High speed stall
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High speed stall
Hi all
Im doing my PPL at the moment (20 hrs) and today we were doing steep angle turns.
We climbed up to 4500ft and began the exercise however when i was doing the steep level turn the stall warner was constantly sounding, it seemed to happen more in the left bank.
My instructor told me that was the high speed stall warner. I was wondering if there is any danger or need for caution when the stall warner sounds during a steep level turn?
The aircraft is a PA38 Thomahawk by the way.
I should really have asked my instructor at the time but did not think to do so.
Thanks in advance
Dave
Im doing my PPL at the moment (20 hrs) and today we were doing steep angle turns.
We climbed up to 4500ft and began the exercise however when i was doing the steep level turn the stall warner was constantly sounding, it seemed to happen more in the left bank.
My instructor told me that was the high speed stall warner. I was wondering if there is any danger or need for caution when the stall warner sounds during a steep level turn?
The aircraft is a PA38 Thomahawk by the way.
I should really have asked my instructor at the time but did not think to do so.
Thanks in advance
Dave
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Hi,
Your stall warner will sound before a full stall develops.(otherwise it would be a stall announcer rather than warner!)
As they would probably have told you you need increased back pressure in the turn to keep the aircraft level, this in turn increases the wing loading and this increases your stall speed.
So basically you will stall at a higher speed when you are in a turn. A good rule of thumb is you need 1 knot more airspeed for every 2 degrees of extra bank.
The Tomahawk may fly very close to the stall in steep turns, too long ago for me to remember but ask your instructor for a thorough de brief on what happened and make sure they brief you thoroughly before you fly so you know exactly what you will be doing and what to expect. You'll learn much more and much quicker!
Enjoy the rest of the PPL.
PS Unless its specific to the Tomahawk it shouldn't make any difference whether you are turning left or right.
Your stall warner will sound before a full stall develops.(otherwise it would be a stall announcer rather than warner!)
As they would probably have told you you need increased back pressure in the turn to keep the aircraft level, this in turn increases the wing loading and this increases your stall speed.
So basically you will stall at a higher speed when you are in a turn. A good rule of thumb is you need 1 knot more airspeed for every 2 degrees of extra bank.
The Tomahawk may fly very close to the stall in steep turns, too long ago for me to remember but ask your instructor for a thorough de brief on what happened and make sure they brief you thoroughly before you fly so you know exactly what you will be doing and what to expect. You'll learn much more and much quicker!
Enjoy the rest of the PPL.
PS Unless its specific to the Tomahawk it shouldn't make any difference whether you are turning left or right.
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MVE,anymore posts like that and we will have to swaps seats...
Aerofoil, the stall speed of an aircraft will increse by 19% in a 45 degree bank i.e. a stall speed of 50kts would become 60kts (59.5) and the stall warner therefore coming on at 65kts. Check the aircrafts Pilot Operating Handbook for recommended speeds.
On a personal note I would not like to fully stall the aircraft whilst in a 45 degree bank.
Most importantly, sit and discuss it with your instructor....its what you pay him/her for.
Aerofoil, the stall speed of an aircraft will increse by 19% in a 45 degree bank i.e. a stall speed of 50kts would become 60kts (59.5) and the stall warner therefore coming on at 65kts. Check the aircrafts Pilot Operating Handbook for recommended speeds.
On a personal note I would not like to fully stall the aircraft whilst in a 45 degree bank.
Most importantly, sit and discuss it with your instructor....its what you pay him/her for.
I can't believe that any FI actually thinks that there's such a thing as a 'high speed' stall warner....
Were you given a ground brief? That should have covered the reason for the relation between 'g' loading, angle of bank and the relationship between indicated stalling speed and 'g' loading in a steep turn.
Were you given a ground brief? That should have covered the reason for the relation between 'g' loading, angle of bank and the relationship between indicated stalling speed and 'g' loading in a steep turn.
