Throttle and elevator - which does what?

[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.

[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

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

[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.....