Well.... one of the bits of really good advice I would usually offer I'm not able to do so since that horse already left the barn.
That being "don't present yourself to a FAA medical examination unless you know you can pass." Even if it means deferment while the reviewers in OKC confirm what the applicant and AME already know: That you are good to do, but your medical history requires the levels above the AME to do the approval.
That
you went in knowing (as you wrote your post) that you were going to be denied..... well, that
really got you started off on your back foot.
The rest of your question about how to obtain guidance on obtaining your medical, myself and the others here on POA need to defer to our two resident AME's, Dr. Lou Fowler and Dr. Bruce Chien.
@lbfjrmd @bbchien
Those two can provide the proper course of action needed. Everyone else are just well meaning SGOTI's.
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When you say you want to appeal, I'm not clear on what item you think you need an aviation lawyer for. Are you wanting to "fight" the denial as a whole? Or the requirement that the FAA instructed you to do a SODA ride?
To me, the letter you got about the SODA flight is a good strong hint at what activities you need to do, and do successfully, to greatly increase your chances to obtain a flight medical. So why fight that?
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Regarding your dilemma of sourcing an aircraft for the SODA ride.... Why not do the following?
Talk to your CFI about "skipping" the solo flight for the moment and moving on to the Dual Cross Country phase of training. In advance, work out the details with the flight school and your CFI to take your SODA ride and work out with the FSDO inspector that he will be PIC during the SODA flight. Then (1) make the flight to the FSDO city one of the destinations for the cross country flight and go there; (2) do the SODA flight in the aircraft you are already renting and familiar with; then (3) return to home base.
2 hour drive one way by car means at least 100-120nm by airplane. Add in landing at the additional airport on the way home and you filled in several checkboxes on a single training day.