Safety Alert "Skull Cap" Spinner

[VictorBravo]

I dodged a $2000 bullet today and maybe worse. Recently someone had made a post that mentioned changing the screw and clip nut holding the little skull cap spinner from a sheet metal screw to a machine screw. Very timely. Two days ago I was starting my engine to take off for the dry lake. When I pulled the prop thru I heard a little metallic tinkling somewhere near the prop. I removed the skull cap spiinner and found nothing wrong (so I thought). I put it back on, tightened the screw and went off.
Getting ready to fly a trim tab test flight today I noticed the screw was not really tight, so I hit it again with the screwdriver... and went off flying. When I got back in the hangar I noticed that the screw was backed out, three threads showing in front of the skull cap! When I went to take it off and see what was going on, I found that the little Tinnerman "clip nut" was broken. so that HALF of the stamped "threads" of the clip nut were missing. The nut had broken so that half the hole ffor the screw was missing.

The skull cap was tight enough around the base, held in position from sliding around by the prop bolts. Becxause it could not move, the screw was holding it in place, but only on one half of the screw diameter. Because of that, the vibration had backed it out almost all the way.

One more touch and go and I probably would have lost the skull cap, which in turn would have wrecked my polished aluminum propeller.

Thanks for looking out for me, C. G. !!

Please, take a minute to check the little clip nut holding the spinner screw. Remove the nut plate entirely and try to break it with your fingers. See if it is cracked. I plan on replacing mine with a 10-32 machine screw and the appropriate clip nut post haste.

[NC36061]

Re: Safety Alert "Skull Cap" Spinner

Years ago my dad and I were "in the pattern" at our farm strip with the old '41 when the skull cap spinner decided to depart. It was a very interesting experience, but we landed without incident or damage. As I recall, we weren't sure what had happened until we got on the ground. I don't suppose the spinner could do a whole lot of damage structurally,given its low mass, but it sure could screw up a windshield or nice paint job at least. It could also lead to a lot worse if the distraction were allowed to overwhelm a guy.

Dave

[1948TCARTDRIVER]

Re: Safety Alert "Skull Cap" Spinner

I thought the word was out on this and everyone already replaced the old sheet metal screws with proper AN/MS hardware.
I ran into this problem shortly after buying my T-Craft in 1991. On preflighting the airplane I noticed the screw for the skull cap spinner was missing, on further investigation I found the the head of the screw had separated from the threaded portion. The spinner stayed on during the previous flight because it fit snugly against the prop bolts. I also picked up a small ding on one of my propeller blades from the departing screw head. I promptly modified my spinner attachment by using a 10-32 screw and nut plate on my attach bracket. I also replace this screw at every other annual.
On relating my tale to a fellow Taylorcraft driver he informed me that he had the same problem, only his spinner departed in flight and managed to not hit anything on its way south. He modified his with a 1/4 inch MS screw and nut plate.

If anyone does not know what holds their spinners on take the time to check, it could save you some grief.

[VictorBravo]

Re: Safety Alert "Skull Cap" Spinner

This morning I replaced the "clip nut" with another one having 10-32 threads, and installed a shiny stainless 10-32 screw. Flew about 1.5 hours today and checked it when I got back, no looseness at all. But it is still on my pre-flight list and will be from now on.