AoA Calibration

[midlifeflyer]

A friend's new to him SportCruiser with dual EFIS HDX. AoA indicator had never been calibrated. We attempted calibration yesterday. Following the on-screen directions (pic), we did three stalls. Power off no flaps, power off full flaps, and a departure Stall. All three recorded by the system when we pressed the "Stall" button after full recovery. Then we pressed "save" and exited.

Before calibration the on-screen AoA indicator was blank with the "Cal?" Note. Once in calibration mode, the on-screen AoA indicator lit up like a Christmas tree. After saving and exiting, the AoA indicator went back to its blank "Cal?" mode.

We did the whole thing twice. Same result. Any ideas?

 

[Bsquared]

Have you confirmed that the pitot tube itself is AOA capable and is connected to the ADAHRS unit. That may be why the original owned never calibrated it. You can check this by removing an access cover near either the pitot tube or the ADAHRS unit t see if there are 2 separate tubes running between them.

 

[Dynon]

That's odd. Try it with just one power off stall. Does that make a difference?

 

[midlifeflyer]

That's odd. Try it with just one power off stall. Does that make a difference?

we tried it with three and then with two.

@Bsquared asks an interesting question. The SportCruiser maintenance manual talks about an "optional" vane-type stall warning system which is definitely not on this airplane. Basically, without the Dynon AoA there is simply no stall warning system

That's what made me think it "had to be" part of the Dynon. but I guess it's conceivable (I'm new to this level of detail in LSAs) there is no stall warning at all. But in that case, I'm surprised the HDX showed the indicator, entered calibration mode, and "accepted" stalls instead of indicating something like, "unable to detect." Does that make sense?

I'll have to check that out, @Bsquared. Thank you.

 

[midlifeflyer]

Have you confirmed that the pitot tube itself is AOA capable and is connected to the ADAHRS unit. That may be why the original owned never calibrated it. You can check this by removing an access cover near either the pitot tube or the ADAHRS unit t see if there are 2 separate tubes running between them.

it looks like that's the answer.

SportCruiser aircraft were built with a stall warning vane system as an option. I don't see anything about a dual pribe sensor pitot installation in the maintenance logs. @Dynon, when was AoA capability added to Skyview?

 

[jakej]

FYI - always was part of the Dynon system & with the ‘legacy’ units too.

 

[Stevec]

we tried it with three and then with two.

@Bsquared asks an interesting question. The SportCruiser maintenance manual talks about an "optional" vane-type stall warning system which is definitely not on this airplane. Basically, without the Dynon AoA there is simply no stall warning system

That's what made me think it "had to be" part of the Dynon. but I guess it's conceivable (I'm new to this level of detail in LSAs) there is no stall warning at all. But in that case, I'm surprised the HDX showed the indicator, entered calibration mode, and "accepted" stalls instead of indicating something like, "unable to detect." Does that make sense?

I'll have to check that out, @Bsquared. Thank you.

When we were doing the flight testing on an RV12 we went through the calibration process which appeared to be working however it would not retain the result. Investigation revealed the tubing from the probe was pinched and blocking the air. All went well once the tube was freed up.
One other point that we discovered after searching through a number of past posts was that the calibration only remembers the data from the last stall so we were not sure why the instructions tell you to carry out a number of stalls. If this is incorrect I am sure Don will let us know.

 

[jakej]

I updated post # 6 to make it clearer .

 

[Curtlyman]

A friend's new to him SportCruiser with dual EFIS HDX. AoA indicator had never been calibrated. We attempted calibration yesterday. Following the on-screen directions (pic), we did three stalls. Power off no flaps, power off full flaps, and a departure Stall. All three recorded by the system when we pressed the "Stall" button after full recovery. Then we pressed "save" and exited.

Before calibration the on-screen AoA indicator was blank with the "Cal?" Note. Once in calibration mode, the on-screen AoA indicator lit up like a Christmas tree. After saving and exiting, the AoA indicator went back to its blank "Cal?" mode.

We did the whole thing twice. Same result. Any ideas?


View attachment 5046

I agree with midlifeflier. The Sportcruiser came with a leading edge vane style stall indicator and a pitot tube that was not compatible with the Dynon AoA system. I own a 2018 SC and about to install Dynons heated dual probe AoA pitot tube. The original pitot tube does not have the capability to support this. What strikes me as odd is why isn’t your stall indicator working and who signed off on the annual and pre buy inspection?

 

[M20Driver]

That's odd. Try it with just one power off stall. Does that make a difference?

Does it indeed only save data from one stall? I've calibrated mine a few times now with no changes.