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Wouldn't worry too much about a stall in a steep turn. One of the more satisfying manoeuvers to practice (in a suitable aeroplane of course) is the "max rate" turn - a steeper "steep turn" where you are in a level turn with full power, turning at a rate where the 'g' loading puts you on the edge of the accelerated stall (i.e. turn any harder and the wing will stall). Get it right and you can feel the pre-stall buffet through the controls the whole way around, followed by a nice bump as you go through your wake. Not easy, and very satisfying when you get it right
Pulling too hard and stalling is one way to get it wrong (and I guess with crossed controls you could in principle spin out of it?), not much of an issue (like any other stall, release some back pressure to reduce the loading and unstall the wing, wings level, nose to the horizon). More likely is to depart into a spiral dive, again not an issue but max rate turns are not something to try for the first time by yourself...
Pulling too hard and stalling is one way to get it wrong (and I guess with crossed controls you could in principle spin out of it?), not much of an issue (like any other stall, release some back pressure to reduce the loading and unstall the wing, wings level, nose to the horizon). More likely is to depart into a spiral dive, again not an issue but max rate turns are not something to try for the first time by yourself...
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Evo,
A stall at a high wing loading is very dangerous, and is deffinately something to worry about! OK, so it is huch harder to get the aircraft to that point, and there are more obvious warning signs (like aching arms pulling hard on the controls), but the reaction of the aircraft will be very rapid.
In the fireflies I flew during my PPL training, stalling at a high AoB resulted in an incipient spin - in otherwords a very rapid roll rate. Simple to get out of at that stage - relax backpressure straight away - but would scare the willies out of anyone who hadn't experienced it before and couldn't identify immediately what ws happening. And as I remember it, I didn't cover incipient spins in my PPL...
Wouldn't worry too much about a stall in a steep turn.
In the fireflies I flew during my PPL training, stalling at a high AoB resulted in an incipient spin - in otherwords a very rapid roll rate. Simple to get out of at that stage - relax backpressure straight away - but would scare the willies out of anyone who hadn't experienced it before and couldn't identify immediately what ws happening. And as I remember it, I didn't cover incipient spins in my PPL...
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High speed stall= wierd terminology. What you were approaching was more commanly known as the G-stall,
MVE explained it fine.
For a low hr PPl (no insult intended) this is something you should be fully aware of. Tis the cause of many a potential crash. i.e. turning finals a touche late / got too tight / tightening wind that you missed appreciating!!! - So, overbank and pull just a bit harder to prevent flying through the center line, speeds Ok at the usual reading / well above the usual stall speed AND - oops there she goes. You are reasonably likely to get a wing dropping, you are, without training, naturally, horribly likely to try to roll the wings level with stick whilst still pulling to stop the ground getting any bigger = depart spin crash burn die. The stall warner (where fitted) is doing its job just fine - it is warning you that pulling harder / going much slower = you gonna stall.
Just like any departure / stall: unload, full power, counter yaw with rudder, whilst out of buffet (unstalled) roll wings level and climb away to set up for a better circuit next time.
Get an instructer to teach you this, initially it is not a natural recovery procedure and certainly not one you should experience for the first time solo.
MVE explained it fine.
For a low hr PPl (no insult intended) this is something you should be fully aware of. Tis the cause of many a potential crash. i.e. turning finals a touche late / got too tight / tightening wind that you missed appreciating!!! - So, overbank and pull just a bit harder to prevent flying through the center line, speeds Ok at the usual reading / well above the usual stall speed AND - oops there she goes. You are reasonably likely to get a wing dropping, you are, without training, naturally, horribly likely to try to roll the wings level with stick whilst still pulling to stop the ground getting any bigger = depart spin crash burn die. The stall warner (where fitted) is doing its job just fine - it is warning you that pulling harder / going much slower = you gonna stall.
Just like any departure / stall: unload, full power, counter yaw with rudder, whilst out of buffet (unstalled) roll wings level and climb away to set up for a better circuit next time.
Get an instructer to teach you this, initially it is not a natural recovery procedure and certainly not one you should experience for the first time solo.
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A stall at a high wing loading is very dangerous, and is deffinately something to worry about!
