Marked for Death

by James Hamilton-Paterson

  The generic problem with biplanes of all kinds was always going to be that of drag, which in turn would limit speed and demand ever more power to overcome it. Biplanes needed struts and wires between the wings, and it hardly helped that they also had fixed undercarriages, a further potent source of drag. There was simply a mass of stuff obstructing the airflow and contributing nothing in the way of lift. In the earlier part of the war aircraft were practically always of all-wood construction, although as engines became more powerful and weight a little less critical metal began to be used for certain parts of the airframe. It was all a matter of weight and the availability of materials. Aerodynamicists realised that in the end the only way to make an aircraft fly faster was to reduce drag and go back to monoplane design; but the problem remained of how to make a cantilever wing stiff enough to withstand the twisting and flexing forces of high-speed manoeuvres. Wood and contemporary glues lacked strength. Making main spars of steel would be too heavy. What was needed were light alloys, but the sort of metallurgical research needed to develop and test them was very time-consuming and besides, even if the ideal metal – both strong and light – were found, the uncertainties of wartime supply made it unlikely that any sort of mass production could be reliably undertaken. At the same time aviation-quality seasoned wood of all kinds became progressively scarcer as the war went on and frames of steel tubing and even monocoque (stressed metal skin) construction were introduced here and there before the war’s end, most notably by German companies like Junkers. It is a measure of the difficulties that only in the early 1930s did all-metal structures slowly become the norm for larger aircraft, while military biplanes persisted here and there even into the Second World War (the Gloster Gladiators that defended Malta in 1940, for example). These late biplanes now had metal frames even if their flying surfaces were still partially covered with fabric. Debatably the most impressive, as well as the fastest, biplane fighter of all time was the Italian Fiat CR.42 ‘Falco’ that flew in numbers in several theatres in the Second World War. It was actually a sesquiplane, its lower wings being much shorter than the upper. Yet although outstandingly manoeuvrable and quick, it was ultimately no match for that war’s potent all-metal monoplane fighters. Even so, wood continued to be used to advantage in certain airframes, most notably in the Hawker Hurricane and the de Havilland Mosquito.

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  Manoeuvrability was always going to be a critical factor in aircraft and its development was much accelerated by the requirements of war flying. For some time, though, what pilots could do in the air was limited not merely by their machines’ structural weakness but by an incomplete understanding of aerodynamics. In addition, the conservative way in which pilots were trained deterred them from performing certain evolutions. By 1914 rolling, diving and even looping an aircraft were all crowd-drawing novelties at any air show, thrilling spectators with both the spectacle and the likelihood of disaster. However, at that time the RFC actively discouraged such ‘stunting’ by its own pilots as being no better than vulgar showing-off. This revealed how very far the British Army still was from recognising the need for pilots skilful enough to fight rather than just to act as chauffeurs for their observers. For at least the first two years of the war stalling and spinning remained aviation’s great bugbears, to be avoided at all cost. In particular, spinning was a phenomenon that scared pilots everywhere simply because nobody really understood its cause, still less how to stop it and regain control.

  It was recognised that the main way to trigger a spin was by losing flying speed. The stall at Hendon that Louis Strange survived showed classic symptoms, and had it occurred at a higher altitude – say 500 feet – the Morane would undoubtedly have spun into the ground. Strange’s observation that the aircraft gave a ‘stagger’ is an exact description of the buffeting that occurs at stalling point. In his case the Morane’s left wing stalled first, losing all lift and gaining drag, while the right wing maintained lift and so swung up and around. Luckily for Strange and Marty they were still low and impact with the ground prevented this from developing into a full autorotation that the pilot appears helpless to stop. Several showmen of the day claimed to be able to spin at will, but there is no reliable evidence for this. What they were probably doing was known then as a ‘tourbillon’ spin: essentially a tight downward spiral as opposed to autorotation. In other words they were maintaining airspeed and were under control, effectively rolling the aircraft but vertically downwards instead of horizontally. All they had to worry about was being able to pull out high enough above the ground without their wings folding up under the strain. A genuine spin was a very different matter and for a while it was nearly always fatal.

