AOA - Pros, Cons and Experiences

[Blue on Top]

I'd like to know people's experiences with angle of attack instruments.  Do they work?  Do they not work?  Are they easy to use?  Are they helpful?  Etc...

I will be completely transparent.  I know Part 23/25 and military certificated AOA systems inside and out and how they operate.  I have designed a 6-hole probe (really 11 holes) to measure: airspeed, alpha (AOA), beta (angle of sideslip), altitude and vertical speed to autonomously control an unstable UAV … 30 years ago.

I am currently designing a system for certificated airplanes.

Thank you!  Your comments will be priceless.

[carusoam]

For some background...

https://mooneyspace.com/search/?q=AOAi

and look for some writing by @201er on the topic...

Expect some people to have a challenge with the costs involved... supported by the tradition under which they have been taught to fly...

Some people get the same thing out of their memory of WnB, stall speed vs bank angle chart, and ASI... others use their AOAi with a lot less memorization involved or interpretation... 

Best regards,

-a-

[Blue on Top]

Thanks!  What is AOAi?  is this simply indicated angle of attack?  There are so many made up terms on this particular topic because people/companies make up terms when they are challenged by knowledgeable people.  As a great example, "Critical AOA" is a common but made up term.  It means nothing to an Aerodynamicist.  They would call that the stall angle of attack. 

[carusoam]

Inviting bob @Bob_Belville to join the conversation...

Bob has a nice cost effective AOAi in his ship...

One of the threads covered all the various manufacturers of AOAi equipment that is used by MSers...

Best regards,

-a-

[DonMuncy]

I'm guessing that AOAi, is an Angle of Attack indicator, or instrument.

First the disclaimer; I am a proponent of AOAs, but have no beef with anyone who feels they are not needed, or don't think they are justified.

Knowing your angle of attack, is almost meaningless. But knowing the angle of attack where you plane stalls is invaluable. So the calibration is the key. When we installed mine, we went calculated the weight and used the POH figures to set the indicator (on mine, the blue light) at 1.3 times stall speed. We then flew to the stall buffet and located the indication where that occurred. I now know when I get to "the second yellow light" it is going to start buffeting, but not before. In my view, we (collectively)have always used the airspeed indicator as an indirect method of determining when a stall is going to happen, but the AOA gives the direct answer. I am not that good a pilot, and it is consoling to me to know that I can look and know how close I am to a stall. I am now more comfortable flying closer to the stall than before. 

[carusoam]

Sorry I left out an important detail that evolved here over time....

AOAi = Angle of Attack indicator

which should probably be rAOAi = relative Angle of Attack indicator (as Don described it above)

 

There has been a lot of mis-direction in the past because some people were talking about one thing, and others caught in an argument because they weren’t on the same page... with regards to terminology...

Cool tools...

Best regards,

-a-

[Blue on Top]

-a-: I'm going to regret saying this, but … wait … I'm gaining a brain … so I won't say it 

Thanks for your input.  I whole-heartedly agree with you on mis-interpretations, mis-direction, mis-informaton.  That is exactly what I am going after … to fix.  The mountain is BIG!

PS.  I'm going back through old threads.  Holy crap!  Some people are nasty.  Thanks again.  

[carusoam]

Some people are nasty... naturally...

It takes a fair amount of control to keep a warm friendly posture...

The more effort it takes to carry on a technical conversation... the harder it is to control that nature thing in the back ground...

 

Sort of multi-tasking of a high order... and friendliness got put on the back burner... a lot...

Check the dates/days of the posts...

Some nastiness will coincide with the day and time... Friday and Saturday nights often have some extra flare involved... 

 

Some wackiness is often between some friends who know each other well....and others starts with mis-interpretation by a new guy in the room...

So... if you feel like you have been attacked... check to see if you are mis-interpreting what has been typed...

Very few of us are pro writers and may be missing the ability to type a wink, or a nod... or a chortle... 

Don’t let the wackiness get in the way of a great factual exchange...

 

Best regards,

-a-

[JohnB]

I have an AOA I installed a few years ago (Alpha systems with Valkyrie HUD) and I can say it is HUGELY helpful. After flying with it for a few years, it becomes your indicator for landing speed near the numbers to achieve nearly perfect landings everytime, and on landing nowadays, I use my airspeed indicator to setup the approach, but then when I'm well on it, my AOA becomes pretty much primary for airspeed,  not having to correct for weight. Several other bonuses

• Alerts you when you are getting slightly slow, well before any stall speed like in turns, or climbs, so the odds of a base to final turn disaster are markedly reduced by an audible alert
• Gives you your best glide angle/speed by just looking at a value so in case I ever had engine out, I know my glide speed would be right on target for maximal glide.
• Easier to view rather than your airspeed indicator when landing, and when you get good at it, you can use different AOA values for different landing types (soft field, short field, gusty field, flaps, no flaps etc)
• Having a HUD is just cool (+100 cool points) 

No but seriously, I think having an AOA and using it adds lots of safety to your flying in the crucial periods of landing, climbing and maneuvering at lower altitudes.

