Martin B-10

		Martin B-10

The Martin B-10 was the first all-metal monoplane bomber to go into regular service with the US Army Air Corps (USAAC). New design features included a fully enclosed cockpit, an internal bomb bay and retractable landing gear. It was obsolete by the time World War II began, but it was considered a pioneering type and it was the first U.S. bomber to see combat although by another nation.

It began as a private venture in early 1932 by the Glenn L. Martin Company as the Model 123 and was powered by two 600 hp (447 kW) Wright R-1820-E Cyclone engines. It was not bound to any specific military specification and therefore Martin engineers had a freehand to pursue the maximum performance possible for that time. It featured tandem open crew compartments, which was typical at the time as early pilots still preferred open cockpits and were reluctant to trust their instruments.

During initial trials, it was found that the aircraft could carry a bomb load 2,000 lbs (998 kg) over a range of 650 miles (1,046 km) at a maximum speed of 197 mph (317 km/h) at 6,000 ft (1,830 m). It was handed over to the USAAC in March 1932 and evaluated as the XB-907. The performance was somewhat higher than the Boeing YB-9, but Martin engineers felt that they could do better. After the trials were completed, it was sent back to Martin for modifications as the XB-907A. ¹

The XB-907A changed to enclosed crew stations, which was becoming a major factor due to the high speeds aircraft were now attaining. Engine cowlings were fully enclosed, replacing the NACA cowling rings on the Model 123. The engines were replaced with more powerful 675 hp (503 kW) Wright R-1820-19 Cyclones, the wing span was increased to 70 ft 7 in (21.71 m) for the lower drag associated with a higher aspect ratio. It also featured an enclosed nose turret. Although the XB-907A performance declined in in range and climb rate, it still had a top speed of 207 mph (333 km/h) which was faster than conventional fighters at that time. The Boeing P-12E pursuit fighter had a speed of 189 mph (304 km/h) and the Curtiss P-6E, still to be delivered, could do 197 mph (317 km/h), but only under ideal conditions.

Martin received a contract for 48 aircraft for the Model 139 production model and the USAAC bought the XB-907A which was designated the XB-10.² The first fourteen were designated pre-production YB-10s. This was followed by one YB-10A with turbo-supercharged engines. Additional orders included, seven YB-12s with 775 hp (578 kW) Pratt & Whitney Hornet engines, one XB-14 with 950 hp (708 kW) R-1830 Twin Wasp engines and twenty-five B-12As similar to the YB-12, but with increased fuel capacity.

In 1932, the B-10 was awarded the Collier Trophy for the most outstanding achievement in American aviation. The trophy was personally presented to Martin by President Franklin Roosevelt. It would be the first of six times Martin would be awarded the trophy.

The first deliveries were made in mid-1934 to the USAAC for service trials and in 1935 they were delivered to operational units that include the 7th, 9th, and 19th bomber groups. Deliveries continued through 1935-36 with an additional order of 103 B-10Bs.

Following the introduction of the Boeing B-17 and Douglas B-18, the B-10 was approved for export. The export version was the Model 139W. Argentina received 25, China (9) nine, Siam (6) six, Turkey (20) twenty, Russia (1) one, and the Netherlands 117. Only the first 39 Netherland aircraft were 139Ws which was similar to the B-10B. The remainder were designated as the Model 166 which had a long greenhouse canopy connecting both the forward and rear cockpits.³

The total production of all B-10 versions was 348 aircraft with 166 for the USAAC and 182 for export. Operators included Argentina, China, Netherlands, Philippines, Thailand and Turkey.

Specifications:
Martin B-10B

Dimensions:
Wing span: 70 ft 6 in (21.5 m)

Length: 44 ft 9 in (13.6 m)

Height: 15 ft 5 in (4.70 m)

Weights:
Empty: 9,681 lb (4,391 kg)

Max T/O: 16,400 lb (7,439 kg)

Performance:
Maximum Speed: 213 mph (343 km/h)

Cruise Speed: 193 mph (311 km/h)

Service Ceiling: 24,200 ft (7,375 m)

Range: 1,240 miles (1,996 km)

Powerplant:
Two 775 hp (578 kW) Wright R-1820-33 radial engines.

Armament:
Three Browning 0.30 caliber (7.62 mm) machine guns and
2,260 lbs. (1,030 kg) bombs.

	Specifications:
	Martin B-10B
	Dimensions:
Wing span:	70 ft 6 in (21.5 m)
Length:	44 ft 9 in (13.6 m)
Height:	15 ft 5 in (4.70 m)
	Weights:
Empty:	9,681 lb (4,391 kg)
Max T/O:	16,400 lb (7,439 kg)
	Performance:
Maximum Speed:	213 mph (343 km/h)
Cruise Speed:	193 mph (311 km/h)
Service Ceiling:	24,200 ft (7,375 m)
Range:	1,240 miles (1,996 km)
	Powerplant:
	Two 775 hp (578 kW) Wright R-1820-33 radial engines.
	Armament:
	Three Browning 0.30 caliber (7.62 mm) machine guns and 2,260 lbs. (1,030 kg) bombs.

Endnotes:

David Donald ed. The Complete Encyclopedia of World Aircraft. London: Brown Packaging Books Ltd., 1998. 599.

Lloyd S. Jones. U.S. Bombers. Fallbrook, California: Aero Publishers, 1974. 32.

Kenneth Munson. Bombers Between the Wars, 1919-1939. New York: The MacMillan Company, 1970. 140.