I am in the final stages of an IFR approval for a Garmin 530/430 plus other stuff on my Reims P337. This includes the 8110-3 for the antenna install with a required doubler riveted in place plus all the calcs for the DER. The DER was interested in hoop strength and I can give you the calculations plus the name of the DER who provided the 8110-3. With a P you must have an 8110-3 for the antenna install as a BTW.
We have the 337's approved for VFR flight and my IA is now doing the second set of 337's for IFR approval. I am hoping the final approvals will be signed off within a couple of weeks. The challenge will be the final sign off by my local FAA office, but they have been great in the past so I am hoping this will go ok as well.
If you are going to do this, read the new AC on GPS installs and approvals as it tells you in detail all you have to know. My advice is get involved as it will make the process faster.
An important note is that although my plane is on the N reg, the plane is a reims 337. It has a different type certificate than US built 337's. My experience with the FAA is that they know these are the same plane, but it does have implications.
In summary it has not been an easy process, but I am willing to share it with you. Drop me an e-mail at
dunderwood@torex.co.uk. I am travelling until 16th August, but can reply in detail after that.
Regards - Dave