The Aircraft Manufacturing Company (Airco) 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 Geoffery de Havilland at the controls. After testing trials at Upavon and later at Martlesham Heath, it entered Royal Flying Corps (RFC) service on 6th March 1917, with No. 55 Squadron based in France.
The Airco 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 defensive armament, with a forward firing Vickers 0.303 mm machine gun for use by the pilot, plus 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, together with creating difficulties when operating from rough ground. The undercarriage struts were therefore lengthened on all later production aircraft.
Power was initially provided in the prototype by the 230hp BHP engine, although several other engine types such as the Siddeley Puma, Fiat and RAF 3A were later fitted. Of these alternative engines, the 375hp Rolls-Royce Eagle VIII is regarded as being the most successful. Unfortunately, Rolls-Royce Eagle engines were in short supply and so production units built U.S. aircraft were powered by the 400 hp Liberty L-12 engine (which was later adopted for the Airco DH9A model) which was also used in American automobiles.
A later US-built derivative, the DH4M featured a fabric-covered steel tube fuselage.
The Airco DH4 proved very popular in service, not least for its speed and climb performance, manoeuvrability and pleasant flying characteristics.
1,449 Airco DH4 aircraft were built in the UK, some 915 of which were constructed at the Aircraft Manufacturing Works at the Hyde 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 Company and Standard Aircraft. Rather strangely however, 15 aircraft were also made by Sociétés Anonyme Belge de Constructions Aéronautiques (SABCA) in Belgium during 1926, long after the aircraft retired from military service.
In USA, the type was designated Airco DH4A and Airco DH4B, with a wide range of designations applied to various mainly experimental developments. In the Airco 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 and Vulcan Motor & Engineering, as well as Westland Aircraft Works. It was also proposed that a factory be set up in Russia to build Airco DH4s although the Russian Revolution of October 1917 resulted in these plans being abandoned.
Many Airco DH4s were used for experimental flying, such as in engine test work, both in the UK and the USA. Post-war, a single seat racing variant with cropped lower wings (Airco DH4R) won the 1919 Aerial Derby air race.
The Airco 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 and Air Mail services in the UK and Australia as well as being particularly important to the US Postal Department. The majority of the US Mail aircraft were actually converted to single seaters, with the mail carried in a watertight compartment in the space previously occupied by the front cockpit.
The Airco DH4A commercial variant had a small glazed cabin in the rear fuselage in which two passengers could be seated. Operators included AT & T Ltd, who operated the service between Hounslow Heath Aerodrome and Paris Le Bourget. Other aircraft were operated by SNETA (Belgium), Handley Page Ltd and Instone Air Lines. In the southern hemisphere, the emerging Australian concern Qantas used the Airco DH4A for its first airmail service in 1922.
The DH4 eventually formed the basis for the Airco DH9 and Airco 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|
|Airco DH4||Two-seat day bomber|
|Airco DH4A||Civil version. Two passengers in cabin behind pilot|
|Airco DH4R||Single seat racing version with 450 hp Napier Lion engine.|
|Airco DH4||Two-seat day bomber|
|Airco DH4A||Civil version|
|Airco DH4B||Liberty powered Airco DH4 for U.S. Air Service. Pilot's cockpit moved to rear of fuel tank|
|Airco DH4B-1||Increased fuel capacity (110 US gal)|
|Airco DH4B-2||Trainer version.|
|Airco DH4B-3||Fitted with 135 US gal fuel tank|
|Airco DH4B-4||Civil version|
|Airco DH4B-5||Experimental civil conversion with enclosed cabin.|
|Airco DH4BD||Crop-dusting version of Airco DH4B|
|Airco DH4BG||Fitted with smoke generators|
|Airco DH4BK||Night flying version|
|Airco DH4BM||Single seat version for communications|
|Airco DH4BM-1||Dual control version of BM|
|Airco DH4BM-2||Dual control version of BM|
|Airco DH4-BP||Experimental photo reconnaissance version|
|Airco DH4-BP-1||BP converted for survey work|
|Airco DH4BS||Testbed for supercharged Liberty engine|
|Airco DH4BT||Dual control trainer|
|Airco DH4BW||Testbed for Wright H engine|
|Airco DH4C||300 hp (220 kW) Packard engine|
|Airco DH4L||Civil version|
|Airco DH4M||Rebuilt version of Airco DH4 with steel tube fuselage.|
|Airco DH4Amb||Ambulance conversion|
|Airco DH4M-1||Postwar version by Boeing (Model 16) with new fuselage, Navy O2B-1|
|Airco DH4M-1T||Dual control trainer conversion of Airco DH4M|
|Airco DH4M-1K||Target tug conversion|
|O2B-2||Cross-country and night flying conversion for Navy|
|Airco DH4M-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
|Airco DH4B||National Postal Museum in Washington, DC|
National Museum of the Marine Corps in Triangle, Virginia
|Airco DH4B||Under restoration for the Pearson Air Museum in Vancouver, Washington www.nps.gov/fova/learn/historyculture/pearson.htm|
|Airco DH4B||National Museum of the United States Air Force in Dayton, Ohio|
Fantasy of Flight in Polk City, Florida
|Airco DH4M-1||Evergreen Aviation and Space Museum in McMinnville, Oregon|
|Airco DH4M-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