by Aviation Stack Exchange
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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.
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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.
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.
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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.
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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:
- If a touchscreen fails, you've lost all the controls that were related to it.
- Likewise, if a touchscreen (or portion of) fails then the whole thing has to be replaced rather than just the button
- 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.
- 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.
- 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:
- Cost
- Certification
- Proven reliability
- 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!
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- Spill lots of water on a touch screen and try to use it.
- Close your eyes and use your touch phone or tablet.
- Try the same with knobs and switches.
Also, it is easier to specially and individually protect mechanical actuators against accidental manipulation than making hundreds of dedicated touch screens and protect those.
It makes no sense if each knob/switch needs to be implemented as a dedicated touch screen, with a fallible control computer or some electronics behind it (in addition to the switching logic behind the knob or switch).
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