AOA - Pros, Cons and Experiences

[Blue on Top]

4 minutes ago, carusoam said:

There is a sensorless AOA device that has been part of a clock and AI display...

Apparently the AOAi doesn’t work in Mooneys... and some aren’t getting installed properly elsewhere...

-a-

Unless complicated algorithms are used, attitude vs. flight path does not account for the air itself having vertical and gust components.

Why would AOAi be aircraft dependent? 

[carusoam]

14 minutes ago, Blue on Top said:

 

Why would AOAi be aircraft dependent? 

Some people were trying to install the device in the panel, but the panel was not aligned with the plane...

Some Mooney panels have a tilt in the top half....

Other Mooneys have angled section to improve visibility to the pilot...

So... the installation seemed to not have enough instructions for the installer to follow along???

Best regards,

-a-

[donkaye]

The David Rogers Report is a good read.  I've attached it here.  I calibrated my AOA at 1.3Vso at a known weight for the low end and the top of the white arc at the high end to minimize the error from the 2 point calibration.  Alpha Systems now has a 4 point calibration system, but I am happy with mine.  Garmin doesn't publicize their AOA much and I have read of people having some trouble with it, but it does normalize its computation where the Alpha Systems does not.  I am comfortable using mine for landings where my understanding is that it works best, maybe not so much under G loading, but Mark from Alpha Systems might disagree.

DeltaPAOA_wide_screen.pdf

[Mooneymite]

I just got done with recurrent training on the jet I fly at work.  Our jets are well equipped with very accurate AOAs which continuously display precise AOA information and drive the stall warnings and stick pushers.  Our AOA receive inputs from various sources, not just an AOA vane.  The system actually is, to a degree, predictive using accelerometer input to sense approaching load factor increase/decrease during maneuvering.

After explaining all this, you would think that we would fly our approaches using AOA.  We don't.  We fly just like the airlines (and mostvMooney owners)....indicated airspeed.  Most of us rarely even look at the AOA display.  It just isn't necessary, or even useful 99.9% of the time.

The training I just completed emphasized the AOA data, but it was during maneuvers to explore the flight envelope, to smooth recovery from unusual attitudes and upsets at FL450.

AOA is a great tool, no doubt about it, but really not all that useful for those of us who try to avoid exploring the envelope when we fly our Mooneys.  Really, the most useful AOA is the one already on our planes...the stall warning system.  I have no plans to equip my plane with a dedicated AOA.

[donkaye]

1 hour ago, Mooneymite said:

I just got done with recurrent training on the jet I fly at work.  Our jets are well equipped with very accurate AOAs which continuously display precise AOA information and drive the stall warnings and stick pushers.  Our AOA receive inputs from various sources, not just an AOA vane.  The system actually is, to a degree, predictive using accelerometer input to sense approaching load factor increase/decrease during maneuvering.

After explaining all this, you would think that we would fly our approaches using AOA.  We don't.  We fly just like the airlines (and mostvMooney owners)....indicated airspeed.  Most of us rarely even look at the AOA display.  It just isn't necessary, or even useful 99.9% of the time.

The training I just completed emphasized the AOA data, but it was during maneuvers to explore the flight envelope, to smooth recovery from unusual attitudes and upsets at FL450.

AOA is a great tool, no doubt about it, but really not all that useful for those of us who try to avoid exploring the envelope when we fly our Mooneys.  Really, the most useful AOA is the one already on our planes...the stall warning system.  I have no plans to equip my plane with a dedicated AOA.

In 1G unaccelerated flight on a stabilized approach flying the donut, as I mentioned before, comfortably enables me to fly the approach nearly 5 knots slower than I felt comfortable flying before installation of the Eagle AOA, and with no mental corrections for landing weight as I always did before.  Just one more tool in the utility bag to ease pilot load.  Necessary?  No.  Useful?  Yes.  But, then again, I will buy pretty much anything that I think makes flying safer, as my panel upgrade of a few years ago will attest.

[GeeBee]

The question about putting AOA on a FIKI airplane. Unless the sensor is part of the FIKI certification, it is likely it could provide erroneous data leading to the pilot possibly maneuvering the airplane to correct indications that are false. (Ask Ethiopian how that works out) How the sensor is certified for FIKI is up to the FAA and the manufacturer, but suffice to say, an unheated sensor on a FIKI airplane could lead to grief. We love to complain about the cost of the stall sensor for a FIKI airplane or even the need for a heated one, but the need is real and important.

