INFORMATION LETTER #2005-2
Use of Cherry Max Rivets to Install T/R Tip Caps
This information Letter pertains to the Sikorsky S-58/H-34 p/n S1615-30101 t/r blade & S-61/H-3 p/n S6117-30101 & 61170-30201 t/r blade tip caps.
Every year we receive a couple of S-58 or S-61 tail rotor blades that have had the tip cap repaired or replaced using Cherry Max rivets. These rivets are not the proper rivets called out in the parts manual or SRM for use to secure a tip cap. It's not that they don't work, it's that they are meant to be a permanent installation and the tip cap is not a permanent installation.
The Cherry Max rivet uses a monel stem in an aluminum sleeve. The problem is in the removal of the rivet. In order to drill the rivet out you must grind the stem and lock collar away to be able to drill the rivet. If damage to the tip cap is not done during the grinding, then the rivet usually spins during the drilling thereby enlarging the hole.
The proper rivet is an all aluminum rivet, sleeve, stem and lock collar. Current part number is NAS1921B04- (which superceded the 100V4 series). The NAS 1921 rivets are generally easier to remove with less damage to the tip cap or blade.
This letter is intended to bring a potential problem to the attention of the owner/operator, thereby reducing your costs.
Please call ABS at 407-846-6780 if you should have any questions or concerns.
Leonard Peterson, President
David Stutesman, Vice-President