Thanks to ASRA
Thanks to ASRA
Murray, thanks for the quick information.
I don't want to dispute this finding, but I have a lot of experience with the Magni control rods. As Birdy mentioned, it is very hard for me to understand how an experienced pilot would not recognize that a rod is lengthening - the flight stick position would be radically different. If adjusted correctly, there are over an inch of thread on both bearings on the ends of the rods - on all rods. Just 1/4 inch of misadjustment of any control rod, or any combination, should readily be noticed in flight?????
In America, we assemble all of our Magni gyros, so we might have more awareness of this issue. I will pull the adjustment procedure out of our Assembly Instructions and post them here. But, the final adjustment has always ended up with much more than just a few threads engaged at every point!????
However, we have always stressed that all of these rod end bearing shank threads must be locked - Left and right hand locking nuts are provided. And, per the procedure I will post, it is very simple to lock these locknuts (someone posted above that it is difficult, but it is not - BECAUSE they are left and right handed.)
On any gyro control rod designs, it is important that these rod end bearings do not rotate on the shank threads. The major reason for locking nuts coming loose is that the rod end bearings are not properly rotated to allow the needed ball rotation range. This is an adjustment problem on many gyros. The Magni design uses special rod end bearings on the lower end of the lower control rod to provide the full cyclic range needed. We instruct all Magni fliers - and any gyro flier - to check the full rotation of the control rods on Preflight. This is simple, but may not be being done my some gyro pilots: With the cyclic stick in the full "corners" of its range - 4 corners - check that all control rods are able to rotate on the rod end balls - at least a bit. This ensures that the cyclic range is not being limited by the rod end ball rotation range. This preflight check also will find any loose rod end locking nuts - the rods should only rotate, at all cyclic extremes - 4 corners.
This means that the rod end bearing adjustment and tightening is critical do be done correctly - see procedure posted. If the rod end bearings are not properly tightened in the correct rotation that allows full range on the "balls", cyclic operation can force the rode end bearings to rotate on the shank threads - loosening the locking nuts and stressing the rod end bearing shanks. The adjustment is critical - and I wonder if this machine had these rod end bearings adjusted properly after its repair.
My major suggestions are:
- Adjust and tighten the locknuts on the rod ends properly to provide full rotation range on the balls and assure that the rod ends balls do not limit the cyclic range.
- Perform preflight checks to at least verify that the rods are rotating on the balls of the rod ends, and not on the threads of the bearing shanks – verifies locknuts are tight.
- For Magni gyros, be sure the rod end bearings are installed in the proper locations - to provide full range of cyclic control without "bottoming out" on the rod end balls. The special bearings - Aurora HXAB-4T - should be installed on the lower end of the lower control rods. Please check this on the accident gyro. If not proper, this could force the lower rod to turn on the threads and loosen at least one rod end bearing on its threads.
In ten years of operating my personal Magni M16 gyros, my preflights have found one rod end bearing loose on it threads. My concern for this is more the stress and wear on the threads and shank - it is hard for me to imagine a control rod unthreading as far as would be necessary to come apart without the pilot noticing something is really wrong with the stick position. And, the locknuts on both ends of the control rod would have to be loose to unscrew!!??? Perhaps though, in the U.S., our builders might be more aware of such things since they have assembled these systems themselves and are familiar with the adjustments and adjustment procedure.
Please let me know if I can help at all. Please note my comments and the referenced procedure should not be construed as official response from the Magni Gyro srl – in Italy. This is from the guidance the factory has provide me and from our experience with building kits in the U.S.
On the attached, I have highlighted what I consider to be the pertinent areas. (I had to split these pages up and crop the pertinent stuff out of them to fit as attachments here.)
Thanks, Greg Gremminger