Armament & payload

The DH.4 outran what chased it, and its most famous enemy was the petrol tank sitting between the two men flying it

On paper the armament is unremarkable for 1917: one or two synchronised Vickers ahead of the pilot, one or two Lewis on a Scarff ring behind, and 460 lb of bombs on external racks. The real weapon was 143 mph. A DH.4 that had dropped its bombs could usually leave a 1917 German single-seater behind, which is why it often flew without escort at all and why No. 55 Squadron came through Bloody April largely intact while most of the RFC was being slaughtered. It is a very fair claim that this was the best single-engine day bomber of the war.

Against that stands the flaw everybody knows about, which is not strictly an armament question and is dealt with here because it is always the first thing asked. The 55-gallon main tank sat between the two cockpits. The crew could not talk to each other, which in a fight is worse than it sounds; and the American aircraft acquired the nickname "Flaming Coffin", which the surviving statistics support less firmly than the phrase suggests. Naval aircraft, American Liberty aircraft and postwar rebuilds all differed in gun fit and tank arrangement; nearly every generalisation below has an exception in one of them.

Sourcing caveat: the DH.4 is well documented and still disagrees with itself. The 143 mph figure is stated for sea level, which is more than most period tables offer, but almost no source gives a comparable speed at 10,000 or 15,000 ft for the Eagle VIII aircraft, so the fighting speed at height has to be inferred. Span is published as 43 ft 4 in and as 42 ft 5.625 in, height as 11 ft 0 in and 10 ft 1 in, empty weight across marks as 2,197 to 2,387 lb, ceiling as 16,000 to 22,000 ft and endurance as 3½ to 4½ hours. The Eagle VIII is rated at 375, 360 and 300 hp by three respectable authorities. Production figures are firmer — 6,295 total, 4,846 American, 1,449 British — but should be read against 9,500 aircraft ordered in the United States and only 1,885 reaching France, which is the more revealing pair of numbers. The Gorrell fire statistic is quoted here because it is the only quantitative evidence there is, not because eight losses out of thirty-three settle anything.

Variants

The DH.4 was a British bomber that became an American institution, and then spent a decade carrying the post

The British variant list is short because the British aeroplane barely changed: one basic day bomber, a succession of engines forced on it by supply rather than chosen, a naval version with two forward guns, and a cabin conversion built so that ministers could talk on the way to the Paris Peace Conference. British production stopped early and for a bad reason. Trenchard and others decided at the end of 1917 that the DH.4 was obsolete and switched production to the DH.9, which had the tank in the right place and an engine that could not lift it. The DH.9 was worse than the aeroplane it replaced in almost every respect, and it took the American Liberty engine and the DH.9A to put things right.

The American story is a different order of magnitude. When the United States entered the war in April 1917 its Signal Corps had no aircraft fit for combat at all. The Bolling Commission chose four foreign types to build; the DH.4 was one, and it was the only one that actually reached the front in American-built form. Dayton-Wright, Fisher Body, Standard Aircraft and Boeing built 4,846 of them with over a thousand modifications from the British drawings, around the new 400 hp Liberty. It was the only American-built aeroplane to see combat in the First World War, and the fact that America's entire wartime aircraft industry produced exactly one combat type, and that a British design, is the most eloquent thing anybody can say about the state of American aviation in 1917.

Then came the strangest chapter. At the Armistice there were more than a thousand Liberty Planes in France and a flood of improved DH-4Bs coming off American production lines. Shipping the old ones home cost more than they were worth, so they were burned in France together with other surplus machines in the episode remembered as the "Billion Dollar Bonfire". The survivors at home were rebuilt as DH-4Bs, with the pilot moved aft next to his observer, and became the standard American general-purpose aeroplane of the 1920s: observation, ambulance, photographic, crop-dusting, smoke-laying, target-towing, engine testbed. The DH-4 flew the first successful air-to-air refuelling on 27 June 1923 and, later that summer, a 37-hour endurance flight with sixteen refuellings that set sixteen world records. Jimmy Doolittle crossed the United States in one in 21 hours 19 minutes on 4 September 1922 with a single fuel stop. The US Army Air Corps did not retire the type until 1932.

Its most durable civil career was the mail. The US Post Office took a hundred DH-4s from the Army and rebuilt them to the safer DH-4B standard, and from 21 August 1924 flew them on the transcontinental route between New York and San Francisco — 2,680 miles, at night, with bonfires along the route for navigation — until the last contracts passed to private carriers in 1927. Canada took twelve DH.4s as part of the Imperial Gift and used them on forestry patrol and survey, spotting hundreds of forest fires and, on the Air Board's accounting, saving millions of dollars in timber, with the last withdrawn in 1927. In Europe the same airframes opened commercial aviation: a DH.4A of Aircraft Transport and Travel flew Britain's first commercial passenger service from Hounslow Heath to Le Bourget on 25 August 1919, carrying a reporter, some newspapers and a consignment of grouse. QANTAS flew its first airmail on a DH.4 in 1922. A war-surplus bomber going cheap turned out to be the aeroplane that started civil aviation almost everywhere it landed.

