Idea for portable AOA device

[aviatoreb]

27 minutes ago, Yetti said:

so it's doing nothing to tell you that you are slipping or skidding in the base to final?   Seems that if we are adding more instruments we should have ones that are telling us that we are not flying properly

The ball already tells you if you are slipping or skidding.  The AOA gives information that no other instrument gives directly, which is how close the wing is to no longer flying.

[Yetti]

12 minutes ago, aviatoreb said:

The ball already tells you if you are slipping or skidding.  The AOA gives information that no other instrument gives directly, which is how close the wing is to no longer flying.

So we could say that the POH (information we are supposed to know) statement of "no turns under 90 mph without flaps in the pattern" and the airspeed indicator is the same information about how close the wing is to no longer flying?

Asking to see if I can use an accelerometer to figure out if the plane is slipping or skidding. ie the ball     (which would be easier than installing two pitot tubes)

[M016576]

2 hours ago, Yetti said:

so it's doing nothing to tell you that you are slipping or skidding in the base to final?   Seems that if we are adding more instruments we should have ones that are telling us that we are not flying properly

In a skid or a slip, you still have to stall the wing first for it to be a problem.  The AoA indicator shows you how close you are to a stall... where in a skid or wrapped up turn  your indicated airspeed at stall is higher than wings level- so without an idea of what your AoA is, or an in-depth understanding of stall vs angle of bank vs weight of your aircraft, you’re flying blind.

 

but you’re right- no amount of money spent is a valid substitute for proper training.  But on that note...  Can I shoot an approach to minimums in hard imc with just an OBS and ILS, and a steam powered 6 pack? Yes.  Would I rather use my Aspen and IFD440? Yes....

Edited February 4, 2018 by M016576

[aviatoreb]

2 hours ago, Yetti said:

So we could say that the POH (information we are supposed to know) statement of "no turns under 90 mph without flaps in the pattern" and the airspeed indicator is the same information about how close the wing is to no longer flying?

Asking to see if I can use an accelerometer to figure out if the plane is slipping or skidding. ie the ball     (which would be easier than installing two pitot tubes)

Yes for the thousandth time ias is an indirect indicator of how close you may be to stall but also the actual stall relies weight.  An aoa displays how close to stall you are in an easy and immediate indication you can use and interpret moment to moment.

[carusoam]

Yetti,

This is how I am seeing it... (let me know if I am off base, or it might just be better for somebody else, or it’s second hand information I read on MS...)

An AOAi simply does the math of weight and stall speed, based on bank angle, and flap setting (some), and delivers how near you are, or away from a stall, in a graphic way for quick and continuous (scanned) interpretation....

Some people look at the device as a meter for lift reserve.  Like a fuel gauge, Keep the indicator from running out...

It is an additional device added to the scan.  It may get priority at some time, or less at others, to make sure the ASI and the AOAi are both making sense...

 

Other things to keep in mind...

• Quality of the turn is not accounted for... a spin occurs after the stall.
• a stall can be initiated by one wing first, by being cross controlled, slipping or skidding....
• staying coordinated using the ball is still important.
• My stall charts don't include coordination, or unweighting of the wing, either...
• When getting to know the envelope and how it is defined using the AOAi, it will take extra effort.  Possibly, a few specific flights at Safe altitudes...

All of this is improves the statistics of having expected results.  

Using all the flight instruments in a normal fashion and keeping all the performance charts memorized can be more challenging on some days.  Or way down the line...  

PP thoughts only not a CFI.... I haven't installed an AOAi yet...

Best regards,

-a-

[Yetti]

OK so how does the AoAi take into account the current weight of the airplane, or is it just a estimated safe envelope?

[carusoam]

^^^ That’s a key question!

As you load your plane with people, fuel and baggage... the actual AOA needs to increase to a new location to maintain level flight.

Flying near empty, the AOA will be less than the AOA when full up.

The AOA is sensitive to a few mm on the leading edge, where the air splits to go over or under the wing.

With an increase in AOA, the split line moves downwards to the stall vane.

When the split line moves below the stall vane, the stall horn is activated.

So the AOAi is kind of measuring where the split line is.

anything that loads the wing adjusts where the split line needs to be...

• going slow, requires raising the AOA
• in a bank, requires raising the AOA

When raising the AOA, you run into a limitation.  This is when the airflow starts to separate from the wing.  This is what is probably called the critical AOA.  Buffet start to begin as small parts of the wing experience flow separation.  Stall trips at work... picture air splitting and flowing up over the stall strip causing disruption to flow in that limited area...

