High speed stall
Not so N, but still FG
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stillin 1, it is true that our rubbishy elastic powered amateur death machines don't have alpha-ometers or whatever they are properly called, but surely it's still relevant for instructors to tell PPL studes about AofA. I recall that my instructors went on about AofA a great deal and told me not to get fixated with the idea that the aircraft will always stall at speed x or sometimes at speed y, or only when going slowly, or only when the nose is pointing up. I read "Stick and Rudder" and "See How it Flies" at the time, which further shoved the "angle of attack is, er, quite important, really" point home.
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Sorry to butt in chaps, I'm only a PPL but..
I learned to fly on gliders, and one of my instructors once said the wing will always stall when the stick is at the same place - this is something that has always stuck with me.
If you are flying slowly at 1G this position will give you 'the' stall speed. If however, you are pulling hard in a tight turn the wing will also stall when the stick is at that point.
I have to say, the same instructor never explained how on a k7, we could go up the wire with the stick on the back stop without stalling though!
Forget about the ASI - it's the biggest lier in the cockpit and the information it does give is always out of date.
Kingy
I learned to fly on gliders, and one of my instructors once said the wing will always stall when the stick is at the same place - this is something that has always stuck with me.
If you are flying slowly at 1G this position will give you 'the' stall speed. If however, you are pulling hard in a tight turn the wing will also stall when the stick is at that point.
I have to say, the same instructor never explained how on a k7, we could go up the wire with the stick on the back stop without stalling though!
Forget about the ASI - it's the biggest lier in the cockpit and the information it does give is always out of date.
Kingy
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DFC, it never fails to amaze me that angle of attack appears to be so little understood in light aviation. Flying is all about agle of attack, and Kingy has got it right when he says that broadly a wing will stall when the stick is in a certain position, and when the chips are down and you are screwing around low level in bad weather it is much easier to recognise that the stick is getting close to this critical position than to monitor speed. The stick is your angle of attack indicator! Read this again and go and fly it!
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Just to stick my oar in.
Broadly true, when doing 1G as Dan has already explained. I haven't done aeros for a while, but I clearly remember that in doing a loop, during the slow speed inverted (nearly zero g) section of a loop it goes so mushy that you pull to the stops without stalling. On the other hand, at the base of the loop when pulling, say 4G, you can only pull the stick back a little way before the buffet.
Seriously, I don't concentrate on the stick position when thinking about stalling, and in a spam can sensing a relative position of the yoke seems very difficult. Its much better to feel what’s happening.
I have to agree with those that say the best thing to do is to go up with an aeros instructor to learn to nibble the buffet round a max rate turn and (if you want) pull a bit beyond to an incipient spin. Once you've done it you'll realise its
a - not difficult to get the hang of
b- not scary, but in fact, fun and rewarding!
Then you can go onto full spins and aeros and have lots of fun.
Kingy has got it right when he says that broadly a wing will stall when the stick is in a certain position,
Seriously, I don't concentrate on the stick position when thinking about stalling, and in a spam can sensing a relative position of the yoke seems very difficult. Its much better to feel what’s happening.
I have to agree with those that say the best thing to do is to go up with an aeros instructor to learn to nibble the buffet round a max rate turn and (if you want) pull a bit beyond to an incipient spin. Once you've done it you'll realise its
a - not difficult to get the hang of
b- not scary, but in fact, fun and rewarding!
Then you can go onto full spins and aeros and have lots of fun.
quote:
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Kingy has got it right when he says that broadly a wing will stall when the stick is in a certain position,
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There are a few if and buts associated with that statement - one is "for the same cg position"
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Kingy has got it right when he says that broadly a wing will stall when the stick is in a certain position,
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There are a few if and buts associated with that statement - one is "for the same cg position"
Yes indeed BEagle, and I remember that diagram well from the CFS bumper book of being an instructor. I am quite happy to accept that the stalling speed varies with the square root of N. The L component is increased to provide the turning force and maintain the aircraft in level flight. However, to acheive the extra L, the angle of attack has to be increased thus increasing the load factor.
It's just easier to explain to a student that the load factor increases with manouevre, or g, and that the stalling speed increases as well. Draw that diagram on the board and you will lose him very rapidly.
