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Switchology Conventions? A different Paradigm ?

Laird

Laird

Well Known Member
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Hi all,

This mornings random musings on instrument panel switchology....

Most RV's (and other types) I've seen have the switches grouped by function, i.e. mags together, radios, lights together. That's the way I did my RV-6 many many moons ago.

Downside to that I see is that you have to think a bit while your going thru your checklist going from one switch to the next.

What if, and I don't think I've seen this done, you have the switches lined up by process, or the check list???

Example would be, from left to right, Master, EFIS, Boost Pump, L/H Mag, Starter, R/H Mag, Strobes, Wig Wag, Nav Lights, etc.

I'm thinking that it might get easier to see each step of the checklist has been completed on start up moving left to right. I think switch grouping might be more helpful in an emergency, but hopefully that should be a rare occurrence.

Have you seen this done before?

Thoughts?
 
Laird said:
Downside to that I see is that you have to think a bit while your going thru your checklist going from one switch to the next.
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Needs to be as intuitive as possible; less for the start check list and more for the unexpected, oh sh!ts! Look at your own words above then apply/add a multiplier for that to a high stress situation. My $0.02.
 
Freemasm is on to something. One good way of grouping switches is by when they are actuated together. Some of these examples are not 100% standard, but: fuel pump and flaps and strobes; pitot heat near strobes because going into clouds, strobes off, pitot heat on; and put switches that you might need in a hurry (fuel pump) at the end of the row so you can find them by position. A Boeing guideline is to never use color by itself to convey meaning, i.e., switch function. Lastly, develop your checklist and switch layout at the same time. Don't forget flow. And for your use cases, consider the functions that are time critical when you lay things out. There's nothing time critical about starting the engine, so that use case is very low priority. There's lots to think about!
 
Laird said:
Hi all,

This mornings random musings on instrument panel switchology....

Most RV's (and other types) I've seen have the switches grouped by function, i.e. mags together, radios, lights together. That's the way I did my RV-6 many many moons ago.

Downside to that I see is that you have to think a bit while your going thru your checklist going from one switch to the next.

What if, and I don't think I've seen this done, you have the switches lined up by process, or the check list???

Example would be, from left to right, Master, EFIS, Boost Pump, L/H Mag, Starter, R/H Mag, Strobes, Wig Wag, Nav Lights, etc.

I'm thinking that it might get easier to see each step of the checklist has been completed on start up moving left to right. I think switch grouping might be more helpful in an emergency, but hopefully that should be a rare occurrence.

Have you seen this done before?

Thoughts?
Click to expand...
Set mine up like that, fuel pump, avionics, autopilot, pitot on left, all lights on right
 
There is an argument for arranging lighting switches specifically in order of typical use, but otherwise I agree with those who've pointed out the merits of grouping controls by function and importance.
 
Human factors dictates a lot of these conventions. Switches that have priority in an emergency (ex. boost pump) really should be put where you can find them without looking, like at the end of a row. Likewise, flight critical switches should be located where it's unlikely for them to be shut off by mistake.

The first post in this thread has a classic example of a crisis waiting to happen; The boost pump switch right next to the EFIS switch. It would be really easy to launch into IMC, and right after takeoff think you're turning off the boost pump but accidentally power down your EFIS.


This isn't just theory. That exact thing has happened and been discussed here on VAF.
 
I always shake my head when I see the fuel pump next to an avionics master. It’s astonishingly common.

I have all my masters/mags up on the roof. Touch them once on startup. Fiddle with them for mag checks once.

Flaps and Fuel pump next to the throttle quadrant. Use them mostly at the same phases of flight. Can reach with hand on throttle.

All the lights are grouped together on the center console. They’re touched rarely. Off in IMC. I like the idea of putting the pitot heat next to them perhaps. I’m thinking of rationalizing them down to two. Strobes/Nav and landing/taxi. The GAD auto wig wag has worked exactly as expected with airspeed. So it’s on - or off in IMC/Rain.

I have a third switch panel on the RHS up high that has pitot heat / defrost fan and dimmers. That panel is very rarely touched.

The main panel has no switches on it at all. PFD/MFD/Navigator. That’s it. I like it like that. I had toggles under my touch efis in my RV7. They are in a bad place for hands on the screen in turbulence.

I think the prevalence of a big row of switches along the panel base was born out of simplified wiring for plug and play panels. Then it got copied.

Each to their own but for me less is more.
 
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Desert Rat said:
It would be really easy to launch into IMC, and right after takeoff think you're turning off the boost pump but accidentally power down your EFIS.
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Indeed. And don’t forget the worst offender: the unguarded starter switch on the stick grip. One of those almost killed me. The people who defend those switches probably wish it had finished the job. 🤣
 
Dugaru said:
Indeed. And don’t forget the worst offender: the unguarded starter switch on the stick grip. One of those almost killed me. The people who defend those switches probably wish it had finished the job. 🤣
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I incorporated many ... switchguards, locking toggle switches and even a swithguarded "starter armed" switch to protect my stick mounted starter button. Complexity? Maybe, but I like the stick and starter button in one hand, and engine controls in the other when starting a taildragger. Emergency systems (starter armed, backup electrical power) get switchguards. Safety of flight systems (EFIS, ignitions) get locking toggle switches. All others (lights, boost pump, pitot heat, etc) get regular toggle switches with colored hats. The only push buttons I use are a remote comm radio flip-flop, the protected starter switch and autopilot disconnect. HF and HMI are too often overlooked in our little airplanes.
 
Dugaru said:
Indeed. And don’t forget the worst offender: the unguarded starter switch on the stick grip. One of those almost killed me. The people who defend those switches probably wish it had finished the job. 🤣
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Ive got a starter switch on the panel but I've also got a parallel circuit with a button on the stick. 100% I would never wire up something like that which was always hot. Mine's got a guarded arming switch on the panel above the radio stack and a "starter armed" CAS message. I find that I'm not using it as much as I thought I would, so I may take it out at some point.
 
Dugaru said:
That seems like a good way to do it. Basically removes any real risk of inadvertent head slicing. 😃
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any head slicing I do will will be 100% advertent...is that the opposite of inadvertent?

Kidding aside, When I put the big engine in the little RV7, I had no idea how much tendency it might have to nose over if a flooded engine start resulted in a high rpm oopsie right after cranking. I know that has happened to at least one RV8, although I think he also had the flaps down which didn't help.

Stick back with one hand, starter with one hand, mixture with one hand seemed like I was going to need to grow a 3rd hand. Turns out, people were right when they told me the ergonomics of the RV7 are good enough that I don't have to be a contortionist to hold the stick aft between my knees and still have my feet on the brakes.

I believe the way I have it wired up is no more dangerous than a panel mounted push button starter, but I doubt if I'd do it again.
 
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