Handley Page Type O

The Handley Page Type O was an early biplane bomber used by Britain during the First World War. At the time, it was the largest aircraft that had been built in the UK and one of the largest in the world. It was built in two major versions, the Handley Page O/100 (H.P.11) and Handley Page O/400 (H.P.12).

The impression made by the Type O was such that for many years after the war, any large aircraft came to be called a "Handley Page" in Britain and entered the dictionary as such.

Design
The design of the series of aircraft began shortly after the outbreak of the First World War as a result of meetings between the Royal Navy's Director of the Air Department, Captain Murray Sueter and Frederick Handley Page. Sueter requested "a bloody paralyser of an aircraft" for long-range bombing. The phrase had originated from Commander Charles Rumney Samson who had returned from the front. Coastal patrol adaptations of the unbuilt Handley Page L/200 and M/200 and MS/200 were initially discussed, but Sueter's technical advisor Harris Booth favoured a large seaplane for coastal patrol and dockyard defence that would also be capable of bombing the German High Seas Fleet at its base in Kiel: a prototype (the AD Seaplane Type 1000) had already been commissioned from J Samuel White & Co. of Cowes. Handley Page suggested building a landplane of similar size, and a specification was drawn up around his suggestions: this was formally issued on 28 December 1914 as the basis of an order for four prototypes. It called for a large biplane - that would fit in a 75 ft x 75 ft shed and so necessitating folding-wings - to be powered by two 150 hp Sunbeam engines to carry six 100 lb bombs and provided with armour plating to protect crew and engines from rifle-fire from the ground. The crew of two were to be enclosed in a glazed cockpit and the only defensive armament planned was a rifle to be fired by the observer/engineer. The designation O/100 came from the aircraft's proposed wingspan prefixed by an 'O', since Handley Page gave their types alphabetical type letters at the time. The outline design was approved on 4 February 1915, now with 250 hp Rolls-Royce Eagle engines, and on 9 February the contract was amended to include a further eight aircraft.

The O/100 was an unequal-span three-bay biplane with the overhanging part of the upper wing braced by kingposts, with a rectangular section fuselage and a biplane tail unit with twin balanced rudders mounted between the horizontal surfaces. Balanced ailerons were fitted to the upper wing only. These extended beyond the wing trailing edge, giving the aircraft a distinctive planform. The two engines drove four-bladed propellers rotating in opposite directions to avoid torque effects and were enclosed in armoured nacelles mounted between the wings on tubular steel struts. The nacelles had a long tapered fairing to reduce drag: in order to clear the wing rigging wires when the wings were folded, the rear portion of the fairings were hinged to fold inward. Construction of the fuselage and flying surfaces was primarily of spruce, with great pains being taken to reduce weight by extensive use of hollow section members.

Development
The four prototypes and first production batch of six aircraft were built at Cricklewood with the first aircraft delivered by road to Hendon on 9 December 1915. The first flight of the first prototype, serial number 1455, was made at Hendon on 17 December 1915 when a short straight flight was made, the aircraft taking off without trouble at 50 mph. A second flight was made the following day, when it was found that the aircraft would not fly faster than about 55 mph. This was blamed on the drag caused by large honeycomb radiators, which were changed for tube radiators mounted either side of the engine nacelles. A third flight on 31 December revealed a number of control problems: ailerons and elevators were effective but heavy, partly due to excessive friction in the control circuit, and the rudders were seriously overbalanced. After minor modifications to address these issues, the aircraft was flown to RNAS Eastchurch, where full-speed trials were made. However on reaching 70 mph, the tail unit began to vibrate and twist violently: the pilot immediately landed, and an inspection showed severe damage to the rear fuselage structure. Reinforcement failed to cure the problem. The enclosed cockpit and most of the armour plating were also removed.

The second prototype, 1456, was completed in April 1916. This had an open cockpit in a lengthened nose with provision for a gunners position in the extreme nose. In order to save weight, most of the armour plating was deleted. This was the arrangement for later production of the machine.

