Position to check for separation Expansion gap (not to be confused with joint separation) Bulkhead ply web Bulkhead frame member Fuselage inner and outer ply skins Wood screw Screw hole Reinforced laminated fuselage member Corrosion indicating failure of bulkhead  glued joint to fuselage side Figure 6-7.  Checking a glued joint for water penetration. manufacturer, replace removed screws with new screws of  identical length, but one gauge larger in diameter.  a stress riser exists at the ends of the plate. A failure of the  primary structure can be expected at this point.  [Figure 6-8]  As part of the inspection, examine the structure for other  defects of a mechanical nature, including any location where  bolts secure fittings that take load-carrying members, or  where the bolts are subject to landing or shear loads. Remove  the bolts and examine the holes for elongation or surface  crushing of the wood fibers. It is important to ensure the bolts  are a good fit in the holes. Check for evidence of bruises or  crushing of the structural member, which can be caused by  overtorquing of the bolts. Inspection experience with a particular type of aircraft  provides insight to the specific areas most prone to water  penetration and moisture entrapment. Wooden aircraft are  more prone to the damaging effects of water, especially  without the protection of covered storage. Control system  openings, fastener holes, cracks or breaks in the finish, and  the interfaces of metal fittings and the wood structure are  points that require additional attention during an inspection.  Additionally, windshield and window frames, the area  under the bottom of entrance and cargo doors, and the lower  sections of the wing and fuselage are locations that require  detailed inspections for water damage and corrosion on  all aircraft.  The condition of the fabric covering on plywood surfaces  provides an indication of the condition of the wood  underneath. If there is any evidence of poor adhesion, cracks  in the fabric, or swelling of the wood, remove the fabric to  allow further inspection. The exposed surface shows water  penetration by the existence of dark gray streaks along the  grain and dark discoloration at ply joints or screw holes.  Cracks in wood spars are often hidden under metal fittings  or metal rib flanges and leading edge skins. Any time a  reinforcement plate exists that is not feathered out on its ends,  Figure 6-8.  Areas likely to incur structural damage. 6-6 Rib attach nail holes Decay Crack Plywood plates Strut attach point Elongated bolt hole Compression failure