It was a low wing cantilever monoplane resembling a cropped double delta in plan, with a short fuselage ending at the pusher engine and propeller.

[4] It was powered by a 105 hp (78 kW) Hirth HM 504 air-cooled, four cylinder, inverted inline engine,[1] which was totally enclosed within the flat sided fuselage with no side-scoops for cooling air,[2] an arrangement which led to overheating.

[1][2] After the cooling problems and some issues concerning the undercarriage had been resolved, the same aircraft flew as the Pa.61B Arbalète but proved to be underpowered with the Hirth engine.

[1] As a result, a new machine, the Pa.61F Arbalète II, was built, powered by a 180 hp (134 kW) Lycoming O-360 air-cooled flat-four engine with side air intakes on the semi-monocoque, circular cross-section fuselage.

The Arbalète II's main undercarriage legs were moved inboard, mounted on the wing but close to the fuselage.