{HEAD ~ Friction} is generated during {TAIL ~ operation} of the engine between the outer surface of the friction damper and the undersides of two adjacent shrouds 
{ HEAD ~ Friction } is generated during { TAIL ~ operation } of the engine between the outer surface of the friction damper and the undersides of two adjacent shrouds
HEAD HEAD HEAD HEAD HEAD REL REL REL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH