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Archive for December, 2014

Phase 1 Flight Test Complete – Hobbs 40.1

December 22, 2014 1 comment

Monday, Dec 22, 2014

Today I finished the Phase 1 flight test phase with a 3.5 hour flight. The Hobbs meter shows 40.1 hrs as you can see below. I enter the certification into the airframe log and now I can legally take passengers on board and travel to just about any destination I choose. Yippee! I expect Denise will be my first passenger.

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Categories: Flying

Flight Test Continues – Hobbs 31.9 hrs

December 14, 2014 Leave a comment

Sunday Dec 14, 2014

I completed 4.7 more hours of flight test this weekend putting my total at 31.9 hours. Only 8.1 more to complete and then I can take passengers. The engine definitely runs with less vibration since I dynamically balanced the propeller. And my landings continue to improve as I am learning to slow the airplane down before and in the pattern better.

Categories: Flying

Balancing the Prop – Hobbs 27.2

December 7, 2014 Leave a comment

Sunday Dec 7, 2014

I’ve have noticed a little bit of vibration from the engine during the test flight phase so I decided to have the prop balance checked. Since my prop is composite with a wood core, I have a heavy steel crush plate, and I did some composite work on my spinner gap closeouts that I didn’t really try to balance, it makes sense that the overall balance could be off.

I called a guy who balances props professionally but I never heard back from him, so a couple of weeks ago I dropped in to visit Corona Engines to inquire about balancing services. The owner, Ben told me they no longer do prop balancing but they have a balance measuring instrument he would loan to me if I was interested. That caught me off guard but I thought why not give it a try. Yesterday I picked up the balancing instrument and today I put it to use. It uses an accelerometer and an optical sensor for the prop angle. Here you can see the yellow optical sensor and black accelerometer mounted on the crankcase.

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In this view you can see the piece of reflective tape I placed on one of the prop blades to mark the zero degree angle.

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The sensors connect to this instrument which only has two buttons, one for On/Off and one for averaging readings for multiple revolutions.

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I connected everything per the instructions then ran the engine up to 1900 rpm while standing on the brakes. I wanted to go higher but the airplane really wants to move out, even at that rpm. The initial reading was .44 inches per second (IPS) which is significant. No wonder I could feel the engine vibrations. After a number of iterations placing various bolts on the ring gear as balance weights I got the reading down to .085 which is not bad according to what I have read. Anything under 0.1 is considered good. A professional could surely get it better, but I am happy with this considering I did it myself.  In this photo you can see the three bolts/nuts I put on the ring gear. Two are 1/4 inch and the third is an AN3.

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This plot shows the results. The lower curve is the initial unbalance at 1500, 1800, and 1900 rpm. The upper curve is the final unbalance at the same rpms. It seemed to feel smoother running up on the ground. I am anxious to see how it feels when I fly the airplane the next time. It was nice of Ben to loan the instrument to me and it was an interesting experience doing this job myself.

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Categories: Flying