replacing 912uls with 912is - DAR required?

The entire fuel and electrical system also needs to be redesigned. Essentially, going from a carbureted engine to a fuel-injected engine is a major alteration.

Rotax-Owner wrote:

The entire fuel and electrical system also needs to be redesigned. Essentially, going from a carbureted engine to a fuel-injected engine is a major alteration.

I'm trying to understand becuase this is an expensive decision and I can't afford to make a mistake.  I know that replacing the dual bing carbs with fuel injection was a huge engineering task for the Rotax engineers but does it trigger any of these items?

"Significantly affects weight, balance, structural strength, performance, powerplant operation, flight characteristics, or other qualities affecting airworthiness"

What am I missing here?

No, you can’t just swap the 912ULS for a 912iS and sign it off yourself. The FAA considers this a major alteration, so you’ll need DAR approval, and the aircraft will go back into “Phase I” flight testing.

Even though HP power is the same, going from a carbureted engine to a “FADEC” controlled, fuel-injected engine significantly changes powerplant operation and requires a redesigned fuel and electrical system, which triggers the “major alteration” definition.

You need to look at your operating limitations that are part of your air worthiness certificate for instructions for how to complete a major alteration. 

This is most certainly a major alteration. It will affect the performance of the aircraft. If this was a certified airplane, it wouldn't even be allowed unless you had an STC. 

Most likely, the process is going to be to complete the alteration. Contact your local FSDO. Let them know about the change and provide a program for your test environment. Essentially it will be something like "I am seeking concurrence for an a major alteration for my aircraft's operating limitations.

My proposed test program is to flythe aircraft within so many miles of XY airport for a minimum of 5 hours per my operating limitations."

The FSDO will either approve it or decline it. You will need to make a logbook entry that you made the alteration and got approval from the FSDO to do the flights. After completion you will make another logbook entry that you completed. If you don't have the aircrafts operating limitations you're not even supposed to be flying the airplane. They're supposed to be in the airplane. The FAA may have a copy of them. If they do not have a copy of them, you may have to apply for a replacement or new air worthiness certificate.

I had some steps to go through when I did mine but I was able to get all this done through my local FSDO without using a DAR. My operating limitations were misplaced so I had the extra steps. 

If you have them or if the FAA has them then there's a good chance the process will be very easy for you.