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Subject: Airco DH.4
Date: 13 Jan 2017 14:28:50 -0800
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https://en.wikipedia.org/wiki/Airco_DH.4
The Airco DH.4 was a British two-seat biplane day bomber of World War I. It was
designed by Geoffrey de Havilland (hence "DH") for Airco, and was the first
British two-seat light day-bomber to have an effective defensive armament. It
first flew in August 1916 and entered service with the Royal Flying Corps (RFC)
in March 1917. The majority of DH.4s were actually built as general purpose
two-seaters in the United States, for service with the American forces in
France.
The DH.4 was tried with several engines, of which the best was the 375 hp (280
kW) Rolls-Royce Eagle engine. Armament and ordnance for the aircraft consisted
of one 0.303 in (7.7 mm) Vickers machine gun for the pilot and one 0.303 in (7.7
mm) Lewis gun on a Scarff ring mounting for the observer. Two 230 lb (100 kg)
bombs or four 112 lb (51 kg) bombs could be carried. The DH.4 entered service on
6 March 1917 with No. 55 Squadron in France.
The aircraft was a conventional tractor two bay biplane of all-wooden
construction. The crew of two were accommodated in widely spaced cockpits,
separated by the fuel tank. It was armed with a single forward-firing
synchronised Vickers machine gun and one or two .303 in (7.7 mm) Lewis guns
fitted on a Scarff ring fired by the observer. A bomb load of 460 lb (210 kg)
could be fitted to external racks. While the crew arrangement gave good fields
of view for the pilot and observer, it caused communication problems between the
two crew members, particularly in combat, where the speaking tube linking the
cockpits was of limited use.
As production continued, DH.4s were fitted with Eagle engines of increasing
power, settling on the 375 hp (280 kW) Eagle VIII, which powered the majority of
frontline DH.4s by the end of 1917. Because of the chronic shortage of
Rolls-Royce aero engines in general, and Eagles in particular, alternative
engines were also investigated, with the BHP (230 hp/170 kW), the Royal Aircraft
Factory RAF3A (200 hp/150 kW), the Siddeley Puma (230 hp/170 kW) and the 260 hp
(190 kW) Fiat, all being used in production aircraft. None of these engines
could match the Rolls-Royce Eagle; however, there were simply not enough Eagles
available.
Role
Light bomber / General purpose
Manufacturer
Airco
First flight
August 1916
Introduction
March 1917
Retired
1932 (United States Army)
Primary users
United Kingdom
United States
Number built
6295, of which 4846 were built in the United States.
Unit cost
$11,250
Variants
DH9, DH9A, Dayton-Wright Cabin Cruiser
British military service
The DH.4 entered service with the RFC in January 1917, first being used by No.
55 Squadron. More squadrons were equipped with the type to increase the bombing
capacity of the RFC, with two squadrons re-equipping in May, and a total of six
squadrons by the end of the year. As well as the RFC, the RNAS also used the
DH.4, both over France and over Italy and the Aegean front. The DH.4 was also
used for coastal patrols by the RNAS. One, crewed by the pilot Major Egbert
Cadbury and Captain Robert Leckie (later Air Vice-Marshal) as gunner, shot down
Zeppelin L70 on 5 August 1918. Four RNAS DH.4s were credited with sinking the
German U-boat UB 12 on 19 August 1918.
The DH.4 proved a huge success and was often considered the best single-engined
bomber of World War I. Even when fully loaded with bombs, with its reliability
and impressive performance, the type proved highly popular with its crews. The
Airco DH.4 was easy to fly, and especially when fitted with the Rolls-Royce
Eagle engine, its speed and altitude performance gave it a good deal of
invulnerability to German fighter interception, so that the DH.4 often did not
require a fighter escort on missions, a concept furthered by de Havilland in the
later Mosquito in World War II.
A drawback of the design was the distance between pilot and observer, as they
were separated by the large main fuel tank. This made communication between the
crew members difficult, especially in combat with enemy fighters. There was also
some controversy (especially in American service) that this placement of the
fuel tank was inherently unsafe. In fact, most contemporary aircraft were prone
to catching fire in the air. The fire hazard was reduced, however, when the
pressurised fuel system was replaced by one using wind-driven fuel pumps late in
1917, although this was not initially adopted by American-built aircraft. The
otherwise inferior DH.9 brought the pilot and observer closer together by
placing the fuel tank in the usual place, between the pilot and the engine.
Despite its success, numbers in service with the RFC actually started to decline
from spring 1918, mainly due to a shortage of engines, and production switched
to the DH.9, which turned out to be disappointing, being inferior to the DH.4 in
most respects. It was left to the further developed DH.9A, with the American
Liberty engine, to satisfactorily replace the DH.4.
At the time of its entry into the war, the United States Army Air Service lacked
any aircraft suitable for front line combat. It therefore procured various
aircraft from the British and French, one being the DH.4. As the DH-4, it was
manufactured mostly by Dayton-Wright and Fisher Body for service with the United
States from 1918, the first American built DH-4 being delivered to France in May
1918, with combat operations commencing in August 1918. The powerplant was a
Liberty L-12 of 400 hp (300 kW) and it was fitted with two .30 in (7.62 mm)
Marlin (a development of the Colt-Browning) machine guns in the nose and two .30
in (7.62 mm) Lewis guns in the rear and could carry 322 lb (146 kg) of bombs. it
could also be equipped with various radios like the SCR-68 for artillery
spotting missions. The heavier engine reduced performance compared with the
Rolls-Royce powered version, but as the "Liberty Plane" it became the US Army
Air Service standard general purpose two-seater, and on the whole was fairly
popular with its crews.
Aircrew operating the DH-4 were awarded four of the six Medals of Honor awarded
to American aviators. First Lieutenant Harold Ernest Goettler and Second
Lieutenant Erwin R. Bleckley received posthumous awards after being killed on 12
October 1918 attempting to drop supplies to the Lost Battalion of the 77th
Division, cut off by German troops during the Meuse-Argonne Offensive; while
Second Lieutenant Ralph Talbot and Gunnery Sergeant Robert G. Robinson of the
United States Marine Corps (USMC) were awarded the Medal of Honor for beating
off attacks from 12 German fighters during a bombing raid over Belgium on 8
October 1918. The type flew with 13 U.S. squadrons by the end of 1918.
Specifications (DH.4 - Eagle VIII engine)
General characteristics
Crew: two
Length: 30 ft 8 in (9.35 m)
Wingspan: 43 feet 4 in (13.21 m)
Height: 11 ft (3.35 m)
Empty weight: 2,387 lb (1,085 kg)
Loaded weight: 3,472 lb (1,578 kg)
kW)
Performance
Maximum speed: 143 mph (230 km/h) at sea level
Range: 470 mi (770 km)
Service ceiling: 22,000 ft (6,700 m)
Rate of climb: 1,000 ft/min (305 m/min)
Power/mass: 0.108 hp/lb (0.266 kW/kg)
Climb to 10,000 ft: 9 min
Armament
Guns: Forward-firing .303 in (7.7 mm) Vickers machine gun, Lewis gun on Scarff
ring at rear
Bombs: 460 lb (210 kg) of bombs
*
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