The order of filter washing.

To increase the removal efficiency of resinous connections during FE clearing the solvent 646 (GOST 18 188 – 72) or solvents 645, 647 and 648 are being applied, but the solvent 646 is the most effective.

Solvent washing:

- FE apertures are closed by the caps preventing the pollutions in its internal cavity;

- FEs are washed in a tray with gasoline Б-70;

- FE caps and rubber consolidations are removed, in order to avoid their destruction in the environment of the solvent and are being dried for 15…20 minutes in the open air or blown with compressed air;

- One cap (made of fluorine plastic or other firm material to the solvent) is installed upon FE and is immersed into a bath with a solvent vertical end open upwards, filled up with a solvetn to the top FE flange, not letting solvent hit through the top sawn-off FE surface into its internal cavity;

- FE is held in solvent not less than for 1.5 h, 645 – not less than 3h, 647 – not less than 2.5 h, 648 – not less 2h.;

- Every 30 minutes FE is pulled out from solvent and, without overturning the solvent is allowed to flow down completely.

One portion of solvent is allowed to be used before its color changes (from colorless till light brown). After FE has been kept during the established time in solvent its to be taken out and dried in air during 15…20 min. and washed out on ultrasonic installation. Then the quality of washing is to be checked up.

The suitable and preserved FE is being stacked together with the control coupon, preventing their direct contact into a vinyl (P.V.C.) package and solder tightly.

Filters refinement quality is checked visually on a gleam through the filtering grid – all the apertures of a frame’s grid should be accurately visible; selectively (some filtering sections from out of the complete set) by means of three-dimensional microscope МБС-2 (during survey at zoom 16…32 times pollutions shouldn’t be observed in grid cells); by means of the device of filter control (ПКФ) on time of the filter elements internal volume fill up during its immerse in АМГ-10 oil.

66. What are the main causes of corrosion damage of structural elements of an AC?

Principal element design corrosion defeat causes are the following:

- Atmospheric factors influence, a moisture at the underground part of a fuselage and FLM;

- Both paint, varnish and metal protective covers infringement;

- Usage of metal, paint varnish aggressive liquids and solvents of different application(either washing, anti-icing, etc.) during aircraft maintenance;

- Details and knots design features (sharp edges presence, where the paint and varnish films are easily get spoiled, insufficient hermetic sealing, for example toilet rooms floor, buffets, kitchens elements etc.);

- Metal contact with various electrical;

- Protective coverings poor care quality during service.

67. How to protect the outer surface of aircraft?

External surfaces of the plated covering made of aluminum alloys are protected by oxide film, and also with oxide film that is covered with a colorless varnish, prime coating and enamel. Magnesium alloys details, differ with the most with their lowered corrosion firmness, in all cases protected by a prime coating and paint with green enamel which is put on preliminary oxidized surface.

Steel details in dependence with their appointment are protected by metallic (zinc, cadmium, chrome, nickel) or with paint and varnish covering upon preliminary phosphates or abrasive surfaces.

Aluminum alloys corrosion sign – white and gray stains occurrence upon the surface of details or the separate, hardly appreciable ulcers isolated from each other, sometimes having an appearance of black dots on a covering. Magnesium alloys corrosion is found out upon paint and varnish coverings swelling and damp salt film of white-dirty color occurrence. Steel corrosion is accompanied by formation of brownish-red rust film on a surface of details.

68. How to remove corrosion from the external surfaces of aircraft?

Corrosion removal starts upon its character definition. It is necessary to distinguish the centers of superficial corrosion with a crater depth up to 0.2 mm and zones of plural corrosion centers in which the depth already exceeds 0.2 mm. If the corrosion has formed in a zone of hit of a chemical liquid or electrolyte than these places should be carefully washed out with baking soda solution, then using warm water and wiped dry. The corrosion zone should be smoothed out by grinding paper (№ 180 - 220), and then the restoration of paint-varnish coverings takes place.

Corrosion on details that are made of magnesium alloys (rocking chairs, cantilevers, fittings) is characterized by ЛКП swelling and salt film of white-dirty color occurrence. Superficial corrosion is removed by grinding paper № 220.

Corrosion bowls are removed by scraper.

Date: 2015-12-17; view: 673