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Use Of Rudder In Large Transport Category Airplanes

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Use Of Rudder In Large Transport Category Airplanes

Old 24th Mar 2021, 20:02
  #21 (permalink)  
 
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Originally Posted by tdracer View Post
IIRC, rudder authority is reduced at higher airspeeds, but don't recall specifics.
Yes, it was called the rudder ratio system.

I see no reasons (because there aren’t any ) to use rudder on a large jet, x wind, engine failure etc. excepted . period.
Chipmunks, Tigers, Cessnas and Pipers are different.
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Old 25th Mar 2021, 02:08
  #22 (permalink)  
 
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You use the rudder when itís time for you do some pilot stuff aka when itís appropriate.
From small to large all aircraft fly the same, you just donít fly them the same.
Low speed regime use the rudder pedals, high speed regime you donít.
The outboard ailerons lock out at 235 kts, Iíd say thatís a pretty good clue from Mr Boeing.
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Old 25th Mar 2021, 03:07
  #23 (permalink)  
 
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To add to Vessbot's post, on a large aircraft the radius of turn made by the extremities (nose, tail) will differ to that of the CoG and have noticeable effects, compared to a small aircraft such as a Chipmunk. If the slip/skid was of a self contained type, as used on light aircraft, and installed in a large aircraft cockpit centering the ball would mean everything aft of the cockpit would be in a skid. IMHO
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Old 25th Mar 2021, 03:12
  #24 (permalink)  
CCA
 
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As others have said the so called slip skid indicator is very sensitive and shouldnít be used like on a light aircraft.

Boeing refers to the Slip/Skid as body lateral acceleration.

Iíve always surmised that itís slip/skid indication in a turn is the fact the IRUs are some distance forward of the aerodynamic centre of the aircraft.

The 747 in particular is very good inherently for turn coordination and does not need ďhelpĒ, handling the big jets has a good read.

One thing that isnít really talked about is the large amount of roll induced by the rudder which can cause instability.

3 large rudder inputs:
1. final
2. Flare
3. During the go around!


Last edited by CCA; 25th Mar 2021 at 14:45.
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Old 25th Mar 2021, 05:14
  #25 (permalink)  
 
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Originally Posted by tdracer View Post
IIRC, rudder authority is reduced at higher airspeeds, but don't recall specifics.
Even Airbus does the same. It is called rudder travel limiter.
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Old 25th Mar 2021, 09:12
  #26 (permalink)  
 
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The outboard ailerons lock out at 235 kts, I’d say that’s a pretty good clue from Mr Boeing.
If "Mr Boeing" wanted you to read something into that, I'm pretty sure he'd tell you.
Secondly, if the turn co-ordination provided by the 747 yaw damper was so poor, wouldn't everyone in the cabin be feeling accelerations, other than straight into their seats, every time we go around the corner? As well as flying the thing, I've spent a fair bit of time in the cabin and can't recall my drink ever being spilt while turning, even at low speed.
I think the video of the podstrike shows exactly why a lot of caution is required every time the rudder pedal is touched in the 747. The associated roll is significant and I'd be lying if I said it hasn't surprised me at least once. Hopefully I learned from it and got better the next time. But then again, I tend to follow the guidance that it really doesn't need any rudder until just prior to touchdown and on a wet runway I would say it's only really required once you have main gear touchdown - you can see in that video that the rudder is being hammered at about 50 feet.

Last edited by anson harris; 25th Mar 2021 at 20:12. Reason: Spelling.
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Old 25th Mar 2021, 13:55
  #27 (permalink)  
 
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Originally Posted by BraceBrace View Post
Rule nį1: ... Never ever "tighten the turn" with rudder in low speed on a swept wing.
Lordilord, I wouldn't even let student pilots do that in a microlight, swept wing or otherwise!
(No experience worthy of mention in anything heavier, so p'raps misunderstood)

Last edited by MadamBreakneck; 25th Mar 2021 at 14:54. Reason: I'd missed the n't in wouldn't
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Old 25th Mar 2021, 14:32
  #28 (permalink)  
 
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Can you use the rudder on large jet transports in the same way you might use it on a light aircraft? Yes. Do you need to? No, not really, outside of asymmetric conditions or deliberate crossed controls. I admit to a bit of top rudder turning visual finals with an empty aircraft, just for the fun of it, but I donít think it would impress passengers.

