HM-4

The HM‑4, conceived by French aviator and designer Henri Mignet in the early 1930s, was the prototype that led to the famous Pou du Ciel (Flying Flea) series. Mignet, inspired by the desire to democratise flight, built the HM‑4 in his workshop at Saint‑Gilles, near Paris, and first flew it on 12 May 1933. The aircraft featured a simple, low‑cost construction using wood frames, fabric covering, and a twin‑engine layout with a small forward‑mounted engine driving a tractor propeller and a larger rear engine turning a pusher propeller. Its tandem wing configuration— a short, strongly‑incidence front wing and a longer, slightly aft rear wing—provided inherent stability without the need for complex control surfaces; pitch was managed by varying the front wing’s incidence, while roll and yaw were handled by a conventional aileron‑and‑rudder pair.

The HM‑4 demonstrated that amateur builders could safely construct and operate an aircraft with minimal technical expertise, sparking a worldwide home‑building movement. Though later safety concerns led to design revisions, the HM‑4’s legacy endures as a milestone in ultralight aviation, illustrating Mignet’s pioneering philosophy of accessible flight. Today, a few restored examples are displayed in French museums, reminding enthusiasts of its innovative spirit.