Stinson Model R

Design and development

In 1931, work began on a replacement for Stinson's SM-8 Junior four-seat light aircraft. The new design, the Model R, while based on the SM-8, had a shorter fuselage and a revised cabin. While the aircraft's undercarriage retained the basic tailwheel undercarriage layout of the SM-8, the split-axle mainwheels of the earlier aircraft were replaced by a semi-cantilever design, in which the mainwheels and shock-absorber units were enclosed in streamlined fairings attached to a short stub wing, which was also used to carry wing bracing struts. The aircraft had a fabric covered, welded steel-tube fuselage, while the wings were of mixed construction, with spruce spars and steel ribs, covered by fabric.

A retractable undercarriage was also designed for the Model R, with the mainwheels retracting upwards and inwards into the lower fuselage. This had less benefit to the aircraft's performance than was expected, however, and only a few aircraft were built with the retractable undercarriage. The aircraft was powered by a single Lycoming R-680 radial engine (Lycoming was controlled by the Cord Corporation, which also owned a controlling stake in Stinson, and so were the preferred powerplants for Stinson aircraft).

Operational history

The prototype made its maiden flight, piloted by Edward Stinson, in autumn 1931 and was certified as airworthy on 25 January 1932. Edward Stinson then set off on a sales tour with the prototype, and on the evening of that day, was carrying out a demonstration flight from Chicago when fuel shortage forced him to attempt a forced landing. Stinson received fatal injuries in the resultant crash.

Production continued, but the Great Depression caused sales to be slow, and only a total of 39 aircraft were built, including 5 Model R-3s fitted with retractable undercarriage. It was succeeded in production by the Stinson Reliant, which managed similar performance but was significantly cheaper ($3995 compared with $5595 for the Model R and $6495 for the R-3).

Variants

R

Basic model, powered by 215 hp (160 kW) Lycoming R-680 engine. 31 built (including prototype).

R-1

Proposed derivative of R with retractable undercarriage. Unbuilt.

R-2

Fitted with 240 hp (180 kW) Lycoming R-680BA engine, while retaining fixed undercarriage. Three built

R-3

Fitted with retractable undercarriage and R-680BA engine. Five built.

R-3S

Conversion of R-3 with 245 hp (183 kW) Lycoming R-680-6 engine.

Specifications (Model R)

Data from General Dynamics Aircraft and their Predecessors

General characteristics

Crew: 1

Capacity: 3 passengers

Length: 26 ft 1 in (7.95 m)

Wingspan: 43 ft 3 in (13.18 m)

Height: 8 ft 9 in (2.67 m)

Wing area: 235 sq ft (21.8 m²)

Empty weight: 2,225 lb (1,009 kg)

Gross weight: 3,325 lb (1,508 kg)

Powerplant: 1 × Lycoming R-680 9-cylinder radial engine, 215 hp (160 kW)

Performance

Maximum speed: 130 mph (209 km/h; 113 kn)

Cruise speed: 110 mph (177 km/h; 96 kn)

Stall speed: 52 mph (84 km/h; 45 kn)

Range: 450 mi (391 nmi; 724 km)

Service ceiling: 12,500 ft (3,800 m)

Rate of climb: 675 ft/min (3.43 m/s)