An aerodynamics question (for experts only)
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The analogy of the resting stone isn't entirely incorrect. It is still doing something and it can be argued that all the forces acting on it are in equilibrium (good word huh! 
). That will continue to be the case until it is affected by an acceleration - thrust created by someone kicking the stone, perhaps?
Anyway, it doesn't adequately illustrate the point but the reality is that in S+L flight, all the forces acting on an aeroplane are similarly in equilibrium until something is changed. I've deliberately avoided any reference to 3 or 4 force (or whatever) models because, even if there are a thousand forces acting on the aeroplane in S+L flight, they are ALL in equilibrium.
). That will continue to be the case until it is affected by an acceleration - thrust created by someone kicking the stone, perhaps?Anyway, it doesn't adequately illustrate the point but the reality is that in S+L flight, all the forces acting on an aeroplane are similarly in equilibrium until something is changed. I've deliberately avoided any reference to 3 or 4 force (or whatever) models because, even if there are a thousand forces acting on the aeroplane in S+L flight, they are ALL in equilibrium.
OK gloves are off this time...
How many actually get the idea?
The idea that we use mathematical models to make difficult things easier to understand.
Not to make things more complicated for people that know less about it.The definition of a model is a simplified version of what's really going on right?Please don't argue on this one.
For those of you that are NOT flight instructors,here's the shocker:
We train people to be a safe proficient PRIVATE PILOT,not a rocket scientist.
That's one of the biggest problems in aviation by the way.
All the smoke & mirrors to impress the non-initiated.
Go to an airport on a weekend day and watch all the know-it-alls
in their regalia(there's a thread on this one) pretend they're Gods gift to aviation as they try to impress their non-flying victims.
I'll admit I'll lose a discussion with an aeronautical engineer but the point is wether it is of any use in actual flying.Designing yes,real life no.
How many of you know what's actually happening to your car as you drive,let alone in your engine.Does'nt stop anybody from driving though does it?
3-forces...4-forces peace to all of you..I've said my thing.
Keep the pointy end in front and the wheels down..you'll be awright...
How many actually get the idea?
The idea that we use mathematical models to make difficult things easier to understand.
Not to make things more complicated for people that know less about it.The definition of a model is a simplified version of what's really going on right?Please don't argue on this one.
For those of you that are NOT flight instructors,here's the shocker:
We train people to be a safe proficient PRIVATE PILOT,not a rocket scientist.
That's one of the biggest problems in aviation by the way.
All the smoke & mirrors to impress the non-initiated.
Go to an airport on a weekend day and watch all the know-it-alls
in their regalia(there's a thread on this one) pretend they're Gods gift to aviation as they try to impress their non-flying victims.
I'll admit I'll lose a discussion with an aeronautical engineer but the point is wether it is of any use in actual flying.Designing yes,real life no.
How many of you know what's actually happening to your car as you drive,let alone in your engine.Does'nt stop anybody from driving though does it?
3-forces...4-forces peace to all of you..I've said my thing.
Keep the pointy end in front and the wheels down..you'll be awright...
PPRuNeaholic
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Yes, I used to be an instructor - and a Chief Flying Instructor at one stage too. That was a real looooong time ago but, back then, it was common to talk about forces being in "equilibrium" in S+L flight. The only way this could be shown, during a blackboard/whyteboard briefing was via the 4-forces model.
Lift and Weight were equal to one another, so it readily made sense that they cancelled each other out. Thrust and Drag were clearly equal to one another and it therefore made sense that they, too, cancelled each other out.
Every student I trained in this concept understood the concept straight off. Indeed, after a few very carefully chosen words at the start of the discussion, the trainees would be telling ME how it all happened! I always love it when a plan comes together!
That provided the foundation upon which to build the briefing on "climbing", where you MUST have a "Total Resultant" vector - otherwise there is NO climb. Again, I could start the discussion with a few carefully chosen words and stand back to let the trainees tell me how it all happened.
And, ya know, the thing is that I'd learned it all in much the same way. I did smplify it. I really was easy to understand and, above all, it was also very easy to demonstrate in flight!
Well, that's my hand grenade into the topic, but it all worked very well over the 10 years that I spent as an instructor.
Lift and Weight were equal to one another, so it readily made sense that they cancelled each other out. Thrust and Drag were clearly equal to one another and it therefore made sense that they, too, cancelled each other out.
