Another XP-67 instrument question

[OldGeezer]

6 instruments on the XP-67 were mounted on a separate panel on top of the main panel. The ones we can identify are the altimeter, airspeed indicator, and two engine torquemeters. The gauges in the middle is a puzzle. The only marking on one is a big "F" which would hint that it's an outside air temperature gauge, but neither the Navy nor the Army instrument manuals show any such gauges reading Fahrenheit, they're all Centigrade gauges. So it may not have anything to do with temperature. The aircraft's S-23A specification calls out, in addition to thermometers (plural - Types A-19 and G-9), a single ammeter (Type D-2) and a voltmeter (Type B-1) "if required." There's no sign of either one unless that's what this gauge is, and it's hard to believe that there wouldn't be something on the panel to monitor the state of the electrical system. So our guess is that this gauge is one of those, but which? The "F" sure doesn't help with that.

Then there's the gauge next to it. It looks similar to the oil and coolant temperature gauges on the main panel, and we thought it was probably a carb temperature gauge, but we're not sure about that. The scale looks odd somehow. It's too blurry to read, but the number of digits doesn't seem to line up with similar gauges we know about.

We haven't been able to find photos of any of these things by looking up their various Type numbers; anyone here have information to guide us? It's absolutely amazing what technical knowledge this group has!

 

[cvairwerks]

I found a photo of the forward cockpit without the additional panel. Another photo shows what appears to be a selector switch for Al/Cr type thermocouples, I suspect that auxiliary panel was only installed as needed for flight test, and reconfigured as testing requirements did also.
We used to install all sorts of stuff for as few as a single flight or engine run when I was in Flight Test Engineering, for one of the big 4, at the time.

 

[OldGeezer]

I found a photo of the forward cockpit without the additional panel. Another photo shows what appears to be a selector switch for Al/Cr type thermocouples, I suspect that auxiliary panel was only installed as needed for flight test, and reconfigured as testing requirements did also.
We used to install all sorts of stuff for as few as a single flight or engine run when I was in Flight Test Engineering, for one of the big 4, at the time.

It actually evolved over the program's short life. The main panel's gauges stayed about the same, only one or two were changed, and it never had an altimeter or airspeed indicator, those were always in that upper panel. The 2 gauges on the far right of that upper panel were swapped out for ones with different scales but apparently the same function. The one in the middle (the first photo in my post) was moved to the left and up over the 2 on that side to make room for some odd piece of gear that we haven't been able to identify, a long tubular thing with a big knob on the "inside" end that we thought was some kind of camera but it definitely didn't have a lens at either end, hence the mystery there. So you're absolutely right, the panels evolved, the upper one in particular. It's just that we're not sure what those 2 gauges in particular were for.

 

[CATCH 22]

The double gauge on the right reminds me of a carburetor air temperature gauge in twin-engine bombers I've seen (B-25).

This type of gauge has 2 "layers" (back and top) and I think it looks like it in your photo as well.
Just and educated guess!
Cheers!

 

[OldGeezer]

The double gauge on the right reminds me of a carburetor air temperature gauge in twin-engine bombers I've seen (B-25).
View attachment 622769
This type of gauge has 2 "layers" (back and top) and I think it looks like it in your photo as well.
Just and educated guess!
Cheers!

I agree. Although most of the ones I've seen have met at "0" in the middle of both scales, while the one in XP-67 doesn't. I know a few that were otherwise, like this one, so I think we're going to declare victory on that one: