Throttle and elevator - which does what?
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Throttle and elevator - which does what?
One thing you should be aware of - flight simulator and reality are two different kettle of fish. For example, I always assumed that the elevator was the "up/down" control rather than speed control.....
The instructors at our club say they can always tell those who had dabbled with Flight Simulators before they started their PPL because of certain habits so if you're going to be serious about flying, then forget Flight Simulators until you have mastered certain exercises and understand what the plane is doing. Only then will a flight simulator allow you to properly relate to what you've done, practice the exercise else the instructor will be forced to not only teach you how to fly but also eliminate bad habits.
The worst case I remember hearing them recall was one student who just wouldn't keep his right hand on the throttle whilst in the circuit coming into land, he had gotten so used to flying FSX having both hands on the yoke, that he had bought himself, when on final, it took 6 additional hours of circuits just to get rid of that bad habit.....
The instructors at our club say they can always tell those who had dabbled with Flight Simulators before they started their PPL because of certain habits so if you're going to be serious about flying, then forget Flight Simulators until you have mastered certain exercises and understand what the plane is doing. Only then will a flight simulator allow you to properly relate to what you've done, practice the exercise else the instructor will be forced to not only teach you how to fly but also eliminate bad habits.
The worst case I remember hearing them recall was one student who just wouldn't keep his right hand on the throttle whilst in the circuit coming into land, he had gotten so used to flying FSX having both hands on the yoke, that he had bought himself, when on final, it took 6 additional hours of circuits just to get rid of that bad habit.....
Last edited by Steve6443; 24th Jun 2013 at 07:48.
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Londonboi - there you have it. Conflicting information some of it excellent and some of it rubbish. I suggest that you go to an aero club and talk to them.
Uneducated rubbish!
'In a powered aircraft throttle controls speed'
Uneducated rubbish!
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DeeCee
Uneducated rubbish!
Please enlighten us all with an educated response using your superior knowledge.
DeeCee
Uneducated rubbish!
Please enlighten us all with an educated response using your superior knowledge.
Most a/c engines like to run at a constantly steady speed. They are not like cars, & they don't have a gearbox to regulate speed. Therefore a/c tend to fly straight & level at a relatively fixed cruise speed at something like 70% throttle. Turning the wick up is ok for a relatively short time but not for too long.
If you are cruising at xx speed & increase throttle the a/c will climb unless you at the same time decrease elevator.
I may not be utterly perfect but closer to correct than "uneducated rubbish".
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I'm sure that DeeCee is trying to point out that if you increase the throttle setting, then the aircraft (from S&L) will climb, and if you close the throttle it will descend.
If you raise the nose by use of the stick, the speed will decrease........
If you raise the nose by use of the stick, the speed will decrease........
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F900 ex:
I would seriously recommend you read Stick and Rudder, you will then understand better the principles behind powered flight. Basically, the elevator controls your angle of attack and thus determines the speed your aircraft will fly at, the throttle determines rate of climb / descent; Wolfgang's explanation not only makes sense but is generally accepted as correct.
If the throttle was responsible for speed, were I to increase my throttle for a constant Angle of Attack, the net effect should be to increase my speed: same attitude + more throttle = more speed and conversely by reducing throttle at the same Angle of Attack, I would reduce my speed - however this is NOT reality.
So, let's take two different examples with which you will be familiar, in both cases you are descending to land for a power on landing. In example one, you see your touchdown point vanishing towards the nose (you are too high), in example two the touchdown point is moving away from you (you are too low) - what do you do?
If the elevator was your climb / descend control, you would nose up / nose down to bring the plane back to the correct position relative to the touchdown point. Now think back to when you are landing a plane. What do you do? Do you move the nose up or down to make sure you reach your targeted landing spot? No, assuming that your approach is stabilised, the attitude remains constant until you start your flare.
In both cases the rate of descent is NOT controlled by the elevators but by the throttle - close the throttle, the plane sinks faster, increase throttle and the plane either stops sinking or begins to climb. Agree with me so far?
This is most apparent when you consider your speed on final - you're adjusting the throttle but you're not gaining or losing speed - this with a constant Angle of Attack - so WHY isn't the throttle affecting speed? Let's go a step further back: You want to stabilise your spam can for the approach, you have a speed to set up according to the POH. What is the *only* method of adjusting your speed? When you nose up or down, change your Angle of Attack, NOT by changing throttle setting.
