Handley Page Type O

The Handley Page Type O was a biplane bomber used by Britain during the First World War. When built, the Type O was the largest aircraft that had been built in the UK and one of the largest in the world.

There were two main variants, the Handley Page O/100 (H.P.11) and the Handley Page O/400 (H.P.12). The aircraft were used in France for tactical night attacks on targets in German-occupied France and Belgium and for strategic bombing of industrial and transport targets in the Rhineland.

Some aircraft were temporarily diverted to anti-submarine reconnaissance and bombing in the Tees estuary in 1917 and two aircraft operated in the eastern Mediterranean.

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. The design of the series of aircraft began shortly after the outbreak of the First World War after meetings between Captain Murray Sueter, the director of the Air Department of the Royal Navy, and Frederick Handley Page. Sueter requested "a bloody paralyser of an aircraft" for long-range bombing.

The phrase was originated by Commander Charles Rumney Samson, who had recently returned from the front.[4] Coastal patrol adaptations of the abortive Handley Page L/200, M/200 and MS/200 designs 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 (AD Seaplane Type 1000) had already been commissioned from J. Samuel White & Co. of Cowes.[5] Handley Page suggested building a land-based aircraft of similar size, and a specification was drawn up around his suggestions and formally issued on 28 December 1914 for four prototypes. It called for a large biplane to be powered by two 150 hp (110 kW) Sunbeam engines, which was required to fit in a 75 ft × 75 ft (23 m × 23 m) shed and would therefore have folding wings.

It was to carry six 100 lb (45 kg) bombs and have 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 name O/100 came from the proposed wingspan of the aircraft prefixed by an 'O', since Handley Page gave their types alphabetical type letters.[5] The outline design was approved on 4 February 1915, with 250 hp (190 kW) 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, a rectangular section fuselage and a biplane tail with twin balanced rudders, between the horizontal surfaces.

Balanced ailerons were fitted to the upper wing only and extended beyond the wing trailing edge.

The engines drove four-bladed propellers, rotating in opposite directions to cancel the torque and were enclosed in armoured nacelles, mounted between the wings on tubular steel struts. The nacelles had a long tapered fairing to reduce drag; to clear the wing rigging wires when the wings were folded, the rear portions of the fairings were hinged to fold inward. Construction of the fuselage and flying surfaces was primarily of spruce, with much reduction in 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 prototype, serial number 1455, was made at Hendon on 17 December, when a short straight flight was made, the aircraft taking off without trouble at 50 mph (80 km/h). A second flight was made the following day, when it was found that the aircraft would not fly faster than about 55 mph (89 km/h).

This was blamed on the drag caused by large honeycomb radiators, which were changed to tube radiators mounted on either side of the engine nacelles. A third flight on 31 December revealed a number of control problems, the 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, the aircraft was flown to RNAS Eastchurch, where full-speed trials were made.

On reaching 70 mph (110 km/h), 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 and had an open cockpit in a longer nose with room for a gunner's position.

To save weight, most of the armour plating was deleted and 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 fin but to find the cause of the tail oscillation, the Admiralty called in Frederick Lanchester from the National Physics Laboratory. Lanchester agreed that simple structural weakness was not the root of the problem and that resonance of the fuselage was the probable cause.

Static tests on the 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 (130 km/h); Lanchester observed that the tail was twisting by 15° to either side and deduced that the cause was asymmetric movement of the right and left halves of the elevators, which were not rigidly linked but connected by long control cables.

He recommended that the halves of the elevators be connected, the elevator balances removed and further bracing added between the lower longerons and the lower tailplane spar, measures which 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 O/100 to be fitted with 320 hp (240 kW) 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 was used to test a new nacelle design, which was un-armoured, had an enlarged fuel tank and a shorter fairing obviating the need for the tip to fold. The new nacelle design was used on all aircraft built after the initial batch of twelve. From 1461, an additional 130 imp gal (590 L) fuel tank was fitted in the fuselage above the bomb floor. A total of 46 O/100s were built before being superseded by the Type O/400.

The most significant difference between the two types was the use of 360 horsepower (270 kW) Eagle VIII engines (£1,622/10/- [£1,622.50] each).[13] Unlike the earlier version, this engine was not built in right-handed and left-handed versions, because production of engines of both types for engine type approval had been difficult; wind tunnel tests at the NPL established that the counter-rotating propellers were a cause of the directional instability of the O/100. It was realised that only one version was necessary, simplifying production and maintenance; the torque effect was overcome by offsetting the fin slightly.

The O/400 had a strengthened fuselage, an increased bomb load, the nacelle tanks were removed and the fuel was carried in two 130 imp gal (590 L) fuselage tanks, supplying a pair of 15 imp gal (68 L) gravity tanks.

The new nacelles were smaller and had simplified supporting struts; the reduction of drag producing an improvement in maximum speed and altitude. The revised nacelle was tested in 3188, which in 1917 was flown at Martlesham Heath with a variety of engine installations. An initial order for 100 of the revised design, with Sunbeam Maori or Eagle engines, was placed on 14 August but cancelled shortly afterwards.

Twelve sets of Cricklewood-built components were transferred to the Royal Aircraft Factory, where they were assembled into the first production O/400s.

More than 400 were supplied before the Armistice at a price of £6,000 each.

Another 107 were licence-built in the US by the Standard Aircraft Corporation (out of 1,500 ordered by the air corps). Forty-six out of an order for fifty were built by Clayton & Shuttleworth in Lincoln.

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