The ADC200 is a pretty common box, which connects to the pitot and static pipes, and gets the heading, the GPS track, the OAT, and outputs TAS and wind data to the GPS so that the GPS now shows the actual wind.
This is a panel mount version of it which I would probably go for, replacing the 2" Shadin I currently have.
They have various STCs but none directly applicable.
However I cannot see why this should be a Major Alteration, according to FAR 43 Appendix A.
Get an Aspen 
Picking up an old thread…
I see these going for a few hundred $ on US Ebay.
Does anyone know the usual certification regime for an N-reg installation?
I cannot see it being a Major Alteration IAW FAR 23 because it is not a “basic change”.
It would give me a TAS readout on the KLN94, or anything else I get to replace it.
It seems to have a “fuel flow option”
but it is not apparent what the point is, because it accepts it only via RS232, and from a Shadin fuel totaliser instrument. But such an instrument is already feeding the GPS via RS232, so what is the point of feeding its output via the ADC-200 and then to the GPS?
Is it done because the GPS does not have enough RS232 inputs, so the data has to be combined?
I had a Shadin Miniflo before I added the ADC200. Wrapping the Miniflo thru the ADC200 meant I could keep both. Otherwise there would be null data on the ADC200.
I can’t see why this should be a major change, it is just a box that gives a little more info to the pilot that has no effect on the aircraft systems, the only slightly controversial bit might be the fuel flow transmitter in because it is part of the fuel system but as this is already fitted to your aircraft they cannot get difficult over this.
This having been said I have yet to meet an organisation that I have as little respect for as EASA when it comes to making good technical and flight safety decisions.
The critical part IMO is the pressure altitude output. If the KLN94 (TSO C129) receiver is using it, then I’d be surprised if it isn’t a major change, as the pressure altitude source is used at least for monitoring integrity.
Peter did you have a look at the Sandia Aero ADC box? .Though a bit more expensive
http://sandia.aero/product/sac-7-35-air-data-computer/
Tomjnx.
You make a good point however exchanging one TSO’d air data sorce for another SHOULD not be an issue however anything is posable in EASAland.
Of course there will also have to be a change in the ATC transponder system as I would think that Peter would remove the old encoder or have the transponder air data sorce selectable to give some redundancy.
I would ignore the fuel flow aspects unless the pass-through is necessary due to the KLN94 not having enough inputs.
There would be no altitude signals because the ADC gets it from the static tubing.
So, apart from the fuel totaliser pass-through, no effect on aircraft systems.