But the point of the exercise I mentioned is to show that a stall can occur at a speed and or attitude other than the one the student has been used to from the precceding practice. It was part of the CFS syllabus in 1993 when I went through.
And I can't agree that angle of attack is always dependant on stick position. It's a clue, but there are lenty of circumstances when this won't be true.
It's just easier to explain to a student that the load factor increases with manouevre, or g, and that the stalling speed increases as well. Draw that diagram on the board and you will lose him very rapidly.
But the point of the exercise I mentioned is to show that a stall can occur at a speed and or attitude other than the one the student has been used to from the precceding practice. It was part of the CFS syllabus in 1993 when I went through.
And I can't agree that angle of attack is always dependant on stick position. It's a clue, but there are lenty of circumstances when this won't be true.
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Dan
I'd be intrigued to hear how much aerodynamic warning you find on a late model PA28 and how you define that.
They always seem to stall without buffet s&l (althought the subsequent mush down is a non event), unlike the PA32, where the buffet shook the fillings out of one's teeth about 4-5 kts before the breaK.
Would be genuinely interested in your 'pilots notes' for my continuing education - maybe I am missing the symptoms.
I know of no GA aircraft that have such poor stall characteristics that they do not give adequate aerodynamic wa
They always seem to stall without buffet s&l (althought the subsequent mush down is a non event), unlike the PA32, where the buffet shook the fillings out of one's teeth about 4-5 kts before the breaK.
Would be genuinely interested in your 'pilots notes' for my continuing education - maybe I am missing the symptoms.
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FNG
Any instructor who is not proficient and confident in spin recovery should not be allowed to fly as P1 with (a) any pre-licence student or (b) any student at all.
You may be right, I don't know. The counter argument is that the only time a GA non-aerobatic pilot is going to get near to stall/spin is when turning base-final and overcooking it, and then he may well be too low to recover from a spin. Therefore, spending time to teach IAS maintenance/control as an essential safety procedure may be more important overall. Let's face it, the time is limited. Very few people do it in 45hrs (those that do usually got very lucky with the weather) and most people that do a PPL don't really want to spend any more money than they see as necessary...
Any instructor who is not proficient and confident in spin recovery should not be allowed to fly as P1 with (a) any pre-licence student or (b) any student at all.
You may be right, I don't know. The counter argument is that the only time a GA non-aerobatic pilot is going to get near to stall/spin is when turning base-final and overcooking it, and then he may well be too low to recover from a spin. Therefore, spending time to teach IAS maintenance/control as an essential safety procedure may be more important overall. Let's face it, the time is limited. Very few people do it in 45hrs (those that do usually got very lucky with the weather) and most people that do a PPL don't really want to spend any more money than they see as necessary...
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djpil, you're right - the cg makes the biggest difference to stick posn at the stall, but for most side by side two seat
light singles, the c of g does not vary that much day to day.
Also if you have any significant "back elevator" at the top of a loop, you are flying an egg shaped figure. You will stall the wing at the top if you pull back to the "stall" position, and on the way down, if you pull to the same posn the wing will also stall, assuming you stay within the design envelope. One other point, the stall warner is not a speed dependant device, it is an angle of attack indicator.
light singles, the c of g does not vary that much day to day.
Also if you have any significant "back elevator" at the top of a loop, you are flying an egg shaped figure. You will stall the wing at the top if you pull back to the "stall" position, and on the way down, if you pull to the same posn the wing will also stall, assuming you stay within the design envelope. One other point, the stall warner is not a speed dependant device, it is an angle of attack indicator.
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I am instructor following the JAR/AOPA syllabus.
Point 1: Exercise 10 is slow flight and stalling, and 11 is incipient spins and a demonstartion of spinning (if the aircraft is cleared for it). The actual GFT only contains one stall (power off, clean...in a straight line) and two incipient stalls in base and fnal configuration. However to complete a PPL the student needs to have done 2 hours of stall and spin awareness training (usually signed off in training record). So all new students over last 4 years should have done a reasonable amount of stalling and slow flight
Point2: All intructors have to do spinning as part of their FI training and they are tested on it in their initial Instructors Test. If the aircraft airworthiness permits, I demonstrate it to all students...to discourage them from mishandling the controls at low airspeed.
