Arup S-4

S-4
Role	Blended wing body aircraft
National origin	United States of America
Manufacturer	Arup Manufacturing Corporation
Designer	Dr. C.L. Snyder, Raoul Hoffman
First flight	19 March 1935
Introduction	1935
Retired	bought and flown with a patched crack in its wood spar to a museum in the Dallas Ft Worth area in the early 70s
Number built	1
Developed from	Arup S-3

The Arup S-4 (Model 104) is the last in a series of round-wing aircraft from C.L. Snyder. ^[1]

Design and development

The S-4 was engineered by Raoul Hoffman. The test pilot was Glenn Doolittle, a cousin of Jimmy Doolittle. ^[2]

The S-4 used a low aspect ratio, semi-circular planform wing with a conventional landing gear and a small rudder with attached elevator on the rear of the fuselage. The aircraft was entered through a door mounted on the bottom of the aircraft. ^{[3] [4]}

Operational history

The S-4 prototype flew extensively in promotional demonstrations. The S-4 was emblazoned with Sears Roebuck and Company logos. The aircraft was scrapped for war materials in World War II. ^[5]

Variants

• Hoffman Flying Wing a design based on the Arup S-4 aircraft. ^[6]
• Milt Hatfield Little Bird - similar design. ^[7]

Aircraft on display

A replica is on display in the atrium of South Bend Airport ^[8]

Specifications (S-4)

Data from Janes, Popular Aviation

General characteristics

• Capacity: 2
• Length: 18 ft 6 in (5.64 m)
• Wingspan: 22 ft (6.7 m)
• Wing area: 273 sq ft (25.4 m²)
• Airfoil: NACA M-6
• Empty weight: 650 lb (295 kg)
• Gross weight: 1,200 lb (544 kg)
• Fuel capacity: 18
• Powerplant: 1 × LeBlond 70-5 5-cyl. air-cooled radial piston engine, 70 hp (52 kW)
• Maximum speed: 100 kn (115 mph, 185 km/h)
• Service ceiling: 9,000 ft (2,700 m)
• Rate of climb: 580 ft/min (2.9 m/s)

References

1. Avrocar: Canada's flying saucer : the story of Avro Canada's secret projects.
2. "Round aircraft designs". Archived from the original on 2 April 2012. Retrieved 7 September 2011.
3. "Announcing the New Arup". Popular Aviation. XVII (2). Chicago, IL: Aeronautical Publications Inc: 92. August 1935. Retrieved May 31, 2025.
4. Hoffmann, Raoul (September 1935). "A Low Aspect-Ratio Plane". Popular Aviation. XVII (3). Chicago, IL: Aeronautical Publications Inc: 158. Retrieved May 31, 2025.
5. "Low AR-planes" . Retrieved 7 September 2011.
6. Experimenter. December 1957.{{cite journal}}: Missing or empty |title= (help)
7. Bernard L Rice (March 1987). "Milt's Little Bird". Sport Aviation: 43.
8. "KSBN airport". Archived from the original on 22 March 2012. Retrieved 7 September 2011.