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As Portuguese EDP Renovaveis he jumped 45On the contrary the markets should be enhancedHowever the text did not far from it resolved all the issuesSITA France says look at the single folderA company of about 100 employees managing 2This principle also applies in the public serviceFind the articles of the series of summer onIt receives more than 150 records per yearA shorter maturity by end 2006 not panicThe objective of the President André Amiel is 4 millionIf the causes of the crash of the Airbus of Air France are not yet known with precision, it is likely that they will have been multiple. A disaster is often the result of an accumulation of events or a series of dysfunctions. Contrary to a widespread idea, technical failure explains only 5 to 10 of cases, while three-quarters of the accidents are due to human error, and 66 of them are linked to external, often atmospheric causes.
1. The atmospheric environment
If lightning is the most spectacular phenomenon, is however not the most feared pilots. The electric current, even of a very high intensity, iterates through the surface of the apparatus from the nose to tail, without penetrating inside (phenomenon of the Faraday cage). However, the arrival of composite materials change the deal. "The composite is not conductive, electric charges do not drain." "There would therefore be breakdown, as in the air, and risk of perforation of the composite, lightning then entering the aircraft", explains Michel de Nzikou, Scientific Director-General of the Onera (national Office of studies and space research). The future Boeing 787 and Airbus 350 will be made at 50 of composite materials, including the fuselage that builders had to "plate" to make it conductive.
Several solutions are employed, such as that of insert a dense wire mesh in the folds of the material. With an unfortunate result, to increase the weight of the aircraft, then the composite aims precisely to alleviate it. Another phenomenon, icing, is much more formidable. Under certain conditions of crystals of ice several centimetres, formed on the edge of the wings, and alter the aerodynamic profile of the aircraft up to make him lose its lift. Onera (in collaboration with Nasa) models in three dimensions the formation of ice crystals, and seeks to better understand this phenomenon of supercooling of water. In the air, particularly at high altitude on the crossing of cumulonimbus, water remains in the liquid state even by 40 degrees, but solidifies on contact with a solid surface. Thermal defrosting systems can then be operated by drivers. Electrical resistance, or from hot air engines warm interior of the wing. A mechanical trail is explored by Onera, with a device of small shocks which break the ice in training.
Turbulence in the cumulonimbus are caused by the crossing of very powerful updrafts (30 metres per second), and downdrafts. Therefore, an effect of shear subjecting the structure of the unit to strong constraints. The aircraft are designed to withstand up to a certain limit: "A the end, the wing of a widebody in flight can move vertically several metres," notes Michel de Nzikou. The best is still to avoid these dangerous areas by detecting turbulence in advance. Systems exist, but can be advanced Lidar technology which, in contrast to the conventional radar, uses light and not waves radio. "retro suspended particles - diffuse light, to measure their speed, so that the flow of air." Only problem, there are very few particles at high altitudes and to observe these so-called turbulence in clear skies, must be of very high energy LiDAR. "Onera is today to detect a minute in advance, time needed for passengers to fasten their seat belts," said the Scientific Director. The problem of the turmoil created by the wake of the aircraft is now well known (see photo of simulation by Onera). A small plane taking off or landing behind a widebody is thus subject to very severe turbulence. This is the reason for which the drivers must meet safety distances the size of the aircraft.
The impact of the bird is also the subject of many studies because the volatile cause many accidents, including, to the landing and take-off.
(2) Technical failures
The aluminum used for the construction of the aircraft contains naturally microfissures, with fatigue, can transform into cracks and fractures. Today, the device is inspected with ultrasound. In the future, should be able to ask sensors, receivers transmitters, particularly in the most difficult locations, to monitor permanently. A kind of "integrated health control". The concerns are of another kind with composites manufactured by superposition of basic folds, consisting of fibers and resin. The risk then is that layers to take off. As in some concrete structures, could place optical fibres that would inform on the evolution of the structure. Difficult to implement, accurate however Nzikou Michel: "Because by placing a fibreglass in carbon fibre, it introduced a singularity that weakens the strength of the material." It is the same problem for the "autoréparants" materials which, thanks to small particles containing the polymerizable resin to contact air, clog microcracks which pass through. The introduction of these microparticles in material weakens his strength.
More and more computerized, aircraft are also subject to the vagaries of the software, it is more difficult to prove reliability due to their number. New programming techniques, "formal methods", should ensure, by design, the absence of a bug in the lines of code. Some software blocks are even designed automatically.
3. The human factor
More quick to manage the unexpected that the machine man is however sensitive to fatigue, and especially the stress. "The brain reacts differently when the individual is stressed, even if it is for a trained professional", stresses Michel de Nzikou. In the future, some countermeasures devices could help the driver avoid bad reflexes. For example, many accidents are due to misinterpretations of the information provided on board. By analyzing real-time actions of the crew, the automation to indicate errors. A simulation of what risk happened could even to be made: for example, a landing outside the runway continue at that speed and with this angle of descent. Researchers imagine even that automatism may take the hand a short time. It is the difficulty of the dialogue of the human with the machine. "One of the major difficulties in the case of the diabolical error, i.e. when the pilot has a false picture of the situation and it is, is to submit information which so respond", stresses Michel de Nzikou. Result: now, even basic research like Onera organizations use ergonomists. The understanding between man and all the machines surrounding is probably one of the most serious work tracks.