Every student I trained in this concept understood the concept straight off. Indeed, after a few very carefully chosen words at the start of the discussion, the trainees would be telling ME how it all happened! I always love it when a plan comes together!
That provided the foundation upon which to build the briefing on "climbing", where you MUST have a "Total Resultant" vector - otherwise there is NO climb. Again, I could start the discussion with a few carefully chosen words and stand back to let the trainees tell me how it all happened.
And, ya know, the thing is that I'd learned it all in much the same way. I did smplify it. I really was easy to understand and, above all, it was also very easy to demonstrate in flight!
Well, that's my hand grenade into the topic, but it all worked very well over the 10 years that I spent as an instructor.
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The 'level' bit isn't necessary for the forces to be in equilibrium. All that is required is that the vertical and horizontal velocities are constant. If you're going straight and climbing at 500ft/min then you are in equilibrium. You are only out of equilibrium when you are accelerating (either horizontally or vertically) e.g. when transitioning from straight flight to a climb.
So
isn't correct. (And I say that pulling my forelock because I dare say you're a far better pilot that I will ever be!)
B2B2: Bang-on right about the model (and why it doesn’t matter that much!)
So
That provided the foundation upon which to build the briefing on "climbing", where you MUST have a "Total Resultant" vector - otherwise there is NO climb.
B2B2: Bang-on right about the model (and why it doesn’t matter that much!)
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RR ... I wouldn't have thought there was any reason for a cynical comment, so I've now learned something from you. In any event, I intend to overlook it and merely ask how one achieves a climb, from S+L, in the first instance, without disturbing the aircraft's equilibrium - as when transitioning "from straight flight to a climb"?
Oh well, just cos I enjoy an argument - "In straight and level flight at constant speed, ie flight at constant altitude and speed, all the forces cancel out". I would suggest - almost, but not quite!! If you set off in straight and level flight as above (and keep going!) you will end up back where you started having flown a circular path around the earth. There must be a resultant centripetal force acting towards the centre of the earth, ie in the same direction as the weight vector.
Forgive me for being flippant but it is a very quiet Sunday morning.
Forgive me for being flippant but it is a very quiet Sunday morning.
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Hi OzExpat, it wasn't meant to be a cynical comment! As B2N2 said, these models are just about helping you understand the basics - it doesn't help you fly. All I was trying to say was that flying's about getting from A to B safely and that is far more about experience and training than technical discussions about forces. I'm a 200 hour PPL and I KNOW I have a huge amount to learn. Sorry if it appeared cynical.
You're right about the forces being out of equilibrium during the vertical acceleration stage between level and climbing at a constant rate. During the constant climb rate stage they are back in equilibrium.
You're right about the forces being out of equilibrium during the vertical acceleration stage between level and climbing at a constant rate. During the constant climb rate stage they are back in equilibrium.
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During a climb forces are certainly not in equilibrium.
Upward force exceeds gravitational force, hence climb.
If they were in equilibrium, as in straight and level flight, there would be no climb.
If you are looking for the acceleration part of F=(W/g)xa, the a is the gravitational acceleration you are overcoming.
Upward force exceeds gravitational force, hence climb.
If they were in equilibrium, as in straight and level flight, there would be no climb.
If you are looking for the acceleration part of F=(W/g)xa, the a is the gravitational acceleration you are overcoming.
Sorry Bluskis, I can not bring myself to agree to that one -
"Upward force exceeds gravitational force, hence acceleration upwards!!"
When they are in equilibrium your vertical speed will be constant.
"Upward force exceeds gravitational force, hence acceleration upwards!!"
When they are in equilibrium your vertical speed will be constant.
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Bluskis-
In a steady state climb (constant direction, rate of climb and airspeed) the forces acting on an aircraft are in equilibrium. Furthermore, lift is less than weight in this state. The NASA site referenced earlier in this thread (p 2 I think) is an excellent resource for this kind of issue. So is AC Kermode's primer on Aerodynamics - I can't remember the exact title. It's up to edition 10 now I think.
Your use of the equation F = W/gxa is out of context. In a steady state climb the aircraft is not accelerating - all speeds, rates of climb, directions are constant and unchanging in direction and magnitude. Thus "a" is zero. Thus net (total, sum, add-em-all-up-and-what-do-you-get) force F is zero, as many preceding posts have stated.
