View Full Version : Pressure gauges (altimeter, vario, IAS) interfacing

10-17-2013, 07:30 AM
This is our Czech DC-9 project video showing interfacing of original altimeters. Due to problems with mobile phone we lost other videos but you can believe me we have connected both altimeters and both vertical speed indicators to the system and it...WORKED! :-) We will record some videos when we are done. Now the unit works just on a table controlled by industrial PLC, but the interfacing to FS via Arduino will be ok. Currently we have precission of +-30ft in range of 0 - 40000ft and maximal achievable speed of change is 240000ft/min (yep, 240 thousand). The whole unit is quite easy, in consits of a vacuum chamber and a very precise valve which can mix the vacuum with ambient air to get simulated low pressure environment. There is analog input 0 - 10V to tell the system which pressure we want, and a simple analog output for actual pressure feedback to the PC. The unit is powered by an air compressor (standard 4 - 6 bar) which generates the vacuum. Developed by local company specialized in industrial automatization. The estimated price is about 600USD. We will need three units - one for altimeters + varios, one for cabin pressure + cabin vario and one (modified) for IAS/mach gauges.

Czech DC-9 project (http://www.dc-9.eu)


Geremy Britton
10-18-2013, 11:17 AM
Pavel, Excellent work.
I've always said once we start finding uses for these real aircraft parts in a functional state, we're not only getting our simulators as real as it gets - but also conserving aviation history.

Thanks for the video!

11-01-2013, 09:50 AM
Geremy, that is so right! We love the feel of keeping those 50+ years old instruments still alive. The altimeters and varios will need some maintenance in local real-world avionics repair company just to clean them and to lubricate the moving parts, but they will be ok. Meanwhile we did another video which I am posting today - sorry for the quality, instead of HD we have switched the camcorded to low-res, but still tells the storry and shows also the other instruments working.

Notice the IAS indicators - we were simulating positive pressure into their "total pressure" port, so they showed positive airspeed, but the mach number plate was still stuck (can be hardly seen in the poor video, but you can see here how it looks http://www.hilmerby.com/dc9/ias_250.jpg) - that is because there was just ambient pressure in the mach plate, so our 400kt IAS didnt approach the speed of sound at that altitude. When fully connected to our simulator, there will be static port connected to the IAS (same as for altimeters) and total pressure port (the positive pressure created by forward motion), so both IAS in knots and mach number and the barber pole needle will be controlled.



12-04-2013, 04:44 PM
For those who would like to see how all the low pressure controllers look like - check our latest photos at http://www.dc-9.eu/photos (pressure instruments gallery) - today received :)


03-03-2014, 12:14 PM
Hi Pavel,
can you tell me which precise valve type did you used ?