[slowflyin]

My experience mirrors JohnB's.   Alpha with HUD as well.  I love it!   The difference in approach speed for my Bravo with just me and minimal fuel is much different than at max weight.  Throw in high density altitude and the delta grows.  The AOA nails the approach speed every time.  Just fly the blue doughnut and a float free landing is assured.   

[brndiar]

 

 

[Austintatious]

My .02 is that AOA is invaluable.  Yes you can fly without it, but with it you can not only be more confident but more accurate AND get more performance out of your airplane.

Confidence of speed on approach... maybe on this landing you are really heavy and 1.3 vs is higher IAS... Maybe you are lighter and going into a short field and you can slow down below normal IAS.

Climb performance...  Trying to climb steeply?, there is an AOA that will do this... the SPEED changes with weight, so if you go for the AOA you know you are right on no matter the load.

Climbing at  higher altitudes, target AOA, best climb airspeed changes with altitude.

Landing with partial or no flaps?  AOA! (sometimes this compensation needs to be corrected for electronically)

 

The other thing I like is that with a HUD of the AOA, on approach you can keep your eyes OUTSIDE and stay heads up for the whole approach. THIS alone would make an AOA worth it.

[irishpilot]

Every military plane I've flown has AOA and it is essential, especially when max performing the airfoil. A lot of GA accidents happen from stalls/spins in the final turn. Yes, if you fly the correct airspeeds, it shouldn't be an issue. However, it's another tool that is much more precise than a stall horn. Lastly, when ice builds up on an airfoil, you can see the impact on the AOA.

I also agree, the AOA must be calibrated in order to be useful. Do I want one for my Mooney, yes, but price is a driving factor.

Fly Safe,
Safety Forum Mod

[brndiar]

1 hour ago, irishpilot said:

Every military plane I've flown has AOA and it is essential, especially when max performing the airfoil. A lot of GA accidents happen from stalls/spins in the final turn. Yes, if you fly the correct airspeeds, it shouldn't be an issue. However, it's another tool that is much more precise than a stall horn. Lastly, when ice builds up on an airfoil, you can see the impact on the AOA.

I also agree, the AOA must be calibrated in order to be useful. Do I want one for my Mooney, yes, but price is a driving factor.

Fly Safe,
Safety Forum Mod
 

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

[bonal]

On December 5, 2019 at 9:15 PM, DonMuncy said:

I'm guessing that AOAi, is an Angle of Attack indicator, or instrument.

First the disclaimer; I am a proponent of AOAs, but have no beef with anyone who feels they are not needed, or don't think they are justified.

Knowing your angle of attack, is almost meaningless. But knowing the angle of attack where you plane stalls is invaluable. So the calibration is the key. When we installed mine, we went calculated the weight and used the POH figures to set the indicator (on mine, the blue light) at 1.3 times stall speed. We then flew to the stall buffet and located the indication where that occurred. I now know when I get to "the second yellow light" it is going to start buffeting, but not before. In my view, we (collectively)have always used the airspeed indicator as an indirect method of determining when a stall is going to happen, but the AOA gives the direct answer. I am not that good a pilot, and it is consoling to me to know that I can look and know how close I am to a stall. I am now more comfortable flying closer to the stall than before. 

So what your saying is you used the feel and performance  of your airplane to calibrate your AOAi which is something that everybody piloting an airplane should be doing at all times weather they have the indicator or not. I'm sure the AOA is a great tool but in my opinion knowing or better yet feeling what your airplane is telling you should be better understood than an instrument that could become inaccurate or fail perhaps leading you to believe life is good when in fact it may not be. As usual I accept that this opinion will not be popular, story of my life. It's aaalllll good.

[JohnB]

32 minutes ago, bonal said:

So what your saying is you used the feel and performance  of your airplane to calibrate your AOAi which is something that everybody piloting an airplane should be doing at all times weather they have the indicator or not. I'm sure the AOA is a great tool but in my opinion knowing or better yet feeling what your airplane is telling you should be better understood than an instrument that could become inaccurate or fail perhaps leading you to believe life is good when in fact it may not be. As usual I accept that this opinion will not be popular, story of my life. It's aaalllll good.

You do have to calibrate your AOA  flying close to your stall speeds , and other speeds and configurations which is clearly outlined in the instructions. (Much easier to do if you have two pilots,  one flying and one hitting the cal buttons) but once you do it, it’s done and you will then get warnings well before your airplane starts to buffet or feel any different, and also well before your stall horn sounds. 

[bonal]

Not saying you won't get warnings but don't you think you should know what your attitude of flight should be without it. Do you think Langewiesche needed such a device. People become over dependent on all kinds of technology and then when it fails there is an inherent lack of skill to keep things from going sideways. Quite a number of instructional videos on the magenta pilot phenomenon as an example of basic navigational skills becoming less proficient as more and more technology takes over. Yes you can have lots of back up. But for heavens sake the best part of flying is flight, being in touch with the sensation of it. It's what I love about riding motorcycles it's so pure. I guess I'm just a romantic. 

[GeeBee]

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.

 

[Blue on Top]

4 hours ago, irishpilot said:

I also agree, the AOA must be calibrated in order to be useful. Do I want one for my Mooney, yes, but price is a driving factor.

