and uncoordinated "moose hunter" stalls  as

 he was well aware of the type of flying I would be doing the

  second he turned me loose to solo (the guy is a genius).  I

 can  tell you with a straight face that he saved my life more

 than once as I  was doing exactly what I was trained not to

 do, and caught it a split  second before it broke into a full

 spin.  Had I not know what it  fe!

  lt l!

 > >  ike (not just "incipient") and  had it burned into my

 brain how to recover with very minimal loss of  altitude I bet

 I would not be typing this right now.

 >  >

 > > Whew didn't mean to get that long winded, just a  subject

 I don't think gets put across to student pilots the way it  should..

 > >

 > > --------

 > > Leonard  Perry

 > > Soldotna AK

 > > Avid &quot;C&quot;  / Mk IV

 > > 582 IVO IFA

 > > Full Lotus 1260

  > > 95% complete

 > >

 > >

 >  >

 > >

 > > Read this topic online here:

  > >

 > > http://forums.matronics.com/viewtopic.php?p=142902#142902

  > >  

 > >

 > >

 >  >

 >





 on the bold... it used  to be that you were taught full on

 fall out of the sky stalls and  spins... The government in

 their infinite wisdom decided that this was  not good and now

 you are only taught to recover at the first signs of a  buffet

 not letting it get into a full stall.  I think this is a  HUGE

 mistake as I think every pilot out there should be taught,  at

 a bare minimum spin recovery techniques.  I bet alot of  guys

 would still be around that spun in a kitfox if they knew

  without hesitation that they had to take the stick outa their

 lap to  recover.  When you are low to the ground the first

 instinct is to  try and pull the nose up...so they spin all

 the way in, when in fact,  they could have recovered, change

 shorts then gone and had a beer to  calm the nerves.



 --------

 Leonard Perry

 Soldotna  AK

 Avid &quot;C&quot; / Mk IV

 582 IVO IFA

 Full  Lotus 1260

 95% complete





 Read  this topic online here:



 http://forums.matronics.com/viewtopic.php?p=142958#142958



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_________________
Noel Loveys
Kitfox III-A
Aerocet 1100 Floats

ruebd(at)skymail.csus.edu
Guest

Posted: Thu Nov 01, 2007 12:21 pm Post subject: Accelerated stalls

List:



	I will put my two cents worth in on this one, since I do

distinctly remember what my late instructor, one James Hackney, had to

say on the subject in the mid 1970's, when I was studying with him for

advanced ratings under the G.I. bill. 

	 He explained that an accelerated stall was produced by curving

the path of the wing, which then produced load factors greater than one.

Notice that nothing is said about the bank angle in this, and, indeed

doesn't need to be.  (The reference load factor of one, being generated

by flying straight and level in calm air.)  At first my engineering self

wanted this to be too simple an explanation, and I was searching for the

flaw in this simple explanation, but I still after all these years

cannot find any fault with Jim's brilliantly simple and therefore

elegant explanation.  

	If anyone out there can see a problem with this, please tell us

all.  



Duane Rueb, N24ZM



--

akanka(at)kiamichiwb.org
Guest

Posted: Thu Nov 01, 2007 1:14 pm Post subject: Accelerated stalls

If curving the path of an airfoil (wing) produces an accelerated stall, how

come helicopter airfoils (blades) produce lift?  They run in a continuous

circle (curved path), and the load factor on them change continuously due to

changing angle of attack in the plane of rotation to compensate for

dissymmetry of lift caused by the advancing half of the rotor system's

relative wind equaling the rotational speed plus the forward airspeed while

the retreating half's relative wind is the rotational speed minus the

forward airspeed.



FAA AC 61-67C with Change 1, Subject: Stall and Spin Awareness Training, is

located online at

http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgAdvisoryCircular.nsf/0/

543ceffb938738a28625736100575511/$FILE/AC%2061-67C%20%20CHG%201.pdf 



 For what it's worth, FAA AC No: 61-67C, paragraph 104 is quoted below:



104. TYPES OF STALLS. Stalls can be practiced both with and without power.

Stalls should be

practiced to familiarize the student with the aircraft's particular stall

characteristics without putting

the aircraft into a potentially dangerous condition. In multiengine

airplanes, single-engine stalls

must be avoided. Descriptions of some different types of stalls follows:



a. Power-off stalls (also known as approach-to-landing stalls) are practiced

to simulate

normal approach-to-landing conditions and configuration. Many stall/spin

accidents have occurred

in these power-off situations, such as crossed control turns from base leg

to final approach

(resulting in a skidding or slipping turn); attempting to recover from a

high sink rate on final

approach by using only an increased pitch attitude; and improper airspeed

control on final approach

or in other segments of the traffic pattern.

b. Power-on stalls (also known as departure stalls) are practiced to

simulate takeoff and

climbout conditions and configuration. Many stall/spin accidents have

occurred during these phases of flight, particularly during go-arounds. A

causal factor in such accidents has been the pilot's

failure to maintain positive control due to a nose-high trim setting or

premature flap retraction, and

during short field takeoffs has also been a causal accident factor.



c. Accelerated stalls can occur at higher-than-normal airspeeds due to

abrupt and/or excessive

control applications. These stalls may occur in steep turns, pullups, or

other abrupt changes in

flightpath. Accelerated stalls usually are more severe than unaccelerated

stalls and are often

unexpected because they occur at higher-than-normal airspeeds.



