"The woes of flying with a fixed pitched prop."
Bill;
I fly a fixed pitch prop and a manifold pressure gauge. Initially I was skeptical, but it turns out that Propeller RPM remains nearly unchanged at high speed decent with an inch or three reduction in manifold pressure. Yet the power delivered and the thrust are reduce as desired. It takes a fairly large power reduction at high speed to see much of a decrease in RPM.
For making power adjustments, I control RPM in the pattern, and combination RPM/Manifold pressure in transitional flight, but at cruise, I mostly watch the Manifold pressure.
When flying near Vne, the RPM may be quite high, possibly higher than you would want to normally operate. I don't see a real problem here, a few moments of 2900 RPM won't hurt the engine while you establish your airframe's integrity. For me, Vne testing is the way VAN intended. It's something to approach carefully, but not overly concerning. I don't believe any RV has suffered a Vne testing failure, so statistics favor a safe outcome if you built well.
Attend any IAC aerobatic competition. Those Pitts S1's with Lycoming 180HP and fixed pitch climb prop run up as high as 3500RPM on the down lines! And they do it over and over again without worry.
That's beyond my comfort level, but it's a data point that a slight overspeed for testing won't do harm.
By the way, my RV-8 has a helicopter IO-360 rated to 2900 RPM.
Bill;
I fly a fixed pitch prop and a manifold pressure gauge. Initially I was skeptical, but it turns out that Propeller RPM remains nearly unchanged at high speed decent with an inch or three reduction in manifold pressure. Yet the power delivered and the thrust are reduce as desired. It takes a fairly large power reduction at high speed to see much of a decrease in RPM.
For making power adjustments, I control RPM in the pattern, and combination RPM/Manifold pressure in transitional flight, but at cruise, I mostly watch the Manifold pressure.
When flying near Vne, the RPM may be quite high, possibly higher than you would want to normally operate. I don't see a real problem here, a few moments of 2900 RPM won't hurt the engine while you establish your airframe's integrity. For me, Vne testing is the way VAN intended. It's something to approach carefully, but not overly concerning. I don't believe any RV has suffered a Vne testing failure, so statistics favor a safe outcome if you built well.
Attend any IAC aerobatic competition. Those Pitts S1's with Lycoming 180HP and fixed pitch climb prop run up as high as 3500RPM on the down lines! And they do it over and over again without worry.
That's beyond my comfort level, but it's a data point that a slight overspeed for testing won't do harm.
By the way, my RV-8 has a helicopter IO-360 rated to 2900 RPM.