rocketbob

rocketbob

Well Known Member
Over the weekend I did the first flight of an RV9 that had a D60. During the first two test flights I found the indicated airspeed off significantly. Being someone who is proficient in embedded design I looked to see if there are calibration offsets that could be programmed.

There are not.

Really?

Are other EFIS's like this?

It would be a simple matter to have a screen with a look-up-table of offsets that one would determine thru test flying. With the advent of digital instruments there is no reason one would have to physically adjust static ports to get the airspeed to read correctly.

I'm actually sort of shocked that you can't do this.
 
Bob,

The EFIS manufacturers will explain that a steam guage airspeed will indicate the installation errors and they want the EFIS to indicate the same as a installed steam gauge to prevent confusion.

Blue Mountain did have a calibration table.

Jim Butcher
 
I called Dynon about this two years ago. I did an airspeed calibration test after I purchased my RV because the airspeed was not reading the same when compared to other aircrafts. I used formulas and test techniques that I learned at Naval Test Pilot School to determine the error. Once I determined the error and fixed the airspeed to within 2 knots throughout the airspeed envelope, I looked at the Dynon pub so I could bias the airspeed. Could not find anything so I called Dynon and explained to them what I wanted to do. The tech got very mad at me and told me he was offended. He said “so you are telling me that you believe your little formulas are better than our Dynon displays? There are hundreds of these things flying and no one complains.” I think he did not understand what I wanted to do. Regardless, I now have a chart that tells me the error at a certain IAS. My other airplane has two GRT screens. The GRT documents states they can calibrate TAS but not IAS. Page 9-5 http://www.grtavionics.com/File/User%20Manuals/Sport%20Users%20Rev%20D%20Sept%202010.pdf
 
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rocketbob said:
Thanks Jim.

Their argument is ****. :)
Click to expand...

My MGL XTreme has adjustments for ASI and ALT.................:D

And they work great. I LOVE the EXtreme. Best bang for the buck.

AND it can also dial in the vsi!!!!
 
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I sent a note to Dynon asking for two things on our D180. One was an airspeed lookup table. I think the wind velocity arrow really needs the correct true airspeed to be accurate. We use them in the helicopters I work with that have glass cockpits. The other item I asked Dynon about was a user preference one could set so that the HSI comes up with your preferred nav source.

The Dynon we have is a great product, but it could be better with a few programming updates. It is not TSOd software.

Phelps
 
Bob,

Have you checked the indicated airspeed with a manometer yet? It's possible that you're dealing with a leak in the plumbing or static source static source pressure error and not an issue with the transducer in the EFIS...Kevin Horton has some good discussion on his site and a helpful spreadsheet that will assist with flight test. If the manometer check is good and you've ruled out a leak on either the pitot or static side, you can use masking tape in front of or aft of the static port to dial things in during flight test. I ran into a similar problem when I installed dual DY-10's in our -4. It took some time to get the static ports adjusted to minimize error.

Best of luck,

Vac
 
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