The Farman Biplane.
Discontented with the Voisin machine, Mr. Henry Farman constructed one of his own design. Though it appeared at an early stage of aëroplane development, it still remains one of the most efficient types of biplanes. It has been used enormously in France, and armoured Farmans play an important part in the great war that is proceeding.
Mr. Farman quickly realised that for maintaining lateral stability the vertical planes fitted between the main planes of the Voisin type were a very poor substitute for the wing-warping method of the brothers Wright. He, however, produced the movement of the main surfaces in an original manner. He hinged small flaps to the rear extremities of the main planes. These he called “ailerons.” They produce much the same effect as the wing-warping method of the brothers Wright. When the biplane tilted sideways, the flaps were drawn down on the side that was depressed. The pressure of the air on the flaps forced the aëroplane back on an even keel. In the normal condition the flaps flew out straight in the wind on a level with the main planes. Another noticeable feature of Mr. Farman’s machine was the production of the first light and efficient landing chassis. This was a combination of wooden skids and bicycle wheels. Below the biplane, on wooden uprights, he fitted two long wooden skids. On either side of each skid he placed two little pneumatic tyred bicycle wheels, connected by a short axle. These were held in position on the skid by stout rubber bands passing over the axle.
In a general way the wheels raised the skids from the ground, but if the ascent was abrupt the wheels were forced against the rubber bands and the skids came in contact with the ground. With the abatement of the force of the shock the wheels came again into play.
Simplification of the chassis is becoming evident in the latest forms of all military aëroplanes, the reduction of weight in this portion of the apparatus being important.
To Mr. Farman belongs the credit of having first applied to his aëroplane the now famous Gnome motor, in which seven or more cylinders revolve. It can truly be said that the influence of this motor on facilitating flight generally, and very particularly military aviation, has been nothing short of prodigious. The aëroplane, like the airship, had to wait for the light petroleum motor. Its advent made flight possible, but achievement in flight would have been comparatively small had it not been for the welcome appearance of a motor specially adapted to the purpose.
The early forms of aëroplane engines in which the cylinders were fixed had proved to be quite unreliable owing to the high speeds at which the engines had to work. Overheating, loss of power, and stopping were frequent occurrences. The water-cooling and air-cooling systems introduced were equally inefficient. The very fact that the cylinders of the Gnome motor revolved effected the desideratum of automatic cooling, and also gave a smooth, even thrust to the propeller.
If the aëroplanes in the present war were flying over the enemy’s lines with old-fashioned engines, they would be dropping down into hostile hands as quickly as dying flies from the ceiling on the first winter days.
After the introduction of the Gnome motor, it was quickly realised that the speeds secured by its use gave the aëroplane a stability that was absent in the more slowly moving machines. Winds that were the bugbear of the aëroplanists could then be combated, and the aëroplane ceased to be the fine-weather machine. Heights could then be climbed that a little while before were undreamt of. It is said that there are some disadvantages in the case of revolving cylinders—that they have been known to produce a gyroscopic effect that has upset the machine. This, however, is a somewhat doubtful point. It may be urged that the greater silence of motors with fixed cylinders is an advantage in war. This may sometimes be so, and it is quite possible that for offensive aëroplanes a special type of motor may be in the future evolved.
To return to the other features of the Farman machine. The plan he adopted in his racing machines of making the upper plane larger than the lower one was a valuable step in speed-producing machines.
The records won by Mr. Farman with his machines alone testify to its efficiency. Often he has held the world’s records of distance, duration, and height, wrestling, indeed, for these with the Blériot monoplane.
In 1911 Mr. Farman began to make types of biplanes specially designed for military use, and in which he studied how he could best give the observing officer an unobstructed view of the ground beneath him. He placed both pilot and observer in seats projecting in front of the main planes. He also made a new departure in placing his upper plane in advance of the lower one. He claimed that this facilitates climbing and descent. He has, however, quite lately evolved a newer type of scouting machine.
In this the lower plane is only one-third the span of the upper one. The nacelle is not mounted on the lower plane, as in the ordinary types of his machine, but, instead, strung from the main spars of the top one. The usual chassis is absent. There is a single running wheel mounted at each end of the lower plane, which is brought very close to the ground. The upper and lower planes are separated by four pairs of struts. The tail is similar to that used on the ordinary type.
The following are the dimensions of one of the latest 1914 types of one-seated Farman machines:—
| Length | 3.75 metres |
| Span | 11.50 metres |
| Area | 26 sq. metres |
| Weight (total) | 290 kgs. |
| „ (useful) | 175 kgs. |
| Motor | 80 h.p. Gnome |
| Speed | 110 km. per hour |
The following are the details of one of his high-power hydroplanes (1914):—
| Length | 8.80 metres |
| Span | 18.08 metres |
| Area | 50 sq. metres |
| Weight (total) | 605 kgs. |
| „ (useful) | 275 kgs. |
| Maximum speed | 105 km. per hour |
[Topical Press.
A BLÉRIOT MONOPLANE IN FLIGHT,
showing one of the two wings attached to the tubular body of machine, chassis, stabilising plane, and rudder at rear.