Ferrarin soon disappointed his local supporters by turning off the course on the first lap with two pistons burnt through, followed by de Bernardi on lap two, suffering from a connecting rod failure. The third Macchi, with an older replacement engine, proved no match for the British with their new uprated Lions, but then Kinkead retired at the beginning of the sixth lap when violent vibrations made it seem prudent to do so. This turned out to have been a wise decision as the previous vibrations were now found to have caused a shear-line about three-quarters around the circumference of the propeller shaft. Then, on the penultimate lap and in sight of being placed, the last Italian, Guazzetti, pulled out in spectacular fashion when he was blinded by the bursting of a petrol pipe. Luckily, he managed to get down safely, although not before just missing spectators on the roof of the Excelsior Hotel on the Lido.
Webster (watched by Mussolini) led the British whitewash with an average speed of 281.65mph, a new record for seaplanes and bettering by 3mph the world speed record for land planes. Worsley came second at 273.01mph in the second, ungeared, S5.
The skill of the pilots is demonstrated by the fact that the RAF front-line fighter at this time, the Armstrong Whitworth Siskin IIIA, had a top speed of only 186mph and that, despite light rain and haze towards the end of the competition, both men, while having to negotiate two sharp turns per lap, had averaged about 87 per cent of the maximum speed available to them. As Schofield said, ‘It must be remembered that we were the first service team, that our work … carried with it an increase in speed of a proportion unheard of before’. It ought also to be added that this unprecedented leap in speeds took place in racing aircraft with the low cockpit positions mentioned earlier, which gave extremely limited, almost non-existent forward views.
When Mitchell, with his wife, arrived back in England, he was among those feted by the Corporation of Southampton and his winning machine was put on display in London. A measure of the designer’s increased status can also be gained by his being invited to address the Royal Aeronautical Society at this time.
In 1928, Vickers (Aviation) Limited acquired the Supermarine Company, but acknowledged the achievements of Mitchell’s design team by retaining it as an entity at Woolston and by allowing the branch a separate identity. Thus, in subsequent volumes of Jane’s, publication of designs from Mitchell’s team were kept separate from other Vickers products under the following title: The Supermarine Aviation Works Ltd (Division of Vickers (Aviation) Ltd).
Vickers had no doubt acknowledged the potential of the much smaller company as early as 1920 when its Commercial Amphibian came a very close second to their Viking. Then came the orders for the Sea Eagle, the Seagull, the Scarab and, pre-eminently, the Southampton. However, in view of Vickers’ dominant position in the armaments industry, Mitchell’s high speed Schneider Trophy contributions must have been particularly noted and thus made Supermarine’s unexpected design of the Spitfire that much more probable.
Mitchell’s name now appeared among the list of Vickers directors, and the 1925 publicity description of him as ‘one of the leading flying boat and amphibian designers in the country’ was now significantly expanded to: ‘one of the leading flying boat, amphibian and high speed seaplane designers in the country’.
He was 34 years old.
THE FLYING RADIATORS
After Britain’s Schneider Trophy success in Venice, the world speed record was raised by the rival Italian Macchi M52, now that its engine problems had been overcome.
Flight Lieutenant Kinkead, who had now taken command of the High Speed Flight, attempted a challenge in the third S5, which had been held in reserve in Italy, but he was killed when he appeared to fly into the sea at full speed, perhaps because of some structural failure – contrary to the official inquest finding that the pilot stalled when attempting to land, because of poor visibility.
Flight Lieutenant D’Arcy Greig took over the flight, and the trophy-winning Supermarine S5 was now prepared for a further attempt. However, the speed achieved did not give a margin sufficient to justify a claim to the FAI and it was clear that a substantial improvement upon the British aircraft would be necessary in time for the defence of the trophy, especially as it would take place in front of a home crowd.