Using an AOAi gives you a visual of the effects of loading up the wing with weight, and g-forces...

This visual should match the ASI and the stall charts.  If not, calibration, install or other thing is amiss.

getting clearer, or am I not able to get my points communicated well enough?

A couple of interesting indirect indicators of AOA that you might see while flying level in cruise...

• The position of the trim indicator while the trim is holding the plane level...
• the position of the tale plane that is holding the tale down, more, or less...

Unfortunately, these are hard to watch while flying on final approach.

PP thoughts only, not a CFI...

Best regards,

-a-

[Hank]

5 hours ago, Yetti said:

so it's doing nothing to tell you that you are slipping or skidding in the base to final?   Seems that if we are adding more instruments we should have ones that are telling us that we are not flying properly

Calling Mike . . . .  @201er  He can clear up your confusion with how he uses his'n.

[M016576]

1 hour ago, Yetti said:

OK so how does the AoAi take into account the current weight of the airplane, or is it just a estimated safe envelope?

A has a pretty good description above- but here’s a slightly different one...

The wing (airfoil) stalls at the same angle of attack regardless of weight of the aircraft. If the gauge is calibrated for full flaps, or no flaps (two different airfoils, essentially, due to different cords), then it will automatically account for whatever weight your aircraft is flying at.... because weight alone only changes the angle of attack required to maintain flight- not the angle of attack where the stall occurs.

thats why “on speed” angle of attack is always the same for a given airfoil, regardless of weight... but if your aircraft is heavier or lighter, you’ll have more or less angle of attack for level, balanced flight. 

As weight changes, though, and as angle of bank changes, you will have a different indicated airspeed in order to maintain that same angle of attack.  The critical angle of attack point where the stall occurs, measured in degrees (or units of degrees in some aircraft), doesn’t change, but the indicated airspeed at the critical AoA point does.

[jaylw314]

11 hours ago, Yetti said:

so it's doing nothing to tell you that you are slipping or skidding in the base to final?   Seems that if we are adding more instruments we should have ones that are telling us that we are not flying properly

No, that's what the slip/skid ball is for.  On the other hand, if you had two AOA's it could tell you if there are different AOA for each wing, which is really what causes a spin, not slipping or skidding.  You sideslip during a crosswind landing, which is uncoordinate flight, but you're not in danger of spinning because both wings are at the same AOA.  

[Yetti]

Apparently AoAi are helpful in power off landings  Click here for the Angle of Attack Final Summary

 

I was under the impression that LOC accidents were the base stall spin and that is what AoAi were trying to solve for.

Apparently they are just to help stabilize the approach.....

I was solving for the base to final stall spin

 

[Yetti]

5 minutes ago, jaylw314 said:

No, that's what the slip/skid ball is for.  On the other hand, if you had two AOA's it could tell you if there are different AOA for each wing, which is really what causes a spin, not slipping or skidding.  You sideslip during a crosswind landing, which is uncoordinate flight, but you're not in danger of spinning because both wings are at the same AOA.  

Data vs. Information.   My day job in Operational Intelligence.   If you are going to use computers they should process the data and create information.   An AoAi for each wing is just more data.   Combining data presented by instruments and presenting it in a more user friendly format is called information.  The white arc and the needle of the ASI is a poor man's AoAi.   The closer I am to the bottom of the white arc with the needle is the less lift I have.   Again just data that I have to translate into information.   Introducing a computer should take all the data and have it tell me corrective actions.   "Straighten up"  "level the aircraft"   "Less rudder"   "too Fast"

[DonMuncy]

If you doubt the value of an AOA indicator. read Don Kaye's posts. I doubt there is a better pilot at landing Mooneys. And he says his AOA improved his landings.

[Baxsie]

If what is important is the "split line" of airflow on the leading edge of the wing, imagine a linear array of these sensors :

http://www.st.com/content/st_com/en/products/mems-and-sensors/pressure-sensors/lps25h.html

Perhaps spaced every 1/4" or every 1/2" along a strip 6~8 inches long. Use a local micro, thin liion battery and one of the tiny Bluetooth modules:

http://www.global.tdk.com/corp/en/news_center/press/20140212771.htm

Or this one, has a micro in it:

https://www.silabs.com/products/wireless/bluetooth/bluetooth-low-energy-modules/bgm11s-bluetooth-sip-module

Display it on your iDevice.

Build it on a flexible circuit, stick it on the wing. Calibrate with a couple stalls  at altitude. 

 

 

[jetdriven]

8 hours ago, Hank said:

Calling Mike . . . .  @201er  He can clear up your confusion with how he uses his'n.

