I have a Dynon 10inch skyview with AOA. I have used AOA in the T38. but the dynon display is much different. I know green is safe, yellow not so safe, and red very bad. how are others reading the Dynon AOA. or where would the max performance green doughnut be if it had one. thanks Dan
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AOA
- Thread starter Miata
- Start date
Bill_H
Well Known Member
I operate off of a short 1260 foot strip on a ridgeline, slopes down at both ends. Love the AOA. But I never look at the AOA display. The variable frequency beeping in the headphone is the perfect interface as I keep my eyes outside the bubble on the approach and watch our for ridgeline sink or uplift.
ChiefPilot
Well Known Member
It depends on your calibration - mine is such that I'm in the mid-yellow when betty starts making noise and the last yellow bar is pretty coincident with max perf turn performance. It's not exact though.
I'd really like to have a display of units on the screen somewhere rather than the chevron, and it'd be cool to have a standalone indexer. The latter is certainly possible to build; the former not so much.
donaziza
Well Known Member
I have a Dynon AOA also ,but rather than the skyview, I have a Dynon 180. Anybody know if I can get noise in the headset like this guy??
I have a D100, which I believe is the same platform. I have my D100 wired to the intercom and it provides nice audio. The configuration menus offer options for voice (the voice option might be from the HS-34 that I have) or tones for AOA warnings.
I am not flying yet, so can't comment on how the AOA messages behave.
Larry
Av8torTom
Well Known Member
Not so useful
In my opinion that AOA instrument isn't much better than a stall warning horn.
If you really want useful AOA data I would go with the Advanced Flight Systems Pro AOA.
In my opinion that AOA instrument isn't much better than a stall warning horn.
If you really want useful AOA data I would go with the Advanced Flight Systems Pro AOA.
Can you elaborate on that? Why?
ChiefPilot
Well Known Member
Have you flown with one?
You have to pay attention and calibrate it correctly.
It takes a while, it takes care and the final part - the full power stalls need to be done carefully.
However, when it is done, it is spot on.
Green, amber - yea - you are OK. get to the top of the amber and watch out, when it goes red, you depart.
To be honest, you know because of stick position and attitude.
For those who are not aware, stick position is directly linked to aoa and therefore to stall. If you find yourself with the stick well back, you have to ask yourself why and are you comfortable ?
On approach, aoa is great if you are going into a short strip - gives you a much better idea of where the energy is and what safety margin you have.
That is if it is correctly calibrated.....
It takes a while, it takes care and the final part - the full power stalls need to be done carefully.
However, when it is done, it is spot on.
Green, amber - yea - you are OK. get to the top of the amber and watch out, when it goes red, you depart.
To be honest, you know because of stick position and attitude.
For those who are not aware, stick position is directly linked to aoa and therefore to stall. If you find yourself with the stick well back, you have to ask yourself why and are you comfortable ?
On approach, aoa is great if you are going into a short strip - gives you a much better idea of where the energy is and what safety margin you have.
That is if it is correctly calibrated.....
boomer
Well Known Member
My AOA is on the D180, but I assume it is the same as yours. My previous AOA experience was in F-4's and F-111's which had indexers and a green "on speed" ball which also was useful for max performance turns. Initially I tried to establish a reading for final approach and max performance turns much like the green ball in military AOA's, but gave up for two reasons:
1. Remembering and counting the green bars for "on speed" is just too hard and not productive, IMO. I too wish there was a classic indexer readout, but there's not.
2. For max performance, the RV lift curve is so flat that one doesn't really find a narrow regime where pulling harder decreases turn performance-- until the stall that is. When I max perform, I nearly always do it to a selected G (3 G's is my favorite <G>) rather than a turn rate. One can pull more G's but I chose not to for a number of reasons.
Given all that, the AOA indicator and the stall audio are useful when making slow speed steep turns and on short final when you don't want to take a quick peek back inside at the airspeed. I have found the stall warning function quite accurate and quite comforting.
