Douglas DB-7 for France

Last revised August 4, 2000


Although the crash of the Model 7B prototype was a setback, the French Purchasing Commission was sufficiently impressed by the Model 7B that they ordered one hundred examples on February 15, 1939. This was the first solid order for the Douglas design, since the USAAC had still not yet placed any firm order. Following the outbreak of war in Europe, 170 more examples were added to the order in October.

However, the French insisted on a large number of changes to prevent the aircraft from becoming obsolescent in the rapidly-evolving European market. The French wanted an increase in the aircraft's range and payload, more armor, as well as the installation of French-built instruments and weapons. Ed Heinemann approached Donald Douglas about the prospect of revising the design to make it more acceptable to the French Purchasing Commission. Donald Douglas reluctantly agreed, but as it turned out so many changes were required, in fact, that the revised design was a virtually new aircraft. The modified version for the Armee de l'Air was designated DB-7 (which stood for Douglas Bomber 7).

The DB-7 retained the wing geometry and 1100 hp Twin Wasp engines of the 7B, but had a redesigned and larger fuselage. The fuselage was narrowed and deepened, which lowered aerodynamic resistance and enabled more fuel to be carried. A raised gunner's position was provided in the rear dorsal fuselage behind the wing trailing edge, which was covered by a sliding glass canopy and fitted with a single flexible machine gun. A ventral gun position was provided underneath the fuselage, which was fitted with a single machine gun. All gun armament on the aircraft was to be the French-built 7.5-mm Chatellerault machine gun. Most of the internal equipment was of French manufacture, with the instruments being calibrated metrically.

The interchangeable nose sections of the Model 7B were replaced by a single nose with a series of clear panels and a glass nose for a bombardier, plus four fixed 7.5-mm machine guns fitted slightly behind and below the nose, two on each side. Initially, the DB-7 did not have a flat-glass bomb-aiming panel in the nose, since the aircraft used a French Bronzavia bombsight that projected from the lower nose just aft of the transparency. Later French DB-7s had oval-shaped flat-glass panels installed.

With the revision of the fuselage, the wings were mounted near the middle of the fuselage rather than at the shoulder position. The slight sweep-back of the Model 7B's wing was replaced by a wing with a completely straight leading edge from wing tip to wing tip. In order to prevent the landing gear from getting too long, the engine nacelles were moved beneath the wings, whereas the engines of the 7B prototype had been enclosed in nacelles partially extending above the wings. The engines were a pair of Pratt & Whitney R-1830-SC3-G Twin Wasp radials, which were the civil equivalents of the Army's R-1830-45 radials. The nacelles were enlarged to handle the new engine mount and slightly revised landing gear, and they extended farther behind the wing trailing edge. The nose wheel leg, however, did need to be lengthened to compensate for the additional height of the fuselage off the ground.

The first DB-7 flew on August 17, 1939, and the first deliveries to France were made in October. The first one hundred DB-7s were powered by a pair of 1000 hp Pratt & Whitney R-1830-SC3-G radials with single-speed superchargers. The additional 170 DB-7s ordered in October differed from the earlier batch of one hundred in having two 1100 hp Pratt & Whitney R-1830-S3C4-G Twin Wasps equipped with two-speed superchargers and Stromberg injection carburetors. However, due to engine shortages, the S3C4-Gs were not readily available and the French agreed to allow Douglas to use the older engines in order to keep the line running. The S3C4-G Wasp did not appear on the DB-7 until the 131st example.

The DB-7s bore the French military designation of DB-7 B-3 (the B-3 meaning "three-seat bomber"). They were operated by the Armee de l'Air starting from January 1940. Late production DB-7s were fitted with self-sealing fuel tanks and included some armor protection for the crew. Following handover to the French in the USA, the DB-7s were shipped to Casablanca, where they were reassembled and test flown before being delivered to units in French North Africa and in France. Five Groupes de Bombardment (GB I/19, II/19, II/61, I/32, and II/32) had been scheduled to receive the DB-7, but only the first three had fully converted to the type by the time of the German invasion on May 10, 1940.

