Back in January, I reported an apparent increase in performance since I reinstalled the engine. I had noted that the aircraft appeared to be several knots faster for the same power setting than it had been when flying over the last several years. My data recording system wasn’t working properly, but I hand recorded some data and plotted power vs speed (after correcting to standard conditions). This appeared to show about a 5 kt increase in performance.

A week ago I finally debugged the data recording system, so I recorded data on the laptop for a few conditions. This data showed results a bit slower than the hand recorded data from January. The latest results were 1–2 kt faster than what I had recorded over several flights in 2010, but that was quite different than the 5 kt increase I had seen in January.

I took a closer look at the data analysis from January, and I found a glaring, rookie error - I had failed to convert my hand recorded Outside Air Temperature numbers from deg F to deg C. Duh! I redid the analysis and now it shows results 2–3 kt faster than the 2010 data. Neither the hand recorded data from January nor the laptop recorded data from a week ago are perfectly clean, so this small difference between the two results is not surprising. Now that I know my data system is working again I’ll gather a bunch more cruise performance data.