Serious wing drop at stall
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wing tip stall
what union, what are you saying?
'when you put flap down you are changing Cl over that part of the wing the flaps affect. you have in fact two different wings on the a/c.an inboard high lift section and an otboard standard section. on a cessna you have two other high lift considerations the slots above the flaps nd the sheer size of the flap in relation to wing area. what this results in is an inboard wing section that will remain unstalled with a normal approach into the stall. there will be a wing drop because the tip must stall first,whichever one goes first goes first. the large wing drop is due to the very large change in Cl across the breadth of the wing coupled to the unstalling of opposite tip.'
When lowering flap you increase the Aof A of that section of the wing. The wing tip is unchanged by this action. The wing root will, therefore, stall at an earlier stage when the a/c pitch is increased further and even sooner than the wing tip in this condition than when the wing is clean. The a/c is of cause less laterally stable with flap lowered. There is no vortice control to the edges of flap unlike a wing tip. The outflow will become turbulent. On lowering aileron you must also increase the angle of attack of the wing tip. The combination of lowering aileron together with turbulent airflow must cause a likelyhood of an unwanted wing tip stall.
The advice comes to mind, "engage brain before opening mouth"
'when you put flap down you are changing Cl over that part of the wing the flaps affect. you have in fact two different wings on the a/c.an inboard high lift section and an otboard standard section. on a cessna you have two other high lift considerations the slots above the flaps nd the sheer size of the flap in relation to wing area. what this results in is an inboard wing section that will remain unstalled with a normal approach into the stall. there will be a wing drop because the tip must stall first,whichever one goes first goes first. the large wing drop is due to the very large change in Cl across the breadth of the wing coupled to the unstalling of opposite tip.'
When lowering flap you increase the Aof A of that section of the wing. The wing tip is unchanged by this action. The wing root will, therefore, stall at an earlier stage when the a/c pitch is increased further and even sooner than the wing tip in this condition than when the wing is clean. The a/c is of cause less laterally stable with flap lowered. There is no vortice control to the edges of flap unlike a wing tip. The outflow will become turbulent. On lowering aileron you must also increase the angle of attack of the wing tip. The combination of lowering aileron together with turbulent airflow must cause a likelyhood of an unwanted wing tip stall.
The advice comes to mind, "engage brain before opening mouth"
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Homeguard i have to say if you are an instructor you should keep that theory very much to yourself.
you obviously do not understand the relationship between a of a and Cl, in fact you do not seem to understand basic aerodynamics.
i would love to know where you got that from.
perhaps you could also explain why you can buy leading edge spoilers to minimise wing drop on cessnas, using your theory.
to firefly bob
when you have a very low nose attitude the selection of full power increses height loss. not to be advised if you fall out of the bottom of a loop when close to the ground.
beware of "book" instructors who have only ever taught stall recovery!
you obviously do not understand the relationship between a of a and Cl, in fact you do not seem to understand basic aerodynamics.
i would love to know where you got that from.
perhaps you could also explain why you can buy leading edge spoilers to minimise wing drop on cessnas, using your theory.
to firefly bob
when you have a very low nose attitude the selection of full power increses height loss. not to be advised if you fall out of the bottom of a loop when close to the ground.
beware of "book" instructors who have only ever taught stall recovery!
Please explain the previously unheard of phenomenon 'falling out of the bottom of a loop'? Is it another of those fabled manouevres known only to aviation fiction writers, ranking alongside the 'tailspin' and the 'power dive'?
Too many words have fallen out of bottoms various on this thread. There is a fundamental misunderstanding by some of the difference between Cl/alpha curves with and without flap, the reasons for tip stall, the difference between design requirements for stalling behaviour and the standard stall recovery techniques for a stall with wing drop....
The reasons why power assists recovery in vertical manouvres are:
From low speed the a/c will accelerate to a safe manoeuvring speed with less height loss.
When being pitched firmly to recover, energy loss will be less if thrust is opposing drag.
Too many words have fallen out of bottoms various on this thread. There is a fundamental misunderstanding by some of the difference between Cl/alpha curves with and without flap, the reasons for tip stall, the difference between design requirements for stalling behaviour and the standard stall recovery techniques for a stall with wing drop....
The reasons why power assists recovery in vertical manouvres are:
From low speed the a/c will accelerate to a safe manoeuvring speed with less height loss.
When being pitched firmly to recover, energy loss will be less if thrust is opposing drag.
