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Saturday last weekend, the day before the big engine overspeed, I did some climb performance testing. I had hoped to do the climbs centred on 5000 ft, but the air wasn't smooth enough. I found smooth air between 7000 ft and 9000 ft, so did the climbs centred on 8000 ft.

The aircraft was loaded as per a solo flight - just me, full fuel and no baggage. The average weight for all the tests was 1583 lb. I did two climbs at each speed, on reciprocal headings at 90 degrees to the forecast wind, starting below 7000 ft so I was nicely stabilized on speed at 7000 ft, and continuing past 9000 ft. I used the recorded data to get the average rate of climb for each run from 7000 ft to 9000 ft, and averaged the rates of climbs for the two runs at each speed. I then did a curve fit on the raw data, and found that Vy at that weight was about 90 KIAS, and Vx was about 68 KIAS.

I'll repeat this test condition with the new prop, and also at gross weight. Eventually I'll correct the results for the effect of OAT on the engine power

Based on these results, I would expect that Vy at 1800 lb would be about 95 KIAS.