assigned Navy enlisted classification (NEC) 7225/military occupational specialty (MOS) 6044. Organizational Maintenance Activities O-levels responsibilities areas follows: 1. Request NDI I-level support as required. 2. Obtain IMA NDI services in all situations where NDI results are suspicious. 3. Have an NDI technician verify defects discovered by an NDI operator, whenever possible. 4. Inform the IMA, in advance, of scheduled NDI requirements. Include these requirements in the monthly maintenance plan. 5. O-level NDI technicians maybe assigned to the supporting IMA, as necessary, to maintain their proficiency and to augment IMAs NDI capabilities. NDI INSPECTION METHODS The various NDI methods serve as tools of prevention that allow defects to be detected before they develop into serious or hazardous failures. With the NDI methods, a trained and experienced technician can detect flaws or defects with a high degree of accuracy and reliability. It is important that you become fully knowledgeable of the capabilities of each method. It is equally important that you recognize the limitations of the methods. Some of the defects found by NDI include corrosion, leaks, pitting, heat/stress cracks, and discontinuity of metals. The following paragraphs will give a brief synopsis of the various NDI inspections. For further information on NDI procedures, you should consult the Nondestructive Inspections Manual, NA-01-1A-16, or the appropriate inspection manual pertaining to the type of aircraft or part that is to be inspected by an NDI method. Magnetic Particle Inspection Magnetic particle inspection is a rapid, non- destructive means of detecting discontinuities in parts made of magnetic materials. If the part is made from an alloy that contains a high percentage of iron and can be magnetized, it is in a class of metals called “ferro- magnetic,” and it can be inspected by this method. If the part is made of material that is nonmagnetic, it cannot be inspected by this method. The magnetic particle inspection method will detect surface discontinuities, including those that are too fine to be seen with the naked eye, those that lie slightly below the surface, and, when special equipment is used, the more deeply seated discontinuities. The inspection process consists of inducing a magnetic field into a part and applying magnetic particles, in liquid suspension or dry powder, to the surface being inspected. When the magnetic field is interrupted by a discontinuity, some of the field is forced out into the air above the discontinuity, forming a leakage field. The leakage field will be stronger and more concentrated the closer the discontinuity is to the surface. The presence of a discontinuity is detected by the ferromagnetic particles applied over the surface. Some of these particles will be gathered and held by the leakage field. This magnetically held collection of particles forms an outline of the discontinuity and indicates its location, size, and shape. Electric current is used to create or induce magnetic fields in magnetic materials. The magnetic lines of force are always aligned at right angles (90°) to the direction of the current flow. The direction of the magnetic field can be altered, and it is controlled by the direction of the magnetizing current. The arrangement of the current paths is used to induce the magnetic lines of force so that they intercept and are as near as possible at right angles to the discontinuity. The magnetic field must be in a favorable direction to produce indications. When the flux lines are oriented in a direction parallel to a discontinuity, the indication will be weak or lacking. The best results are obtained when the flux lines are in a direction at right angles to the discontinuity. If a discontinuity is to produce a leakage field and a readable magnetic particle indication, the discontinuity must intercept the flux lines of force at some angle. When an electrical magnetizing current is used, the best indications are produced when the path of the magnetizing current is flowing parallel to the discontinuity, because the magnetic flux lines are always at an angle of 90° to the flow of the magnetizing current. The two types of magnetizing methods used are circular and longitudinal. CIRCULAR  MAGNETIZATION.—Circular magnetization is used for the detection of radial discontinuities around edges of holes or openings in parts. It is also used for the detection of longitudinal discontinuities, which lie in the same direction as the current flow either in a part or in a part that a central conductor passes through. Circular magnetization derives its name from the fact that a circular magnetic field always surrounds a conductor, such as a wire or a bar carrying an electric current (fig. 15-3). The direction of the magnetic lines of force (magnetic field) is always at right angles to the 15-6