Hugo Byttebier - The Rise of the Flying Machine

Maxim was now at the point where free flight could be contemplated, a flight which in 1892 he had imagined could be as follows: “Taking one man with us to attend to the two horizontal rudders and to keep the machine on an even keel, we should make our first flight, running the engines and doing the right and left steering ourselves. A day should be selected when there is a fresh breeze of about 10 mph. We should first travel slowly around the circular railway until we came near that part of the track in which we should face the wind. The speed should then be increased until it attained a velocity of 38 or 40 mph. This would lift the machine off the track and probably slightly change the centre of effort. This, however, would be quickly corrected by the man at the wheel. While the machine is still in the air careful experiments should be tried in regard to the action of the rudders... trying the effect of running one propeller faster than the other, to ascertain to what extent this would have to be done in order to cause the machine to turn to the right or to the left...”

“A large field as near to our railway as possible should be selected for alighting, and having approached the field so as to be facing the wind, we should gradually descend by slowing up the engines, and finally alight while the machine was still advancing at the rate of 20 mph. If the wind were blowing at the rate of 20 mph the machine would approach the earth very gradually indeed, so that all shock would be avoided. It would only require a few yards of comparatively smooth ground to run after alighting, in order that there should be no disagreeable shock or danger.”

This was not an inaccurate description of an actual flight, although the landing speed of 20 mph was a bit on the low side, but no free flight was ever attempted, certainly not after the crash of 31 July 1894.

“A hundred necks have to be broken, before all sources of accident can be ascertained and guarded against” wrote Cayley in 1846 with his usual acumen. Maxim did not offer his own neck to be the first. He had become aware of the fact that a free flight might possibly not be such an easy affair as he had suggested in 1892 and it was as well that he did not press his experiments any further.

Maxim’s flying machine, with its two movable rudders was, like Ader’s, longitudinally unstable and had to depend on the continuous intervention of a man at the wheel or wheels to actuate those rudders and, however quickly he tried to correct the balance, it would soon have been beyond that man’s capacity. For a time Maxim toyed with the idea of installing a gyrostat for automatic balancing, but he decided to let the matter drop.

In the evolution of the heavier-than-air flying machine, Maxim was the first to take off under his own power and also the first to produce sufficient power to achieve the feat and, although his craft never actually made a completely free flight, it did fly.

The cost of his experiments has been estimated at $200,000. After the accident of 1894, the plane was repaired and Maxim made several more runs, although he never left the boundary of the restraining upper planks, and limited the steam pressure to the extent that this restraining mode of flight could be made with safety.

He later continued to work, to invent, to write and to lecture, and in general took the necessary steps to ensure that posterity would not forget him, and in this he was certainly successful.

Lilienthal’s Flights

Lilienthal started to fly in July 1890. He was able to finance his experiments with the proceeds from a workshop that he owned, so that he was never short of funds and did not have to appeal to third parties for financial assistance and suffer the inconveniences that sometimes result from this.

His first glider consisted simply of a pair of wings with a surface of 107 sq ft. On his first attempt to glide, he started from a slight rise in a field, in a fairly strong wind of 18 mph but the craft overturned and crashed.

A new glider was then built, in which the wing area was reduced to 86 sq ft and, in a first endeavour to stabilize the flightpath, a fixed vertical tail was added to the rear. With this glider, Otto Lilienthal achieved a few successful glides starting from Windmühlenberg at Dernitz, not far from Berlin. In 1891 he was able to cover distances in the air of up to 100 ft but the wing proved too small for successful lifting in the moderate winds which were then a prerequisite for safety.

In 1892 he built a new glider, doubling the wing surface to 172 sq ft, so that flights with little wind became possible. His apparatus was first tested in Steglitz from the roof of a shed, which was built on a slight rise.

This shed limited flights to only a few directions so Lilienthal then decided to build his own artificial hill in the form of a cone 50 ft high near Heimersdorf, not far from his home in Lichterfelde. The top of this hill was crowned with a shed in which Lilienthal housed his aircraft. He was now able to glide downhill in whatever direction the wind blew, whilst the wind was forced upward along the slope of the hill, so that take-off became possible after running a few feet.

From this hill Lilienthal was able to make many impressive glides, and because of this the place became a favourite spot for a family excursion for many Berliners.

Meanwhile, through trial and error, Lilienthal discovered the concept of the stable aeroplane and, possibly without being aware of Pénaud’s designs, he adopted a horizontal and vertical fixed tail at the rear of his gliders and with this his flights improved immeasurably. At Steglitz he made several glides of 80 m (285 ft) in the air and from his artificial hill he did even better.

But the Heimersdorf hill still had a defect in that the wind was apt to be deflected laterally. Lilienthal continued with his search for a better jumping-off point and, later in 1892, he found the “Rhinower Mountains” which were about 35 miles west of Berlin. They consisted of a series of elevations which rose about 200 ft above the surrounding terrain of flat fields covered with grass and heather.

Lilienthal continued his gliding experiments in the Rhinower Mountains over the following years and became so proficient in flying against ever stronger winds that he was eventually able to cover distances of over 1,100 ft in the air.

Commenting in his annual report on his flights during 1892, Lilienthal stated: “Each apparatus had a vertical and horizontal tail without which it is impracticable to practice in the wind.” In order to control and steer, Lilienthal applied the principle of displacement of the centre of gravity by moving his body. This was the simplest way to steer a stable light gliding craft and is still used in today’s hang-gliders.

It is interesting to note that the tail surfaces mentioned by Lilienthal were fixed, so that they were meant for inherent longitudinal and directional stability, whilst the movement of the body was used for control and only incidentally for aid in balancing the aircraft.

In his report about his flights in 1893 Lilienthal wrote: “A slight change in the centre of gravity to one side produces at once a small inclination to the carrying surface so that the supporting air pressure also moves to this side and changes the direction of flight. There is nothing simpler than steering flying machines.”

It may be said that during 1893, Lilienthal acquired the art of sailing or gliding flight to perfection. From then on he began to consider the possibility of carrying out his original aim, which was to build a machine using powered flapping wings for true bird-like flight. Although his experiments had convinced him of the importance of the inherently stable aeroplane, he still wanted to use flapping wings for propulsion.