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Douglas A-20 Havoc / Boston Light Bomber / Night-Fighter Aircraft


The Douglas A-20 Havoc proved a suitable and adaptable light bomber and night-fighter for Allied forces of World War 2.

 Updated: 1/22/2017; Authored By Dan Alex; Content ¬©www.MilitaryFactory.com

The Douglas A-20 Havoc served Allied forces through most of World War 2, fighting for British, American and Soviet forces. The type saw extensive use, proving itself a war-winner capable of withstanding a great deal of punishment but living up to its namesake in turn thanks to its speed and inherent firepower. Her crews put the aircraft through its paces with production topping over 7,000 units and several major production variants. Built as a light bomber but operated more or less as a heavy fighter, the Havoc proved a successful addition to the Douglas company line and the Allied war effort as a whole before being eventually replaced by the more capable Douglas A-26 Invader in the attack/light bombing role and Northrop P-61 Black Widow in the night-fighter role.

Development

The A-20 series began life as the Douglas Model 7B design, a light bomber attempt originally put to the paper as early as 1936. The United States Army Air Corps (USAAC) showed enough interest after a design review in 1938 that it ordered an operational prototype to be constructed under contract. The first flyable model took to the air on October 26th, 1938, and displayed extremely promising potential for such a design. The aircraft was fast on its twin engines and responsive to the controls with very few negative aspects to her overall design. At any rate, the future of the Model 7B was showing great promise.

With America still in an isolationist mentality despite the worsening situation in Europe (and the world for that matter), the Model 7B was not followed upon by the USAAC and shelved for the time being. Despite this setback, the French and Belgium governments came calling - with some desperation one can imagine - and ordered several hundred Model 7B's for immediate production in February of 1940. These were assigned the official designation of DB-7 and construction covered two distinct production models to become the DB-7A and the DB-7B. An initial batch of 100 DB-7's were constructed and an extended order for 270 more was put into action to help strengthen the ranks. Despite the initiative, only 115 DB-7;s were ultimately delivered to French forces before the collapse of France under German power. Some 95 French-operated DB-7's escaped to North Africa while the remaining models in American hands - and the contract to go along with them - were diverted to British ownership who took over operation of the type as the "Boston". The British Boston series covered three distinct marks as the Boston Mk.I (DB-7), Boston Mk.II (DB-7A) and Boston Mk.III (DB-7B).

RAF Bostons were fielded as day bombers initially, though these met with disastrous results. The type was found to be unsuitable for such a dangerous role and therefore modified into a dedicated night-fighter form. The RAF selected roughly 100 of these Boston light bombers and produced the converted "Havoc", intruder aircraft fitted with the AI Mk IV series of radar in the nose housing and as many as 12 x 7.7mm machine guns to handle the offensive dirty work. Additionally, these converted Bostons were given increased armor protection for the crew and specialized exhaust piping to dampen the flame effects of the engines at night. Essentially, the British RAF gave birth to the "Havoc" series by default, despite its origins as an American airplane. Havocs were first fielded by No. 23 Squadron.

With its newfound weapon, the RAF initiated several interesting - yet costly - projects involving the Havoc. One such initiative involved the "Turbinlite", night-fighting Havoc Mk I models fitted with a 2,700-million candlepower spotlight taking up most of the space in the nose housing. Up to 10 squadrons and 18 months of valuable time and resources went into this project which ultimately proved a failure.

In 1939, the USAAC returned to the DB-7 and re-evaluated its potential for use in the American military. The aircraft was given an extended life now with the initial order of 63 DB-7B platforms. The initial requirement of the USAAC specified a high-altitude capable airframe in the attack bomber role. As such, Douglas produced the design (designated as the A-20) with 2 x turbosupercharged R-2600-7 Wright Cyclone radial engines of 1,700 horsepower each. These initial A-20s were to feature a battery of 4 x 7.62mm (.30 caliber) machine guns in fuselage blister positions. An additional 2 x 7.62mm machine guns would be manned from a dorsal position while a single 7.62mm machine gun was allotted to a manned ventral gun position. Interestingly, rearward-firing 7.62mm machine guns were also introduced in this design, with these being mounted in each engine nacelle. Bombload was a reported 1,600lbs of internal ordnance. Crew personnel amounted to four specialists - a pilot, navigator, bombardier (in a glassed-in nose position) and gunner. Performance specs allowed for a top speed of 385 miles per hour (comparable to fighter performance) and a ceiling of up to 31,500 feet and range totaling some 1,100 miles (ferry range).