Point3: A steep turn to the left in most current training aircraft, when taken to the stall will result in 'departure' (i.e. roll) to the right. This can often be quite slow and only requires the angle of attack to be reduced by moving the stick forward a little . If done to the right the a/c may roll inverted into an incipient spin... sometimes. Taking the power off and releasing the back pressure should get things back to normal fairly quickly before a true spin develops in a C152 or C172. The spin recovery for your aircarft will be detailed in the POH. How many pilots actually have read their POH?
Point 1: Exercise 10 is slow flight and stalling, and 11 is incipient spins and a demonstartion of spinning (if the aircraft is cleared for it). The actual GFT only contains one stall (power off, clean...in a straight line) and two incipient stalls in base and fnal configuration. However to complete a PPL the student needs to have done 2 hours of stall and spin awareness training (usually signed off in training record). So all new students over last 4 years should have done a reasonable amount of stalling and slow flight
Point2: All intructors have to do spinning as part of their FI training and they are tested on it in their initial Instructors Test. If the aircraft airworthiness permits, I demonstrate it to all students...to discourage them from mishandling the controls at low airspeed.
Point3: A steep turn to the left in most current training aircraft, when taken to the stall will result in 'departure' (i.e. roll) to the right. This can often be quite slow and only requires the angle of attack to be reduced by moving the stick forward a little . If done to the right the a/c may roll inverted into an incipient spin... sometimes. Taking the power off and releasing the back pressure should get things back to normal fairly quickly before a true spin develops in a C152 or C172. The spin recovery for your aircarft will be detailed in the POH. How many pilots actually have read their POH?
How many pilots actually have read their POH?
G
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Proposition 1: Any instructor who is not proficient and confident in spin recovery should not be allowed to fly as P1 with (a) any pre-licence student or (b) any student at all.
Since the the requirement to teach fully developed spins was taken out of the syllabus, apart from teaching the incipient spin, not many FI's or students feel willing to go into it fully.
The reason that it was taken out was that far more people were being killed in spin training than in stall/spin accidents. The fact remains that with the vast majority of GA types you have to be either unlucky or incredibly ham fisted to end up spinning inadvertantly unless you are doing aeros.
How many accidents have been attributed to spinning in recent years? I cant think of any, but I certainly can remember of couple of horrible accidents due to spin training.
Any FI should of course be proficient in stall and spin avoidance, since that is what we want students and PPL do. If you teach someone to recognise the symptoms of a stall etc, then hopefully they'll never need the ability to recover from a 'real' event.
Another way of looking at is if someone is daft enough to to get into a spin turning onto final, then what is the likelyhood of them having the skill to recover sucessfully?
Not so N, but still FG
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IO540, that may true enough, in relation to the students, and I didn't mean to re-open here the perennial debate as to how much, if any, spin recovery should be demonstrated or taught to student pilots. I was addressing the skills-set which the instructor should possess. I know of course that instructors do spinning during their FI training, but was struck by the reference above to an instructor who felt uncomfortable about demonstrating spins to a student.
During any flying training, the student may put the aircraft into a situation of potential danger. Indeed, doing so may be part of the learning proceess. One of the difficult judgments for an instructor must be when to let things carry on going wrong in order to demonstrate a point, and when to intervene*. Suppose the student really stuffs it up before the instructor has a chance to take over? For example, during the steep turning exercise, the student pulls like mad, and the aircraft spins out of the turn. This could happen with a very new student, or maybe with an advanced student in whose abilities the instructor has some confidence, doing some pre-test revision. In that situation, if the instructor himself has hardly ever spun since hois course, and isn't confident in his spin recovery skills, a bad situation could get much worse.
*I was recently speaking to a friend who instructs at CFS about this, and he told me that the flying he is now doing ranks as amongst the most dangerous flying he's ever done because he is teaching other highly skilled instructors how to deal with dangerous mistakes made by advanced students, and this involves deliberately putting the aircraft in big trouble (and this is a guy who has flown in some very hairy, sandy places and been very severely shot at).
During any flying training, the student may put the aircraft into a situation of potential danger. Indeed, doing so may be part of the learning proceess. One of the difficult judgments for an instructor must be when to let things carry on going wrong in order to demonstrate a point, and when to intervene*. Suppose the student really stuffs it up before the instructor has a chance to take over? For example, during the steep turning exercise, the student pulls like mad, and the aircraft spins out of the turn. This could happen with a very new student, or maybe with an advanced student in whose abilities the instructor has some confidence, doing some pre-test revision. In that situation, if the instructor himself has hardly ever spun since hois course, and isn't confident in his spin recovery skills, a bad situation could get much worse.
