I do a lot of back-of-a-napkin conceptual design and I was wondering how hard it would be to get a homebuilt light airplane classified as a motorglider. The FAA definition seems to be: 1) one or two seats; 2) 850 kg (1874 lb) max gross weight; and 3) 3 kg/sq m (0.62-lb/sq ft) max span loading (weight/span squared).

What strikes me as odd about that is that with a gross weight of 650 kg/1433 lb and a span of 13.74 m/45' 1", a classic motorglider like the Fournier RF-5 does not seem to qualify because of its span loading of 3.44 kg/sq m (0.7 lb/sq ft).

What gives...?

What strikes me as odd about that is that with a gross weight of 650 kg/1433 lb and a span of 13.74 m/45' 1", a classic motorglider like the Fournier RF-5 does not seem to qualify because of its span loading of 3.44 kg/sq m (0.7 lb/sq ft).

What gives...?

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