Mind Refresher Questions - "Why the use of rudder"

[Tomo]

Mind Refresher Questions - "The benefit of top rudder"

 

This one...

 

- What is the benefit of top rudder in a steep banked turn? Especially at Low Level.

 

 

[Tomo]

Now this one would have been drummed into you during your training, but now you've got your license and on your own, and he can't give you a rap over the knuckles any more, so why, it mustn't be that bad to do it just little bit...

 

- So why can't you tighten a turn with just a little more rudder? Why it is a rudder isn't it? and that's what they do in boats....

 

Disclaimer, I'm just wording it like this to make people think!

 

 

[Mazda]

In straight and level flight the rudder is vertical and the elevator is horizontal. Imagine the aircraft flying at a 90 degree angle of bank. The rudder is now horizontal and the elevator is vertical. In effect, the rudder will still yaw the aircraft, but the rudder is acting a bit like an elevator.

 

So the steeper the turn, the more you can think of rudder as working like an elevator.

 

Applying top rudder yaws the aircraft's nose UP and helps to maintain height in the turn. :)

 

 

[mAgNeToDrOp]

maybe because this can happen?... pucker factor 11/10

 

[YOUTUBE]swk25weGyYo[/YOUTUBE]

 

 

[facthunter]

Why do it?

 

You were taught it for a good reason. If the ball is out of centre you can come unstuck real fast. You do need to have the stick BACK as well, to cause the problem, but the plane will drop a wing long before it would have normally stalled and can catch you out. A docile stall will become a quick wing drop. If the aircraft has a low rate of roll (this is such a rare thing in the type of aircraft we fly that you could ignore the possibility, almost) , you can increase the rate of roll by applying rudder and leading the aileron application a bit . This will cut out some of the adverse yaw that some aircraft exhibit, due to aileron drag, and will be beneficial when going from a steep turn to a steep turn in the other direction. Try it. Nev..

 

 

[Guest wondai aviation]

This may interest you .

 

What differentiates our aircraft from a car , on the ground , not much , we can speed up , slow down , turn right and left , just like a car , on the ground that is ! whats the one thing our A/C can do that a car cannot ? FLY ! , now hang on , that takes lift ! , but thats not enough info , because we need "vertical lift" to stay up there , you see you can turn the lift produced by the wings horizonal then it take a form of centrophedal force ( I believe a car suffers "centrophugal force") anyway , I believe in the old days ( turn of century) the Wright Bros & the like predominately used the rudder to turn , i know there was wing warping and all that , but anyway they made these flat , car type turns , until someone came up with the idea , well why can't we use the tilt part of a turn , the "centrophedal part , the horizontal lift part , by banking the aircraft and the "lift" will actually help change the aircraft's direction ! , which is of course part of the definition of what a turn is , anyway the rest is history , they have stuck with Ailorons ever since ! ... .... see ya !

 

 

[Guest Bert Foster]

Unless you are deliberately doing a slipping turn the ONLY use of rudder, top, bottom, left or right, is to keep the ball in the middle.

 

 

[Guest Bert Foster]

This is all very clearly explained in the Fly Better Book One and it is available as a free download at http://www.flybettter.com.au so there should be no excuse for killing yourself with the incorrect use of rudder.

 

 

[hihosland]

As I understand it

 

The use of the rudder is to keep the forces acting on the aircraft in balance. The ball gives you an indication of how well those forces are balanced AFTER the event. There is a time lag between the aircraft doing something and the ball recording that event.

 

Imagine a bicycle fitted with a inclinometer ball and trying to ride that bicycle on an ice rink.

 

If you keep all the forces in balance you will be able to execute turns on the ice and the ball will stay in the centre. However if you concentrate on the ball rather than the bicycle you will probably crash when the wheels skid out from under you.

 

 

[facthunter]

Top Rudder.

 

IF you try to do a SUSTAINED 90 degree banked turn, you cannot do it as you are relying on the vertical component of lift which is zero at 90 degrees. IF you choose to use the keel surface to provide lift, the rudder is the control to do that with. Any time you have a side load in the cockpit, (you are being forced to one side or the other), the keel surface is providing that force. ie. You are skidding.

 

This is observed when an aerobatic aircraft does a "knife edge" after take off. High speed aircraft can fly with wings vertical using the fuselage for lift. A hesitation or even a well-coordinated slow roll wll use "top" rudder to stop the nose dropping and height being lost. Also uses forward stick when inverted for the same reason.

