Throttle and elevator - which does what?

[Steve6443]

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.....

[DeeCee]

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.

'In a powered aircraft throttle controls speed'


Uneducated rubbish!

[Crash one]

Quote:
DeeCee
Uneducated rubbish!
Please enlighten us all with an educated response using your superior knowledge.

Not difficult, nose down, gravity, speed+. Nose up, gravity, speed -. Shimples.
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".

[airpolice]

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........

[Steve6443]

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......

[Rhino25782]

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).

[stevelup]

That is a secondary effect of controls, for normal flight take the following.

I don't agree... it's the primary effect, not the secondary.

[englishal]

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....) :)

[darkroomsource]

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.

[Heston]

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?

[stevelup]

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 ?

You would have no choice other than to do both in this example, but the point remains - which is that it is your attitude and not the power setting which determines the speed.

[Steve6443]

Quote:
Stevelup
but the point remains - which is that it is your attitude and not the power setting which determines the speed.
Quote:
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 ?

Assume constant (full) power in a climb, ok?

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.....

[Steve6443]

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 ?

Whether flying ILS or PAPI or even visually to a runway without markings, the result is always the same - adjust the throttle to keep on the glide slope / approach.

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.

[Heston]

To prove this, take off in your C172 (or whatever you fly)...

But clearly he doesn't fly anything (sims don't count by the way).

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.

[Steve6443]

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?

I'll do that for him / her.... the application of power tends to raise the nose so even if the trim hasn't been adjusted, the angle of attack has changed slightly. A change in angle of attack upwards means a lower airspeed.

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....

[Mariner9]

Isn't proon a nice place these days?

Disagree with someone and you are accused of being a sim pilot (the ultimate insult :p). 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.

[24Carrot]

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.

[Heston]

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...

That statement is absolutely and fundamentally incorrect. Speed is controlled by a combination of power and elevator. The whole point is that you can't control it by one without the other (in level flight, or without changing the descent or climb profile you are using).

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.

[Mariner9]

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 :ok:

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.

[Jonty]

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.

[Mariner9]

Jonty, the 1st 3 paragraphs of your book were great :ok:

But I suggest you drop the prop wash chapters :E

[Steve6443]

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.


Hi Jonty,

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 ;-)

[Jonty]

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.

[Steve6443]

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 ;-)

[Jonty]

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!

[Rhino25782]

Now here's some thoughts from an absolute beginner. :-)

If all we were to do was raise AOA to slow down, we would indeed slow down, but we would also start to climb.

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?

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?

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?

[dont overfil]

Quote:
Now the $64.000 dollar question: What part of the aircraft controls Angle Of Attack? Elevator


Now If you had said airflow over the elevator I would have agreed.

D.O.

[Mariner9]

What part of an aircraft controls angle of attack?

If its an airbus, a computer.

If its an AF Airbus, nothing. :E

[PaulisHome]

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

[Saab Dastard]

This discussion is spun off from a thread on a completely unrelated topic.

SD

[Cows getting bigger]

I prefer to keep things simple. Power + Attitude = Performance

[Pilot DAR]

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:eek:). 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!

[mrangryofwarlingham]

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?

[Pace]

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 :E

But above all stop this silly argument and PLEASE SEE THE BIG PICTURE!!!!!!!!!!!!!!!!!!!!!!


Pace

[mrangryofwarlingham]

who are you calling camp ?:eek:

[Pace]

Mr Angry :)

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?

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

[Steve6443]

Steve, Heston

I suggest you stick to spam cams.

Thanks, Mr Angry, I have no intention of becoming a glorified bus driver, I earn too much money to want to don a jacket with a few gold rings on them and have long since grown out of requiring the adoration of pubescent females, hence I'll stick to flying my PA28 as a hobby, which is more than adequate for me. However the question still remains:

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.

[thing]

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.

[Lord Spandex Masher]

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? ;)

[thing]

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...

[The500man]

Thrust and gravity work against drag and lift. I would say the elevator is not your speed control because it controls angle of attack. Increasing lift, increases drag, and it is that drag increase that slows you down. If an aircraft designer could work out a way to create lift without drag they would surely do so.

