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Blackbird
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Silly Question Regarding Rudder Deflections

Sun Aug 24, 2008 9:41 pm

I know this sounds remarkably silly... why does the rudder when deflected (being above the planes center of gravity) not roll the plane the opposite way it's deflected? In other words, right rudder, left roll?

Is it just because the yawing motion (say right-yaw) produced also produces a rolling movement (say right-roll, due to asymmetrical airflow over the wings) to go with it, that neutralizes this tendency?

Or is there another reason the rudder doesn't roll the plane the opposite way it yaws it because the fin is above the center of gravity?


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SlamClick
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RE: Silly Question Regarding Rudder Deflections

Sun Aug 24, 2008 9:53 pm

It does.

It is possible to rudder-roll many airplanes.

If you are thinking airliners, you should know that the rudder pedals are nothing more than footrests, and not even our favorite footrest any time all the engines are running. We roll in and out of turns with our feet flat on the floor or resting against the pedals and let the yaw damper operate the rudder. I flew a DC-3 a while back and humiliated myself (I am typed in it) because I'd utterly forgotten what those pedals were for.

The [airliner] rudder has a large area because we may have to lift off with one engine inoperative and the other at takeoff thrust. By the time we have the flaps/slats cleaned up the rudder travel (throw) is restricted. By the time we get to cruise the thing hardly moves at all. So it has its center of pressure maybe twenty feet above the CG. The wings have theirs maybe forty or fifty feet outboard from CG and have a lot more area than the rudder. Then we have ailerons out at the very tips, maybe 70 to 100 feet from CG - lots of arm! And we have roll spoilers. The rudder just doesn't have much opportunity to roll the airplane once we are underway.

Now I suspect that, say, a T-38 would be rather different.

One more thing to think about regarding rudder. Let's make it a Cessna 150. To make a turn you will apply aileron and rudder into the turn - your early lessons being focused on teaching you how to keep the ball centered. When the bank is steep enough you will center the ailerons to stop the roll-rate and use the rudder to center the ball, which means you will end up centering the rudder. You will continue the turn with backpressure on the elevators alone. In a sustained, coordinated turn the elevator will be the only surface with any noticeable throw. We turn with elevator.
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Starlionblue
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RE: Silly Question Regarding Rudder Deflections

Sun Aug 24, 2008 10:52 pm

SlamClick explains it well (how else?) I would add that rudder roll is an interesting design consideration for trijets. Once of the disadvantages of the DC-10/MD-11 style rudder is that it is quite far from centerline compared to the L-1011's rudder. So you get more more roll when it deflects than if it were closer. I believe this is why the DC-10 wing engines had to be closer to the fuse than the L-1011 wing engines, leading to a stronger (=heavier) wing.
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474218
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RE: Silly Question Regarding Rudder Deflections

Sun Aug 24, 2008 11:39 pm



Quoting Starlionblue (Reply 2):
I believe this is why the DC-10 wing engines had to be closer to the fuse than the L-1011 wing engines, leading to a stronger (=heavier) wing.

The L-1011 has a large single rudder, while the DC-10/MD-11 has a much smaller duel segment, double articulated rudder. Because the L-1011's larger rudder provides more rudder authority, the wing engines could be mounted further away from the fuselage centerline.
 
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Starlionblue
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RE: Silly Question Regarding Rudder Deflections

Sun Aug 24, 2008 11:57 pm



Quoting 474218 (Reply 3):

The L-1011 has a large single rudder, while the DC-10/MD-11 has a much smaller duel segment, double articulated rudder. Because the L-1011's larger rudder provides more rudder authority, the wing engines could be mounted further away from the fuselage centerline.

Ah. Quite.

The DC-10/MD-11 is also smaller due to less usable fin height. I guess it's all part of the same puzzle.  Wink
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BE77
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RE: Silly Question Regarding Rudder Deflections

Mon Aug 25, 2008 12:16 am

OK Blackbird - I never thought about it like that before, so now I am confused too.

