Central Aerohydrodynamic Institute
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Flight safety: a new step towards problem solving

For the first time in Russia, the scientists of the Central AeroHydrodynamic Institute named after professor N.E. Zhukovsky, TsAGI, (together with colleagues from the Institute of General and Inorganic Chemistry named after N.S. Kurnakov of the Russian Academy of Sciences) are carrying out projects to create and study a shock-sensitive detector polymer coating for aircraft structures. Why it is so unique and how it can provide increase in flight safety and reduce the maintenance time for aircraft — these are the questions we discussed with Svetlana Smotrova, the Head of the Research Laboratory of the Structural Testing and Monitoring Promising Methods.

Svetlana Aleksandrovna, how long have the scientists of TsAGI and the Institute of General and Inorganic Chemistry been working on the problem of creating a unique indicator coating?

We have been working on this problem for almost four years. The achievements of the specialists from both Institutes are one more important step in solving the current problem of ensuring the flight safety of civil aircraft. We hope that the new coating, along with other means, will allow us to carry out an in-operation visual inspection of the aircraft’s technical condition without using special complicated equipment. The detector coating will allow us to obtain easily and conveniently reliable data on the technical condition of the structure and is able to facilitate support of the airframe’s airworthiness.

We would like to know, how dangerous are the barely-visible damages on airframes made of a polymer composite material?

It is known that ensuring the aircraft’s flight safety and the aircraft’s protection against aviation accidents is an important national task. The accidental shock-type damages, such as scratches, cleavages, dents, the depth of which is between 0.5 and 1 millimeter, can occur at any stage of aircraft operation, including the stages of transportation, airport parking, scheduled maintenance, and those caused by human errors. Collisions with birds, hail, stones, concrete pieces flying out from under the landing gear wheels during take-off and landing also lead to damages and the occurence of various faults that may affect structural strength and integrity.

If metallic materials are used, the problem of small accidental operational mechanical damages is of no interest from a practical point of view. However, for an aircraft made of composite materials, such phenomena can be a serious danger. Unlike metals, which absorb the shock energy through plastic deformation, almost retaining its strength, polymer composite materials may demonstrate brittle fracture of a matrix and fibers at the moment of impact with relatively low energy level. Therefore, the most common operational problems of composite airframe are the barely-visible shock damages in the form of dents, cleavages, which are accompanied by delamination and cracking of the inner layers, which can not be seen on the exterior side. In these areas, there is a significant reduction or disappearance of the bonds between adjacent polymer-composite layers, which leads to a significant deterioration of the strength and operational characteristics of the airframe elements.

When will this coating be introduced into the operational process?

At present, this coating is being tested on structurally similar samples made of carbon fiber covered with a standard paint coating. By the end of this year, the scientists will have tested the technological parameters of its application. As part of the experiment, they will assess the detection properties of a shock-sensitive polymer coating allowing them to detect the barely-visible damages with a depth of 0.5 to 1 millimeter on carbon fiber. It is also necessary to evaluate the impact of environmental factors, primarily the solar ultraviolet radiation. The scientific research works are to be completed next year after the developed coating passes full-scale aircraft unit tests in the laboratory. Then it will a long way to full-scale implementation of this development.

Flight safety in our country is one of the national priorities. The specialists are constantly striving to minimize the number of aviation accidents, and at the same time to reduce the life cycle cost of aircraft. In May 2008, in accordance with the Convention on International Civil Aviation, the State program on ensuring flight safety of civil aircraft was developed and adopted in Russia. The main purpose of the document is the problem solving and introduction of the system, which will provide steady reduction in the number of aviation accidents and human losses with a simultaneous increase in the rate of aviation industry modernization in all its areas.

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