Spindle Radiuses – February 4, 2010
A question has been raised that may be disturbing to owners of SAFARI helicopters. We present the information that follows to assist you in determining if you should be concerned.
It concerns the presence of a radius at the machined edges of the main rotor spindle and of the tail rotor spindle. There have been 2 accidents involving failure of these parts. We have posted information concerning these accidents on the website. In both events, the helicopters had been involved in previous accidents.
In one, the tail rotor spindle had been removed in the repair of a tail boom strike. The spindle and delta pin had been reinstalled incorrectly, and produced a violent vibration. At the insistence of the owner, a second set of tail rotor blades was provided by the factory. After dismantling the tail rotor assembly to install the new blades, the spindle was installed correctly. The vibration disappeared, but the spindle failed in flight shortly after. The incorrect installation was confirmed by an independent party with knowledge of the helicopter.
All tail rotor spindles are now clearly marked for correct installation.
In the second event, the main rotor spindle failed in flight. A number of factors contributed to this event. This helicopter was constructed of one of two kits purchased by the owner. When it was crashed, it was repaired using some of the parts from the second kit; however the main rotor spindle was not replaced. It later failed as a result of fatigue cracking from the earlier event.
In both cases, the radius at the machined edges of these spindles was cited as a contributing factor.
All parts are machined with radiuses with safety margins sufficient to withstand normal use; however, we strongly advise that affected parts be replaced in the event of shock loading or other event which could result in fatigue failure. This includes restarting the engine while the clutch is partially engaged, rotor over speed, hard landings, and tail boom strikes. The black bump stop installed on the side of the yoke will indicate the need for overhaul resulting from excessive blade flap.
This situation is not unique to SAFARI. Every manufacturer of certified aircraft takes the same position – in the event that extraordinary dynamic forces affect critical components, those parts must be inspected, tested, and replaced as needed. In the experimental helicopter environment, the owner of the helicopter can choose to re-use parts without verifying their integrity.
The current design has been proven by thousands of hours of safe flight, in many Baby Belle and SAFARI helicopters. Since adoption of the present design in 1994, there has never been a failure of either spindle unless unusual forces had been applied.
When considering the purchase of a used SAFARI, please make every effort to determine the history of the aircraft. We will be happy to share any information we might have about incidents involving the helicopter.
If you have any reason to believe that the spindles in your SAFARI are not built to standard, are installed incorrectly, or if you are concerned about their condition, you are welcome to return them to the factory for inspection.