You would think you would get a rolling moment about the CG when you deflect the rudder - actually, you must. Something else bigger is happening though, since it doesn't work that way?
I tend to actually use those 'footrests' all the time, as a BE77 does not have aileron trim. If I need both hands for things like map reading (I'm old school - my gps does not have a moving map  Smile ) then I just use the rudder to pick up a wing when it drops. (Note - yes, the BE77 ailerons are spring connected to the rudder, but the same thing works in a buck and a half too).

Back to the conjecture...maybe the diehedral of the wing push forward by the induced yaw acts to generate a lot more lift, therefor overcoming any roll moment about the cg??
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futureualpilot
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RE: Silly Question Regarding Rudder Deflections

Mon Aug 25, 2008 12:16 am

I'm guessing its because it makes the outside wing travel faster, generating more lift and creating a tendency to roll towards the same side as the depressed rudder pedal. (Thinking as though one were to apply rudder in level flight)
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BE77
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RE: Silly Question Regarding Rudder Deflections

Mon Aug 25, 2008 12:19 am



Quoting Blackbird (Thread starter):
I know this sounds remarkably silly...

No silly questions are possible, only silly answers!  crazy   silly 
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SlamClick
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RE: Silly Question Regarding Rudder Deflections

Mon Aug 25, 2008 12:19 am



Quoting BE77 (Reply 5):

I guess there was something wrong with my explanaton.

Oh. by the way:

Quoting BE77 (Reply 5):
just use the rudder to pick up a wing when it drops

Get rid of that habit before you ever fly swept-wing aircraft.
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Moose135
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RE: Silly Question Regarding Rudder Deflections

Mon Aug 25, 2008 12:25 am



Quoting SlamClick (Reply 1):
Now I suspect that, say, a T-38 would be rather different.

Yes, but I don't remember using the rudder for turns in a T-38, mostly just roll and pull. The T-37 you used rudder in turns, and when I went to the KC-135, I needed to re-learn using rudder around the pattern.
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BE77
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RE: Silly Question Regarding Rudder Deflections

Mon Aug 25, 2008 1:07 am



Quoting SlamClick (Reply 8):
Get rid of that habit before you ever fly swept-wing aircraft

Sure hope I have to!!! Not likely without a lot of help from the lottery though.  Sad

Quoting SlamClick (Reply 8):
guess there was something wrong with my explanaton.

Nah, nothing wrong, with your explanation. I was just trying to sort out the dynamics wrt the Newtownian physics of the issue in my own head. Like Blackbird posted, I know that a rudder acts differently than an aileron, but it is the why that is interesting - and I at least never thought about it before - for the last 29 years, I 'knew' the rudder behaved as it did, without ever thinking about the counter-intuitivensss that Blackbird highlighted.
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Starlionblue
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RE: Silly Question Regarding Rudder Deflections

Mon Aug 25, 2008 1:56 am

On the opposite end, you have fighter aircraft that use their elevators (and I believe even rudder(s)) as extra ailerons. They have elevons and I guess the rudder(s) are "rudderons".  Wink
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Jetlagged
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RE: Silly Question Regarding Rudder Deflections

Mon Aug 25, 2008 2:33 am



Quoting BE77 (Reply 10):
Nah, nothing wrong, with your explanation. I was just trying to sort out the dynamics wrt the Newtownian physics of the issue in my own head. Like Blackbird posted, I know that a rudder acts differently than an aileron, but it is the why that is interesting - and I at least never thought about it before - for the last 29 years, I 'knew' the rudder behaved as it did, without ever thinking about the counter-intuitivensss that Blackbird highlighted.

Hardly counter-intiutive. All pilots are taught "effects of controls", and that includes roll induced by rudder. Only a non pilot or someone who has not studied aerodynamic stability and control would find it surprising.

