How does an aircraft turn while taxiing?

Question

I know that an aircraft uses its own power (thrust) while taxiing to move forward. But how does it turn?

Do the front wheels pivot?
Do you simply apply more power to the left engine if you're trying to make a right turn?

If you do apply power to turn, how much power? Wouldn't it tip over the plane? And how do you do it on a single-engine or prop aircraft?

Definitely related, @fooot, but not duplicate. This question doesn't differentiate between "small" and "large" craft, nor have the exclusion of the tiller. Describing the operation of the tiller would make an excellent addition to an answer for this question. — FreeMan, Commented Jul 22, 2016 at 20:23
I vote to re-open the the question as neither of the linked questions or answers properly address free castering nosewheels which are steered by using differential braking and/or differential power. Small aircraft like the Grumman AA-1 and AA-5, and larger aircraft like the Consolidated PBY-5A and B-24, all use free castering nosewheels. I am sure their are many other examples. — Mike Sowsun, Commented Jul 23, 2016 at 16:38
@MikeSowsun I think your point should be emphasize in the question so that it is clear it is not a duplicate. — Manu H, Commented Jul 24, 2016 at 5:33

Fred Larson · Accepted Answer · 2016-07-25 18:57:20Z

6

Primarily steering is accomplished in two main ways:

Steerable nosewheels - Usually limited to tricycle undercarriage, and usually controlled using the same left/right pedals as control the rudder in flight
Using the rudder itself - Often associated with the traditional undercarriage (tail draggers to some). In this case the rudder works on the ground in much the same way as it does in the air - ie, deflecting the rudder pushes the tail in the opposite direction, thus causing the nose to pivot in the required direction.

In addition, steering can be augmented in two ways

Differential braking - often the left and right main undercarriage have their own deferentially controlled brakes. These are usually controlled by "hats" on the top of each rudder pedal. By applying greater braking pressure to, for example, the left wheel will cause the aircraft to pivot more around that wheel causing a left-turning tendency.
Differential thrust - in a similar vane to above, greater thrust applied to the left engine will cause a right turning tendency.

Fred Larson

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answered Jul 25, 2016 at 13:42

Jamiec♦

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$\begingroup$ steerable nosewheels: does that mean that when you use the rudder pedals while taxiing the rudder and wheels turn? or only the wheels do? using the rudder itself: meaning you use the air to turn? how effective is this? don't you need high speed for the rudder to make a difference? (sorry I'm not very familiar though, that is just a general observation) $\endgroup$
– majidarif
Commented Jul 25, 2016 at 13:52
2

$\begingroup$ @majidarif - Both the rudder and the wheels turn in the case of steerable nosewheels, Yes, the rudder uses the airflow to make the aircraft turn on the ground - a surprisingly low, however not insignificant, amount of speed is required to make this work - however it's usually in conjunction with differential breaking. $\endgroup$
– Jamiec ♦
Commented Jul 25, 2016 at 13:57
$\begingroup$ Oh, one thing I should have mentioned is that its not ground speed so much as airflow speed which makes the rudder work on the ground. The propeller is providing that airspeed, not movement over the ground. $\endgroup$
– Jamiec ♦
Commented Jul 25, 2016 at 14:07
1

$\begingroup$ I have an edit pending review, but note that "breaking" is very different than "braking". $\endgroup$
– Fred Larson
Commented Jul 25, 2016 at 18:08
$\begingroup$ @FredLarson - lol, thanks for spotting my awful spelling there. $\endgroup$
– Jamiec ♦
Commented Jul 26, 2016 at 7:31

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user3344003 · Accepted Answer · 2016-07-25 15:47:12Z

4

There are two major systems that are used to turn aircraft on the ground:

Steerable nose wheel.The wheel moves like on a car.
Differential braking (generally only small aircraft). The nose gear is free castering. The pilot eases up on the brakes on one side or the other.

answered Jul 25, 2016 at 15:47

user3344003

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1

$\begingroup$ Not following what the image has to do with the answer, but in any case please cite the owner of the image. (Is that "Keith Morris"? - its not clear) $\endgroup$
– Jamiec ♦
Commented Jul 25, 2016 at 16:07
$\begingroup$ The images shows a free castering nose gear used with differential braking. $\endgroup$
– user3344003
Commented Jul 26, 2016 at 16:11

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