Posted for John Spry <spry@paradise.net.nz>:

 I've done 30 odd hours in my recently completed 320 (small tail) and notice
grey streaks (aluminium I think) coming from the outboard elevator hinges .
 Everything seems tight - has anyone got any ideas what may be causing it and
the best fix.
 
 Thanks

[It's strange to hear it reported in a plane with only 30 hours on it, but it's a well-documented phenomenon.  The grey streaks are most likely aluminum, as you surmised, resulting from the wear the hinge knuckles are seeing from rotating around the hinge pins.  The most typical fix is to ream the knuckles and go to the teflon tube hinge pin sleeves.  Search the archive for "airframe vibration".  One of our members sells the teflon and hinge pin kits... I'm sure he'll jump in.   <marv>     ]