Throttle and elevator - which does what?
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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.
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.
Nice book, by the way, who's the ghost writer ;-)
My (simplified) take is as follows:
Speed is always going to be a function of the angle of attack. Increase the angle of attack, the plane will fly slower, decrease the Angle of Attack, the plane will fly faster.
Now the $64.000 dollar question: What part of the aircraft controls Angle Of Attack?
Answers on the back of European Form EU50 (the brown one) or EU100 (the green one) to me here ;-)
Hi Steve,
You're right to an extent but you have cause and effect the wrong way round. To fly slower we have to decrease power and then raise the AOA to maintain the required amount of lift. If we want to go faster we increase power and lower the AOA to maintain the required amount of lift. If all we were to do was raise AOA to slow down, we would indeed slow down, but we would also start to climb. That's why elevators only control speed in constant power scenarios. Climb or decent. So, we primarily use elevators to go up or down, and power to go faster or slower.
Another way to think about it is energy management. If we want to go faster, or up, we need to increase the amount of energy we have in the system. We do this by adding power. If we want to go slower or lower, we have to remove energy from the system. To do this we have to remove power.
You're right to an extent but you have cause and effect the wrong way round. To fly slower we have to decrease power and then raise the AOA to maintain the required amount of lift. If we want to go faster we increase power and lower the AOA to maintain the required amount of lift. If all we were to do was raise AOA to slow down, we would indeed slow down, but we would also start to climb. That's why elevators only control speed in constant power scenarios. Climb or decent. So, we primarily use elevators to go up or down, and power to go faster or slower.
Another way to think about it is energy management. If we want to go faster, or up, we need to increase the amount of energy we have in the system. We do this by adding power. If we want to go slower or lower, we have to remove energy from the system. To do this we have to remove power.
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Tell you what I'm going to do, this Sunday I'm hoping to go for a flight (assuming the weather allows me). I'll trim the plane to fly straight and level, then increase the engine power by 100rpm and see what happens. I'll then trim for straight and level flight and adjust the trim and see what happens... I'll try to record it with my GoPro and share the results ;-)
Steve, when you go for a flight on Sunday, and you sit on the end of the runway. You will have to increase the speed of the aircraft to get airborne. Ask your self what your going to use to so that. Elevator or throttle? Enjoy the flight!
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Now here's some thoughts from an absolute beginner. :-)
For exactly how long? I can see that there will be an initial tendency to climb this way, but have you ever tried sustaining a climb in this fashion? You might be surprised?
Jonty, you're comparing apples to oranges and you probably know it. I think this discussion is about the effects of controls in flight. I was hoping it was generally accepted among pilots that aircraft on the ground are controlled in a different fashion than when airborne. Do you use ailerons for directional control when taxiing?
If all we were to do was raise AOA to slow down, we would indeed slow down, but we would also start to climb.
You will have to increase the speed of the aircraft to get airborne. Ask your self what your going to use to so that. Elevator or throttle?
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Quote:
Now the $64.000 dollar question: What part of the aircraft controls Angle Of Attack? Elevator
Now the $64.000 dollar question: What part of the aircraft controls Angle Of Attack? Elevator
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Doesn't sound like a good idea to get too religious about one approach or the other.
After a couple of years' flying gliders, it was pretty clear to me that you control speed by attitude, and that by elevator. Then I decided to renew my IR. It took me a couple of goes to work out why I couldn't fly ILSs very accurately, until it was pointed out that the technique there was to fly rate of climb by attitude, and speed with the throttle. (If you're off the glideslope you're going to fix it much faster in the short term with the elevator than power).
Bottom line - we use both. Which you use as the primary depends a bit on what you're doing.
Paul
After a couple of years' flying gliders, it was pretty clear to me that you control speed by attitude, and that by elevator. Then I decided to renew my IR. It took me a couple of goes to work out why I couldn't fly ILSs very accurately, until it was pointed out that the technique there was to fly rate of climb by attitude, and speed with the throttle. (If you're off the glideslope you're going to fix it much faster in the short term with the elevator than power).
Bottom line - we use both. Which you use as the primary depends a bit on what you're doing.
Paul
Spoon PPRuNerist & Mad Inistrator
Throttle and elevator - which does what?
This discussion is spun off from a thread on a completely unrelated topic.
SD
SD
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We all agree that in a powered aircraft, we have a pitch attitude control and a power control. It sounds as though many people posting here are desperately trying to figure out how to use them in isolation - use 'em together! Co-ordinate the control of the aircraft in the pitch axis, as you do in the roll/yaw axis during a turn!
