"And then the University of North Dakota, which has a large well-maintained fleet of aircraft, started running on unleaded Swift UL94 fuel and guess what? They started seeing exhaust valve recession on several aircraft."
My understanding is that this is not necessarily true. One valve on one...
That's not how it works.
Sport Pilot Airplane lets you fly powered airplanes that qualify as LSA and have an airplane certificate. No other certificate is required for you to shut off the engine and glide around if you wish.
Glider rating lets you fly aircraft that have a glider certificate...
Aircraft has a glider certificate
You have private pilot glider certificate - no 10 k limit
You have sport pilot glider (a truly pointless rating) cert - 10 k limit
Aircraft has an airplane certificate (and qualifies as an LSA but could be standard catagory, homebuilt, SLSA, ELSA, whatever)...
Rewind.
You want to make some money selling rides in a Pipistral Sinus (without an FAA medical).
You need a Sinus that has "glider" on the type certificate.
You need a Commercial (and/or CFI) Glider ticket with a "self launch" endorsement. You do not need a Sport Pilot airplane certificate...
Your choice.
(You would want a private glider rating - getting a sport pilot glider rating would be pointless).
Irrelevant. What does it say on an FAA type certificate? Glider or Airplane?
It is certificated either as a glider or airplane. Can't be both.
If it's certificated as an airplane you need a sport (or private, or...) pilot airplane (single engine land) rating to fly it. Of course, there is nothing preventing you from shutting off the engine.
If it is certificated as...
Strictly speaking - it's a glider rating with self-launch endorsement.
As I understand it, if you are a sport pilot and want a private glider you would need a current (within the last two years) flight review to do the solo parts of the glider rating. (same if you want to add Airplane sport to...