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This question came across my mind when I was thinking about cockpit design vs car design: why don't we have yokes that look like steering wheels?

The first advantage I can think of is more gestures to hold the yoke. You can hold a steering wheel in many ways, e.g. 2 & 10 o'clock, 3 & 9 o'clock, top, bottom, one hand, both hands etc. And one can still pull or push the yoke even if it's circular.

Secondly, in most (if not all) of the yokes, full aileron deflection is achieved when the yoke is rotated approximately 90 degrees. Would it be beneficial if it's 180 degree instead, allowing more fine control?

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    $\begingroup$ As far as I can remember, the only times I use anything like full aileron deflection is when landing or taxiing in a crosswind. Otherwise, control movements are fairly small, probably no more than the arc of the yoke, and done with fingertip pressure. $\endgroup$ – jamesqf Jul 21 '15 at 17:37
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    $\begingroup$ Another good question would be: why do we use steering wheel instead of yokes on cars? $\endgroup$ – Manu H Jul 22 '15 at 8:18
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Short answer: Because you only use one hand on the yoke.

Longer answer: In an airplane, you almost always fly with only one hand on the yoke (or none, as the case may be.) You will be using your other hand for power adjustments, setting flaps, adjusting radios, setting instruments, writing, etc.

In a car, power is adjusted with your feet, so you don't need your second hand for power adjustments and there aren't really any other particularly critical controls that need to be manipulated frequently or precisely. However, in an airplane, you have to be able to precisely control three axes of rotation, not just one like in a car. As such, your feet are needed for yaw control (and differential braking,) which means power must instead be controlled by hand. So, there's no need for the various grip positions that you could use with a wheel because you don't want your second hand on the yoke in the first place.

Additionally, having a 90-degree angle (or nearly so, as the case may be) allows for a better grip than the smooth curve of a steering wheel. You can place 2 or 3 fingers above the horizontal bar and the others below, which prevents your hand from slipping up or down the control wheel, as is possible with a normal car steering wheel.

As far as the second question of whether it would be better to have 180 degrees equal full deflection, that would mean you would either need 2 hands on the yoke in order to command full deflection, which is not good for the reasons already mentioned, or have a weaker grip on the yoke that would allow you to rotate it 180 degrees either direction. If you have a firm grip on the yoke, your wrist will simply not be able to rotate enough to turn it upside down without releasing your grip.

It's also important to note the difference here between what the yoke controls versus what a car steering wheel controls. A car steering wheel directly controls your turn rate. Thus, a car whose steering wheel is in the neutral position will not be turning. In an airplane, however, your current bank angle controls your turn rate. An aileron deflection changes your bank angle. Having the ailerons in the neutral position will not cause you to fly straight forwards, but rather will simply leave your bank angle (and thus your turn rate) at its present value (if we ignore the effects of dihedral and such.) Thus, you don't need as much possible input control range to get precise turn rate control.

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    $\begingroup$ "In a car, (…) there aren't really any other particularly critical controls that need to be manipulated frequently or precisely" - gearbox? ;) $\endgroup$ – el.pescado Jul 21 '15 at 16:33
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    $\begingroup$ @el.pescado: Exactly, at least for those of us who choose to drive cars without assistive technology for the handicapped - AKA automatic transmission. And in my hybrid, I've installed a setup which allows me to use one hand to control the electric assist separately from the accelerator pedal. $\endgroup$ – jamesqf Jul 21 '15 at 17:34
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    $\begingroup$ @el.pescado A gearshift is a discreet control. It doesn't require a great deal of precision. And if you need to shift frequently during sharp turns you're probably doing it wrong. $\endgroup$ – reirab Jul 21 '15 at 17:48
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    $\begingroup$ @reirab, modern gear boxes don't require precision but older gear boxes that predate syncros or even helical cut gears require a great deal attention to shift if you intended to make them last. Not to mention any kind of heal toe (or other double clutch) down (or up) shifting that may require you to keep your hand on the shifter for an extended time. $\endgroup$ – Dave Jul 21 '15 at 18:23
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    $\begingroup$ You obviously don't have many roundabouts where you are, @reirab . On exiting a roundabout onto a high speed multi-lane road you are both going through the gears rapidly, and turning the steering wheel at least over ninety degrees with precision at the same time. But that this is, indeed, rather difficult kind of supports your original answer. $\endgroup$ – Dan Sheppard Jul 22 '15 at 13:18
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We Do! It just has been a while since anyone has built a plane like that.

Many early planes did, notably the curtis biplane comes to mind

enter image description here

As closed cockpits came into be and the modern control set up we see something like a car wheel.

The cockpit of the Reliant SR-6A shows the love and skill that went into the restoration.

enter image description here source

Yokes then evolved to have a more cut down top like the one seen here (in my favorite plane) the Spartan Execuitve This plane was built in the 30's

enter image description here

Even later than that the Ercoupe has a somewhat rounded control wheel. enter image description here

Also of note the Piper Pacer and Cessna 140 had rounded yokes. After that period most of the big makers moved to the yoke we know and love today. Piper would have a closed top yoke on their early Comanches through the early 60's as well. It should also be noted that early planes (wright flyer etc) had stick like controls. I would assume this was to allow the cable to be mounted far from the pivot for torque reasons although Im not sure (this was for sure before trim).