Variation in drag is why the elevator effects speed, but that is not it's primary purpose (which is attitude control). If you want to go faster AND remain straight and level you need an excess of thrust over drag to enable an acceleration (since lift and gravity need to remain balanced). You will get that excess from both increasing thrust and reducing drag, you won't get that soley from your elevator or solely from your engine because a change in one will effect the other. We all know that the four forces I've written about above are not uniquely seperate in the real world.

[Above The Clouds]

Heston
But clearly he doesn't fly anything (sims don't count by the way).


Heston, you cannot imagine how far from the truth you are. :uhoh:

[thing]

But hang it all, we're all here talking about it so whatever works for you works otherwise we would all be smoking holes in the ground by now. Don't sweat the detail.

[flybymike]

Hey! while we are on with pointless discussions, how come my aeroplane doesn't stall every time I turn downwind?

[thing]

Because it likes you. Don't annoy it.

[piperboy84]

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?

Now THAT explains why I'm a **** pilot, my mother never put strings on, she just said "you lose them gloves I'm gonna batter you ya little bastard"

[foxmoth]

I prefer to keep things simple. Power + Attitude =Performance

At last, someone has it correct, why all the other rubbish?!

[Pace]

900

I mean it too:) sorry if it came over as arrogant but this argument has raged for decades and neither camp is right!
The less powerful an engine and more draggy it is the more pitching for speed becomes dominant but it Is still a matter of tapping into two energy sources

Pace

[englishal]

Whether flying ILS or PAPI or even visually to a runway without markings, the result is always the same - adjust the throttle to keep on the glide slope / approach.
This statement is not true. When flying the ILS at 100 kts, if you are above the glidslope you push forwards and if below, you pull back. Throttle then controls your speed...think of a 747 on a coupled approach with autothrottles maintaining a set speed. If the aeroplane is high, George (the AP) will push forward. If that results in higher airspeed then autothrottles will command less thrust.

Conversely, now imagine you are dragging yourself into a short strip under power. You have a high AoA and engine producing a lot of power. If you end up getting low, you increase throttle and bring you back up to the glide path (you don't pull back on the stick or you may stall). If you are high you reduce throttle and sink back onto the glide path.

Pace mentioned Energy Management, and that is what it is. This all depends on where you are on the drag curve which determines which control you should use for speed and height.

[thing]

But doesn't your second para agree with what you quoted? (Englishal)

I always think of stick (or yoke) for speed and throttle for rate of descent on approach. Works for me. Maybe we're all describing the same thing in a different way as altering one thing usually means altering the other anyway.

[mrangryofwarlingham]

Steve

think about your take off roll
to gain speed what do you do? open the throttle sound familiar?
to leave the ground, you.....wait for it.....pull back on stick....

OK, OK. more powerful types will fly themselves off as more speed starts generating sufficient lift.

increase RPM by 100 ? i don't recall. haven't flown an SEP without a wobbly prop for a while now. I think of manifold inches and turbine RPM.

perhaps to help you think about energy management you should think of Vx and Vy. Best rate of climb and best angle of climb.......and then you have cruise climb. all with different power and attitude settings.

[CharlieDeltaUK]

Going back to the laws of physics, it's been said already that this is about how energy is used. Throttle brings more energy into the system, which we can (using the control surfaces) deploy to accelerate or gain height. It converts the chemical energy of fuel into kinetic energy (and/or potential energy if you climb) and mostly you dont notice any immediate consequence of losing the chemical energy. The elevator can convert potential energy into
kinetic energy or vice versa, but then you do notice the loss of the other energy type. Use the elevator to convert kinetic energy into potential energy (climb) and you will notice that the loss of kinetic energy results in deceleration. Using elevator and throttle allows you to do both at the same time.

Ok, so it's been a while since I was at school so maybe someone will re-educate me at this point.

[Pace]

think about your take off roll
to gain speed what do you do? open the throttle sound familiar?
to leave the ground, you.....wait for it.....pull back on stick....

Mt Angry :) for one second I thought you were going to go into the old pitch or power for speed joke there about the student being taught pitch for speed sitting on the end of the runway pumping his elevator up and down to accelerate :ok:

Obviously sitting on the runway there is no potential energy available from the airframe unless there is a cliff at the end of the runway so you only have one source available to you to accelerate to takeoff speed.