  At six in the morning of 25th August 1912 a young naval lieutenant, Wilfred Parke, and his RFC observer took off from the Army’s Larkhill aerodrome on Salisbury Plain in an Avro biplane for a three-hour qualifying flight. They returned to the airfield at nine o’clock at an altitude of around 700 feet and Parke banked the machine to lose height in order to land. Thinking his angle of descent too steep, he pulled back on the control wheel and the machine immediately stalled and whipped into a left-handed spin. The technical editor of Flight described it for the magazine’s next issue:

  [T]he machine was completely out of control, diving headlong at such a steep angle that all the spectators described it as vertical and stood, horror-stricken, waiting for the end. According to Parke the angle was very steep, but certainly not vertical; he noticed no particular strain on his legs, with which he still kept the rudder about half over to the left (about as much as is ordinarily used in a turn), nor on his chest, across which a wide belt strapped him to his seat. His right hand he had already removed from the control wheel in order to steady himself by grasping an upright body strut… This he did, not for support against the steepness of the descent but because he felt himself being thrown outwards by the spiral motion of the machine, which he describes as ‘violent’. It was his recognition of the predominating influence of the spiral motion, as distinct from the dive, that caused him to ease off the rudder and finally push it hard over to the right (i.e. to turn the machine outwards from the circle), as a last resort when about 50 feet from the ground.

  Instantly, but without any jerkiness, the machine straightened and flattened out – came at once under control and, without sinking appreciably, flew off in a perfect attitude, made a circuit of the sheds, and alighted in the usual way without the least mishap.24

  This incident became famous in aviation circles as ‘Parke’s Dive’, and remains the first known detailed description of an aviator surviving an unintentional spin. It so happened that the Royal Aircraft Factory at Farnborough had recently been asked to investigate the phenomenon of spinning and by good fortune the young Geoffrey de Havilland was present at Larkhill that day as their representative. He promptly debriefed Lieutenant Parke at length in the mess. It seems unlikely that Parke would have had much of an appetite for breakfast and his observer – who had worn no seatbelt and had been pinned helplessly to the side of the aircraft by centrifugal force – still less. But de Havilland, self-taught pilot that he was, must have clearly noted the lesson of Parke’s Dive because at some date in 1914 he deliberately spun an aircraft knowing how to regain control.

  Dunstan Hadley, a Fleet Air Arm pilot who flew Fairey Barracuda torpedo-bombers in WW2, made a particular study of the history of spinning and consulted records in the USA, France, Italy and Germany as well as in the UK. He concluded that Geoffrey de Havilland was ‘the first British pilot to have spun intentionally, knowing he could recover; and until any earlier claim is discovered and verified, it stands as both the British and world record for the earliest known deliberate spin’.25 As for Lieutenant Parke, he had just under four more months to live, being killed while flying a Handley Page Type F monoplane when it suffered engine failure on a flight from Hendon to Oxford in December 1912. He was twenty-three.

  Thereafter, one would have thought the method for getting out of a
spin would have spread like wildfire throughout the flying fraternity – reduced to a life-saving mantra such as Full opposite rudder, stick centred, throttle back or, a little later, Throttle back, stick forward, pause, opposite rudder. Yet the mere fact that spins were still almost superstitiously feared four or five years later shows it did not. Even a pilot as accomplished as Cecil Lewis was clear on that point:

  In 1916, to spin was a highly dangerous manoeuvre. A few experts did it. Rumour had it that once in a spin you could never get out again. Some machines would spin easier to the left than to the right; but a spin in either direction was liable to end fatally. The expression ‘in a flat spin’, invented in those days, denoted that whoever was in it had reached the absolute limit of anger, nerves, fright, or whatever it might be. So spinning was the one thing the young pilot fought shy of…26

  Even so, 1916 was also the year Major Lanoe Hawker, VC, put his DH.2 through a series of spins above his squadron’s airfield to demonstrate to his assembled pilots that this aircraft’s reputation for fatal spinning was unwarranted, and that it was perfectly possible to spin it deliberately and regain control.