*I was recently speaking to a friend who instructs at CFS about this, and he told me that the flying he is now doing ranks as amongst the most dangerous flying he's ever done because he is teaching other highly skilled instructors how to deal with dangerous mistakes made by advanced students, and this involves deliberately putting the aircraft in big trouble (and this is a guy who has flown in some very hairy, sandy places and been very severely shot at).
Last edited by FNG; 11th Dec 2003 at 17:05.
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Genghis the Engineer
I don't think reading the POH is very common among PPL students. It was never even mentioned to me, nor to anyone else I know.
I have a few pilots names on my plane; I photocopied the POH and ensured all of them bought a copy. But I know this is pretty rare.
Possibly a factor in why the POH is not often referenced is that it tends to be very generic and bear little relation to what is actually fitted to the aircraft.
I don't think reading the POH is very common among PPL students. It was never even mentioned to me, nor to anyone else I know.
I have a few pilots names on my plane; I photocopied the POH and ensured all of them bought a copy. But I know this is pretty rare.
Possibly a factor in why the POH is not often referenced is that it tends to be very generic and bear little relation to what is actually fitted to the aircraft.
Finals 3 greens.
I teach on both slab wing PA28s and the newer wing design and I find the aerodynamic warning on a new wing PA28 quite adequate. In fact, it displays all the classic characteristics of a stall, is quite well behaved and is very docile. I recently renewed my instructor rating on a PA28-161 - the exercise I demonstrated for the test was stalling.
You may be confused about the origins of the buffet and where to notice them. You mention the PA38 which I remeber does shake at the stall. But it was designed as a trainer and this may be a deliberate design feature. The PA28 was designed as a tourer with comfort in mind. However, the buffet is there and like a lot of low wing aircraft it is first noticed through the control column as the turbulent airflow breaks off the wing and is felt through the stabilator.
When you train someone, you are not just training him/her for that one type. They will go and fly something different at some stage and need a thorough grounding in all the aspects of an exercise. It the emphasis on buffet recognition in the stalling exercise is not made because the buffet is so obvious, there is a danger it may be missed when that student flys another aircraft.
I teach on both slab wing PA28s and the newer wing design and I find the aerodynamic warning on a new wing PA28 quite adequate. In fact, it displays all the classic characteristics of a stall, is quite well behaved and is very docile. I recently renewed my instructor rating on a PA28-161 - the exercise I demonstrated for the test was stalling.
You may be confused about the origins of the buffet and where to notice them. You mention the PA38 which I remeber does shake at the stall. But it was designed as a trainer and this may be a deliberate design feature. The PA28 was designed as a tourer with comfort in mind. However, the buffet is there and like a lot of low wing aircraft it is first noticed through the control column as the turbulent airflow breaks off the wing and is felt through the stabilator.
When you train someone, you are not just training him/her for that one type. They will go and fly something different at some stage and need a thorough grounding in all the aspects of an exercise. It the emphasis on buffet recognition in the stalling exercise is not made because the buffet is so obvious, there is a danger it may be missed when that student flys another aircraft.
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Croqueteer,
If you are at the top of an inside loop, you are inverted.
Take the position described where you are holding the stick back against or close to the rear stop. Now keeping the aircraft still, extend the stick through the floor and imagine yourself sitting on top of the inverted aircraft. You will se that from this perspective, the stick is at or close to the imaginary forward stop......i.e. similar to being upright and pushing over the top.
True, there is no angle of attack indicator in many light aircraft. However, teaching that the stall always ocurs at the same angle of attack is true and also is easy to relate to the required movement of the stick to prevent or recover from the stall. It is also easy to relate to the fact that as angle of attack is increased, drag is increased which explains the closing in of the margins in a high G situation and also for budding aero's pilots, explains one useful way of recucing the acceleration when pointing towards the ground.....pull to the bufett (G limits permitting).
G loading at a particular speed is a function of angle of attack.
It is possible to complete a 60deg bank turn at 1.01 G.......it will have a very big radius though.