What has little illumination in this discussion is which side of the power curve you're on while you're doing all of this, and, the configuration.
NO, it is not always prop wash only which affects lift with power. Application of power does not always result in a pitch up - I have a power plane which does neither, but it still flies entirely normally, and follows all the "rules" of stability and control on both sides of the power curve. People's minds are fixated on Cessna/Piper, which are examples of these relationships, but not the only examples of how pitch and power affect each other in flight.
Let's extend the thinking farther ahead... Helicopters:
They have a cyclic control, which can be used at any airspeed to lower or raise the nose. They have a collective, which can be used at any speed to increase or decrease lift (let's assume it's a governed engine, so collective equates to power).
If you're hovering, you've increased lift to get there, but not used it all (I hope), and could raise the collective more to climb. But you're not doing that, you're just hovering. You push the cyclic, nose dips and you move forward = speed increases. So far so good? but as you increase speed, you increase drag, and because you have not further raised the collective, you give up some power to that, so you're going to descend a little. But it's okay, you lifted off a skyscraper helipad, so you've got altitude to loose safely. So far, everything we have done is behind the power curve and in helicopter terms, slower than translation speed. Roughly speaking, collective (= power) is primarily controlling lift, and cyclic (= pitch) is primarily controlling speed. Some co ordination of these with the other control is nice, ut it work without.
Then, speed increases, like magic, you pass through translation, the nose pitches up, and you further lower the nose (with the cyclic). So far, you could have done all of this without changing the collective (power), though there would have been some altitude excursions.
Now, through translation, and in cruise flight, still with the same collective power setting, if you want to climb, you will increase pitch with the cyclic, which is now primarily controlling lift (climb), though you'll have to add collective, if you want to maintain the same speed. If you want go faster, you will raise the collective (increase power), and you'll go faster, though you will have to lower the nose a bit to not climb, so collective is controlling speed.
When you approach to land with power, it all reverses, you descend in with low power, on the fast side of the power curve, but as you slow to enter the hover, you're going to have to add a whole bunch of power, and pull the cyclic back to prevent a pitch down. You just translated through to the back side of the power curve. You'll have to add move of both pitch and power to actually slow to a zero speed zero descent hover, but collective is doing lift, and cyclic doing speed again. If you're not sure, pull the cyclic back, and you'll go backward.
So why have I explained flying a helicopter in a primarily fixed wing thread? 'Cause it is surprisingly similar, though the plane will mask the effects pitch/power effects with stability, which the helicopter really does not have much of.
You will find in some flight manuals (some C 150, for sure) contain instructions for landing the aircraft with no pitch control (the cables came off the elevator
). When you read the instructions, and do what it says, it works (but for heaven's sake, do it with a really sharp safety pilot!) You will not use the elevator at all ('cause you broke it), and you will not use the trim or flaps to change pitch in the last phase of the landing, power only, and it works. While you're carefully using power, the speed of the aircraft is not rapidly changing, but pitch and lift are.
However, after all of that....... If I were flying with a pilot who was thinking their way through this while flying the plane, and mechanically selecting one control input then the other to fly, I would be taking them aside for a long talk after landing - 'cause they don't get it yet.
I would expect any self respecting Cessna pilot to be able to extend electric flaps, and change power with one hand, and control the pitch and G with the elevator with the other hand, in such a way that there was the desired pitch change as you slowed, but no G change at all. This would demonstrate appropriate co ordination, and be evidence that that pilot need not worry about which control does what, they can use them appropriately unison, and it does not matter!
What has little illumination in this discussion is which side of the power curve you're on while you're doing all of this, and, the configuration.
NO, it is not always prop wash only which affects lift with power. Application of power does not always result in a pitch up - I have a power plane which does neither, but it still flies entirely normally, and follows all the "rules" of stability and control on both sides of the power curve. People's minds are fixated on Cessna/Piper, which are examples of these relationships, but not the only examples of how pitch and power affect each other in flight.
Let's extend the thinking farther ahead... Helicopters:
They have a cyclic control, which can be used at any airspeed to lower or raise the nose. They have a collective, which can be used at any speed to increase or decrease lift (let's assume it's a governed engine, so collective equates to power).
If you're hovering, you've increased lift to get there, but not used it all (I hope), and could raise the collective more to climb. But you're not doing that, you're just hovering. You push the cyclic, nose dips and you move forward = speed increases. So far so good? but as you increase speed, you increase drag, and because you have not further raised the collective, you give up some power to that, so you're going to descend a little. But it's okay, you lifted off a skyscraper helipad, so you've got altitude to loose safely. So far, everything we have done is behind the power curve and in helicopter terms, slower than translation speed. Roughly speaking, collective (= power) is primarily controlling lift, and cyclic (= pitch) is primarily controlling speed. Some co ordination of these with the other control is nice, ut it work without.
