Steep Turns

[FOD]

In a shallow bank turn...you can roll in with rudder and aileron and the airplane will naturally want to roll out

In a medium bank turn...you can roll in with rudder and aileron and trim it up and the airplane will naturally stay in the medium turn

But in a steep turn...you roll in with rudder and aileron and you must keep that rudder pressure in and use a little opposite aileron....Why do you have to keep the rudder pressure in? and why the opposite aileron (imagine its cause the overbanking tendicies)?

[FlyboyZR1]

Draw yourself a picture of a top-down view of an airplane in a 360* turn. The outside wing has a farther distance to travel than the inside wing, and therefore is traveling faster, producing more lift and an overbanking tendency which is why we relax aileron pressure in the turn.

Rudder is used to counteract left-turning tendencies and to keep the airplane coordinated.

[FOD]

then how come we need left rudder in a left turn?

[BayAreaPilot]

Adverse yaw, that outer wing is travaling faster, producing more lift, and with that comes more drag. So with that added drag the nose will want to swing to the right (a slipping turn) A skidding turn would be when you put in too much rudder. That left ruddder then conteracts adverse yaw and get us into a coordinated turn. hope this helps.

[FOD]

Not really
I understand adverse yaw...however like i stated earlier...how come we need to hold that rudder pressure while doing steep turns, but dont need to during medium or shallow turns. go up and try it and you will see....throw in a meduim bank, nuetralize the controls, and trim it up, it will pretty much turn itself...but in a steep bank you have to continue to hold in that rudder pressure.

[RiddlePilot]

[ QUOTE ]
Not really
I understand adverse yaw...however like i stated earlier...how come we need to hold that rudder pressure while doing steep turns, but dont need to during medium or shallow turns. go up and try it and you will see....throw in a meduim bank, nuetralize the controls, and trim it up, it will pretty much turn itself...but in a steep bank you have to continue to hold in that rudder pressure.

[/ QUOTE ]

Well, let's think about what causes the most adverse yaw in a shallow/medium banked turn. As you well know, when you put in aileron deflection, the "down" aileron effectively changes the camber of the airfoil, and causes more lift than the "up" aileron. This causes the need to add rudder for coordination during entry. Once you stabilize in a shallow/medium bank turn, you neutralize the ailerons, which gets rid of a lot of that adverse yaw.

Now, if you increase the angle of bank to the usual 45-60 required for steep turns, you end up with two problems: overbanking tendency, and the need for a good amount of rudder pressure for coordination during the maneuver. As BayAreaPilot said, this is due to the fact that the "up" wing is effectively traveling faster through the air than the "down" wing. When you increase the speed of the relative airflow, you also increase the amount of lift that the wing is producing. Hence, you get that "up" wing trying to bank you over even further. Adverse yaw is created just as BayAreaPilot said too: with increased lift comes increased induced drag.

You can see that the adverse yaw is being created in two separate ways here. One is due to aileron usage during entry (shallow/medium bank), and another is caused by the raised wing moving considerably faster than the lowered wing (steep bank).

Hope this one helps.

[FOD]

all you riddle pilots are the same.....haha...im kidding...im still looking for a little more...but thanks for the help
cheers

[E_Dawg]

[img]/ubbthreads/images/graemlins/confused.gif[/img] you don't need rudder in a steep turn any more than you do in a normal turn

[FOD]

why you hating on the 909?

[RiddlePilot]

[ QUOTE ]
[img]/ubbthreads/images/graemlins/confused.gif[/img] you don't need rudder in a steep turn any more than you do in a normal turn

[/ QUOTE ]

Seems to me like ya do...hmm. Maybe I'm the screwy one,

Anyways, back to the original question: Yes, the opposite aileron is due to the overbanking tendency. And as for the rudder, that's apparently up in the air now. *shrugs*

What else are you looking for?

[RPM]

The 152 I fly doesn't require any rudder during steep turns to stay coordinated, only use it during roll in/out [img]/ubbthreads/images/graemlins/buck.gif[/img]

[RiddlePilot]

I just spent some time in the books trying to figure out the correct answer to this. In the Arrow and Seminole, you'll end up a good bit uncoordinated if you don't apply a solid amount of rudder during the maneuver itself. I haven't done 'em for a long time in a C172, so I don't recall one way or another.

