07-07-2026, 11:47 AM
Yesterday Jeff R. brought his severely rusted main rotor shaft assembly to my workshop for shaft replacement. He had taken it to at least one machine shop to have them remove the main shaft but they were unwilling to work on anything relating to aircraft. On this particular shaft assembled in South Africa the main thrust bearing was locktited onto the shaft so we had to heat it up with a torch then beat it off, the thrust bearing will be replaced with a new one. The slider ball internal bore was securely rusted onto the main shaft and after much penetrant oil and physical force with no movement, I cut the main shaft off just above the slider ball and was able to press the shaft out of the slider ball with my hydraulic press. We then installed the swashplate assembly onto his new main shaft after cleaning up all of the components and applying generous amounts of grease to all surfaces.
If your helicopter has sat for several years without periodic greasing, it is imperative to inspect it for rust pitting especially in the area above the thrust bearing where the entire cantalevered portion is exposed to the most lateral stresses in flight. The first place to look is under the rubber boot because that boot traps moisture that begins to eat away at the shaft surface. Surface rust in that area can be cleaned up with emery cloth as long as there is no pitting that cannot be sanded off. If the shaft is pitted to the point where sanding will not remove the pits, the shaft is not airworthy and must be replaced. Don't let this happen to your main shaft.
I suggest that the boot be lifted and the shaft greased with generous amounts of lubricant every 25 hours or if the helicopter is sitting, every year at least.
If your helicopter has sat for several years without periodic greasing, it is imperative to inspect it for rust pitting especially in the area above the thrust bearing where the entire cantalevered portion is exposed to the most lateral stresses in flight. The first place to look is under the rubber boot because that boot traps moisture that begins to eat away at the shaft surface. Surface rust in that area can be cleaned up with emery cloth as long as there is no pitting that cannot be sanded off. If the shaft is pitted to the point where sanding will not remove the pits, the shaft is not airworthy and must be replaced. Don't let this happen to your main shaft.
I suggest that the boot be lifted and the shaft greased with generous amounts of lubricant every 25 hours or if the helicopter is sitting, every year at least.