I’m interested to know if anybody knows of any sudden failures of Phenolic Control Pulleys.
Obviously they are inspected every Annual, lubricated and the ones with limited travel checked for “flat spots” – I can’t recall seeing any AD’s or Accident Reports. I am also convinced that most old Aircraft don’t ever have them replaced if they are in good condition so there must be lots of these in service 40-50 years old.
Do they get more brittle with age?
Any comments welcome
Individually there are very few failures, the cable cutting grooves in them along with rough bearings are the usual reason for replacement .
I replaced all the pulleys and most of the cables on both by Cessna 152’s when I had them and clearly some of the pulleys had flown 12,000 hours, the result was a considerable reduction of control system friction but none of the pulleys was totally unserviceable ….. just well past their best.
It’s not at all obvious that they are lubricated once a year – some are hard to get to, and hard to lubricate.
On Luscombes the aileron pulleys are a well known upgrade item. The originals have only plain bearings and on many planes they are seized or nearly so. A lot have been in service over 70 years. Replacing them with new ball bearing pulleys can make a big difference to the aileron feel – which is then still heavy, but a lot better.
I don’t think they get brittle with age or fail catastrophically – phenolic is pretty good material.
Thanks both of you – Your feedback is much appreciated
