AOA - Pros, Cons and Experiences

[bonal]

And Paul as I said if I were an IFR pilot and flew the kind of missions you are able. I would be on the other side of that coin. I think horses are beautiful animals but I've no desire to ride one. Sorry if I pissed you off not my intention but it seems like people don't accept my version of the passion for flight as its not the same as theirs. I do have a garmin 296 and like the information it provides. Everyone wants to see the costs associated with flying and owning an airplane go down but all we talk about is this upgrade and that upgrade shoot most of your panels are worth twice my whole plane. And I celebrate all you are able to do with your awesome  Mooney's. 

[bonal]

23 minutes ago, GeeBee said:

The attitude of an aircraft has zero relationship to its angle of attack.

Poor choice of words my bad not what I meant. I guess I really had no business responding to this thread. It was a rainy day and I was bored. Sorry everyone.

im out

Edited December 8, 2019 by bonal

[Bob_Belville]

 I bought my CYA 1000 aoa indicator from Aircraftspruce for $625. Will be installed bei next Annual.

I’ve had the CYA installed for several years. It is a flying wing giving very useful information on relative AOA. Calibration is pretty simple. The top of the 10 light stack is usually set to approximately Vy clean, ~90 kias for my M20E. The bottom of the lights is set by flying in landing configuration, gear down, full flaps and plane at stall or near stall.

I find it most useful when setting speed on final on short field.


Sent from my iPad using Tapatalk

[Bob_Belville]

 I bought my CYA 1000 aoa indicator from Aircraftspruce for $625. Will be installed bei next Annual.

I’ve had the CYA installed for several years. It is a flying wing giving very useful information on relative AOA. Calibration is pretty simple. The top of the 10 light stack is usually set to approximately Vy clean, ~90 kias for my M20E. The bottom of the lights is set by flying in landing configuration, gear down, full flaps and plane at stall or near stall.

I find it most useful when setting speed on final on short field.


Sent from my iPad using Tapatalk

[Andy95W]

5 hours ago, gsxrpilot said:

 

No one NEEDS these devices, but neither do we NEED autopilots, radios, or even airplanes. But they are nice to have and do serve a very useful purpose.

 

⬆️⬆️⬆️

IMO, this is the best summation of this entire thread as well as the previous ones where folks got so testy with each other.

[Blue on Top]

6 hours ago, GeeBee said:

It is still dependent on the actual dynamic pressure in both direction and velocity which makes it a true AOA as opposed to LRIs which compare dynamic to static and thus are derived values. Regardless if the vane sticks out horizontally from the fuselage or is a on the leading edge it directly measures AOA without deriving AOA from inferred pressure differentials. The proof is I can walk up to both vane types on the ground, move them with my hand, and the AOA gauge will move. You cannot do that with LRIs.

AOA can be derived from an LRI type unit … Garmin does it in a sneaky way.  "Off angle" differential pressure divided by Qc (or pitot - static or airspeed differential pressure) is proportional to AOA.  GeeBee is correct in saying it has to be derived … through an ADC (Air Data Computer).  Harco (Eclipse jets) do this and so does the Goodrich (United Technologies) Smart Probes, but they are very expensive … even for business jets.

The SafeFlight system is measuring force on the flipper.  The stall warning works because it is a single point value.  When the stagnation point (where airflow first contacts the wing) goes aft of the vane, the forward airflow pushes the flipper up into the contact points, and you hear a tone (stall warning).  On the "similar" AOA unit it measures force on the flipper.  (making up numbers) At an AOA of 10 degrees and 70 knots, the flipper has X oz. of force on it.  If I keep AOA constant and increase airspeed to 140 knots (yes, I'm now pulling 4Gs), the flipper will have 4X oz. of force on it.  The displayed AOA will be converted/calculated as significantly less (guessing near 2 degrees).  In addition and in turbulence (which is a change in AOA) and knowing that the flipper is not mass balanced, it will record vertical loads as changes in AOA.  Vanes are mass balanced so they don't do this. 

[brndiar]

9 hours ago, GeeBee said:

Most GA AOA systems are not true AOA systems, but lift reserve indicators. That is why you have to calibrate them with test flights. A true AOA system uses a flying vane to measure true AOA. I have flown both and while a properly calibrated LRI functions just fine, a true AOA is so refined if you fly into rain, in level flight, you can see the AOA increase. The only true AOA for GA I know of is the SafeFlight system. That all said, I believe LRI units are a real plus and a wise investment.