And Dusty - you SHOULD have covered incipient spins for the PPL (but fully developed spins are not required).
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Incipient spins should be covered, but I wonder how often they are. In my case it was a bit of a joke, 15 minutes of trying to abuse a PA28 into droping a wing - or for that matter doing anything other than mush downwards. We didn't succeed.
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Very surprised that no one so far has mentioned the angle of attack.
Whatever aircraft you fly, it will stall at a particular angle of attack. Regardless of what speed you do, the stalling angle of attack remains the same.
The stall warner is a small vane that moves with the aircraft's angle of attack. The angle of attack when the warning sounds will be set below the stalling angle of attack and provides a warning in suficient time so that should you not be expecting it, you can take appropriate action.
In a steep turn the lift vector is tilted to one side and in order to maintain enough lift opposing the weight (vertical), lift must be increased. This is done by inreasing the angle of attack.
Increasing the angle of attack increases the drag. Consequently, unless sometyhing is done, the aircraft will slow, reducing lift and requiring a further increase in angle of attack. During a medium turn, we accept the slight loss of speed.
During a steep turn, the increase in angle of attack required is significant resulting in the angle of attack being closer to the stalling angle of attack and for something to be done to counteract the drag if a constant height and speed is required.
G force is the ratio of lift generated to weight. In theory, with big enough of and engine, it is possible to apply a G force to the aircraft by accelerating the aircraft rapidly to a great speed while maintaining the angle of attack constant........the aircraft would experience a great increase in lift at a constant angle of attack due to the increased speed of the airflow and G would be increased without getting any closer to the stalling angle of attack.
When dealing with the topic of loading, we must always be aware of Va.
Below Va, the aircraft will reach the stalling angle of attack before something breaks. Above Va, it is possible to bend/break the aircraft before reaching the stall!!
Furthermore, when talking about loading, remember that the aircraft is loaded in all directions......think about what a severe Yaw does to the horizontal loading of the fin and rudder!!!. Or think of the F16 in a vertical accelerating climb.....where is the highest loading acting then?
As for stalling in the turn.....one wing will have a higher angle of attack than the other. Consequently, one will stall before the other. We all know what happens when one wing stalls first and nothing is done to stop the wing drop!............although you might have to do nothing for a while in some aircraft while they roll from 60 left to 90 right.......others are a little more inclined to flick but no matter provided it is expected and at a safe height!
Regards,
DFC
PS. Aerofoil, you are now entering the more intersting phase of the training so enjoy expanding your experience of the aircraft envelope!!
Whatever aircraft you fly, it will stall at a particular angle of attack. Regardless of what speed you do, the stalling angle of attack remains the same.
The stall warner is a small vane that moves with the aircraft's angle of attack. The angle of attack when the warning sounds will be set below the stalling angle of attack and provides a warning in suficient time so that should you not be expecting it, you can take appropriate action.
In a steep turn the lift vector is tilted to one side and in order to maintain enough lift opposing the weight (vertical), lift must be increased. This is done by inreasing the angle of attack.
Increasing the angle of attack increases the drag. Consequently, unless sometyhing is done, the aircraft will slow, reducing lift and requiring a further increase in angle of attack. During a medium turn, we accept the slight loss of speed.
During a steep turn, the increase in angle of attack required is significant resulting in the angle of attack being closer to the stalling angle of attack and for something to be done to counteract the drag if a constant height and speed is required.
G force is the ratio of lift generated to weight. In theory, with big enough of and engine, it is possible to apply a G force to the aircraft by accelerating the aircraft rapidly to a great speed while maintaining the angle of attack constant........the aircraft would experience a great increase in lift at a constant angle of attack due to the increased speed of the airflow and G would be increased without getting any closer to the stalling angle of attack.
When dealing with the topic of loading, we must always be aware of Va.
Below Va, the aircraft will reach the stalling angle of attack before something breaks. Above Va, it is possible to bend/break the aircraft before reaching the stall!!
