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Another RV guy contacted me this morning to tell me that a friend recently had a large overspeed on his RV He said that his friend found that the rpm in his event was high enough that Hartzell said the prop had to be scrapped, rather than inspected and returned to service.

I sent an e-mail to Hartzell tech support asking them about this, and got an answer this afternoon. For short duration events (20 seconds or less), the official info in the Special Inspections sectionj of Hartzell's Standard Practices Manual says:

  1. overspeed of 100% to 110% - no action required
  2. overspeed of 110% to 115% - inspect prop and return to service
  3. overspeed of 115% to 120% - overhaul prop and return to service
  4. overspeed of greater than 120% - scrap the prop

The recommendation to scrap the prop at 120% overspeed or higher is partially due to the centrifugal loads, and partially due to the potential for much higher harmonic vibration loads at rpms above the normal rpm limit.

My overspeed was about 148%. The loads at that speed would be more than twice the normal loads, which made me nervous about continuing to use this prop, even if it had been inspected. Hartzell's official inspection info pretty much makes the decision for me. I'll scrap the prop and buy a new one. Maybe I can sell it to the airboat guys.

This is getting more expensive by the day. To put salt in the wound, the Canadian dollar to US dollar exchange rates are moving in the wrong direction, and very quickly. Not too many months ago, the two dollars were pretty much equal in value. Now the Canadian dollar is worth less than 0.80 US dollar.

Terry, bless her heart, has been extraordinarilly understanding. She offered to work an extra day per week for the next few months, and she will use more restraint when shopping. I was in the habit of taking overtime as banked time off - I'll start taking it as cash for awhile.

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