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Reference guide

Every Part 103-legal ultralight (and how they stay legal)

Part 103 has no pilot certificate, no medical, no registration — and brutally hard limits: 254 lb empty, 5 gal fuel, 55 kn top speed. Here's how the survivors stay inside the envelope.

The three numbers that matter: empty weight ≤254 lb, fuel ≤5 US gallons, speed ≤55 kn (63 mph) in level flight. Stall ≤24 kn. These aren't averages — an overweight engine package or a 10-gallon tank moves the aircraft out of Part 103 entirely, into ELSA/experimental territory (and out of the no-license zone).

The survivors build light ON PURPOSE: Aerolite 103 (235 lb w/ Hirth F33 — a 55-lb single-cylinder four-stroke that keeps 19 lb of margin), Kolb FireFly (253 lb, chromoly cage, folding wings), Quicksilver single-seat variants (the historical benchmark).

Engine choice IS the legal decision: every manufacturer's page says so. A 63-hp twin may fly beautifully but tip the scales over the limit. Read the empty-weight line per ENGINE, not per MODEL.

Reality check: 55 kn and 5 gallons is a fair-weather, short-hop envelope — and its fans wouldn't have it any other way.

Original reference content compiled by the ClearProp team — specs and costs shift with manufacturer pricing; verify with the maker before committing. Not legal or purchase advice.