Level Use I Short-term preservation of flyable and nonflyable aircraft for periods up to 60 days Preservation of aircraft for shipment and for II periods of 60 days to 1 year Preservation for long-term aircraft storage III for periods of 1 to 8 years NOTE: Level I preservation will have special MRCs for each aircraft/engine. As a maintenance crew member, you will be involved with level I preservation. Anytime an aircraft is out of service or will remain idle for 14 or more days, maintenance will put the aircraft in level I preservation. You will use special MRCs to preserve, maintain preservation, and depreserve an aircraft. Protection against corrosive attack on aircraft is achieved by placing a barrier between the surface and any possible source of moisture. During overhaul or manufacture, protective barriers, such as electroplate, paint, or chemical surface treatment, are provided. Surfaces that cannot be so treated (in some instances, the treated surfaces themselves) are covered with special corrosion-preventive compounds. These compounds are effective only if no moisture, dirt, or active corrosion is present on the treated surface. Therefore, you must thoroughly clean and dry the aircraft before applying a preservative compound. Also, you must apply an unbroken film of preservative in as moisture-free an atmosphere as possible. Complete protection is not provided by compounds alone. Tapes, barrier paper, and sealing devices are used to seal off the many openings on aircraft. If these openings were to remain open during long-term storage, moisture and dirt would enter and accumulate. To provide additional protection against corrosion, a complete moisture barrier is sometimes used on aircraft. Unless the cavity is protected by a vapor corrosion inhibitor, use desiccants to dehydrate internal areas that have been sealed. When an area cannot be sealed adequately, provide ventilation and moisture drainage. When installed equipment in an aircraft is not being regularly used, its components must be preserved. For example, the guns of an aircraft must be cleaned after each firing. The type of oil or other protective treatment used depends upon the anticipated period of idleness for the guns. In the maintenance of aircraft surfaces under operating conditions, preservation adds to the protection already present. Also, protection coating and barrier materials provide temporary protection to damaged areas. A brief description of some of the more common materials used in aircraft preservation that are readily available in Navy stock is given in the following text. Corrosion-Preventive Compound, Solvent Cutback Corrosion-preventive compound, solvent cutback, comes in grades for specific applications. There are five grades of this compound, three of which are commonly used and do not displace water, grades 1, 2, and 4. All grades can be removed with dry-cleaning solvent. These materials are designed for cold application. 4-16 Grade 1 preservative forms a dark, hard-film, opaque cover. Its general use is limited because of the difficulty in removing aged coatings. Also, it hides what corrosion is present when it is applied over corroded areas. This material is used where maximum protection against salt spray is required. The military specification is MIL-C-16173, grade 1. Grade 2 is a thick soft, greaselike compound which is used primarily to protect metal surfaces against corrosion during rework or storage periods. The military specification is MIL-C-16173, grade 2. Grade 4 preservative forms a thin, semitransparent film through which identification dates can be read. It sets up dry enough to the touch, so preserved parts may be handled easily. This grade is effective in protecting wheel well areas and other exposed surfaces where film transparency is required and moderate protective characteristics can be tolerated. Its main disadvantage is that it is easily removed by water spray and requires replacement at l-month intervals under severe exposure conditions. The military specification is MIL-C-16173, grade 4. Coating Compounds Activities based outside the Continental United States sometimes receive aircraft via ocean surface shipment. This is especially true of helicopter and limited-range fighter aircraft. These aircraft are