Vne Testing

[SHIPCHIEF]

"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.

[rzbill]

Scott,
I have never had the opportunity to fly a fixed pitch with MP gage. Interesting that it is only a few inches of MP, but it is still that, a power reduction. That was the point of the one-liner. Fixed pitch descent technique would normally include a power reduction of some amount. Since most trainers are fixed pitch, that is what we are taught. I get your points about acro but I'm not going to overspeed my engine like that either.

With a CS, I fly descents like DavidZ. Push the nose, smile at the speed, watch for the Vne indication and reduce power as it starts hedging over 75% at lower altitudes. The point of my first post was that it was the first time TAS Vne became an issue since I was flying higher than normal and descending at a faster rate than normal.

Originally Posted by David Z

Unfortunately RVs typically do not have a barber pole easily displaying the IAS limit at altitude.

RVs with steam gages would certainly fit that, and there are plenty. I think most if not all of the glass EFISs will do the TAS conversion and show a TAS corrected Vne on the airspeed tape. My GRT does so I assume the others do too.