The way I taught it was:
1. Pitch to fix the stall problem. Will work with or without power although significant height loss without power.
2. Rudder applied as necessary to prevent yaw.
3. Power application to reduce height loss. If the recovery results in a significant nose low attitude eg after a spin or whatever, delay power application until at least in a S&L attitude or nose is above the horizon.
1. Pitch to fix the stall problem. Will work with or without power although significant height loss without power.
2. Rudder applied as necessary to prevent yaw.
3. Power application to reduce height loss. If the recovery results in a significant nose low attitude eg after a spin or whatever, delay power application until at least in a S&L attitude or nose is above the horizon.
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ah Tinstaafl at last someone who actually understands stall recovery.
your instructor was probably experienced in aerobatics and would have also known what falling out of the bottom of a loop meant too!
i learnt both of these lessons under the watcful eye of barry tempest, an ex member of the british aerobatic team and panel examiner
however pitch to fix is not really the way a proffesional instructor would explain the recovery, its too vague
but this is a cracker, even better
imagine trying to teach the local milkman to fly using this explanation.
the reasons for tip stall, the difference between design requirements for stalling behaviour and the standard stall recovery techniques for a stall with wing drop....
what a load of twaddle and thats even if you can understand it and i cant even after 35 yeras of profesional flying!
your instructor was probably experienced in aerobatics and would have also known what falling out of the bottom of a loop meant too!
i learnt both of these lessons under the watcful eye of barry tempest, an ex member of the british aerobatic team and panel examiner
however pitch to fix is not really the way a proffesional instructor would explain the recovery, its too vague
but this is a cracker, even better
imagine trying to teach the local milkman to fly using this explanation.
the reasons for tip stall, the difference between design requirements for stalling behaviour and the standard stall recovery techniques for a stall with wing drop....
what a load of twaddle and thats even if you can understand it and i cant even after 35 yeras of profesional flying!
whatunion, do you find English difficult....
1. The reasons for tip stall:
Cl v AoA curve and actual AoA at each part of the wing. Exacerbated by poor rigging, power effects and flap angle (eta tab)
2. The difference between design requirements for stalling behaviour and the standard stall recovery techniques for a stall with wing drop....
One is an airframe design requirement, the other is a technique.
Given your "35 yeras of profesional flying" (sic), please explain what on earth 'falling out of the bottom of a loop' means? In 35 years of professional flying I have never come across this phenomenon before. Others have also asked you to expound on this, but all we've heard so far is a deafening silence.
Earlier you stated:
".....for anybody who is not convinced can i suggest you stall and spin a cherokee with a front seat passenger and then try it with 4 heavy male passengers on board (but dont do it until i give you the recovery technique in my next post)"
You do know what the spinning limits on the PA28 are, I suppose?
1. The reasons for tip stall:
Cl v AoA curve and actual AoA at each part of the wing. Exacerbated by poor rigging, power effects and flap angle (eta tab)
2. The difference between design requirements for stalling behaviour and the standard stall recovery techniques for a stall with wing drop....
One is an airframe design requirement, the other is a technique.
Given your "35 yeras of profesional flying" (sic), please explain what on earth 'falling out of the bottom of a loop' means? In 35 years of professional flying I have never come across this phenomenon before. Others have also asked you to expound on this, but all we've heard so far is a deafening silence.
Earlier you stated:
".....for anybody who is not convinced can i suggest you stall and spin a cherokee with a front seat passenger and then try it with 4 heavy male passengers on board (but dont do it until i give you the recovery technique in my next post)"
You do know what the spinning limits on the PA28 are, I suppose?
Last edited by BEagle; 22nd May 2004 at 14:07.
erm, minor point but...
...that *is* how a professional would explain it to the local milkman, the local car mechanic, truck drivers, farmers, labourers, chinese & vietnamese cadets with minimal english language skills, doctors, lawyers etc. Namely me!
I spent 10 years instructing at all levels from aeroclub to airline cadets. I also used to teach basic aerobatics & do licence tests.
My students didn't get to a stalling lesson without comprehending that exceeding the Crit AoA is the primary problem. Ergo, pitch to correct the problem. One goal (as an instructor) is to minimise the verbiage the poor bloody student has to attend while at, near or over their capacity. Hence 'Pitch to fix' as a short-hand (er...-speak).
cheers
T.
...that *is* how a professional would explain it to the local milkman, the local car mechanic, truck drivers, farmers, labourers, chinese & vietnamese cadets with minimal english language skills, doctors, lawyers etc. Namely me!
