Marked for Death by James Hamilton-Paterson Read Free Book Online Page B

way a wing works. Its cambered shape produces a drop in pressure in the airflow as it passes over its curved upper surface, creating a vacuum effect that ‘sucks’ the wing upwards. At the same time the flatter underside of the wing, at an angle to the airflow (the ‘angle of attack’), produces an increase in pressure that ‘pushes’ the wing upwards. Both these forces togetherproduce lift. In a biplane, though, with one wing above the other, there is interference between the positive pressure beneath the upper wing and the negative pressure above the lower, cancelling some of the potential lift. It was for this reason that, as the war went on, aircraft designers tried either increasing the distance between the top and bottom wings or else ‘staggering’ them so they were not directly above each other. Usually the top pair was placed slightly ahead of the bottom pair.
    It was soon discovered that, with careful placing of a biplane’s centre of gravity and by not designing it for stability at all costs, it could be made much more agile if often trickier to fly. This might be achieved by ‘short-coupling’: reducing the length of the fuselage so the aircraft became stumpier. There were subtleties of fine-tuning, too. The diagonal wires between the pairs of wings could be tightened or slackened by means of turnbuckles. By careful alignment of the tail with the centre section (the roofed ‘box’ of struts that surrounds the cockpit), the aircraft could be deliberately trimmed to fly in a particular way. ‘Tuning’ a biplane to suit its pilot became a valued skill on the part of his rigger mechanics.
    Sundry variations in design were tried during the war, including that of adding a third pair of wings. The first triplanes to be seen were the big Voisin bombers of 1915 and 1916, when a third wing was very obviously a load-bearing measure. When Britain’s Sopwith company came up with the first little triplane fighter in 1916 it seemed revolutionary. It was found that three pairs of somewhat shorter wings could confer amazing agility in the air and the design of the ‘Tripe’ was quickly copied. As mentioned earlier, a plethora of different triplanes came from Austro-German manufacturers, most notably Fokker’s Dr.I which today is most associated with Baron von Richthofen. Yet the triplane craze was short-lived. While increasing the number of wings can indeed increase lift, it also adds weight and drag. The Dr.I was noticeably slower than many of its contemporaries and although initially it climbed well it soon became sluggish at altitude.
    The French company Nieuport, which built some of the war’s most successful fighters, went in another direction, that of the sesquiplane. This literally means ‘a wing and a half’, and the Nieuport design was a biplane in which the lower two wings were much narrower and shorter than the upper. They were pretty machines and generally very agile. The flying aces Eddie Rickenbacker, ‘Billy’ Bishop, Albert Ball and Charles Nungesser all flew Nieuports for preference at one time or another. They liked their manoeuvrability and responsiveness to the controls. But even they needed to be careful not to over-stress the aircraft because the narrow lower wings suffered from the same old problem that monoplanes had: they couldn’t be built rigid enough to withstand too much torsion, and the twisting forces sometimes caused the wing to fail, which usually led to the break-up in mid-air of the entire machine.
    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