This also applies in normal flight:
If we keep a constant Angle of Attack and apply power, the plane will NOT speed up but it will actually begin to climb - try it. Trim your plane for straight and level and increase the power. Your speed will remain relatively constant, however your variometer will show a climb. If you increase the power and want to keep a constant altitude, the nose has to be LOWERED which THEN increases speed - if you DON'T adjust the Angle of Attack, all you do is increase the rate of ascent.
Take your plane back to straight and level flight and, keeping a constant Angle of Attack, reduce the throttle. The plane will NOT slow down, instead it will begin to descend. To arrest the descent and keep a constant altitude, you need to INCREASE the angle of attack which THEN slows the plane. The increase or decrease in speed was NOT a result of changes in the throttle position BUT as a result of a change in Angle of Attack which was caused by:
The elevator.
Had you not adjusted the elevator the speed would have remained constant, hence the elevator should really be viewed as your speed control, the throttle determines whether you will climb or descend.
This is extremely well described in the book Stick and Rudder......
I would seriously recommend you read Stick and Rudder, you will then understand better the principles behind powered flight. Basically, the elevator controls your angle of attack and thus determines the speed your aircraft will fly at, the throttle determines rate of climb / descent; Wolfgang's explanation not only makes sense but is generally accepted as correct.
If the throttle was responsible for speed, were I to increase my throttle for a constant Angle of Attack, the net effect should be to increase my speed: same attitude + more throttle = more speed and conversely by reducing throttle at the same Angle of Attack, I would reduce my speed - however this is NOT reality.
So, let's take two different examples with which you will be familiar, in both cases you are descending to land for a power on landing. In example one, you see your touchdown point vanishing towards the nose (you are too high), in example two the touchdown point is moving away from you (you are too low) - what do you do?
If the elevator was your climb / descend control, you would nose up / nose down to bring the plane back to the correct position relative to the touchdown point. Now think back to when you are landing a plane. What do you do? Do you move the nose up or down to make sure you reach your targeted landing spot? No, assuming that your approach is stabilised, the attitude remains constant until you start your flare.
In both cases the rate of descent is NOT controlled by the elevators but by the throttle - close the throttle, the plane sinks faster, increase throttle and the plane either stops sinking or begins to climb. Agree with me so far?
This is most apparent when you consider your speed on final - you're adjusting the throttle but you're not gaining or losing speed - this with a constant Angle of Attack - so WHY isn't the throttle affecting speed? Let's go a step further back: You want to stabilise your spam can for the approach, you have a speed to set up according to the POH. What is the *only* method of adjusting your speed? When you nose up or down, change your Angle of Attack, NOT by changing throttle setting.
This also applies in normal flight:
If we keep a constant Angle of Attack and apply power, the plane will NOT speed up but it will actually begin to climb - try it. Trim your plane for straight and level and increase the power. Your speed will remain relatively constant, however your variometer will show a climb. If you increase the power and want to keep a constant altitude, the nose has to be LOWERED which THEN increases speed - if you DON'T adjust the Angle of Attack, all you do is increase the rate of ascent.
Take your plane back to straight and level flight and, keeping a constant Angle of Attack, reduce the throttle. The plane will NOT slow down, instead it will begin to descend. To arrest the descent and keep a constant altitude, you need to INCREASE the angle of attack which THEN slows the plane. The increase or decrease in speed was NOT a result of changes in the throttle position BUT as a result of a change in Angle of Attack which was caused by:
The elevator.
Had you not adjusted the elevator the speed would have remained constant, hence the elevator should really be viewed as your speed control, the throttle determines whether you will climb or descend.
This is extremely well described in the book Stick and Rudder......
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I'm reading Stick & Rudder at this very moment to keep me busy during the waiting time for the license and I find this discussion extremely entertaining.
I also find Steve's post a very good summary of some of the main points of the book so I recommend everyone who doesn't "agree" with it chew on that summary for a little while or better yet: get yourself a copy of that book.
Just ignore - or marvel at - the paragraphs where old Wolfgang reveals his opinion about female aviators (the so-called "wives" of pilots).
I also find Steve's post a very good summary of some of the main points of the book so I recommend everyone who doesn't "agree" with it chew on that summary for a little while or better yet: get yourself a copy of that book.
Just ignore - or marvel at - the paragraphs where old Wolfgang reveals his opinion about female aviators (the so-called "wives" of pilots).
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It is more complicated than to simply say "elevator controls speed" etc. as it is combination of throttle and elevator. Depending where you are on the drag curve, one might be more effective than the other at controlling vertical speed. (Yes I have read Stick and rudder, and Fate is the Hunter, and Weather Flying...and.....and...and....) 