Yeah we were doing slow flight and his AOA was buried full left. Showed completely stalled. I don’t even know his airplane well but I know that AOA is lying and airspeed and weight and G determine stall speed. . Ok let’s do another turn to the right but let’s do it at 30 degrees of bank. It did that just fine. So we were probably at 1.15 or 1.2 Vso which is normal short field landing airspeed.  Now a gadget that forces you to fly 10-15 MPh faster than you need to is no help at all.  Plus how does it know if the flaps or gear are down? These things matter you know. 

Mike has a slow J as well.  Look at this! 

[M016576]

5 hours ago, jetdriven said:

Yeah we were doing slow flight and his AOA was buried full left. Showed completely stalled. I don’t even know his airplane well but I know that AOA is lying and airspeed and weight and G determine stall speed. . Ok let’s do another turn to the right but let’s do it at 30 degrees of bank. It did that just fine. So we were probably at 1.15 or 1.2 Vso which is normal short field landing airspeed.  Now a gadget that forces you to fly 10-15 MPh faster than you need to is no help at all.  Plus how does it know if the flaps or gear are down? These things matter you know. 

Mike has a slow J as well.  Look at this! 

At first I saw 162...and said to myself- that seems fast to me!  Then I noticed... 16.2!  Which!  What, were you guys taxiing?!

a gauge is only as good as it’s calibration, or the information it’s receiving!  What’s up with that 430?

[Yetti]

11 hours ago, DonMuncy said:

If you doubt the value of an AOA indicator. read Don Kaye's posts.

I don't think anyone is doubting anything here  except jetdriven.    The AoAi has been promoted as a way to decrease fatalities in small GA Aircraft for LOC.  I am trying to understand what fatalities we are trying to reduce and what information pilots need to not become a fatality.   I was headed in the direction of reducing the stall spin on turn to base or turn to final.   As pointed out by Jetdriven and what I was surmising earlier to keep from stall spinning you would need a pitot static tube on each wing.  Then present the corrective action to the pilot as information to use since we were getting a computer involved.  A three axis accelerometer may be a replacement for the need for two pitot tubes.

Edited February 5, 2018 by Yetti

[aviatoreb]

9 hours ago, jetdriven said:

Yeah we were doing slow flight and his AOA was buried full left. Showed completely stalled. I don’t even know his airplane well but I know that AOA is lying and airspeed and weight and G determine stall speed. . Ok let’s do another turn to the right but let’s do it at 30 degrees of bank. It did that just fine. So we were probably at 1.15 or 1.2 Vso which is normal short field landing airspeed.  Now a gadget that forces you to fly 10-15 MPh faster than you need to is no help at all.  Plus how does it know if the flaps or gear are down? These things matter you know. 

Mike has a slow J as well.  Look at this! 

Once in a piper cub, in a fierce wind day, and in slow flight, we managed to stop the airplane and hoover about a thousand feet over my house. Sort of the exact opposite of buzzing.

Also the take-off and landing can be really funny in one of those vtol airplanes.  Essentially it just jumps up off the ground.

[Yetti]

Meh I flew a 172 backwards in slow flight.   I think I got the Mooney to zero GS last FR. 

[aviatoreb]

19 minutes ago, Yetti said:

Meh I flew a 172 backwards in slow flight.   I think I got the Mooney to zero GS last FR. 

We also flew backwards that day - but stopping in front of the house was cool.  My kids were tiny then and I called on the cell and told my wife to bring the kids out and look up at the little yellow airplane.  (I was not the one flying).

That is a bigger wind in a 172 eh.  I have certainly felt like I was flying backwards in a 172, but never literally.

[Piloto]

On ‎2‎/‎2‎/‎2018 at 12:52 AM, jaylw314 said:

I'm just randomly thinking.  Would it be feasible to make a portable AOA device by attaching a sensor to your side window?  If you take a small windvane with a metal base, you could attach it to your side window with a rare-earth magnet on the inside (both protected by rubber, of course).  The windvane has a electronic position sensor and bluetooth transmitter, with the receiver being a display that you would velcro to the top of your glareshield.

Since it is not permanently attached to the plane, it requires no installation.  It might need calibration, or you could have the receiver use the position during the ground roll as your zero degree calibration automatically.

Heck, if you wanted to go really low tech, you could just have a mirror on the glareshield pointing at the windvane on the side window.

Anyway, just my brain droppings for today...

A simple, low cost, portable and reliable AOA indicator is a 1ft of shoelace taped to the top of the wing close to the leading edge. As the AOA increase the shoelace will start separating from the wing surface. It will also show turbulence on the airflow.