Ailerons induce yaw as well as roll (which is part of the reason why you need a rudder!). Lateral and directional control and stability are closely interlinked. It is not like a ships rudder, as the only means of making a turn. You could make a rudder turn in an aircraft but it would not be very efficient. Better to use the tilted lift vector instead.

Actually a rudder works just like an aileron. It changes the local aerofoil camber and thus changes the lift the surface produces. The only difference is the axis the surface acts in.
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474218
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RE: Silly Question Regarding Rudder Deflections

Mon Aug 25, 2008 3:30 am



Quoting Jetlagged (Reply 12):
Actually a rudder works just like an aileron. It changes the local aerofoil camber and thus changes the lift the surface produces. The only difference is the axis the surface acts in.

Jetlagged:

Congratulations, you are the first person (beside myself) that understands that the rudder doesn't push the nose of the aircraft. But that the the tail end is sucked in the the low pressure created by deflecting the rudder.
 
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Starlionblue
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RE: Silly Question Regarding Rudder Deflections

Mon Aug 25, 2008 4:15 am



Quoting 474218 (Reply 13):
But that the the tail end is sucked in the the low pressure created by deflecting the rudder.

Isn't it pushed by the high pressure?  duck 
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SlamClick
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RE: Silly Question Regarding Rudder Deflections

Mon Aug 25, 2008 5:40 am



Quoting Starlionblue (Reply 14):
Isn't it pushed by the high pressure?

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vikkyvik
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RE: Silly Question Regarding Rudder Deflections

Mon Aug 25, 2008 6:39 am



Quoting Starlionblue (Reply 14):
Isn't it pushed by the high pressure?

Hah! I worked with a guy once at a company who, although not trained as an engineer, was very technically astute. We used vacuum pumps and such at that job, and he'd often explain something by referring to the "negative pressure" created on something-or-other. That annoyed the hell out of me  Smile

Quoting Jetlagged (Reply 12):
Actually a rudder works just like an aileron. It changes the local aerofoil camber and thus changes the lift the surface produces. The only difference is the axis the surface acts in.

 checkmark 

As pointed out, however, the rudder has far less moment-arm to work with. I'd imagine that the increased lift on the downward-moving wing (due to the roll caused by rudder deflection) would cancel out a fair amount of the rolling force provided by the rudder.

Quoting SlamClick (Reply 8):
Get rid of that habit before you ever fly swept-wing aircraft.

For what reason, out of curiousity?
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PhilSquares
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RE: Silly Question Regarding Rudder Deflections

Mon Aug 25, 2008 7:43 am



Quoting SlamClick (Reply 1):
Now I suspect that, say, a T-38 would be rather different.

The reason has to do with the effectiveness of the actual control surface. On conventional straight wing aircraft, the rudder works very different than it does on swept wing aircraft. I only have about 80 hours in light aircraft, so I am far from being an expert, but I do have about 22000 hours in swept wing aircraft.

I was a T-38 instructor, many years ago and one of the things we would do as a demonstration of the swept wing characteristics of the T-38. We would do a full aft stick stall, which was just what it says. The aircraft would enter a conventional stall, where on a swept wing aircraft, the wing stalls from the wing tip inward. Thus, the conventional controls, ailerons, become ineffective. As the stall develops, the wing is completely stalled, and there is no longer any buffett and the IVSI is pegged at a 6000/FPM descent. However at higher angles of attack, the rudder is extremely effective as a control surface and you can still do a rudder roll by a smooth application of rudder.

In a swept wing aircraft, at higher angles of attack, the ailerons which are normally located on the outboard sections of the wing, are less effective due to the stalled condition that exists. The rudder since it's not effected by the ever increasing angle of attack remains effective.
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Starlionblue
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RE: Silly Question Regarding Rudder Deflections

Mon Aug 25, 2008 9:01 am



Quoting Vikkyvik (Reply 16):
Quoting SlamClick (Reply 8):
Get rid of that habit before you ever fly swept-wing aircraft.

