air speed indicator calibration

[n502pd]

I have read an artical elsewhere, dated 2002, about using a manomometer(sp?) with a water column. they referenced another article, AN 05-10-24. I can not find anything close to it on the web searches I have done. The info in the Kitplanes article has been subsiquently questioned reguarding the data accuracy, but not the method. Does anyone know where I can get the original AN publication? thanks in advance!

[Bryan Cotton]

Joe,

May be too late. A buddy of mine just sent out pictures of his calibration setup. I asked him about it and he sent me these links:
http://www.eaa1000.av.org/technicl/instcal/instcal.htm

http://www.iflyez.com/manometer.shtml

[n502pd]

Thanks Bryan! I had not seen this one before, and am intrigued with the math. However, I have completed my 'rig' and checked several instruments and one aircraft for functionality. I am using published coorelation charts for inches of water to airspeed, and find both the knots and mph charts easier to use. At the moment I am not addressing errors, but may well do so in the flight testing stage, which is a couple of years off(for me at least!!).Had to repair one static system on a ch750, so its worth while to do! One word of caution, as checked with the DAR, one should not consider using this system to technically , maybe leagally too, 'calibrate' any instrument as there is no tracability to NBS referenced cal standards. Rather, one should only consider using it for a functionality check, eg leaks or miss routings of lines. Thanks again, and I am following your posts every time!! As some say, very good on you!! :)

[pfhoeycfi]

Does anyone have a source for airspeed vs pressure (inches of water) tables or charts. I have 2 MGL ASIs indicating a 10 - 15 mph difference between the 2 and I'd like to do some testing with a manometer.

Peter

[n502pd]

Yes I have something from my building N502PD. I have to dig it out, get the article amd pass it to you. I will have to make time later tonight, or in late AM tomorrow.

[rick9mjn]

here is a link ,and if it does not work ,here are some rounded munbers ,
110 mph = 8 in. of water colum , 140mph - 13 in of water , these are not perfect numbers,
but looking at the article , thay are good to 3 decimal places,
http://www.rstengineering.com/rst/articles/KP89JUL.pdf
good day / rick

[rick9mjn]

also here is another link
http://www.n56ml.com/airspeed_calibration/
good day / rick

[pfhoeycfi]

I found this as well. The tables are in the appendix. There is no table for inches of water so a simple conversion must be made if using a water manometer.

https://ntrs.nasa.gov/citations/19800015804

[n502pd]

thats pretty much what I did, verrification only. the manometer method will also find slow leaks, in the gauge, or plumbing.. Have fun!