content_image/602785.jpg
<img src='content_image/602785.jpg'>

2. Dispose of all safety devices (safety wire, cotter pins, etc.) as they are removed. Never use them a second time. Always replace with new safety devices. 

3. All loose studs, and loose or damaged fittings, should be carefully tagged to prevent being overlooked during inspection. 

4. Always use the proper tool for the job. Use sockets and box end wrenches wherever possible. If special tools are required, use them rather than improvising. 

## Inspection Process 

The inspection of engine parts during overhaul is divided into three categories: 

1. Visual 

2. Structural NDT 

3. Dimensional 

Many defects on the engine components can be detected visually, and a determination of airworthiness can be made at this time. If, by visual inspection, the component is determined to be unairworthy, the part is rejected, and no further inspection or repair is required. Structural failures can be determined by several different methods. Magnetic parts can readily be examined by the magnetic particle method. Other methods, such as dye penetrate, eddy current, ultra sound, and X-ray, can also be used. The first two methods are aimed at determining structural failures in the parts, while the last method deals with the size and shape of each part. By using very accurate measuring equipment, each engine component can be dimensionally evaluated and 

compared to service limits and standards (tolerances) set by the manufacturer. 

## Visual Inspection 

Visual inspection should precede all other inspection procedures. Parts should not be cleaned before a preliminary visual inspection, since indications of a failure may often be detected from the residual deposits of metallic particles in some recesses in the engine. 

Several terms are used to describe defects detected in engine parts during inspection. Some of the more common terms and definitions are: 

1. Abrasion—an area of roughened scratches or marks usually caused by foreign matter between moving parts or surfaces. 

2. Brinelling—one or more indentations on bearing races, usually caused by high static loads or application of force during installation or removal. Indentations are rounded or spherical due to the impression left by the contacting balls or rollers of the bearing. 

3. Burning—surface damage due to excessive heat. It is usually caused by improper fit, defective lubrication, or over-temperature operation. 

4. Burnishing—polishing of one surface by sliding contact with a smooth, harder surface. Usually no displacement nor removal of metal. 

5. Burr—a sharp or roughened projection of metal usually resulting from machine processing. 

6. Chafing—a condition caused by a rubbing action between two parts under light pressure that results in wear. 

7. Chipping—breaking away of pieces of material, that is usually caused by excessive stress concentration or careless handling. 

8. Corrosion—loss of metal by a chemical or electrochemical action. The corrosion products are easily removed by mechanical means. Iron rust is an example of corrosion. 

9. Crack—a partial separation of material usually caused by vibration, overloading, internal stresses, defective assembly, or fatigue. Depth may be a few thousandths, to the full thickness of the piece. 

10. Cut—loss of metal, usually to an appreciable depth over a relatively long and narrow area, by mechanical means, as would occur with the use of a saw blade, chisel, or sharp-edged stone striking a glancing blow. 

11. Dent—a small, rounded depression in a surface usually caused by the part being struck with a rounded object. 