I find most people that dismiss the value of AOA have never flown them. In line service in particular I have encountered several times where I set Vref and fly Vref+5 only to see the AOA indicating too high. A load audit usually reveals an error in the weight and balance numbers. Which points to the value of AOA. No matter what is happening, the critical angle of attack does not change for a given configuration.  I used AOA regularly when flying critical approaches coupled with HUD. You can really stick a landing on a short runway flying AOA which is why the Navy uses it for carrier landings.

[Blue on Top]

5 hours ago, donkaye said:

But, then again, I will buy pretty much anything that I think makes flying safer, ...

@donkaye  I'd like you to be my first customer with you being an influencer and all.  

[Blue on Top]

11 hours ago, GeeBee said:

1) Unless the sensor is part of the FIKI certification, it is likely it could provide erroneous data leading to the pilot possibly maneuvering the airplane to correct indications that are false.

2)We love to complain about the cost of the stall sensor for a FIKI airplane or even the need for a heated one, but the need is real and important.

1) How is the stall warning set on a FIKI-equipped Mooney?  Is it assumed that there is never any ice on the airplane?

2) I have heard this before.  What is the cost for heated and non-heated?

Thanks, Ron 

Edited December 10, 2019 by Blue on Top

[GeeBee]

Well I just came out of KABR after a blizzard the night before. Crossed a cold front that caused the blizzard, started icing despite a -16 temp, ran the TKS and the wing stayed pretty dang clean. Airplane is new to me but I would say, not an issue with the effectiveness of the TKS system compared to boots. It looked more like a hot wing to me.

 

[carusoam]

Great pirep Gee!
 

got a pic?  
 

South Dakota is pretty chilly this time of year, and windy to go with that...

Best regards,

-a-

[GeeBee]

I wish I did, I'll check with my buddy in the right seat to see if he grabbed one. I was a little busy dodging weather.

 

[Blue on Top]

All: My intent on MS is to state engineering facts, educate and learn from all of you.  If I offend anyone, it is definitely NOT my intent.  I've removed my earlier post, and I'll try to restate it better here.

To begin, let's delineate NORSEE equipment from certificated systems.  Certificated systems (those systems which are required by law to show compliance to the regulations) must be accurate and reliable. Stall warning is a good example.  The stall warning on a Mooney is required to be on the airplane and adjusted properly.  A NORSEE item is not required by law to be accurate, and (in this case) it cannot replace your certificated stall warning device. 

Talking only about certificated systems, AOA must be correct because it is used to show compliance to a regulation (stall warning), and in those airplanes with a stick pusher, as a stall barrier (FAA words).  In the case of the stick pusher, the stall speed is defined by when the pusher activates.  Now we're going to get a little controversial as there is a lot of misinformation being disseminated out there by some very important and knowledgeable people.

(again, certificated systems) AOA and airspeed are totally independent of each other, and this is where it gets a little tricky/confusing.  For those that have PDFs with airspeed and AOA on vertical tapes on the left side of the display, although they are displayed on the same scale (which happens to he airspeed), they are still independent.  In other words, if the airspeed stops (in the valid range), the AOA-driven color bands will still operate properly.  If the AOA transducer fails, the airspeed will still be valid.

There is so much more to say as an AOA system is complicated, the interaction with other systems makes it more complicated and if there are redundant systems of each of those systems it gets more complicated yet.

I really, really hope this helps clarify.  I love answering questions.   The more people know, the safer we will be. 

[John Mininger]

I am seriously thinking about installing an AV-20S.

Now Ron, I know this is not your favorite type of source for AOA data. But when one looks at the overall cost effectiveness of this instrument, along with all of the other information that it provides; why not? Is there a risk that it will give erroneous information?

https://www.youtube.com/watch?v=M8p3ncDYFiI

John

[tmo]

I'm pretty sure the AV-20S is not a reliable AoA indicator...  Calling @0TreeLemur from the other (backup AI) thread.

