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I didn’t get flying last weekend, due to terrible weather. I did get the landing light bulb replaced on Sunday - I had noticed some time ago that it wasn’t working. I don’t plan to do any night flying, so I don’t need it as a landing light, but it and the taxi light can be selected to flash alternately, which makes it much easier for other pilots to spot this small aircraft. The flasher system won’t work if only one of those lights is operative, so I was keen to get the burned out bulb replaced.

Today I took advantage of the good weather to do some performance testing. I had noted since I started flying in November with the rebuilt engine, that the indicated airspeeds for any given power setting seemed to be several knots faster than I was seeing before. On the one hand, I was happy to see the aircraft apparently performing better, on the other hand I was suspicious of these speeds. Could there be some new error in the airspeed system?

Today I took a few minutes and did a four sided box pattern at 160 kt IAS, hand recording the data needed to check the accuracy of the indicated airspeed. I found that the airspeed was still fairly accurate. In the distant past, before the aircraft was painted, I found that there the indicated airspeed was about 1 kt too high in this speed range. After the aircraft was painted, the error seemed to have changed by roughly 1 kt, so it was approximately correct in this speed range. Today, I found that the indicated airspeed at 160 kt was about one kt too low. The test wasn’t of perfect quality, but the result should be good to plus or minus 1 kt.

Next, I gathered some cruise speed vs power data. Assuming the airspeed errors were unchanged from my original testing, the speeds I got today were about 5 kt faster for a given power than they were in the distant past. If the airspeed system errors have changed by two kt, as today’s single test point might suggest, then the speeds I got today were about 7 kt faster than before. Great!

Today’s data is Flt 214. The blue line is the average of all the earlier data.

 


I had always been somewhat suspicious of the engine power since it came back from the big overspeed event on flight 13. I wonder if perhaps something was not right with the engine all this time. Now the speeds I am getting are much more in line with what I would have expected.

 


Update - 06 May 2013 - I discovered a very stupid error when I did the data analysis from this flight. I failed to convert the hand recorded Outside Air Temperatures from deg F to deg C. I reran the analysis after correcting this error, and now it shows the hand recorded results from Flight 214 were about 2–3 kt faster than the laptop recorded data from 2010. I finally got my data recording system working again, and I plan to record cruise performance data on several flights over the summer.

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