Douglas DB-7B Boston

In 1940, the new Douglas bomber also attracted the attention of the British Purchasing Commission, which was, like its French counterpart, touring various American aircraft factories in search of combat planes. The British Purchasing Commission was impressed with the DB-7, but wanted some changes which would better suit it to British requirements.

An initial order for 150 was placed on February 20, 1940, which was increased to 300 on April 17. The British version of the Douglas bomber was designated DB-7B. As compared to the DB-7A for France, the DB-7B for Britain had revised systems and introduced a flat-glass bomb-aimer nose extending six inches further forward and having 25 percent more glazed area. Instead of a stepped arrangement for the nose glass, the glass went back at a diagonal angle for improved visibility. The DB-7B was fitted with British instruments and bomb racks and was armed with 0.303-inch machine guns. Power was provided by two 1600 hp Wright R-2600-A5B radials that were equipped with two-speed superchargers. As compared to the DB-7A, the self-sealing tanks were improved and armor protection was better. Total fuel capacity was increased from 205 US gallons to 394 US gallons in order to improve the range, which had been the primary weakness of the earlier Douglas bombers. Because the British 0.303-inch machine guns were larger than the French 7.5-mm guns, four could not be fitted into the lower nose, so two were kept inside and the other two were carried outside the nose in removeable streamlined blisters.

Following the standard RAF practice of assigning popular names to their aircraft, the name Boston was assigned to the DB-7B. Roman numerals were used to designate different versions. However, by the time that deliveries of the DB-7B to Britain had started, the designations Boston I and II had previously been applied to DB-7 aircraft commandeered from French orders, and so the DB-7Bs were designated Boston III. The first DB-7B flew on January 10, 1941. 541 were built between May and December of 1941. In addition, one DB-7B was delivered as a replacement for the DB-7A which had crashed while under test in the USA.

A Boston III was experimentally fitted with a twin-Browning Bristol power-operated dorsal turret, and one was fitted with four rocket-launching rails underneath each wing. These options were not adopted as standard, but a Martin power turret later became standard on later A-20s for the USAAF.

The Boston III began to arrive in Britain in the spring of 1941. The Boston III was the first of the DB-7/A-20 series actually to operate with the RAF in its intended role of light bomber. They were supplied to RAF squadrons in the United Kingdom, in the Middle East and later in Italy. They replaced the Blenheims previously operated by these units. The first raid against the enemy in occupied France took place on February 12, 1942. And Bostons took part in the attacks on the German warships Scharnhorst, Prinz Eugen, and Gneisenau when they were involved in the famous channel dash during Operation Cerberus.

Many Boston III aircraft were modified to Turbinlite or Intruder configurations. Turbinlite was the name given to a night fighter version which was modified to carry a 2.7 million candlepower Helmore/G.E.C. searchlight in the nose in addition to the AI radar. The system was built by the General Electric Company and it was intended that searchlight would operate in conjunction with the AI radar. The radar would be used to locate enemy night intruders, and the aircraft's radar controller would direct the pilot to close to within 3000 feet of the target. The spotlight would then illuminate the target so that accompanying fighters could attack it. Thirty-one such Turbinlite conversions were made. Since the nose and the bomb bay were now full of equipment, the Turbinlite Havoc was unarmed and depended on accompanying fighters to destroy the targets which it was supposed to illuminate. This mode of attack was not all that successful, since the glaring searchlight gave enemy defensive gunners something bright to fire at. The development of centrimetric radar made such tactics obsolete, and the Turbinlite Havoc units were soon disbanded. The Boston III (Intruder) aircraft retained their transparent noses but were painted matte black, equipped with flame-damping exhausts, and fitted with a belly gun pack housing four 20-mm Hispano cannon which supplemented the standard Boston III armament. These operated from mid 1942-onwards. There were 7,385 DB-7/A-20 aircraft produced.

GB Planes and Specifications