Furthermore, when talking about loading, remember that the aircraft is loaded in all directions......think about what a severe Yaw does to the horizontal loading of the fin and rudder!!!. Or think of the F16 in a vertical accelerating climb.....where is the highest loading acting then?
As for stalling in the turn.....one wing will have a higher angle of attack than the other. Consequently, one will stall before the other. We all know what happens when one wing stalls first and nothing is done to stop the wing drop!............although you might have to do nothing for a while in some aircraft while they roll from 60 left to 90 right.......others are a little more inclined to flick but no matter provided it is expected and at a safe height!
Regards,
DFC
PS. Aerofoil, you are now entering the more intersting phase of the training so enjoy expanding your experience of the aircraft envelope!!
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Neither spins, nor incipient spins were covered in my ppl training.
So one day post ppl, feeling brave, I asked an instructor would he do some with me. He said he wasn't current on spinning, and it wouldn't be safe for him to cover this with me, and that I'd better ask another instructor
While I very much appreciate his honesty, it did put me off the idea of doing them.....if they frightened him that much....
dp
So one day post ppl, feeling brave, I asked an instructor would he do some with me. He said he wasn't current on spinning, and it wouldn't be safe for him to cover this with me, and that I'd better ask another instructor
While I very much appreciate his honesty, it did put me off the idea of doing them.....if they frightened him that much....
dp
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Just because he is an instructor does not mean he has done a lot of spinning, especially with it not being in the syllabus anymore. I would suggest getting hold of an aeros instructor who SHOULD be happy with spinning- also, do it in an aircraft that has a reasonable spin, ie. not a pa28 or Cessna (Pa38 spins well - but don't look back at the tail 
).
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Stall speed = Square root of the `g` applied to the aircraft
Example
60 bank turn with 2 `g` applied to stay level, the stall speed will increase by approx 1.4.
Not massively precise but close enough if you need a rough calculation.
Dont know about the knot per 2 degrees of bank but this works on more high performance aircraft that pull `g` to turn.
Example
60 bank turn with 2 `g` applied to stay level, the stall speed will increase by approx 1.4.
Not massively precise but close enough if you need a rough calculation.
Dont know about the knot per 2 degrees of bank but this works on more high performance aircraft that pull `g` to turn.
The stall speed varies as a function of the load factor and not angle of bank. The stall speeds quoted in the POH are all based on 1g, and in testing, great pains are taken to ensure that the load is 1 g by reducing speed at 1 knt per second.
Any more or less than 1g, the stall speed will differ. Quite simply, it is the square root of the load factor. So if your clean stall speed is 50 knots, at 2g it will be 70.7 knots (1.41 x 50), at 3g it will be 86.6 knots (1.73 x 50), at 4g it will be 100 knots (2 x 50), at 9g - the wings would have come off! But if they hadn't it would be 150 knots. And at less than 1g, you can see speeds on the ASI at less than basic stall speeds. At a 0g bunt, you can't stall the aircraft as there is no load on the wings.
When I teach stalling, I demo this to the student. I get him to tell me at what speed we have seen the aircraft stall. I then tell him it's possible to fly the aircraft at a speed lower than that and demo it with a gentle wingover and about 1/2 a g getting the ASI to read less than the noticed speed. The key to this part of the exercise is to point out that there is no buffet and therefore the wing is not stalled. I then fly the aircraft in a level 60 degree angle of bank turn which should be at 2g and pull back to the light buffet noticing the speed. Another point to this exercise is to demo that the aircraft can be stalled or still flying in attitiudes other than the one we have become accustomed to.
Buffet is the only true indication that the wing is stalling - this is the key to the whole exercise. It's not the stall warner - that's only there for certification reasons and it may be unserviceable or not be installed in the first place. I know of no GA aircraft that have such poor stall characteristics that they do not give adequate aerodynamic warning.
A lot of this should have been covered by briefing if not in the air.
