Learn to Turn

[rstowell]

Loss of control-inflight remains the top cause of fatal accidents in general aviation and occurs most often while maneuvering. Most pilots memorize the "horizontal component of lift" mantra and learn to perform rudimentary turns under mostly ideal conditions. With the added stress of an emergency or when more complex maneuvering is required, however, pilots often botch their turns -- sometimes catastrophically.

The majority of pilots do not realize that the elevator is their primary turn control. In other words, whether or not the flightpath follows a straight line or the arc of a circle depends not on the bank angle, but largely on what the pilot chooses to do with the elevator.

See “Learn to Turn” (07:50) -- http://youtu.be/nWbk3jn0GK4

 

[S Joslin]

Good video.

874 pilots polled and 23% said the rudders turned the airplane!

Good grief!

 

[tehmightypirate]

Great video. Your anecdote about loading the wings and then unloading them was very key to me as this was something I picked up LONG after my private and really should have been stressed more during my training.

 

[thezoolityre]

So I flight instruct at the moment at KBVI, and this hotshot captain came in acting like a "never flown before idiot" parent of a daughter who was going to go through the program. And when I gave the walk around on the airplane he asked me "what primary control surface makes the plane turn?" and I said the elevator. He then proceeded to bombard me with insults like who gave you your instructors certificate and I guess you are too young to have any clue. The dumb-ass thought the rudder turned the plane... and these types of folks are flying you around! Lovely

 

[Henning]

It.s not correct though. The wing makes the plane turn, all the rest of the controls do is situate the wing for the desired component of lift.

 

[ClimbnSink]

It.s not correct though. The wing makes the plane turn, all the rest of the controls do is situate the wing for the desired component of lift.

Yup. My parachutes don't have elevators or rudders they bank up and turn just fine.

 

[tehmightypirate]

The majority of pilots do not realize that the elevator is their primary turn control.http://youtu.be/nWbk3jn0GK4

You guys are missing the point.

 

[G-Man]

Thanks, Rich. I enjoyed this and definitely learned some stuff.

 

[rstowell]

It.s not correct though. The wing makes the plane turn, all the rest of the controls do is situate the wing for the desired component of lift.

What the pilot chooses to do with the elevator largely determines the bulk of the lift being produced by the wing, including: the magnitude of the lift (which can be zero when needed, as during the up line of a Hammerhead or in knife-edge flight; or +2 Gs worth for a level turn at 60 degrees of bank; or +3.5 Gs worth for an inside loop or -3.5 Gs for an outside loop), which side of the wing produces lift (for sustained upright or inverted flight), whether a rolling turn is an inside roller (pull then push on the elevator) or whether it's an outside roller (push then pull on the elevator), and so on.

 

[Henning]

What the pilot chooses to do with the elevator largely determines the bulk of the lift being produced by the wing, including: the magnitude of the lift (which can be zero when needed, as during the up line of a Hammerhead or in knife-edge flight; or +2 Gs worth for a level turn at 60 degrees of bank; or +3.5 Gs worth for an inside loop or -3.5 Gs for an outside loop), which side of the wing produces lift (for sustained upright or inverted flight), whether a rolling turn is an inside roller (pull then push on the elevator) or whether it's an outside roller (push then pull on the elevator), and so on.

Yep, none of that contradicts what I said, the wing turns the plane when situated with a horizontal component of lift, the rest of the controls dictate the wing situation, simple as that. When you bank the wing you add a horizontal component of lift, let's use a normal turn and give the horizontal component .5G and the plane is now turning. Unless we add horsepower or angle of attack, we will start to descend. For normal turns we will typically just add angle of attack and take the minor reduction in speed to maintain 1G Vertical component of lift while adding .5G for to add the horizontal component of lift which is what is turning the plane. We can just as easily leave the elevator alone, split the .5G off of the vertical component and give it to the horizontal component and fill in the energy with gravity and take a loss in altitude.

The elevator does not turn the plane, the elevator prevents loss of altitude while turning the plane and the ailerons and rudder manage the bank angle and coordination of the wing, but when all is said and done, the wing turns the plane.

 

[rstowell]

The elevator does not turn the plane, the elevator prevents loss of altitude while turning the plane and the ailerons and rudder manage the bank angle and coordination of the wing, but when all is said and done, the wing turns the plane.