 

CYA 1000 is not "true" aoa Sustem? By the way cost only $625. 

[Blue on Top]

8 hours ago, brndiar said:

CYA 1000 is not "true" aoa Sustem? By the way cost only $625. 

CYA 1000 is a true AOA.  ALL AOA systems measure local AOA.  I believe what brndiar is saying is that it is not converted to aircraft AOA.  I believe the CYA is calibrated at two points.  Certificated AOA (typically business jets and up) is corrected and calibrated for each flap setting, icing, etc.  CYA works well … if toward the front of the wing where local AOA actually changes.

[slowflyin]

I’ve owned and flown both the CYA and Alpha systems.  Both have pros and cons.
 

 My first was the CYA installed on my F.   It was affordable, easy to install and worked very well.  I always liked that it had a vane  as opposed to measuring pressure differential.  It looked like a “true, jet like” AOA.   My only gripes were stability and indicator location.   On bumpy days it was all over the place.  Still very usable but took some interpretation and practice.  I found myself using it to identify the correct airspeed for weight and conditions then flying the ASI.  Because it was next to the ASI this seemed very natural. 
 

My second is the Alpha with the heads up display.  It was more expensive and more difficult to install.   I find it to be more stable and the heads up is a game changer. On short final, second to my rear end, it’s the indicator I use.  Mark with AlPHA talked me into the heads up and I have zero buyers remorse.  For me, having it above the glare shield makes all the difference.   For that reason I prefer the Alpha and feel the price delta is well worth it.  
 

If I had mounted the CYA above the glare shield, front and center view, I’m certain I would have liked and utilized it more.  

[gsxrpilot]

@bonal not pissed off in the least. Just pointing out the other side of the coin. We undoubtedly agree on much more than we disagree on. And I'm sure we aren't as far apart on this topic as it might seem. 

I took my daughter and another young teacher up for a ride this morning. Going no where, just boring holes in the sky and had a wonderful time. Later this afternoon we'll likely try to fly home to Denver, very carefully and picking our way around the weather.

Lots of wonderful ways we get to use our airplanes. So very privileged in so many ways.

[DonMuncy]

 

38 minutes ago, gsxrpilot said:

 Later this afternoon we'll likely try to fly home to Denver, very carefully and picking our way around the weather.

 

High overcast at Castle Rock at this moment.

[donkaye]

56 minutes ago, gsxrpilot said:

@bonal not pissed off in the least. Just pointing out the other side of the coin. We undoubtedly agree on much more than we disagree on. And I'm sure we aren't as far apart on this topic as it might seem. 

I took my daughter and another young teacher up for a ride this morning. Going no where, just boring holes in the sky and had a wonderful time. Later this afternoon we'll likely try to fly home to Denver, very carefully and picking our way around the weather.

Lots of wonderful ways we get to use our airplanes. So very privileged in so many ways.

Not related at all to this thread, but how do you get the @bonal to show up as you did?   IOW how do you get this function to work on MS.  I've seen people use this often, but haven't found instructions on its use.

I do have the Alpha Systems AOA with HUD, and it shaved nearly 5 knots off of the more conservative speeds I teach in the Mooneys when exact weight and other important conditions on landing  are not known.

[PT20J]

@donkaye Just type the @ followed by a the first few letters of the username and a drop down list will appear with the closest matches to select from. 

What approach speeds do you teach for the J?

Skip

[PT20J]

I’m curious what experience others have with the Aspen synthesized AOA indicator. Does it seem accurate? Do you use it?

I have a EFD 1000 (PFD only) with AOA installed by the previous owner. Mine seems to be out of calibration as I’m deep into the crosshatch at 65 KIAS, 2400 lb., full flaps in a M20J which seems to provide a reasonable compromise between too much float and enough reserve for a good flare. Also the display is so small that I find it hard to read at a glance. 
 

Skip

[donkaye]

1 hour ago, PT20J said:

@donkaye Just type the @ followed by a the first few letters of the username and a drop down list will appear with the closest matches to select from. 

What approach speeds do you teach for the J?

Skip

70 knots nominally on final.  Depending on float, I might adjust it lower after a couple of times around the pattern.

[donkaye]

1 hour ago, PT20J said:

@donkaye Just type the @ followed by a the first few letters of the username and a drop down list will appear with the closest matches to select from. 