For what reason, out of curiousity?

My guess is that you risk dutch roll and all sorts of other nasty behaviors. Or could end up parking your aircraft in a residential neighborhood on Long Island.
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RE: Silly Question Regarding Rudder Deflections

Mon Aug 25, 2008 2:09 pm



Quoting Vikkyvik (Reply 16):
We used vacuum pumps and such at that job

Damn! In public? Here in Germany nobody uses "toys" at work Big grin
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vikkyvik
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RE: Silly Question Regarding Rudder Deflections

Mon Aug 25, 2008 6:07 pm



Quoting PhilSquares (Reply 17):

In a swept wing aircraft, at higher angles of attack, the ailerons which are normally located on the outboard sections of the wing, are less effective due to the stalled condition that exists. The rudder since it's not effected by the ever increasing angle of attack remains effective.

Hmmm. I had thought that one of the reasons for wing twist (higher AOA inboard) was to ensure that the wing stalls at the root first - for the specific reason of maintaining controllability with the ailerons.

Am I mis-remembering something?

Quoting NicoEDDF (Reply 19):
Damn! In public? Here in Germany nobody uses "toys" at work

I didn't know a vacuum pump was a toy. Apparently different terminology between countries  Smile
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PhilSquares
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RE: Silly Question Regarding Rudder Deflections

Mon Aug 25, 2008 7:08 pm



Quoting Vikkyvik (Reply 20):
Hmmm. I had thought that one of the reasons for wing twist (higher AOA inboard) was to ensure that the wing stalls at the root first - for the specific reason of maintaining controllability with the ailerons.

Am I mis-remembering something?

Not with a swept wing aircraft. The most unfavorable stall characteristics are found with the swept wing, which is used in transonic aircraft to reduce wave and parasite drag at cruise speeds. The sweep causes high induced drag and stall conditions at low speed. The sweep creates an induced upwash angle of the relative wind at the leading edge that increases from wing root to tip. This means that the wingtip is flying at a higher angle of attack than the root. Thus, it will reach its critical angle of attack first. The wingtip is the worst possible location for an initial stall, since loss of aileron control is the result. The burbling airflow off the wingtips does not encounter the tail assembly and thus does not give the pilot a natural stall buffet warning.

On straight wing aircraft the wing stalls from the wing root and moves outboard.

So, to answer your question, yes you are mis-remembering something.
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Blackbird
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RE: Silly Question Regarding Rudder Deflections

Mon Aug 25, 2008 9:08 pm

PhilSquares,

But aren't most swept-wings designed with a twist so the incidence outboard is lower than mid-span and inboard so you get a stall that starts mid-span to root, then progress outward or something to that effect?


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RE: Silly Question Regarding Rudder Deflections

Mon Aug 25, 2008 9:49 pm



Quoting Vikkyvik (Reply 20):
I didn't know a vacuum pump was a toy.

http://shop.beate-uhse.com/shop2/ind...nce=1&onEnterFrame=[type+Function]

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vikkyvik
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RE: Silly Question Regarding Rudder Deflections

Mon Aug 25, 2008 11:02 pm



Quoting PhilSquares (Reply 21):
So, to answer your question, yes you are mis-remembering something.

Thanks for the explanation.

Quoting NicoEDDF (Reply 23):
http://shop.beate-uhse.com/shop2/ind...nce=1&onEnterFrame=[type+Function]

Warning: explicit content

I figured that's what you were referring to  Smile
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tdscanuck
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RE: Silly Question Regarding Rudder Deflections

Tue Aug 26, 2008 12:03 am



Quoting 474218 (Reply 13):
Congratulations, you are the first person (beside myself) that understands that the rudder doesn't push the nose of the aircraft.

No, he's not.

Quoting 474218 (Reply 13):
But that the the tail end is sucked in the the low pressure created by deflecting the rudder.

