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 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.
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.
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.
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.
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.
|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|
|Total 6310||1,449 in UK, 4,846 in USA and 15 built in 1926 by SABCA in Belgium|
|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.|
|DH-4||Two-seat day bomber|
|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-3||Fitted with 135 US gal fuel tank|
|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-4M||Rebuilt version of DH-4 with steel tube fuselage.|
|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|
National Air and Space Museum in Washington DC
|DH-4B||National Postal Museum in Washington, DC|
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|
Fantasy of Flight in Polk City, Florida
|DH-4M-1||Evergreen Aviation and Space Museum in McMinnville, Oregon|
|DH-4M-2A||Historic Aircraft Restoration Museum in Maryland Heights, Missouri www.historicaircraftrestorationmuseum.org/|
Omaka Aviation Heritage Centre in Blenheim, New Zealand
Museo del Aire in Madrid, Spain