Douglas A-20 Havoc (Boston, DB-7. P-70) was an American attack, medium bomber, intruder and night fighter aircraft of World War II. USAAC in autumn 1937 published the specification for a new bomber. The design team from company Douglas decided to modify the earlier draft Model 7A through replacement of engines for stronger Pratt & Whitney R-1830 S3C3-G with a capacity of 1100 hp, changing the designation of the project on the Model 7B. Two alternative were proposed to use part of the bow, one transparent to the bombardier and the other covered , equipped with a battery of six machine 7.7 mm guns and two 12.7 mm caliber. For the transparent part of the bow you could mount two gondolas on both sides of the hull, including two machine guns. The other armament were supposed to be machine guns mounted in a 7.7 mm turret or fire through the open bomb bay doors. Capacity bomb was increased to 900 kg. Competitors for Douglas construction were planes North American NA-40, Stearman Model X-100 and Martin 167F. Although the Model 7B was sufficiently fast and agile, he did not arouse interest in the US Army, but he scored for recognition of the French Commission for the purchasing, visiting the United States. The French side participated in testing Douglas machines and eventually ordered 100 machines, increasing the order to 270 at the start of the war. USAAC finally ordered the first copies of the A-20 in mid-1939 years. Another user DB-7 was a British RAF, which because of the situation in France has decided to take the French order for planes (designation Boston Mk I and Mk II, depending on the engine). Later, Brits have already received orders from their own machines (versions Boston Mk III, IV, V). The largest user of the A-20 was the Soviet Union and for their needs were produced more than half of these machines. It was expected to provide 3125 machines of all types in the framework of the Lend-Lease, but ultimately went to the Soviet Union 2901 aircraft. The main route of delivery was overflown by Iran or Alaska because of too much risk to attack convoys by German submarines. These machines are called the Soviet Union the A-20 Boston. Russians often modified the structure of the A-20 to their needs: replaced the rear turret, added torpedoes, changed the structure of the nose and adjusted planes to harsh winter conditions. A-20 designed as a light bomber has successfully served as gunship aircraft, torpedo and reconnaissance, and even a night fighter. It was easy to use and piloting and easy to build. Total production: 7478.

General Specifications

• Type: Shoulder-wing cantilever monoplane.
• Wings: The aircraft has a laminar-flow wing section with no center-section; the left and right wing panels attach directly to the fuselage. The structure includes two spars built with unspliced spar caps and integral end fittings. The wings have chordwise stiffeners and flush-riveted metal skin. It features electrically-operated slotted trailing-edge flaps.

Fuselage

• Structure: All-metal semi-monocoque with a practically square cross-section featuring rounded corners.

Tail Unit

• Configuration: Cantilever monoplane type with a dihedral tailplane. It is an all-metal structure with trim-tabs in all control surfaces.

Landing Gear

• Configuration: Retractable tricycle type operated hydraulically. The main wheels retract into the engine nacelles, and the nose wheel rotates 90° to lie flat at the bottom of the fuselage.

Power Plant

• Engines: The aircraft is powered by two Pratt & Whitney R-2800-71 eighteen-cylinder radial air-cooled engines, each producing 2,000 horsepower with two-speed superchargers.
• Propellers: Equipped with three-blade Hamilton-Standard Hydromatic constant-speed quick-feathering airscrews.
• Engine Mountings: These are interchangeable

  General Specifications

  • Type: Twin-engined attack bomber.

  Wings

  • Configuration: Mid-wing cantilever monoplane.
  • Structure: Each wing consists of an inner section with an integral engine nacelle, an outer section, and a wing-tip. The inner section attaches to the fuselage at five points, and the inner and outer sections are connected at five similar points.
  • Design: Single-spar aluminum-alloy structure with stressed Alclad skin.
  • Control Surfaces: Framing-edge flaps are located on the inner wing sections, and ailerons are on the outer sections. The ailerons include trimming-tabs, interconnected and controlled from the pilot's compartment.

  Fuselage

  • Construction: Aluminum-alloy monocoque with smooth, flush-riveted Alclad skin. The nose and tail cone are detachable.

  Tail Unit

  • Type: Cantilever monoplane with a 10-degree dihedral tailplane.
  • Surfaces: Fixed surfaces are all-metal with stressed-skin covering; movable surfaces have metal frames with fabric covering. Trimming-tabs are installed in both elevators and the rudder, controllable from the pilot's cockpit.

  Landing Gear

  • Type: Retractable tricycle type with hydraulic retraction, backed by an emergency hand operation system.
  • Mechanism: Main wheels retract backward into the tails of the engine nacelles, and the nose wheel retracts into the fuselage. The system includes oleo-pneumatic shock absorbers and hydraulic brakes.

  Power Plant

  • Engines: Two Wright R-2600-29 fourteen-cylinder radial air-cooled engines, each producing 1,700 horsepower. They are equipped with two-speed superchargers.
  • Propellers: Three-blade Hamilton-Standard Hydromatic constant-speed, full-feathering airscrews, with a diameter of 11 ft. 3 in. (3.43 m).
  • Fuel Tanks: The aircraft has four main self-sealing fuel tanks in the wings—two inboard (136 U.S. gallons each) and two outboard (64 U.S. gallons each) of the engine nacelles, totaling 400 U.S. gallons. For long-range missions, it can carry additional auxiliary tanks in the bomb bay and a boat-shaped external tank under the fuselage.

