A fuselage which deepened rapidly behind a small radial engine and ended with a fin integrated into it, together with a tricycle undercarriage with a tall and faired front leg, gave the Aircar an unusual appearance.

The wings were built around two wooden spars, with metal ribs and edges but fabric covered; they were fixed to the upper and lower fuselage.

The Aircar was initially fitted with a 95 hp (71 kW) Pobjoy Niagara II engine, a small diameter radial.

The all-metal, stressed skinned fuselage bulged rapidly behind the engine and was roughly circular in cross section between the wings.

These legs were joined to the front wing spar close to the fuselage, cross braced and splayed outwards to increase the track.

Landings were made from a low speed approach with flaps extended; throttled back, the Aircar adopted a horizontal attitude, the elevator only controlling the sink rate.

Tests led to changes in the engine cowling, to experiments with a four-bladed propeller produced by mounting a pair of two-bladed ones at right angles on the same shaft, and to a serious revision of the fin.

Given the nickname "Pregnant Guppy", ground and wind-tunnel testing revealed low rudder control authority and poor directional stability, as well as problems with engine cooling.

Convair persevered with the Aircar until it was deemed uneconomic to continue supplying engines and driveshafts to replace those damaged in testing.