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Author Topic: BETA Light  (Read 2490 times)


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BETA Light
« on: May 08, 2023, 11:09:14 pm »
I learned something in my last recurrent with Barry Lane. He asked me if the "beta" in the 331 engine is an acronym or a greek letter. I assumed, of course, that it was a greek letter and that buried somewhere in the engine was an alpha and a gamma... nope! It's an acronym, for "Below Effective Thrust Angle."

This came in handy for me last week when I got a BETA light just after takeoff. Everything was normal, engines were running fine, and I was climbing. I pulled the RPM back slightly and the light went out. Once I got up to cruise, I pulled out the checklist (FlightSafety abbreviated version), and read that I was supposed to attempt a "landing at altitude" to see if I had any control problems, and if I did, I should shut the engine down.

Well, that just seemed absurd, since at FL280 the engine was running fine, making normal power, everything smooth, as it was for the entire takeoff and climb. There is no possible way that one prop was below effective thrust angle (i.e. in flat pitch or reverse) and the other one was making full power-- if that were the case, I wouldn't need a light to tell me something was wrong!

That put my mind at ease, and when I got back home (BETA light came on briefly when I went to high RPM before landing), I called Dan Black at Aero Air. He told me there was no question that it was an oil pressure switch, and it was easy to change out.

So once in a while, you might think about the checklist before blindly applying it!