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Development of landing gear

When the first aircraft began to be designed and built, aeronautical pioneers of the time had a small problem to solve: how to support the aircraft on the ground.

Until the end of the 19th century it was the pilot’s own body that was tasked with this mission, in particular their legs. They served to start a run during the doubtful moment of take-off, and to brake once back on the ground. Needless to say, bone fractures were practically inevitable for those early air pioneers.

Landing gear is one of the most visible systems on aircraft, but it is hardly ever granted the importance and prominence it really deserves.

It was not until the early 20th century that consideration was given to the use of more robust support that was less jeopardising to the health of the crew. In 1903 the Wright brothers carried out their first flight with the Flyer using a kind of sled whose sole mission, without going into the technical complexities, was to support the just over 220 kg of aircraft.

In fact, the first landing gears were generally little more than skids, which from 1906, with the flight of the Santos Dumont 14-bis model, began to be replaced in general by small wheels. The incipient (or non-existent) suspension system did not have major requirements, given the speed and weight of those early aircraft (which were made of wood and canvas), so it was a simple system based on rubber bands and reticulated structures.

The wheels were also small in the first prototypes. The lack of specialisation of this element of the aircraft even led on many occasions to the use of wheels that had been initially manufactured for bicycles.

At this time, landing gears were, of course, fixed. There was no need to hide them, given their limited influence on the aerodynamics of the aircraft, which at the time were flying at low speeds. It was only from 1920 that the first retractable models started to appear. The first aircraft that used them was the Dayton Wright RB-1, which had a mechanical activation system by means of a lever operated by the pilot.

Even so, for quite some time there were aircraft that kept fixed landing gear, although they incorporated fairings that reduced their aerodynamic resistance (in fact, it is still common to see these in some small aircraft models). The reason was very simple: the weight of a fairing was much less than that of a complete system for retracting landing gear.

As metal (aluminium) gained prominence as a material for the manufacture of aircraft, their performance gradually improved; however, it also meant a gradual increase in the weight of the aircraft. This made it necessary to create more robust and complex landing gear that would provide greater efficiency in absorbing the greater impact against the ground generated by a heavier craft with faster landing speeds.

At this point the brakes also had to evolve, as they had to cope with greater speeds on the runway, as well as with the aircraft’s greater mass. In the first aircraft with fixed landing gear, the use of brake shoes, very similar to those used for bicycles, was common. Drum brakes were the next development. But the most significant change came in 1978, when Bosch introduced a new electronic braking system, initially designed and developed for aircraft, which it called ABS (AntiBlockierSystem). Bosch had obtained a patent for this system in 1936, but the inability to manage the complex calculations that ensured efficiency in braking prevented its development until the advent of digital electronics.

The braking system is always installed in the main landing gear and is not incorporated into the aircraft’s directional wheels.

Lastly, the steering capability of landing gears was another variable that added complexity to their development. Initially, aircraft could not be manoeuvred on the ground and were usually positioned manually. In the 1920s, a directional wheel was introduced into some aircraft (initially it was placed at the rear as part of an inverted tricycle configuration). And so it remains to this day.

Landing gear is not only based on the use of wheels, but rather throughout the history of aviation it has been adapted to the various mediums in which aircraft are operated. Thus, floats are characteristic elements of seaplanes, skis are incorporated when operations are performed on snow, caterpillar tracks are used for soft terrain, and air cushions are used to operate on soft and mixed surfaces.

Landing gear is an element that often goes unnoticed or is considered a simple system; however, nothing could be further from the truth.

 

 

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26/11/2018

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