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RV9A Performance Numbers

dbaflyer

Well Known Member
This is the first time I've flown at WOT at altitude. The first time i was going over 2700RPM and was unsure about staying over for a little bit of time. This time i wanted to measure top speed so I stayed at WOT long enough to do that.

So at 2750 RPM, 21.4 MP, 73% power, 9.7GPH, 138 IAS, 162 TAS, 8670 DALT

When I compare this to Vans web site 75% power and 8,000 solo weight they state 187MPH or 162.5 KT. This matches up pretty well and I'm happy with that.

So the questions from a newbie here is... If I'm at full throttle producing 73% power, I presume with a fixed pitch prop there is no more in the tank so to speak. This is going to be my maximum speed. So is the only way to get to Van's top speed number with a constant speed propeller?

This is with an O-320 carburetor running one Mag and one EFII ignition. The prop is a 3-blade Catto 67x70 carbon composite.
 
Uh, no. Fixed pitch props can, in general, match the pitch range of a constant speed prop from most coarse pitch (cruise) to most fine pitch (climb). So, in general, a constant speed prop won't gain you any extra speed over a fixed pitch prop. The advantages of a constant speed prop are uniformly good performance over the speed range of the airplane, more drag on descent and landing, and, if your plane is tail heavy, more weight up front.

However... the Sensenich metal fixed pitch props have a 2600 RPM redline, so the engine won't be able to achieve max RPM, hence, won't achieve max power. So when I flew over West Texas a few summers ago with the autopilot holding altitude, I had to retard the throttle in the updrafts to avoid overspeeding the prop. Presumably would not have to do this with a constant speed prop.
 
Top speed is not found at 8000 feet

Try your top speed check at sea level. My 9A made 172 Knots true. Of course top speed at sea level is largely irrelevant to the way we use our airplanes.

-Andy
 
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