Any more or less than 1g, the stall speed will differ. Quite simply, it is the square root of the load factor. So if your clean stall speed is 50 knots, at 2g it will be 70.7 knots (1.41 x 50), at 3g it will be 86.6 knots (1.73 x 50), at 4g it will be 100 knots (2 x 50), at 9g - the wings would have come off! But if they hadn't it would be 150 knots. And at less than 1g, you can see speeds on the ASI at less than basic stall speeds. At a 0g bunt, you can't stall the aircraft as there is no load on the wings.
When I teach stalling, I demo this to the student. I get him to tell me at what speed we have seen the aircraft stall. I then tell him it's possible to fly the aircraft at a speed lower than that and demo it with a gentle wingover and about 1/2 a g getting the ASI to read less than the noticed speed. The key to this part of the exercise is to point out that there is no buffet and therefore the wing is not stalled. I then fly the aircraft in a level 60 degree angle of bank turn which should be at 2g and pull back to the light buffet noticing the speed. Another point to this exercise is to demo that the aircraft can be stalled or still flying in attitiudes other than the one we have become accustomed to.
Buffet is the only true indication that the wing is stalling - this is the key to the whole exercise. It's not the stall warner - that's only there for certification reasons and it may be unserviceable or not be installed in the first place. I know of no GA aircraft that have such poor stall characteristics that they do not give adequate aerodynamic warning.
A lot of this should have been covered by briefing if not in the air.
Not so N, but still FG
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Hey, controversy fans, whaddya think?
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.
Discuss.
Proposition 2: Any instructor who does not brief their PPL student in advance about what happens during steep turns, about the dangers/needs for caution incidental to steep turning, and about why this is significant to everyday flying, should, at the least, be taken behind the hangar by the CFI and given a polite, friendly, caring, sharing, mentoring, right good kicking.
Discuss.
PS: Aerofoil: whether or not you presently have any interest in aerobatics, if you get the chance, pre or post PPL, to have a trip with a spinning/aeros instructor, you could perhaps explore further pulling to the buffet, in the manner mentioned by Mr Winterland, and feeling the effects of the g. If you find that informative, you might then ask the instructor to show you a spin and recovery, and maybe let you try one or two yourself.
PPS: I agree with everything said by Flyin Dutch in the posting below.
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.
Discuss.
Proposition 2: Any instructor who does not brief their PPL student in advance about what happens during steep turns, about the dangers/needs for caution incidental to steep turning, and about why this is significant to everyday flying, should, at the least, be taken behind the hangar by the CFI and given a polite, friendly, caring, sharing, mentoring, right good kicking.
Discuss.
PS: Aerofoil: whether or not you presently have any interest in aerobatics, if you get the chance, pre or post PPL, to have a trip with a spinning/aeros instructor, you could perhaps explore further pulling to the buffet, in the manner mentioned by Mr Winterland, and feeling the effects of the g. If you find that informative, you might then ask the instructor to show you a spin and recovery, and maybe let you try one or two yourself.
PPS: I agree with everything said by Flyin Dutch in the posting below.
Last edited by FNG; 11th Dec 2003 at 01:45.
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Obviously we have to be careful to judge an instructor's performance based on just this posting but if your pupil writes:
There is something fundamentally wrong with either the basic knowledge of the subject or the ability to transfer sound knowledge.
FD
My instructor told me that was the high speed stall warner.
FD
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DFC, I recon no one mentioned AoA cos they didn't think it practically relevent in a GA puddle-jumper when replying to a new PPl.
AoA guage not fitted in any I regularly get to play with!
Shame really cos AoA IS the never failing winner in the race to never depart.
Edit addition: FNG agreed with all propositions + sack the oxygen stealing waste of space
I shall have anuvver glass of red and wait.
AoA guage not fitted in any I regularly get to play with!
Shame really cos AoA IS the never failing winner in the race to never depart.
Edit addition: FNG agreed with all propositions + sack the oxygen stealing waste of space
I shall have anuvver glass of red and wait.
Dan - wash your mouth out! Don't forget that, in a level turn, N (which is L/W) = Sec (theta), where theta is the angle of bank! And, as the indicated stalling speed varies with the square root of N, stall speed is indeed dependant upon AoB in a level steep turn!