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Just looked at the Lamac ( light aircraft manufacturers association of Canada) specs. If I remember correctly, They want to see a maximum of 3 psf wing loading for Vc of 60mph, rising to a maximum of 12psf for Vc of 120mph and above.

Why only 3 psf? Looks to me they just want standard wings with a cl max of 1.5.

The Zenith 701 stol has a wing loading of about 10 psf, yet has a Vc of about 60mph, with a cl of about 3.

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It's a design standard to set minimum wing area for the airplane's intended speed range using "unassisted" Clmax as the basic parameter. And most low speed wings have a Clmax without enhancement of somewhere around 1.5/1.6.

The 701 gets its low speed range with small wings using both slats and slotted full span flaps to get its 3+ Clmax, so it doesn't really fall within the definition.

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  • $\begingroup$ I assume they want larger wing area at slower speed for safety? With a partially stalled smaller wing, there is more chance of a crash. Is this correct? $\endgroup$
    – Fred
    Commented May 29, 2019 at 17:28
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    $\begingroup$ Not more chance of a crash, just that there is more energy which can to put you in the hospital for a longer stay. Traditionally the "safety" of ultralights has always depended on the low energy of the potential crash making up for very unreliable 2 stroke engines. Ironically the biggest danger of very low loading ultralights is actually because of the low mass/large area;when the engine quits they tend to just stop (well not quite) and you have to aggressively nose down to maintain airspeed.Stall spin accidents on climbout when the rotax wingy-dingy thing stops wingy-dingying is the big one. $\endgroup$
    – John K
    Commented May 29, 2019 at 19:40

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