-John
Don't know about other Dynon products, but lots of features have been added at users' requests to the Skyview line. Given that these sorts of things are "just software", I'd say go over to the Dynon forum and toss it into the mix as a requested feature. They've been pretty responsive in the past (although, for the life of me, they still don't have the capability to use flap position in the AOA computations/indications, which seems horribly wrong to me; that said, I do like the SV AOA indications/audio alerts very much).
Brantel
Well Known Member
You could build your own AOA display and used Dynon's serial stream to drive it. The code to parse the serial data out of the stream is so easy even a hack like me did it.
http://www.vansairforce.com/community/showthread.php?t=68922&highlight=remote+aoa+display
http://www.vansairforce.com/community/showthread.php?t=68922&highlight=remote+aoa+display
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carrollcw
Well Known Member
For those who are not aware, stick position is directly linked to aoa and therefore to stall. If you find yourself with the stick well back, you have to ask yourself why and are you comfortable ?
This is absolutely not true. As a prior fighter pilot, I can attest to this statement's falsity. AOA has nothing to do with stick position. In an RV-7 at 180 KIAS full aft stick (probably over G), you will not be in the same AOA as full aft stick at 80 KIAS (will stall). Instead, AOA is more easily understood as the airplane's energy state at a given stick position related to airspeed, altitude, attitude, and weight. If you calibrate it properly, it can help you understand the airplane's ability to perform the desired maneuver (based on the aforementioned factors). Calibrate the green circle for best glide. That should also correspond to best turn performance. Then strive to be in the green circle when in the final turn at 75ish KIAS, throughout a loop (between entry to the end), or if dogfighting and wanting your best sustained turn rate for a given airspeed. If your desire is to accomplish the best nose rate, you should be in the yellow chevron as best nose rate is not sustainable but for a few seconds.
OK, all in fun now: This absolutely IS true. As a prior fighter pilot, I can attest to this statement's veracity. AOA has everything to do with stick position.
Yes I am a former fighter pilot, but that doesn't change what rules angle-of-attack follow. During my instruction and particularly when giving BFR's, I demonstrate that stick position equals "alpha" (AoA) by doing the following: I do a power off, level, one-G stall, and ask the other pilot to carefully note the stick position. Then I do an accelerated stall at about 2 to 2.5 G's, and again carefully note the stick position.
For all practical considerations, the stick positions are the same.
Now, I am sure that an aero engineer will comment and explain that there are small differences in stick position, but to the unaided eye, the stick position is the same.
Try it yourself, if you don't believe me.
"Screens up, Scotty!"
I believe that is exactly what was done on the Ercoupe.
One issue is that as the CG changes, so does the stall stick position. So perhaps to get a full CG range, it is necessary to have some additional control authority. Pure speculation on my part here!
Steve Smith, comments invited!
One issue is that as the CG changes, so does the stall stick position. So perhaps to get a full CG range, it is necessary to have some additional control authority. Pure speculation on my part here!
Steve Smith, comments invited!
rmartingt
Well Known Member
Those differences will creep in with CG (as you noted), transonic/supersonic effects (center of lift moving aft, etc; not a factor for RVs), landing gear extension (if equipped), flap/slat deployment (again if equipped), etc.
Yep, that's part of the problem. Unless you have some kind of fancy auto-compensating limiter that looks at CG, you're going to set the stop for your worst-case condition. That leaves you running out of elevator authority at forward CG conditions, meaning you're landing faster and running the chance of landing nosewheel first.I believe that is exactly what was done on the Ercoupe.
One issue is that as the CG changes, so does the stall stick position. So perhaps to get a full CG range, it is necessary to have some additional control authority. Pure speculation on my part here!