  Part of the reason for this fear must also have been that for many pilots the remedy for a spin was counter-intuitive. One instinctive reaction was to freeze and steer into the spin, as though to mollify the machine by going along with it before finding a way of coaxing it out of its disorder. Yet any horseman would know that was fatal. It required a masterful hauling of the beast’s head round, using strength. Full opposite rudder. Also, if you were heading for the ground out of control, the last thing you felt like doing was pushing the stick forward. Yet the chances were the stall occurred in the first place because you had the stick back and had lost flying speed. It was soon learned that each aircraft, as well as every type, could have slightly different stall and spin characteristics. Even so, it would not be until 1925 that the RAF made it mandatory for a company’s test pilots to complete spinning tests on any new aircraft before it was accepted for trials by the RAF’s own test pilots.

  As combat became more aerobatic during the war, the more adventurous pilots did learn to spin at will, knowing they could recover, and it became a trick used to simulate being shot down in order to fool an opponent. Yet by no means every pilot either mastered it or wished to try. Spinning in general went on having a bad reputation, while particular aircraft became notorious for it. A centre of gravity too far aft was always a danger sign. An additional problem was that the slightest alteration to the airframe – putting on an external mount for a camera or adding a fairing behind the pilot’s head – could sometimes drastically change an aircraft’s spin characteristics and a new set of trials would be needed. As Dunstan Hadley observed, ‘Even by the 1930s the dynamics of the spin were imperfectly understood and trial and error was very much the order of the day.’ It should be added that much the same applied to the stall, which continues to be a problem to this day, as witness several recent accidents to commercial airliners involving the loss of all on board. Any complacency in flying of any kind sooner or later proves fatal, as does putting too much faith in training pilots entirely in simulators in order to save money. There is no substitute for live cockpit experience, preferably including a couple of hundred hours in light aircraft or gliders.

  Quite apart from pilot training, though, it should be remembered that every light aircraft has a personality of its own: not just the different types but each individual machine. It can differ in ways no rigger or fitter or mechanic can account for, acquiring a reputation for docility or sluggishness, the engine not giving full revs in a steep turn or overheating, even occasionally making a mysterious faint whinnying sound like a pained horse. Some aircraft feel eager to fly as soon as the engine starts, others much less so. It can’t be explained. (Many drivers feel the same way about cars.) This was especially true in the First World War when so much production was farmed out to various factories, each of which had slightly differing work practices according to what they had been making before the Munitions of War Act obliged them to build aircraft. The machines they turned out may have looked identical – may have been identical in the sense of meeting specifications – but they seldom flew identically.

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  In many ways it was the engine as much as a growing understanding of the basics of flight that determined the progress of early aviation. Weight was absolutely critical, and power-to-weight became a ratio that haunted every aircraft designer. It can be argued that an equal hero of the Wright brothers’ first controlled and powered flights was their mechanic, Charlie Taylor, who was asked to provide an engine for what was essentially one of the Wrights’ manned gliders. In the absence of any existing engine light enough to power an aircraft weighing only 604 lb, Taylor built a 12 h.p., four-cylinder inline engine whose block was cast aluminium. He did it from scratch in six weeks and the resulting engine weighed a mere 180 lb. For its time it was a masterpiece of off-the-cuff engineering.

  On the other hand, it was weak. French aviation pioneers like the Voisin brothers were not satisfied with the Wrights’ top airspeed of 30 mph in 1904. This was, after all, the year Henry Ford set a new land speed record of 91 mph. They turned to the rotary engine. This was originally a French invention, although by the turn of the twentieth century it had been developed elsewhere, notably in the United States for use in cars. Now the three Voisin brothers set up a rotary aero-engine business called Gnome, which along with Le Rhône and Clerget was to become a major engine supplier to the Allies during the war. Many companies also made Gnome rotaries under licence, especially in Germany. Trade was trade, even in wartime.