That is why its so important especially for students to think of two power sources, two throttles and energy management rather than the pitch or power for speed both in isolation are flawed.

Pace

[Steve6443]

Steve

think about your take off roll
to gain speed what do you do? open the throttle sound familiar?
to leave the ground, you.....wait for it.....pull back on stick....

Mr Angry, just for you, I'll repeat the salient part of a sentence:

in a plane, for example a PA28, TRIMMED FOR STRAIGHT AND LEVEL FLIGHT what happens if I change the setting of throttle or elevator trim - note the bit in italics?

I am NOT talking about take off roll, I am talking about a plane in flight, established straight and level and I make a change to either the elevator or the throttle, what is the outcome to the plane, which, as you hopefully now understand, is a totally different kettle of fish than on a take off roll.

[BEagle]

if you are above the glidslope you push forwards and if below, you pull back.

You neither push nor pull. The control column selects attitudes, the trim controls maintain that attitude and the power lever / throttle selects thrust. Both attitude and thrust are used in order to achieve the desired result.

This thread must be one of the worst I've ever read on PPRuNe. It confirms that the vast majority of civil pilots posting here simply didn't understand their training, or that their training was cheap, nasty and inadequate.

If you wish to understand how to fly, don't listen to some keyboard warrior or computer toy player - go and find a good FI!

[Crash one]

About 60 years ago I built a model of a Javelin. My mate & I decided to see how fast it would go, we rigged a catapult the length of the cricket pitch & launched the thing.
We discovered that in order to keep the a/c in a straight & level attitude at increasing speeds we had to seriously increase the amount of down elevator. If the down elevator was not maintained the thing climbed & lost speed considerably.
We were about 13yrs old & learned a lot from such pissing about. Mainly in this case "You can't have one without the other".
The Javelin eventually broke up in exactly the same fashion as the full sized version did a few weeks later. If the AAIB had asked us we could have told them what would happen:cool:

[Steve6443]

This thread must be one of the worst I've ever read on PPRuNe. It confirms that the vast majority of civil pilots posting here simply didn't understand their training, or that their training was cheap, nasty and inadequate.

Ok BEagle, if your training was so superior, PLEASE could you answer my question as until now, all the answers we have had are people talking about "energy management" without actually answering the question which was:

What happens, with a plane like a PA28, trimmed for straight and level flight if the pilot:

1) Increases the engine rpm by 100rpm

2) after returning the plane to straight and level, trims the plane slightly up?

Yes, this is a theoretical question, however I want to know what happens IF one is moved without adjusting the other, does one have a more marked impact on the aircraft speed compared to rate of climb than the other?

[24Carrot]

In both cases, you should see a phugoid oscillation first. For a spam can that should be a small "roller coaster" in pitch repeating every 20-30 seconds or so.

If you use elevator to hold a fixed pitch, the oscillation will "damp", i.e. die away, very quickly indeed. If you are flying visually you should be doing this without even thinking about it.

If you don't touch the elevator, it still damps, but more slowly. The angle of attack stays pretty constant throughout the oscillation, but speed, pitch and height vary. Energy is swapped between kinetic and potential. (Yes, that E word again...)

After the oscillation?

Assuming you started at cruise speed (i.e. you start on the high speed side of the drag curve, and stay there):

With just extra power, and no other input except anti-yaw pedal, I would predict a gentle climb at a very slightly lower airspeed.
You need very slightly less lift because lift and thrust now share the task of opposing gravity.
You have the same angle of attack so you need slightly less speed.
Extra engine power with slightly lower drag losses means you climb.

With just some back-trim, and no other control input, I would expect a noticably lower airspeed, and a gentle climb.
Again you need very slightly less lift, and you have a higher angle of attack, so a lower speed is enough.
Lower speed means lower drag.
Same engine power with lower drag losses means you climb.

[mrangryofwarlingham]

oooh, Beagle.
Are you going to bite?
"your training"....was very much point and power if I am not mistaken.
and you flew delightful aircraft with a little more poke than a PA28.
but now you train civvies....as a CFI.
I would guess you have a little more experience than Steve.
Heston has wisely left the thread - poor as it is.
but that is the beauty of Pprune - you have the ability to contribute and make it better.