Yes, lift really is less than weight and forces are in equilibrium.
Really!
happy flying,
O8
In a steady state climb (constant direction, rate of climb and airspeed) the forces acting on an aircraft are in equilibrium. Furthermore, lift is less than weight in this state. The NASA site referenced earlier in this thread (p 2 I think) is an excellent resource for this kind of issue. So is AC Kermode's primer on Aerodynamics - I can't remember the exact title. It's up to edition 10 now I think.
Your use of the equation F = W/gxa is out of context. In a steady state climb the aircraft is not accelerating - all speeds, rates of climb, directions are constant and unchanging in direction and magnitude. Thus "a" is zero. Thus net (total, sum, add-em-all-up-and-what-do-you-get) force F is zero, as many preceding posts have stated.
Yes, lift really is less than weight and forces are in equilibrium.
Really!
happy flying,
O8
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Kermode.
Bluskis - and friends..
A C Kermode. Mechanics of Flight. Edition 10. Page 229. "Climbing".
First, I need you to imagine a picture - let's, for the sake of continuity, call it "Figure 7.1".
Imagine a picture of an aircraft - side view. Draw on it the four arrows that we are all familiar with. Identify them with the the famous four - L, D, T and, W. For those with bad memories - L, represents Lift and is drawn vertically upwards, W represents Weight and is drawn vertically downwards, T represents Thrust and is drawn horizontally (pointing to the left), D represents drag and is drawn pointing to the right. All the above assumes you have drawn the aircraft the right way up and flying from right to left.
Now - leave the W arrow still pointing vertically downwards, but rotate everything else in the picture - to represent a climb. The amount that you have rotated the picture, measured in degrees, will represent the "climb angle", and will be called "a". Thats a small letter "a" (presumably "alpha").
Imagine now, your thrust arrow is inclined upwards at angle "a", your drag arrow is inclined downwards at angle "a", and the lift arrow is inclined backwards at angle "a". Weight, still vertically downwards. Got it??
Onwards to Kermode....
Climbing
During level flight the power of the engine must produce, via the propeller, jet or rocket, a thrust equal to the drag of the aeroplane at that particular speed of flight. If now the engine has some reserve of power in hand, and if the throttle is further opened, either -
(a) The pilot can put the nose down slightly, and maintain level flight at an increased speed and decreased angle of attack, or
(b) The aeroplane will commence to climb
A consideration of the forces which act upon an aeroplane during a climb is interesting, but slightly more complicated than the other cases which we have considered.
Assuming that the path actually travelled by the aeroplane is in the same direction as the thrust, then the forces will be as shown in Figure 7.1
If "a" is the angle of climb, and if we resolve the forces parallel and at right angles to the direction of flight, we obtain two equations -
(1) T = D + W sin "a"
(2) L = W cos "a"
Translated into non-mathematical language, the first of these equations tells us that during a climb the thrust needed is greater than the drag and increases with the steepness of the climb. This is what we would expect. If a vertical climb were possible, "a" would be 90° and therefore sin "a" would be 1, so the first equation would become T = D + W, which is obviously true because in such an extreme case the thrust would have the opposition of both the weight and the drag. Similarly if "a" = 0° (i.e. there is no climb), sin "a" = 0. Therefore W sin "a" = 0. Therefore T = D, the condition which we have already established for straight and level flight.
The second equation tells us that the lift is less than the weight, which is rather interesting because one often hears it said that an aeroplane climbs when the lift is greater than the weight! One must admit, however, that the misunderstanding is largely due to the rather curious definition which we have assigned to the word 'lift'. Let us consider the second equation under extreme conditions. If the climb were vertical, cos 90° = 0. Therefore L = 0. So that in a vertical climb we have no lift. This simply means that all the real lift is provided by the thrust, the wings doing nothing at all to help. If, on the other hand, "a" = 0, cos "a" = 1, and therefore L = W, which we already know to be the condition of straight and level flight.
(Phew)
A C Kermode. Mechanics of Flight. Edition 10. Page 229. "Climbing".
First, I need you to imagine a picture - let's, for the sake of continuity, call it "Figure 7.1".