In 1927, Britain and Mitchell had been more fortunate than the Italians as their winning engine had not been a new, and therefore possibly unreliable, design. However, the Napier Lion had been in continuous development since its use in the Supermarine 1922 Schneider Trophy winner and, although it had never failed in the aircraft it powered, the question had nevertheless to be asked whether this remarkable engine was now reaching the end of its development potential.
By now, Rolls-Royce had produced the successful 490hp Kestrel, in response to the American Curtiss D-1 engine which had powered the Schneider Trophy-winning aircraft of 1923 and 1925. The Kestrel now offered reduction gearing and supercharging and Mitchell asked Major G.P. Bulman, the Air Ministry official responsible for the development of aero engines, for his opinions. Bulman thought that Rolls-Royce should be approached, and Mitchell was reported to have given it some thought and then said, ‘Right, that’s decided it.’
Commander James Bird, the managing director of Supermarine, and Bulman accordingly called on Henry Royce, then living in semi-retirement at his West Wittering home on the Sussex coast and, as it was already October 1928, it was decided that the partially developed 36.7-litre Buzzard engine would have to be the basis for the required new engine. It would have to have a modified crankcase and supercharger to conform to the sort of shape that Mitchell was likely to develop out of the S5 design and so it was separately designated the ‘R’ engine, with a hoped for output of 1,800hp.
The S6
For the improved airframe, Mitchell decided on the basic suitability of his previous design for the more powerful new engine. Thus his main design effort was in respect of a larger, all-metal, version of the S5, in order to accommodate the projected heavier engine: the 930lb of the Napier Lion in 1927 was to be replaced by an engine weighing 1530lb.
First configuration drawings were sent to Mitchell on 3 July 1928, and he was able to influence the shape of the cam covers so that they would conform to the streamlines he was developing for his new machine. An eventual 1900hp was achieved by August – a power increase of 211 per cent over the previous Lion engine, for what turned out to be a loaded aircraft weight increase of 78 per cent. Mitchell was reported to have said, ‘Go steady with your horsepower’ – no doubt anticipating the cooling problems that would be encountered.
An immediately obvious alteration to the new machine was the cowling, necessitated by the change from the ‘arrow’ shape of the Lion engine to the ‘V’ of the new Rolls-Royce unit. As the empty weight of the S6 was 1791lb heavier than that of the S5, the wingspan was increased by more than 3ft and the front float struts had to be moved further forward on the fuselage to support the heavier and longer engine. Also, the increase in fuel consumption, from the Lion engine with a 24-litre capacity to the proposed Rolls-Royce R engine of 36.7 litres, would require both floats to be used for the fuel tanks and the extra weight of the new engine made it necessary to move the pilot’s position further back.
Solving the constructional and loading problems in itself had justified the new design’s ‘S6’ designation, but these matters were relatively straightforward compared to contending with the heat produced by the new engine.
The channels for oil cooling attached to the sides of the fuselage of the S5 were now increased, more were added to the underside of the fuselage, and particular attention was given to their efficiency. Mitchell’s chief metallurgist, Arthur Black, came up with a solution whereby the channels which conveyed the oil from and to the engine had copper tongues soldered at right angles to the oil flow, and these were configured in such a way that they did not impede the flow of oil, while ensuring its maximum contact with the surfaces of the piping being cooled by the slipstream of the aircraft.
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sp; Additionally, the oil was now sprayed from this piping into the top of the fin to trickle down to the return pipes, thereby causing the fin to act as both oil tank and radiator. It was estimated that these devices increased the efficiency of the oil cooling by about 40 per cent but, nevertheless, Greig found that the position of the oil piping, attached to the sides and base of a very narrow fuselage, ‘turned the inside of the cockpit into something approaching an extremely hot Turkish bath’ with the oil temperature gauge reading ‘around 136 degrees centigrade’.
Other aspects of the design reflected the constructional changes beginning to take place in the aircraft industry, and Supermarine were anxious to point out that their move to metal construction was not just with respect to the framework of their machine, but placed them in the forefront of the use of load-bearing external skinning – particularly in respect of the wings. Here, instead of being plywood covered with the radiator panels externally attached, as with the S5, they were now covered by the panels alone. Now made of aluminium, the radiator panels now took torsional loads and, as Supermarine announced, ‘saved a considerable amount of weight over previous practice’.
