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Broken Pitot Tubes at 92.0Hrs

WJaviation

Active Member
Anyone ever seen a pitot tube broken near the front of the spinner?

On the flight back today I got airspeed unreliable. I was able to make a safe landing, but when I pulled the pitot tube it popped right out of the spinner.

It appears to have cracked circumferentially at about 3 inches form the front. No contact points or any rubbing from the spinner tip. Literally just cracked in open space.

I never noticed any unusual wobbling with the spinner. And I balanced the prop to .06 ips with a dynavibe at about 24 hrs flight time.

Any ideas?
 
Mine broke at the filed flat where the retaining screw contacts the tube. I replaced the tube without filing a flat. So far no more issues. I’d have to check my logs for time in service.
 
I Know! I'm assuming user error, but I can't figure out just what that error is...

For it to break in an annular ring like that, I can only imagine there was a scratched line on the circumference that acted as a stress riser.

When making metal aircraft parts, it’s important to keep all scribed lines within the material that is cut away...
 
Ensure the pitot tube moves less than 1/16" when the prop is rotated thru its full arc in accordance with the plans. I place a 6" scale on the head of a tripod with the scale corner centered on the pitot bore then rotate the prop with the plugs removed. A slight bump on the spinner before tightening the spinner screws will get it centered. Started doing this when an observer commented, indicating he could see the pitot tube moving with the engine running.
 
I always use a little Boelube on that part of the tube in the spinner insert. Don't know if that was factor or not.
 
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