Procedures and Precautions The stripping procedures described below are general in nature. When stripping any aircraft surface, you should consult the applicable MIM for the specific procedures to be used. Stripping should be accomplished outside whenever possible. If you must strip aircraft surfaces in a hangar or other enclosure, you should make sure you have adequate ventilation. You should adhere to the following general procedures and precautions during stripping operations: CAUTION Before cleaning and stripping, make sure that the aircraft is properly grounded. This will dissipate any static electricity produced by the cleaning and stripping operations. Where the paint remover may contact adhesives, mask all seals, joints, skin laps, and bonded joints by using the approved tapes and papers. Apply the stripper liberally. Completely cover the surface with a thick layer of stripper with a paint or acid brush. The stripper should not be spread in a thin coat like paint because it will not loosen paint sufficiently for removal, and the remover may dry on the surface of the metal. This would require it to be reapplied. Allow the stripper to remain on the surface long enough for it to wrinkle and lift the paint. This may be from 10 to 40 minutes, depending upon temperature, humidity, and the condition of the paint coat being removed. Reapply paint remover as necessary in the areas where paint remains tight or where the material has dried. Remove loosened paint and residual paint remover by washing and scrubbing the surface with fresh water, fiber scrapers, bristle brushes, and rags. If water spray is available, you should use a low-to-medium pressure stream of water. Apply it directly to the surface while scrubbing the surface. After a thorough cleaning, you should remove masking materials and clean any residual paint from the surface. Rinse with water and clean the area with aircraft cleaning compound (1 part MIL-C-85570 to 9 parts water) to remove paint remover residue. Flap Brush Paint can be mechanically removed with a flap brush. The brush consists of many nonwoven, nonmetallic, nylon flaps bonded to a fiber core. The brush assembly (fig. 4-31) is made up of a flap brush, flanges, and mandrel. Use a NO LOAD 3200 rpm pneumatic drill motor to power the brush. Do not use a flap brush that is worn down to within 2 inches from the center of the hub. Continued use beyond this limit may cause gouging due to loss of flexibility of the fiber. When you use a flap brush, apply minimum pressure to remove the most paint and the least metal. Excessive pressure will cause some paints to melt, gum up, and streak around the area being worked. For safe and efficient operation, the direction of rotation is indicated by an arrow imprinted on the inside of the core. Wear eye protection when operating a flap brush, and consult your maintenance instruction manuals for limitations on corrosion removal. Q77.  What is the primary purpose of any paint finish? Q78.  When using paint removers, you should wear what type of protective clothing? Q79. What safety precaution must be taken before cleaning and stripping old finishes on aircraft? Q80.  What type of motor should you use to power a flap brush? Figure 4-31.—Flap brush and mandrel. 4-47