Despite the gap of two years between competitions that had now been agreed upon, the scheduled start of the eleventh event was less than six weeks away before Mitchell’s new airframes could be tested in the air. In May, the new R engine had reached 1545hp but, after running for about quarter of an hour, failures began to occur and it was only at the end of July that the new engine passed the one hour mark at full throttle and supercharger boost. A few days later, with the blending of a special fuel, an engine run of 100 minutes and 1850hp was achieved.
Incidentally, the end of testing was much to the relief of the citizens of Derby, as the tests had also required the running of three Kestrel aero engines. They drove fans to cool the new R engine, to expel fumes from the test shed, and to enable the carburettors to be set up in simulated flight conditions. These were the days before modern health and safety regulations, and Rodwell Banks, responsible for the fuel mixes, described the din of four aero engines within the test sheds: ‘reverberation from walls and roof is such that at certain engine speeds one cannot keep still: the whole body seems in a state of high frequency vibration. One shouts at the top of one’s voice but cannot even feel the vibration of the vocal chords.’
People living up to 15 miles away reported still being able to hear the engine runs, and the ears of the Rolls-Royce workers were plugged with cotton wool. They were also well supplied with milk to counteract the laxative effect of breathing in the engine oil, ejected out of the exhaust ports and deposited on the walls of the test cell. Flight reported that one early run consumed oil at the rate of 112 gallons per hour and that the state of the test shed inside was ‘a wonder to behold’.
Meanwhile, a new High Speed Flight had been formed in the February of 1928. Greig, who had been posted in after the death of Kinkead, had recommended members of his Hendon aerobatic team: Flight Lieutenants G.H. Stainforth and R.D.H. Waghorn and Flying Officer R.L.R. Atcherley. He then prepared to hand over command to a Squadron Leader, A.H. Orlebar, with the new title, ‘Officer Commanding the High Speed Flight’. As before, none of these airmen had been trained as naval pilots, and so time was needed to convert onto the seaplanes that were expected to be the fastest in the world.
Waghorn has described how they used their practice machines to devise the best method for cornering with the help of scientists from the Royal Aircraft Establishment, who installed instruments in the machines to measure speed, acceleration and climb. A compromise between high G tight turns, with loss of speed, and wider arcs, which incurred less drag, was worked out. But, with the increased speed in the turns, pilots had now to get used to blacking out, as Atcherley recalled:
I went ‘out’ halfway round a turn at Calshot Castle [the sharpest of the four turns of the proposed course] and flew completely unconscious at about 500ft halfway back to Cowes before regaining my senses. Even then, there was a very frightening lapse of seconds when one realised that one was flying and had been ‘out’ but still could not see or move one’s hands.
As the circuit flying took place at an altitude of only a few hundred feet, he unsurprisingly admitted that ‘it made me brood a bit’.
These preparations received a considerable setback when the actual contest aircraft finally arrived and it was discovered that the possible effects of the much greater torque of the new engine had not been fully appreciated. Against the turn of the propeller, the S6 would dig in the left float, describing circles in the water which Orlebar reported ‘had rather shaken’ Mitchell. One can easily imagine the chief designer’s feelings, seeing his aircraft quite unwilling to fly, and when Orlebar pointed out to him that 247, the number of the first of the new machines, added up to thirteen, ‘the poor chap replied with feeling that he had not designed that’.
A solution to the torque problem at take-off would be found in later years with the invention of variable pitch propellers but, in the meantime, a special technique was worked out whereby it was necessary to keep the stick well back, contrary to all basic instruction, in order to maximise lift at the extreme low end of the aircraft’s airspeed. Additionally, the take-off had to begin with any breeze kept on the left quarter. This allowed for a nice judgement of acceleration while being pulled in an arc by the propeller torque to face directly into wind by the time that lift-off speed was attained.
