Vintage Avionics

[Greg Ellis]

So, my 63 C model is finally in the shop getting the GFC 500 autopilot installed.  I had been having problems with altitude reporting.  ATC would tell me that I was 300 feet lower than what my altimeter was telling me when the pressure was set in the Kollsman window.  In IFR that would be an altitude bust.  Anyways, when the plane went in for its autopilot install, they ran tests on all my stuff including the encoder, G5, etc... and it turns out that the altimeter was faulty.  They pulled the altimeter out.  It was made by a company called Square D.  They contacted Square D regarding parts and overhaul.  Square D is still in business.  They make electrical junction boxes and switches, etc... for commercial uses.  They apparently stopped making altimeters in World War II according to the company.  So, I have a pretty old altimeter.  It was put in my airplane about 15 years ago when the previous altimeter failed its IFR test.  I googled it and it is correct that Square D made them from about 1933 through World War II.  There is even one in storage at the Smithsonian.  The only difference is my part number is 671 BK-03.  All the ones I have seen on the internet are 671 BK-10.  So, I am not sure if mine is older or newer than what I have seen on the internet.  Either way, I think this altimeter provided a long life for more than one airplane.  It will now provide a long life as a paper weight on my desk.

[N201MKTurbo]

My instrument guy says the Square D altimeter is one of the finest altimeters ever made. He also said nobody these days knows how to adjust them properly (except him). You can still get parts for them, I'm not sure where you get them. So, it isn't a boat anchor, you just need to find an instrument shop who knows how to fix them.

Apparently they have adjustable pivots for all the wheels. If you don't know how to adjust the pivots, they don't work very well. If you do know how to adjust the pivots, it becomes like the finest swiss watch.

Mooney bought a huge lot of surplus Square D altimeters from WWII and every Mooney got one until they ran out. My J has one. Howard the instrument guru did mine and it has less than 20 feet of error from SL to 25000 feet.

Edited April 4, 2022 by N201MKTurbo

[Greg Ellis]

3 minutes ago, N201MKTurbo said:

My instrument guy says the Square D altimeter is one of the finest altimeters ever made. He also said nobody these days knows how to adjust them properly (except him). You can still get parts for them, I'm not sure where you get them. So, it isn't a boat anchor, you just need to find an instrument shop who knows how to fix them.

Apparently they have adjustable pivots for all the wheels. If you don't know how to adjust the pivots, they don't work very well. If you do know how to adjust the pivots, it becomes like the finest swiss watch.

Thanks for the information.  Every overhaul shop my shop called said they do not work on them.  Like what you said above.

[N201MKTurbo]

3 minutes ago, Greg Ellis said:

Thanks for the information.  Every overhaul shop my shop called said they do not work on them.  Like what you said above.

Try these guys:

https://fliteinstruments.com/

[Greg Ellis]

41 minutes ago, N201MKTurbo said:

Try these guys:

https://fliteinstruments.com/

Thanks.  I just sent them a request for a quote through their website.

[0TreeLemur]

I have a certified altimeter that passed its IFR certification in 2021.  I swapped it out because I found the "Beechcraft" written on the face unworthy of MY Mooney.  Just sitting on my shelf.  Bored.  I'll sell it to you for a tank of fuel (not the red-carpet FBO stuff) because your are a MS member.  If you are interested PM me.