Then, speed increases, like magic, you pass through translation, the nose pitches up, and you further lower the nose (with the cyclic). So far, you could have done all of this without changing the collective (power), though there would have been some altitude excursions.
Now, through translation, and in cruise flight, still with the same collective power setting, if you want to climb, you will increase pitch with the cyclic, which is now primarily controlling lift (climb), though you'll have to add collective, if you want to maintain the same speed. If you want go faster, you will raise the collective (increase power), and you'll go faster, though you will have to lower the nose a bit to not climb, so collective is controlling speed.
When you approach to land with power, it all reverses, you descend in with low power, on the fast side of the power curve, but as you slow to enter the hover, you're going to have to add a whole bunch of power, and pull the cyclic back to prevent a pitch down. You just translated through to the back side of the power curve. You'll have to add move of both pitch and power to actually slow to a zero speed zero descent hover, but collective is doing lift, and cyclic doing speed again. If you're not sure, pull the cyclic back, and you'll go backward.
So why have I explained flying a helicopter in a primarily fixed wing thread? 'Cause it is surprisingly similar, though the plane will mask the effects pitch/power effects with stability, which the helicopter really does not have much of.
You will find in some flight manuals (some C 150, for sure) contain instructions for landing the aircraft with no pitch control (the cables came off the elevator
). When you read the instructions, and do what it says, it works (but for heaven's sake, do it with a really sharp safety pilot!) You will not use the elevator at all ('cause you broke it), and you will not use the trim or flaps to change pitch in the last phase of the landing, power only, and it works. While you're carefully using power, the speed of the aircraft is not rapidly changing, but pitch and lift are.However, after all of that....... If I were flying with a pilot who was thinking their way through this while flying the plane, and mechanically selecting one control input then the other to fly, I would be taking them aside for a long talk after landing - 'cause they don't get it yet.
I would expect any self respecting Cessna pilot to be able to extend electric flaps, and change power with one hand, and control the pitch and G with the elevator with the other hand, in such a way that there was the desired pitch change as you slowed, but no G change at all. This would demonstrate appropriate co ordination, and be evidence that that pilot need not worry about which control does what, they can use them appropriately unison, and it does not matter!
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Steve, Heston
I suggest you stick to spam cams.
If say you are on final, slow, just above stall, and with a height of 50 ft above the threshold.
Tell me you wouldn't lower the nose in isolation as your primary control to gain speed.
Even in a tail dragger?
Tell me you wouldn't .....please.
Think about what Jonty is trying to tell you.
imagine you are going to practice stalling.....do your hasells...and then what?
to slow down and maintain constant height you......close the throttle first, and then adjust the angle of attack. sound familiar?
I suggest you stick to spam cams.
If say you are on final, slow, just above stall, and with a height of 50 ft above the threshold.
Tell me you wouldn't lower the nose in isolation as your primary control to gain speed.
Even in a tail dragger?
Tell me you wouldn't .....please.
Think about what Jonty is trying to tell you.
imagine you are going to practice stalling.....do your hasells...and then what?
to slow down and maintain constant height you......close the throttle first, and then adjust the angle of attack. sound familiar?
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Oh here we go the old Pitch for speed or power for speed argument again!
Both camps talking absolute rubbish!
Think energy management a new phrase!
In a SEP you have two throttles! a conventional one attached to the engine and another attached to the airframe.
Think along those lines and you will not go far wrong!!
There are times especially in a low powered aircraft where full power will not control your speed and you will sit there like an idiot full power watching the speed falling away.
What can you do? Tap into your second throttle by pitching forward reducing AOA and drag and tapping into your second source of energy the airframe.
Fly straight and level! Leave your engine power where it is and note the speed 100 kts? Now tap into the second engine ie the airframe and start using the potential energy by exchanging altitude for energy.
Miracle of miracles the airspeed as you pitch forward increases as you have two big engines available to you and two sources of power.
Both concepts of pitch for speed or power for speed are absolute unadulterated RUBBISH think two throttles two power sources and use them together or apart.
Low powered draggy aircraft and pitch takes superiority as it does with novice learners who need to be kept away from high AOA high drag low powered situations!
Jump Into a Lightning and forget pitch for speed as you will go vertical to 40,000 feet
But above all stop this silly argument and PLEASE SEE THE BIG PICTURE!!!!!!!!!!!!!!!!!!!!!!