The explanation that the raised wing creates more induced drag makes sense from a theoretical standpoint, but realistically that could be inaccurate. I've been unable to prove it one way or another, though. Anyone have any reliable sources?

[averyrm]

It seems to me that the not needing rudder in a shallow or medium turn could be a characteristic of the aircraft itself, its static stability, or the tendency to remain in a new attitude once there.

Chances are the aircraft needs rudder in the shallow and medium banked turns, but just not as much because the adverse yaw isn't as pronounced.

So why is it more pronounced in the steep turn? Well, remember the planform view - circle description? Well, if you're doing a shallow turn, the speed difference between the two wings is very small, because the diameter of the circle is fairly large. However, when you're doing a very steep turn, the speed difference is much greater as the rate of turn is greater, making the circle smaller. (If you're in an aircraft with a 10 meter wingspan, flying at 50m/s - doing a turn with 100m radius provides a speed difference of 5 m/s at the wingtips and doing a turn of 50m is a difference of 10m/s.)

Hence: greater lift, more drag = stronger overbanking tendency, and more pronounced adverse yaw

Or, steep turns have stronger aerodynamic forces acting on the plane, thats why you have to use more input to counteract them.

Edited to make sense to more people then just me [img]/ubbthreads/images/graemlins/grin.gif[/img]

[Grabo172]

[ QUOTE ]
all you riddle pilots are the same.....haha...im kidding...im still looking for a little more...but thanks for the help
cheers

[/ QUOTE ]

Seems like you don't want to know the answer to the question.
If you aren't going to believe what is said (and correct) then why ask?

So here it is one more time.

In shallow turns and medium turns, you need rudder when deflecting the ailerons due to the adverse yaw created by the greater lift (hence more drag) on the downward deflected aileron. Once established in the turn, with controls neutralized, there isn't enough difference in lift between the wings to cause a NOTICABLE adverse yaw, BUT THERE IS SOME. If you look at your medium bank turn, the ball will be between the lines but NOT centered.

In a Steep Turn, the outside wing is traveling MUCH faster than the inside wing, hence creating NOTICABLE LIFT on the outside wing, therefore you need to hold opposite aileron to maintain bank, then since there is NOTICABLE adverse yaw now, you hold rudder in the direction of the turn.

Can you believe this now?

Cheers! [img]/ubbthreads/images/graemlins/grin.gif[/img]

[FlyboyZR1]

[ QUOTE ]

When you increase the speed of the relative airflow, you also increase the amount of lift that the wing is producing. Hence, you get that "up" wing trying to bank you over even further. Adverse yaw is created just as BayAreaPilot said too: with increased lift comes increased induced drag.

You can see that the adverse yaw is being created in two separate ways here. One is due to aileron usage during entry (shallow/medium bank), and another is caused by the raised wing moving considerably faster than the lowered wing (steep bank).

Hope this one helps.

[/ QUOTE ]

I've never heard of adverse yaw being caused by the outside wing traveling faster during a steep turn. If anything one would think the outside wing is producing more parasite drag because it's traveling faster that the inside wing, not induced drag. Either way it's interesting, I only thought adverse yaw was present when entering a turn, not when already established in a turn.

[E_Dawg]

If you're holding opposite aileron... you'd need rudder toward that side, i.e. away from the turn. Anyway in all the planes I've flown I never seemed to need rudder in the turn to stay coordinated, including the Arrow (never flown a seminole).

[FOD]

Alright im pretty convinced (not 100% positive) that it is due to the tail down force. As bank increases so does the tail down force, due to the increase in AOA or the back pressure that must be added to maintain altitude. This must be compenstated by more rudder or vertical lift.

[Grabo172]

[ QUOTE ]
Alright im pretty convinced (not 100% positive) that it is due to the tail down force. As bank increases so does the tail down force, due to the increase in AOA or the back pressure that must be added to maintain altitude. This must be compenstated by more rudder or vertical lift.

