3-position toggle switch question

[alpinelakespilot2000]

I'm trying to consolidate my switches a little and can't find I switch that I think exists. I'm looking for a 3-position toggle switch with off(bottom)-on(middle)-momentary(top).

Bob Nuckoll's describes this type of switch as being appropriate for a combination boost pump/primer switch with the boost being the on and primer being the momentary. As best I can tell, Spruce only has similar 3-position switches with off in the middle. However, since all of my other switches are off when all the way down, I'd like to remain consistent with a boost pump/primer switch. Any recommended sources?

If I did find such a switch, what would be the implications of accidentally (and only VERY briefly) engaging the momentary primer switch during a go-around or in preparation for landing when I really only intended to engage the boost pump?

Thanks for your thoughts/sources.

[Mark Burns]

Originally Posted by alpinelakespilot2000

I'm trying to consolidate my switches a little and can't find I switch that I think exists. I'm looking for a 3-position toggle switch with off(bottom)-on(middle)-momentary(top).

Thanks for your thoughts/sources.

B&C Specialty Products has them.
It's a double pole but should do what you want it to.
Part Number S700-2-51 (Should be -50 see posts below)

Just realized you'll need the double pole to control the boost pump and the primer valve.

http://www.bandc.biz/cgi-bin/ez-cata...8218#s700-2-51

Mark

[alpinelakespilot2000]

Originally Posted by alpinelakespilot2000

If I did find such a switch, what would be the implications of accidentally (and only VERY briefly) engaging the momentary primer switch during a go-around or in preparation for landing when I really only intended to engage the boost pump?

Thanks a lot Mark. It looks like I'll need to get friendly with yet another supplier! I can do that!

Anyone have any ideas on the other question? Is there any problem with inadvertantly (and briefly) engaging the primer when the intent is to ensure that the boost pump is on?

[gmcjetpilot]

Originally Posted by alpinelakespilot2000

If I did find such a switch, what would be the implications of accidentally (and only VERY briefly) engaging the momentary primer switch during a go-around or in preparation for landing when I really only intended to engage the boost pump? Thanks for your thoughts/sources.

Prime in a carb engine pumps RAW fuel into the intake ports directly and the engine will be super-duper rich (technical term ) and guess it would stumble a little, at worse flood with partial loss of power. If you got ridiculous and held I guess it could shut the engine down and make restart hard.

Yes every RV is different but you don't have to try and make it real different. I'm sure some one will say they have this switch and never mess up, no doubt. The obvious solution is a simple toggle and a separate prime button in a shield.

It would nice to have a lock toggle that requires you to pull-out on the lever to get into the last or prime position. Some where their is an expensive Mil Spec locking toggle with an ON-OFF-MOM (pull) momentary.

Special switch-ology and human factors is always good to think about, what would another pilot do. It's not like RV's require type ratings, extensive ground and flight training and recurrence to fly. I won't show the picture, but there's a RV with like 15-20 switches for all kinds for things I never heard of. Bless all those fancy switches and wiring schemes, but it makes me wounder will you remember all the switch-ology when you need to. I know some factory planes have some thing like this. One is the 400 series Cessna with a high low boost in one switch. There have a been a few accidents using the wrong boost which can flood the engine.

Love the primer switch in the fuel pump switch idea. It might be cool to make a little spring loaded latch/stop you have to flip to get into the momentary/prime. Probably a little two paranoid or over worrying but it could happen.

[Rick_A]

I'm using this off-on-mom switch for Fuel Pump and Fuel Purge. The Purge will control a primer solenoid to route hot under cowl fuel back to the tank. I have a "pump on" idiot light to tell me when the switch is on in the Fuel Pump position.

The TL switches cost more than the B&C switches.

[JonathanCook]

Hi Steve,


I am also thinking of using a switch like you are using for boost pump and prime. Bob Nuckoll's book does not describe the 700-2-51 switch, therefore I am using the 700-2-50 switch. I know that it seams trivial, but I can not be sure how the "51" switch works with out having a schematic. My assumption, is that the "51" switch will opperate as:

1. off (down)
2. Boost pump on, prime off (middle)
3. Boost Pump off, prime on (top)

Bob Nuckoll's boost and prime method will NOT work exactly as described with the 700-2-51 switch, because the boost pump will be OFF when you prime.

Again, I am can not confirm the 700-2-51 function with out the schematic, but I know that the 700-2-50 will work as described in Bob's Nuckoll's book.

[Mark Burns]

Originally Posted by JonathanCook

Hi Steve,


I am also thinking of using a switch like you are using for boost pump and prime. Bob Nuckoll's book does not describe the 700-2-51 switch, therefore I am using the 700-2-50 switch. I know that it seams trivial, but I can not be sure how the "51" switch works with out having a schematic. My assumption, is that the "51" switch will opperate as:

1. off (down)
2. Boost pump on, prime off (middle)
3. Boost Pump off, prime on (top)

Bob Nuckoll's boost and prime method will NOT work exactly as described with the 700-2-51 switch, because the boost pump will be OFF when you prime.

Again, I am can not confirm the 700-2-51 function with out the schematic, but I know that the 700-2-50 will work as described in Bob's Nuckoll's book.

Jonathon,
I was going by the description of the -51 switch. (ON)-ON-OFF
I was confused because the description of the -50 is (ON)-ON-ON
I was looking for an OFF when down

The schematic of the -50 shows you can have an OFF (down) for both the boost pump and primer if you don't use terminals #3 & 6. Duh

http://www.aeroelectric.com/articles/switches.pdf

So with the -50 it would be terminals 2 and 1 to control the boost pump and terminals 5 & 4 to control the primer.
Terminal 1 goes to the boost pump and terminal 4 goes to the primer.

Is that how you see it?

Mark

[alpinelakespilot2000]

Thanks for the clarifications on the switch, Jonathan and Mark. I too was thrown off by the on-on-(on) description on the B&C website. Whatever the number, I'd really like to use it, because it makes a lot of sense, given that the boost pump has to be on to use the primer. At the same time, however, George's comments above make a lot of sense as well. If accidently engaging the primer might cause a safety of flight issue, it's probably not worth it just to be able to clean up the panel a little.

[bsacks05]

Steve,
I did exactly as recommended by lectric Bob with the fuel pump/primer switch, also ordered all my switches and odds and ends from B&C.
Once, while in the pattern, I accidently hit the momentary prime and the engine roughened up a bit which got my attention instantly. (I am priming two cylinders) My initial thought was, "well now I know the primer works" because I neglected to do a flow check of the primer system up to that point. Had I kept the prime on for a few seconds, the engine probably would have stalled but it all took place in less then half a second and I have never done that again. This was in the early hours of my RV before I had all my switchology down. I also put color coded covers on the toggles since then.
Otherwise, I have been very pleased with it and all the other ideas I used from Aeroelectric Connection.

[alpinelakespilot2000]

Thanks for the firsthand report, Bruce. It is very helpful.