The tail can't see absolute pressure, just pressure differential. It's equally correct to say it's pushed by the high pressure on one one side or sucked by the low pressure on the other.

Quoting PhilSquares (Reply 17):
The aircraft would enter a conventional stall, where on a swept wing aircraft, the wing stalls from the wing tip inward.

Did we suddenly stop designing wings with washout? That's the primary reason you do put in washout (other than moving the load inboard). Commercial airliners do not stall tip first.

Tom.
 
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RE: Silly Question Regarding Rudder Deflections

Tue Aug 26, 2008 4:38 am



Quoting PhilSquares (Reply 21):
The burbling airflow off the wingtips does not encounter the tail assembly and thus does not give the pilot a natural stall buffet warning.

Lockheed L1011 aircraft.

Although this aircraft does indeed have a stick shaker fitted, when a stall is approached with the flaps/slats retracted, natural stall buffet is first noticed, prior to stick shaker activation.
A notable characteristic of this aircraft.
 
PhilSquares
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RE: Silly Question Regarding Rudder Deflections

Tue Aug 26, 2008 5:33 am



Quoting Tdscanuck (Reply 25):
Commercial airliners do not stall tip first.

Unless you can change the physics of a swept wing aircraft, they do stall from the tip inward. That's why transport category aircraft have a stick shaker/stick pusher. Initial buffett in a swept wing aircraft will be felt when the wing is about 1/2 stalled. The outboard control surfaces will already be losing their effectiveness then.

Quoting Blackbird (Reply 22):
But aren't most swept-wings designed with a twist so the incidence outboard is lower than mid-span and inboard so you get a stall that starts mid-span to root, then progress outward or something to that effect?

No.
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ALexeu
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RE: Silly Question Regarding Rudder Deflections

Tue Aug 26, 2008 9:37 am

Are these the reasons while B732 (UA I think) crashed in Colorado years ago (off course not including mechanical problems of rudder)?
 
PhilSquares
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RE: Silly Question Regarding Rudder Deflections

Tue Aug 26, 2008 9:59 am



Quoting AlexEU (Reply 28):
Are these the reasons while B732 (UA I think) crashed in Colorado years ago (off course not including mechanical problems of rudder)?

Certainly at higher angles of attack, on a swept wing aircraft, the rudder will be more effective.

See here www.ntsb.gov/ntsb/brief.asp?ev_id=20001212X16583&key=1
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jetmech
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RE: Silly Question Regarding Rudder Deflections

Tue Aug 26, 2008 11:34 am



Quoting Tdscanuck (Reply 25):
Did we suddenly stop designing wings with washout?



Quoting PhilSquares (Reply 27):
That's why transport category aircraft have a stick shaker/stick pusher. Initial buffett in a swept wing aircraft will be felt when the wing is about 1/2 stalled. The outboard control surfaces will already be losing their effectiveness then.

Out of curiosity, aren't some current swept wing transport types designed with washout? I have no references as such, but I have heard many times that the 747 for instance does have wings incorporating washout.

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PhilSquares
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RE: Silly Question Regarding Rudder Deflections

Tue Aug 26, 2008 12:22 pm



Quoting JetMech (Reply 30):
Out of curiosity, aren't some current swept wing transport types designed with washout? I have no references as such, but I have heard many times that the 747 for instance does have wings incorporating washout.

No, the 744 winglets do not delay the onset of the stall. It still stalls from the wingtip inwards.
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bond007
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RE: Silly Question Regarding Rudder Deflections

Tue Aug 26, 2008 1:44 pm



Quoting JetMech (Reply 30):
Out of curiosity, aren't some current swept wing transport types designed with washout? I have no references as such, but I have heard many times that the 747 for instance does have wings incorporating washout.

Well, presumably for the same reasons, the outboard portion of the 747 wing (not sure what models), is a degree or two less swept than the inboard portion.