After the first A-20 was produced in this fashion, the Air Corps came back with a "modest" change to the requirement, deleting the need for a dedicated high-altitude platform and instead centering on a design capable of handling operations in a low-to-medium altitude zone. As such, the design was revisited and had its turbo-superchargers rightfully removed as they posed no performance benefits at lower operating levels. With the first A-20 completed to the high-altitude specification, the remaining aircraft on order followed this new design direction.

The initial A-20 did go on to serve as the developmental prototype form of the XP-70, the basis for the P-70 dedicated night-fighter. This single A-20 was modified to an extent, having its Wright Cyclone engines changed out for a different model version in the engine series and the problematic turbosuperchargers removed altogether, the latter causing some cooling issues.

143 total contracted A-20A models (based on the DB-7B) were introduced, first as an initial batch of 123 followed up by a smaller batch of 20 more. Differences between the A-20A and the original A-20 model were subtle yet distinct. The most prominent change occurred in the selection of a new Wright R-2600-3/-11 series engines of 1,600 horsepower each (sans the turbosuperchargers required for high-altitude work). First flight of the model was achieved on September 16th, 1940 and saw first deliveries to the 3rd Bomb Group by early 1941. Smaller issue numbers also were allotted to Panamanian and Hawaiian stations as well, extending the types reach somewhat. Armament of A-20A models included the 4 x 7.62mm forward-firing machine guns in fuselage blisters, 2 x 7.62mm machine guns in the dorsal position, 1 x 7.62mm machine gun in the ventral position and the 2 x 7.62mm rear-firing machine guns in fixed engine nacelle positions. Additionally, 1,600lbs of internal ordnance could be carried. The crew remained the initial four personnel as in the base A-20 design. Performance allowed for a top speed of 347 miles per hour, a ceiling of 28,175 feet and an operating range of 1,000 miles.

By October of 1940, the USAAC went on order for more Havocs, these being in the newer A-20B model form based on the DB-7A). The A-20B retained its twin engine light attack bomber role along with the A-model's R-2600-11 series radials and glassed-in nose, framed like that of a greenhouse. A slight variation in the design of this nose glass was the most discerning factor between distinguishing the A-20A and A-20B models. Additionally, armament was lessened to an extent, with the A-20B mounting just 2 x 12.7mm nose-mounted (lower fuselage) machine guns, 1 x 12.7mm machine gun in the dorsal position, 1 x 7.62mm machine gun in the ventral position and the two engine nacelle-mounted rear-firing 7.62mm machine guns. To make up for the lessened offensive firepower, the internal bombload was increased to 2,400lbs. Performance remained comparable with the top speed reported at 350 miles per hour, a range of 2,300 miles and a ceiling of 28,500 feet. The US Navy received eight such aircraft but used them in the target towing role as BD-2's. The Soviet Union became a large operator of the A-20B series under the Lend-Lease program, receiving 665 of the 999 production examples under the agreement.

The A-20C model appeared as an "improved" A-20A model. C-models brought back the cluster of 4 x 7.62mm lower-fuselage nose-mounted armament. 2 x 7.62mm machine guns were appropriated to the dorsal aft gun position along with a 7.62mm machine gun in a flexible ventral tunnel mount. Bombload was an impressive 2,400lbs though this could be supplemented by an internally-held fuel supply instead, increasing the aircrafts range somewhat. Additional improvements over the A-models included self-sealing fuel tanks (almost a prerequisite of any aircraft design going into the Second World War), improved armor plating for improved crew protection and 2 x Wright R-2600-23 Cyclone radial engines of 1,600 horsepower each. A crew of four was still required to operate the light attack bomber. Despite these additions and the aircraft proving heavier than preceding models, the A-20C saw only a slight reduction to overall speed. Performance included a top speed of 342 miles per hour, a range of 2,300 miles and a reduced ceiling of 25,320 feet. 948 examples of the A-20C were produced with these ear-marked for Britain (under designations Boston Mk.III and Boston Mk.IIIa) and Russia under Lend-Lease. However, the American need for such a platform was growing evermore and, as such, the a bulk of these were retained for American use. At least 140 A-20C models were produced by Boeing at their Seattle, Washington plant. Douglas handled the production of their 808 A-20C's at their Santa Monica, California facility.

