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Airco DH4

One of the best single engine bombers of the First World War that also played a role in the development of commercial air services.
Airco DH4 prototype 3696 at Hendon in August 1916 Airco DH4 prototype 3696 at Hendon in August 1916.
 
The DH4 (No3696) was a two-seat biplane day bomber of the first World War.  It first flew at Hendon in August 1916 with its designer Geoffrey de Havilland at the controls.  After testing trials at Upavon and later at Martlesham Heath, it entered RFC service on 6th March 1917 with No. 55 Squadron based in France.
 
The DH4 had open cockpits with the crew being separated by the fuel tank installed between them in the fuselage which meant that a speaking tube was required for communications. It was the first day bomber to have deffensive armanment with a forward firing Vickers 0.303 mm machine gun for use by the pilot and a 0.303 Lewis gun (sometime 2 guns) fitted on a Scarff ring for the observer. Two 230lb or four 112lb bombs could also be carried.
 
Early production Airco DH4 with short undercarriage Early production Airco DH4 with short undercarriage legs.
 
Early aircraft featured fairly short undercarriage legs, which resulted in a low propeller clearance on take-off and created difficultings when operating from rough ground. The undercarriage struts were therefore lengthened on all later production aircraft.
 
Power was initially provided by the 230hp BHP engine in the prototype but several other engine types such as the Puma, Fiat and RAF 3A were fitted although the 375hp Rolls-Royce Eagle VIII is regarded as being the most successful.  Unfortunately Eagle engines were in short supply and the U.S. production units were fitted with the Liberty engine which was also used in American automobiles.
 
American-built aircraft were powered by the 400 hp Liberty L-12 engine, which was later adopted for the DH9A model. A later US-built derivative, the DH4M featured a fabric-covered steel tube fuselage.
 
Airco DH4 with Rolls-Royce Eagle engine Airco DH4 with Rolls-Royce Eagle engine.
 
The type proved very popular in service not least for its speed and climb performance, manoeuvrability and pleasant flying characteristics.
 
1,449 DH4 were built in the UK with some 915 being constructed by AIRCO in Hendon. A further substantial number (4,846 from planned orders of up to 9,500) were built in the USA by Boeing, Dayton-Wright, Fisher Body and Standard Aircraft. Rather strangely, 15 aircraft were made by SABCA in Belgium during 1926, long after the aircraft retired from miltary service.
 
In USA, the type was designated DH4A and DH4B with a wide range of designations applied to various mainly experimental developments. In the DH4B version, the pilot’s cockpit was moved to the rear to be adjacent to that of the gunner.
 
Airco DH-4B AS23-669 Airco DH-4B AS23-669 showing revised cockpit layout. This aircraft is fitted with wings from a Loening COA-1 amphibian.
 
British sub-contract orders were also placed with F.W. Berwick, Glendower Aircraft, Palladium Autocars Ltd, Vulcan Motor & Engineering as well as Westland Aircraft Works. It was also proposed that a factory be set up in Russia to build DH4’s although the Russian Revolution of October 1917 resulted in these plans being abandoned.
 
Many DH4s were used for experimental flying such as engine test work, both in the UK and the USA and post-war, a single seat racing variant with cropped lower wings (DH4R) won the 1919 Aerial Derby air race. 
 
Airco DH4R Racer K-141 The one-off Airco DH4R Racer K-141 set a closed circuit speed record of 129.3 mph.
 
The DH4 was employed in a large number of roles, with variants that included crop-duster, ambulance and target-tug adaptations, as well as numerous training and commercial developments.
 
After the war, the type, and its derivatives, played an important role in initiating commercial passenger (in UK and Australia) and mail services, the latter particularly with the US Postal Department. The majority of these US Mail aircraft were converted to single seaters, with the mail carried in a watertight compartment in the space previously occupied by the front cockpit.
 
RAF Airco DH4A on ground One of seven DH4s converted to DH4A configuration for RAF use in 1919.
 