I spent 10 years instructing at all levels from aeroclub to airline cadets. I also used to teach basic aerobatics & do licence tests.My students didn't get to a stalling lesson without comprehending that exceeding the Crit AoA is the primary problem. Ergo, pitch to correct the problem. One goal (as an instructor) is to minimise the verbiage the poor bloody student has to attend while at, near or over their capacity. Hence 'Pitch to fix' as a short-hand (er...-speak).
cheers
T.
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dropping out of the bottom of a loop, isnt that self explanatory!
"dishing out of a roll",
sorry when i did aerobatics all this was common language. also seems common sense
mind u these days it seems everyone is frightened to even spin a/c!
i have just taken this off my previous post
"when you have a very low nose attitude the selection of full power increses height loss. not to be advised if you fall out of the bottom of a loop when close to the ground."
perhaps instead of trying to make snide remarks (another hallmark of a poor instructor)you should just read the posts
"pitch to fix" explanation to chinese and vietenese
no sorry i would prefer my explanation. "move the cc forward until flying control is fully regained" (that works for stalling or spinning)
heres another cracker for an explanation for wing tip stall
Cl v AoA curve and actual AoA at each part of the wing. Exacerbated by poor rigging, power effects and flap angle (eta tab)
what is the arrival time for the tab and if it be real where do it come from and where do it go!
"a of a curve" thats a new one. that was called camber when i was an instructor. again the local milkman will know camber but, a of a curve, i dont think so!!!!! perhaps i just taught more local milkmen!
oh yes good try but you missed out another major consideration wing area
try defing Cl - 1/2r - V2 - S that may help u understand what you are trying to say (s = area)
you only gave 3 reasons for wing drop , again, wrong.
others you can add are surface irregularities on leading edge or upper surface, yaw, wing area inc due to flap selection (with flaps that increase wing area.) mis handling of ailerons
spanwise movement of centre of pressure etc
wing tip stalling isnt rocket science instead of trying to impress with complication try impressing with simplicity.
tips stall before roots because of a difference in lift between tip and root, end of story
if you can get the root to stall before the tip you can greatly minimise wing drop at the stall, putting flap down does the OPPOSITE, thats why tip stalling can be more pronounced with flaps down on certain a/c.
also said was
".....for anybody who is not convinced can i suggest you stall and spin a cherokee with a front seat passenger and then try it with 4 heavy male passengers on board (but dont do it until i give you the recovery technique in my next post)"
You do know what the spinning limits on the PA28 are, I suppose?
yes i do know and so does the caa who prosecuted the handling pilot at the local magistrates courts after both wings had to be replaced on G-AWXS due to the excessive G on recovery.
my point which you failed to replicate is that c of g is the most important factor on handling characteristics on stall/spin recovery as this pilot found out ( he is currently a captain with a major airline, Hi Nick!)
as a matter of interest they only recovered within feet of the ground because the instructor in the rear(hi graham!) leant forward to try and jockey the throttle backward and forward. the shift in c of g allowed the handling pilot to recover.
its events like this that teach us all more than is written in any book.
remeber mike lythgo, selecting full thrust for stall recovery didnt help him, in fact it just made it worse, so much for STANDARD RECOVERY.
now u have been in flying 35 years tell me who he was and how selecting full thrust didnt help him in one the steepest learning curves of stall recovery of all time.
"dishing out of a roll",
sorry when i did aerobatics all this was common language. also seems common sense
mind u these days it seems everyone is frightened to even spin a/c!
i have just taken this off my previous post
"when you have a very low nose attitude the selection of full power increses height loss. not to be advised if you fall out of the bottom of a loop when close to the ground."
perhaps instead of trying to make snide remarks (another hallmark of a poor instructor)you should just read the posts
"pitch to fix" explanation to chinese and vietenese
no sorry i would prefer my explanation. "move the cc forward until flying control is fully regained" (that works for stalling or spinning)
heres another cracker for an explanation for wing tip stall
Cl v AoA curve and actual AoA at each part of the wing. Exacerbated by poor rigging, power effects and flap angle (eta tab)
what is the arrival time for the tab and if it be real where do it come from and where do it go!