Only 64 DB-7s were in service at the time of the German western offensive. They were immediately rushed from North Africa to France and were committed in a piecemeal fashion in a vain attempt to halt the German advance. The first DB-7 sortie against the Germans was on May 31, 1940, when 12 aircraft attacked enemy columns near St. Quentin. Some seventy sorties were flown against troops and panzer concentrations, supply convoys and depots and road bridges. The French DB-7s did a fairly creditable job against the Germans, but at least eight were lost to ground fire and fighter attacks.

By the time of the German attack in the west, about half the DB-7 order had been completed, but many of these aircraft never got to France since they were en route at the time of the collapse. Some sixteen DB-7s from the first production batch were diverted for use by Belgium's Aviation Militare. In the event, France actually only received about seventy DB-7s out of the 270 that it had ordered. Only a very few of these actually saw any combat.

Just prior to the Armistice, all serviceable DB-7s were flown out of France to North Africa, where they were formed into four light bomber squadrons (GB I/32 and II/32 in Morocco and GB I/19 and II/61 in Algeria. These units later became part of the Vichy Air Force, which collaborated with the Germans. When the British attacked the French fleet on July 3, 1940 to prevent it from falling into German hands, DB-7s from GB 1/32 carried out a retaliatory strike against Gibraltar, but did not do any damage or suffer any losses. In November of 1942, during Operation Torch, US Navy carrier based fighters attacked the DB-7s of GB I/32 on the ground and inflicted severe losses on this unit, preventing it from opposing the Allied landing. This little-known service with the Vichy Air Force makes the DB-7 yet another example of an aircraft which fought on both sides in World War 2.

Shortly afterwards, the North African-based French forces switched over to the Allied side, but the DB-7s were by that time obsolete and were relegated to training and ancillary duties. However, from October 1944 to April 1945 a few DB-7s operated by GB I/34 Bearn and I/31 Aunis carried out attacks against German strongholds along the Atlantic coast of France.

Several Armee de l'Air DB-7s escaped to England after the fall of France, and these were incorporated into the RAF and given RAF serial numbers.

Specification of Douglas DB-7:

Engines: Two Pratt & Whitney R-1830-SC3-G air-cooled radials, each rated at 1050 hp for takeoff and 900 hp at 12,000 feet. Performance: Maximum speed 280 mph at sea level, 305 mph at 9650 feet, 295 mph at 13,000 feet. Cruising speed 270 mph. Landing speed 81 mph. Initial climb rate 2440 feet per minute. An altitude of 12,000 feet could be attained in 8 minutes. Service ceiling 25,800 feet. 996 miles combat range. The DB-7 could fly 462 miles with a 2080 pound bombload. Weights: 11,400 pounds empty, 17,031 pounds maximum takeoff. Dimensions: Wingspan 61 feet 3 inches, length 46 feet 11 3/4 inches, height 15 feet 10 inches, wing area 464 square feet. Armament: Four fixed 7.5-mm machine guns fitted slightly behind and below the nose, two on each side. One 7.5-mm machine gun on dorsal flexible mount. One 7.5-mm machine gun in flexible tunnel position. Maximum internal bombload was 2080 pounds.

Sources:


  1. American Combat Planes, Third Enlarged Edition, Ray Wagner, Doubleday, 1982.

  2. United States Military Aircraft Since 1909, Gordon Swanborough and Peter M. Bowers, Smithsonian, 1989.

  3. McDonnell Douglas Aircraft Since 1920, Vol 1, Rene J. Francillon, Naval Institute Press, 1988

  4. A-20 Havoc in Action, Aircraft Number 144, Squadron/Signal Publications, Jim Mesko, 1994.

  5. Famous Bombers of the Second World War, William Green, Doubleday, 1960

  6. Boston, Mitchell and Liberator In Australian Service, Stewart Wilson, Aerospace Publications, 1992.

  7. Jane's Fighting Aircraft of World War II, Military Press, 1989.