I have been having trouble with the throttle response of my P3. I called the factory support line and talked to their engine guru. He suggested that I run the P3 on the ground, throttle up until I get into the problematic RPM range, and then give it a little shot of prime. (The primer shoots gas directly into the carburetor and is generally used only during starting.) The thought was if I gave it some prime, and then engine bogged down, then I’m running too rich, if the engine revs up, then I’m running too lean with the stock settings in the carburetor. I tried the test and it bogged down big time.
Six Chuter factory support recommending I change the clip position on the jet needle. With out going into carburetor theory the jet needle controls how much gas the carburetor delivers to the engine. Moving the clip up makes the engine run leaner, moving it down makes the engine run richer. I moved it down first, and the problem became worse. I moved the clip up and throttle response was good throughout all RPM ranges!
I did have a momentary scare when I saw that there was a split in the clip on the jet needle. I had never noticed it before but was assured it was completely normal and was part of the design. Six Chuter factory support assured me this was normal. And a friend of mine who has an extensive ultralight history assured me this was normal. In fact, he sent me an article by Chris Wolf on rebuilding the Bing 54 carburetor which has this excerpt:
If you look closely at the E CLIP, you’ll see that it has a break in the
metal, right next to the curved part of the clip that snaps around the body
of the JET NEEDLE. This is as it should be. Rest assured that you didn’t
break the clip when you pulled the JET NEEDLE out of the piston.
Well that’s exactly what I did. I dropped the clip on the ground and thought I broke it! So glad Jim Volk sent me that article.
Now that I have the carb adjusted properly I’m going to give it a test fly tomorrow and see how it works. I’m hoping this cures the problem and I can start working on my landings again.
I’m not big on naming inanimate objects. I’m not good at it. However, when a fellow P3 pilot suggested that since I used to work right outside the gate to Moffett Field and I had P-3 Orion Sub Hunters flying overhead all day, and since I was working for the company that manufactured these airplanes, Lockheed, that I call my P3… Orion. And a name is born! This same fellow also quipped that I should check the belt drive on the propeller from time to time, as he put it, don’t for get to check Orion’s belt!