[0TreeLemur]

3 minutes ago, tmo said:

I'm pretty sure the AV-20S is not a reliable AoA indicator...  Calling @0TreeLemur from the other (backup AI) thread.

Yes, I had an experience during IFR training in March flying through moderate rain.  My pitot-tube vent became partly plugged with water causing transients in the pitot-static system, which caused the AV-20S AOA sensor to freak out and start telling me that I had approached or exceeded what it thought was the critical AOA.   Very distracting- flashing brightly bad AOA data.  In reality my static instruments were extremely happy- nothing had changed and I was in a stabilized descent with low turbulence, the altimeter and VSI both stably indicating 500 fpm descent.

After that I contacted Aerovonics, the original mfgr. of the AV-20S.   I was told that the AOA sensor is uncalibratable in the Mooney airframe, and that I should disable it, which I did.

I bought the AV-20S for (1) timer, (2), backup MEMS attitude indicator, and (3) TAS indication.   After setting the temperature trim to calibrate the thermistor, it typically gives TAS of 150 kts (I wish) when according to the Garmin 430W it is more like 143 kts.   I recently contacted uVonics regarding the apparent error in the TAS indication and they are working on improvements.  I've not yet been informed of any new firmware being released.

The AV-20S is (IMHO) a good timer.  It gives engine run time as indicated by V>13.4V, and flight time according to TAS>40 kt.   It includes two user-selectable count up/count-down timers that are useful.  I most often use the flight time indication to remind me when to switch tanks.   The backup AI is a very nice feature.   Every time I compare it against my vacuum AI it agrees.   When flying actual IFR in turbulence I'll often turn it to display the attitude indication to just have a confirmation that my brain is wrong.

The AV-20S is not a great AOA sensor.  Don't buy it for that.  I could never calibrate it and was told by Aerovonics to give up trying.

As @Hank educated me- it is a good clock with excellent 'Lagniappe".

Good luck.

Fred

[gsxrpilot]

3 hours ago, John Mininger said:

I am seriously thinking about installing an AV-20S.

Now Ron, I know this is not your favorite type of source for AOA data. But when one looks at the overall cost effectiveness of this instrument, along with all of the other information that it provides; why not? Is there a risk that it will give erroneous information?

https://www.youtube.com/watch?v=M8p3ncDYFiI

John

I have the AV-20S in my panel as well and have never been able to get the AOA calibrated. 

I'd be willing to sell mine. I just don't find it very useful.

[John Mininger]

Thanks for the info guys.

I think this kind of backs up Ron's critique of NORSEE.

[Blue on Top]

7 hours ago, John Mininger said:

Now Ron, I know this is not your favorite type of source for AOA data. Is there a risk that it will give erroneous information?

John

@John Mininger  I will not address company specific instruments.  Plus, on this one in particular, I know more background information.

For probe-less AOA sensors, the device compares aircraft attitude to flight path (GPS).  Please note that flight path is NOT equal and opposite to relative wind as the air itself is moving (turbulence, bumps, up and down movement and plus and minus gusts).  Now let's take a quick look at attitude and flight path data.  The new attitude indicators use inexpensive accelerometers to measure attitude, but they are made better with other sources and filters (hence the reason G-meters, GPS, pitot and static are added).  Through a Kamen filter, attitude is made better.  GPS (at best) is delayed 300 ms (0.3 seconds) … but that timing fluctuates.  Now, how long does it take the computer to process these inputs, filters, GPS and (if applicable) data busses?  Is the GPS data (flight path) being compared to the attitude data at the same point in time?

If a product makes you a better pilot, I am for it.

[Blue on Top]

2 hours ago, John Mininger said:

I think this kind of backs up Ron's critique of NORSEE.

Please don't misunderstand me, NORSEE has some useful purposes … and I hope the new AIs are just one BIG one of them.  As has been pointed out by others @gsxrpilot @tmo @0TreeLemur there are misinformation and failure modes of some of these devices that are not directly and obviously intuitive.  On a funny note (and all of these are only funny because no one is getting hurt), the first time I got to evaluate a new attitude indicator, it kept red Xing.  After hours of frustration and conversations with the OEM, we came to the conclusion that the device had concluded that my pitot tube was icing over … the unit was setting on my desk.  Not intuitive.