Why are traditional knobs not replaced by touchscreens in cockpits?

Looking at this picture of an A380 cockpit I see that there are still a lot of traditional switches (meaning manual click on and off or knobs). Being technology so advanced in these days, why is it that traditional switches and knobs are used instead of having a couple of touch screens on which the various controls are placed?

Wouldn't this make it more economic as there would be savings on material and wiring? They could also be less susceptible to failures as traditional switches and knobs still rely on mechanical actions.

Another advantage I could think of is that every pilot could customise positioning of controls and switches based on his/her way of piloting. This could then be reset to a default state every time a new pilot takes over.

• Just look at the big mess all home equipment is now. You never know how to use it without opening the manual, or you keep clicking 23 times like a mentally ill just to change from summer time to winter time, and you are lucky if you manage to stop clicking before being too far :( – mins Nov 6 '15 at 13:04
• As for any electrical systems, you should think of what happen in case of (partial or total) electrical failure. Also note that for home devices, keyboard are easier and faster to use than touch screen for many usages (e.g. post on this website) – Manu H Nov 6 '15 at 13:27
• @ToddWilcox: But in a B737, at least when you want to change the bank angle limit you don't have to remember that it buried in the configuration -> current flight -> FMS ->other -> angles -> bank -> max option. – mins Nov 6 '15 at 14:24
• You must look at what your hand when using a touch screen in order to get the correct spot. With a mechanical control, muscle memory will get your hand to the right spot, and the control shape (for major controls), will confirm that you're there, all without ever looking in the cockpit. For example, I can find the power button on the TV remote without looking at all, while using my phone as a remote for Kodi requires that I look at my phone - if I drag my hand looking for the pause button, I'll hit all sorts of other stuff. – FreeMan Nov 6 '15 at 17:44
• "They could also be less susceptible to failures as traditional switches and knobs still rely on mechanical actions." As someone who designs devices using both touchscreens and physical buttons, all I can say about this is no. – reirab Nov 6 '15 at 17:49

Adding a pilot's perspective to what others have said:

Look at the switches and knobs in an airplane up close some time. You'll notice that nearly all of them have different textures,heights,sizes or shapes. That's intentional. Pilots train and train and train and train on checklists, especially the emergency ones. Muscle memory is a big part of quickly and correctly executing an emergency checklist.

As an example, flap levers/switches normally have a cap or top that is flat and parallel to the wings. It's easy to identify solely by touch.

Checklist item: "flaps up" Action: Hand to flap lever (automatic after doing it a hundred times in training), verify feel of lever, move, look to verify

Without the tactile element, every motion would have to be verified by looking before it's made. With the tactile element, the movement can be made and then verified visually while the hand is moving to the next item. In an emergency, every second counts and the savings from tactile + verify matters.

Beyond emergency procedures, they're simply safer. The plane I fly the most has a touch screen display and several non touch devices. In turbulence, the touch screen is basically useless. But, the important devices all have buttons and knobs. I can be banging my head on the ceiling (literally) and still adjust the auto-pilot or radio. In that kind of turbulence, the touch screen device is completely useless.

• This. 100% exactly! Try tuning the touch-screen radio in your car on a bumpy road. Now try it with a knob. No contest! – FreeMan Nov 6 '15 at 17:05
• Ha, I just made the same comment above before scrolling down and reading this answer. I think the turbulence answer should be the #1 canonical answer; the rest of the answers here are all true, but the human factors seem like the primary reason physical controls persist. – egid Nov 6 '15 at 22:46
• @egid perhaps I'm just interpreting it differently, but I'd consider turbulence an environmental factor, not a human factor (to me, "human factor" = "human error"). While humans are involved in the error that'd be introduced by turbulence, it's not directly their fault. – Doktor J Nov 6 '15 at 23:34
• @DoktorJ Well, Human Factors as a concept is the study of the interaction between man & machine. Turbulence is environmental, but it affects how effective we are at manipulating the controls and is certainly something that guides cockpit/flight-deck design. – egid Nov 6 '15 at 23:36
• Welcome Sean, nice first post! Hope to see more of those. – DeltaLima Nov 9 '15 at 21:54

• Flicking a switch gives clear haptic and audible feedback. Compare that to a touchscreen where you can never be sure if your intention has been interpreted correctly. This might not seem to matter much, but if you need to throw 20 switches in a hurry, the mechanical solution is head and shoulders above anything with a touch input.
• Mechanical switches can be operated with gloves on. Touchscreens generally cannot.
• If the computer driving the touchscreen crashes, you are out of control. Mechanical switches don't have this failure mode.
• Mechanical switches are far easier to debug than touchscreens. You can make sure if the switch works by using a screwdriver and a voltmeter. And some knowledge of the routing, admittedly.

@Greg Taylor and @Lightsider are correct: Inadvertently flicking a mechanical switch is so much harder than one on a touchscreen, especially if it has a cage to protect it from movements in an off direction.