The wing does not turn the airplane. Forces act to move the airplane (or not), and we use the various controls to manipulate those forces for desired effects. Rudder controls the angle of attack of the fuselage; the ailerons control local angles of attack near the wingtips; the elevator controls the overall angle of attack of the wing. We employ these controls to manipulate various forces to accomplish desired outcomes (though accident reports are replete with case after case where the pilot wanted "A" result, but applied inputs for "B" result and got "B").

Need to start thinking about the airplane as an all-attitude vehicle capable of three-dimonsional movements, and "turns" as any curving of the flightpath. There are only two possible flightpaths: straight lines and curves, dictated by choice of elevator position (energy state notwithstanding).

Depending on energy state and equipment, at least seven types of "turns" are possible starting at, say, 30 degrees of bank, also depending on what's important to me at the moment:

Coordinated level, climbing, and descending turns; slipping or skidding turns; inside looping or outside looping (climbing turns where bank angle is allowed to vary naturally).

When banked, I can make the horizontal component of lift disappear if I so choose with proper placement of the elevator. It won't end up being a turn in that case.

Also, can you explain how I was able to do a segmented turn, a 4-pt roll, and a segmented loop if elevator action does not determine whether the airplane follows a straight path or a curved one?

 

[Everskyward]

I think I am having deja vu.

So I will ask, if the airplane is straight and level how does the elevator turn the airplane? It only controls the turn once the airplane is positioned in a bank using some other means.

I think this is where the conflict is and why you get so many people saying "ailerons".

 

[rstowell]

I think I am having deja vu.

So I will ask, if the airplane is straight and level how does the elevator turn the airplane? It only controls the turn once the airplane is positioned in a bank using some other means.

I think this is where the conflict is and why you get so many people saying "ailerons".

If I'm straight an level, I am there because I have set the elevator to make it so. I can also be straight and level at 140 mph in my Decathlon and decide to perform a vertical turn (i.e., loop) first by pulling about +3.5 G on the elevator to bend the flightpath upward (the climbing part of the turn), then continuing to pull the elevator to bend the flight path back around to level flight (the descending part of the turn). Upon reaching level flight again, I release the aft elevator and re-establish level flight (a straight line).

Elevator dictates flightpath, and flightpath is either a line or a curve. From the three-dimensional view of flying, the airplane does not need to be banked first in order to turn/follow a curve. Did you watch the video yet?

 

[Everskyward]

If I'm straight an level, I am there because I have set the elevator to make it so. I can also be straight and level at 140 mph in my Decathlon and decide to perform a vertical turn (i.e., loop) first by pulling about +3.5 G on the elevator to bend the flightpath upward (the climbing part of the turn), then continuing to pull the elevator to bend the flight path back around to level flight (the descending part of the turn). Upon reaching level flight again, I release the aft elevator and re-establish level flight (a straight line).

Elevator dictates flightpath, and flightpath is either a line or a curve. From the three-dimensional view of flying, the airplane does not need to be banked first in order to turn/follow a curve. Did you watch the video yet?

Yes, I watched the video and I understand the principle once the airplane is banked. OK, so you are calling a loop a vertical turn. That may be true as far as physics is concerned but that's stretching the definition for the average pilot. Would you also call entering a climb straight ahead a "turn"?

 

[bqmassey]

The horizontal component of lift turns the airplane. That comes from the wing, not the elevator. This is private pilot level aerodynamics.

 

[rstowell]

Yes, I watched the video and I understand the principle once the airplane is banked. OK, so you are calling a loop a vertical turn. That may be true as far as physics is concerned but that's stretching the definition for the average pilot. Would you also call entering a climb straight ahead a "turn"?

Insofar as the transition from the "straight and level line" to the "climbing line" requires bending the flightpath in much the same way as is done during a classic level turn, yes.

The flare to landing (when pilots actually flare :wink2 then, is the last piece of a loop/vertical turn, albeit with a lot less G required compared to an aerobatic-syle loop!

The problem in aviation, especially for students, is that teaching is compartmentalized as if nothing is connected. In reality, everything is connected in the three-dimensional world we inhabit as pilots. For example, if all I said is that I am pulling 2 Gs, I could be doing one of several things: a level, coordinated turn at 60 degrees of bank, a pitch up from level flight before starting an aileron roll, pulling out of a spiral after leveling the wings, and so on. While the attitudes may be different, and the mechanism that put me in those positions may be different, the pull on the elevator and the result are identical: the flightpath bends by imposing a 2-G load via the elevator.

If our teaching was broader, we wouldn't have pilots asking questions like, "how can an airplane fly upside" when it is no different from upright flight. All that's needed is wind and an angle of attack. Doesn't matter which side of the wing that might be happening on. Also, broader understanding makes it easier to transition to new maneuvers and concepts because the foundation is there vs. a "this is totally different from that" approach.

