[Sparky69]

This is from the USRA web site: www.usrainfo.org

Thanks to a lot of people for testing various props, we were able to get down to two props that we thought would make the Sundowner a faster and fun plane to fly. The two props were the APC 16x12 and APC 16x14.

I installed the Eagle Tree flight data recorder in my Sundowner. If you have never tried to use any type of flight data recorder it takes some getting used to how the data is recorded and what is the usable format that you want to display.
In any test program you have to have goals and a method that could be reproducible later if you need to go back and run the numbers or if you wanted to try to test some other props at a later date and be confident that you would be getting comparable data.

All that being said my tests flights were conducted yesterday 13 October at our local flying field near Bloomington Indiana about 700' MSL. The winds were less than 10 mph, most of the time calm. temp less than 75.

I would take off and immediately turn onto the course. I did not mill about for the start, just full power into the pylon turns. I did make slight adjustments to the needle valve between flights if I saw a downward slope in engine RPM as the flight progressed indicating the engine was getting too lean as the flight progressed.

I was using a timer box set at 5 seconds so when the plane passed in front of me we hit the timer and I was turning after 5 seconds of straight away. If you do the math that works out to around 800' I would fly laps until my 7 minute countdown timer signaled and then land. I made 3 flights on the 16x14 and two on the 16x12. The numbers that I was recording was indicated airspeed and engine rpm. The Eagle Tree is capable of recording a heck of a lot more info but I was only after the important numbers. I would have recorded the engine temp but I burned up my temp sensor during earlier tests.
After landing I downloaded the information from each flight then put the info on a graph showing airspeed and RPM over time. Comparing between the props and validated by a Nuclear Physicist. The 16x14 is a little faster. The other good thing is that the engine is turning a lower RPM and is noticeably quieter which is good for flying at club fields.
The 16x12 turned an average rpm of 8642 compared to the 16x14 at 8151.
How fast was the airspeed? it really isn't too important I was looking at difference in speeds between the two props. Straight away speeds are influenced by a lot of things not to mention that the airspeed in a full scale airplane has to be calibrated so that installation variables are accounted for. The 130+ MPH claimed other places was not anywhere near what this engine/prop/plane is capable of in level flight.
After all I went supersonic in a Prowler once! (43,000 feet 60 degrees nose down at full power) See why I only did it once, it took me 20,000 feet to pull out!

APC 16x14 is the prop for Parker!!!
Now I am going to go out and try a few really off the wall props just for fun.

Sparky
USRA V.P.