R66 Service Letter SL-01 (Cracked MS21042L-Series Nuts)

[bizjetplt]

Good day everyone. This question goes out to other Robinson R66 operators.

How many operators have experienced any fractured MS21042L-series nuts on the rotor head blade attachment ring?

Our helicopter has approximately 250 hours total time and we have already had to replace several of the self-locking nuts described above. We have not received any valid explanation as to why these nuts are failing prematurely. Feel free to contact me off line if you prefer.

Thank you.

JD

[Ian Corrigible]

JD,

You might want to try asking the question over on the RHOG (http://www.robinsonhelicopters.org/index.php?option=com_jfusion&Itemid=53).

I/C

[noooby]

A bad batch from a supplier. Other Helicopter OEM's have had the same issue and have issued Alert Bulletins for them to be removed from service.

[nomorehelosforme]

Would appreciate any comments on OEM spare's suppliers, not just for Robinson. Will be honest I'm considering a new career with an OEM spares supplier for both fixed wing and helicopters. Thanks in advance for any comments.

[Gemini Twin]

If it's a bad batch, it's the same "batch" that has been failing for at least 20 years leading to some serious accidents. In some cases, 50's -60's time frame, they were used in flight controls and if you were very lucky the connecting bolt didn't fall out in flight. Some years ago Hiller issued a SB to remove the standard bolts and L series nuts and install drilled bolts, slotted nuts and split pins. They seem to be OK in fixed wing designs but I'm not sure they should ever be used in helicopters, at any location.

[bizjetplt]

@ Ian - Thanks. I just posted the question there also.

We were contacted by RHC today with a request to exam the nuts that have fractured. I'll post more info once we learn more.

JD