PACE and I were trying to bring a little lightheartedness to the thread.

Now I do recall flying a JP5 a while ago with a F3 instructor, and I stated to him that when the throttle on said JP5 was closed, it would initially pitch up and climb for a few hundred feet. so we went for a flight to prove it....

back to Steve ....
Steve. if you fly these aircraft, you know the answer already. you don't need to be told.

PACE - no potential energy on board the plane unless perhaps there is also an explosive device on board. Wonder what one of those might be to give you a bit of height?

Ah, yes. That black and yellow thing between your legs.....

[BEagle]

oooh, Beagle.
Are you going to bite?

No - it was a stupid question. Steve6443 should refresh EofC2 and S&L2.

"your training"....was very much point and power if I am not mistaken.

I was taught to fly at Bedfordshire Air Centre on the C150 in 1968.

and you flew delightful aircraft with a little more poke than a PA28.

The Chipmunk in which I received my initial RAF training was indeed delightful, but did not have as much 'poke' as a Pa28.

but now you train civvies....as a CFI.

Not any more. But I was taught how to instruct by CFS, the world's best.

I would guess you have a little more experience than Steve.

Probably.

Heston has wisely left the thread - poor as it is.
but that is the beauty of PPRuNe - you have the ability to contribute and make it better

I don't normally bother with 'the blind leading the blind' threads such as this, but because it was such utter rubbish I did so on this occasion.

Now I do recall flying a JP5 a while ago with a F3 instructor, and I stated to him that when the throttle on said JP5 was closed, it would initially pitch up and climb for a few hundred feet. so we went for a flight to prove it....

Again I refer you to EoC 2.....

[BEagle]

I have just got my popcorn ready :E

Do enjoy it! Toffee popcorn in a 1/- or, if you were lucky, a 1/6 bag was always great at the Gaumont many years ago!

[mrangryofwarlingham]

see F900 Ex, i believe you might be what is called a reverse Troll....
someone who possibly knows a lot more than they let on.

Heston = wiser than Steve.
one of them knows when to stop digging....

[Cows getting bigger]

Gents, it appears to me that there is a whole load of egos getting involved here. Undoubtedly there are some enthusiastic individuals who really want to understand how things work and they will be mystified by our willie-waving.

Lets keep this simple. On the vast majority of GA aircraft, a change in attitude or power will require a counter or balancing input from the other control in order to assure a desired effect. Sure, we can add/reduce one element without doing anything with the other but we need to understand the effect of this action (EASA Ex 4) It is true that some aircraft pitch in the opposite direction to the 'norm' when power is changed (Thruster is one example); however, this is actually irrelevant as a decent pilot will always adjust pitch and power to achieve the desired result.

If someone is being taught to utilise controls in isolation and subsequently apply a balancing input, then I suggest they are not being taught correctly.

[Crash one]

I find the willie waving quite entertaining, and informative. Not from a "How to fly" point of view but "Who really knows what they are talking about". :D:D

[Discorde]

In basic terms:

The combination of pitch attitude setting and power setting will determine whether the aircraft flies level or climbs or descends, and also the speed at which it flies. To make the aircraft achieve a desired vertical flight path and speed the pilot must select the appropriate pitch attitude and power setting. Only one combination will give the correct result. The pitch attitude chosen by the pilot is sometimes used to control the vertical flight path of the aircraft and sometimes to control its speed.

When a defined vertical flight path is the intention, pitch attitude controls vertical flight path and power controls speed. Examples: straight and level, approach (including ILS) and landing flare.

When power setting is fixed, pitch attitude controls speed. Examples: climbing and descending.

These methods are valid for all aircraft, from Piper Cub to A380. For analysis in greater depth, look at 'How Do We Fly The Plane'.

[Noah Zark.]

The mantra I was always taught was "Height with throttle, speed with stick."

[flyinkiwi]

The mantra I was always taught was "Height with throttle, speed with stick."

I was told the same thing by my instructor, who then went on to say, "...except when you do this, or this, or this..." :}

He told me during the subsequent debrief that it is a good concept for beginner pilots as it provides them with a good fundamental base on which to build their skills on at the small corner of the flight envelope they'll be living in for a while. But there are exceptions to that rule (hence his demonstration), and once you get into the more advanced training that rule goes out the window.

