When ‘just buy a new engine’ isn’t the right answer

Q: I have a Beechcraft A60 powered by Lycoming TIO-541E1C4 engines, with approximately 1,100 hours on each. I am experiencing intermittent, uncommanded propeller feathering on landing rollout or during engine shut-down on the right engine.

I’m frustrated at this juncture simply because many are defaulting to the “just buy a new engine” solution while myself and others realize that doing so without determining exactly what the root cause of this issue is seems foolish and professionally and technically timid.

I’ve read your comments on similar problems on other aircraft in the past and wonder what you have to say? Where can I go to find the answers and maybe even a solution short of a complete engine replacement?

Thank you for your time and expertise.

Lee Collins

Answer from Paul McBride: The first thing that came to mind regarding your experience with an intermittent prop feathering condition on roll-out or during engine shut-down was that you are either experiencing a higher-than-normal engine oil temperature, possibly from a higher OAT, or for some reason a lower engine oil pressure at idle rpm.

My first suggestion is to confirm the exact engine oil pressure at normal operating temperatures using a master calibrated gauge at the oil pressure takeoff point at the engine. You may also want to perform this same check on the left engine just to compare readings. Any reputable maintenance facility should have no problem conducting this check.

I’d also recommend the actual oil temperature be checked and compared between both engines. You may find that the engine oil pressure at idle rpm on the right engine is a little lower compared to the left and can possibly be adjusted upward by adjusting the oil pressure relief valve on the right engine. 

Another thing that comes to mind: What type of oil are you using in your engines?

If, for example, you are now using a multi-grade weight oil, I’d suggest you consider going to a straight weight oil like SAE 50 weight during the warmer months at your next oil change just to see if this makes any difference.

However, I highly recommend you conduct the troubleshooting steps mentioned earlier so we can obtain a good starting point. 

If you have oil analysis done on a regular basis, has this indicated any change in any of the materials recently? It’s possible that if lower oil pressure is an issue, it may be the result of bearing wear. Oil analysis may provide some answers if we see higher numbers of certain materials.

One more thing, Lee, that I’d suggest is contacting the Duke Flyers Association. From my experience, this organization has more knowledge regarding the Beech Duke, including all aspects of operations and maintenance, than you can imagine.

I believe that by doing some simple troubleshooting you will be able to sort out the feathering issue and hopefully it will be something rather easy to fix before you have to make a decision regarding an engine replacement.