The A-20D model appeared as a proposed high-altitude variant based on the A-20B. Once again, the idea of a turbosupercharged Wright Cyclone engine was entertained with equal results. The project was cancelled without any production taking place.

The A-20E represented converted A-20A models for use as utility use or developmental test airframes. These models were fitted with the Wright Cyclone R-2600-11 series engines as found on the later batch of A-20A production models (numbering some 20 such aircraft). A total of 17 A-20E converted models existed.

The XA-20F was a single A-20A model converted for use as a weapons test platform. These Havocs had a 37mm T-20-E-1 cannon mounted in a specially-designed nose assembly. General Electric powered turrets replaced the flexible gun mounts of the dorsal and ventral positions, each fitted with 2 x 12.7mm machine guns. Though relegated strictly to testbed use, the remote-controlled turrets were later a feature of the Douglas A-26 Invader series. This aircraft retained the Wright R-2600-3/-11 series of engines in its design.

The A-20G became the largest production run of the Havoc series, numbering some 2,850 total aircraft. The A-20G followed on the heels of the A-20C production model and was a dedicated ground attack platform as opposed to the light bomber designation carried by preceding models. The initial production A-20G block (259 total A-20G-1's) featured the distinctive solid nose assembly mounting 4 x 20mm cannons (deleting the bombardier's nose position and bringing the crew total down to three personnel). The follow-up production block (Block 5) reverted back to a more conventional array of 6 x 12.7mm machine guns as the cannons were prone to jamming and offered up a slow rate of fire. The cannon-armed versions were mostly operated under the Soviet banner via Lend-Lease and understandably proved quite devastating in the ground attack role. Additional armament for either form of this aircraft included 2 x 12.7mm machine guns in a flexible dorsal position and a single 7.62mm machine gun in the ventral position (flexible mount). Bombload totaled 2,000lbs of internally-held ordnance and/or 374-gallon drop tank. Engines for the aircraft were Wright R-2600-23 Cyclone supercharged radials of 1,600 horsepower each. Top speed was 317 miles per hour with a combat range of 950 miles and a modest ceiling of 23,700 feet.




Three A-20G blocks were represented via 50 total A-20G-5's, 300 total A-20G-10's and 150 total A-29G-15's. These held 4 x 12.7mm machine guns in the solid nose with additional 2 x 12.7mm machine guns to the lower forward portion of the fuselage (ala the A-20A, A-20B and A-20C models). The dorsal 12.7mm and ventral 7.62mm armament remained the same as in the A-20G Block 5 models. Block 10 and Block 15 incorporated other more subtle changes including increased armor protection based on operational feedback. Beginning with Block 20 (through Block 45), the dorsal 12.7mm armament on a flexible mount was upgraded to a powered-turret fitting. Four outboard under wing pylons were also added on a new reinforced wing.

The A-20H was a limited-production run model numbering 412 aircraft for use by American and Soviet forces (via Lend-Lease). These represented similar models to the A-20G (Block 45) but with more powerful engines allowing for shorter take-offs. Essentially, A-20H models were "improved" A-20G models with Wright R-2600-29 Cyclone supercharged radial engines of 1,700 horsepower each. By this time the R-2600-3 series was out of production.

A-20J models were "lead ship" variants with glassed-in nose assemblies as requested by the USAAC. These aircraft were pivotal in increasing the bombing accuracy of the solid nose A-20G models as they featured dedicated bombardiers complete with Norden bombsights and would often "lead" the other "sightless" bombers to the target, achieve the appropriate drop time via direct sighting and inevitably drop its bombload, signaling the other A-20's in the flight group to do the same. A-20J's were essentially the same aircraft with the exception of their nose construction. As might be expected, the 4 x 12.7mm machine guns were removed in the A-20J models to make room for the bombardier and his equipment. The 2 x 12.7mm lower-fuselage machine guns were, however, still kept as standard armament in the type those there were sometimes deleted in the field for the simple idea of saving weight. Total production of the A-20J was 450, built concurrently alongside the A-20G for ease. The A-20J was eventually replaced by the A-26C Invader aircraft, this airplane with its own glassed-in nose. A-20K models were similar in design and scope to A-20J models, serving as lead ships though based on the A-20H and mounting different engines (Wright R-2600-29 Cyclone radials of 1,700 horsepower).