Fly Safe,
Safety Forum Mod
 

A ROUGH estimate on price.  I know, this isn't fair because I'm not telling you all the features.  Actual, calibrated AOA is the only way to go.

[Blue on Top]

1 hour ago, bonal said:

... don't you think you should know what your attitude of flight should be without it. Do you think Langewiesche needed such a device.

No, we are flying newer technology airplanes that are not Cub-like … and even those have their fair share of stalls-spins-spirals on takeoff and during moose turns (maneuvering near the ground).  Today's airplanes may or may not give the pilot a natural warning before they depart.  This answers the question about Wolfgang, too.  And, although I love his book, AOA is not the acute angle between the chord line and the direction of flight … unless the air is perfectly calm (no thermals, no bumps, no gusts, no etc.)  

[Blue on Top]

48 minutes ago, GeeBee said:

The only true AOA for GA I know of is the SafeFlight system.

 

It's not either.  The force on the flipper vane is airspeed dependent … and changes in rain.

[bonal]

I guess I have to re read it again but I'm pretty sure he discusses many variations of air flow and its relationship to angle of attack not just chord and direction of flight. As for new technology my old c is based on a design not much newer than a cub. I think a C is a great stick and rudder fun to fly basic airplane the only thing I miss about my C150 is doing full stalls to fully developed spins. I'm not advocating that folks shouldn't enjoy equipping there airplane with the best tech money can buy. I just derive my enjoyment of flying from a different perspective. If I were an instrument rated pilot that needed to fly in challenging weather I would be on the other side of this coin but that's not me. I like these discussions because it reminds me of what's important when it comes to safe operation of an airplane. I remember a fellow called me stupid or something not nice years ago around here because I mentioned the importance of airspeed well his comment got me thinking about the importance of AOA and wing loading. All I'm saying is the more people rely on technology the more they risk losing the ability to feel what's going on around them. Please correct me if I'm wrong but aren't the airlines going back to a greater emphasis on stick and rudder skills in their training because too many incidents have been attributed to the pilots dependence on the airplane doing all the flying.

[GeeBee]

38 minutes ago, Blue on Top said:

It's not either.  The force on the flipper vane is airspeed dependent … and changes in rain.

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.

[gsxrpilot]

2 hours ago, bonal said:

Not saying you won't get warnings but don't you think you should know what your attitude of flight should be without it. Do you think Langewiesche needed such a device. People become over dependent on all kinds of technology and then when it fails there is an inherent lack of skill to keep things from going sideways.

You're making some huge leaps in your assumptions. 

One can have warning systems and still be aware of flight attitude. Nothing wrong with a backup, or secondary indication. Why do we need a stall horn if any halfway competent pilot can feel the buffet before the stall.

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.

Going from possessing a certain technology and becoming  over dependent, is a leap and accusation I would hesitate to make. One does not guarantee the other.

2 hours ago, bonal said:

Quite a number of instructional videos on the magenta pilot phenomenon as an example of basic navigational skills becoming less proficient as more and more technology takes over.

There is one of those videos and it was done a long time ago. Yes, it's quite famous. But again, having a GPS and being dependent on it are two very different things. I flew from Denver to Austin this weekend. I was at 17,500 ft. Pilotage is a bit more difficult from that altitude but not impossible. I was talking with ATC about an upcoming MOA that was hot. He gave me a VOR to navigate to as a means to stay clear. No problem. A few minutes later he asked if I was /G equipped, I confirmed I was. So he gave me a Waypoint that allowed me to cut off more of the corner and save about 10 minutes off the trip. Could I have flown the trip down low, under the MOA's, or following a sectional and a compass to stay clear? Sure I could. But I wouldn't have flown Denver to Austin in under four hours and been able to land with almost three hours of fuel still in the tanks. My navigation skills are fairly good, but why not use the GPS when it makes life easier?

2 hours ago, bonal said:

But for heavens sake the best part of flying is flight, being in touch with the sensation of it.

That's a very nice part of flying, but so is being able to cross the country, up in the smooth and quiet flight levels, and arrive in time for lunch with family we haven't seen in awhile. And technology is what makes that possible.

AOA indicators are just another piece of technology that makes life just a little bit easier and more enjoyable. 

2 hours ago, bonal said:

It's what I love about riding motorcycles it's so pure. I guess I'm just a romantic. 

I'll agree with you here. I don't use motorcycles to GO anywhere, but rather for the experience. But if you're truly just a romantic, I think you have to get rid of all these newfangled machines and get back in the saddle... 

[GeeBee]

6 hours ago, bonal said:

Not saying you won't get warnings but don't you think you should know what your attitude of flight should be without it. Do you think Langewiesche needed such a device. People become over dependent on all kinds of technology and then when it fails there is an inherent lack of skill to keep things from going sideways. Quite a number of instructional videos on the magenta pilot phenomenon as an example of basic navigational skills becoming less proficient as more and more technology takes over. Yes you can have lots of back up. But for heavens sake the best part of flying is flight, being in touch with the sensation of it. It's what I love about riding motorcycles it's so pure. I guess I'm just a romantic. 

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