Imagine a picture of an aircraft - side view. Draw on it the four arrows that we are all familiar with. Identify them with the the famous four - L, D, T and, W. For those with bad memories - L, represents Lift and is drawn vertically upwards, W represents Weight and is drawn vertically downwards, T represents Thrust and is drawn horizontally (pointing to the left), D represents drag and is drawn pointing to the right. All the above assumes you have drawn the aircraft the right way up and flying from right to left.
Now - leave the W arrow still pointing vertically downwards, but rotate everything else in the picture - to represent a climb. The amount that you have rotated the picture, measured in degrees, will represent the "climb angle", and will be called "a". Thats a small letter "a" (presumably "alpha").
Imagine now, your thrust arrow is inclined upwards at angle "a", your drag arrow is inclined downwards at angle "a", and the lift arrow is inclined backwards at angle "a". Weight, still vertically downwards. Got it??
Onwards to Kermode....
Climbing
During level flight the power of the engine must produce, via the propeller, jet or rocket, a thrust equal to the drag of the aeroplane at that particular speed of flight. If now the engine has some reserve of power in hand, and if the throttle is further opened, either -
(a) The pilot can put the nose down slightly, and maintain level flight at an increased speed and decreased angle of attack, or
(b) The aeroplane will commence to climb
A consideration of the forces which act upon an aeroplane during a climb is interesting, but slightly more complicated than the other cases which we have considered.
Assuming that the path actually travelled by the aeroplane is in the same direction as the thrust, then the forces will be as shown in Figure 7.1
If "a" is the angle of climb, and if we resolve the forces parallel and at right angles to the direction of flight, we obtain two equations -
(1) T = D + W sin "a"
(2) L = W cos "a"
Translated into non-mathematical language, the first of these equations tells us that during a climb the thrust needed is greater than the drag and increases with the steepness of the climb. This is what we would expect. If a vertical climb were possible, "a" would be 90° and therefore sin "a" would be 1, so the first equation would become T = D + W, which is obviously true because in such an extreme case the thrust would have the opposition of both the weight and the drag. Similarly if "a" = 0° (i.e. there is no climb), sin "a" = 0. Therefore W sin "a" = 0. Therefore T = D, the condition which we have already established for straight and level flight.
The second equation tells us that the lift is less than the weight, which is rather interesting because one often hears it said that an aeroplane climbs when the lift is greater than the weight! One must admit, however, that the misunderstanding is largely due to the rather curious definition which we have assigned to the word 'lift'. Let us consider the second equation under extreme conditions. If the climb were vertical, cos 90° = 0. Therefore L = 0. So that in a vertical climb we have no lift. This simply means that all the real lift is provided by the thrust, the wings doing nothing at all to help. If, on the other hand, "a" = 0, cos "a" = 1, and therefore L = W, which we already know to be the condition of straight and level flight.
(Phew)
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GW ... I couldn't have said it better meself! Really!! But, seriously, thanks for that - I'm in the same situation as bluskis, in that my now very aged copy of Kermode's wisdom is many miles away from me right now... 
RR ... the written word can often be subject to misinterpretation, except perhaps in Kermode's turn of phrase. We can't all be as good at it as he is.
Geez, I wonder what edition of his book I have?
RR ... the written word can often be subject to misinterpretation, except perhaps in Kermode's turn of phrase. We can't all be as good at it as he is.
Geez, I wonder what edition of his book I have?
All,
When I look at this circular discussion ( if you take it all to the nth degree, using your handy backyard Cray, you will only ever wind up with an approximation of the answer) I am reminded of an Australian cartoon character, Ding Duck, in the Swamp series.
A cartoon, which was enlarged and graced the door of the then Dept. of Aviation ( or whatever the airstapo was then called) examination hall in Sydney showed the question: What are the four forces acting on an aircraft in flight.
The happless Ding's answer was: Lift, Weight, Thrust and the Department of Aviation.
Tootle pip !!
When I look at this circular discussion ( if you take it all to the nth degree, using your handy backyard Cray, you will only ever wind up with an approximation of the answer) I am reminded of an Australian cartoon character, Ding Duck, in the Swamp series.
A cartoon, which was enlarged and graced the door of the then Dept. of Aviation ( or whatever the airstapo was then called) examination hall in Sydney showed the question: What are the four forces acting on an aircraft in flight.
The happless Ding's answer was: Lift, Weight, Thrust and the Department of Aviation.
Tootle pip !!
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GW
Thanks for the extract.