Pace
Both camps talking absolute rubbish!
Think energy management a new phrase!
In a SEP you have two throttles! a conventional one attached to the engine and another attached to the airframe.
Think along those lines and you will not go far wrong!!
There are times especially in a low powered aircraft where full power will not control your speed and you will sit there like an idiot full power watching the speed falling away.
What can you do? Tap into your second throttle by pitching forward reducing AOA and drag and tapping into your second source of energy the airframe.
Fly straight and level! Leave your engine power where it is and note the speed 100 kts? Now tap into the second engine ie the airframe and start using the potential energy by exchanging altitude for energy.
Miracle of miracles the airspeed as you pitch forward increases as you have two big engines available to you and two sources of power.
Both concepts of pitch for speed or power for speed are absolute unadulterated RUBBISH think two throttles two power sources and use them together or apart.
Low powered draggy aircraft and pitch takes superiority as it does with novice learners who need to be kept away from high AOA high drag low powered situations!
Jump Into a Lightning and forget pitch for speed as you will go vertical to 40,000 feet
But above all stop this silly argument and PLEASE SEE THE BIG PICTURE!!!!!!!!!!!!!!!!!!!!!!
Pace
Last edited by Pace; 28th Jun 2013 at 20:01.
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Mr Angry 
You could leave full power and pull the nose up far enough where you would achieve almost the same but a power on stall rather than a power off stall
Pace
imagine you are going to practice stalling.....do your hasells...and then what?
to slow down and maintain constant height you......close the throttle first, and then adjust the angle of attack. sound familiar?
to slow down and maintain constant height you......close the throttle first, and then adjust the angle of attack. sound familiar?
Pace
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Steve, Heston
I suggest you stick to spam cams.
I suggest you stick to spam cams.
What happens, with, for example, a PA28, trimmed for straight and level flight, if I:
- increase the engine power by, say, 100rpm
or
- trim the plane to a slightly higher Angle of Attack.
I am taking each of these actions as a separate action and wanted to understand what the ultimate reaction of the plane is after, say, 10 seconds. Is that so hard to understand? I know about co-ordination, I just want to take each item as an singular action and see the reaction of the plane to an individual input.
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F900 think of it this way. You know when you were a kid and your mum put gloves on you that were tied with a bit of string from one arm to the other? So you didn't loose them?
Imagine the bit of string is too short and when you extend your left hand your right hand comes backwards. It's the same with aeroplanes, stick forward with left hand, right hand comes back on the throttle; throttle forward with the right hand, stick back with the left hand. Except you might be wanting to put a bit of right rudder in with the last bit.
Everything works in conjunction with everything else.
Edit: Interesting comments about the 'Push to maintain glideslope'. I find it a lot better, especially if it's something like an NDB approach with set rate of descent for airspeed to use the throttle to control glideslope. The airspeed doesn't change so there's no need to recalculate rate of descent/glideslope and the a/c doen't need retrimming. Just IMO opinion of course, both methods achieve the same thing.
Imagine the bit of string is too short and when you extend your left hand your right hand comes backwards. It's the same with aeroplanes, stick forward with left hand, right hand comes back on the throttle; throttle forward with the right hand, stick back with the left hand. Except you might be wanting to put a bit of right rudder in with the last bit.
Everything works in conjunction with everything else.
Edit: Interesting comments about the 'Push to maintain glideslope'. I find it a lot better, especially if it's something like an NDB approach with set rate of descent for airspeed to use the throttle to control glideslope. The airspeed doesn't change so there's no need to recalculate rate of descent/glideslope and the a/c doen't need retrimming. Just IMO opinion of course, both methods achieve the same thing.
Last edited by thing; 28th Jun 2013 at 20:39.
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This question is generally only pertinent when you're at the limit of power and/or pitch (and then the answer is, I hope, obvious). Otherwise a bit of one requires a bit of the other, usually.
Answer this: You fly down the GS into a suddenly decreasing headwind, or increasing tailwind, how do you recover the loss is airspeed?
Answer this: You fly down the GS into a suddenly decreasing headwind, or increasing tailwind, how do you recover the loss is airspeed?
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Do the glove thing; throttle forward, stick back. I don't mean back as in yank the thing back although I know you knew that... Airspeed remains constant, rate of descent remaons the same. Although lets be honest here in your average spammy if the weather conditions are that bad then you just hang on in there and do the man stuff...
Airspeed remains constant, rate of descent remaons the same. Although lets be honest here in your average spammy if the weather conditions are that bad then you just hang on in there and do the man stuff...