Steering

[Lump Jockey]

How, and when, are planes steered by using
a)ailerons, if possible, the "steering wheel effect"?
b)the tiller
c)rudder
I've always been confused by this, so don't worry if you think your responses are simplified for numb-skulls, because that's what i am!:p And what does the tiller look like in regards to shape and such? (A little windable handle, isn't it?). Also, is it difficult to steer with rudder pedals and not brake at the same time? Thank you for your help as always!

[Flyboybrad]

Ok, here we go....

A plane has three primary control surfaces.

Ailerons : These control the roll of an aircraft. As the control columm is moved to the left, the left aileron moves up and the right aileron moves down. These control deflections alter the amount of lift produced. Resulting in a roll angle to the left. etc, etc

Rudder: This is found on the vertical stabiliser. This is controled by the lower pedals. Pressing the left lower pedal down will result in the aircraft to yaw to the left, vise versa.

Elevator: this is on the rear horizontal wing. This controls pitch (up/down)

Simple yeah?

I think you mean "TRIMMER"....this adjusts the elevator. It is used to dampen out control forces, and yes it is on a spinning wheel :)

Braking and rudder controls are seperate. There are two sets of pedals, the lower are for rudder control, and the upper two are used when braking on the ground. Funnly enough these are NOT airbrakes.

[FlapsOne]

The Tiller is used to steer the aircraft on the ground. It normally turns the nosewheel and the rest of the aircraft follows in sympathy.

In the 737 it's a triangular segment (shaped like slice of pizza), with a gap for the fingers to slide into.

There's always one on the left hand side, just forward and left of the Captain's knee.

Optionally one can also be fitted on the right hand side.

[Flyboybrad]

thanx....:)
never stop learning

I have a question... how are air brakes activated?

[Tinstaafl]

To follow on from the previous..

I think the question relates to steering on the ground.

Usually the rudder pedals also connect to the nose wheel. Depress the left pedal and the nosewheel moves left etc

Additionally, mounted on the rudder pedals, but able to be depressed independently, are a second set of pedals. These control the brakes.

The brake pedal on the left rudder pedal controls the left mainwheel(s) brakes, right brake pedal the right. This gives the ability to use differential braking eg like a skid steer bulldozer.

The most common mounting is for each brake pedal to be mounted above its respective rudder pedal. Rudder/nosewheel can be used without activating the brakes or, by moving one's foot up a bit, brakes can be used as well.

Larger a/c also use a tiller ie a small steering wheel-like device. This commands a greater range of movement of the nosewheel compared to the rudder pedals and is used at low speeds. At higher speeds the rudder & nosewheel steering is sufficient.

The tiller is usually located to the side of the control column, on or near the cockpit sidewall. Interestingly, some Russian designs incorporate it into the control column as a separate yoke.

Additionally, multi-engine a/c have the option to use differential power to assist with turning or crosswind handling. More applicable to wing mounted designs than centerline/near centerline types.

Single engine types can also benefit from power being applied. The rudder is usually in the slipstream so when power is applied the increased airflow makes the rudder more effective.

There are variations to the above and include:

Having a hand activated brake eg the Victa Airtourer

Not connecting the rudder pedals to the (freely castering) nosewheel & using differential braking only. eg Grumman AA5 series

Using finger steering eg the Piper Aerostar uses a couple of rocker switches that activate nosewheel hydraulic rams.

Heel brakes where the brake pedals are mounted below the rudder pedals and activated with your heels instead of your toes/ball of your foot. Has been used on some british designs, Chimpmunk I think.

[FlapsOne]

Airbrakes - big planks on the wings. Activated by a lever on centre pedastal. Moved by Hydraulics.

They stick up into the airflow to either slow you down, increase rate of decent or, when activated (manually or automatically, depending on type) after touchdown, to kill lift and make it stick to the ground.

[Dop]

Tinstaafl mentioned the Grumman AA5 - I'm currently learning in one of those and it took me AGES to get the hang of taxiing. Once I'm on the taxiway I'm OK now, but the number of times I nearly went off when taxiing to the hold was ridiculous.
Training planes at Biggin are usually parked up on a bunch of paving slabs set in the ground off a small taxiway. Trying to park when the ground is wet and muddy and your wheels just slide is a b'stard. Next time it's like that I get out and push...

[Lump Jockey]

Thanx TINSTAAFL! Pretty much what I was after. Quite a thorough explanation, much appreciated!;)
Of course, I know what much of an aircraft's gizmoes are for, it was just the steering on the ground that has had me stuck for a while. So, basically, correct me if I'm wrong, tiller usage is mainly for slow turns where the rudder/nose wheel pedals don't do their job sufficiently enough. Rudder is probably used mostly on take offs, (and of course landings, but they aren't done on the ground til the end!;) ). Then there's the ailerons, which I'm still not sure about? I know how they work in the sky, but I've read elsewhere they can be used to turn an aircraft on the ground! If this is true, why are they used specifically, and when? Thanx again!

[foghorn]

Dop, don't worry, you'll get used to it. The AA5 is a wonderful aircraft, particulaly the larger of the breed, the Tiger.

I know exactly what paving slabs you mean at Biggin, and it's a real knack to get on to them, but once you've got it, you don't lose it. Also the AA5's differential braking means it can turn on a sixpence, which is useful in most cramped UK GA fields...

[FlyingForFun]

Lump Jockey,

As far as I'm aware (I'm sure one of the real airline pilots will correct me if I'm wrong) there's usually a specific speed below which the tiller is used, both on take-off and landing.

As for the ailerons, there are a couple of times that you might use them on the ground. In general, the bigger the aircraft, the less important they are.

During the take-off and landing roll, you would use into-wind aileron. This is to prevent the wind blowing you sideways off the runway, or from lifting a wing - it's not realy "steering" as such.

While taxying, you should (but most pilots don't), on most aircraft, use into-wind aileron when taxying with a headwind, and out-of-wind aileron when taxying with a tailwind. Again, nothing to do with steering - this is to prevent the wind from lifting the into-wind wing. Obviously on a 747 there is very little chance of the wind doing that! But on a little single-seater aircraft it's a real possibility with any kind of wind.

It's also possible to use adverse yaw of ailerons to assist with steering. (Do you know what adverse yaw is? If not, just say, and I'll post again to explain, unless someone beats me to it.) You would use the ailerons in the opposite direction to the way you're turning - left aileron for a right turn. Adverse yaw always works in the opposite direction to the way you've moved the ailerons.

Almost all modern aircraft have sufficient control, using nose-wheel or tail-wheel steering and differential braking, that it would be very unusual to see this method used! But there are a small number of older designs out there, with no brakes and just a tail-skid at the back, that have no real method of steering except using aerodynamic controls (or, more commonly, a man standing by the wing helping it around the corner!) If you're turning a tight corner in this type of aircraft, then adverse yaw might be useful. Bear in mind, though, that you'd need a reasonable amount of speed for the adverse yaw to have any effect. In fact, you'd need a reasonable amount of speed for the rudder to have any effect too, but less so. If you find yourself having to resort to this, then unless you're very experienced in that type of aircraft, you'd be better off shutting down, getting out and pushing! But it does make a nice demonstration, even if it has little practical value.

FFF
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