I hope that explains the rationale behind why students are taught this concept. Personally I thought it made a great deal of sense at the time.

[dash6]

Point and shoot.Gas for speed.If you point it too high,you lose speed even with full power,If you point it too low,You will speed up with no power.Anything in between is ok.Live long and prosper! (And use long runways)Enjoy.

[Crash one]

Point and shoot.Gas for speed.If you point it too high,you lose speed even with full power,If you point it too low,You will speed up with no power.

That reads like a contradiction to me.
Gas for speed but not if you point up or down too far.?

[dash6]

Yes. That's aviation for you. Full of contradictions.Stop trying to analyse it,go fly.

[Crash one]

Sorry I spoke.:mad: I wasn't analysing anything.
In fact I think discussing which control does what in isolation in a machine that operates in all three dimensions at the same time is a total nonsense, because it can only be done as an experiment with no meaningful result. If that is analysing then so be it.:ok:

[phiggsbroadband]

Hi Somebody mentioned that the original question was...

What happens, with a plane like a PA28, trimmed for straight and level flight if the pilot:
1) Increases the engine rpm by 100rpm
2) after returning the plane to straight and level, trims the plane slightly up?

In both cases, if you were at say 2000ft S+L, the plane would try to find a new equilibrium altitude at say 5000ft and then would fly S+L there... Of course it would take a long time, the final levelling off would be at less than 100ft/min.
So you could say that the Trimmer ultimately controls the S+L Altitude.

[Lightning Mate]

As a very experienced ex-RAF QFI, all I can say is












.

[FlyingOfficerKite]

Imagine you're in a glider:

Elevator controls speed.

Put an engine on the front.

Now power controls ROD/ROC.

FOK :)

[Runaway Gun]

But in a glider, what controls your ROD? Speed?

[BackPacker]

Ultimately, side slip or speed brakes. In a glider those are essentially the only methods of reducing total energy. (Actually, the third is aggressive manoevering, as in aerobatics, but that's not exactly suitable while trying to land.)

By increasing your speed you will initially increase ROD as well, but that will be offset if you reduce speed later on - you're only exchanging kinetic for potential energy and vice versa. Furthermore, the descent angle (glide ratio) will not change all that much with speed to have any meaningful effect. Well, at least in the frame of reference of powered flying. Glider pilots fight for every scrap of lift, and there's a whole body of theory around selecting the optimal speed for various circumstances.

[FlyingOfficerKite]

Runaway Gun

But in a glider, what controls your ROC? Speed?

Read the reluctant Post by BEagle.

FOK

[VP-F__]

I have never made a power adjustment to stay on the glidepath whilst flying an ILS approach, always a tweak of elevator does the trick.

As for the original post, the throttle adjusts the noise level and the elevator alters how much land/sky you are looking at. The debate will go on but once you have learnt how to fly and start flying by feel you will do things automatically enough to not really know what does what, you do what needs to be done.

[dash6]

Crash...? VP. Yes if you set a target thrust that covers all eventualities. What if ATC give you a speed to fly?

[FREDSIMTH]

I just don't get it. I sat for 10 minutes on the runway pushing the stick forward and couldn't get the plane to move :)

[Pace]

Oh my Gowd I can hardly believe some of the comments in this thread! Mickey Mouse school of flying comes to mind :ugh:

Just imagine a bike sitting on a pivoted straight construction! Wind the construction forward and the bike will roll forward, wind it back and lo and behold the bake will roll backwards keep it horizontal and you are not going anywhere.
What is controlling speed? Now add an engine to the bike and the bike can move under power when the construction is horizontal it can even climb if you wind a slope uphill into the equation! Wind in too much and the poor little engine will not cope.
Wind the slope forward engine, bike and your weight and you will accelerate like mad.
Conventional peddle bike you are the engine. You peddle like mad uphill you sit there doing nothing downhill.

Aircraft! No rule in isolation is correct! Low powered draggy aircraft with novice pilot and pitch becomes more relevant for speed but pitch is purely the throttle which allows you to tap into the potential energy in the airframe!
Its that energy which gives the speed, The Elevator is just the throttle!