Edited February 5, 2018 by Piloto

[201er]

1 hour ago, Yetti said:

As pointed out by Jetdriven and what I was surmising earlier to keep from stall spinning you would need a pitot static tube on each wing.  Then present the corrective action to the pilot as information to use since we were getting a computer involved.  A three axis accelerometer may be a replacement for the need for two pitot tubes.

What are you rambling about? All you need to do is keep the ball centered on the slip indicator with the rudder and the indication centered “on the ball” on the aoa indicator with pitch. There’s no math. There’s no pitot tubes on both sides. Just keep the two indications centered or as close to centered as possible on approach and you will not stall (including very steep turns in the pattern).

[aviatoreb]

20 minutes ago, 201er said:

What are you rambling about? All you need to do is keep the ball centered on the slip indicator with the rudder and the indication centered “on the ball” on the aoa indicator with pitch. There’s no math. There’s no pitot tubes on both sides. Just keep the two indications centered or as close to centered as possible on approach and you will not stall (including very steep turns in the pattern).

Sometimes you speak like a grumpy old man - geesh I wonder what you will be like when you actually are an old man!

Yes of course a standard AOA on one wing plus a slip-ball are sufficient.  OTOH two AOA indicators one on each wing would be sufficient.

OF COURSE there is math.  :-)  We are going around and around here about two classic topics in control theory - controllability and observability.

https://en.wikibooks.org/wiki/Control_Systems/Controllability_and_Observability

In a nut shell the idea is if you are observing enough independent variables to specify the state of the system so that then a controller can be built with enough actuators to steer the system system to a desired state.    This is a VERY well developed engineering/mathematics area because it is the heart of standard control theory used by engineers across multiple disciplines in a myriad of areas.  Technologies you use and love daily but you may be unaware of the algorithms built into your favorite devices.  Electronics, biomedical devices, car systems (engine, breaks, cooling), and on and on and on.

I'm with Yetti.  He is in sort of a policy-intelligence officer sort of way calling out that there could be a computer placed in the loop so that the feedback control plant can be built to easy the strain on our poor human brain which currently must serve the role of monitoring the input observed variables to compute control actions on the available actuators (the yoke position, pedal positions, the throttle positions are the actuators that we manipulate by moving our arms and feet).  Instead of seeing ball is too far left out of center and then computing in our feeble brains that what we need to do is something with our feet that will then do something with the rudder - it would be reasonable to ask if that computation could be done by a computer - ball is too far left and the computer speaks to us in english and says push your left foot on the left rudder because your in a slip condition.  It's a good idea - computers can help improve situational awareness and improve decision making in areas that computers are really good at - and this is an area that is easy-squeezy to imagine someone building.

[201er]

22 minutes ago, aviatoreb said:

I'm with Yetti.  He is in sort of a policy-intelligence officer sort of way calling out that there could be a computer placed in the loop so that the feedback control plant can be built to easy the strain on our poor human brain which currently must serve the role of monitoring the input observed variables to compute control actions on the available actuators (the yoke position, pedal positions, the throttle positions are the actuators that we manipulate by moving our arms and feet).  Instead of seeing ball is too far left out of center and then computing in our feeble brains that what we need to do is something with our feet that will then do something with the rudder - it would be reasonable to ask if that computation could be done by a computer - ball is too far left and the computer speaks to us in english and says push your left foot on the left rudder because your in a slip condition.  It's a good idea - computers can help improve situational awareness and improve decision making in areas that computers are really good at - and this is an area that is easy-squeezy to imagine someone building.

Might as well just have it fly itself then. What’s the point of talking to the feeble brained ballast wasting a seat that could be used for passengers.

[aviatoreb]

1 hour ago, 201er said:

Might as well just have it fly itself then. What’s the point of talking to the feeble brained ballast wasting a seat that could be used for passengers.

...did I say I want that?

I was saying that what Yetti was saying a) was indeed math which you declared it was not.  Fact is, yes it is math. Fact.  b very reasonable.  Your "might as well have it fly itself" could be applied as an argument to keep  all sorts of old school tech to counter that new fangled stuff: autopilot, hsi, synthetic vision, electronic engine monitor, AOA, backup AI because after all real pilots fly partial panel and they like it, and on and on.  Full disclosure I have all the above except for svt.  

Anyway, in terms of asking if something is a good idea it probably is for some and available to go old school for others.  I have your opinion on this issue for other devices - for example, the auto lean -"autopilot" stc, which I think is too much trouble for an easy to handle work load.  But I think it is a nice and very creative idea.  And I can see some wanting it.