What approach speeds do you teach for the J?

Skip

Thanks, Skip.

[GeeBee]

Any LRI is only as accurate as you calibrate through test flying. In a true AOA system zero is referenced to the chord line by accurate measurement. However this can be messed up if for instance zero is set then the angle of incidence on the wing is tweeked. Accurate installation however makes a true AOA operate without the need for flight calibration. Once zero is known for the given aircraft and the assembly is consistent the AOA installation has is easy. 

[GeeBee]

16 hours ago, brndiar said:

CYA 1000 is not "true" aoa Sustem? By the way cost only $625. 

I did not say it was not a true AOA. I said "most", and I said the ones I know of, which I am not familiar with the CYA system. It appears to be a true AOA although the nature and method of approval and installation requires you to calibrate in flight test and not against the actual wing chord. I would also not install that on a FIKI airplane.

 

[Blue on Top]

… and this is one of the reasons this thread was started … education.

Vanes accurately measure LOCAL AOA, period.  They can be "calibrated" to indicate when AOA is at 1.3Vstall (all weights, etc.; not all configurations, in icing, etc … unless those are inputs into an AOA computer).  They can be calibrated to: produce aircraft AOA, produce correct values and margins in ALL configurations … if those parameters are input (i.e. flap positions, speed brake position (if they affect stall AOA), icing conditions, etc.)

"LRIs" should be broken into at least a couple categories: differential pressure and Cp measurement.  Differential pressure is NOT AOA nor is it  directly related to AOA … unless Qc (airspeed) or G-load is known.  It is simply an "off-angle" airspeed.  And, before I get flamed , people (like Mr. Baker) that have installed one and uses it as he does, I applaud him.  The device is making him a better pilot!  If you want to question me, I respect your opinion.  Ironically, placing them on the aft lower side of the wing is an area where AOA doesn't change (the airflow is parallel to the airfoil, which is why Piper puts pitot tubes in that location.

Now, for Cp measurement devices (like Garmin).  They measure differential pressure ("off angle" airspeed) and divide it by Qc (airspeed pressure or Ptotal minus Pstatic).  That value is what aero people call Cp.  That value is directly related to AOA.  Again, and in addition, an aircraft calibration  and all the other inputs need to be there to make it all calibrated AOA.   Process timing is also an issue with these devices.  IOW, all the pressures need to be taken at the same time, each data bus adds delay, each transfer of data adds delay .. it adds up quickly.

Please remain respectful.  I want to educate, but I also want to learn.  There are no dumb ideas or dumb questions.  There is A LOT of bad information out there … FAA included  

Let's discuss and learn.

[Blue on Top]

37 minutes ago, GeeBee said:

… method of approval and installation requires you to calibrate in flight test and not against the actual wing chord. I would also not install that on a FIKI airplane.

 

And here is the problem with NORSEE (no safety effect) installations of AOA.  How's this for irony?  A device designed to improve the safety of the #1 fatal accident cause falls under "no safety effect".  NONE of these low-end devices are certificated.  They are allowed to be put on certificated airplanes in the hope of helping the accident numbers … time will tell.  ASTM self-approval only states that the same device must be produced over and over.  It does NOT require the data to be accurate … it's NORSEE.  NONE of these devices show compliance to a regulation.  If they did, they would be required to be accurate.

Agree on FIKI.  But, on that note, the vast majority of these fatal accidents are in Day, VFR flight.

[carusoam]

We are doing much better lately discussing this topic...

1) Lots of flexibility built into people’s opinions... just now it is more obvious how flexible they are... 

2) Some go to the extent of explaining what they use, and how they use it...

3) Some are OK with not having one and it matches their need perfectly well.

4) Some have added concerns regarding when one type of sensor may not work as expected...

5) Bob included exactly how his exact AOAi is calibrated.

6) It would be really helpful to know how the sensors react to being in rain.... snow and ice...

7) Since ice on the wing changes the AOA that the ice modified wing actually stalls at... the AOAi is no longer calibrated to the newly modified wing...

8) Ice on the sensor may actually keep it from giving valid data... of any value...

9) So for @GeeBee do you mean... you wouldn’t use a CYA-100 in nice weather on a FIKI plane... or you would use a heated AOAi appropriate for a FIKI plane to match its heated stall warning vane... and ice light and secondary pumps and tanks...?

does an AOA sensor exist for a Fiki installation on a Mooney?