The P-70 became the dedicated (albeit interim systems until the arrival of the Northrop P-61 Black Widows) night-fighter variants of the A-20 series. The P-70A featured AI radar in a solid nose along with 2 x Wright R-2600-11 radial engines of 1,600 horsepower. 39 P-70A-1's were delivered in 1943 to help combat Japanese night raids in the Pacific. Armament of these P-70A-1's included an under-fuselage pack containing 4 x 20mm cannons and two machine guns in the dorsal position. The former was later changed to 6 x 12.7mm machine guns in the nose. The P-70A-2 appeared as 65 converted forms from A-20G models but were basically similar to the P-20A-1's without the rear defensive machine guns. The P-70B-2 followed and was a night-fighter trainer platform appearing as 105 converted A-20G and A-20J models with American-made SCR-720/-729 series radar systems.

The CA-20 was another notable variant, these being A-20's converted for general transportation roles as the newer A-26 Invader took more and more of the A-20's role away from it. These aircraft astoundingly served into the 1960's.

Like the British before them, the Americans subjected the A-20 airframe to a series of experiments. Jet Assisted Take Off (JATO) was a popular experimental approach to most any airframe during the war and the A-20 was no exception. GALCIT JATO units were installed in the aft portion of each engine nacelle and tested in April of 1942. A reconnaissance attempt produced an A-20 with a K-24 camera system mounted in the tail. One A-20 had her nose armament removed in favor of a trial 4 x gun blister package attached to the fuselage sides. Another more interesting experiment saw an A-20 with her main landing gears converted to tractor-style tracks for operations in mud, snow and generally any surface unusable by traditional aircraft. Needless to say, these aircraft served as nothing more than experiments with most going the way of the dodo, though some still serving a viable research-minded purpose nonetheless.

Design

The basic A-20 design featured a deep cylindrical fuselage with middle mounted cantilever monoplane wings, each containing a radial three-propeller engine slung under the wing in an extended engine nacelle. The empennage was traditional, sporting a single vertical stabilizer and cantilever horizontal planes. The undercarriage was of a tricycle arrangement with two main wheels recessing into each engine nacelle and a nose gear with a single wheel recessing rearwards just under the cockpit floor. The engine nacelles on either wing assembly came to a point well past the wing trailing edge, giving the A-20 its distinct top-down silhouette. A rear gunnery/observation position was set at the top of the base of the empennage while a ventral gun "tunnel" position could also be utilized. The cockpit provided good views all around and helped offer up the feel of the A-20 as a fighter more than a bomber. In all, the aircraft proved structurally sound and suited to the work bestowed upon it, proving a success for the Douglas company as well. Like many of the larger aircraft in the Second World War, the airframe of the Havoc was duly noted for its ability to withstand a great deal of damage while keeping her crews alive. Additionally, the airframe proved quite adaptable by a variety of users utilizing a variety of armament and internal systems. Power for the type was provided by a long line of Wright radial series engines of various power specifications.

Armament

Armament varied throughout the course of the aircraft's production life, particularly when basing it on the operator. Standard fare included a battery of 4 x 12.7mm machine guns housed in a solid nose supplying the aircrafts offensive forward "punch" along with a dorsal position mounting a flexible machine gun (or a pair of such weapons). Additionally, this punch could be enhanced through the use of internally held bombs - a bombload of up to 4,000lbs - which a portion of this load could be used for additional fuel. It was not uncommon for the nose-mounted armament to be increased in the form of 6 x 12.7mm machine guns for a truly imposing forward-strike potential. Other armament included a pair of defensive 12.7mm machine guns held in the rear cockpit and a single 12.7mm machine gun in a ventral position reached via a tunnel. Blister gun packs were not uncommon as were lower-fuselage 12.7mm machine guns. 4 x 20mm cannons were attempted in the solid nose assembly as was a 1 x 37mm cannon arrangement.