Jimbo
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ALexeu
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RE: Silly Question Regarding Rudder Deflections

Tue Aug 26, 2008 2:51 pm



Quoting PhilSquares (Reply 29):
Certainly at higher angles of attack, on a swept wing aircraft, the rudder will be more effective.

See here www.ntsb.gov/ntsb/brief.asp?ev_id=20...key=1

And perhaps speed, since it was fully deflected?
 
PhilSquares
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RE: Silly Question Regarding Rudder Deflections

Tue Aug 26, 2008 4:25 pm



Quoting AlexEU (Reply 33):
And perhaps speed, since it was fully deflected?

Speed? No, it's all angle of attack. That's what's so good about angle of attack, the wing will stall at the same angle of attack, no matter what the speed of the aircraft is...
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ALexeu
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RE: Silly Question Regarding Rudder Deflections

Tue Aug 26, 2008 5:33 pm



Quoting PhilSquares (Reply 34):
Speed? No, it's all angle of attack. That's what's so good about angle of attack, the wing will stall at the same angle of attack, no matter what the speed of the aircraft is...

So, is it the critical angle of attack (about 15 degrees)?
I assume that it's only under the condition that the rudder is fully deflected
 
SlamClick
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RE: Silly Question Regarding Rudder Deflections

Tue Aug 26, 2008 5:46 pm



Quoting Vikkyvik (Reply 16):
For what reason, out of curiousity?

Sorry, lost my computers for a few days. The answer:

Quoting Starlionblue (Reply 18):
My guess is that you risk dutch roll

...is indeed what I was referring to. You can get into Dutch roll with rudder, you will not get out of Dutch roll with rudder. You will end up using aileron/roll spoiler to sort of "slap down" the rising wing. You can probably Google that for a better explanation but take our word -

Quoting PhilSquares (Reply 34):
That's what's so good about angle of attack, the wing will stall at the same angle of attack, no matter what the speed of the aircraft is...

That of course refers to a conventional stall. When talking about the rudder, separation of airflow can happen sooner due to turbulent wake from other parts of the aircraft. It is not reasonable to expect the full angle or effectiveness in this case.
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Blackbird
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RE: Silly Question Regarding Rudder Deflections

Tue Aug 26, 2008 6:35 pm

PhilSquares,

Even modern airliners stall and pitch-up?

I thought wing twist cured that problem, how weird... then what's the twist for?


Blackbird
 
SlamClick
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RE: Silly Question Regarding Rudder Deflections

Tue Aug 26, 2008 7:09 pm



Quoting Blackbird (Reply 37):
Even modern airliners stall and pitch-up?

I thought wing twist cured that problem, how weird... then what's the twist for?

I think it might be wise to be more specific in conditions if the assertions are becoming more specific. While power ON and power OFF do not materially affect stall speeds in jets, configuration most certainly does.

So, talking about a "clean" stall, if the tips tend to stall first then as the stall develops out there the center of lift for the remaining unstalled part of the wing moves forward. The CG does not, and the result is a pitch up tendency. At the other end of the envelope, at too-high mach numbers they tend to shock stall near the root and progress outboard. So the upshot of these two phenomenoids is that if you are going too slow the stall will have some tendency to pitch you up and make you slower and if you are going too fast it will tend to make you pitch down (mach tuck) and make you go faster. There are lots of design features in use to ameliorate these effects.

Now think about a jet in the landing configuration. Extending the high-lift devices significantly alters the wing geometry. Out near the tip you may have slats only, in near the root you may have slats or leading-edge flaps and trailing edge flaps which probably will be multi-slotted. Since wing chord is measured from leading edge to trailing edge and all of these devices move one or the other of those, they all alter the chord. The chord, compared with the longitudinal axis is the angle of incidence. If we assume that the airflow is from the same direction all along the span of the wing, then the angle of attack is higher near the root and lower near the tip. That will affect stall characteristics in this configuration. It is also true that the tips are not carrying their share of the load in this configuration and at approach speeds.

