David-aviator
Well Known Member
I had an inspiration today to attempt measuring stall AOA .
The basic premise is that wing incidence is set to a level longeron and that incidence represents zero AOA. If that is not true, the data is flawed from the beginning and useless.
What I did was take off with a Smart Level to measure the angle of the longeron when the airplane stalls. That was easier said than done. Beside clearing the area, the level had to be held in position on the longeron while trying to keep the airplane straight and level during the stall. There is a freeze feature with level so the button was pushed when the stall occurred.
The first attempt resulted in a reading of 10.4?. That did not seem right and later at lunch with some guys, including a retired F-18 test pilot, it was noted that if there was any drift down, that angle had to be added to the reading. The idea of measuring the angle at the longeron was valid but only if the airplane was level and not sinking.
Later, on the way home, I tried it again. This time I went to great effort to keep the V/V at zero going into the stall. I almost succeeded but the Dynon still said 100 fpm. The longeron measurement at stall was 12.1?. I tried one with 20? flaps it came in at 8.8?. To do this right, I really need a co-pilot to read the level while I concentrate on keeping sink rate at zero.
I took a few measurements at a set IAS with the altitude hold engaged. The trend with increasing speed obviously would result in a negative AOA. I'm not sure what to make of that.
130 KIAS = .3?
110 KIAS = 1.6?
100 KIAS = 2.4?
90 KIAS = 2.7?
80 KIAS = 4.0?
70 KIAS = 5.5?
Not sure what all this is worth but it is a diversion from searching for enemy Cessnas and Pipers.
The basic premise is that wing incidence is set to a level longeron and that incidence represents zero AOA. If that is not true, the data is flawed from the beginning and useless.
What I did was take off with a Smart Level to measure the angle of the longeron when the airplane stalls. That was easier said than done. Beside clearing the area, the level had to be held in position on the longeron while trying to keep the airplane straight and level during the stall. There is a freeze feature with level so the button was pushed when the stall occurred.
The first attempt resulted in a reading of 10.4?. That did not seem right and later at lunch with some guys, including a retired F-18 test pilot, it was noted that if there was any drift down, that angle had to be added to the reading. The idea of measuring the angle at the longeron was valid but only if the airplane was level and not sinking.
Later, on the way home, I tried it again. This time I went to great effort to keep the V/V at zero going into the stall. I almost succeeded but the Dynon still said 100 fpm. The longeron measurement at stall was 12.1?. I tried one with 20? flaps it came in at 8.8?. To do this right, I really need a co-pilot to read the level while I concentrate on keeping sink rate at zero.
I took a few measurements at a set IAS with the altitude hold engaged. The trend with increasing speed obviously would result in a negative AOA. I'm not sure what to make of that.
130 KIAS = .3?
110 KIAS = 1.6?
100 KIAS = 2.4?
90 KIAS = 2.7?
80 KIAS = 4.0?
70 KIAS = 5.5?
Not sure what all this is worth but it is a diversion from searching for enemy Cessnas and Pipers.