In 1976, a hang glider enthusiast named Steve Grossruck began exploring ways to increase the soaring performance of the Manta Products Fledgling (see Pterodactyl Fledgling in NASM collection). Grossruck sought the advice of polish-born sailplane pilot Witold Kasper. Kasper had won Poland's national sailplane championship on four occasions before World War II, and he proposed that Grossruck make some striking modifications to the Fledgling.

To give the Fledgling a better lift-to-drag ratio, Grossruck and Kasper designed a wing with highly reflexed, trailing edges, and wingtip rudders that did triple duty as air brakes and vortex generators (a reflexed airfoil takes the shape of a flattened 'S'). When the pilot of this aircraft flew slowly and carefully shifted her weight aft, she could induce a strong vortex over the top of the wing. These changes increased soaring performance but they also allowed the airplane to drop nearly vertical, but under complete control.

Except for the new design features of the wing, Grossruck built the Kasperwing like most ultralights of the day. He framed the swept, constant-chord wing with aluminum tubing, covered this frame with colorful Dacron fabric, and then braced it with stainless steel wires. Customers could buy a Kasperwing in one of several configurations: standard tricycle landing gear; twin, plastic floats for water takeoffs and landings; and a streamlined, plexiglas pod to enclose the pilot and reduce the effects of wind and temperature. Grossruck's company, Cascade Ultralights, required a week to fabricate each kit and the average buyer spent another 40 hours assembling the Kasperwing. The controlled, vertical descent maneuver put the Kasperwing on the map of innovative kitplane designs in 1980 when it won the Experimental Aircraft Association (EAA) Best Design Award.

Polish sailplane pilot and aerodynamicist Witold Kasprzyk (pronounced ‘vee-told kasper’), and American hang glider designer and entrepreneur Steve Grossruck, collaborated to design the Cascade Kasperwing ultralight aircraft. They began working together in 1977 to integrate Kasprzyk’s ideas about developing a unique wing shape and control system that permitted flight with little or no forward airspeed into the airframe of a Manta Products Fledgling hang glider (see Pterodactyl Fledgling displayed at the Steven F. Udvar-Hazy Center).

The two men designed innovative winglets that gave the experimental airframe additional lift by increasing the effective aspect ratio, cut drag by reducing the wingtip vortex, and provided control even when forward speed was zero and the aircraft was descending vertically. This control capability was completely unlike the control systems used in conventional aircraft. A pilot could stall the modified Fledgling, but instead of falling out of control, the wing gently settled into a near vertical descent or ‘mush’ and the pilot remained fully in control about all three axes of flight, pitch, yaw, and roll.

Kasprzyk and Grossruck decided to call their new aircraft the Kasperwing. As a hang glider, it flew very well for its time: sink rate 49 m (160 ft) per min and glider ratio 14:1. Grossruck flew the Kasperwing using a supine harness suspended beneath the wing by a strap that allowed him to recline on his back beneath the wing. Grossruck and Kasprzyk decided in 1978 to begin experimenting with engines installed on the Kasperwing to give pilots the capability to takeoff from level ground.

By 1980 the ultralight movement had become very popular and Grossruck decided enough people were interested in the Kasperwing to risk a business venture manufacturing and selling kits to build the airplane. A licensing agreement was established between Kasprzyk and Grossruck and production began at the Skyport in Issaquah, WA. Altogether, the factory delivered 333 Kasperwings between the fall of 1980 and summer of 1988 when production ceased. Mr. Phillip C. Farnam donated his Kasperwing 180-B (fitted with two Sea Hawk floats) to the National Air and Space Museum and the artifact arrived at the Paul E. Garber Facility on December 31, 1986.