I was confusing the increase in upward force required for the climb compared with straight and level flight ,with equilibrium of the forces which Kermode clearly shows exists in a stable climb.
Thanks for the extract.
I was confusing the increase in upward force required for the climb compared with straight and level flight ,with equilibrium of the forces which Kermode clearly shows exists in a stable climb.
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The basic problem here is that all sorts of people do not have even the most basic understanding of mechanics.
If you want to talk about forces at all, then the student has got to have a proper understanding of the basic laws of motion. Otherwise the best that you can hope for is that they will remember individual 'sound bites' of your explanation.
Generally, instructors tend to assume knowledge.
The average person on the street does not understand friction, so their everyday experience tell them that when you stop pushing something, its slows down and stops. As a result, they don't really understand what a force is, and hence understanding Newton is just a no hoper.
The other problem is that straight and level flight is the obvious first thing to talk about. Sadly, its not the best way to do it. In straight and level, the standard 4 forces are conveniently 90 degrees apart. So the student gets the idea (subconsciously, even though you haven't said it) that all the forces are defined in those orientations.
I have found it useful to just draw introductory diagrams of different flight phases to show how the forces are defined (whilst stating any simplifications). Then you've got a basis for teaching S&L without causing miscomprehension.
Then, to teach the detail of different flight phases, you have to do the same sort of thing as the air exercise.
e.g. Climbing. To teach, you show student how to start, maintain, and finish. Basically 3 different exercises.
To teach the theory, you need to differentiate between steady flight paths, and changing flight paths. In the former, the forces must be IN balance, in the latter they must not. To enter climb, must have more lift to alter flight path. To maintain ..(bleh, can't be bothered to spell it out). To return to level flight, must reduce to level off, then increase back to match weight again to avoid descent.
But fundamentally, most students have forgotten (if they ever knew) their basic science, and the pre-flight briefing just isn't long enough to rectify that knowledge gap.
So basically I'm saying that if one is going to use force diagrams to teach, then I feel it is essential to get them right. On the other hand, what training value is actually derived from so doing?
In some ways I'm with B2N2 as far as the necessity of theory goes. But if someone wants to know, then get it right or leave well alone!
CPB
If you want to talk about forces at all, then the student has got to have a proper understanding of the basic laws of motion. Otherwise the best that you can hope for is that they will remember individual 'sound bites' of your explanation.
Generally, instructors tend to assume knowledge.
The average person on the street does not understand friction, so their everyday experience tell them that when you stop pushing something, its slows down and stops. As a result, they don't really understand what a force is, and hence understanding Newton is just a no hoper.
The other problem is that straight and level flight is the obvious first thing to talk about. Sadly, its not the best way to do it. In straight and level, the standard 4 forces are conveniently 90 degrees apart. So the student gets the idea (subconsciously, even though you haven't said it) that all the forces are defined in those orientations.
I have found it useful to just draw introductory diagrams of different flight phases to show how the forces are defined (whilst stating any simplifications). Then you've got a basis for teaching S&L without causing miscomprehension.
Then, to teach the detail of different flight phases, you have to do the same sort of thing as the air exercise.
e.g. Climbing. To teach, you show student how to start, maintain, and finish. Basically 3 different exercises.
To teach the theory, you need to differentiate between steady flight paths, and changing flight paths. In the former, the forces must be IN balance, in the latter they must not. To enter climb, must have more lift to alter flight path. To maintain ..(bleh, can't be bothered to spell it out). To return to level flight, must reduce to level off, then increase back to match weight again to avoid descent.
But fundamentally, most students have forgotten (if they ever knew) their basic science, and the pre-flight briefing just isn't long enough to rectify that knowledge gap.
So basically I'm saying that if one is going to use force diagrams to teach, then I feel it is essential to get them right. On the other hand, what training value is actually derived from so doing?
In some ways I'm with B2N2 as far as the necessity of theory goes. But if someone wants to know, then get it right or leave well alone!
CPB
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CPB ... okay, if nobody else is going to take issue with what you've just said, I'll kick the ball into the air. First of all, I resent your implication that no other instructor gets the basics right with briefings for trainees. Do you really believe that every other instructor, or former instructor, around the world, is so completely idiotic as to overlook such a fundamental aspect as the way we show the forces in a (massively) simplified diagram?
