The racer was definitely a novel design, incorporating many different features, including a tandem landing gear with wheels sunk into the belly of the aircraft, the front wheel was steerable and hydraulic brakes were applied when the stick was shoved forward, roller skate wheels, attached to the wing tips, were used as outriggers. Its most novel feature was the variable-incidence wing that provided a high angle of attack for takeoff and landing, while permitting the fuselage to remain almost parallel to the runway for good pilot vision.
The Par Special was first flown by another McDonnell employee, Art Beckington, in January 1950. Beckington did most of the flight testing and subsequently flew the aircraft, that had been listed as Racer number "87", in a number of races. The aircraft was dubbed "Mixmaster" by the newspapers, referring to the Douglas XB-42. It was powered by a mid-fuselage-mounted 85 hp Continental C85 four-cylinder horizontally-opposed air-cooled engine, driving a pusher propeller at the extreme Y-tail by a long extension shaft. It was this extensions shaft that proved to be troublesome, preventing the aircraft to be competitive.
The aircraft was used for only a short period, as 1952 it had been broken up and parts had been used to buit the Mace-Trefethen Seamaster.
Span: 20 ft 0 in (6.10 m)
Length: 20 ft 0 in (6.10 m)
Wing area: 66.67 sq.ft (6.19 sq.m)
Max speed: 190 mph (306 kmh)
Cruise speed: 140 mph (225 kmh)
Ceiling: 12,000 ft (3,658 m)."