# What is the best aircraft by useful load fraction?

I’m looking for the most capable in terms of payload relative to own weight heavier than air vehicle of any type, size or era. Untested designs are of interest too.

Essentially, what is the most efficient way to fly?

I suppose that ultimate vehicle is probably made of top-end composite materials, uses high lift devices and is electric as batteries doesn’t count to the empty weight.

I have done a fair research on the topic from unmanned rc models to Stratolaunch, and so far the best discovery is https://www.nestofdragons.net/weird-airplanes/special-facet-opal/ with 1.73 ratio. This particular aircraft is a very old design and quoted numbers may be not realistic, so I wounder what is the modern record keeper?

• Take a letter, fold it into a paper airplane and throw it. Payload fraction = 1. Dec 16, 2022 at 21:33
• Batteries don't count towards the empty weight?! Because unless you have the option to remove them they are part of the aircraft and reduce your payload. Dec 16, 2022 at 21:35
• Off the top of my head Rutan's Globalflyer: empty weight 1'700kg, take off weight 10'000kg i.e. 0.17 empty-weight fraction. The aircraft you linked had an empty-weight fraction of 0.4 a quite extreme value for homebuilt composite airplane... its end might suggest that it was indeed structurally too extreme Dec 16, 2022 at 21:40
• fuel apparently also counts as useful load, hence no need for electric. There's that thing with counting fuel / batteries as useful load, it's really a bit pointless. What you want really is Dec 21, 2022 at 7:09

I assume that even with a paramotor the ratio $$m_{payload} / m_{TOW}$$ still holds as "quite good".