Lyc IO-360 M1B with MT CS prop.
About 3 months ago as part of my pre-first flight engine checkout, I did a full power static run and was pleased to see the full power RPM stop at precisely 2700. On my first flight some weeks later I noted full power RPM on takeoff at 2680 (good enough for me). Well as the 40 hour fly off continued I started to notice on each subsequent takeoff the full power RPM contained to drop. By the 25hr mark I was getting between 2600 and 2640 RPM on takeoff. After 40 hrs the takeoff RPM has stabilized around 2600 to 2630 RPM.
My question is what has caused this RPM drop? I live just outside Las Vegas and although I always fly in the relatively cooler mornings, it's still significantly hotter now than it was when I did the first static test. Could the increase in pressure altitude explain the drop?
About 3 months ago as part of my pre-first flight engine checkout, I did a full power static run and was pleased to see the full power RPM stop at precisely 2700. On my first flight some weeks later I noted full power RPM on takeoff at 2680 (good enough for me). Well as the 40 hour fly off continued I started to notice on each subsequent takeoff the full power RPM contained to drop. By the 25hr mark I was getting between 2600 and 2640 RPM on takeoff. After 40 hrs the takeoff RPM has stabilized around 2600 to 2630 RPM.
My question is what has caused this RPM drop? I live just outside Las Vegas and although I always fly in the relatively cooler mornings, it's still significantly hotter now than it was when I did the first static test. Could the increase in pressure altitude explain the drop?