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Cabin Pressure Altimeter can anyone ID?

Started by velo-ct , Feb 27 2017 08:11 PM

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#1 velo-ct

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Posted 27 February 2017 - 08:11 PM

Hello I am hoping the experts here will recognize this. I am stumped trying to find out what military aircraft this cabin altimeter came from.   I bought it because I had never seen one go beyond 50,000 feet in a jet from the early years.   Now I can only think of 2 candidates that if they lost cabin pressurization would need to show up 80K but I have not seen this so far in any U2 or SR71 cockpits.   Can anyone tell me what this came out of?  the first is natural light.  The second picture shows the bright orange color under a UV light so I assume it is radium paint.

 

Thanks in advance for your help.

 

Captures.JPG

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Edited by velo-ct, 27 February 2017 - 08:13 PM.


#2 northcoastaero

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Posted 27 February 2017 - 08:47 PM

Are there any markings such as part numbers, contract numbers, manufacturer, etc. elsewhere on the altimeter?
These may help for a proper ID.

#3 velo-ct

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Posted 27 February 2017 - 09:15 PM

Excellent question but it is surprisingly very sterile with only the manufacturer and some cryptic temporary markings but no model number anywhere.  Here is a picture of the backside.

 

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#4 velo-ct

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Posted 28 February 2017 - 01:19 AM

Is it possible that the real gauges may have been 80,000 ft units in the SR71?

 

One could assume that if you did not want anyone to be sure how high your plane flew then a one-handed 80,000 ft cabin pressure altimeter would have been a dead giveaway.  For pictures and displays then it would have been desirable to swap in the standard unit displaying 50,000 ft.   The main three handed altimeter would not need to be swapped out because the upper limit display is always 99,999.

 

That could explain why all the display cockpits in the museums look like this one.  The manuals are declassified now so we know they pressurized the cabin to 26,000 ft but it would make sense to have a gauge that was capable of displaying a full depressurization situation.  

 

Just a wild theory....

 

 

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#5 Bluehawk

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Posted 28 February 2017 - 05:53 AM

WAG, because of the 80k reading... might this have been used in some sort of training simulator or chamber, and not in an aircraft?

 

As velo-ct wrote, not a whole lot of airplanes can reach 80k ft.



#6 2BanAviator

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Posted 06 March 2017 - 07:27 PM

Per the 1959 Flight Manual, the U-2 Cabin Pressure System monitored altitude pressure in both the cockpit and the equipment bay.  The pilot would select which area to monitor by flipping a console switch, and the Altitude Pressure Indicator (marked Cabin Pressure) would display for that area.  I haven't seen any illustrations of the indicator installed, but one could speculate that it would need to be able to display up to 70K in the event of a catastrophic pressurization failure in the equipment bay. That doesn't explain the 80K upper limit of the scale, tho. 



#7 velo-ct

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Posted 08 March 2017 - 10:30 PM

Thanks for the U-2 info 2Ban...  Is the manual linked online?  I found the SR-71 manual and it specifically refers to a 50K  cabin altimeter but who knows if it was not edited.  As for the U-2 perhaps they were more concerned about it since it was the first to get up there and the 80k would still make sense, my corvette speedo goes to 200mph but alas,  it won't quite reach it!



#8 Bluehawk

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Posted 09 March 2017 - 02:23 AM

U-2 then, most likely... which, does make sense.



#9 velo-ct

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Posted 15 March 2017 - 12:49 AM

Update:   

 

The museum of flight research team was unable to discover the origins of the unit.  They even wrote to Aerosonic and they didn't know what it was for either.  

 

In the meantime I bought a standard 50k unit for comparison and it is the same size.

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Edited by velo-ct, 15 March 2017 - 12:49 AM.



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