  Accommodation

  • Crew: Positions include a bomb-aimer (in models with a transparent plastic nose), pilot, and rear gunner. The pilot's cockpit is located in front of the wing leading-edge, accessed via a side-hinged hatch in the roof. The bomb compartment is positioned aft of the cockpit, followed by the rear gunner's compartment. Crew positions are armored.

  Armament

  • Varied Configurations: The aircraft can be configured with different types of noses, including a transparent plastic nose for bomb aiming or a closed attack nose for other versions. Specific armament details are not included in the description provided.

  Dimensions

  • Span: 61 ft. 3½ in. (17.8 m)
  • Length: 48 ft. 4 in. (14.74 m)
  • Height: 18 ft. 1½ in. (5.5 m)
  • Wing Area: 465 sq. ft. (43.2 sq. m)

  Weights and Loadings

  • Loaded Weight: 20,000 lbs. (9,080 kg)
  • Wing Loading: 43.01 lbs./sq. ft. (209.88 kg/sq. m)
  • Power Loading: 7.4 lbs./h.p. (3.36 kg/h.p.)

  Performance

  • Maximum Speed: 325 m.p.h. (520 km/h) at 14,500 ft. (4,420 m)
  • Cruising Speed: 280 m.p.h. (448 km/h) at 14,000 ft. (4,270 m)
  • Stalling Speed: 98 m.p.h. (157 km/h)
  • Initial Rate of Climb: 2,000 ft./min. (610 m/min)
  • Service Ceiling: 25,300 ft. (7,720 m)
  between left and right positions. The mountings feature a large metal spinning forward, a stainless steel rear part, and six identical forgings connecting them. The engines have quick-release fittings for lines, pipes, and wiring, and cowling is split into two quickly removable halves. An access door in the firewall allows mechanics to work on the engine accessory section from within the nacelle. Fuel and oil tanks are located in the wings and nacelles, respectively.

Accommodation

• Crew: The aircraft accommodates a crew of three, with all positions armored.

Armament

• Nose Configurations: Various fuselage nose types allow for different armament installations, including a transparent bombardier nose.
• A-26B Armament: Fixed forward-firing armament of six .50 caliber machine guns in the nose, with provisions for up to eight additional .50 caliber "package" guns under the wings, mounted in pairs outside each engine nacelle.
• A-26C Armament: Features a transparent bombardier nose and two fixed .50 caliber guns. Defensive armament includes two twin .50 caliber machine gun turrets, one above and one below the fuselage. These turrets are remotely controlled from a gun-sighting station aft of the wings, with aiming via periscopic sights. The upper turret, when locked in the forward position, can be fired by the pilot along with the nose armament.
• Bomb Bays: Internal bomb bays with hydraulically-operated doors, and external bomb racks under the wings.

Dimensions

• Span: 70 ft. (21.35 m)
• Length: 50 ft. 9 in. (15.47 m)
• Height: 18 ft. 6 in. (5.64 m)
• Wing Area: 540 sq. ft. (50 sq. m)

Bibliography:

• Scott Thompson - Douglas Havoc and Boston: The DB-7/A-20 Series, Crowood Aviation Series 2004
• William N. Hess - A-20 Boston at War
• Roger A. Freeman - Douglas A-20 Havoc U.S.A.A.F., 1940-1945, Camouflage & Markings Number 20
• Jim Mesko - A-20 Havoc in action, Squadron/Signal Publications Aircraft Number 144
• Pilots Manual Douglas A-20 Boston & Havoc, 1940
• Harry Gann - The Douglas A-20 (7A to Boston III), Aircraft Profile Number 202
• Richard J. Caruana - Douglas A-20 Boston / Havoc, Warpaint Series No. 32
• R. Johnson - American Attack Aircraft Since 1926, Mcfarland
• William Wolf -The Douglas A-20 Havoc, The Ultimate Look:From Drawing Board to Peerless Allied Light Bomber
• David Doyle - A-20 Havoc In Action
• United States Army Air Force - Douglas A-20 Havoc Pilot's Flight Operating Instructions
• Andrew Thomas, Chris Davey -Defiant, Blenheim and Havoc Aces, Osprey Aircraft of the Aces
• Robert A Watkins - Battle Colors, Volume III: Insignia and Tactical Markings of the Ninth Air Force in World War Two
• Dana Bell, Don Greer - Air Force Colors, Volume 2: ETO & MTO 1942-1945 - Squadron Signal Aircraft Specials series 6151
• Dana Bell, Don Greer - Air Force Colors Volume 3: Pacific & Home Front 1942-1947, Squadron Signal 6152
• Robert Watkins - Battle Colors Volume V: Pacific Theater of Operations: Insignia and Aircraft Markings of the U.S. Army Air Forces in World War II