A machine was built by the Farman company and pedalled by Gabriel Poulain over the specified distance in both directions early on the morning of 9th July 1921 with Robert Peugeot watching, with a distance of 11.98 metres. (Incidentally, two weeks later, the long-jump record was reset at 7.69 metres by Edwin Gourdin on 23rd July 1921 in Cambridge Massachusetts. ) The Poulain Farman machine was undoubtedly a human-powered-vehicle. It was a biplane with a span of 20 feet (6 m) and a wing-area of 132 square feet,(12.08 m2) (i.e. larger than some wings built for the purpose of true human powered flight in the 1960's). There was a fairing around the person and bicycle. There was no propeller and there were apparently no aerodynamic controls. The total weight was 201 lbs.(91 Kg)
The lifting force, (lift) produced by a wing is mainly a function of the area of the wing(s), the density of the air, the speed of the wing relative to the air and the shape of the wing section. The other factor is the viscosity of the air, (see Reynolds number in Glossary). The section shape and its angle relative to the motion determines the factor Cl or "lift coefficient" in the formula
L = Cl x ro/2 x V2 x S
where L = lift, ro = air density , V = velocity and S = area. Cl is a pure number (dimensionless), hence if one converts to a different system of units its value is unaltered.
In round terms, one might assume that Poulain's wings achieved a lift coefficient of 1. Assuming also the typical sea-level value of air-mass-density of 1/420 in the ft/lb/sec system, and knowing the wing area and the weight that was needed to be lifted, one may state :-
210 = 1 x 1/840 x V2 x 132
which gives V = 36.5 ft/sec or 25 mph
However, to have travelled 11.98 metres (39.3 feet), he would have needed to be moving faster than this when leaving the ground. A rough estimate of this extra necessary speed can be made by assuming a glide-ratio of 5/1, (typical for hang-gliders), that is he could have travelled 39.3 feet forward while losing 39.3/5 = 8 feet in altitude whilst maintaining the same speed. The extra energy needed is the same as that needed to climb this height. The calculation is done most simply by converting the forward speed into its equivalent height using
height = 1/2 x 1/g x V2 = 1/2 x 1/32.2 x 36.5 x 36.5 = 21 ft
Hence total equivalent height is 21 + 8 = 29 ft which is equivalent to a speed of half of 1/g times the square root of 29 = 43 ft/sec (29 mph).
Hence, assuming a lift coefficient of unity this would imply a minimum flying speed of 25 mph, and if we assume a glide-ratio of 5 then Poulain would have needed to achieve 29 mph just before take-off to provide the momentum to carry through the air over the distance. Poulain was a racing cyclist and an experienced pilot. Is it a bike ? is it a plane ? No, it was a machine which had been optimised over nine years purely for the purpose of winning the Peugeot prize, and was demonstrably the appropriate vehicle for the purpose. Poulain and the Farman company succeeded with this simple layout against a competition of machines with flapping wings and propellers, some of them being tricycles or having other appendages adding to the weight and drag. There is no record of anyone else operating this machine, or of whether it was stable or whether Poulain personally had gradually to acquire the specific knack of controlling it. Clearly, without some sort of drive when airborne, one will not get very much further than this, but note that all those of the early aircraft which intended unaided take-off, and some of the later ones, used drive to the ground-wheel as well as to the propeller.
Dr Alexander Lippisch, a prolific designer of sailplanes and other aircraft, built an ornithopter (see Glossary) in 1929. This was always launched like a glider (Lippisch 1960). The principle Lippisch used relied on the wings twisting during the flapping cycle. In general, on an aircraft the centre of pressure of the lift will not remain on the axis of the spar during flight. This offset loading will tend to warp the wing. On almost every other aeroplane this is a problem which must be overcome, usually by making the wing structure stiff enough to resist this torsion. But on this aeroplane, Lippisch tried to make use of this effect; the extra, and different, forces on the wing during the downstroke would hopefully warp it more. Hence, the effect of the wing flapping would propel the plane on a similar principle as a fish's tail propels a fish.
However, for one reason or another it did not work. Perhaps the wing was too torsionally stiff - again the opposite of what is unfortunately more common. Lippisch added flexible extensions behind the trailing edge and it was then found that flapping of the wings slightly prolonged the flights, but he could not understand the still disappointing results until he realised that the pilot, Hans Werner Krause, was not really pulling very hard, and didn't see the point of it. He then offered to pay Krause's rail fare to see his girl friend for the weekend, if he were to fly from the usual launch point over a specified puddle about 300 yards away. The course was covered on the first attempt.
MUSKELFLUG INSTITUT (Institute of Muscle-Powered-Flight)
This was set up in 1935, within the Gesellschaft Polytechnic, Frankfurt. Oskar Ursinus, director saw as the prime question the determination of power available (from a a person`s muscles). A prize was offered for the first flight in Germany over a 1 km course. The data from his tests on muscle-power were made available to designers in 1936. Unfortunately no further research could be carried out by the Institute because of the onset of war.
This was the only relatively successful contender for the prize offered by the Muskelflug-Institut. Helmut Haessler finalised his design in 1935. His estimate of the available power was too high. Eventually, since the results of the tests from the Institut were not published he and a colleague Franz Villinger performed their own tests on human-power by having one cyclist tow another who read a spring balance on the handlebars attached to the tow-line. " It was not realised until our own tests and those of the Muscle Flight Institute, which was founded later, had been done, that the earlier data gave more than double the actual power." (Villinger 1960) None of these human-power data mention the weight of the person producing it. Franz Villinger and Helmut Haessler were both experienced in aircraft through their employment at Junkers. The neatness of the configuration and the similarity to a sailplane conceal some subtle points. The length of the drive is very short and the propeller-support-pylon and wing do not interfere aerodynamically as they do on some later machines. (See below re Interference Drag). The frontal area is desirably low, although this meant that it was most awkward for the pilot to get into or out of the Mufli.