To assist the pilots, Mitchell lengthened the starboard float by 1ft so that it could contain 90 gallons of fuel and allow the capacity of the submerging float to be reduced to 25 gallons. But having now achieved take-off, engine overheating was found to be a problem and so radiator piping had to be fitted along the sides of the floats. Small scoops were also fitted under the wing tips, facing forward and, with exhaust ports at the wing roots, creating a flow of air over the inner surfaces of the radiators – an unexpected bonus for using the radiators as load-bearing wing surfaces.
Once these problems had been overcome, and if one set aside the peculiarities of the take-off procedures, the S6s were proving to be viceless aircraft to fly and to have even better flying qualities than the previous, smaller, less powerful machine, despite the wing loading having now risen from 28 to 40lb/sq. ft. Waghorn wrote that, although she was a little heavier laterally, there was no noticeable torque effect against a left-hand turn which he had found tiring in the S5. He also found the new machine ‘extraordinarily stable at the stall’, whereas the S5 would quiver and ‘flick over either side at the slightest provocation’. The S6 showed no tendency to drop either wing, but would sink on an even keel – no doubt much appreciated by the pilots, as the ‘ground effect’ of the low wing and the highly streamlined fuselage created a long ‘float’ at over 100mph before final touch down.
Meanwhile, the two Gloster VIs were affected by ‘G’ related fuel starvation problems, and the Italians, the only other team to compete in 1929, were experiencing worse problems. They had also received their new aircraft late, and it was soon found that the hydrofoil equipped Piaggio P.7 was unable to take off at all, and one of the two Fiat C29s caught fire and later stalled on take-off and sank.
On the other hand, the first of the Macchi M67s was looking much more promising, reaching a speed of over 360mph, but then it too crashed, killing its pilot. Accordingly, Italy requested a one-month postponement on 22 August, but the Royal Aero Club stuck to the rules and refused the next day – the FAI concurred.
To prevent Britain winning by a fly-over, Italy decided not to withdraw from the competition and sent over their remaining, largely untested, aircraft – the second Fiat C29, a Savoia-Marchetti S65 and the two Macchi M67s – as well as two older Macchi M52s, one of which currently held the world speed record. By this time, both the Supermarine aircraft were ready but, as the Glosters’ fuel problems could not be solved in time, it was decided to call up one of the 1927 S5s.
Perhaps surprisingly, all the aircraft successfully complet
ed the competition navigation tests on 6 September and they were then all moored out for the watertightness test. Some time later, Mitchell, having been up late overseeing final preparations, was woken up in the officers’ mess. Atcherley’s N248 was listing, still with over two hours to go of the required flotation test. Mitchell decided that it would hold out long enough and went back to bed. By the due time, the machine had a very distinct list but was able to be beached and a leak repaired.
Then a further, more serious, problem was discovered, this time with Waghorn’s N247. Traces of white metal were found during the routine plug change and internal damage strongly suspected. The competition rules did not allow ‘any major component’ to be changed at this late stage, but it was at least possible to substitute parts. Orlebar has recounted that ‘poor Mitchell was hauled out again’ as the required removal and replacement of one of the cylinder blocks was going to present a problem.
Major overhauls would normally be carried out at Rolls-Royce with the engine removed from the aircraft but, at Calshot, it was necessary to devise some means of offering the intact machine up to the replacement block. Luckily, a number of Rolls-Royce mechanics had travelled to see the competition and they were collected from various hotels nearby. By working through the early hours of the morning, they were able to make the change, even without manoeuvring the aircraft. Their heroic efforts were proved entirely necessary, as it was found that one piston head and its cylinder lining was damaged and would have led, at the very least, to engine failure in the competition. The damage was traced to fuel being drawn into the engine during slow running before take-off and washing lubricant from the cylinder walls. It was thereafter decided that no engine was to have long periods of slow running prior to the beginning of the contest.
From Nighthawk to Spitfire Page 12
