Merlin Musings
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Project North Star Association of Canada December 2007 Merlin Musings Fifth in a series after the Battle of Britain when the Luftwaffe began bombing raids at night on Britain and made use of its Ted Devey radar. Initially they were fitted with Bristol Hercules Merline Engine Applications (con- sleeve-valve radial engines but when engine pro- duction lagged behind airframe production, Mer- tinued) lin engines were fitted to production aircraft. Of about 5500 Beaufighters built, 442 Mk ll aircraft were Two engine aircraft equipped with Merlin XX engines.. After catching up in production the remaining Beaufighters were pow- Most aircraft fitted with two or four Merlin engines ered by Bristol Hercules engines. were bombers, however some two engine aircraft were classed as fighters or fighter bombers. Two en- gine aircraft using Merlins included the De Havil- De Havilland Mosquito land Mosquito and the Bristol Beaufighter. Heavy bombers were powered by four engines The Mosquito was of unique design and construc- and will be considered in the next chapter in this se- tion. The airframe was built almost entirely of wood, ries. usually a very thin veneer ranging from .035" to .80" Twin engine aircraft are rather a mixed group as in thickness separated by a sandwich core of Balsa .75 some of a kind were powered by Merlins and oth- to 1.25" Thickness. In tropical areas, Mosquitoes suf- ers by radial engines, principally Bristol Hercules fered from delamination of the veneers due to high sleeve=valve engines; others were powered exclu- temperature and humidity environments. However, sively by Merlins. in the cooler temperatures of the European theatre of war, laminated structures were quite stable and reli- able. Mosquitoes were adapted for a number of dif- Bristol Beaufighter Mk ll ferent roles, low-altitude ’hedge-hop’ bombing runs, long range reconnaissance, attacks on shipping and The Beaufighter was intended for long-range opera- submarines (Coastal Command), ground attack etc. tion equipped for various roles; as a night fighter (it Initially, Mosquitoes equipped for bombing could was one of the first aircraft to be fitted with radar), carry 1000 lbs. of bombs, 2 250 lb. bombs in the bomb torpedo-bomber, ground attack fighter, and attacker bay and 2 250 lb bombs under the wings. of shipping. The Beaufighter first saw service in 1940 Eventually, Mosquitoes could carry 4000 lbs of Contents of this volume: TransCanadaAirlinesNorthStars . 2 TheLifeofRobertHolmgren . 4 MerlinMusings .................. 1 Miscellany ..................... 6 PNSAC Newsletter December 2007 bombs. With a special modification to the bomb bay, radar than airplanes of metal construction. a single 4000 lb bomb could be carried. Low-flying About 6400 Mosquitoes were built in Britain in a Mosquitoes would precede raids by heavy bombers dozen variants while about 1300 were built in Aus- by laying down coloured incendiaries to precisely lo- tralia, and Canada (at Downsview, Toronto, which is cate specified targets, thus improving the accuracy of now the location of the Toronto Aerospace Museum). the raids by heavy bombers. All Mosquitoes were fitted with Merlin engines. Early production models were fitted with Merlins Hedge-hopping was a specialty of Mosquitoes equipped with 2-speed single-stage superchargers. whereby the plane would fly at low altitudes just When later models were fitted with 2- speed 2- above ground foliage and below radar beams thus stage Merlins, higher altitude performance was con- avoiding detection. The use of wooden construc- siderably enhanced often as high as 30,000 feet. tion provided two advantages, 1) relief of metal sup- Mosquitoes were very versatile aircraft due to the plies that were of limited availability and 2) very low high performance of Merlin Engines. About 1100 radar reflectivity because wood absorbed radar en- Mosquitoes were built at Downsview and were fit- ergy whereas metal returned radar energy quite effi- ted with Packard Merlins from Detroit. ciently. Mosquitoes were more difficult to detect by PNSAC Trans Canada Airlines North Stars setting of 990 brake horse power per engine was used. When the aircraft and power plant were cho- Bill Tate sen, the humour of the day suggested it was an ille- gitimate aircraft conceived in Canada by an Ameri- In late 1943 the outcome of World War II was show- can father with an English mother! ing in favour of the Allies. This allowed the Gov- ernment of Canada to begin looking for an aircraft The aircraft was built under license in that would meet the needs of the Royal Canadian Cartierville, Quebec, to help establish a Canadian Air Force (RCAF) and Trans Canada Airlines (TCA). aviation presence and to assist in the transition from At that time, only the Lockheed Super Constellation a war-industry to a post-war economy. and the DC-4 were the only two commercial aircraft types available. The former was experiencing tech- Of the 71 aircraft that were eventually built, the nical problems with its testing and development; the bulk of production was for TCA (20 aircraft), the latter had a proven track record in commercial avia- RCAF (24 aircraft) and BOAC (22 aircraft known as tion and in a military application known as the C-54. the Argonaut). With the war concluded, Douglas an- The Government of Canada chose the DC-4 to nounced that the DC-6 would be built which was be called the North Star, to be built in Cartierville larger and pressurized. Since the choice for the DC- outside of Montreal. TCA decided it would need 4 had been made, TCA entered into discussion with an aircraft suitable for oceanic services but it would Douglas to determine if the DC-4 could be pressur- require a larger power plant. The available power ized. It was decided that it could be done but with plant of the day (Pratt and Whitney) P.W. R-2000 major modifications required as the initial aircraft Dash 9 rated at 1100 horse power was suitable for do- was not built to be pressurized. Further modifica- mestic operations but not for oceanic services. Win- tions included the use of the landing gear for the ter operations (runway conditions) in Canada re- DC-6 and using the DC-6 fuselage with an 80-inch sulted in the requirement for an additional 200 horse section removed (same size of DC-4). Versions of the power per engine for the North Star. The Rolls Royce aircraft types built were the C-54 GM (the first ver- 620 series engine rated at 1725 horse power was se- sion for the RCAF), the DC-4 M1, (the final version lected for the aircraft. for the RCAF), DC-4 M2 (pressurized passenger for The advantage was that the Rolls-Royce power TCA), CL-4 (DC-4M2) design for BOAC for its Impe- plant had a proven military track record and a two rial Route Structure to the Far East). The C-4-1 was stage super-charger for high altitude flight at a low built for Canadian Pacific Airlines (CPA), four were speed and medium speed setting. At an altitude of delivered and used on trans Pacific service, and fi- 23,000 feet, in the medium speed setting for the su- nally the CL-5 V.I.P.transport(4 Pratt Whitney R-2800 percharger, it could produce 1150 h.p. per engine. radial engines) of which only one was built for the For fuel economy for trans-oceanic flight, a power Government of Canada for V.I.P. services. 2 PNSAC Newsletter December 2007 flaps, and brakes which were normally powered from the number three engine along with electric hy- draulic pumps. Emergency landing gear extension was accomplished by a hand pump in the cockpit with trapped hydraulic fluid. On one flight with H.R.H. Prince Phillip the aircraft lost its hydraulics and the gear had to be hand pumped down. Prince Phillip said "nice rowing chaps". On signing the contract, TCA agreed to pay a to- tal of $13,320,000 for twenty aircraft in 1947 dollars or $660,000. per aircraft. Using Bank of Canada C.P.I. adjustment for today’s dollars would show the value of the contract to be $144,450,875.00for the 20 aircraft of $7,175,475.00per aircraft. As the reader can appre- Figure 1: DC4M North Star at Vancouver Interna- ciate, this was a huge capital acquisition for TCA but tional Airport (Photo courtesy of Mel Lawrence) the government of the day wanted the money to re- main in Canada plus having the skill-set to built large Roll out of the first aircraft was 20 July 1946. Ini- aircraft to stay here as well. tial flight tests showed the aircraft had very easy Before the DC-4 M2 was in production, TCA ac- handling characteristics. During testing, it was de- quired six unpressurized C-54 GM aircraft to start its termined that the four bladed propeller could gen- ’transoceanic’ service to England in the fall of 1947. erate the best second segment climb characteristics The DC-4 M2 served on this route until 1961. in an engine-out situation. Although 79,850 lbs was As with most new aircraft the airplane came in the maximum gross take-off weight, the four bladed heavy. TCA had a weight reduction plan set-up from propeller met second segment climb requirements at 1948 to 1951 which had 731 lbs removed for oceanic 82,700 lbs versus 80,200 lbs for the three-bladed pro- services and 1134 lbs removed for domestic opera- peller. By using the conservative figure of 79,850 tion. lbs., this assured a more conservative margin in an The initial layout was for forty passengers in a engine-out consideration.