Ha Ha! Grants Pass Bill gets his name because his name is Bill, and he lives in Grants Pass, Oregon. No offense taken, nor are there any hard feelings regarding any perceived flippancy on your part.
I've just never heard the bit about a 337 being required. I maintain a King Air and just last year, we revised our maintenance program, working hand-in-hand with our PMI. We operate part 91 and choose not to encumber ourselves with an MEL, but rather to deal with inoperative equipment (if we can't fix it on the spot) IAW FAR 91.213 with the inspection of such inoperative instruments/equipments IAW FAR 91.405.
In fact, 91.213(d)(4) states "An aircraft with inoperative instruments or equipment as provided in paragraph (d) of this section is considered to be in a properly altered condition acceptable to the Administrator." So, although an aircraft may have originally been certified with a particular instrument or equipment, so long as it's not required for day VFR and the conditions spelled out in 91.213 have been met, there's no need for the 337. If it is beyond the scope of 91.213, a special flight permit may be required, or perhaps no flight would be authorized, or even safe.
Thank you for your military service. You're undoubtedly giving the country some of the best years of your life. You'll never regret it!
Now, back to airplanes.
