Martin B-10
The Martin B-10 is a bomber aircraft designed by the Glenn L. Martin Company. Entering service in June 1934, it was the first all-metal monoplane bomber to be regularly used by the United States Army Air Corps. It was also the first mass-produced bomber whose performance was superior to that of the Army's pursuit aircraft of the time.
The B-10 served as the airframe for the B-12, B-13, B-14, A-15, and O-45 designations – using Pratt & Whitney engines instead of Wright Cyclones. A total of 348 of all versions were built. The largest users were the US, with 166, and the Netherlands, with 121.
Design and development
The B-10 began a revolution in bomber design. Its all-metal monoplane airframe, along with its features of closed cockpits, rotating gun turrets, retractable landing gear, internal bomb bay, and full engine cowlings, became the standard for bomber designs worldwide for decades. It made all existing bombers completely obsolete. Martin received the 1932 Collier Trophy for designing the XB-10.The B-10 began as the Martin Model 123, a private venture by the Glenn L. Martin Company of Baltimore, Maryland. It had a crew of four: pilot, copilot, nose gunner and fuselage gunner. As in previous bombers, the four crew compartments were open, but it had a number of design innovations as well.
These innovations included a deep belly for an internal bomb bay and retractable main landing gear. Its Wright SR-1820-E Cyclone engines provided sufficient power. The Model 123 first flew on 16 February 1932 and was delivered for testing to the U.S. Army on 20 March as the XB-907. After testing it was sent back to Martin for redesigning and was rebuilt as the XB-10.
The XB-10 delivered to the Army had major differences from the original aircraft. Where the Model 123 had Townend rings, the XB-10 had full NACA cowlings to decrease drag. It also sported a pair of Wright R-1820-19 engines, and an increase in the wingspan, along with an enclosed nose turret. When the XB-10 flew during trials in June, it recorded a speed of at. This was an impressive performance for 1932.
Following the success of the XB-10, a number of changes were made, including reduction to a three-man crew and addition of canopies for all crew positions. The Army ordered 48 of these on 17 January 1933. The first 14 aircraft were designated YB-10 and delivered to Wright Field, starting in November 1933, and used in the Army Air Corps Mail Operation. The production model of the XB-10, the YB-10, was very similar to its prototype.
Operational history
United States
In 1935, the Army ordered an additional 103 aircraft designated B-10B. These had only minor changes from the YB-10. Shipments began in July 1935. B-10Bs served with the 2d Bomb Group at Langley Field, the 9th Bomb Group at Mitchel Field, the 19th Bomb Group at March Field, the 6th Composite Group in the Panama Canal Zone, and the 4th Composite Group in the Philippines. In addition to conventional duties in the bomber role, some modified YB-10s and B-12As were operated for a time on large twin floats for coastal patrol.In February 1936, the US Army Air Corps used 13 B-10Bs of the 49th Bomb Squadron to drop supplies to the residents of Virginia's Tangier Island and Maryland's Smith Island; with ships unable to reach the islands due to heavy ice in the Chesapeake Bay, the islanders faced starvation after a severe winter storm. The B-10B supply flights followed earlier supply flights to the islands by the Goodyear Blimp Enterprise on 2 February 1936 and by the squadron's Keystone B-6A bombers on 9 and 10 February 1936.
With its advanced performance, the Martin company fully expected that export orders for the B-10 would flood in. The U.S. Army owned the rights to the Model 139 design. Once the Army's orders had been filled in 1936, Martin received permission to export Model 139s, and delivered versions to several air forces. These included six Model 139Ws sold to Siam in April 1937, powered by Wright R-1820-G3 Cyclone engines, and 20 Model 139Ws sold to Turkey in September 1937, powered by R-1820-G2 engines.
China
In July 1936, the Martin B-10 was put up for export, with the first sale being made to the Republic of China Air Force in the same year, purchasing six Model 139WC-1s and three Model 139WC-2s. When introduced, it was the fastest aircraft in China.The 139WC was primarily used for night bombing and maritime reconnaissance.
On 25 August 1937, as the air battles intensified in the early part of the Second Sino-Japanese War, five Chinese Nationalist Air Force bombers of the 8th BG, 19th and 30th Squadrons consisting of three Heinkel He 111As and two Martin B-10s, flying from their base in Nanjing to Shanghai, successfully dropped their bombs on Japanese landing forces at Liuhe, Taicang, northwest of Shanghai. However, Japanese aircraft pursued the bombers and shot up two of the Heinkels, forcing them to crash land; two crew members were killed on the ground by Japanese aircraft strafing them.