John Hart 

--

wingnut

Joined: 11 Jan 2006
Posts: 356

Posted: Thu Nov 01, 2007 1:52 pm Post subject: Re: Accelerated stalls

What does it mean to curve the path of a wing? 



The best explanation of the physics of a stall that I know focuses on angle of attack which is the angle of the incidence of the airfoil relative to the direction its moving through the air. In fact, isn't that what stall/lift reserve indicators actually measure? If your angle of attack gets too high the flow of air separates from the top of the airfoil and it looses it's ability to produce lift. The same principal applies to helicopter blades as well.



 	  Quote: 	
		  He explained that an accelerated stall was produced by curving 

the path of the wing, which then produced load factors greater than one.

_________________
Luis Rodriguez
Model IV 1200
Rotax 912UL
Flying Weekly
Laurens, SC (34A)

wingnut

Joined: 11 Jan 2006
Posts: 356

Posted: Thu Nov 01, 2007 2:01 pm Post subject: Re: Accelerated stalls

On the other hand, while talking about the physics behind a stall might be interesting and maybe even enlightening, I think it's still worth talking about the various situations where a high angle of attack occurs. After all, people might not make the connection in their minds between what they they're doing and the aerodynamic consequences. 



Steep turns during slow flight seem to me like one of the more popular ways that pilots induce high angles of attack. I read posts on this very forum from time to time that seem to advocate the practice.

_________________
Luis Rodriguez
Model IV 1200
Rotax 912UL
Flying Weekly
Laurens, SC (34A)

ruebd(at)skymail.csus.edu
Guest

Posted: Thu Nov 01, 2007 2:18 pm Post subject: Accelerated stalls

What it means to curve the path of the wing is to cause it to curve by

first banking and turning (a curve) or by abruptly causing it to climb,

(a curve), and this is true for both a positive curve or a negative one.

As long as there is a curved path, the load factor will be other than

one.  With a negative curve established from straight and level flight,

the load factor will first be reduced below one.  But the key to how

much load factor is in how much of a curve, and what the airspeed is.

But the path needs to curve for this to happen.  Even in turbulence

where you are attempting straight and level flight, the air that causes

you to experience high and low load factors is causing a curved path of

the aircraft.  Note that nothing is said about angle of attack, but of

course it follows that this will be changing to compensate for the

curved path involved when the load factor deviates from one.  



Duane Rueb, N24ZM



--

wingnut

Joined: 11 Jan 2006
Posts: 356

Posted: Thu Nov 01, 2007 3:24 pm Post subject: Re: Accelerated stalls

OK. Now that I understand curving the path of a wing meens, I'd have to say that this doesn't seem to me like a good description of what is going on in a stall at all. An airfoil can be stalled with no 'curve' to it's direction of travel at all and a load factor of even less than 1. Consider this, if you kill your engine, the airplane will begin to slow down. As it slows down and begins to loose lift, you can pull back slowly to maintain a strait flight (ie: no curve). Eventually, the airplane is going to stall. Guess what you have when the airplane finally stalls? You guessed it, a high angle of attack.



 	  Quote: 	
		  What it means to curve the path of the wing is to cause it to curve by first banking and turning (a curve) or by abruptly causing it to climb, 

(a curve), and this is true for both a positive curve or a negative one. 

As long as there is a curved path, the load factor will be other than 

one. With a negative curve established from straight and level flight, 

the load factor will first be reduced below one. But the key to how 

much load factor is in how much of a curve, and what the airspeed is.

_________________
Luis Rodriguez
Model IV 1200
Rotax 912UL
Flying Weekly
Laurens, SC (34A)

rexinator(at)gmail.com
Guest

Posted: Thu Nov 01, 2007 3:51 pm Post subject: Accelerated stalls

I'm not so sure if describing an acellerated stall as curving the path 

of the wing works as well in text form. If you are showing what you mean 

with hand gestures or a model aircraft it would work better. Which is 

always true describing flight, a visual image helps greatly. Here's 

another attempt.



 Any stall occurs when Angle of Attack referenced to relative wind 

exceeds the lift capability of the airfoil.