If you're going to have said fancy auto-compensator, then instead of trying to predict CG and limit stick deflection, it'll almost certainly be easier just to pick off calibrated AOA to drive a stick shaker and use your autopilot servos as an alpha limiter (like Garmin has apparently just done). I think this is going to become a more common approach, especially as it looks like the newest round of certification requirements are getting tougher on stall/spin resistance. As much as it bugs a lot of people (and even myself sometimes), I think fancier and more involved systems than we're used to seeing--that is, AOA indicators, stick shakers, the EFIS-based limiters mentioned above, and so on--are going to be pushed harder and harder. Stall/spin accidents keep happening no matter how many times we admonish ourselves to "be a better pilot and practice"; we can keep trying the same approach and keep watching it fail, or we can try something else.
Av8torTom
Well Known Member
Because AOA is NOT just about stall warning, it's about providing the pilot with detailed information about that the wing is doing. All of your V speeds for example can have an AOA value, but that requires an instrument that provides degrees AOA and not just some lights on a bar. The Advanced Pro AOA has both a light bar and degrees AOA readout.
I have not flown with the Advanced AOA, but have flown with another AOA instrument that provided a degrees AOA readout. I knew for example that on take off my airplane 8 deg AOA gave me Vx. There was no searching around with pitch chasing an airspeed indicator. I could instantly bring the wing to 8 degrees and I was done. The airspeed indicator would then settle on Vx some moments later.
Obviously I'm a huge fan of AOA information in the cockpit. I would like to see people's thinking evolve past just the stall warning information it provides. A good AOA instrument can provide much more.
rmartingt
Well Known Member
A really interesting and relevant paper on the subject: NASA/TM?2014-218514: Review of Research on Angle-of-Attack Indicator Effectiveness
Some money quotes (emphasis mine):
And yet... with study after study after study, spanning multiple decades, with entire books written on the subject, so many pilots still insist that AOA indication is "useless", "secondary to airspeed", "a distraction", a "gee-whiz gadget"; that a "Real Pilot" doesn't need those things but instead will just "feel" the airplane.
Some money quotes (emphasis mine):
And yet... with study after study after study, spanning multiple decades, with entire books written on the subject, so many pilots still insist that AOA indication is "useless", "secondary to airspeed", "a distraction", a "gee-whiz gadget"; that a "Real Pilot" doesn't need those things but instead will just "feel" the airplane.
Walt
Well Known Member
Good post, I think that pretty well sums it up!
Restating the Obvious
I'm a former Navy carrier pilot and commanded a Navy Aggressor squadron. AOA was the primary instrument for landing on the boat (and everywhere else since we always trained to boat procedures) and edge of the envelope sustained G maneuvering in the A-4. It also provided ballpark max range / max endurance airspeeds. It was also a primary aide in spin/departure recovery - if the AOA wasn't pegged up or down, you weren't in a spin and application of spin recovery procedures was probably going to make things worse.
AOA was useful not only for real time energy determination, but also trends. Unwanted increasing AOA meant you were either underpowered in level flight - or your attitude was different from what you wanted.
Each to his own - but like other cockpit tools, the pilot has to understand its capabilities, limitations and procedures.
I'm a former Navy carrier pilot and commanded a Navy Aggressor squadron. AOA was the primary instrument for landing on the boat (and everywhere else since we always trained to boat procedures) and edge of the envelope sustained G maneuvering in the A-4. It also provided ballpark max range / max endurance airspeeds. It was also a primary aide in spin/departure recovery - if the AOA wasn't pegged up or down, you weren't in a spin and application of spin recovery procedures was probably going to make things worse.
AOA was useful not only for real time energy determination, but also trends. Unwanted increasing AOA meant you were either underpowered in level flight - or your attitude was different from what you wanted.
Each to his own - but like other cockpit tools, the pilot has to understand its capabilities, limitations and procedures.
AoA Flap Position Sensor
I've enjoyed reading all your comments about AoA. Very compelling.
I am a new RV-8 owner and a low-time pilot. Installing an AoA and learning how to calibrate and use it correctly is one of my highest priorities.
I just read "Angle of Attack Indicators" by Charlie Precourt in the April 2015 issue of EAA's Sport Aviation.
