WW2 500 mph airspeed indicator?
- Thread starter OldGeezer
- Start date
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FLYBOYJ
"THE GREAT GAZOO"
No this was common - we discussed this in another thread. The Gauge is showing "indicated air speed," you have to calculate for "true air speed"
From a P-38
From a P-38
I believe the OP is asking about that one specific gauge, its increments of 50mph and its use in an aircraft, ....., 200, 250, 300, 350, 400, 450, 500. It's not typical for a WWII ASI.
P-38 gauge, ....., 200, 250, 300, 400, 500, 600, 700.
FLYBOYJ
"THE GREAT GAZOO"
OK but I don't know about it being "not typical" one would have to see the production call out. I do know that several models of instruments (which are "standard parts") many be applicable to one specific aircraft based on customer. Instrument configuration may vary. If we knew what aircraft this was from?
FLYBOYJ
"THE GREAT GAZOO"
Is this the only pic you have of this? Where did the pic come from?
- Thread starter
- #8
Sorry all, I've been tied up doing unexpected "springtime" repairs on the lawn mower and car. The pictured gauge is one of 2 identical ones sitting side by side on the upper panel of the McDonnell XP-67 aircraft. Both of these gauges were replaced at some point with ones that only went up to 300 instead of 500, which seems to rule them out as airspeed indicators for an aircraft that was required to make 400+. Could the pictured gauge, going from 0 in increments of 50 units, be something else? Or can someone say definitely that it's an airspeed gauge? There's no such gauge anywhere on the main panel, though, so it seems like that's what it has to be...but why 2 of them, side by side? I would think the last thing a pilot would want is a disagreement between gauges about how fast he's going. It's a puzzle and it's making my head hurt...
Since there are two, possibly something to do with the engines, RPM or whatever.
FLYBOYJ
"THE GREAT GAZOO"
I pulled up the photo of the XP-67 cockpit. The only thing I can think of is the "extra" airspeed indicator was installed there for flight test purposes. I also notice those instruments are installed on a panel above the main instrument panel in a position where a gunsight or armament panel would go.
FLYBOYJ
"THE GREAT GAZOO"
It seems in this picture there are 2 pitot tubes, on on each wing. Again, maybe for flight testing purposes?
- Thread starter
- #12
The RPM gauges are down on the main panel, we have a crisp photo of them. I'm still thinking airspeed but I wish I could find a photo of another one like these, with 0 at the lower left and 500 at the lower right, and increments of 50 all the way around.
- Thread starter
- #13
That's what I've been thinking too. Can't help wondering why they thought they'd get 2 different results from LH and RH probes, but they must have had a reason.
GrauGeist
Generalfeldmarschall zur Luftschiff Abteilung
During the testing process, they would look for irregularities (i.e.: working out the bugs), so extensive and detailed instruments would provide such data.
My guess would be looking for the compressability threshold and/or dive performance characteristics?
- Thread starter
- #15
Found the airspeed indicator elsewhere on the panel, a gauge that I previously didn't recognize, so the 2 that I was scratching my head over are for something else. It was the comment about P-38s that got me thinking, and led me back to that other gauge. The amount of technical knowledge in this group is awe-inspiring!
FLYBOYJ
"THE GREAT GAZOO"
As mentioned, I think that whole upper instrument panel was used for flight testing as a gunsight would go there if this aircraft was put into production. I also noticed in the photo that there is no cover for the rear of these instruments. Sunlight would quickly play havoc on hoses and electrical wire so I'm thinking the installation is temporary.
Manifold Pressure, left and right? What a poorly laid out instrument panel! Accident looking for a place to happen. Designed for manufacturer's convenience, not aircrew safety. Maybe they just didn't have a two needle MAP gauge handy when they were hooking up this "test" panel. Can't believe they would go into production with a hodge podge panel like that.
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It was the XP-67, not production. The upper (temporary) instrument panel was for Flight Test. The typical two needle gauges are in the lower panel.
Orange Logic - McDonnell XP-67 Bat Cockpit
FLYBOYJ
"THE GREAT GAZOO"
No pics in your link
If you've ever done multi engine training, you'd probably have an idea. A plane with a single pitot tube static port system usually has significant airspeed errors, since single engine flight, especially down near VMC (where it's most critical) is an almost continuous sideslip. If you have two pitot tubes with correspondingly located static ports, and mounted at slightly converging angles, all feeding a single set of ALT, ASI, and VSI, the errors will tend to cancel or average, giving you a "poor man's Air Data Computer".