After a series of proving flights at Hendon, 1456 was accepted by the RNAS and was flown to Manston for further trials. These revealed that despite a reduced balance area on the elevators, there was still a tail oscillation problem. A lack of directional stability caused by the increased forward side area was partly cured by adding a fixed vertical surface, but in order to find the cause of the tail oscillation the Admiralty called in F.W. Lanchester from the National Physics Laboratory. He agreed that simple structural weakness was not the root of the problem, and suspected that resonance of the fuselage was the probable cause. Static tests on a third prototype, 1457, which had a redesigned, stiffer, fuselage structure, showed nothing. This aircraft had an amidships crew position, and on 26 June Lanchester was flown as an observer. The tail oscillations started at 80 mph, and Lanchester observed that the tail was twisting by 15° to either side, and deduced that the probable cause was asymmetric movement of the right and left halves of the elevators, which were not rigidly linked but only connected by long control cables. He recommended that the halves of the elevators be connected, removal of the elevator balances and additional bracing between the lower longerons and the lower tailplane spar. These measures were wholly successful.

The fourth prototype, 1458, was completed with the same fuselage structure as 1456 and provision for armament, with a Scarff ring mounting in the nose, a pair of post mountings in the mid position and a gun mounting in the rear fuselage. This was also the first 0/100 to be fitted with uprated 320 hp Eagle engines. After completing acceptance trials, 1456 and 1457 were retained at Manston to form a Handley Page training flight. The first prototype was rebuilt to production standard and 1458 used to test a new nacelle design. This was unarmoured, had an enlarged fuel tank, and the fairing was shortened, eliminating the need for the tip to fold. This nacelle design was used on all aircraft built after the initial batch of twelve. From 1461 onward, an additional 130 impgal fuel tank was fitted in the fuselage above the bomb floor. A total of 46 examples of the O/100 were built before the type was superseded by the Type O/400.

The most significant difference between the two types was the use of 360 hp Eagle VIII engines. Unlike the earlier version, this engine was not built in right handed and left handed versions. This was because production of the necessary engines of both types for engine type approval had been difficult: wind tunnel tests at the NPL established that the contra-rotating propellers were a cause of the O/100's directional instability, and so it was realised that only one version was necessary, simplifying both production and maintenance. The torque effect was overcome by offsetting the fin slightly. In addition, the O/400 had a strengthened fuselage, an increased bomb load and redesigned tankage: the nacelle tanks were deleted and fuel was carried in two 130 impgal fuselage tanks supplying a pair of 15 impgal gravity tanks. Deletion of the nacelle tanks permitted a more compact nacelle design,which in turn allowed a simplified arrangement of supporting struts: the resultant loss of drag producing an improvement in maximum speed and altitude. The revised nacelle was tested in 3188, which during 1917 was flown at Martlesham Heath with a variety of engine installations. An initial order for 100 of the revised design, to be powered either by Sunbeam Maoris or Eagles, was placed on 14 August but cancelled shortly afterwards. Twelve sets of Cricklewood-built components were then transferred to the Royal Aircraft Factory, where they were assembled into the first production O/400s. Over 400 were supplied before the Armistice. Another 107 were licence-built in the USA by the Standard Aircraft Corporation (out of a total order of 1,500 by the air corps). Forty-six out of an order for 50 were built by Clayton & Shuttleworth in Lincoln.

Operational history
The first O/100s to be deployed to France were received by 7A Squadron of the RNAS's 5th Wing at Dunkirk in late 1916. Their first combat came on the night of 16 March 1917 when a single aircraft was sent to bomb a railway junction at Moulins-lès-Metz. Initially, they were also used for daylight attacks, damaging a German destroyer on 23 April 1917, but the loss of an aircraft to fighter attack two days later resulted in a switch to exclusive night attacks, usually by single aircraft against German occupied Channel ports, railway targets and airfields. O/100s were also used for anti-U boat patrol off the mouth of the River Tees in September 1917.

The improved O/400 started to enter service in April 1918, gradually allowing the re-equipment of more squadrons, being used for both support for the ground forces on the Western Front, particularly during the German Spring Offensive, and for strategic bombing under the control of the Independent Air Force. The O/400s could carry a new 1,650 lb (750 kg) bomb which were aimed with the Drift Sight Mk 1A bombsight. In service, they were deployed in force, with up to 40 aircraft participating in a raid.