What you say might well be the case, in your experience, in your part of the world, but it certainly is not the case in my experience, in my part of the world. So, please, no lofty generalisations.
Next, you've ignored one of the fundamentals of aerodynamics in saying that "lift" is increased in the climb. I invite you to read back over the quote from AC Kermode, made by GoneWest, and then tell us about lift in the climb.
What you say might well be the case, in your experience, in your part of the world, but it certainly is not the case in my experience, in my part of the world. So, please, no lofty generalisations.
Next, you've ignored one of the fundamentals of aerodynamics in saying that "lift" is increased in the climb. I invite you to read back over the quote from AC Kermode, made by GoneWest, and then tell us about lift in the climb.
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Relax Ozexpat.
I said "generally, instructors..."
not "all flying instructors..."
Which means, off course, exactly what you said. I.E. generally, but not always, in my experience. And I also mean 'instructors including myself', not 'other instructors because I'm such a genius'. I've certainly made the mistake of assuming knowledge on the part of the student. And as a student, not just in flying, I've had the reverse situation.e.g.
"We're going to start by looking at M32"
"What's an M32?"
"Number 32 in the catalog of Messier Objects"
"What's a Messier Object?"
Having said that, I don't think most flying instructors are that hot on the basics of mechanics. But I don't think they need to be, in most cases, so why worry? I on the other hand spent several years teaching commercial groundschool, but am by contrast, at best a mediocre flying instructor.
As far as your last paragraph is concerned, I did not say ' "lift" is increased in the climb'. I said that lift is increased to enter a climb. For most average powered aircraft in mundane flight phases this is true.
Kermode says that the aircraft climbs because power is increased. That excerpt however doesn't tell us the mechanism by which the climb is established. His aircraft just suddenly, instantly, starts climbing and miraculously points its thrust vector along its new flight path.
In other words, in this excerpt, Kermode is not even attempting to discuss the transition from level flight to climb. He is instead interested in studying the forces once established in the climb.
Hopefully I've made myself a bit clearer and you can see where I'm coming from. If you actually want a discussion of the forces involved in entering, maintaining, and leaving the climb I'm quite happy to continue. I got the impression however that you were just pouncing on a perceived error on my part though, so I don't propose to continue unless you actually wish it.
CPB
I said "generally, instructors..."
not "all flying instructors..."
Which means, off course, exactly what you said. I.E. generally, but not always, in my experience. And I also mean 'instructors including myself', not 'other instructors because I'm such a genius'. I've certainly made the mistake of assuming knowledge on the part of the student. And as a student, not just in flying, I've had the reverse situation.e.g.
"We're going to start by looking at M32"
"What's an M32?"
"Number 32 in the catalog of Messier Objects"
"What's a Messier Object?"
Having said that, I don't think most flying instructors are that hot on the basics of mechanics. But I don't think they need to be, in most cases, so why worry? I on the other hand spent several years teaching commercial groundschool, but am by contrast, at best a mediocre flying instructor.
As far as your last paragraph is concerned, I did not say ' "lift" is increased in the climb'. I said that lift is increased to enter a climb. For most average powered aircraft in mundane flight phases this is true.
Kermode says that the aircraft climbs because power is increased. That excerpt however doesn't tell us the mechanism by which the climb is established. His aircraft just suddenly, instantly, starts climbing and miraculously points its thrust vector along its new flight path.
In other words, in this excerpt, Kermode is not even attempting to discuss the transition from level flight to climb. He is instead interested in studying the forces once established in the climb.
Hopefully I've made myself a bit clearer and you can see where I'm coming from. If you actually want a discussion of the forces involved in entering, maintaining, and leaving the climb I'm quite happy to continue. I got the impression however that you were just pouncing on a perceived error on my part though, so I don't propose to continue unless you actually wish it.
CPB
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CPB ... yes, I probably could've phrased my previous post a little less stridently. I did, however, believe that you were saying something that was a tad too generalised. I accept that not all instructors (ground and flight) are good instructors and, indeed, everyone can have an "off-day" once in a while.
After several thousand hours instructing, I found it was still possible to assume a certain amount of knowledge on the part of the trainee, sometimes. I suspect there's probably some "human factors" stuff at work there.
The passage that GW quoted from Kermode does, however briefly, touch on the forces at work in the initiation of a climb. That bit about what happens when you have reserve engine power in S+L flight. Using that additional thrust, without a change in angle of attack, will initiate the climb.