As the National Revolutionary Army of China fought desperately to hold onto their remaining positions in the Battle of Shanghai, the Chinese Air Force launched a major strike with a motley mix of aircraft against Japanese positions in Shanghai on 14 October 1937, consisting of three B-10s, two Heinkel He 111As, five Douglas O-2MCs, five Northrop Gammas, and three Curtiss Hawk IIIs from Nanjing in the late afternoon; in the evening, one bomber was launched every hour from Nanjing to attack Japanese positions in Shanghai until 03:00 on 15 October.
On 19 May 1938, two B-10s of the 2nd BG, 14th Squadron, led by Capt. Hsu Huan-sheng and Lt. Teng Yen-bo, successfully flew the first air raid on mainland Japan; the unescorted nighttime raid over Japan saw the B-10s dropped 2 million leaflets in "alerting the conscience of the Japanese people against atrocities committed by the Japanese invasion and occupation of China", over the cities of Nagasaki, Fukuoka, Kurume, Saga, and others, while reconnoitering airbases, ports, warships and factories.
Dutch East Indies
In the mid-1930s, the Netherlands government adopted a doctrine for defense of the Netherlands East Indies, which relied on the use of land-based bombers against any attacking force, with orders for defensive fighters cancelled to pay for the bomber force. The Martin 139 was chosen in preference to the Dutch Fokker T.V, as its all metal construction was considered more robust than the steel tube and fabric Fokker, while the Martin bomber was also already in production and therefore would be available sooner. Twelve Martin 139 WH-1s were ordered for the Royal Netherlands East Indies Army Air Force in 1936, followed by 26 improved WH-2s in March 1937, sufficient bombers to equip a Group of three squadrons. In December 1937, an order was placed for 39 Martin 139 WH-3s, followed by an order for 40 Martin 139 WH-3As in November 1938. Two more Martin 139 WH-3As were ordered in July 1939 to replace aircraft lost during delivery. The last of these attrition replacement aircraft was delivered in March 1940, including the last Martin B-10/139 built. On the outbreak of war with Japan in December 1941, about 58 Martins were operational with six squadrons, with about 20 more of the older variants in reserve. B-10s of the ML-KNIL served in the defense of the Dutch East Indies.During the start of Pacific War, Dutch Martin units were as follows:
- Ie Vliegtuiggroep based on Andir Airfield, Bandoeng which consisted of 1e Afdeling and 2e Afdeling, each has nine Martin 139WH-3/3A with additional two aircraft as reserve. Each afdeling has a detachment during the war, with the Patrouille Butner of 1-VLG-I stationed at Tarakan and Patrouille Cooke of 2-VLG-I stationed at Samarinda II Airfield, Melak.
- IIe Vliegtuiggroep based on Singosari Airfield, Malang which consisted of 1e Afdeling with nine WH-3/3A with three additional reserves and three WH-2. During the war, four patrouille consisted of three aircraft plus a reserve were created from 1-VLG-II, with the crews mobilized from Kalidjati flight school.
- IIIe Vliegtuiggroep based on Tjililitan Airfield, Batavia which consisted of 1e Afdeling and 3e Afdeling, each equipped with nine WH-3/3A with two additional reserves, and 2e Afdeling with nine WH-2 with two additional reserves. 7e Afdeling Bommenwerpers, a reserve unit mobilized on 15 December 1941, were placed under VLG-III and consisted of one WH-2, two WH-3 and six WH-3A.
Malayan campaign
In early January 1942, Dutch Martins along with British Blenheim bombers sortied over the west coast of Malaya to halt the Japanese advance. On 8 January, nine Martin and four Australian Hudson attacked a suspected Japanese seaplane tender anchored offshore in South China Sea, but the results were inconclusive. In the next day, nine Martin "quite successfully" bombed several Japanese ships unloading cargo at Kuantan. Two Martins were shot down by the Japanese near Penang on 1 January, while a further four Martins were lost while attacking Japanese forces on the Muar River on 19 January. On the same day, Dutch fighter squadrons were withdrawn to Sumatra, while the Martins were also withdrawn to Java three days later. Additional two Martins were destroyed and another two were damaged during an air raid at Sembawang on 22 January.