 

NORMALLY the rudder is a "balance" control. You keep the ball in the centre, or the seat of your pants tells you. or (in an open cockpit) the wind does not come from the side, it comes from the front. This is when the plane flies best, it is most efficient and feels the most comfortable and everything is at its most safe (stall wise).

 

I would advise against using top rudder in a turn. The procedure is unsafe. Turns are best made coordinated. When the ball is "off centre" moving the stick back will put you in a situation where the aircraft is likely to do a very rapid FLICK roll. This is particularly likely in a turn where the stick is already a fair way back, and not far from th position where it will cause the wing to stall anyhow. As you are already skidding you guarantee that one wing will stall before the other, and this is very sudden., when it occurs Nev

 

 

[facthunter]

Link.

 

Sorry Bert, The link didn't work for me . Is it still current? Nev

 

 

[ahlocks]

There's a typo in the link.

 

Try this:

 

FLY BETTER......

 

 

[facthunter]

Link 2

 

Thanks. Not all books are published. yet. These should be good.

 

NOTE.. This thread is duplicated. Nev

 

 

[Admin]

Threads now merged!

 

 

[Yenn]

What is the benefit of top rudder in a steep banked turn? Especially at Low Level.

 

I have only just seen this thread and in answer I cannot think of any good reason to use excess rudder in a turn. Keep the ball centred and you will have as much lift as you can get.

 

My opinion is that you can do whatever you like with a rudder when you have height, but incorrect rudder use close to the ground is a killer. The problem arises when you are low and turning, you are flying in the air mass but you can see how turn is progressing in relation to the ground, this causes you to think you are skidding or slipping and can lead to incorrect rudder inputs.

 

The only place I see close to the ground for unusual rudder is when you are slipping to lose height.

 

 

[Guest weekendwarrior]

Excellent thread, love the video!

 

During PPL training you are being taught to use rudder for balanced turns, and counter yaw P-factor on take-off, kick it back for crosswind landings, but that's about it.

 

When you learn gliding / soaring, you are being hammered on rudder work.

 

In a glider you don't have a ball but you have a yaw string to show airflow vs where the nose in pointing. Flying straight you want to have it all lined up to minimize the drag ==> rudderwork.

 

Or you want to side slip to lose height ==> rudderwork.

 

Most importantly you spend a fair bit of time thermalling in lift, that is going around in circle at 45 degrees of bank and fairly slowly (45 to 50kts). Not much margin above stalling, and with the angle of bank, with too much rudder and skid in stall means a certain spin. It is thus safer to have a bit of top rudder - I'd rather slip than spin. Also the upper wing is flying slightly faster that the lower wing (it's travelling a greater distance), so it's got more lift and will bank more if you don't do anything, so you also have to compensate for that - with a tiny weeny little bit of opposite ailerons and top rudder.

 

In a glider you also practice spins (not gentle wingdrops incipient spins, the real thing), this is seriously scary sh!t the first few times, like in that video, but eventually it becomes fun and you certainly remember what the rudder is for after that!

 

The biggest danger remains in the circuit - turning base or final too flat (the safest angle of bank is actually 45 degrees, believe it or not), too slow, and adding rudder to compensate - again just like in the video. A stall/spin in the circuit is almost certainly deadly, whereas a slip can be dealt with.

 

 

[poteroo]

Agree with Yenn regards the original post about using 'top' rudder in a turn. The last place you want to be flying cross controlled is anywhere lower than 500 ft agl. It's difficult enough to recover from a stall in a low turn, without trying to create a stall + spin situation.

 

Doing this to excess will lead to the infamous mustering stall, where you'll spin up and over, out of the turn. (In Canada and the US it's known as the moose stall).

 

Solution = take off the angle of bank, take the pic, then resume the steep turn.

 

happy days,

 

 

[facthunter]

Recovery.

 

When it all goes wrong, roll out of it with aileron and recover from the dive "gently". Unless you are stalled when it is a different matter.. Remember speed building up lots of "G" you are spiralling. Speed constant and tending low (near stall) you are stalled and spinning. Your aileron is ineffective and the rudder is the primary control to get you out of the spin.. Your turn needle (if you have one) is a good indicator of direction. Spiral, get it back to centre with aileron. Spin , get it back with rudder and push forward with the stick (generally). NOTE. Individual aircraft behave differently when spinning due to the rudder being "masked" by the elevators. Even spin proficient pilots should familiarise themselves with the characteristics peculiar to the aircraft to apply the appropriate technique for spin recovery. Nev.