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Steve is right.
Try it.
And as to 'ATC asking you to increase speed'
Yep, elevator for speed, but then you'll be low, so throttle for altitude. In practice though, we do both at the same time, then adjust one or the other depending on whether we need to change speed or angle of descent.
And that's where the confusion comes in, normally you change both at the same time, and if you relate it to driving a car, you may think that it's the throttle that's controlling speed. But then if you relate it to a car, you'll slow down to turn left and speed up to turn right.
Try it.
And as to 'ATC asking you to increase speed'
Yep, elevator for speed, but then you'll be low, so throttle for altitude. In practice though, we do both at the same time, then adjust one or the other depending on whether we need to change speed or angle of descent.
And that's where the confusion comes in, normally you change both at the same time, and if you relate it to driving a car, you may think that it's the throttle that's controlling speed. But then if you relate it to a car, you'll slow down to turn left and speed up to turn right.
Last edited by darkroomsource; 27th Jun 2013 at 09:15.
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I do sooooo love these discussions!
To confuse F900 even further consider this: in most light aircraft if you increase the power and do nothing else with the pitch trim, the airspeed will actually decrease...
I wonder if he/she can explain why that is?
To confuse F900 even further consider this: in most light aircraft if you increase the power and do nothing else with the pitch trim, the airspeed will actually decrease...
I wonder if he/she can explain why that is?
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Let say during an approach in either your C150 or 757 you are following a constant profile using a visual touch down reference or Papi's or ILS G/s to achieve the profile.
ATC ask you to increase or decrease speed or maybe you decide to fly the approach at a different speed for whatever reason. You are saying your first reaction would be to use elevator to raise or lower the nose instead of changing the power setting ?
ATC ask you to increase or decrease speed or maybe you decide to fly the approach at a different speed for whatever reason. You are saying your first reaction would be to use elevator to raise or lower the nose instead of changing the power setting ?
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Stevelup
but the point remains - which is that it is your attitude and not the power setting which determines the speed.
Stevelup
but the point remains - which is that it is your attitude and not the power setting which determines the speed.
F900 ex
Debate is always good, so lets take it to extreme.
With an aircraft in a vertical climb accelerating how does attitude control speed assuming sufficient power ?
Raise the nose higher, the speed slows. Lower the nose, the speed increases.
Now assume constant attitude:
Close the throttle, the airplane sinks. Open the throttle, the plane climbs.
The only way a plane can accelerate in a climb is if that the plane has more than enough power - eg, an F16 - to climb vertically AND gain speed even when climbing at 80 - 90 degrees vertical. The superfluous power allows the speed to increase.
However this is not the case with a spam can like we fly - raise the nose, the plane slows. Lower the nose, the plane speeds up, we do not have this abundance of power.
To prove this, take off in your C172 (or whatever you fly) with engine at full power and once the plane is climbing, raise the nose slightly. What happens to your speed? Or lower the nose slightly - what happens to your speed?
It is this misunderstanding that your throttle controls the speed of your aircraft that has led to many a VFR pilot enter IMC and kill themselves, the book describes what happens rather nicely.
Shortened the sequence is:
Enter IMC. His thoughts are: Oh, I can't see the ground, don't want to collide with the ground, down is danger, up is safe so I will climb slightly. Pilot PULLS BACK ON ELEVATOR TO CLIMB - this starts his disaster in motion.
What happens now is that the plane starts to climb but, with constant throttle, starts to slow down. A few seconds later the pilot sees his airspeed is getting dangerously low - remember the instruments lag so if it has shown a decline from 90 to 50 knots, the airspeed is most likely less than 50 knots, possibly close to stalling.
So what does he do? He has learnt that nearing a stall, the only course of action is to lower the nose. He lowers the nose, the plane starts descending but he has no reference to the horizon and can overdo it. Before he realises it, he is descending with an incredible rate of knots, here the ASI has increased from, say, 50 knots to 110 knots, meaning it's now exceeding 110knots. So he now pulls back up, creating a sinus wave of ups and downs of an ever increasing magnitude until either he overstresses the airframe, hits the ground or loses all orientation due to inadvertant looping etc.
What could he have done differently? Apart from a 180 out of IMC? Assuming the plane was trimmed for level flight, if he wanted to ensure his safety, increasing the power by, say, 100rpm would have started a climb WITHOUT speed decay.....
Last edited by Steve6443; 27th Jun 2013 at 11:21.
