The Air King Model 26 was a single bay biplane with wings of rectangular plan, though with rounded, steel tube tips. The rest of the wing structure was a mixture of spruce and ash, with all wing surfaces fabric-covered. Because its upper and lower wings were interchangeable, the span of the upper one was only about 90% that of the lower, the latter mounted on the lower fuselage. They were braced together by inward-leaning, N-form interplane struts with 14 in (360 mm) of stagger and supported over the fuselage on short, outward-leaning cabane struts, an inverted V forwards and a single strut aft on each side. Only the lower wing was set with dihedral (2.5°). Ailerons on upper and lower wings were externally interconnected though, unusually, port and starboard pairs could be separately controlled.^[1][2]

The fuselage was a fabric-covered, trussed steel tube structure with the readily available Curtiss OX-5 water-cooled V-8 under a rather pointed cowling in the nose. Its honeycomb radiator was mounted under the upper wing. There were two wide, open cockpits, each with a bench seat for two. The tail surfaces were very angular and constructed from dural, with a tailplane externally braced to the fin and fuselage. Its control surfaces were broad chord; the elevators had a deep cut-out for rudder movement.^[1][2]

The Air King's fixed undercarriage was conventional for its time, its wheels on a single axle mounted on short, vertical legs with trailing drag struts attached to the lower fuselage and a rear tailskid.^[1]

The date of the Air King's first flight in uncertain but it had been completed by January 1927. No more four-seaters were built but in early 1928 the prototype reappeared as the Model 28 with a smaller rear cockpit seating only the pilot. The engine cowling was cleaned up, totally enclosing the OX-5, and the cabane struts revised with a forward single strut and a transverse V aft on each side. It had a wider track, split axle undercarriage with longer main legs from mid-fuselage. The vertical tail was also modified, with the external bracing removed and a rounded fin and rudder. It was 7 in (180 mm) shorter but its other dimensions were unchanged, as, largely, was the performance. Slightly cheaper, this two passenger version proved more popular and twenty-three were completed.^[3][4]

Model 26

1926 first prototype, three passengers.

Model 28

1928 two passenger version with cleaned-up engine cowling and new, two axle wider track undercarriage. 23 built.

Data from Aero Digest (1927)^[1]

General characteristics

• Crew: one
• Capacity: three passengers
• Length: 26 ft (7.9 m)
• Upper wingspan: 30 ft 11 in (9.42 m)
• Lower wingspan: 33 ft (10 m) ; another source has 34 ft 1 in (10.39 m)^[4]
• Height: 8 ft 8 in (2.64 m)
• Empty weight: 1,095 lb (497 kg)
• Fuel capacity: 35 US gal (29 imp gal; 130 L)
• Useful load: 850 lb (390 kg)
• Powerplant: 1 × Curtiss OX-5 water-cooled V-8, 90 hp (67 kW)
• Propellers: 2-bladed Hartzell Propeller

Performance

• Maximum speed: 99 mph (159 km/h, 86 kn)
• Cruise speed: 85 mph (137 km/h, 74 kn)
• Range: 400 mi (640 km, 350 nmi)
• Service ceiling: 17,000 ft (5,200 m)
• Rate of climb: 550 ft/min (2.8 m/s)
• Landing speed: 31 mph (50 km/h; 27 kn)