I'm guessing about what might have been intended in posts above, with this next, but when a "pitch up" tendency is discussed, one might also think about engines slung under the wings and forward of the CG. If recovery includes increasing thrust and considering that aerodynamics are less a factor at lower speeds (including the fletches - tailplanes) then adding power will tend to rotate the airplane around its CG - resulting in a pitch up for underwing engines and a possible pitch down for high tail-mounted ones. Not a huge factor but something to be observed anyway.
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PhilSquares
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RE: Silly Question Regarding Rudder Deflections

Tue Aug 26, 2008 7:49 pm



Quoting Blackbird (Reply 37):
Even modern airliners stall and pitch-up?

Please remember, the training pilots receive is up to stick shaker which is not a full stall. I have done acceptance flights where we pull the stick shaker CB and we must get initial buffett +1/-0 knots from computed. But to take any airliner to a stall puts quite a bit of stress on the structure of the aircraft.

If we're talking about an accelerated stall, then there is a definite pitch up, and as SlamClick has written, during the recovery, when power is applied with underslung engines, there is a definite pitch up.
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SlamClick
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RE: Silly Question Regarding Rudder Deflections

Tue Aug 26, 2008 8:09 pm

I forgot to mention that wing taper and not just sweep affects stall characteristics and some of these things can be better understood with that in mind.

This would include flap taper, or effective taper due to extension geometry. The angle of incidence at the inboard end of a given flap panel is likely to be different from the angle at the outboard end due in part to taper.

Since these things cannot be changed except by selecting a different flap setting, flying characteristics are the net result of a lot of things no one has given any thought to since the early design days.
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Starlionblue
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RE: Silly Question Regarding Rudder Deflections

Wed Aug 27, 2008 1:55 am



Quoting SlamClick (Reply 38):
phenomenoids

A google search reveals:

No definitions wewe found fow phenomenoid.

Suggestions:

- Make suwe aww wowds awe spewwed cowwectwy.
- Seawch the Web fow documents that contain "phenomenoid"


Great word though. And yes, I have the Google language set to "Elmer Fudd". "Bork! Bork! Bork!" and "L33t" were just too hard to read.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
SlamClick
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RE: Silly Question Regarding Rudder Deflections

Wed Aug 27, 2008 2:58 am



Quoting Starlionblue (Reply 41):
Great word though.

It's one of those words where I can never remember the correct number, tense, gender or case endings so I append my own. Kind of like a particular college alumperson.

Extra points without looking it up - what is plural for Opera?

V

V

V


Trick question. Opera is plural, opus is singular.

Bravo Tango Whisky since "phenomenoid" isn't Googleable, can I copyright it? Maybe start a religion?

It worked for a coined synonym for "epistemology" but you'll have to check that out for yourself. I'm suddenly paranoid.
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Starlionblue
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RE: Silly Question Regarding Rudder Deflections

Wed Aug 27, 2008 3:10 am



Quoting SlamClick (Reply 42):
Trick question. Opera is plural, opus is singular.

Etymologically, that is quite interesting. It must come directly from the latin. In Italian, the plural for opera (which means "work" as in for example "work of art"), is "opere". Forked evolution. Note also the word "operate" which is related.
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RE: Silly Question Regarding Rudder Deflections

Wed Aug 27, 2008 3:26 am



Quoting Starlionblue (Reply 43):
Note also the word "operate" which is related.

Leading us to the ultimate etymological cul de sac "Tech / Ops"
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tdscanuck
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RE: Silly Question Regarding Rudder Deflections

Wed Aug 27, 2008 5:54 am



Quoting PhilSquares (Reply 27):
Unless you can change the physics of a swept wing aircraft, they do stall from the tip inward.

They can't all do that...for *any* wing configuration you can design a washout that will cause the wing to stall at the root first. It's not inherent to the physics of swept wing aircraft.