 I used "airfoil" here to allow the statement to apply to elevators and 

propellers as well. Seems better to me. No reference to bank angle there 

and as you said it doesn't need to be. A stall can occur regardless of 

the path of flight, but gravity and bank angle effects the lift capacity 

(G load) as compared to wings level. Thus the practice of using a 60 

degree bank angle. Lift capacity is reduced in the 60 degree 

accellerated stall because of the lift vector in relation to gravity so 

that structual damage is not possible at the speeds used.

 I should note that it used to be the FARs allowed certain training 

manuevers with a CFI that would normally fall under the definition of 

"aerobatic flight" without the requirement of parachutes. An 

accellerated stall without a CFI would have been defined as a aerobatic 

maneuver. I'm not sure what the regs say now.

Rex Hefferan



Rueb, Duane wrote:



 	  Quote: 	
		  



List:



	I will put my two cents worth in on this one, since I do

distinctly remember what my late instructor, one James Hackney, had to

say on the subject in the mid 1970's, when I was studying with him for

advanced ratings under the G.I. bill. 

	 He explained that an accelerated stall was produced by curving

the path of the wing, which then produced load factors greater than one.

Notice that nothing is said about the bank angle in this, and, indeed

doesn't need to be.  (The reference load factor of one, being generated

by flying straight and level in calm air.)  At first my engineering self

wanted this to be too simple an explanation, and I was searching for the

flaw in this simple explanation, but I still after all these years

cannot find any fault with Jim's brilliantly simple and therefore

elegant explanation.  

	If anyone out there can see a problem with this, please tell us

all.  



Duane Rueb, N24ZM

  




	


-- 

Rex Hefferan

SE Colorado / K-II / 582-C / still waiting repairs

avidfox

Joined: 03 Apr 2007
Posts: 87

Posted: Thu Nov 01, 2007 4:13 pm Post subject: Accelerated stalls

§ 91.303   Aerobatic flight. 

No person may operate an aircraft in aerobatic flight— 

(a) Over any congested area of a city, town, or settlement; 

(b) Over an open air assembly of persons; 

(c) Within the lateral boundaries of the surface areas of Class B, Class C, Class D, or Class E airspace designated for an airport; 

(d) Within 4 nautical miles of the center line of any Federal airway; 

(e) Below an altitude of 1,500 feet above the surface; or 

(f) When flight visibility is less than 3 statute miles. 

For the purposes of this section, aerobatic flight means an intentional maneuver involving an abrupt change in an aircraft's attitude, an abnormal attitude, or abnormal acceleration, not necessary for normal flight. 

    § 91.307   Parachutes and parachuting. 

(c) Unless each occupant of the aircraft is wearing an approved parachute, no pilot of a civil aircraft carrying any person (other than a crewmember) may execute any intentional maneuver that exceeds— 

(1) A bank of 60 degrees relative to the horizon; or 

(2) A nose-up or nose-down attitude of 30 degrees relative to the horizon. 

(d) Paragraph (c) of this section does not apply to— 

(1) Flight tests for pilot certification or rating; or 

(2) Spins and other flight maneuvers required by the regulations for any certificate or rating when given by— 

(i) A certificated flight instructor; or 

(ii) An airline transport pilot instructing in accordance with §61.67 of this chapter. 

 



  [quote][b]

nail13zg(at)centurytel.ne
Guest

Posted: Thu Nov 01, 2007 4:17 pm Post subject: Accelerated stalls

Curves and airspeed, etc. etc. I think we are  missing a fundamental lesson here on stalls. An airplane, any airplane, stalls  when the wing's designed critical angle of attack is exceeded. For most general  aviation airplanes this angle is about 18 degrees. When this angel of attack is  exceeded, regardless of airspeed, weight, configuration, attitude, or  anything else you can think of, the wing stalls. 

  

 Trey Moran

  

    [quote][b]

dgolden(at)golden-consult
Guest

Posted: Fri Nov 02, 2007 12:31 pm Post subject: Accelerated stalls

Rueb, Duane wrote:

 	  Quote: 	
		   

 

 List:

 

 	I will put my two cents worth in on this one, since I do

 distinctly remember what my late instructor, one James Hackney, had to

 say on the subject in the mid 1970's, when I was studying with him for

 advanced ratings under the G.I. bill. 

 	 He explained that an accelerated stall was produced by curving

 the path of the wing, which then produced load factors greater than one.

 Notice that nothing is said about the bank angle in this, and, indeed

 doesn't need to be.  (The reference load factor of one, being generated

 by flying straight and level in calm air.)  At first my engineering self

 wanted this to be too simple an explanation, and I was searching for the

 flaw in this simple explanation, but I still after all these years

 cannot find any fault with Jim's brilliantly simple and therefore

 elegant explanation.  

 	If anyone out there can see a problem with this, please tell us

 all.  

 


	


After I left the service, I was training at a Part 141 school. They

taught accelerated stalls by stalling right after recovering from a

departure stall. This was in a Cherokee 140 and was quite dramatic.



Dennis

-- 

Dennis Golden

Golden Consulting Services, Inc.

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