Toggle switch with cage (picture source)

• I'd add one small point, that inadvertently hitting a switch with a touchscreen would be far more likely. Brushing another area of the screen with a pinky or knuckle could change something you didn't intend. A physical switch doesn't change from such a light touch. – Greg Taylor Nov 6 '15 at 13:17
• @GregTaylor: Right, and for that reason important switches have cages around them so they need to be toggled by a movement in the right direction. – Peter Kämpf Nov 6 '15 at 14:03
• As anyone who has driven a car for several years knows, once you are familiar enough with physical controls, you can keep your eyes on the road (or skies, or display, or altimeter, or whatever) and 100% use touch to find, check the current setting of, and change the setting of a physical control. Not so with a touchscreen control. – Todd Wilcox Nov 6 '15 at 14:23
• I think the point @ToddWilcox makes deserves more visibility than a comment affords. I know it's a big reason for me to prefer physical controls in high-focus environments, even if those physical controls in the end change some setting in an electronic system (like the radio's volume level in my car, which uses a continually rotating knob to adjust the volume but provides clear tactile feedback that I am (a) touching the right control and (b) operating said control). – user Nov 6 '15 at 15:37
• Don't forget turbulence. Have fun tapping in a frequency on a touchscreen in mod tb; I finished a minute ago with knobs. Just imagine driving on a washboard or gravel road, trying to use a touchscreen that's an arm's length in front of you. – egid Nov 6 '15 at 22:45

Mechanical switches gives a better visual inspection than digital touch screens. For a pilot surrounded with so many switches, just a visual glance would be enough to find the position of the control.

• In addition to the vsual feedback, touching a knob without looking at it also provides a feedback on its position (I agree this is not enough to be sure the knob is in the correct position, but it is an information that can trigger some check process) – Manu H Nov 6 '15 at 14:23
• As an additional point, when using a touchscreen your hand is blocking the view of it. You can't see the actual button that you are pushing, and you can't grab a switch, verify that it is correct, and then move it. – Adam Nov 6 '15 at 14:34
• I wouldn't agree entirely with visual inspection. With a touchscreen, a good interaction designer can make visual inspection much easier. Besides, only the buttons which need to be shown at a time can be shown, thus reducing a LOT of visual clutter. – Nav Nov 7 '15 at 7:55
• @Nav "only the buttons which need to be shown at a time can be shown" You mean, "only the buttons the interface designer assumed you'd need to be shown at a time can be shown." – David Richerby Nov 9 '15 at 8:53
• @Nav "reducing a LOT of visual clutter" Is visual clutter in the cockpit a problem for properly trained pilots? I'll grant you it can be intimidating at first, but once you know the control layout, I tend to find "cluttered" panels easier to use in many situations because the control is always right there, in the same spot every time, no matter what else is going on. – user Nov 9 '15 at 15:16

Beyond the obvious aviation reasons of cost and so on, I can think of a few reasons why I'd not want an over reliance on touchscreens in the cockpit:

1. If a touchscreen fails, you've lost all the controls that were related to it.
2. Likewise, if a touchscreen (or portion of) fails then the whole thing has to be replaced rather than just the button
3. Feedback - phones and similar devices offer things like haptic feedback to register a positive touch. I can't imagine that being implemented and working well in a fixed monitor. Pressing a button provides a positive reinforcement that you did press the button.
4. Using touch-screens is hard if they're not still - it's far easier to press a physical button, without pressing an adjacent button, than it is to press an area on a screen without accidentally glancing another area.
5. Some controls are designed to be easy to operate, while being hard to do accidentally - for example flaps, gears, mixture etc. All of these require some positive force.

With that said - you've posted some advantages and, in honesty, I suspect it'll all happen one day. So, for that reason, in the meantime I give you the stock answer to any "Why isn't..." aviation question:

1. Cost
2. Certification
3. Proven reliability
4. Market demand

Unless pilots and airliners are crying out for it, and a manufacturers think it will make the difference between whether they buy a particular aircraft or not, they simply aren't going to spend the time and money necessary to make it a reality.

Additionally, it'll almost certainly come in slowly. It's one thing to add some touch functionality to a flight computer but I wouldn't be expecting flap and gear levers to be touch sensitive anytime soon!

