Warbird Information Exchange

Did any WWII aircraft have some kind of gauge to measure boost on the superchargers? If so, anyone have any pics?

a few here:

http://www.warbirdsite.com/museumspitfire.html

a little ways down the page.

cheers

greg v.

They pretty much all did.
Rich

I thought so. THanks guys! Now I just need to find one that is for sale.

Here are a couple of styles of gauges:

http://www.warbirdsite.com/lancboost.jpg

http://www.warbirdsite.com/spitfireboost.jpg

_________________
"They done it, they done it, damned if they ain't flew." December 17, 1903

Use and type? Twin, single? Different a/c operated at different Manifold Pressures. IE T-6 vs P-51 had different upper limits.
American, British or other foreign user?
Rich

All aircraft with an internal supercharger, turbo-charger, or a constant speed prop have a boost/manifold pressure guage. The four engined aircraft usually have a dual indicating guage that has two needles labeled 1/2 or 3/4 and a tachometer with dual needles also. I think the B-36 had individual gauges for each engine, not sure on that though. Most of the gauges would have red, yellow, or green markings on them indicating the normal, caution, or danger areas/ranges.

That's why when you hear old flight engineers explaining that if all the needles are pointing in the same direction, everything is OK.

MP is measured in inches of mercury, isn't 'boost' usually measured in PSI?

During WWII the US used manifold gages and the British used boost gages on certain aircraft to provide information to the pilot as a guide to adjusting the supercharger regulator (if the system had means of adjustment) to prevent over-supercharging at low altitudes or loss of power at high altitudes.

Single engine manifold pressure gages in use in 1944 include the Army Type D-2 FSSC Number 88-G-760, 0 to 50 inches of mercury, the Army Type D-9 FSSC Number 88-G-700, 0 to 50 inches of mercury, and the Army Type AN5770-1 D-10 FSSC Number 88-G-773, 0 to 75 inches of mercury.

Dual engine manifold pressure gages in use at the same time include the Army Type AN5770-2 D-11 FSSC Number 88-G-690, 0 to 75 inches of mercury, Army Type D-8 FSSC Number 88-I-1575, 0 to 50 inches of mercury (electric, requires manifold pressure transmitters), Army Type D-8A, 0 to 60 inches of mercury (electric, requires manifold pressure transmitters).

[quote="famvburg"]MP is measured in inches of mercury, isn't 'boost' usually measured in PSI?


Yes to the first question. Second question, I think it's pounds of boost??? I believe boost is the British term for manifold pressure?

The superchager boost pressure is measure in PSIA on the british boost gauge.

Boost is measured either way in inches of mercury or PSI. The Brits used pounds of boost. For example +18lbs would be 66" MAP. To convert PSI to inches of mercury its X2 then +30.

Sparrow

Yes and no. Suppose the max MAP allowed is 48". If the barometric pressure there is 30" that would equal 18" of boost. If you are at Colorado Springs, for example, the barometric pressure might be 25". You are still limited to 48" but if the supercharger is efficient enough to produce 48" MAP, the boost would 23", etc.

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It's what you learn after you think you know it all, that counts.

Django,

I have a few manifold pressure gauges (US) and a Smiths raf boost gauge. They are all mechanical. The needle is resting at 30 (pounds?) in the center of the scale at atmosphere. Any boost pressure will go past 30 and vacuum (as at idle) will show as less than 30. The US stuff is inches and the RAF gauge is pounds.

Thinking about Carburetors and theory, don't we have 14.something pushing down on us all the time? then if you start an internal combustion engine you get vacuum of another 14.? pounds... (or is this all inches of mercury) -almost the "30" on the manifold gauge.

Anyway, you can plug a manifold gauge into a hot rod and get the needle moving all over the scale if you have a blower on it. I just can't figure out how to interpret the reading. I think Sparrowv12 has it correct.

Dave

Yes and no. Suppose the max MAP allowed is 48". If the barometric pressure there is 30" that would equal 18" of boost. If you are at Colorado Springs, for example, the barometric pressure might be 25". You are still limited to 48" but if the supercharger is efficient enough to produce 48" MAP, the boost would 23", etc.


Not exactly----- What I was providing was a simple formula to convert LBS of boost into inches of mercury. I think you're reading way to much into it. Regardless of elevation or anything else, if you want to convert it, the simple way is X2 + 30. If you want to go from MAP to LBS do it backwards.

Sparrow