Cockpit

As with any aircraft, the cockpit of the A-20 series was the heart of the plane. One must keep in mind that the A-20 was really designed as a light bomber, though it was piloted by just one personnel in the single-seat cockpit and was, for all intents and purposes, designed as a heavy fighter. The cockpit was positioned forward in the design with a glazed canopy, offering up stellar views forward, above and to the sides (including rear sides). The framed canopy door swung open on a hinge mounted along the starboard side of the frame and allowed for easy entry and exit from the seat. Maneuvering the aircraft was accomplished through a traditional control wheel mounted on a flexible column. The gun button was fitted to the top right portion of the control wheel for easy access. Throttle, mixture and propeller controls were fitted in a cluster to the left side of the seat as were the various electrical switches. The main board was noted for its well-placed dials and gauges. Fuel tank controls, bomb selector, radio and cockpit heating functions were placed to the right of the pilot's seat. In all, the cockpit was approved of by both American and British airmen alike. If there was any complaint from pilots, it was in the use of framing for the cockpit window, restricting viewing to some extent, particularly in poor weather.

Operational Service

A-20's served in Pacific and European Theaters of War. The 3rd, 312th and 417th Bomb Groups represented Havoc use in the Pacific whilst the 47th, 409th, 410th and 416th Bomb Groups utilized the type in an early limited role in Europe. Operations in the latter were held by the 9th Air Force with the 9th Bomber Command. On July 4th, 1942, twelve A-20 Havocs (6 with American airmen and 6 with British airmen) launched a low-altitude daylight bombing raid on four Dutch airfields marking the first such US raid in the European Theater. These American-flown Havocs were part of the 15th Bombardment Squadron.

A-20's converted as interim night-fighters became the P-70. P-70 Havocs were sent in bulk to the 18th Fighter Group and saw action in support of ground forces over Guadalcanal, Bougainville and the Solomons. P-70's were eventually replaced by the newer and more capable Northrop P-61 Black Widows beginning service in 1944. Black Widows offered up improved overall performance, impressive cannon/machine gun firepower and high-altitude performance and was a dedicated platform specifically designed for night operations.

Soviet forces were the other real major operator of the aircraft, making headway with the platform as a ground attack fighter by bringing its impressive nose-mounted armament to bear on unsuspecting ground foes. Additional actions saw the A-20 operating in the Middle East and North Africa.

Production of any A-20 system was ended in September of 1944 after which some 7,385 to 7,478 were produced.

Conclusion

The A-20 proved a little aircraft of large worth. The ability for the system to adapt to various armament configurations allowed for the type to reach further and deeper into the war than it would have otherwise. The Havoc proved to provide its operators with a sturdy and powerful attack platform capable of under taking a variety of specialized roles from ground attack to light bombing and strafing as needed. In any form, A-20 Havocs proved that "tweener" type, twin-engine designs still had a place in a war dotted with sleek fighters and heavy bombers.



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Douglas A-20G Havoc Technical Specifications



Service Year: 1941
Type: Light Bomber / Night-Fighter Aircraft
National Origin: United States
Manufacturer(s): Douglas Aircraft Company - USA
Production Total: 7,478


Structural (Crew Space, Dimensions and Weights)



Operating Crew (Typical): 3
Overall Length: 48.00 feet (14.63 meters)
Overall Width: 61.32 feet (18.69 meters)
Overall Height: 17.59 feet (5.36 meters)

Weight (Empty): 15,984 lb (7,250 kg)
Weight (MTOW): 27,201 lb (12,338 kg)

Cockpit Image



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Installed Power and Standard Day Performance



Propulsion: 2 x Wright Cyclone R-2600-23 14-cylinder air-cooled radial piston engines developing 1,600 horsepower.

