Guys:

I bought an Eagle Tree system, with altimeter, 3-axis accelerometer, and GPS. Mounted the components on a 3x5" piece of ply, and installed adapter mounts in all my aircraft so i can move it about.

My question is this:

I was flying my Revolver 90 / DLE55RA gathering performance data, and I am unable to explain why the GPS speed (averaging upwind and downwind) exceeds the theoretical max.

I was out in 15 mph south winds , and ran some S/L speed runs. Averaging 2 upwind (86 mph ground speed) and 2 downwind runs (116 mph groundspeed), directly into, and directly with the wind (averaging 15 mph), I averaged 101 mph AIRSPEED. I had a week or so earlier, in different wind, gotten an estimate of 103 mph airspeed, so these two sets of data were pretty consistent.

I am missing something, however:

I turn 6800rpm on the ground with a Xoar 22x10 prop; that gives me a theoretical max airspeed of about 65 mph, not 101 mph.

The Eagle Tree GPS calibrates - when i take it for a ride in my truck, the GPS speed matchs my garmin gps speed, and matches my truck's calibrated spedometer, so I am pretty confident that I have accurate GPS data from the Eagle Tree system.

How then do I get airspeed above theoretical max? Yes, the engine unloads some, but doing the arithmetic, it would have to unload to >10,000 rpm to exceed 100 mph, and i doubt that a DLE55RA would unload that much.

What is the aerodynamic, or other, explanation?

I bought an Eagle Tree system, with altimeter, 3-axis accelerometer, and GPS. Mounted the components on a 3x5" piece of ply, and installed adapter mounts in all my aircraft so i can move it about.

My question is this:

I was flying my Revolver 90 / DLE55RA gathering performance data, and I am unable to explain why the GPS speed (averaging upwind and downwind) exceeds the theoretical max.

I was out in 15 mph south winds , and ran some S/L speed runs. Averaging 2 upwind (86 mph ground speed) and 2 downwind runs (116 mph groundspeed), directly into, and directly with the wind (averaging 15 mph), I averaged 101 mph AIRSPEED. I had a week or so earlier, in different wind, gotten an estimate of 103 mph airspeed, so these two sets of data were pretty consistent.

I am missing something, however:

I turn 6800rpm on the ground with a Xoar 22x10 prop; that gives me a theoretical max airspeed of about 65 mph, not 101 mph.

The Eagle Tree GPS calibrates - when i take it for a ride in my truck, the GPS speed matchs my garmin gps speed, and matches my truck's calibrated spedometer, so I am pretty confident that I have accurate GPS data from the Eagle Tree system.

How then do I get airspeed above theoretical max? Yes, the engine unloads some, but doing the arithmetic, it would have to unload to >10,000 rpm to exceed 100 mph, and i doubt that a DLE55RA would unload that much.

What is the aerodynamic, or other, explanation?

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