In Mr. Precourt's article, it states, "the better (AoA) systems available on the market also accommodate input for gear and flap position, but not all do".
The article does not describe why a flap position sensor makes the AoA system better.
My RV will stall about 7 knots faster clean (without flaps) then with flaps fully deployed. Is that why?
Here's my question:
With consideration to purchasing and installing an AoA in my RV-8, which AoA is all around functionally better because it provides better more accurate information in all phases of flight and configurations?
1. Advanced Flight Systems
2. Dynon
3. Garmin
4. Other
I want to make an informed decision. Do you all have flap position systems
Thank you,
I've enjoyed reading all your comments about AoA. Very compelling.
I am a new RV-8 owner and a low-time pilot. Installing an AoA and learning how to calibrate and use it correctly is one of my highest priorities.
I just read "Angle of Attack Indicators" by Charlie Precourt in the April 2015 issue of EAA's Sport Aviation.
In Mr. Precourt's article, it states, "the better (AoA) systems available on the market also accommodate input for gear and flap position, but not all do".
The article does not describe why a flap position sensor makes the AoA system better.
My RV will stall about 7 knots faster clean (without flaps) then with flaps fully deployed. Is that why?
Here's my question:
With consideration to purchasing and installing an AoA in my RV-8, which AoA is all around functionally better because it provides better more accurate information in all phases of flight and configurations?
1. Advanced Flight Systems
2. Dynon
3. Garmin
4. Other
I want to make an informed decision. Do you all have flap position systems
Thank you,
Bill_H
Well Known Member
If you have a Dynon system, the AOA is "built into it." All you have to provide is the tubing input from the sensor, and this can be as little as $12 in parts. The DYNON Skyview provides both onscreen and audio output of the AOA.
I calibrated mine for the flaps-down landing condition as I operate off a 1260 foot strip. Love the AOA! For details on the $12 sensor, read this thread, starting page 2. You do not need the fancy combo pitot. I have the basketball inflation needle sensor, later in the thread the flush rivet sensor was proven.
The thread is about the RV12 but it would apply to any RV or other plane, for that matter.
http://www.vansairforce.com/community/showthread.php?t=34040&highlight=AOA+RV12&page=2
I calibrated mine for the flaps-down landing condition as I operate off a 1260 foot strip. Love the AOA! For details on the $12 sensor, read this thread, starting page 2. You do not need the fancy combo pitot. I have the basketball inflation needle sensor, later in the thread the flush rivet sensor was proven.
The thread is about the RV12 but it would apply to any RV or other plane, for that matter.
http://www.vansairforce.com/community/showthread.php?t=34040&highlight=AOA+RV12&page=2
rmartingt
Well Known Member
No! Stop thinking airspeed! Your clean vs. dirty speed has nothing to do with it. Stall speed is a result, not an input.
Flaps can potentially change the AOA at which a given wing stalls; how big of an effect they have is dependent on the airfoil, the flap geometry, the wing planform, etc. An AOA indicator/stall warning system with a flap position input can be calibrated for the stall AOA at different flap settings; those without flap position input probably just use the worst case out of all flap settings (i.e. lowest AOA value recorded at stall) and are therefore a little conservative at the other flap settings.
Anecdotally, I've heard the difference in flaps-up vs. flaps-down stall AOA on the short-wing RVs is small, but I don't know for sure. I'll have to defer to the manufacturers and those who have flown tests on these aircraft.
Trailing edge flaps generally decrease the angle of attack where the wing stalls. The do however increase the CL the wing can generate before stall so the reduction in AOA is outweighed by the increase in lift.
Leading edge devices increase the stalling AOA with little effect on CL at a given AOA. That is why you see both on most modern airliners. They work together quite well.
In a RV if you have a system without a flap position indicator I would set it up to provide a stall warning with the flaps down. This will mean your warnings will be a little conservative in the clean configuration.
George
Leading edge devices increase the stalling AOA with little effect on CL at a given AOA. That is why you see both on most modern airliners. They work together quite well.
