Important Event Report!!!

[T&C Brown]

Well said Robert!!

Not to ask the obvious, but how were these props pre-flighted and installed??  

Were they installed too tight, or perhaps too loose?  Are the hubs being crushed during installation?

Next thing is how tight is too tight??  Is there a magic number of inch / foot pounds for torquing a prop?  I don't know.  But I do know that after installing a new prop, I go back and check for tightness after the first run.  I believe the heat from an engine is hot enough to soften the hub and cause the nut to loosen, therefore increasing a chance for un-due vibration.

Are the spinner slots, aluminum ones in particular, coming in contact with the prop?  If so, that's a big no-no!

Or perhaps is the  diameter of the prop hub too large for the shaft and causing the prop not to be centered and therefore "walking" around on the hub?  Does your engine have a metric diameter shaft??  Are you using a metric prop reamer?? 
And most importantly, are these props (three blades in particular) properly balanced before use.  I don't know right off hand the proper procedures to balance 3-blades because I don't use them, but I know someone out there does.  Please enlighten us.  

I can't count the number of times I've seen individuals take a new prop out of the package and place it directly onto the plane.  I see this most at contests were a balancer is usually not handy and or available.  Do we go back and re-check props for balance from time to time?

I think before we start pointing fingers at different props and brands we need to look at the above things and then ask ourselves if were watching out for these "Gotchas".

I am by no means some prop expert.....I barely know what end of the plane the prop goes on.....
This is just my two cents on the situation.

T-Bone


  ----- Original Message ----- 
  From: RUDDERCABL at aol.com 
  To: discussion at nsrca.org 
  Sent: Wednesday, September 07, 2005 9:56 PM
  Subject: Re: Important Event Report!!!


  I would like to urge that there not be an automatic condemnation of any prop or prop engine combination. 

  One of the very first things we learn in this hobby is that "PROPS CAN FAIL". There have been several reports lately of 3 blades failing ( including mine ), but there have also been some 2 blade failures that haven't been reported. Not saying that there is a cover up or anything, but that failures have been by individuals that realize this can happen and take a rational approach to the issue rather than a knee-jerk reaction. 

  When mine failed, one of the first questions I got was " Well I quess you won't be using three blades anymore?" My answer, " Yes I will. If it works with the plane/ engine combination, there will be a three blade on there".

  To me, the most important thing about these reports is that they should be reminders that these things can and do happen. Everyone of us has at one time or another subjected ourselves to the danger zone of the prop arch. Some of us repeatedly violate this rule of physics. Take these reports as reminders that we need to be vigilant about the care of our props and our own safety around them.

  Robert Gainey
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