IMHO, to put into a student's mind that proximity to the stall is in some way related to G loading could lead them think that they have a margin above the stall....when they don't simply because they are about to stall at 1G.
Try an outside 60deg turn....and stall it by PUSHING too hard......much easier to explain using angle of attack!!!
At the end of the day, for most students, the high speed stall is of theoretical value only because in many aircraft that they fly, something will break before they stall at anything above Va........which is why I relate the G loading to steep turns and other cases of loading both positive and negative.
Regards,
DFC
If you are at the top of an inside loop, you are inverted.
Take the position described where you are holding the stick back against or close to the rear stop. Now keeping the aircraft still, extend the stick through the floor and imagine yourself sitting on top of the inverted aircraft. You will se that from this perspective, the stick is at or close to the imaginary forward stop......i.e. similar to being upright and pushing over the top.
True, there is no angle of attack indicator in many light aircraft. However, teaching that the stall always ocurs at the same angle of attack is true and also is easy to relate to the required movement of the stick to prevent or recover from the stall. It is also easy to relate to the fact that as angle of attack is increased, drag is increased which explains the closing in of the margins in a high G situation and also for budding aero's pilots, explains one useful way of recucing the acceleration when pointing towards the ground.....pull to the bufett (G limits permitting).
G loading at a particular speed is a function of angle of attack.
It is possible to complete a 60deg bank turn at 1.01 G.......it will have a very big radius though.
IMHO, to put into a student's mind that proximity to the stall is in some way related to G loading could lead them think that they have a margin above the stall....when they don't simply because they are about to stall at 1G.
Try an outside 60deg turn....and stall it by PUSHING too hard......much easier to explain using angle of attack!!!
At the end of the day, for most students, the high speed stall is of theoretical value only because in many aircraft that they fly, something will break before they stall at anything above Va........which is why I relate the G loading to steep turns and other cases of loading both positive and negative.
Regards,
DFC
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DFC, I don't what being inverted has to do with it - if you pull too hard at the wrong speed YOU WILL STILL STALL and it will still be a POSITIVE stall.
I also do not see how you are going to do a 60degree bank turn at 1.01g, certainly not if it is level and in balance, and I believe this is what is being refered to here.
I also do not see how you are going to do a 60degree bank turn at 1.01g, certainly not if it is level and in balance, and I believe this is what is being refered to here.
Quite right! It wouldn't be a level, balanced 60 deg AoB turn at 1.01G!
The "It'll stall at any speed" demo (as Dan says) which we used to do on the Bulldog was very useful in pointing out that AoA, not speed, causes the stall. Dive to about 110 KIAS, pull up on the pre-stall buffet to about 60 deg nose up, then push over the top at zero G and the IAS off the bottom of the ASI, show that it was still flying unstalled. But it could be a bit of a honk-making demo!
The "It'll stall at any speed" demo (as Dan says) which we used to do on the Bulldog was very useful in pointing out that AoA, not speed, causes the stall. Dive to about 110 KIAS, pull up on the pre-stall buffet to about 60 deg nose up, then push over the top at zero G and the IAS off the bottom of the ASI, show that it was still flying unstalled. But it could be a bit of a honk-making demo!
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It is easy when flying into an unfamiliar strip with a tailwind on base leg to fly through the centre line and if all your attention is outside, you can still feel if the stick or column is a bit far back and warning bells will ring if you've thought about what I've said. DFC, I don't know what you're blethering about, unless you're thinking of Neil William's Stampe pictures!
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DFC, not quite sure what you mean by being inverted at the top of a loop. You are upside down, but if the manoeuvre is done correctly then you are still at positive 'g' and the a/c thinks it is still the right way up. It has no idea where it is in relation to the ground unlike the pilot, who's senses tell them all sorts of nonsense.
I have had the pleasure of being stalled at a relatively high speeds and not had anything fall off the machine. Ahh, I love teaching aero's.....
I'm never quesy no matter how bad I stuff up, but with a ham phisted student.........
Can't see how a 1.01g turn at 60 deg AoB would be level? Am I missing something?
I have had the pleasure of being stalled at a relatively high speeds and not had anything fall off the machine. Ahh, I love teaching aero's.....
I'm never quesy no matter how bad I stuff up, but with a ham phisted student.........Can't see how a 1.01g turn at 60 deg AoB would be level? Am I missing something?