Maximum Speed: 339 mph (545 kph; 294 knots)
Maximum Range: 1,091 miles (1,755 km)
Service Ceiling: 25,098 feet (7,650 meters; 4.75 miles)
Rate-of-Climb: 1,500 feet-per-minute (457 m/min)

Armament / Mission Payload



Dependent upon specific Havoc Model. Can include:

4, 6 OR 8 x 12.7mm machine guns in nose
4 x 20mm cannons in nose

OPTIONAL:
2 x 12.7mm machine guns in lower-fuselage position.
2 x 7.62mm OR 12.7mm machine guns in flexible rear dorsal position.
1 x 7.62mm OR 12.7mm machine gun in flexible ventral position.
4 x 7.62mm machine guns in fuselage blisters (2 to a side).
6 x 12.7mm machine guns in fuselage blisters (3 to a side).
2 x 7.62mm machine guns in fixed rear-firing engine nacelle positions (1 per nacelle).

1,600lbs to 4,000lbs of bombs including four held in an internal bay and (later) two external pylons outboard of the nacelles.

1 x 374-gallon fuel tank in place of some of the internally-held bombs.

Global Operators / Customers



Australia; Brazil; Canada; France; Netherlands; New Zealand; South Africa; Soviet Union; United Kingdom; United States

Model Variants (Including Prototypes)



Model 7 - Private Douglas venture design to replace current US Army single-engine attack aircraft.
Model 7A - Proposed light bomber with improved 450hp radial engines.
Model 7B - Followup proposed light bomber with Pratt & Whitney R-1830 radial engines devlivering 1,100hp.
DB-7 - (Douglas Bomber 7) Original French order placed featuring R-1830-S3C4-G radial engines and longer fuselage.
DB-7A - Wright R-2600-A5B radial engines; Improved variant.
DB-7B - Redesigned with British equipment; Enlarged vertical tail surface structure; Redesignated Boston Mk III.
DB-73
DB-7C
A-20A - Initial production model to go in service with Britain and Commonwealth nations; "Havoc" name officially adopted; 143 examples produced.
A-20B - First major order in terms of overall numbers for Soviet Lend-Lease Act; 999 produced.
A-20C - "Improved" A-20A model; 4 x 7.62mm machine guns in nose; improved Wright engines of 1,600 horsepower; self-sealing fuel tanks; increased armor plating; 948 total produced by/for Douglas including 140 by Boeing.
A-20D - Proposed high-altitude version; intended powerplant of turbosupercharged Wright Cyclone radial engines; canceled before production.
A-20E - Test Models converted from A-20A models; all fitted with Wright R-2600-11 Cyclone engines; 17 total conversion ecamples.
XA-20F - Single A-20A model example set aside for nose armament and powered-turret tests; 1 x37mm nose cannon trialed along with 2 x 12.7mm machine guns in powered dorsal and ventral turrets.
A-20G - Sans-bomb aimer in nose; Solid nose with 8 x machine gun battery; Highest production rate of entire A-20 series; production blocks of A-20G-5 to A-20G-15, A-20G-20 to A-20G-45 with various minor changes throughout; 2,850 examples produced.
A-20H - Similar to A-20G-45 block model with increased MTOW and upgraded engines (Wright R-2600-29 series radials); 412 examples produced.
A-20J - "Lead Ship" aircraft model based on A-20G with glassed-in nose and bombardier position; 450 examples produced.
A-20K - "Lead Ship" aircraft model with glassed-in nose and bombardier position based on A-20H models; improved powerplant, improved armament capabilities and updated onboard equipment; Represents final production version; 413 examples produced.
Boston Mk.I - British redesignation of DB-7.
Boston Mk.II - British redesignation of DB-7A.
Boston Mk.III - British redesignation of DB-7B; DB-7B model with enlarged vertical tail surface and featuring British equipment internally.
Boston Mk.IIIa - A-20C models via Lend-Lease
Boston Mk.IV
Boston Mk.V
XP-70 - Converted A-20 to Night-fighter with glass-nose section painted black housing 4 x 20mm cannons.
P-70 - Night-fighter Variant Conversion base model.
P-70A-1 - Converted A-20C model to Night-fighter role.
P-70A-1 - Converted A-20G model to Night-fighter role.
P-70B-1 - Converted A-20G-10-DO Night-fighter.
P-70B-2 - A-20G / A-20J converted trainers for Northrop P-61 crewmembers.
F-3 - Base A-20 conversion to Night-time photography and reconnaissance.
F-3A - Night-time Photography and Reconnaissance Conversion of A-20J and A-20K models.