12.09 The Trials and tribulations of producing the right aircraft
Bristol Aircraft’s resistance to the fitting of another manufactures engine to their aircraft had caused real problems within the RAF and the Air Ministry. At one time during the height of the Taurus engines debacle the government had seriously considered nationalising the company and sacking the entire boards of directors. The companies obstruction of the fitting of another companies engines eventually resulted in the simple expedient of cancelling the Beaufort and increasing orders for the Beaufighter. Whilst all this was going on the Australian Government had already bought a licence for both the Beaufort and the Taurus engine. When the Australian government looked at the problems with the Taurus their experts ventured the opinion that a sleeve valve engine would not be the best choice for a domestically produced engine. An engine using conventional valves would be within the experience of the existing aeronautical and internal combustion engine industry in Australia. After due consideration the choice had come down to either the Alvis Pelades engine or the Pratt and Whitney Twin Wasp. With the British Government offering financial aid for the building of a factory to build the Alvis engine the choice was made in the favour of that engine. The subsequent success of the Australian Beaufort with the Alvis engine would do much to show how self serving the position of the Bristol Directors had been in their objection to and obstruction of the use of the Alvis engine in the UK.
Despite all the problems the first Australian built Beaufort had flown in May 1940 and series production of the first batch was preceding to schedule with some two hundred aircraft on order. Testing by RAF pilots had resulted in August 1940 of renewed attempts by the AM and the MAP to revive production of the Beaufort in the UK. After due consideration and the adverse effect on Beaufighter production assessed ,it was not considered worth the slightly better performance of the Alvis engine version of the Beaufort over the similar engine version of the Hadley Page Hampton. Also the potential of the Beaufighter as a cannon armed, rocket/bomb/ or torpedo carrying maritime strike fighter was now being recognised, so by late November nineteen forty all efforts by the MAP were in the case of the Bristol Aircraft Company focused on maximising the production of the Beaufighter in all it’s variants and ensuring that the supply of Bristol built engines was sufficient to meet the current and future airframe construction schedules. With increasing production of the Beaufighter and the commencement of serial production of the Hadley Page Halifax the requirement for Hercules engines was set to rise steeply through nineteen forty one.
To mitigate engine shortages due to enemy action or production problems it was current AM requirements that as many aircraft types as possible were fitted and test flown with at least one alternative engine. Hence Wellingtons being fitted with inline Merlins as replacements for the radial as was the Armstrong Whitworth Whitley. The Hercules engine Beaufighter was also built using Merlin engines and had been test flown with the Alvis pelides. Whereas the Halifax with Hercules could also be built to use either the pelides or tha Merlin as an alternative.
The Pelides with a swept volume equivalent to the Hercules was producing comparable power despite the use of conventional valves. The Alcadies with a swept volume only a litre greater than the Centaurus was as this stage of development matching it for power, both engines currently peaking at around one hundred and ten horse power per cylinder for a gross output of just under two thousand horse power. However Bristols were developing a new head for the engine which they claimed would enable a considerable increase in the engines power.
With the Avro Manchester there was a problem that in Mid 1040 there was no other production engine then available in the two thousand horsepower class. Both Bristol and Alvis were developing suitably powerful radial engines but neither were yet ready for entry into service. Therefore the option to develop a four engine version of the Manchester, originally designated Manchester III, was being pursued.
Four Manchester fuselages had been removed from the production line to provide the basis for the Manchester III, the first protype number BT 308 was built with a new wing spanning one hundred and two feet, as opposed the the Manchester II’s wingspan of ninety feet (increased from the eighty two feet of the original prototypes), for speed of production the original triple tail fin and twenty foot tail plane span was retained. The following three prototype aircraft had the modified Manchester Mark II tail plane of longer span with the two larger endplate fins. Commenced on the the same day the second aircraft to be modified, numbered BT 812, known as the Manchester Mk II L.W. (long wing) was built as a proof of concept by adapting the new one hundred and two foot wingspan to take the two Monarch engines of the Manchester II. The reason behind this development was that since the first Manchester Mark I’s had flown the Monarch had gained twenty percent more power and that was seen to produce a somewhat over powered airframe for the weight and wing area. So it was that the two prototypes were constructed side by side and actually test flown on the same day in January 1941
Both aircraft were sent to the Aircraft and Armament Experimental Establishment at Boscombe Down for trials and assessment. The Manchester II.LW with four thousand eight hundred installed horse power from it’s twin Monarch engines showed distinct advantages of the standard aircraft. Meanwhile the four engine version now christened Lancaster with four merlin mark X engines providing a total of four thousand five hundred and eighty horsepower. As a result of these early trials the third protype number DG 595 as the first production standard Lancaster was fitted with four Merlin XX type engines giving a total of five thousand one hundred and twenty horsepower. Ernest Hives at Rolls Royce had promised that by the time the Lancaster could enter service Rolls Royce would have a mark of Merlin capable of providing at least one thousand five hundred horse power.
All of these development were to give the RAF, AM, and the MAP much food for thought. The success of the Lancaster prototype and the probability that it’s production version would have greater development potential than the Manchester had raised some real problems for all concerned, the Manchester MkII was only now entering squadron service in numbers and to change production now and lose a considerable number of airframes was not viable. Whilst The operational advantages of the Manchester Mk III would be more easily obtained with less disruption and in the eyes of the bureaucrats at the MAP would with the same basic wing structure as the Lancaster provide a viable stepping stone to Lancaster production if that was required. With production jigs being prepared at Armstrong Whitworth time was of the essence and a decision to commence production of the Manchester MkIII needed to be taken quickly.
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