Away from the European theatre of war, a single O/400 served with 1 Squadron, Australian Flying Corps in the Middle East. There, flown by Lt. Ross Smith, it was used for night attacks against the Turkish and supplying the small number of aircraft flying in support of Lawrence of Arabia. As part of the Dardanelles campaign a single O/100, 3124, was flown to Moudros on the Greek island of Lemnos. On 9 July 1917, squadron commander Kenneth Savory used it to bomb the battle cruiser Goeben at anchor in Constantinople, winning a bar to his DFC After being used for anti-submarine patrols and to bomb Adrianopolis and Panderma, it was lost and the crew taken prisoner on 30 September when, flown by John Alcock, it was forced to ditch due to a broken oil-pipe in an attempt to bomb railway marshalling yards near Constantinople.

After the war, O/400s remained in squadron service until replaced by the Vickers Vimy toward the end of 1919. War-surplus aircraft were converted for civilian use in the UK and nine were used by Handley Page's pioneering airline, Handley Page Transport.

Eight O/400s were fitted with passenger accommodation and operated by the 86th (Communication) wing, formed at Hendon to provide quick transport between London and Paris for officials engaged  in the negotiation of the Treaty of Versailles. Two were finished in silver dope and named Great Britain and Silver Star and fitted as VIP transports, while the others, seating eight, retained their dark green finish.

Six aircraft were assembled post-war for sale to Republican China under the designation O/7, principally for use as transports. These were delivered to China and re-assembled at Nanyuan near Beijing. The aircraft flew their first service, carrying both airmail and passengers, between Beijing and Tientsin on 7 May 1920. These services were disrupted by the outbreak of civil war, with the aircraft being taken over by various warlords.

Prior to 1924, Handley Page used an alphabetical system for aircraft designations and the Type O followed the Type M and Type N. Type O aircraft are very frequently misnamed as "Handley Page 0/100" and "0/400" with a numeral "0" instead of the letter "O". The company designations "H.P.11" and "H.P.12" were applied retrospectively after the change to the use of type numbers in 1924.

Variants

 * O/100
 * Original bomber version for RNAS - Two 260 hp (190 kW) Rolls-Royce Eagle II engines. Four prototypes and 42 production aircraft built.


 * O/400
 * Improved bomber for RFC/RAF - Two 360 hp (270 kW) Rolls-Royce Eagle VIII engines. 554 built.


 * O/7
 * Export transport version for China to carry 14 passengers. Lengthened engine nacelles for fuel tanks moved from fuselage; 12 conversions.


 * O/10
 * Transport variant to carry 12 passengers; 10 conversions.


 * O/11
 * Variant of the O/7 for mixed passenger/cargo use, two passengers up front and three in the very rear, with a freight in between; three conversions.

Civil

 * The Government of China
 * 🇮🇳 India
 * Indo Burmese Transport.
 * The Polish Government bought one aircraft in 1920.
 * Handley Page Transport
 * The Polish Government bought one aircraft in 1920.
 * Handley Page Transport
 * Handley Page Transport

Military

 * Australian Flying Corps
 * No. 1 Squadron AFC in Palestine.
 * Royal Air Force
 * No. 58 Squadron RAF (O/400)
 * No. 70 Squadron RAF (O/400)
 * No. 97 Squadron RAF (O/400)
 * No. 100 Squadron RAF (O/400)
 * No. 115 Squadron RAF (O/400)
 * No. 116 Squadron RAF (O/400)
 * No. 207 Squadron RAF (O/400)
 * No. 214 Squadron RAF (O/400)
 * No. 215 Squadron RAF (O/100 and O/400)
 * No. 216 Squadron RAF (O/400)
 * Royal Naval Air Service
 * No. 7 Squadron RNAS (O/100)
 * No. 7A Squadron RNAS (O/100)
 * No. 14 Squadron RNAS (O/100)
 * No. 15 Squadron RNAS (O/100)
 * No. 16 Squadron RNAS (O/100 and O/400)
 * Handley Page Squadron (O/100 and O/400)
 * No. 15 Squadron RNAS (O/100)
 * No. 16 Squadron RNAS (O/100 and O/400)
 * Handley Page Squadron (O/100 and O/400)

Captured aircraft
One of the early O/100s 1463 landed behind German lines on 1 January 1917, the five crew became prisoners of war and the aircraft was painted and flown in German markings until it later crashed.

Accidents and incidents

 * On 14 December 1920 a Handley Page Transport O/400, operating a service from the company's airfield at Cricklewood, crashed on take-off when it hit a tree, killing the two crew and two of the six passengers.