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 Aviation Blade Services receives several 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 for in the parts manual or SRM for use to secure a tip cap. While these rivets work they are intended 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 the stem must be ground and lock collar away to be able to drill the rivet. If the tip cap is not damaged 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. The current part number is NAS1921B04- (which superseded the 100V4 series). The NAS 1921 rivets are generally easier to remove with less damage to the tip cap or blade.
For more information contact Paul Bolton at (407) 846-6780.
This notice is for information purposes only and does not condemn any blade without a more detailed inspection of the blades.