  Rotary engines look like radial engines in that both have their cylinders arranged as a ‘clock face’, but they function quite differently. A radial engine, like a car engine, is stationary and turns a crankshaft in the normal fashion, whereas the rotary’s crankshaft is fixed and the entire block of cylinders turns around it. If it is to be used in an aircraft, a propeller is simply bolted to the front of the rotating engine. By modern standards this may seem a bizarre arrangement but in the early days of aviation it offered important advantages over a conventional stationary engine, the main one being that it had an impressive power-to-weight ratio since it was very light. As the cylinders whirled around they cooled themselves in the air and there was therefore no need for a bulky system of radiators and water jackets. Secondly, a rotary engine ran very smoothly because the whole thing acted as a flywheel. And thirdly, it was extremely compact, amounting to little more than the clock-face of cylinders with its circular sump in the middle, like a fat hub surrounded by spokes. This compactness was a useful feature, and in a fighter like the Sopwith Camel it meant that the first seven feet of airframe could accommodate the entire ‘works’: engine, fuel tank, guns and pilot. This design led directly to that fighter’s hair-trigger handling which was to gain it so many combat victories.

  But back in the summer of 1914 it is practically certain that not a single British military aircraft that flew in the first batch to France had a British engine. Initially, our development of both aero engines and aircraft was seriously hampered by a chronic lack of machine tools, ball bearings and magnetos, as well as steel and alloys of sufficient quality. Britain, the erstwhile cradle of the Industrial Revolution, now had only a single ball bearing factory capable of bulk output and supplies had to be imported urgently from Sweden and the United States. As for magnetos, home-grown production proved equally inadequate and until mid-1916 the RFC relied largely on a pre-war stockpile of German-made magnetos to enable its aircraft to fight Germany.27 By 1918 the desperate modernization of British industry had gathered considerable pace and things had much improved. Even research into new alloys had become advanced.

  For the first two years of the war, however, the RFC was almost entirely reliant on French-designed rotary engines. In fact, in August 1914 there were only two British-designed aero engines being built, the 60 h.p. Wolseley that powered the earliest B.E.1 and S
unbeam’s 120 h.p. Crusader. Both were V-8s and as such were bulky and heavy for their output. Rotaries were the obvious choice: it was a capable and ingenious design. Tens of thousands were built by all sides throughout the war, and yet they virtually disappeared the moment the Armistice was signed. By then their drawbacks had exceeded their usefulness.

  While the rotating engine did indeed provide smoothness, it also produced a powerful gyroscopic effect that could make an aircraft easy to turn in one direction but less so in the other. This feature became notorious in Sopwith Camels, which were typically powered by the 130 h.p. Clerget engine. That aircraft also had a marked tendency to swing on take-off and landing, one of several tricky features that led to countless crashes in training. Because rotaries lacked carburettors they were tricky to control with a throttle. They tended to run ‘full on’, and the normal way to reduce power was by using a cut-out switch that prevented every other cylinder from firing and required repeated ‘blipping’ of the engine. This – together with a fuel-air mixture control that demanded constant monitoring – made flying all rotary-engined aircraft a handful, and the Camel most of all. Rotaries also worked on a ‘lost oil’ principle that used great quantities of castor oil, much of which was sprayed back half-burnt over the pilot.

  None of this was ideal, although it had to be lived with at the time. The real reason why the engines fell out of fashion so quickly after the war was because aircraft designers wanted more and more power. Rotaries were comparatively slow-revving and the propeller could only turn as fast as the engine, unlike stationary engines where the power could be greatly increased and the propeller geared for maximum efficiency. (The underlying problem is that petrol engines reach their maximum efficiency at relatively high speeds, whereas propellers are more efficient at lower speeds.) During the First World War rotaries were developed as far as they could be, even acquiring a second bank of cylinders ‘staggered’ with respect to the first. The high point was probably reached with the Bentley BR.2, a magnificent 25-litre rotary engine whose single bank of nine cylinders produced 250 h.p. But rotaries had reached their limit for reasons of simple physics. The faster the cylinders whirled, the more the drag on them increased (since drag in air increases with the square of the velocity). But the power needed to overcome drag is the cube of speed, and very soon a point was reached when much of a rotary engine’s power was spent in making itself turn.