Figure 13-138.  Deflate a tire before removing or probing any area  where a foreign object is lodged.  Figure 13-137.  Marking of damaged area to enable closer  inspection. Figure 13-139.  Remove an aircraft tire from service when the depth of a cut exposes the casing outer plies of a bias ply tire or the outer  belt layer of a radial tire (A); a tread rib has been severed across the entire width (B); or, when undercutting occurs at the base of any  cut (C). These conditions may lead to a peeled rib. 13-83 must be removed. Landing with a brake applied can often  cause a severe flat spot that exposes the tire under tread. It  can also cause a blowout. The tire must be replaced in either  case.  [Figure 13-140] A bulge or separation of the tread from the tire carcass is  cause for immediate removal and replacement of the tire.  the tire.  [Figure 13-139]  Consult the aircraft maintenance  manual, airline operations manual, or other technical  documents applicable to the aircraft tire in question. A flat spot on a tire is the result of the tire skidding on the  runway surface while not rotating. This typically occurs  when the brakes lock on while the aircraft is moving. If the  flat spot damage does not expose the reinforcing ply of a  bias tire or the protector ply of a radial tire, it may remain in  service. However, if the flat spot causes vibration, the tire  Protector ply Bolt plies Tread reinforcing plies Casing outer ply Casing outer ply C A B C A B Radial Tire Bias Ply Tire Peeled Rib