Old 6th Dec 2018, 18:06
  #952 (permalink)  
Join Date: Jul 2003
Location: Brum
Posts: 545
Originally Posted by [email protected] View Post
OAP - the nut at the duplex bearing end was clearly overtightened - hence my comment about assembly problems. It may be that the TR pitch change mechanism has to be taken apart and greased regularly which ,might make the over-tightening a servicing error instead.

If the nut is over-tightened and impinges on the duplex bearing, you have a probable cause for the excess heat and seizing of the bearing.
Hang on, doesn't the report suggest the overtightening is from the spining shaft...?
ie Wind-up in the shaft has pulled the spider nut down and unwound the servo end?
Page 7.
Am I miss-reading this?

Sufficient force and torque had been applied to the castellated nut on the actuator end ofthe control shaft to friction weld it to the pin carrier and to shear the installed split pin. Theobserved condition of the duplex bearing and the increased torque load on the castellatednut that remained on the spider end of the shaft is consistent with rotation of the tail rotoractuator control shaft. Whilst the shaft was rotating and a yaw control input was applied, theshaft “unscrewed” from the nut, disconnecting the shaft from the actuator lever mechanism,and causing the nut to become welded to the pin carrier.

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