The DH4A commercial variant had a small glazed cabin in the rear fuselage in which two passengers could be seated and operators included AT&T Ltd who operated between Hounslow Heath Aerodrome and Paris Le Bourget.
 
Other aircraft were operated by SNETA (Belgium), Handley Page Ltd and Instone Air Lines as well as emerging the emerging Australian concern Qantas for its first airmail service in 1922.
 
The DH4 formed the basis for the DH9 and DH9A, of which a further total of more than 6,000 aircraft were built.

Specification

Powerplant One 375 hp Rolls-Royce Eagle VIII
Span 42 ft 4.6 in
Maximum Weight 3,472 lb
Capacity and armament Pilot and observer. Forward firing Vickers gun and one or two Lewis guns on a Scarff mounting. Typical bomb load 450 lb (four 112 lb or two 230 lb bombs)
Maximum Speed 143 mph at sea level
Endurance 3.75 hr 

Number built

Total 6310 1,449 in UK, 4,846 in USA and 15 built in 1926 by SABCA in Belgium

Variants

UK Variants
DH4                         Two-seat day bomber 
DH4A Civil version. Two passengers in cabin behind pilot
DH4R Single seat racing version with 450 hp Napier Lion engine.
US Variants
DH-4  Two-seat day bomber 
DH-4A  Civil version
DH-4B  Liberty powered DH-4 for U.S. Air Service. Pilot's cockpit moved to rear of fuel tank 
DH-4B-1  Increased fuel capacity (110 US gal)
DH-4B-2  Trainer version.
DH-4B-3  Fitted with 135 US gal fuel tank
DH-4B-4  Civil version
DH-4B-5  Experimental civil conversion with enclosed cabin.
DH-4BD  Crop-dusting version of DH-4B
DH-4BG  Fitted with smoke generators
DH-4BK  Night flying version
DH-4BM Single seat version for communications 
DH-4BM-1  Dual control version of BM
DH-4BM-2  Dual control version of BM
DH-4-BP  Experimental photo reconnaissance version 
DH-4-BP-1  BP converted for survey work
DH-4BS  Testbed for supercharged Liberty engine
DH-4BT  Dual control trainer
DH-4BW  Testbed for Wright H engine
DH-4C  300 hp (220 kW) Packard engine
DH-4L  Civil version
DH-4M  Rebuilt version of DH-4 with steel tube fuselage.
DH-4Amb  Ambulance conversion
DH-4M-1 Postwar version by Boeing (Model 16) with new fuselage, Navy O2B-1 
DH-4M-1T Dual control trainer conversion of DH-4M
DH-4M-1K Target tug conversion
O2B-2 Cross-country and night flying conversion for Navy
DH-4M-2 Postwar version by Atlantic
XCO-7  (Boeing 42) Two-seat observation version with Boeing designed wings, enlarged tailplane and divided landing gear.
XCO-8 One Atlantic DH.4M-2 fitted with Loening COA-1 wings and a Liberty 12A engine

Survivors

DH-4
(21959)          
 National Air and Space Museum in Washington DC
DH-4B National Postal Museum in Washington, DC
DH-4
National Museum of the Marine Corps in Triangle, Virginia
DH-4B Under restoration for the Pearson Air Museum in Vancouver, Washington www.nps.gov/fova/learn/historyculture/pearson.htm
DH-4B National Museum of the United States Air Force in Dayton, Ohio

www.nationalmuseum.af.mil/

DH-4B
Fantasy of Flight in Polk City, Florida
DH-4M-1 Evergreen Aviation and Space Museum in McMinnville, Oregon

www.evergreenmuseum.org/

DH-4M-2A Historic Aircraft Restoration Museum in Maryland Heights, Missouri www.historicaircraftrestorationmuseum.org/
DH-4
Omaka Aviation Heritage Centre in Blenheim, New Zealand
DH4 
Museo del Aire in Madrid, Spain