Originally Posted by
Dana
In level unaccelerated flight, wing loading does not change; it's aircraft weight divided by wing area. Well, it decreases slightly as fuel is burned, but that's it.
For Part 103 ultralights, the FAA has published a set of tables (In the AC103-7 appendix) that essentially give the required wing loading (assuming a 170# pilot) to achieve the mandated stall speed for various generic airfoil types. If your ultralight complies on paper with those tables, no further proof is required, even if the actual pilot is a sumo wrestler, and yes, even if the actual performance is outside the 103 limits. As those tables are rather generous, they're a good place to start your initial wing area sizing.