Test notes
Below are the notes I made on Tuesday. I tried to attach photos but the image button in the tool bar doesn't work anymore - sorry.
Bob Axsom
After I got to the hangar it took two hours to complete the work to get ready to fly. All of the wires hanging out of the wing had to be terminated, insulated and secured until the fuel tank and stock wingtip are reinstalled. The fuel line which I had capped earlier had to be secured. Then I put the new short race tip on the left wing and installed the 47 screws. The approach used to place the mounting holes in this wingtip was better than that used on the right wingtip. Drilling through the dimpled holes in the wing skin was more accurate than marking the tip through the wing skin holes and drilling on the work bench separate from the wing.
I took some photographs and it was time to fly. I advised the tower that I had removed three feet from the wing and may return fairly quickly. The controller chuckled and said “Thanks for the heads up.”
The take off was not unusual and the flight progressed normally. In accordance with the U. S. Air Race Handicap Procedure (
http://www.us-airrace.org), I climbed to 6,000 ft to record the temperature of 16 C. Then subtracted 3C to determine that the speed run would be flown at 4,700 ft for a 6,000 ft density altitude.
I contacted Razorback Approach and told them my intentions to fly a triangular speed run at 4,700 ft.MSL. They assigned squawk code 0440 and told me to advise them when I was ready to return to Drake field.
I dropped down to 4,700 ft, turned north, closed the vents, went to wide open throttle, maximum rpm (which turned out to be 2730) trimmed for straight and level flight, activated the autopilot (Pictorial Pilot) on a track of 000 degrees (magnetic), pressed the Altrak “ALT” button to hold 4,700 ft and monitored the GPS ground speed. When the speed stabilized I recorded five consecutive readings at twenty-second intervals. The speeds were 182, 182, 182, 182 and 183 kts.
I disengaged the autopilot and turned southeast to 120 degrees and repeated the process on the new track. The speeds were 170, 169, 168, 169 and 168 kts.
For the final leg I turned southwest to 240 degrees and repeated the process for the last time. The speeds were 183, 182, 181, 181 and 180 kts.
The handicap procedure requires deviations of no more than 1 kt but time was short and experience has shown that this is good enough.
On the way back to Drake I pulled back the power and slowed to determine the clean stall speed. It is 59 kts. The landing was fairly normal but the sink rate seemed higher than the configuration with three feet longer wingspan even with the reduction in weight of 100 pounds of fuel and 40 pounds of structure.
When I got back home I brought up the National Test Pilot School spreadsheet for three leg speed runs and determined that the speed for this test run was 177.8 kts or 204.6 mph and the wind was 9kts from 125 degrees. This is an increase of 3 kts over the previous best configuration.
I want to do some fiberglass work for a better fit at the leading edge and perhaps install a few floating platenuts (only one or two are bothersome) but it is ready to race right now if necessary. I will certainly use the short race wingtips in the Memphis 100 cross country air race.