On modern jets, especially FBW ones, there are all sorts of things going on underneath the skin that obviate the need for rudder inputs in normal flight, so youíll just end up fighting those systems...
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Old 25th Mar 2021, 14:42
  #29 (permalink)  
 
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They took the Boeing slip/skid ball off our 737NG panels years ago.
There is an indicator under the roll pointer on the PFD when you need it.
Some sim sessions left me sweating and thinking I need more leg work at gym.
787 much nicer.
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Old 25th Mar 2021, 19:02
  #30 (permalink)  
 
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I had a mate who used the rudder a lot in a VC10 up at 30 odd thousand feet. Back and forth or should that be side to side? it went. Fortunately it stopped once he'd got the probe in the drogue.
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Old 26th Mar 2021, 00:05
  #31 (permalink)  
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Originally Posted by blind pew View Post
In the old days when pilots tried to do a greaser we had a captain, who if he thought you had accidentally got it right in spite of trying extremely hard, would put a large boot of rudder in during the flare and watch how you coped with the secondary effects with a highly swept wing.
Still here to tell the tail.
He would get away with that maybe once at the place I worked....
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Old 26th Mar 2021, 00:57
  #32 (permalink)  
 
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Originally Posted by anson harris View Post
you can see in that video that the rudder is being hammered at about 50 feet.
Thatís a rudder defection to the Left with a pod strike on the Right.
They encountered windshear at low altitude.
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Old 26th Mar 2021, 01:56
  #33 (permalink)  
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WRONG and why rudder should only be used for crosswind correction and engine failures. If the aircraft had a fin out the top and the bottom you’d only get yaw and secondary roll from the wing but there is a significant roll from the top mounted fin when rudder is used inappropriately.

That fin has more wing area than one side of a 757 and they just deployed the entire trailing edge to full deflection.
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Old 26th Mar 2021, 09:06
  #34 (permalink)  
 
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Originally Posted by B2N2 View Post
Thatís a rudder defection to the Left with a pod strike on the Right.
They encountered windshear at low altitude.
Yes, I realise that. What I'm hinting at is that maybe there's some misunderstanding of how to use the rudder during a crosswind landing.
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Old 26th Mar 2021, 09:40
  #35 (permalink)  
 
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Originally Posted by NGjockey View Post
@ BraceBrace:

True. Also true is that part of being rated on an aircraft includes for example being able to perform crosswind takeoffs and landings on slippery runways. If you read the FCOM or FCTM you won't find any information about how many inches of rudder or control wheel input you will need exactly for a particular crosswind or a particular mass. You will apply inputs as needed according to your experience, and that is what I wanted to state with my argument about being able to judge the amount of control input required as highly trained pilots, in any phase of flight.
Yes, but that is training. I sometimes allow people who are scared of crosswind landings in line training to go (established on the ILS with runway in sight) low wing and out again on the approach. It gives them a sense of how much rudder input is required (but it is REALLY important to state that rudder input is gentle & singular and then you hold the rudder in that deflection - never "play" with it) AND how it effects your aileron requirement. The secondary roll effect due to rudder is always there, always, and you have to give it time to show up.

I don't know if it is a common thing on turboprops, but when people come in with turboprop experience they will often "fiddle with the rudder" on final. Some of the aircraft I fly are old classics with not too symmetrical thrust and some rudder trim requirements, and that's always been an excuse for them for the negligence of the secondary roll. It shouldn't be if the thrust is equalized and the trim was set properly. They will hardly ever be able to stabilise the aircraft with the rudder tickling because they end up correcting secondary roll all the way down.

