Conducted 09/30/2012 –
With the propeller now functioning correctly and the engine still performing well we were ready to reattempt the ASI calibration. we had decided to try a different calibration method with involves flying 3 (or 4) separate headings at a set airspeed and altitude. So we modified the protocol 4 test card and after having checked the plane over thoroughly from the previous days flight, set out to finish a test we started almost 3 months earlier.
John’s flight report is below:
“This morning I got out the airport about 8am, it was a nice 52F outside. I saddled up and with no one else to slow me down, I was in the air a few minutes later. I did my normal climb out to 5000′ and started setting up for my ASI calibration work. 3 legs each at 100, 120, 140, and 160kts, all 90deg apart. I called out all my data to my wife on the ground, so I could concentrate on holding airspeed, heading, and altitude accurately instead of writing. The airplane performed flawlessly again. No issues with engine or prop. My only complaint is my lack of trim authority. I have the Strong pitch trim, but it is not mounted per his instructions which I’m certain is the issue.
Even with full nose up trim she’ll dive if I let go of the stick. This is not to be confused with elevator authority, I’m able to control the plane just fine, just not take the control forces away. I believe the issue is that my mounting method doesn’t have the same mechanical advantage as the instructions method. So we’re working to correct that.
When I was all done I came back down and setup my approach, again carrying 90kts on final, and again setting it down very gently. Another landing with the prop surviving. I taxied back to the hangar, checked the hobbs (another hour of flight testing in the books), and proceeded to pull the cowls and covers again.
While waiting for the engine to cool down so I could inspect things, I fed the data from my ASI calibration runs into the spreadsheet to see how accurate it was. The results have me concerned. The spreadsheet arrived at TAS speeds of 96.8, 117.0, 137.5, and 158.0 respectively. Those numbers are all very close to my IAS. But I was at 5250′! My TAS should have been 110, 133, 155, and 177kts respectively. This means my ASI appears to be reading about 15Kts FAST. NOT GOOD!
So while munching on lunch I built a manometer and decided to test the ASI on the ground. I didn’t have a tall enough board to test all the way to 160kts. But I did 80, 100, 120, and 140 Kts, and got 4.6″, 6.8″, 9.8″ and 13.2″ H2O respectively. All are within a couple knots. So now I’m left with 3 possibilities. My static port is in a very low pressure area, the spreadsheet calculations are wrong, or the data is bad.”