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This is a really old thread, but I am looking at the issue now. As some indicated above, the FAA regs are clear. An airplance instrument rating and glider rating allows you to fly gliders and motor gliders IFR, as long as you meet the ifr currency requirements. Motor gliders are gliders as far as the faa regs go, so you need no medical. It is possible to equip a motor glider with the items required in FAR 91.205. BUT, all the motor gliders I am aware of, are certified day vfr only. So this restriction does not change, whether you install all the ifr equipment or not. The manufacturer can not remove this restriction without a new certification for the motor glider. The only option I can think of is getting a DAR to do a field approval to add IFR to the Airworhtyness cert. I can't find any evidence that this has ever been accomplished. I've talked to EAA and they have no info. I will try the soaring society next, but it doesn't look good. I've hear rumors that STEMME will try to certify ifr on their new S6 and S8 due to military interest, but no written evidence, and those things cost $300K
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