I'm curious about AOA indicators. I know lots of guys poo-poo them while some that have them like them a lot. My G3X will support an AOA probe with a total investment of $199. It could be a fun experiment to try one out to make up my own mind. So here's the big question. Has anyone here installed an AOA on a slat wing?
AOA on a Slat Wing
- Thread starter stewartb
- Start date
Interesting thought. Question I would have is what range these sensors have since they are designed for a straight wing and your slatted wing is able to achieve a much greater AOA?
If an AOA probe is engineered to be accurate up to 10 to 14°, how is it's calibration in what would normally be beyond a deep stall. Would it be repeatable and useful information?
If an AOA probe is engineered to be accurate up to 10 to 14°, how is it's calibration in what would normally be beyond a deep stall. Would it be repeatable and useful information?
mike mcs repair
Registered User
chugiak AK
CamTom12
Registered User
Huntsville, AL
Steve Pierce
BENEFACTOR
Graham, TX
I don't know how the G3X works but have seen the box in the wing attached to the pitot/static system in the Carbon Cub FX2and 3. Way better than a stall warning horn. As you get close to full stall the beeps get closer together and were dead on accurate. Interested in what you find out.
The ADHRS/air data computer is the heart of all G3X systems. It comes with 3 air ports. Pitot and static, and AOA in the middle. Most guys like me leave a plug in the AOA port. The GAP-26 is the Garmin probe for the AOA. It provides Pitot and AOA pressure lines. Static has to come from a separate source. I don't know how the probe works but apparently it provides differential pressure to the GSU which computes AOA and displays it on the GDU screen. The probe is $199. Everything else is already in place. I'd like to see how an AOA instrument works and this would be easy to set up. I'd like to see for myself if AOA indicators have a place in my airplanes. The Cessna may be a better platform for AOA but the Cub has most of the components already installed.
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mike mcs repair
Registered User
chugiak AK
You’ll need a couple fittings. Think aoa is currently teed into static line
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Gordon Misch
MEMBER
Toledo, Wa (KTDO)
I wonder if the probe needs to be out front of, or at least close to the leading edge, to be accurate or at least consistent?
mvivion
SPONSOR
Bozeman,MT
I think that's the single biggest challenge to mounting a sensor on or close to the wing. The wing influences the airflow out at a considerable distance from the leading edge, which is why the test pitots you see extend well forward of the wing.
Jerry Burr posted some photos illustrating this with tufts on this forum a long time ago. Really nice illustration of air moving around the wing leading edge.
MTV
Gordon Misch
MEMBER
Toledo, Wa (KTDO)
I don't think accuracy (true AOA) is very important. But it seems that consistently and correctly indicating near-stall conditions with varying flap and slat deployments would be important - i.e. the only reason for having the system? On the other hand, maybe calibrating it only for full-flap operation would do the desired job.
Steve Pierce
BENEFACTOR
Graham, TX
I will pay closer attention when the FX3 gets here and post some pictures. I do know that it worked well on the standard wing. I had to ask the dealer about the beeping. I was use to the stall warning going off well before the stal but the AOA were gradual beeps that got closer together as I got closer to the full stall. Flying it around some different back country strips in Arkansas I realized it was pretty accurate.
Since the Garmin is not a true AOA but a "Lift reserve indicator". It requires a low end and high end calibration. As such it matters little what kind of wing you have and since your slat deployment is automatic you simply calibrate it at the low end when the slats have deployed anyway.
mike mcs repair
Registered User
chugiak AK
so you will need to use the built in W&B on the g3x, since it sounds like it's using that in its calculations....?
Jonnyo
Registered User
Fairbanks, Ak
Probably not what Stewartb was heading for, but I mounted a 4 inch digital level on the cabin wall, while I was experimenting. A hand mirror on the instrument panel made it so I didn't have to look sideways. A GoPro recorded the stall angle and speed for observation later.
Dave Calkins
Registered User
Anchorage, Alaska
I have done the same thing that Jonnyo describes.
Amazing what a slatted wing can do. Like 45 degrees noseup, no problem. And with gobs of power, you are hanging on the prop, even hovering, as witnessed by some when I flew MikeO’s Redneck Cub.
Obviously, we are way,way behind the power curve in this regime.
Its nothing like an unslatted wing and I wonder how the AOA systems handle this. A reduction in power has the airplane descending, but not stalled.
Thanks for sharing with us SB, this is very interesting
Amazing what a slatted wing can do. Like 45 degrees noseup, no problem. And with gobs of power, you are hanging on the prop, even hovering, as witnessed by some when I flew MikeO’s Redneck Cub.
Obviously, we are way,way behind the power curve in this regime.
Its nothing like an unslatted wing and I wonder how the AOA systems handle this. A reduction in power has the airplane descending, but not stalled.
Thanks for sharing with us SB, this is very interesting
I think this is the weekend I'll finally install my GAP26 AOA probe. A G3X's ADHRS has a port for AOA so all I need to do is add one tube between the probe and ADHRS and connect the pitot line to the new probe. No wiring required. To set it up I need to set the speed where the AOA indicator comes to life on the screen, probably 30 or 35 mph, then set the speed where I want it to go from green to yellow for the alert stage, then tell the G3X that I'll doing a stall series where it sets its own critical AOA. Pretty simple. Instructions say the probe needs to be +/- 5* of chord and it appears that makes the underside of my leading edges a perfect position to mount it. Measure twice, cut once, right? 
Why an AOA? The G3X Touch airspeed tape doesn't light up until 20mph. My plane can fly slower than that. Not a lot, but having a visual and audible indicator of stall in the absence of an airspeed indicator doesn't seem like a bad idea.
Why an AOA? The G3X Touch airspeed tape doesn't light up until 20mph. My plane can fly slower than that. Not a lot, but having a visual and audible indicator of stall in the absence of an airspeed indicator doesn't seem like a bad idea.
mike mcs repair
Registered User
chugiak AK
Has anyone complained to garmin and asked for a software fix for below 20mph?
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mike mcs repair
Registered User
chugiak AK
Another thread here was complaining they don’t go under 20....
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Full flaps power-off. I want to try a couple of other configurations, too, but with the way my summer went last year I didn’t get to it.
The power-off instructions by Garmin triggered a long discussion about AOA with my rocket scientist buddy. Is AOA at the stall different with partial power on? I want to experiment with that when I get back to flying.
The power-off instructions by Garmin triggered a long discussion about AOA with my rocket scientist buddy. Is AOA at the stall different with partial power on? I want to experiment with that when I get back to flying.
How many degrees of flaps do you have?
I have Keller’s flaps like you, and I set them 15, 35, 50 and 60 degrees (i have four notches).
I am really new with my SuperCub, I only have three since we finished last week (I am breaking the engine) and I did not try -so far- more than the second notch of flaps (35 degree).
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AOA is the angle of the wing compared to the relative wind. With power, your AOA doesn’t change, but the relative wind does.
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