 

[rstowell]

The horizontal component of lift turns the airplane. That comes from the wing, not the elevator. This is private pilot level aerodynamics.

And what controls the magnitude of that lift? The elevator, hence the ability to either grow or shrink that horizontal component (and simultaneously, the vertical component) once a bank has been established. It's how air show pilots are able to perform 4-pt rolls and knife-edge passes without veering off heading. It's also how aerobatic pilots are able to set and maintain a vertical line for a Hammerhead without being pulled off off of it by the wing's lift. Watch the video, especially the segmented turns.

 

[FastEddieB]

From the FAA Airplane Flying Handbook:



All four primary controls are used in close coordination when making turns. Their functions are as follows.

• The ailerons bank the wings and so determine the rate of turn at any given airspeed.

• The elevator moves the nose of the airplane up or down in relation to the pilot, and perpendicular to the wings. Doing that, it both sets the pitch attitude in the turn and “pulls” the nose of the airplane around the turn.

• The throttle provides thrust which may be used for airspeed to tighten the turn.

• The rudder offsets any yaw effects developed by the other controls. The rudder does not turn the airplane.

 

[RoscoeT]

So I flight instruct at the moment at KBVI, and this hotshot captain came in acting like a "never flown before idiot" parent of a daughter who was going to go through the program. And when I gave the walk around on the airplane he asked me "what primary control surface makes the plane turn?" and I said the elevator. He then proceeded to bombard me with insults like who gave you your instructors certificate and I guess you are too young to have any clue. The dumb-ass thought the rudder turned the plane... and these types of folks are flying you around! Lovely

I think your story is BS...airline pilots don't use the rudder so therefore, how could he have ever turned an airplane.

 

[Everskyward]

Insofar as the transition from the "straight and level line" to the "climbing line" requires bending the flightpath in much the same way as is done during a classic level turn, yes.

I see where you are coming from in that you are calling any bend in the flightpath a "turn" even if it is straight ahead. But I can also see where this would confuse people who think of turns in the normal sense. So maybe when you ask "how does an airplane turn?" you need to define what "turn" means. Or is this something you are trying to get people to discover on their own?

 

[rstowell]

I see where you are coming from in that you are calling any bend in the flightpath a "turn" even if it is straight ahead. But I can also see where this would confuse people who think of turns in the normal sense. So maybe when you ask "how does an airplane turn?" you need to define what "turn" means. Or is this something you are trying to get people to discover on their own?

Discover, debate, but more importantly, become better observers of what we and our airplanes are doing at all times. As our awareness grows, so too does the appreciation for the magic we experience as pilots.

 

[ClimbnSink]

Let's tell students pitch turns airplanes.

 

[bqmassey]

And what controls the magnitude of that lift?

Airspeed, wing shape, surface area, air density, and—what I'm sure you're alluding to—AoA (adjusted with elevator).

The elevator, hence the ability to either grow or shrink that horizontal component (and simultaneously, the vertical component) once a bank has been established.

I think we all understand that elevator can encourages the wing to produce more (or less) lift. That's not an aviation mystery. But that lift, regardless of it's magnitude, is not going to turn the airplane if it's strictly vertical.

Even if you've got that wing producing a ton of lift, (high airspeed, maximum CL), it will turn at a very slow rate if you only bank it one degree. Why? Because, as most of us understand, the shallow bank is only diverting a small portion of that lift into the horizontal.

There's a lot of things that are required to facilitate the turn, but it's the horizontal component of lift, generated by the wing, that turns the airplane.

 

[Jaybird180]

Rich,
I enjoyed the video and also the debate here is better than morning coffee.

I noticed that during the Dutch roll tun, there was a change in the rate of turn commensurate with the reduction in bank angle, very slight but most detectable at the bottom of the roll (hesitation point).

I was thinking the same that Fast Eddie posted in #18, that there is an interaction between all of the forces that prevent LOC-I that you alluded to in #16

 

[rstowell]

Airspeed, wing shape, surface area, air density, and—what I'm sure you're alluding to—AoA (adjusted with elevator).

There's a lot of things that are required to facilitate the turn, but it's the horizontal component of lift, generated by the wing, that turns the airplane.

