They may not have any grounds to deny it, but of course every office seems to work a little differently with their own interpretation of the rules. One person licensed a Quicksilver MX-II as an experimental motor glider... he had to push against some fairly strong resistance but was able to get it done. I think he had to convince them that he often landed with the motor shut off, which is easy to do; we trained a lot of people in MX-II’s and we did a majority of our landings deadstick as a way to emphasize proper glide path judgement. The Quicksilver has neither a long wing nor a noteworthy glide ratio.
^ This.
Claims here to the contrary, there are NO concrete requirements defining a homebuilt motorglider as-such. None. Every single FAR and JAR spec cited in this thread is for classifying
type certificated motorgliders, not E-AB. As crazy as it sounds, the final determination is going to come down to the
opinion of the DAR or FAA examiner doing the airworthiness inspection, and that will not only vary from FSDO to FSDO, but from examiner to examiner, and so on down to whether he had a fight with his wife that morning.
If you can show that you've got a Glider rating on your certificate, have flown sailplanes at least "a bit," and the airplane has "long wings", a starter on the engine*, and generally "looks like a motorglider," you'll have a much better chance of getting your homebuilt declared a motorglider. If you show up with a denied medical on a PPL-ASEL with no "G", and something with short wings and a big motor, the "giggle factor" goes up and you're much less likely to get that declaration (and the privileges that go with it.)
The FAA
knows that people want to use the "motorglider loophole" to keep on flying without a medical, or get around the altitude, retractable gear, speed restrictions, and other limitations of LSA. They're generally not fools. If your
intent is clearly to go soaring, that's going to show in your cert, your logbook, and the overall appearance and
intent of the airplane you're presenting. If your
intent is to game the system to get around the medical or LSA requirements, that's usually going to be obvious, too. The case of the Challengers and similar aircraft were enough in the "gray zone" that they gained some notoriety in the back-and-forth to get them declared motorgliders.
So, for an E-AB airplane, span loading, L/D, sink rate, or any other metric are totally irrelevant towards getting it declared a motorglider. If you want to type certficate the design, then yes, JAR-22 is used by the FAA as a baseline but, ultimately, it's going to be up to the certification committee to make the final determination. E-R&D gets a
broad pass on limitations, if the proposed design mission supports the notion that the aircraft is intended to operate power-off for significant portions of that mission. This is how things like Scaled Composites'
Space Ship One can get a "motorglider" declaration. But E-R&D isn't homebuilding, and gets much tighter scrutiny in other ways.
@cluttonfred, if your intent is to build a self-launching sailplane or glider, make sure you can convince the examiner that you're really out to do just that. People who are serious about it won't have a hard time.
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* A purported ICE or electric "motorglider" without some kind of in-flight restart capability is going to be laughed at. Openly, with a "nice try" thrown in for good measure. Think about it: A motorglider takes off and climbs out, shuts down the engine and goes soaring. Very often, at the end of the day, it's restarted to fly back to the airport. The
other point to having the engine on board - for most glider pilots, the
main point - is to be able to use the engine for a "save" if the lift dies out, especially in places with poor prospects for an outlanding. If you can't restart the engine, you're not serious about ever shutting it down in-flight, and that's going to be
really obvious.