10) there are going to be children of the magenta line... have no fear... MS even gently brings them up to speed over time... 

11) there probably aren’t going to be children of the AOAi... we still have the ASI with a heated pitot... and a stall warning system to remind you when things have gone less than perfect... even pear-ish...

12) Around here there are a few AOAis in use...

• CYA
• BK
• Aspen, the Aspen has an indication for flaps down or up...
• Alpha Systems

13) Calibration is everything... the user needs to know / verify its calibration... for optimum use... since the prior user may have included flaps, or didn’t...   

14) Heads up displays... or even putting the lights closer to line of sight has value...

15) my biggest challenge with using the ASI... scanning inside the plane and back outside the plane, rapidly...

Fortunately I’m not using the instruments for primary control on final approach... in VMC.

16) hey wait... gravity and bouncing can effect AOA sensors as well as other vane like sensors... it can also effect ASI needles and other mechanical displays...and eyeballs...

17) I got to fly right seat in an O with an Alpha Systems heads up display... not knowing the pilot very well... one gets an eerie feeling for trust in their instruments and skills...  we landed perfectly on the numbers about five knots slower than I would have used without the AOAi... (thanks to Dr. Fox who took me flying on some practice IFR approaches a few years ago) not the Dr. Fox that is a plane surgeon... 

Go MS!

Best regards,

-a-

[Bob_Belville]

These pics of the CYA 100 AOA have been posted on MS before. As you can see the light stack is very narrow and small and fits anywhere. I positioned mine at the top of the panel and right between the primary ASI (Aspen) and the BU. 

The CYA AOA is not critical to flight, it is not heated, and would be useless if iced up. 

[Andy95W]

4 hours ago, Blue on Top said:

And here is the problem with NORSEE (no safety effect) installations of AOA.  How's this for irony?  A device designed to improve the safety of the #1 fatal accident cause falls under "no safety effect".  

Except that's not what NORSEE stands for.  It actually means NOn Required Safety Enhancing Equipment.  What this means is that the equipment is not required under the type certification standards that the FAA has laid out, but the FAA recognizes it as safety enhancing.  (This also explains why the FAA has allowed this to be an easy and approved shortcut for installation approval.)

https://www.faa.gov/aircraft/air_cert/design_approvals/norsee/

[Blue on Top]

1 hour ago, Andy95W said:

Except that's not what NORSEE stands for.  It actually means NOn Required Safety Enhancing Equipment.  What this means is that the equipment is not required under the type certification standards that the FAA has laid out, but the FAA recognizes it as safety enhancing.  (This also explains why the FAA has allowed this to be an easy and approved shortcut for installation approval.)

https://www.faa.gov/aircraft/air_cert/design_approvals/norsee/

100% agree with your statement and FAA reference … I deal with it daily.

1) To flip the coin, how many pilots realize that there is no requirement for accuracy on NORSEE items (AOA is a great example)?

2) One of the hardest parts of certification of these types of items is how to alleviate misleading information.  How do you ethically address that issue?  One of the largest flying clubs in the nation has AOA on their training airplanes.  They are teaching students to not use the information because of the poor and erratic information being presented.  Instructors can't use them either.  The Pegasus (FAA) program at Purdue proved this, too.  Part of that issue was training, though.

I believe that AOA has gotten a bad rap because it's not (calibrated) AOA that is being presented.  BTW, LRI is a made-up word because people finally admitted it wasn't AOA.

[carusoam]

.... the ‘don’t fall out of the sky’ sensor was too long to say... 

 

Norsee is probably the method that airbag seatbelts have gotten the ability to get into most Mooneys...

Somethings are best blessed by the FAA...

Fortunately the FAA has opened a door for alternative methods of approval...

But, even the FDA doesn’t approve every step of the pharmaceutical process... they provide guidelines... companies follow the guidelines... for many things...

The FAA isn’t the only intelligent resource when it comes to GA planes... there are many other independent people that can provide a valuable service... qualification, and validation steps... on the way to approval if required...

Then there is the failures that come with some devices...

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...

Its internal sensor needs to be in line with the airplane... some instrument panels have various bends and folds...

 

Have you seen the electronic AI around here that picked up a case of the leans...?

 

The mechanical AIs are pretty good... but have all kinds of quirks... from worn bearings to acceleration/deceleration oddities...

Best regards,

-a-