Remember in an airplane its all about weight so trimming it where ever you can is worth it.

In a plane the maximum deflection of a yoke is often no more than 90 degrees so having a full wheel (which allows a hand over hand car style turn) is not necessary.

Orientation is a bit of a concern when flying on instruments but many race cars have center marks on their steering wheels for a similar reason.

For what its worth formula 1 steering wheels see about as much travel as a yoke and are similarly shaped. Some even have more buttons than a cockpit.

enter image description here
source

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    $\begingroup$ And as more and more instruments were added to aircraft, a wheel would just get in the way; you can see and reach over a yoke more easily $\endgroup$ – Pondlife Jul 21 '15 at 14:13
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    $\begingroup$ @Pondlife: Airbus pilots love the folding table in front of them that the switch to side-stick made room for. $\endgroup$ – Jan Hudec Jul 21 '15 at 14:20
  • $\begingroup$ Are aircraft yokes self centering? Or do they stay where you move them to, typically? $\endgroup$ – curious_cat Jul 22 '15 at 1:56
  • $\begingroup$ @curious_cat that is a complex question as there are many factors involved (more than in a car) and there are many types (and system designs) of yokes and sticks but in general no they are not as far as I know at least when talking about the small planes I fly. $\endgroup$ – Dave Jul 22 '15 at 14:06
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With a steering wheel in a car, the driver can judge how far it is rotated without looking at it by at least three means.

In a car, the driver:

  1. can extrapolate visually the curved path he or she is moving along.
  2. usually experiences centripetal force on his or her body.
  3. feels the feedback of the steering assembly. Whether purely mechanical or assisted, steering assemblies are self-centering. If the driver releases the wheel, it will return to neutral.

In a plane, the pilot:

  1. may be relying on instruments and have no outside cues.
  2. may have a false seat-of-the-pants sense of attitude and direction.
  3. should not need to make violent or large steering movements.
  4. has no need to 'steer' around a corner as you do in a car. Once a new attitude is attained, it should remain stable until the pilot corrects it back to normal (this is a rather simplified statement).

The yoke's shape is valuable because it easily informs the pilot of the yoke's rotation with high precision.

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    $\begingroup$ I'm not sure I follow this. Neither 1 or 2 have any relation to whether or not the yoke is centred, and I'm not sure why 4 is relevant either. None of the items in the "in a car" list are relevant to telling whether the wheel is centred. $\endgroup$ – DJClayworth Jul 21 '15 at 16:02
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    $\begingroup$ @DJClayworth the relevancy is that they are cues to whether the wheel is centered. Using 1,2,3 from the car list you can determine if the wheel is centered or not without looking at the wheel, thus a circular wheel whose orientation may be hard to determine is unimportant. In the airplane you don't always have those cues, and if you do they can be misinterpreted, thus having a yoke whose orientation is easily determined is a benefit. $\endgroup$ – casey Jul 21 '15 at 16:10
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    $\begingroup$ In a plane, even in perfect visibility and not on instruments there are no outside cues as to whether the yoke is centred (unless you are actually looking at the control surfaces). $\endgroup$ – DJClayworth Jul 21 '15 at 16:19
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    $\begingroup$ @DJClayworth in perfect visibility you have a horizon to look at. $\endgroup$ – casey Jul 21 '15 at 18:18
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    $\begingroup$ @casey ...which tells you absolutely nothing about whether the yoke is centred or not. $\endgroup$ – DJClayworth Jul 21 '15 at 18:52
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Steering wheels were developed for cars to provide the large amount of leverage necessary to turn the wheels of a car without any power assist.

In planes, you don't need that much leverage (ok maybe in some long-wing aircraft) to control the elevator and ailerons, and the stick is mostly centered, even in turns.

The idiom for fine control of the yoke is to "milk the mouse", and use two, maybe, three fingers so as not to overcontrol.

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    $\begingroup$ Steering wheels were developed for cars to provide the large amount of leverage necessary to turn the wheels of a car without any power assist. Are you sure? In my modern car with power steering, it's still well beyond 360 degrees to turn the wheels all the way to the left or right. $\endgroup$ – Mason Wheeler Jul 21 '15 at 14:44
  • $\begingroup$ I think it would be more correct to say that "steering wheels were of a large diameter to provide leverage before power steering". Power steering has eliminated the need for muscle provided leverage. The only reason trucks & buses have large steering wheels these days is because a small, car-sized one would look weird in the large space of a truck/bus cab. As @MasonWheeler said, it still takes more than a full rotation in most road vehicles to reach full lock, though most cars are only 2.5 turns lock-to-lock. $\endgroup$ – FreeMan Jul 21 '15 at 14:52
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    $\begingroup$ @MasonWheeler And if the power steering (and power brakes, for that matter) fails, such as an engine stall on the freeway, the average adult will have enough power to steer and brake. $\endgroup$ – Adam Davis Jul 21 '15 at 15:10
  • $\begingroup$ I did say power assist. There are various kinds of assist, only one of which is hydraulic. $\endgroup$ – rbp Jul 21 '15 at 17:15
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    $\begingroup$ It should be noted that a larger steering wheel gives you finer control in addition to leverage. (Imagine having a doorknob-sized wheel--it would be very hard to get the precise angle you wanted.) $\endgroup$ – msouth Jul 21 '15 at 18:12

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