Figure 8-10.  Hoist and frame assembly used for engine removal.  Hoisting and Mounting the Engine for  Installation Hoisting the Engine Before the hoist is hooked onto the engine sling, recheck the  aircraft tail supports and the wheel chocks. Fasten lines to the  engine, at points on the sides or rear, so that the engine can  be controlled as it is being hoisted. Hook the hoist onto the  sling and hoist the engine just enough to relieve the engine  weight from the mount attachments. Remove the nuts from  the mount attachments in the order recommended in the  manufacturer’s instructions for the aircraft. As the last nuts  are being removed, pull back on the lines fastened to the  engine (or force it back by other means if lines are not being  used), thus steadying the engine. If bolts must be removed  from the mount attachments, be sure the engine is under  control before doing so. If the bolts are to remain in the mount  attachments, the hoist can be gently maneuvered upward or  downward as necessary after all the nuts have been removed.  Meanwhile, gently relax the backward force on the engine  just enough to allow the engine gradual forward movement  when it is free from the mount attachments. When the hoist  has removed all engine weight from the mount attachments,  the engine should be eased gently forward, away from the  aircraft. If the engine binds at any point, maneuver it with  the hoist until it slips free. The procedure just discussed applies to removal of most  reciprocating and turbine aircraft engines. Any variation  in details is outlined in the manufacturer’s instructions.  Before attempting any engine removal, always consult these  instructions for the aircraft concerned. When the engine has  been removed, it can be carefully lowered onto a stand. The  engine should be fastened to the stand and prepared for the  removal of accessories. When the new or overhauled engine is ready to be hoisted  for installation, move the engine stand as close as possible  to the nacelle in which the replacement is to be installed.  Then, attach the sling to the engine and hook the hoist to the  sling. Take up the slack until the hoist is supporting most of  the engine weight. Next, remove the engine attaching bolts  from the stand and hoist the engine clear. The engine stand may be moved and the hoist frame  positioned so the engine can be hoisted easily into the nacelle.  To prevent injury to the crew or damage to the aircraft or  engine, be sure that the engine is steadied when moving the  hoist frame. Engine nacelles are rarely designed for the engine to be  fitted and bolted into place as though it were being mounted  on a bare wall. The engine must be guided into position and  mated with its various connections, such as the mounting  bolt holes and the exhaust tailpipe. This must be done despite  such obstacles as the nacelle framework, ducts, or firewall  connections and without leaving a trail of broken and bent  parts, scratched paint, or crushed fingers. When the engine has been aligned correctly in the nacelle,  insert the mounting bolts into their holes and start all  of the nuts on them. Always use the type of bolt and  nut recommended by the manufacturer. Never use an  unauthorized substitution of a different type or specification  of nut and bolt than that prescribed. The nuts on the engine mount bolts must be tightened to the  torque recommended by the aircraft manufacturer. While the  nuts are being tightened, the hoist should support the engine  weight sufficiently to allow alignment of the mounting bolts.  If the engine is permitted to exert upward or downward  pressure on the bolts, it is necessary for the nuts to pull the  engine into proper alignment. This results in nuts being  tightened to the proper torque value without actually holding  the engine securely to the aircraft. The applicable manufacturer’s instructions outline the  sequence for tightening the mounting bolts to ensure security  of fastening. After the nuts are safetied and the engine sling  and hoist are removed, bonding strips should be connected  across each engine mount to provide an electrical path from  the mount to the airframe. 8-10