Thus, thrust contributes to lift to create the "total reaction" vector, which is how this came up in one of my earlier posts. This is the basis I've used in briefings to explain to a trainee why, in practice, thust needs to be applied to initiate the climb. Of course, such briefings are necessarily tailored to the typical type of trainng aeroplane which is not overly endowed with thrust and, naturally, that point must also be made in the briefing.
This works out in practice too because, while a climb can often be initiated simply by converting excess speed to height, such a climb cannot be sustained without an increase in thrust. This is pretty easily demonstrated in flight. One must then touch on the fact that, when you run of out reserve thrust, you're playing with a stall to attempt further climb.
When I was trained as an instructor, it was emphasised that we need to keep briefings as short and simple as possible, without bypassing the essentials. Also, that it was entirely appropriate to give a briefing that covered all the essentials for that exercise alone.
Thus, the S+L briefing was intended to teach the student why it is necessary to have particular combinations of power and attitude to maintain S+L flight. If the basics of this are covered well at that stage, it is much easier for the student to grasp the concepts related to initiation of a climb. And, of course. to the subsequent maintenance of the climb.
It is certainly useful to start a briefing on climbing by reviewing our defined forces in S+L. Indeed, it is always a good idea to start any new topic with a review of what the student should already know. This is where shortcuts can often occur, because an instructor can be easily persuaded to assume a certain level of knowledge by the student.
All things considered, I suspect we've been talking more about instructional technique than the material itself. It had not been my intention to hijack the debate along those lines. Still, its clear that we all need to exhange views of such matters periodically, as it helps to keep us all up to speed and, thereby, to make us all better instructors.
There's one helluva thin dividing line between giving the student as much as is needed to understand what is about to be taught in the aeroplane, and complicating the whole thing with too much theory. This is the line that each instructor walks every day because we all need to know more about the subject than we'll normally need to teach. This was another point that came up in my own training because you never knew when a student was going to ask one of them really complex questions!
After several thousand hours instructing, I found it was still possible to assume a certain amount of knowledge on the part of the trainee, sometimes. I suspect there's probably some "human factors" stuff at work there.
The passage that GW quoted from Kermode does, however briefly, touch on the forces at work in the initiation of a climb. That bit about what happens when you have reserve engine power in S+L flight. Using that additional thrust, without a change in angle of attack, will initiate the climb.
Thus, thrust contributes to lift to create the "total reaction" vector, which is how this came up in one of my earlier posts. This is the basis I've used in briefings to explain to a trainee why, in practice, thust needs to be applied to initiate the climb. Of course, such briefings are necessarily tailored to the typical type of trainng aeroplane which is not overly endowed with thrust and, naturally, that point must also be made in the briefing.
This works out in practice too because, while a climb can often be initiated simply by converting excess speed to height, such a climb cannot be sustained without an increase in thrust. This is pretty easily demonstrated in flight. One must then touch on the fact that, when you run of out reserve thrust, you're playing with a stall to attempt further climb.
When I was trained as an instructor, it was emphasised that we need to keep briefings as short and simple as possible, without bypassing the essentials. Also, that it was entirely appropriate to give a briefing that covered all the essentials for that exercise alone.
Thus, the S+L briefing was intended to teach the student why it is necessary to have particular combinations of power and attitude to maintain S+L flight. If the basics of this are covered well at that stage, it is much easier for the student to grasp the concepts related to initiation of a climb. And, of course. to the subsequent maintenance of the climb.
It is certainly useful to start a briefing on climbing by reviewing our defined forces in S+L. Indeed, it is always a good idea to start any new topic with a review of what the student should already know. This is where shortcuts can often occur, because an instructor can be easily persuaded to assume a certain level of knowledge by the student.
All things considered, I suspect we've been talking more about instructional technique than the material itself. It had not been my intention to hijack the debate along those lines. Still, its clear that we all need to exhange views of such matters periodically, as it helps to keep us all up to speed and, thereby, to make us all better instructors.
There's one helluva thin dividing line between giving the student as much as is needed to understand what is about to be taught in the aeroplane, and complicating the whole thing with too much theory. This is the line that each instructor walks every day because we all need to know more about the subject than we'll normally need to teach. This was another point that came up in my own training because you never knew when a student was going to ask one of them really complex questions!