[/ QUOTE ]

huh? [img]/ubbthreads/images/graemlins/banghead.gif[/img]

[RiddlePilot]

[ QUOTE ]
[ QUOTE ]
Alright im pretty convinced (not 100% positive) that it is due to the tail down force. As bank increases so does the tail down force, due to the increase in AOA or the back pressure that must be added to maintain altitude. This must be compenstated by more rudder or vertical lift.

[/ QUOTE ]

huh? [img]/ubbthreads/images/graemlins/banghead.gif[/img]

[/ QUOTE ]

I'm just as confused. FOD, I'm not seeing where you're getting the idea that downforce translates to more rudder needed...

[RiddlePilot]

[ QUOTE ]
I've never heard of adverse yaw being caused by the outside wing traveling faster during a steep turn. If anything one would think the outside wing is producing more parasite drag because it's traveling faster that the inside wing, not induced drag.

[/ QUOTE ]

Due to the increased lift, induced drag will increase on the raised wing like what's been said. Good point though...I'll get into ANA and see if I can't find a more technical answer for ya.

[ QUOTE ]
Anyway in all the planes I've flown I never seemed to need rudder in the turn to stay coordinated, including the Arrow (never flown a seminole).

[/ QUOTE ]

This could also be due to just the nuances of the individual aircraft. Theoretically, you should need bottom rudder throughout the maneuver. Realistically, the airplane may act a bit different.

[MrCole]

I know I'm late to this party, but I wanted to chime in as well. I think Averyrm had the best explanantion, but Grabo and Flyboy had good replies as well. Remember that the velocity of any point of an object in circular motion is, in a simplified form, V = omega x radius, where omega is the rate of turn. So if the center of motion of the turn is the down wing then r is zero and the velocity of the inner wing due to the circular motion is zero. The outer wing on the other hand has a velocity due to the circular motion of omega x r, where r in this case is the wingspan, for small bank angles. Of course this is a simplistic point of view in that the inner wing will still be traveling at some velocity due to its forward motion, and the center of the circle is usually not the tip of the inner wing.

But this will be the case for all turns, not just steep turns. As was pointed out, the rate just happens to be a lot higher for the steep turn, although the radius in the plane of motion is smaller than in a medium or shallow turn. What I mean by this is that the radius r that counts is the projection into the plane of motion. As the angle of bank become steeper, the wingspan that actually lies in the plane of motion becomes smaller until it's zero at knife edge.

But I digress. In medium and shallow bank turns the lateral stability is about equal to or greater than the effect of the increased lift on the outer wing due to circular motion. In steeper turns the overbanking tendency dominates. On the issue of adverse yaw. While the most commonly known is that due to aileron deflection, there is also adverse yaw in any banking as the angle of attack on the wings vary as one goes down and the other goes up . Since the lift vector is perpendicular to the relative wind, the lift vector for one wing usually point a little more forward than the other, leading to adverse yaw.

Although it took me a while to finally get through it, I'm almost done reading "Aerodynamics for Naval Aviators". Having a physics and engineering background made it a lot easier to understand, but I think it's a must read for all pilots who really want to understand the details in an applied manner. Another good read is "Emergency Maneuver Training" by RIch Stowell.

Regards,

Dave

[Grabo172]

Awesome reply!

That's what I wanted to say, but I just didn't have the time to type all that much... I'm a man of few words... [img]/ubbthreads/images/graemlins/cool.gif[/img]

[MrCole]

Grabo,

No problem. Glad I could back you up. [img]/ubbthreads/images/graemlins/grin.gif[/img]

[surreal1221]

Alright, I'm dragging this one out from the depths of late summer 2004.

For a left steep turn.

1) Roll the plane to the left, 45º point
2) Then apply right rudder
3) Power as needed to maintain altitude
4) If you use trim, then trim.

Or

1) Full right rudder
2) Roll left into the turn to 45º
3) Power asneeded
4) Trim as needed

Eh? Which one?

[meritflyer]

I teach -

Roll into your 50 degree turn (commerical standards), add your power beyond 30 degrees where load factors become apparent, trim the aircraft so you dont have to fight with the controls, and monitor. Once we complete the first 360, I teach to lead with the rudder turning into the opposite direction in order to keep the airplane from wanting to gain altitude on the roll out prior to the second 360.

It works out pretty dang good.