What if the pilot chooses not to turn? How is the air show pilot able to perform a knife-edge pass while remaining on heading, since in knife-edge, every bit of that lift from the wing would then be a horizontal component? (Hint: it has nothing to do with the rudder)

Divorcing the elevator from the lift generated by the wing means the above question cannot be answered properly. On the other hand, recognizing that elevator and lift are indelibly linked, and that it is the pilot's selection of elevator position that controls AoA/lift, makes for a consistent and straightforward explanation.

The explanation of knife-edge flight and a whole host of other possibilities is simple with elevator: in knife-edge flight, the pilot, using the elevator, must drive AoA to the zero lift angle in order to eliminate the lift from the wing. This is the only way to stay on heading in knife-edge flight.

What is true in the knife-edge example in terms of using the elevator to manage lift is true elsewhere. For example: Assume a coordinated, level, upright turn at 60 degrees of bank with sufficient energy/margin to critical AoA.

Q: What is required to sustain such a turn?
A: +2 G

Q: Where does the +2 G come from?
A: Pulling on the elevator ("2 Gs worth" of pull)

Q: What is happening regarding the lift on the wing as a result of the +2 G pull?
A: Due to the +2 G pull on the elevator, total lift doubles; the vertical component, Lv, grows just enough to equal W; the horizontal component, Lh grows as well, accelerating the turn.

Q: What happens if the pilot only pulls +1.5 G?

Q: What happens if the pilot pulls +3 G?

Q: Can you map it on a V-G diagram (or V-n, if you prefer "n" vs. "G")?

Q: What other maneuvers can be mapped on a V-G diagram?

Q: The V-G diagram is a plot of speed (V), G-load (G or n), structural design limits (bending or breaking the airplane), and aerodynamic limits (critical AoA). So, what does the diagram really represent?
A: The V-G diagram a graphic representation of everything the elevator does. You can plot turns, loops, hammerheads, and even accelerated stall scenarios -- all driven by the elevator.

 

[rstowell]

Rich,
I enjoyed the video and also the debate here is better than morning coffee.

I noticed that during the Dutch roll tun, there was a change in the rate of turn commensurate with the reduction in bank angle, very slight but most detectable at the bottom of the roll (hesitation point).

Indeed, the rate of turn did vary as the bank angle varied, mostly because I was also varying the amount of elevator pressure to keep the nose tracking the horizon line -- less G as bank decreased, slightly more G as bank increased.

 

[Velocity173]

The video said primary CONTROL SURFACE when turning an airplane, not what turns an airplane. The elevator is primary in varying the rate of turn but the wing's horizontal component is what actually is turning the aircraft. The ailerons are just banking the aircraft, once the nose starts to transverse across the horizon, then you have a turn established. Increase elevator and you increase AOA, thereby increasing both the vertical and horizontal components.

Also I wouldn't say this demonstration is universal to all airplanes. Some airplanes you can stomp on rudder and get very little if any bank. While others, depending on size of rudder, wing dihedral, fuse shape etc, you can get a decent bank. A canard with tip sails can bank quite rapidly with just the application of rudder.

 

[rstowell]

To get back to the central thesis:

The elevator pulls the nose of the airplane around the turn.​

It's that simple.

 

[ClimbnSink]

Hmmm I thought the elevator changes the angle of attack on the wings and the wings pull the airplane round the turn. I get the point, people suck at flying.

 

[rstowell]

Hmmm I thought the elevator changes the angle of attack on the wings and the wings pull the airplane round the turn. I get the point, people suck at flying.

You're on the right track, Greg -- you have linked the elevator to the wing, input with output!

Some of the other posts leave the impression that once a bank has been established, the wing takes care of the rest and the pilot is relegated to that of observer. There is no connection between movement of the elevator and response of the wing. If that were really true, then the shape, quality, and type of turn that results at a given bank would be random -- maybe level, maybe descending, maybe climbing, maybe even a chandelle, ultimately whatever the wing is in the mood to deliver at the time. Talk about making check rides that much harder

Regarding arcing flightpaths and within aerodynamic, structural, and energy considerations, the pilot dictates what he/she wants the wing to deliver via the elevator. The pilot is not passive, but actively controls the outcome by managing what the wing does. Via elevator, the pilot commands more or less lift from the wing, and even which side of the wing produces that lift, to reach the desired outcome.

Rolling turns are a perfect example of dictating the terms to the wing. Let's say we're tooling along in the airplane. We pick a landmark on the horizon off our left wingtip. We decide to make a 90 degree heading change to the landmark. For fun, we decide to do a full roll to the left along the way. To accomplish the task (shown in the video), we roll slowly to the left and tug on the elevator to pull the nose to the left along the horizon. Near the inverted part of our full roll, we have to switch which side of the wing makes lift to continue to move over to the landmark -- we have to now push on the elevator an perform an inverted turn.