"a of a curve" thats a new one. that was called camber when i was an instructor. again the local milkman will know camber but, a of a curve, i dont think so!!!!! perhaps i just taught more local milkmen!
oh yes good try but you missed out another major consideration wing area
try defing Cl - 1/2r - V2 - S that may help u understand what you are trying to say (s = area)
you only gave 3 reasons for wing drop , again, wrong.
others you can add are surface irregularities on leading edge or upper surface, yaw, wing area inc due to flap selection (with flaps that increase wing area.) mis handling of ailerons
spanwise movement of centre of pressure etc
wing tip stalling isnt rocket science instead of trying to impress with complication try impressing with simplicity.
tips stall before roots because of a difference in lift between tip and root, end of story
if you can get the root to stall before the tip you can greatly minimise wing drop at the stall, putting flap down does the OPPOSITE, thats why tip stalling can be more pronounced with flaps down on certain a/c.
also said was
".....for anybody who is not convinced can i suggest you stall and spin a cherokee with a front seat passenger and then try it with 4 heavy male passengers on board (but dont do it until i give you the recovery technique in my next post)"
You do know what the spinning limits on the PA28 are, I suppose?
yes i do know and so does the caa who prosecuted the handling pilot at the local magistrates courts after both wings had to be replaced on G-AWXS due to the excessive G on recovery.
my point which you failed to replicate is that c of g is the most important factor on handling characteristics on stall/spin recovery as this pilot found out ( he is currently a captain with a major airline, Hi Nick!)
as a matter of interest they only recovered within feet of the ground because the instructor in the rear(hi graham!) leant forward to try and jockey the throttle backward and forward. the shift in c of g allowed the handling pilot to recover.
its events like this that teach us all more than is written in any book.
remeber mike lythgo, selecting full thrust for stall recovery didnt help him, in fact it just made it worse, so much for STANDARD RECOVERY.
now u have been in flying 35 years tell me who he was and how selecting full thrust didnt help him in one the steepest learning curves of stall recovery of all time.
Mike Lithgow was a famous test pilot.
If you don't know the difference between camber and the lift curve slope (that's the Cl vs AoA curve with Cl on the y-axis and AoA on the x-axis), don't bother to comment further.
I certainly agree that CG position has an effect on stalling behaviour - the T67A demonstrates that very well.
But what in earth is 'falling out of the bottom of a loop'?
eta tab is the deflexion angle of a control surface - sorry, no Greek on this PC!
If you don't know the difference between camber and the lift curve slope (that's the Cl vs AoA curve with Cl on the y-axis and AoA on the x-axis), don't bother to comment further.
I certainly agree that CG position has an effect on stalling behaviour - the T67A demonstrates that very well.
But what in earth is 'falling out of the bottom of a loop'?
eta tab is the deflexion angle of a control surface - sorry, no Greek on this PC!
If he really means an accelerated stall at the bottom of a loop, then not using full power in the recovery will certainly make things worse.
Full power on the buffet nibble will always maximise performance.
'...the phantom had such a violent wing drop at the stall which you wouldnt belive so much so that all students were told never to make any rearward pressure after going over the threshold merely to let it hit the deck with power on'. Well, that's not the way I was taught to fly the F4. It was flown at constant AoA on the approach at the correct datum speed; it wasn't 'merely allowed to hit the deck', the descent rate was very easily reduced immediately prior to touchdown - although throttling back excessively in 12th stage air would certainly cause a high RoD to develop as the flap blow reduced. The a/c certainly had some vices at high AoA; roll reversal being one and wing rock another. However, unloading for control was quite straightforward.
whatunion, your rudeness and level of knowledge are all too obvious for all to read. I don't think that I've ever come across such postings as yours on PPRuNe before.
(Edited because I was rather harsh yesterday!)
Full power on the buffet nibble will always maximise performance.
'...the phantom had such a violent wing drop at the stall which you wouldnt belive so much so that all students were told never to make any rearward pressure after going over the threshold merely to let it hit the deck with power on'. Well, that's not the way I was taught to fly the F4. It was flown at constant AoA on the approach at the correct datum speed; it wasn't 'merely allowed to hit the deck', the descent rate was very easily reduced immediately prior to touchdown - although throttling back excessively in 12th stage air would certainly cause a high RoD to develop as the flap blow reduced. The a/c certainly had some vices at high AoA; roll reversal being one and wing rock another. However, unloading for control was quite straightforward.
whatunion, your rudeness and level of knowledge are all too obvious for all to read. I don't think that I've ever come across such postings as yours on PPRuNe before.
(Edited because I was rather harsh yesterday!)
