The Handley Page Halifax was conceived in 1936 as the result of an Air Ministry specification which called for an all metal mid wing cantilever monoplane heavy medium bomber to be powered by two Rolls Royce Vulture liquid cooled engines, these still being in the state of development. Because of subsequent doubts as to the ultimate suitability of these engines, the design requirement for the airframe was altered to take four engines, the tried and tested Rolls Royce Merlin units.
Construction of the prototype aeroplane, known as the HP57, began at the Handley Page Cricklewood factory in January 1938. Semi assembled sections were transported by road to RAF Bicester where the work of final assembly was completed. The first flight took place in October 1939, a month after the outbreak of World War 2.
The Protoype Halifax
A second prototype was flown from Boscombe Down in August 1940 and soon thereafter the machine went into limited production. The aircraft, designated HP57 Mk I, carried four 1130hp Rolls Royce Merlin X engines which gave a maximum speed of 255 mph at 7,000 feet and a cruising speed of 195mph at 15,000 feet. The service ceiling was 18,000 feet and the flight range was 1860 miles. When fully loaded and carrying the maximum complement of 13,000lb of bombs, the all up weight of the aircraft was 55,000 lb or over 24 ton. The wing span was 98’8”, the length was 74’1” with a standing height of 20’9”. Armament comprised two Browning .303 machine guns housed in a Boulton & Paul power operated turret in the nose, four in a similar turret in the tail of the aircraft. Additional Vickers gas operated guns were set to fire from beam position in the fuselage.
4 Group Bomber Command was the first recipient of the Halifax B Mk I with it being issued principally to 35 and 76 Squadrons. Testing and assessment under operational conditions continued and B Mk II duly appeared in October 1941, one month after Lady Halifax, performed the naming ceremony at Radlett.
The Mk II, introduced in January 1942, carried uprated Rolls Royce Merlin XX engines each giving an improved power output of 1220 hp, thus enabling the aircraft to perform somewhat better in respect of speed and at increased altitude, the service ceiling now being 22,000 feet. The bomb load and overall dimensions of the aircraft remained as for Mk I but the defence capability had improved by the introduction of a power operated mid upper turret containing two .303 machine guns, although the guns in the fuselage were taken out.
The continuing modifications and detail improvements being made although useful in themselves had the effect of increasing the overall weight of the bomber with serious effect on the performance of what was generally regarded as an already under powered machine.
A Mk II Series 1 variant was produced in August 1942 where the nose turret was removed, the mid upper turret replaced by a more streamlined version and the other drag reducing measures taken, such as removal of the under wing fuel jettison equipment and bulky asbestos muffs to the engine exhaust pipes. The engines were changed to Rolls Royce Merlin 22 units each giving 1,390 hp. The result of these changes gave about 20 mph increase in cruising speed.
A MkII saries 1 halifax of No10 Squadron
A serious problem had been encountered in that lack of rudder response when flying at relatively low speeds had caused a number of aircraft to enter into uncontrollable and fatal spins. It was thought also that this characteristic may have been induced by violent rudder action, such as would be employed during evasive flying. Extensive testing at the Aeroplane and Armament Experimental Establishment at Boscombe Down revealed the design of rudder to be the probable cause of locking. Accordingly the assembly was redesigned in that the leading edges of rudders, instead of being angled backwards above and below the tail-plane, were made vertical. This modification was introduced to the Mk II Series 1A Halifax and ultimately to all previous issues of the aircraft still in service. The new rectangular rudders remained a successful feature of the aircraft from then on.
Because, by this time, Handley Page were unable to meet service demand for the aircraft, a consortium of other firms was formed in order to cope with the large production programme. The principal members were, under the parentage of Handley Page, English Electric, Rootes Securities, Fairey Aviation and an organisation drawn from the automobile industry known as the London Aircraft Production Group the members of which were Chrysler Motors, Duple Bodies, Express Motor and Body Works, Park Royal Coachworks and the London Passenger Transport Board. During the peak of production, there were forty-one factories engaged on round the clock manufacturing utilising six hundred sub contractors with a total work force of fifty-one thousand people. The story is told by 578 Squadron ground crews that on receipt of these new machines the name plates of sub manufacturers would be removed, particularly that of LPTB so as to avoid misapprehension by the aircrews charged with flying them!
A considerable and successful step forward was achieved by the introduction in January 1994 of the Halifax B Mk III in which the four Rolls Royce Merlin engines were replaced by Bristol Hercules XVI radial units, each with the increased output of 1675 hp. These propelled the aircraft at a maximum speed of 277mph at 6,000 feet, gave a cruising speed of 225 mph at the service ceiling of 24,000 feet, a considerable improvement on earlier machines.
MkIII Prototype, still with original rudders
The armament had been settled at four .303 Browning machine guns in each of the mid upper and rear turrets and some aircraft possessed a single Vicars ‘K’ gun carried in the fuselage nose cone. All up weight had increased to 65,000 lb, or 29 ton, although the bomb load had remained the same as it had always been, 13,000 lbs. The size of the aircraft had increased marginally with a wing span of 104’2”, length of 71’7” but the standing height remained at 20’9”.
MkIII in final form, note rudders and perspex fairing: Later models had extended wing tips
578 Squadron, being newly formed, was one of the first to be equipped with this aircraft Aircrews drew great confidence in the handling ability, robust construction and reliability of such a large aircraft, which was to prove fully capable of carrying out the exacting tasks for which it was designed. There are many examples where the Halifax sustained damage which could have proved fatal to other aircraft. Ground staff responsible for maintenance, often under very difficult conditions also came to enthuse as to the qualities of airframe and engines on which they worked. Indeed 578 Squadron were to win the covetous Shield presented by the Bristol Aeroplane Company for the best engine servicing record in 4 Group Bomber Command.
source: ‘Based at Burn Mk II’
Author : ‘Hugh Cawdron’