|First flight||early 1918 |
|Introduction||April 1918 |
|Primary users|| U.K. (RFC/RAF)|
|Number built||550 to 554[note 1]|
|Developed from||Handley-Page O/100|
|Wingspan||30.5 m (100 ft) |
|Engine||2×322hp Rolls-Royce Eagle VI or|
2×360-375hp Rolls-Royce Eagle VIII 
|Armament||1-2×flexible nose Lewis|
rear left Lewis
rear right pillar-mounted Lewis
rear downward pillar-mounted Lewis[note 2][note 3]
680 kg (1,500 lb) to 910 kg (2,000 lb) of bombs [note 4][note 5]
|Ammo||17 drums of 97 rounds|
|Max Speed||156 km/h (97 mph) |
|Climb||1,000 ft (300 m) in 2:45|
6,500 ft (2,000 m) in 27:10 [note 6]
10,000 ft (3,000 m) in 45:00
|Service Ceiling||8,500 ft (2,600 m)  to 10,000 ft (3,000 m)[note 7]|
The Handley-Page O/100 had been Britain's best heavy bomber, and the Handley-Page O/400 was a refinement of that design. The chief difference was the removal of the fuel tanks from the engine nacelles to a pair of main tanks in the fuselage and smaller gravity tanks on the upper wing. The shortening of the nacelle allowed an ordinary strut to be placed behind the nacelle. While a handful of planes were built with alternative engines, the standard was the Rolls-Royce Eagle VI or VIII.
Like the O/100, the wings folded just past the engine nacelles so that the large aircraft could fit in standard Bessonneau hangars. The counter-rotating props of the O/100 were dropped and both propellers turned in the same direction, which simplified maintenance and inventory. The plane was too heavy to move by manual labor; instead a Clayton 35-hp crawler was used to move the plane from airfield to hangar and back.
While an order for one hundred was placed in August, 1917, it was not until the spring of 1918 that the O/400s started arriving in numbers, and it was only in late summer that they were used in large bombing formations.
Fifteen hundred Liberty-engined American O/400s were ordered from Standard, but only 107 had been delivered before the Armistice. American crews were just getting accustomed to the the type, and they were still training in England when the war ended. 
At the end of the war, 259 O/400s were operational with the RAF.
For more information, see Wikipedia:Handley_Page_Type_O.
Timeline [note 8]
|Version||Maneuver||Damage||Dmg Points||Max Alt.||Climb||Points|
Miniatures and Models
- Ares: WGF303A RAF; WGF303B RNAS
- Metal+Resin kit: Red Eagle
- Cast Metal: MSD Games/Hostile Aircraft
- Metal kit: Heroics & Ros GWA111
Isometric Top Views
- 281 were built by Handley-Page, 273 by others, plus there were six intermediate aircraft blending O/100 and O/400 characteristics.
- Firing downward to the rear from a trap door in the rear fuselage.
- The rear gunner was responsible for all three rear guns.
- 16×51 kg (112 lb) bombs or 8×110 kg (250 lb) bombs, 1×750 kg (1,650 lb) bomb, or various combinations.
- The rear gunner had also a small selection of 11 kg (25 lb) Cooper bombs and grenades to use on targets of opportunity.
- 6,500 ft (2,000 m) in 30:00 with the Eagle VI engines
- 7,000 ft (2,100 m) with Eagle VIs
- British usage numbers are approximate, derived from the squadron histories.
- Langham, p.97.
- Angelucci, p.76.
- Langham, p.47.
- Lamberton, pp.214-215.
- Bruce'69, p.272.
- Langham, p.27.
- Lamberton, p.64.
- Langham, pp.34-41.
- Langham, p.46.
- Kelly, p.230.
- Langham, p.28.
- Bruce'69, p.277.
- Munson, p.72.
- Langham, p.44.
- Angelucci, p.77.
- Philpott'13, pp.379-444.
- Enzo Angelucci, ed. The Rand McNally Encyclopedia of Military Aircraft, 1914-1980. New York: The Military Press, 1983 edition. ISBN 0-517-41021-4.
- J.M. Bruce. British Aeroplanes 1914-18. Great Britain, Funk & Wagnalls, 1957, 1969. ISBN 0370000382
- Kevin Kelly, "Belts and Drums: A Survey of First World War Aircraft Ammunition Totals". Over the Front, Vol. 5, No. 3, Autumn 1990. Walsworth Publishing Co, Inc. and The League of World War I Aviation Historians.
- W.M. Lamberton and E.F. Cheesman, Reconnaissance & Bomber Aircraft of the 1914-1918 War. Great Britain: Harleyford Publications Ltd., 1962. ISBN 9780900435027
- Rob Langham, Bloody Paralyser: The Giant Handley Page Bombers of the First World War. UK and USA: Fonthill Media Limited, 2016. ISBN 978-1-78155-080-9
- Kenneth Munson, Bombers: Patrol and Reconnaissance Aircraft, 1914-1919. New York: The MacMillan Company, 1968, Blandford Press Ltd. ISBN 978-0753721711
- Ian Philpott, The Birth of the Royal Air Force. Great Britain: Pen & Sword Books Limited, 2013. ISBN 978-1-78159-333-2