To make it even more fun, we could do the same 90 degree heading change, but instead of initially rolling left TOWARD the landmark, we roll to the right AWAY from it. So how do we make the nose go where we want it to go now? We push on the elevator, commanding the wing to produce lift on its other side to turn us in the desired direction. Half way through we have to switch to pulling to complete the desired heading change. This is not an aberration, but perfectly consistent with the "elevator pulls (sometimes pushes) the nose around in a turn" discussion. Rolling turns are the ultimate expression of the concept.

Elevator controls AoA, and AoA gets us to the lift we seek from the main wing. Absent (or even with) direct AoA measurement, we know that AoA is on the move, i.e., that the pilot is doing something with the elevator, whenever at least two of these three parameters are changing at the same time: speed, G-load, flightpath.

The other issue we have in aviation is the language we use to describe events. For example, saying "the airplane turned" or "the plane stalled" or "the plane spun" not only is passive, but implies something like the relationship between horse and rider where the rider has control of the horse up to the point where the horse decides it has other ideas. But flying isn't like that -- the airplane does exactly what it's told, when it's told, and however much it's told. If we want "A" but communicate "B" to the airplane with our inputs, we'll get "B."

It is more accurate to say "the PILOT turned/stalled/spun the airplane."

 

[rstowell]

I get the point, people suck at flying.

I forgot to add that pilots don't have to suck at flying (the sucking usually doesn't start until something novel or scary happens).

If instructors did a better job of raising the stick and rudder skills of their students above the rote level, particularly as those skills relate to unusual situations, there'd be less sucking and a whole lot more fun and confidence on the controls.

 

[Everskyward]

How are you going to explain this situation? You roll into a bank but keep the elevator neutral. You still will be turning although you will also be descending.

 

[Jaybird180]

How are you going to explain this situation? You roll into a bank but keep the elevator neutral. You still will be turning although you will also be descending.

Dihedral can account for that also....


Wait for it.....





Lift displaced horizontally about the roll axis

 

[Everskyward]

Dihedral can account for that also....


Wait for it.....





Lift displaced horizontally about the roll axis

I want to hear the answer which involves the elevator.

 

[rstowell]

I want to hear the answer which involves the elevator.

Watch the video. The default turn will be whatever the elevator trim has been set for.

Next time you're out flying, why don't you experiment with turns to see what's doing what?

 

[rstowell]

Watch the video. The default turn will be whatever the elevator trim has been set for.

Next time you're out flying, why don't you experiment with turns to see what's doing what?

How does the "elevator neutral" turn violate the concept? For a given bank angle, there are a near infinite number of elevator positions and resulting turns/arcs between almost full aft and almost full forward elevator.

 

[eetrojan]

How are you going to explain this situation? You roll into a bank but keep the elevator neutral. You still will be turning although you will also be descending.

I suspect that it boils down to choosing to do nothing with the elevator is still choosing.

 

[Everskyward]

I suspect that it boils down to choosing to do nothing with the elevator is still choosing.

I get that, but it seems like unnecessarily confusing the issue. If the purpose is to make people think, it does do that, however.

 

[FastEddieB]

I suspect that it boils down to choosing to do nothing with the elevator is still choosing.

I hear that in some celestial voice!

 

[Henning]

Watch the video. The default turn will be whatever the elevator trim has been set for.

Next time you're out flying, why don't you experiment with turns to see what's doing what?

All the elevator does is regulate the angle of attack of the wing. Lift turns the plane same as lift supports the plane against gravity. The elevator impacts the angle of attack of the wing which when combined with power create lift. Lift in the direction of the sum of the components of lift is directed by the wing. The elevator is just a lever on a stick used to control the angle of attack of the wing. Power is what "pulls the nose around" and the elevator is one of two components which regulate where the nose points.

The elevator is one of the components that we use to control the plane in a turn, but in the end, the turn is accomplished through lift, and that lift is provided by the wing. We really don't even need an elevator or rudder to turn as is exemplified by a foil type parachute, all we need is some way to to modify the vector component of lift, 'wing warping' being the simplest.

To pin the turning function on the elevator is no more correct than to pin it on the ailerons or rudder. I can use any of these control surfaces independently to make the plane turn (when we allow for your loop being a vertical turn) because each of these controls independently can alter the sum vector of lift.

Lift turns the airplane, the wing creates the lift, the control surfaces only direct the sum vector of lift.