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RV-12 AOA systems

bbaggerman

bbaggerman

Active Member
I am interested in retrofitting an AOA system onto my RV-12. AOA systems that I am familiar with all have an external pitot-like probe. But the RV-12 KIA shows fabricating an AOA port simply by installing the same type of port as the static port (appropriate pull rivet with 1/4" tubing glued on) at a specific location under the wing near the stall warning vane.

Does anyone have any experience with this kind of AOA port? What kind of AOA system(s) does it feed? Has it worked well for you?

I have a conventional pitot on my -12 rather than the thing that sticks out of the spinner so a pitot-like AOA probe probably makes more sense for me but the wing rivet thing intrigues me.
 
I installed a rivet AOA port on my RV6 connected to a Dynon system and it has worked well. I found somewhere that the ideal angle to the airflow was about 45 degrees although I can remember the exact figure. I then leveled the aircraft and ran a digital level up the leading edge until the level formed a tangent at that angle. That’s where I put the rivet. It seems to have been the right position.
 
Works very well. Used the rivet and a hose to the Dynon ADHRS module in the back. You have to do some stalls to calibrate the system.
Before I had the AOA system installed I flew fixed speeds. Since I use the AOA system I fly slower resulting in a shorter flare and landing.

First flight with the system (still flying too fast);

AOA Dynon Skyview
 
Gagarin737 said:
Works very well. Used the rivet and a hose to the Dynon ADHRS module in the back. You have to do some stalls to calibrate the system.
Before I had the AOA system installed I flew fixed speeds. Since I use the AOA system I fly slower resulting in a shorter flare and landing.

First flight with the system (still flying too fast);

AOA Dynon Skyview
Click to expand...

That video is Private.
 
The AOA can be computed from the data already available to the Dynon and without an external sensor. If I recall correctly, that was a normal feature on my GRT on my 7A.

I wonder why Dynon chooses not to do that.

This is from the user manual available on the GRT site

"Angle-of-Attack can also be calculated by the EFIS by combining a variety of sensor data. AOA calculated in this manner has the benefit that does not require any dedicated hardware. The drawbacks are that the calculated AOA is dependent on proper functioning of the pitot/static and pitch attitude data. Also, the accuracy of the calculated AOA degrades when flying through rising or descending air."

GRT added it after I pointed it out, long ago and far away. It was on the EFIS that I had. My AOA was an entirely separate, non-electric round instrument. They agreed to a reasonable level of precision.
 
hevansrv7a said:
The AOA can be computed from the data already available to the Dynon and without an external sensor. If I recall correctly, that was a normal feature on my GRT on my 7A.

I wonder why Dynon chooses not to do that.
.
Click to expand...

GRT EFIs's of a certain vintage do (did) contain software to calculate AOA from the EFIS data, without any direct measurement. Current EFIS's use a second angled ram air data input, just like Dynon.

I have one of the direct-calculation GRT models, as well as a Dynon D6, and have directly compared the 2 AOA sensors. On a slow approach to a stall, like a typical landing flare, they agree well. But on a rapid approach to a stall - like maybe a too aggressive pull up from a dive - the GRT indicator lags behind the Dynon by a second or two. The error bar on the required rapidly changing data is just too large for accurate immediate results.
 
I have the Dynon D-180 with the AOA input connected to the static type rivet
port on the wing. I set the AOA to start beeping slowly at about 60 knots
airspeed. It serves as an audio on-speed indicator so that I can keep my eyes
focused on the runway. The closer the wing gets to stall angle-of-attack, the
faster it beeps until it is a steady tone. It doesn't matter what kind of airspeed
probe that you have. The EFIS compares the pressure difference between the
airspeed port and the AOA port. After installation, the AOA needs to be calibrated in flight.
 
Mich48041 said:
I have the Dynon D-180 with the AOA input connected to the static type rivet
port on the wing. I set the AOA to start beeping slowly at about 60 knots
airspeed. It serves as an audio on-speed indicator so that I can keep my eyes
focused on the runway. The closer the wing gets to stall angle-of-attack, the
faster it beeps until it is a steady tone. It doesn't matter what kind of airspeed
probe that you have. The EFIS compares the pressure difference between the
airspeed port and the AOA port. After installation, the AOA needs to be calibrated in flight.
Click to expand...

Joe, I have the same set up but no beeping. I didn't think it was available on the D180? I would be interested to know what settings you are using get the beep. Mine provides an audible "stall, stall" but it isn't progressive.

Thanks in advance.

Jack
 
I am involved in the FlyONSPEED project. My thought was after installing an appropriate AOA port I would plumb up to both the Dynon AOA system and the FlyONSPEED box for comparison.

The FlyONSPEED box takes flap position into account. It seems some other systems you guys have experience don't use flap position in the AOA calculation. I wonder how they get around that.
 
bbaggerman said:
The FlyONSPEED box takes flap position into account. It seems some other systems you guys have experience don't use flap position in the AOA calculation. I wonder how they get around that.
Click to expand...

Maybe because they don't calculate AOA, but measure it instead? Based on the airflow over the leading edge (compared to the pitot input), which would already be effected by flap position.
 
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