Rudder is "designed" to cope with engine failures and therefore very powerful for "normal" steering. Which is why once the flight controls become more effective (flaps up) or engines less powerfull (high up), the rudder force is generally reduced to more acceptable levels. If you look even look at non-normals, Boeing is very cautious in advertising the use of rudder. Even in manual reversion on the 737, Boeing doesn't stop you from using rudders, but it emphasises not to overcontrol it and be really gentle. Because you always create secondary effect you don't want. Even in an approach to stall - or stall recovery or upset recovery, Boeing says not a single word about use of rudder. The reason is easy: DON'T, as the secondary effect is the nastiest backstabber you can find.

Boeing designed an aircraft where you don't need to use rudder except in a certain set of situations and that is trained for. And I'e never felt uncoordinated in a turn (within the limits of course, but heck I don't even like 30į bank to be honest, 25į in manual flight should get you everywhere as the maneuvering speeds allow you)

BTW: it's one of the hardest things to "de-learn" for the turboprop guys, because there have been many cases where I said "but you were steering with your feet" and they said "no". I truly believe them as there have been too many. They do it without even knowing. Which is why I emphasize "no rudder unless a very specific situation" so hard in this discussion, and the idea you really have to put an effort in "learning the aircraft you fly".

I know the document that started this thread. The background is not about good or bad pilots, it even discusses people with plenty of military background who are very capable pilots. They have used rudder on carrier landings, to pinpoint the nose in dogfights, etc etc... but the main goal here is: learn to use your aircraft as the guys who designed it tell you to.

Tapping the rudder to coordinate a turn "more" does not make you a better pilot (which is also a statement that was posted in the thread starter), as subconciously you might be learning yourself dangerous stuff. Don't tap the rudder in a turn. Learn yourself the right way to fly the aircraft, don't go out and tell the other guy he's not flying correctly as he IS doing it the correct & safest way.

Last edited by BraceBrace; 26th Mar 2021 at 10:21.
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Old 27th Mar 2021, 16:16
  #36 (permalink)  
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Nicely put, like you say you can feel the crew who still fly it like it needs rudder assistance, small roll inputs with small rudder inputs. The problem will be on those gusty days with large roll inputs required then coupled incorrectly with large rudder inputs which can get ugly very quickly but will be blamed on the weather.
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Old 27th Mar 2021, 17:35
  #37 (permalink)  
 
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Originally Posted by blind pew View Post
In the old days when pilots tried to do a greaser we had a captain, who if he thought you had accidentally got it right in spite of trying extremely hard, would put a large boot of rudder in during the flare and watch how you coped with the secondary effects with a highly swept wing.
Still here to tell the tail.
I see what you did there...
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Old 27th Mar 2021, 19:19
  #38 (permalink)  
 
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Having flown big Airbus, the fear seen when discussing the use of the rudder is sometimes irrational. The manuals say it is available for crosswind landings and engine failures but most crew think it is a one off input rather than an adaptable flight control. Obviously it is dumb to put a large input above approach speeds but the latest aircraft even protect dummies from doing this by reducing the rudder authority as speed increases.

I believe if you get a float in a large aircraft and the fuselage has been aligned too early, the only way to prevent lateral drift is with, as you say, the ďsubtleĒ use of rudder. Using aileron when the inner engine is on the runway edge is fraught with danger. Obviously if you are going to miss the TDZ, go around and have another go but a squeeze of rudder to prevent drift is eminently sensible.

All that said it is madness to try and coordinate turns when there is a decent flight control computer between the stick and control surfaces.

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Old 27th Mar 2021, 19:48
  #39 (permalink)  
 
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I've used the rudder to fly runway heading from an initial track, on instruments and VMC. Of course, the runway as a reference will most likely be gone by then.
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Old 31st Mar 2021, 16:43
  #40 (permalink)  
 
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anson harris

So go on, teach us how to use the rudder in a crosswind landing when encountering windshear.
We obviously need it.
I’d love to hear.
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