• For new designs, I'd actually guess that the touch screen solution would cost less, especially since modern glass cockpits already have plenty touchscreens in place (and a lot of controls already have been assimilated into these.) Reasons 3-5 have a lot more to do with why lots of other switches still exist, though, imo. (And reason 6: having a touch screen control for the main power bus doesn't work out well, since it becomes very hard to turn it back on without power...) – reirab Nov 6 '15 at 17:56
• "Proven reliability" A big deal in aviation. – T.J. Crowder Nov 6 '15 at 22:39
• @reirab if you see a screen in a cockpit, don't jump to the conclusion that it is a touch screen. The downsides of a touch control do not carry over to displays so you might be noticing that instead of physical dials, a cockpit has multi-function displays. I would bet that what controls the display are traditional knobs / levers / buttons though. – Kelly S. French Jan 3 '18 at 17:56
• @KellyS.French Yes, sorry, you're correct. That was a typo on my part. I meant to say "especially since modern glass cockpits already have plenty of screens in place." The point was that adding a touch-screen digitizer is not expensive (especially not relative to the cost of new aircraft.) Why touch screens aren't used for most of the controls has more to do with the other reasons listed here. – reirab Jan 3 '18 at 19:05

Touchscreen flight displays are already under production and the first commercial aircraft with touch screen primary flight displays as standard equipment to receive FAA certification is the Beechcraft King Air 250 turboprop equipped with Rockwell Collins Pro Line Fusion avionics.

There are some issues with touchscreen, such as,

...special security procedures are needed to avoid unintentional taps or movements that could jeopardise flight safety, especially during turbulence.

However, touch screens for aircraft are under intense development by almost all of the major avionics manufacturers and should be available for large aircraft by the end of the decade.

As an aside, the F-35 is the first combat aircraft to use a touch screen.

• Very interesting. Would be nice to know what solutions are being explored to avoid unintentional taps. – Fabrizio Mazzoni Nov 6 '15 at 12:58
• @FabrizioMazzoni: I've heard that taps are ignored, and large directional swipes (think iPhone's "Slide to Unlock") are the safe way to design for touch-screen controls in the cockpit. – Jacob Krall Nov 6 '15 at 14:14

"Wouldn't this make it more economic as there would be savings on material and wiring?"

Not necessarily, because the days of "one wire per function" are long over. Automotive has pushed that forward, and aerospace is following. Modern systems tend to be networked. This actually gives better reliability for less wiring, because it's easier to duplicate individual network cables than to duplicate a 6"-wide bundle of wires carrying the same information. Superficially the cockpit may still have 30-year-old switches and dials, but expecting 30-year-old wiring under the surface is generally incorrect.

"They could also be less susceptible to failures as traditional switches and knobs still rely on mechanical actions."

So do touchscreens to some extent. As for numbers of failures, how robust is your phone screen to minor impacts, compared to the switches on your car dash?

• "Automotive has pushed that forward, and aerospace os following." Really? Can-bus is older than Arinc 429? – Koyovis Jun 1 '17 at 20:25

Ive had touch devices misread my intentions many factors of factors times more often than mechanical switches. Furthermore you can operate mechanically arranged interfaces without looking, ie. by feel. In fact, having an interface that responds when you touch it is not at all what you want to happen when safety is a major concern.

When my hands are swatting, or there is dust in the air etc I find that the touch screen on my phone does not always work. Also in turbulence, how well can someone touch a flat smooth screen in the correct location, but a physical 3d switch can still be used. Also what if the operator has to wrap his/her hand in a cloth due to it bleeding?

Do you wish your life to depend on the above?

However on the ground, a touch screen make sense for reading of event logs etc by a maintenance person.

• If the pilot's bleeding, I'm not sure I want him or her anywhere near the controls, thank you very much. – Lightness Races in Orbit Nov 9 '15 at 23:55
• @LightnessRacesinOrbit Better a bleeding pilot than no pilot at all – Dr. belisarius Nov 10 '15 at 0:42
• @belisariushassettled: If your A380 only has one pilot then you have bigger problems. – Lightness Races in Orbit Nov 10 '15 at 0:50
• @LightnessRacesinOrbit I know. But I still prefer that only bleeding pilot in the cockpit rather than away from it! :) – Dr. belisarius Nov 10 '15 at 2:01

The A380's maiden flight was in 2005.

iPhone's release was in 2008.

Planes development cycles are drastically longer than phones, and require very reliable materials.

We just didn't had readily available large capacitive touch screen when engineers started designing the A380's cockpit.

• But we did have resistive touchscreens, and the biggest advantage of capacitive is multi-touch, which is a whole extra layer of complexity. – Chris H Nov 6 '15 at 16:53
• Indeed. But Resistive touch screen are drastically less user friendly, precise , and convenient to use. – Antzi Nov 6 '15 at 17:15
• @ChrisH Capacitive touchscreens are truly touchscreens. Resistive touchscreens typically required some force: you had to actually press into the screen. Though that might actually be an advantage to prevent accidental touches... but it's also generally less accurate with a finger, and easier to accidentally break (thin plastic vs thick plastic/glass). – Bob Nov 6 '15 at 20:19
• Nintendo DS are portable devices that use a resistive touchscreen along with a stylus. The device has very good response to touch, despite being resisitive. Also, I remember late-generation PDAs that had very good resisitive touchscreens too. – sleblanc Nov 7 '15 at 6:11
• @Bob, I think you simply dealt with devices with low-quality resistive touchscreens. – sleblanc Nov 7 '15 at 6:11

Don't try at home experiment: Spill lots of water on a touch screen and try to use it.