Shoguns,

I am helping some folks restore a P-40. This aircraft has an instrument that shows the actual positions of all three landing gears and the position of the flaps. I've included a photo below. AN-5780-1.

This gauge has a pair of coils that run the indicator in either direction for each gear and the flaps. I took it apart and could readily figure out how it was connected. One contact for each direction, hence two pins for each item and a common pin connected to the center of each coil with a red wire. There is no ground connection. The common pin must be (+) to get
the indicators to work at all. It takes about 40ma to get the things to indicate.

The sender is a round wire-wound pot that is continuous. It has 4 unevenly spaced taps, 3 of which are brought out on individual pins and one that is grounded thru the case. The wiper which rotates all the way around is brought out to the forth pin. I think the value is around 1000 ohms. If that were connected to 28v, the current would be ~ 28 ma.

I'm no dummy on this stuff but I'll be damned if I can figure out how it's to be connected. The diagrams I have are for 14v airplanes and make no sense and do not have the letters of the AN connector pins anywhere. If incorrectly hooked up there would be smoke.

Can anyone help? Is this setup used in other warbirds? If so maybe I could find decent documentation for them. Is there a guru on this stuff? The documentation on line (not free)
is of no help.

Thanks for the read. BH

Could it be AC? That would make the values you see make sense

That is called a Selsyn indicator. It is common on several WWII aircraft.

I have no early idea how it is wired, but if you go to;

Air Corps Library you will have your answer. All the drawings for the P-40 are there....

For $5 per month or $50 per year you can have access to hundreds of thousands warbird aircraft drawings.

NO ONE should try to restore a warbird without access to this database. Air Corps provides the library as a community service. It is a big $ loser for them.

Erik Hokuf the lead partner at Air Corps has rebuilt several P-40s and would be an invaluable resource for you....

Confirms my suspicion, Selsyns are AC

It's resistors, not selsyns. So DC. Tried the website--P-40 diagrams are illegible on the section that covers this indicator. The pin arrangements are different and the batteries are shown as 12V, so still looking. Thanks, BH

The gear indicator s on the B25 are called selsyns and we have no AC... Eric at aircorps can help you, and if you are restoring a P40, you need to know aircorps and Fagen fighters...

If you want one or two to experiment on check this guy out on ebay, has more than 10 new surplus condition, $80

http://www.ebay.com/itm/war-bird-desk-a ... Sw9NxTxD-Z

Looks to be the exact same one you have??

Yes, the gauge is the same. bh

Hey Bill,

Is this the info you're looking for?

E

Elliot, Yes, thank you so much!! The pins agree and it actually makes sense!! I can't wait to hook it up and see if it works. Where did you find it? BT wins again! BH

Glad to hear it!

I was poking around the Bay last night and came across the sender which had that drawing as one of the pictures:

https://www.ebay.com/itm/361467161601

E

Wow!! These are the best threads to read.... ever. Nice teamwork and finding the answer from an unlikely source such as eBay.

Faith in humanity restored... at least for tonight.

Kevin

Where is this P-40 project located?

Yuma co

Oh yes, I talked to those guys when they bought the CAF Minnesota Harvard... I hope they are enjoying the HVD. That is a really nice flying airplane.... Exceptionally straight airplane....