High powered aircraft power can become more relevant but you are regardless managing the energy available to you from the engine and airframe to achieve a desired effect.
So think two throttles two energy sources and both are available to you to use!

The glider on a no lift calm day only has one energy source and that is from the airframe by trading altitude for energy which gives enough speed for the wing to fly. The elevator is the throttle to that energy source! push forward and the speed will increase pull back and it will decrease! pull back too far and that energy will climb the aircraft.

In a typical low powered draggy trainer the biggest danger with novice students is keeping them away from stalling the aircraft. In these aircraft pitching for speed becomes more relevant as with little engine power available there is a danger of the student gettting into a high drag high AOA situation with minimal power which is a lethal combination so teaching them to pitch for speed is vital although only part of the true picture and principal.

For more advanced experienced pilots they will use a combination of both energy sources sometimes more from one source sometimes more from the other sometimes some of both, sometimes none from one all from the other and visa versa hence why I prefer the description of energy management.

Its energy which always gives you speed its the throttle AND elevator which controls that speed as well of course as drag that is available to you

Pace

[Ralis]

Power + Attitude = Performance
With the combination of a power setting and an attitude the A/C will achieve a specific performance, simple as that.

Keep in mind performance is judged by lateral, vertical and linear (airspeed) quantities and not just one individual parameter.

So changing just one variable in the above equation will affect the performance in more than just one parameter, if you want to adjust speed but want to keep ROD/ROC constant both attitude and power must be adjusted to get that performance not just one alone.

What dose this all mean? well both throttle and yoke can change air speed and vertical speed, keeping in mind that when used independently or uncoordinated there will be a secondary, possibly unwanted or opposite effect as described in many of the previous posts.

Whatever action comes first it is the combination that gives us our performance be it what we want or not.

[Crash one]

Crash...? VP. Yes if you set a target thrust that covers all eventualities. What if ATC give you a speed to fly?


Then ATC controls the speed innit.

[Pace]

Then ATC controls the speed innit.

What are the ATC guys in the aircraft poling the machine? :ok:
Many times ATC have given me an instruction I cannot comply with or attempt to comply with but cannot then its a matter of telling them "no can do" !!!
Not much to do with the thread but added it anyway as ATC do not ultimately control the aircraft. You do :E

[Crash one]

Not much to do with the thread but added it anyway as ATC do not ultimately control the aircraft. You do http://images.ibsrv.net/ibsrv/res/src:www.pprune.org/get/images/smilies/evil.gif

Well I never! I didn't know that!!:ok:

[mm_flynn]

It may be useful to consider what the throttle and elevator actually control.

Throttle (to a very close approximation ) controls the rate chemical energy is removed from the fuel tank and added as mechanical energy to the aircraft.

Elevator sets the Cl and Cd, changes in which generally exchange kinetic and potential energy. This also changes the rate of energy dissipation. For many speed ranges this is a rather marginal effect, however well above or below best glide, the effect can be very pronounced (I.e energy dissipation at Vy, Vbg, Vx will all be much much lower than Vso-20%)

The kinetic energy can be exchanged most quickly but is generally most limited in supply.

My instrument instructors tended to teach the lazy mans approach of trim for the air speed you want, use power to adjust your overall ROD (energy dissipation rate in this case), use small elevator input to address short term transients in energy dissipation (I.e. a transient move above GS due to a gust or air column off the parking lot)

[Crash one]

Oh my Gowd I can hardly believe some of the comments in this thread! Mickey Mouse school of flying comes to mind :ugh:



This may well be true.:D It is brilliant, I have learned that if I push on the stick the cows get bigger quicker than they get smaller if I pull. Eventually!!

[Pace]

Crash one is that the case inverted or right way up : ) If its inverted there is always the danger of mistaking sheep for cows ? :{

Pace

[Crash one]

Point taken, but then if you are half inverted then the rudder would control the size of the cows & we are back to square one.:ok:

[Cows getting bigger]

My cows are always getting bigger.

What f there are no cows - are you still descending?

[Crash one]

Depends whether the fields are green or blue

[mrangryofwarlingham]

on a more serious note, if i push forwards on the stick at night, do the street lights below become bigger, or are they the stars? which way up am I?