Tuesday, 21 March 2017

Spitfire versus Hurricane – a 1920’s precursor.

Whilst the 69 foot span Swan was being prepared for its first flight, Supermarine departed from the usual designs of medium and heavy amphibians by requiring Mitchell to design a very small aircraft – a very light aeroplane and a landplane as well – and, incidentally, to compete with Sidney Camm, ten years before his Hurricane was first seen as a rival to the Spitfire in the race to produce a thoroughly up-to-date fighter as war clouds gathered.

R. J. Mitchell’s First Landplane – the Sparrow I.

Supermarine Sparrow (from a painting by the author)

Early in 1924, the Air Ministry announced a competition for two-seat, light, all-British aircraft to take place at Lympne in the September of that year. The  rules called for a winning aircraft which scored most points for combined high-speed and low-speed performance, control, shortest take-off and landing runs, and dismantling and re-erecting. The engine size was limited to 1,100 c.c.  Subsequently, the Air Ministry offered to equip ten light aeroplane clubs with a design selected from the competition aircraft. As club aircraft would have to be dual control two-seaters, established British companies took an interest, given the generally stagnant nature of the aircraft industry at the time,  and the large number of ex-service pilot in the country who also might be buyers. 
     Supermarine named their entry "Sparrow" and chose the 35 h.p. Blackburne Thrush to power it. Unfortunately, Biard, the test pilot, reported nineteen engine failures before the start of the competition and things did not improve at the competition itself. As a result, the Sparrow did not complete the preliminary flying tests and was eliminated.
     Most of the other major manufacturers had entered machines; the Bristol Brownie, the Beardmore Wee Bee, and the Short Satellite represented the monoplane approach to the specification and four were conventional single bay biplanes like the Sparrow: the Vickers Vagabond, the Avro Avis, the Westland Woodpigeon, and the Hawker Cygnet. The last three machines had full span combined ailerons and flaps like the Mitchell machine. In view of the later rivalry between the Hurricane and the Spitfire, Sidney Camm’s Cygnet was especially interesting as it embodied a formula even more similar to Mitchell’s Sparrow as it was also a sesquiplane. 

Unfortunately, the chance to compare different manufacturers' aircraft built to the same specification and at the same point in time, did not materialize: only eight of the nineteen entrants survived the eliminating trials and only six eventually competed – all but seven of the competitors failed because of some sort of engine problem and even a comparison between the survivors was not possible: ten trouble-free laps had to be completed and, by the last day of competition, only the Bristol and the Beardmore entries had done so – with their engines throttled well back. The fact that these two aircraft were monoplanes was not so much a vindication of the monoplane approach as a result of their particular engines holding out the best.
     The Air Ministry produced a report on the entries and, although recording the lowest landing speed and making a generally favourable impression, Mitchell’s Sparrow was also criticised for poor communication (as the tandem cockpits were well separated)  and for a less than satisfactory view for the forward pilot; it was also regarded as too cluttered with external control mechanisms (a not untypical feature of Supermarine's larger flying-boats of this time). Sidney Camm’s Cygnet, which had the best turn of speed, might very well have been considered by the Air Ministry for the proposed lightplane clubs, given a redesigned undercarriage and a widened fuselage but, in the end, no orders were placed for any of the machines: it had been clearly discovered that it would take much longer to develop a reliable power unit than to design a satisfactory airframe.

Sparrow II
Supermarine persisted with their aircraft, entering it in the 1926 Daily Mail Two-seater Light Aeroplane Competition. Again based at Lympne airfield, it required six days of out and return circuits, amounting to nearly two thousand miles of flying. The aircraft was now, wisely, fitted with the make of engine which had powered the two most successful aircraft of the 1924 Competition, a Mk.III version of the Bristol Cherub. Given the earlier criticism of  pilot view, Mitchell also abandoned the sesquiplane structure for a parasol high-wing replacement, the resultant aircraft being designated “Sparrow II”.

On September the 12th, the first day of flying, Biard took off but the weather worsened and, after less than thirty miles en route for Brighton, he decided that the strong headwind would not allow him sufficient fuel to complete the circuit. He returned to Lympne, refuelled and set off again. Unfortunately, over Beachy Head, his passenger, a Supermarine mechanic, noticed that one of the wing strut pins had nearly worked itself out. Biard hastily landed on the Head where the aircraft was immediately blown on its side. By the time that it had been righted and checked, it was too dark to attempt the return flight to Lympne and so an unhappy night was spent beside the machine. The next morning, Biard and his mechanic guided the Sparrow several hundred yards up the slope of Beachy Head whence Biard, leaving behind his passenger, turned downhill, successfully took off in the lightened plane and finally returned to base. However, the rules of the contest stipulated that each of the six circuits had to be completed within the day allotted and thus the Sparrow II was eliminated. In the event, the competition was won by Sidney Camm's Cygnet.
     Thereafter there was an Air Ministry contract for flight comparisons of identical area wings with different aerofoils –  for which the parasol wing configuration of the Sparrow II was very suitable as it kept interference effects of the fuselage to a minimum.
The machine was then put into storage at Hythe until May 1929, when it was registered G-EBJP and went to the Halton Aero Club. It may have survived until as late as 1933 but it does not appear to have been extensively used. 

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For reference sources, see my Blog: “Source Material and References. " An extended bibliography is included in my R.J.Mitchell at Supermarine; Schneider Trophy to Spitfire  which also provides material for wider reading, grouped according to specific areas of interest. 

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