Quoting PhilSquares (Reply 27):
That's why transport category aircraft have a stick shaker/stick pusher.

I thought that was because you don't get any feedback from a hydraulically boosted flight control system.

Quoting JetMech (Reply 30):
Out of curiosity, aren't some current swept wing transport types designed with washout? I have no references as such, but I have heard many times that the 747 for instance does have wings incorporating washout.

All current Boeing and Airbus products have washout.

Tom.
 
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RE: Silly Question Regarding Rudder Deflections

Wed Aug 27, 2008 6:42 am



Quoting Tdscanuck (Reply 45):

I thought that was because you don't get any feedback from a hydraulically boosted flight control system.

You get feedback from the airframe, buffet and it gets very quiet. The stick shaker/pusher was so you don't even get close to initial buffet.

Quoting Tdscanuck (Reply 45):
All current Boeing and Airbus products have washout.

I never said they didn't. However, I can assure you the 744 stalls just like any other swept wing aircraft, from the wing tip inwards. In addition, the airframe buffet in a fully developed stall is quite severe.

Quoting SlamClick (Reply 36):
That of course refers to a conventional stall. When talking about the rudder, separation of airflow can happen sooner due to turbulent wake from other parts of the aircraft. It is not reasonable to expect the full angle or effectiveness in this case.

On a T tail aircraft yes, but with a conventional swept wing arrangement, the rudder will be much more effective as the wing approaches it's max angle of attack. As it exceeds it, again, the rudder will be extremely effective. It doesn't make any difference if it's a conventional stall or an accelerated stall. Once the aircraft enters a spin, stall and yaw, then the rudder as well as the wings will cease to have any effectiveness.
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jetmech
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RE: Silly Question Regarding Rudder Deflections

Wed Aug 27, 2008 10:31 am



Quoting JetMech (Reply 30):

I was going to ask a follow up question according to the responses to reply 30, but the question has been answered  Smile !

Quoting Tdscanuck (Reply 45):
All current Boeing and Airbus products have washout.



Quoting PhilSquares (Reply 46):
I never said they didn't. However, I can assure you the 744 stalls just like any other swept wing aircraft, from the wing tip inwards.

Fair enough. In this case then, what is the general purpose of washout in relation to swept wings? What does it do specifically on Boeing and Airbus commercial types?

I was always under the false impression that washout was incorporated into swept wings to make the root sections stall first ( I also understand that this can be achieved with careful airfoil selections ).

The 744 stalls wing tip first, so what does washout actually achieve? From what I can gather, it seems that washout may "soften" the initial stall from the wingtips. Is this somewhat closer to what actually happens?

Regards, JetMech
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PhilSquares
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RE: Silly Question Regarding Rudder Deflections

Wed Aug 27, 2008 11:14 am



Quoting JetMech (Reply 47):
The 744 stalls wing tip first, so what does washout actually achieve? From what I can gather, it seems that washout may "soften" the initial stall from the wingtips. Is this somewhat closer to what actually happens?

Exactly! While it is possible to change the aerodynamics of a swept wing aircraft, the entailing cost and weight penalties would make it impossible to market. That's why the stick shaker/pusher has come about in conventional controlled aircraft. Airbus, has a pitch limiter while Boeing on the 777 still has a stick shaker.

I can assure you the 747-400 still stalls just like any other swept wing aircraft, from the tip inward.
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Nicoeddf
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RE: Silly Question Regarding Rudder Deflections

Wed Aug 27, 2008 11:28 am



Quoting JetMech (Reply 47):
The 744 stalls wing tip first, so what does washout actually achieve? From what I can gather, it seems that washout may "soften" the initial stall from the wingtips. Is this somewhat closer to what actually happens?

And washout is the term for exactly what?  ashamed 

The translation gives some indication toward the upward bending of a wing under load.
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