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Steve6443
Let me grasp your concept with the following.
Let say during an approach in either your C150 or 757 you are following a constant profile using a visual touch down reference or Papi's or ILS G/s to achieve the profile.
ATC ask you to increase or decrease speed or maybe you decide to fly the approach at a different speed for whatever reason. You are saying your first reaction would be to use elevator to raise or lower the nose instead of changing the power setting ?
Let me grasp your concept with the following.
Let say during an approach in either your C150 or 757 you are following a constant profile using a visual touch down reference or Papi's or ILS G/s to achieve the profile.
ATC ask you to increase or decrease speed or maybe you decide to fly the approach at a different speed for whatever reason. You are saying your first reaction would be to use elevator to raise or lower the nose instead of changing the power setting ?
Going back to your example, if ATC asked me to slow down / speed up on an approach - which has happened at EDLW, for example - I will adjust the Angle of Attack for the desired speed AND adjust the throttle at the same time. Why?
Let's assume I was asked to slow my approach to allow a 737 30 seconds more to depart (happened last week, actually). I raise the nose, the plane slows, the angle of attack INCREASES, meaning that, until the stall angle is exceeded, with constant throttle the wings generate more lift. I am now generating more lift than is required for stable flight (or in this case, a 300 foot per minute descent) so what happens? The plane climbs (or descends less slowly). To compensate this, I reduce the throttle to lower the amount of lift the wings are generating, thus slowing my climb.
Both actions happen together but each action is done for a different reason. The elevator to set the lower speed, the throttle to control the lift the airplane generates and thus my rate of descent.
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To prove this, take off in your C172 (or whatever you fly)...
And you haven't answered my question, F900. Any student pilot who has understood Ex4 Effects of Controls (in the UK syllabus) could answer it and will know how to demonstrate it. But I don't think you do.
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I do sooooo love these discussions!
To confuse F900 even further consider this: in most light aircraft if you increase the power and do nothing else with the pitch trim, the airspeed will actually decrease...
I wonder if he/she can explain why that is?
To confuse F900 even further consider this: in most light aircraft if you increase the power and do nothing else with the pitch trim, the airspeed will actually decrease...
I wonder if he/she can explain why that is?
This is what students have to learn when they start practising their approaches - can you all remember back to that first time you came into land and the instructor said "you're a little low, apply some power"? So what did you do? Applied power and the first thing that happened was that the plane nosed up. That upwards motion is what tends to cause the decay in airspeed.
I think part of the problem is, is that we all know how to fly, we do things automatically - apply power on final, compensate for the nose up action without thinking about it.... But we don't possibly understand WHY the plane reacts as it does.
However unless you think about what your controls do, you could put yourself in danger. The chapter in Stick and Rudder about the rudder and tripping over your ailerons is extremely enlightening....
Isn't proon a nice place these days?
Disagree with someone and you are accused of being a sim pilot (the ultimate insult
). Perhaps the accuser might wonder why a sim pilot would start a thread only a couple of days ago asking about changing an a/c from N to G reg? (Easy to do on MS Fsim - I'm forever telling off my air cadets for changing call sign to G-F**K or similar 
)
As to the entrenched positions in the argument, the fact is that speed is a function of both attitude and power, so can be controlled by either throttle or elevator in isolation or both in combination.
Disagree with someone and you are accused of being a sim pilot (the ultimate insult
). Perhaps the accuser might wonder why a sim pilot would start a thread only a couple of days ago asking about changing an a/c from N to G reg? (Easy to do on MS Fsim - I'm forever telling off my air cadets for changing call sign to G-F**K or similar )As to the entrenched positions in the argument, the fact is that speed is a function of both attitude and power, so can be controlled by either throttle or elevator in isolation or both in combination.
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Ultimately it comes down to the first law of thermodynamics: energy is conserved.
If you start in straight and level flight and then increase the throttle setting, the engine puts out more energy every second, so where can that energy go?
IF you pitch up to maintain speed, you will also maintain power lost though drag, so that extra power can only escape as a positive climb rate. Nowhere else to go.
IF you pitch to maintain height, then the only place the energy can be dissipated is through higher drag. A higher speed will achieve this, (unless the wings come off). Theoretically, a much lower speed also works, but fear of the stall makes that less popular.
Practically speaking, if you want to change speed quickly, nothing beats gravity: its force is 5-10 times greater than your typical spam-can engine's maximum thrust.
If you start in straight and level flight and then increase the throttle setting, the engine puts out more energy every second, so where can that energy go?
