Thomas-Morse MB-4

The Thomas-Morse MB-4 was a prototype American mailplane of the 1920s. It was of unusual design, being a biplane with twin fuselages housing the crew of two and a central nacelle which carried the aircraft's twin engines in a push-pull configuration.

MB-4
Role Mail plane
National origin United States of America
Manufacturer Thomas-Morse Aircraft
First flight 1920
Number built at least 2
Developed from Thomas-Morse MB-3

Design and development

The MB-4 was designed to meet a June 1919 specification from the United States Post Office Department for a two- or three-engined mailplane, required to carry 1,500 lb (682 kg) of mail on a single engine.[1] Thomas-Morse chose to use as much as possible of its existing Thomas-Morse MB-3 fighter in order to reduce costs, using two engineless MB-3 fuselages to carry the crew and cargo, with the pilot in a cockpit in the nose of the port fuselage and the co-pilot/mechanic in a similar cockpit in the nose of the starboard fuselage, while cargo was carried behind the crew in each fuselage. Two 300 hp (224 kW) Wright-Hisso H V8 engines were mounted in a central nacelle between the two main fuselages in a push-pull configuration, with fuel tanks mounted between the engines.[1][2][3]

The MB-4's three-bay biplane wings were all new, with ailerons on the upper wing.[3] It had a conventional tailwheel undercarriage and had two separate tail assemblies, which were standard MB-3 empennages. Dual controls were fitted, with the pilot able to disconnect the co-pilot's controls, but there were no means of communication between the two cockpits.[1][2]

Operational history

The MB-4 made its maiden flight in February 1920.[1] While the aircraft had reasonable speed for the time,[3] it was otherwise poor, with one fuselage tending to take-off before the other, while the engines caused severe vibration which overloaded the aircraft's structure.[1][4] It was described as the "worst thing on wings" by Jerome Fried, the general plant superintendent of Thomas-Morse.[1]

One aircraft was tested by the US Post Office, but was not used for mail services, and was scrapped in 1921.[4] At least one MB.4[1] (and possibly 3[4]) was delivered to the United States Army Air Service where it was stored before being scrapped.[1]

The MB-4 was a failure, having extremely poor flying characteristics and being described as the "worst thing on wings",[1] and saw no service other than the trials by the manufacturer, US Army and the US Post Office.

Specifications

Data from General Dynamics Aircraft and their Predecessors[1]

General characteristics

  • Crew: 2
  • Length: 25 ft 5 in (7.74 m)
  • Wingspan: 45 ft 6 in (13.87 m)
  • Height: 11 ft (3.4 m)
  • Wing area: 645 sq ft (59.9 m2)
  • Empty weight: 3,554 lb (1,612 kg)
  • Gross weight: 5,564 lb (2,524 kg)
  • Powerplant: 2 × Wright-Hisso H water-cooled V8 engines, 300 hp (220 kW) each

Performance

  • Maximum speed: 122 mph (196 km/h, 106 kn)
  • Stall speed: 53 mph (85 km/h, 46 kn) [2]
  • Range: 600 mi (970 km, 520 nmi)
  • Time to altitude: 9,000 ft (2,745 m) in 10 min

References
Notes
  1. Wegg 1990, p. 26.
  2. Flight 1 April 1920, p. 373.
  3. Eberspacher 2001.
  4. "Thomas, Thomas-Morse". aerofiles. 1 August 2008. Retrieved 22 January 2011.
Bibliography
  • Eberspacher, Warren. "Thomas-Morse MB-4". Excerpts from AAHS Journal, Vol. 46, No. 3 - Fall 2001.
  • "New York Aero Show". Flight, 1 April 1920, pp. 370–373.
  • Wegg, John. General Dynamics Aircraft and their Predecessors. London:Putnam, 1990. ISBN 0-85177-833-X.
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