DH.4 (1917–18 / 1,449 of 1,700 ordered)

British production by Airco, F. W. Berwick, Glendower Aircraft, Palladium Autocars, Vulcan Motor and Engineering and Westland. One Vickers forward, one or two Lewis aft, 460 lb of bombs.

DH.4, alternative engines (1917–18)

200 hp RAF 3a, issued to No. 18 Squadron in June 1917 and a failure; 230 hp BHP and Siddeley Puma; 260 hp Fiat A-12 in the batch built for Russia and retained by the RFC. All markedly slower than the Eagle aircraft.

Admiralty DH.4 (1917–18 / 90 plus 16)

Ninety built by Westland to Admiralty specification with two forward Vickers and a raised Scarff ring, plus sixteen transferred from War Office orders. Flew with five RNAS squadrons in Belgium, three coastal stations, four squadrons in the Aegean and three in Italy.

DH.4A (1919 / 16)

Cabin transport with two passengers in a glazed enclosure behind the pilot, built at Bonar Law's request for the Paris Peace Conference. Seven for the RAF's No. 2 Communication Squadron and nine for civil use; one was Lloyd George's regular aeroplane, probably the first used routinely by a head of government.

DH.4R (1919 / 1)

Single-seat racer with a 450 hp Napier Lion, built for the postwar racing circuit.

DH-4 "Liberty Plane" (1918 / 4,846 of 9,500 ordered)

American production by Dayton-Wright, Fisher Body, Standard Aircraft and Boeing with more than a thousand design changes, 400 hp Liberty L-12, two Marlin-Rockwell guns forward and two Lewis aft, 322 lb of bombs. 1,885 reached France; the only American-built aeroplane to see combat in the war.

DH-4B and sub-variants (1919–25 / many hundreds rebuilt)

The important American rebuild: pilot moved aft alongside the observer with the tank ahead of him. B-1 to B-5 covered extra fuel, training, civil and cabin work; BD crop-duster, BG smoke-layer, BK night flyer, BP photographic, BS supercharger testbed, BT trainer, BW engine testbed. Boeing alone delivered 111 in 1920.

DH-4M-1, DH-4M-2 and O2B (1923–25 / 163 plus a second batch)

Welded steel-tube fuselage in place of the wooden one: Boeing's Model 16 as the DH-4M-1, Atlantic Aircraft's as the DH-4M-2. Twenty-two M-1s became dual-control trainers and a few target tugs; thirty were diverted to the Marine Corps as the O2B-1, which served until 1929.

L.W.F. J-2 "Twin DH" (1919–20 / 30)

Twin-engine long-range development with a 52 ft 6 in span and two 200 hp Hall-Scott Liberty L-6 engines. Twenty for the US Post Office and ten for the Army.

Foreign, licence and gift aircraft (1918–32)

SABCA built 15 in Belgium in 1926; Polikarpov copied the type at the former Dux factory in the 1920s. Imperial Gift aircraft went to Canada (12), New Zealand (2), South Africa and Australia. Military service also with Chile, Cuba, Greece, Iran, Mexico, Nicaragua, Spain and Turkey, some into the early 1930s.

Survivors, stated precisely, because the distinction between an original airframe and a reproduction matters more here than the count — and because for this type it also decides the nationality. Every original DH.4 known to survive is American-built. The prototype American-built DH-4 is at the National Air and Space Museum in Washington; there is a DH-4 at the National Museum of the Marine Corps, one at the Omaka Aviation Heritage Centre in New Zealand, and airframe 32517 under reconstruction in Wichita as a memorial to Erwin Bleckley. Of the DH-4B rebuilds, examples are on display at the National Postal Museum in Washington, the National Museum of the United States Air Force at Dayton, the Pearson Air Museum in Vancouver, Washington, and Fantasy of Flight in Florida, with another in restoration. A DH-4M-1 is at the Evergreen museum in Oregon, and a DH-4M-2A is airworthy at the Historic Aircraft Restoration Museum in Missouri. What is missing from that list is the aeroplane that earned the reputation: no original British-built Airco DH.4 is known to survive anywhere, not one of the 1,449 that the RFC, RNAS and RAF flew, and not one Rolls-Royce Eagle VIII installation in an original airframe. The flying DH.4 in the world today is a reproduction — The Vintage Aviator's aircraft at Masterton in New Zealand, built by Century Aviation around a rebuilt Liberty V-12 — and there is a static reproduction at the Museo del Aire in Madrid. So the DH.4 that is preserved is almost entirely the American Liberty Plane, which is fair enough given where most were built and where they went on working for another decade, and slightly unfair to the Eagle-engined British aeroplane that actually did the fighting.

Airco DH.4 operations map: origin, wartime fronts and surviving airframes