The engine was the 295 hp Lycoming GO-480, which had a gearbox that lowered the output RPM and allowed for the use of a large three-bladed propeller to further improve takeoff performance.

Only the cabin area of the PA-17's original airframe remained unmodified, with the fuselage lengthened by four feet (1.2 meters), given a taller fin-rudder unit, clipped the Vagabond's stock 29 ft-3 inch (8.92 meter) wingspan down to only some 28.5 feet (8.7 meters), fitted the shortened wings with full-span leading-edge slats, long-span wing flaps that forced the ailerons to be much diminished in their span - only occupying the two outermost rib bays inboard of the wingtip; and a longer-travel main landing gear of a taller design, not unlike that of the 1930s-origin Fieseler Fi 156 Storch German military short take-off and landing (STOL) pioneer aircraft.

The powerplant for the demonstrator was switched to the Continental C85 boxer-four cylinder air-cooled engine, upgraded with fuel-injection, and uniquely equipped with a multi-belt speed reduction unit to drive its Aeroproducts nine-foot (2.75 meter) diameter, variable-pitch two-blade propeller, which contributed greatly to the amazing STOL flight characteristics of the demonstrator aircraft.

[5] For the construction of the production Courier aircraft, its all aluminum-clad airframe features a welded 15G steel-tube center section fuselage, with shoulder harnesses that protect the occupants in an emergency.

The wings are of conventional aluminum construction, but feature Handley Page leading-edge slats that deploy automatically when the aircraft's airspeed falls below a certain value — 55 to 60 miles per hour (89 to 97 km/h).

In conjunction with the leading-edge slats, 74% of the trailing edge incorporates high-lift slotted flaps, which together with interrupter blades atop each wing when roll control is lost at very low airspeed, allows for a tight turning radius.

The Helio has its main gear placement far forward of the cabin, enabling hard braking on unprepared landing areas.

[7] Jaars Helio Courier has been a frequent airshow performer at EAA AirVenture Oshkosh for decades, displaying its slow flight capability in front of thousands and serving as a drop plane for the Liberty Parachute Team.

Helios remain very popular among bush pilots in Canada (32 current) and Alaska and missionaries who fly into rough, relatively unprepared jungle airstrips because of its superior STOL abilities.