Last edited by BEagle; 24th May 2004 at 20:29.
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"whatunion, your rudeness and level of knowledge are all too obvious for all to read. I don't think that I've ever come across such postings as yours on PPRuNe before."
perhaps you should read some of your own postings then.
heres another cracker
"If you don't know the difference between camber and the lift curve slope (that's the Cl vs AoA curve with Cl on the y-axis and AoA on the x-axis), don't bother to comment further."
i know how to simply explain why a wing drops at the stall.
yet another comprehensive explanation
"Full power on the buffet nibble will always maximise performance."
i like this one best
"Mike Lithgow was a famous test pilot."
you imply you have flown jets, is that all you can say. with your vast unchallengable knowledge surely you can come up with more than that, or wasnt a suitable book to hand to quote from this time.
perhaps you should read some of your own postings then.
heres another cracker
"If you don't know the difference between camber and the lift curve slope (that's the Cl vs AoA curve with Cl on the y-axis and AoA on the x-axis), don't bother to comment further."
i know how to simply explain why a wing drops at the stall.
yet another comprehensive explanation
"Full power on the buffet nibble will always maximise performance."
i like this one best
"Mike Lithgow was a famous test pilot."
you imply you have flown jets, is that all you can say. with your vast unchallengable knowledge surely you can come up with more than that, or wasnt a suitable book to hand to quote from this time.
OK then, Mike was Mr Swift at Vickers Supermarine... And I don't 'imply' that I have flown 'jets', I have indeed flown several types of jet aeroplane and was taught all about full power and buffet nibble on the JP, Gnat, Hunter, Hawk, Phantom (opt AoA rather than buffet) , Buccaneer (steady tone ADD, not buffet)...
Have you ever taught Max Rate Turns? That's when the student learns the max rho, max thrust, Cl max and max AoB relationship - manoeuvring for best turn performance at full power, buffet nibble and the AoA which gives level flight under these circumstances at the lowest possible altitude to maximise rho.
You appear to be heading for the JCB trophy...
Have you ever taught Max Rate Turns? That's when the student learns the max rho, max thrust, Cl max and max AoB relationship - manoeuvring for best turn performance at full power, buffet nibble and the AoA which gives level flight under these circumstances at the lowest possible altitude to maximise rho.
You appear to be heading for the JCB trophy...
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Must admit from my - much more limited - aeros experience, adding power 'tightens' things up.
The steep turns example is a perfect one. I know I can pull harder, turn tighter, with more power. The same dynamics are surely going on regardless of bank?
I can't see how you can pull out from the bottom of a loop quicker, and with less altitude loss, by using same or less power.
(If you like, I\'ll post a link to a video which shows what you can do with power to transition a downline into the opposite. The particular example - lots of BHP - shows an almost dead stop on pulling up from the descent)
The steep turns example is a perfect one. I know I can pull harder, turn tighter, with more power. The same dynamics are surely going on regardless of bank?
I can't see how you can pull out from the bottom of a loop quicker, and with less altitude loss, by using same or less power.
(If you like, I\'ll post a link to a video which shows what you can do with power to transition a downline into the opposite. The particular example - lots of BHP - shows an almost dead stop on pulling up from the descent)
Last edited by paulo; 25th May 2004 at 20:51.
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As you didnt say you had actually flown jets I used the word, imply.
One thing is not in question here is that you, Mr Beagle have a wealth of experience and knowledge. In fact as you have implied(nice word isnt it) i have a very poor level of knowledge. I remember trying, yes trying, to study. advanced aerodynamics. So i am aware of my own limitations.
yes i have taught max rate turns but we were talking about the use of power in other situations.
You still havnt drawn the connection i was hoping you would with Mike Lythgo and stalling, with respect have another go
This thread appears to be going nowhere at the moment so pardon me if i take the liberty of starting a new thread under stalling and spinning which i hope mr beagle and friends will join me on.
One thing is not in question here is that you, Mr Beagle have a wealth of experience and knowledge. In fact as you have implied(nice word isnt it) i have a very poor level of knowledge. I remember trying, yes trying, to study. advanced aerodynamics. So i am aware of my own limitations.
yes i have taught max rate turns but we were talking about the use of power in other situations.
You still havnt drawn the connection i was hoping you would with Mike Lythgo and stalling, with respect have another go
This thread appears to be going nowhere at the moment so pardon me if i take the liberty of starting a new thread under stalling and spinning which i hope mr beagle and friends will join me on.