In a RV if you have a system without a flap position indicator I would set it up to provide a stall warning with the flaps down. This will mean your warnings will be a little conservative in the clean configuration.
George
Av8torTom
Well Known Member
I believe the Advanced Flight Pro is the only one available with a degrees AoA readout. As I've stated previously, without that you really have just a glorified stall warning horn. Stall warning is but ONE use for having AoA information in the cockpit.
rmartingt
Well Known Member
I think the important part isn't the numerical readout, but rather that there's some means of referencing a given condition so that one can repeatedly attain it. If one had marks on an AOA indicator corresponding to optimum approach AOA, best glide, climb, etc. that would be just as good as a number. Or if the number was a "normalized" value rather than true degrees, it would be just as useful.
In other words, it doesn't matter if optimum approach AOA is 7.2 degrees relative to the wing, 9.2 degrees relative to the fuselage, .81 normalized AOA, or the blue line on the indicator--as long as I have that indication, I can fly to it repeatedly.
Edit: On another note, is there some industry standard for AOA displays?
ChiefPilot
Well Known Member
Incorrect, at least insofar as not have a readout in degrees being next to useless.
If it were true, modern military aircraft would have useless AoA indicators and they use AoA for far more than just a stall warning.
Av8torTom
Well Known Member
I totally agree - as long as the light bar display has the resolution (many do not) to provide that information. and you can remember which bar needs to be lit to achieve the performance you want. Personally, and from experience, I prefer being able to go to a number. The degrees AoA for a given wing's performance will likely be different for each type or aircraft and installation, but once you observe for example, what AoA provides best climb or best glide you can pitch to those numbers and hit those speeds every time with the least delay.
carrollcw
Well Known Member
OK, all in fun now: This absolutely IS true. As a prior fighter pilot, I can attest to this statement's veracity. AOA has everything to do with stick position.
Yes I am a former fighter pilot, but that doesn't change what rules angle-of-attack follow. During my instruction and particularly when giving BFR's, I demonstrate that stick position equals "alpha" (AoA) by doing the following: I do a power off, level, one-G stall, and ask the other pilot to carefully note the stick position. Then I do an accelerated stall at about 2 to 2.5 G's, and again carefully note the stick position.
For all practical considerations, the stick positions are the same.
Maybe in that one example, in a stall scenario, stick position has a relation to AOA, but as a prior fighter pilot, you should be able to follow this example. In a break turn beginning above cornering velocity, if you pull full aft stick, you will initially be at a much lower AOA than after speed deteriorates. As it deteriorates you will slow to cornering velocity (unless you have excessive thrust to weight) as aoa increases (still full aft stick) where you will most likely unload to capture cornering velocity aoa (unless in a nose position fight).
I want to have AOA configured to let me know when I can get away with full aft stick application vs when I have to fly with a little more finesse.
Respectfully, I think you are over simplifying things a bit.
ChiefPilot
Well Known Member
So just for s**ts and grins...what IS cornering velocity in an RV?
Corner speed (or Vc) is the indicated airspeed at which maximum load factor occurs without inducing an aerodynamic stall or structural failure and occurs at the same point on the V-N diagram as Va.
The Vc of my particular aircraft is classified
Corner speed (or Vc) is the indicated airspeed at which maximum load factor occurs without inducing an aerodynamic stall or structural failure and occurs at the same point on the V-N diagram as Va.
The Vc of my particular aircraft is classified
Oh, well, THAT'S no fun...here I thought it would be something really *cool*, not just boring old Va LOL!
Wunderon
Well Known Member
mmm, Va includes full rudder deflection, one time, so not sure which control surface is the Va limit. I'd argue cornering is primarily an elevator/airspeed/load limit.
anyone volunteer their airspeed/weight/power for a sustained level 4 or 6 G turn? Or is it a lower G?
simpkinsona
Well Known Member
ChiefPilot
Well Known Member
It's a lower load factor. The actual turn rate (degrees per second) is pretty good though.