IF you pitch up to maintain speed, you will also maintain power lost though drag, so that extra power can only escape as a positive climb rate. Nowhere else to go.
IF you pitch to maintain height, then the only place the energy can be dissipated is through higher drag. A higher speed will achieve this, (unless the wings come off). Theoretically, a much lower speed also works, but fear of the stall makes that less popular.
Practically speaking, if you want to change speed quickly, nothing beats gravity: its force is 5-10 times greater than your typical spam-can engine's maximum thrust.
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Mariner 9 said
...the fact is that speed is a function of both attitude and power, so can be controlled by either throttle or elevator in isolation...
...the fact is that speed is a function of both attitude and power, so can be controlled by either throttle or elevator in isolation...
Thinking about point-and-power as a different technique that "proves" that power controls speed is not really helpful. Either way round the adjustment to speed and/or approach angle has to be done by a combination of adjustments to both power and pitch.
Sorry Heston, I maintain that speed can be changed using either control in isolation. You have given an example yourself in a post above how speed can be changed using power alone 
So was that post fundamentally incorrect?
Anyway, this is all academic really, as flying is all about using controls collectively as we all would (presumably) agree.
So was that post fundamentally incorrect?
Anyway, this is all academic really, as flying is all about using controls collectively as we all would (presumably) agree.
Last edited by Mariner9; 28th Jun 2013 at 07:31.
Ok, my take on this.
Primary effects of controls.
Elevators: up and down
Throttle: fast and slow.
However, the two always work in conjunction with each other and cannot be taken in isolation. For a constant throttle setting, pitch controls speed. For example, full throttle climb. For a constant altitude, throttle controls speed.
If we talk about straight and level flight, and increase the speed, we have to increase throttle. But, as we have trimmed for a set speed, we have to move the elevator to maintain straight and level, otherwise the aircraft would start to climb at the speed we had trimmed in level flight.
If we took the power off, the aircraft would decend at the speed we had trimmed in level flight. So, at this point you could argue that power controls pitch. You would be wrong. This is all to do with the AOA of the aircraft, flying fast requires a lower AOA. Flying slow, a higher AOA. This is all to do with weight (mass) and the required lift from the wing.
If we take the approach case. This is all to do with prop wash over the wing. Add power, increase the velocity of air over the wing, and for a constant AOA, you will increase the lift the wing produces, you will decrease your rate of decent. The opposite is true for decreasing power. It's all about prop wash. Don't try this on a jet aircraft, jets don't have this prop wash effect and all you will end up doing is going down the slope faster. In jets elevators control rate of decent, due to a lack of secondary effects.
So, don't take the two systems in isolation. However if we do, throttle can control pitch, just as much as elevators control speed. When we trim an aircraft the trim setting is only good for that speed, and if we adjust the power that aircraft will try to maintain the trimmed speed. Lastly, don't confuse much used secondary effects of controls, as primary effects. However, we all use a combination of both to get the job done.
Maybe I should write a book.
Primary effects of controls.
Elevators: up and down
Throttle: fast and slow.
However, the two always work in conjunction with each other and cannot be taken in isolation. For a constant throttle setting, pitch controls speed. For example, full throttle climb. For a constant altitude, throttle controls speed.
If we talk about straight and level flight, and increase the speed, we have to increase throttle. But, as we have trimmed for a set speed, we have to move the elevator to maintain straight and level, otherwise the aircraft would start to climb at the speed we had trimmed in level flight.
If we took the power off, the aircraft would decend at the speed we had trimmed in level flight. So, at this point you could argue that power controls pitch. You would be wrong. This is all to do with the AOA of the aircraft, flying fast requires a lower AOA. Flying slow, a higher AOA. This is all to do with weight (mass) and the required lift from the wing.
If we take the approach case. This is all to do with prop wash over the wing. Add power, increase the velocity of air over the wing, and for a constant AOA, you will increase the lift the wing produces, you will decrease your rate of decent. The opposite is true for decreasing power. It's all about prop wash. Don't try this on a jet aircraft, jets don't have this prop wash effect and all you will end up doing is going down the slope faster. In jets elevators control rate of decent, due to a lack of secondary effects.
So, don't take the two systems in isolation. However if we do, throttle can control pitch, just as much as elevators control speed. When we trim an aircraft the trim setting is only good for that speed, and if we adjust the power that aircraft will try to maintain the trimmed speed. Lastly, don't confuse much used secondary effects of controls, as primary effects. However, we all use a combination of both to get the job done.
Maybe I should write a book.