 

[Rhino]

I agree with midlifeflier. The Sportcruiser came with a leading edge vane style stall indicator and a pitot tube that was not compatible with the Dynon AoA system. I own a 2018 SC and about to install Dynons heated dual probe AoA pitot tube. The original pitot tube does not have the capability to support this. What strikes me as odd is why isn’t your stall indicator working and who signed off on the annual and pre buy inspection?

Unless the type certificate data specifies otherwise, not even certificated aircraft require aural or other indicator warning as long as the aircraft itself warns of a stall through "inherent aerodynamic qualities" (FAR 23.207). Some aircraft do it simply by nature of their design, and some use devices like stall strips. Stall warning isn't required at all on homebuilts. Not sure of the exact rule for ELSA, but it appears the Sportcruiser is perfectly legal even without the optional paddle vane, so there doesn't appear to be any reason it couldn't have been signed off. I personally wouldn't want to fly without one though.

 

[airguy]

The Dynon software has always had the inherent ability for AOA monitoring and stall alerts - but it also requires an AOA pitot probe, which is optional. If the aircraft does not have a dual-port AOA pitot probe, you can't make use of the AOA function.

 

[midlifeflyer]

I agree with midlifeflier. The Sportcruiser came with a leading edge vane style stall indicator and a pitot tube that was not compatible with the Dynon AoA system. I own a 2018 SC and about to install Dynons heated dual probe AoA pitot tube. The original pitot tube does not have the capability to support this. What strikes me as odd is why isn’t your stall indicator working and who signed off on the annual and pre buy inspection?

It's not that it's not working, there simply isn't a vane stall indicator. The wings are flush. I thought that odd but the maintenance manual says it was optional.

 

[midlifeflyer]

I personally wouldn't want to fly without one though.

The funny part of all this is that for a long time I never even noticed it was missing despite doing and teaching approach, departure, and falling leaf stalls. Plenty of "inherent aerodynamic qualities" warning if the impending stall, as @Rhino mentioned.

 

[Dynon]

Does it indeed only save data from one stall? I've calibrated mine a few times now with no changes.

It's not that it remembers just "one stall", but that the calibration is ultimately railed by the deepest stall as the AOA probe sees it. IE, if you do a stall clean and a stall completely dirty, they might look relatively the same at the AOA probe, but more likely the one where you have your flaps out will allow a higher AOA before it goes critical. So the red zone will be tied to that deeper stall. That make sense?

 

[airguy]

And just to muddy the waters a bit further - you can "cheat" the calibration to a higher airspeed if you like - to give you more warning time. When I was teaching my uncle to fly my 9A, I went out and calibrated the AOA alert a few knots high by intentionally "breaking" the stall by pushing the stick about 3-4 knots before the actual stall. I taught the algorithm the new, false, higher speed stall alert so that my uncle would have just a few knots of cushion on the AOA alert for learning the landings.

And that way I got to keep my wheel fairings.

 

[Stevec]

Thanks Don that clears it up nicely.

 

[andresmith76]

It's not that it remembers just "one stall", but that the calibration is ultimately railed by the deepest stall as the AOA probe sees it. IE, if you do a stall clean and a stall completely dirty, they might look relatively the same at the AOA probe, but more likely the one where you have your flaps out will allow a higher AOA before it goes critical. So the red zone will be tied to that deeper stall.

Don -

I don't want the AoA indicator going into the RED zone & start beeping when I'm on final, just above the runway with full flaps, starting my flair - that is when I expect the plane to stall. I want the AoA system to alert me when I'm in a tight turn or turbulence and I'm about to stall when I don't expect it. How do I calibrate for that?

 

[airguy]

There's no way for the airplane to tell the difference. It only knows an approaching stall situation.

Don -

I don't want the AoA indicator going into the RED zone & start beeping when I'm on final, just above the runway with full flaps, starting my flair - that is when I expect the plane to stall. I want the AoA system to alert me when I'm in a tight turn or turbulence and I'm about to stall when I don't expect it. How do I calibrate for tha

 

[andresmith76]

There's no way for the airplane to tell the difference. It only knows an approaching stall situation.

According to Dynon's earlier post, "the calibration is ultimately railed by the deepest stall as the AOA probe sees it" - "the red zone will be tied to that deeper stall". So there are variations on stall warnings that depend on how and where you calibrate. As stated, I'm wanting to know how to calibrate to warn me of an impending stall while maneuvering when I least expect it.

Also - what's with the "oscillate the aircraft + or - 5 degrees 4 times" procedure before performing stall? What does that do?