Stalls and Turns by AOA

[201er]

I've been wanting to make a video showing my AOAi for a while and particularly with a comparison the ASI. I figured out how to mount a bunch of GoPros to achieve that. I went up on a smooth day to do just that. I was narrating as I was going but unfortunately the cockpit audio got messed up so I ended up doing some new narration in editing.

This is just a first test run of this recording method and I hope to do some more analysis at a later time. One of the main reasons I wanted to record this was to get a more precise correlation of airspeed to AOA. I will have some pattern work and simulated engine outs with this set up coming up soon. But for now, here's a video of performing power on stalls, power off stalls, constant AOA turns, and constant airspeed turns with comparison between airspeed and angle of attack. It's a good learning tool.

During this flight I was very light and the density altitude was quite low (negative at sea level). These stalls and slow flight look nothing like they do with a fully loaded airplane, especially on a hot high density altitude day. I believe this is a poor practice of stalls, although it is probably what most instructors would require you to demonstrate. I'm more focused on doing these maneuvers to be able to see a clear distinction between a stall break, airspeed, and AOA indication. I don't believe that practicing full stalls serves much merit beyond initially learning the characteristics of an airplane.

I'll need some more videos and flights to come up with an analysis in more depth than I've done before. But in the meantime, just to show you what I see and how airspeed compares with aoa.

 

[Robert C.]

Mike, great video! Required viewing for all student pilots

Since i got my AoA I've become completely habituated to glancing at it during the downwind-base and the base-final turn. Even on final I rarely glance down at the AS any more glancing instead at the AoA on the glareshield.

Robert

[Guitarmaster]

Nice job on the video Mike!

Sent from my XT1585 using Tapatalk

[Oscar Avalle]

Nice video Mike. I agree the AOA is a great addition. I also got so accustomed to it that I fly patterns and approaches mainly by reference to the AOA.  I found an older video I made showing a landing with a different kind of AOA. 

 

[DVA]

I have the Garmin AoA - but regardless these devices are all similar with a very simple design. Some use a different method of detection than another but basically they are all single-state calibrated devices. This means they will only be accurate in the configuration from which you did the calibration; such as approach to landing with full flaps and gear down, as an example. If you do have full flaps and gear down, they will not be accurate.

The FAA relaxed installation option for these devices states that they cannot be connected to any of the airplane’s other systems, such as P/S or flap position. If we able to interconnect (as is done in the certified devices) you could count on the device’s accuracy in all modes of flight.

Since we’re sharing home movies - here is an approach to landing. I have my AoA calibrated for the approach phase, the green ball and bottom green bars align when I’m at the correct approach angle which normally turns out to be around 70 knots or so as I cross the fence. Note that the AoA will start beeping when it gets into the yellow as I flare and hold it off, and you can see that when I land I am at a full stall, with the top red chevron is flashing and beeping right beforehand.

To my point above, if I go up and fly the airplane in a landing config, I can rely on the AoA in any attitude or airspeed and it will indicate full red with beeping just a few knots before the airplane stalls. It doesn’t matter if I’m power on, power off, in a steep turn, at gross weigh or light, it works every time. However, if I am not in a landing config, say my gear is up or I have 1/2 flaps or no flaps, it will not be accurate because the critical AoA for the ship has changed and the AoA doesn’t know it.

The only non-certified AoA that I know of that can take into account more than one aircraft config is the Aspen software driven device. You can calibrate it for two modes: flaps and without flaps, but the indicator on the 1000 display **always** shows two graphs for AoA, which is confusing and odd (to me).

Bottom line, simple AoA’s are great as long as you respect and understand the limitations.

 

 

 

 

[carusoam]

DVA,

Your point is valid.  I assume the AOA indicator will be out of calibration and alarm early for the other less critical configurations?

Probably a bit annoying using it to land with T/O flaps instead of full flaps, where 5 and 10 extra knots is pretty annoying.

Did I understand correctly?

 

Mike, nicely done.  I'm looking forward to the landing sequences. Your attention to detail and safety make it comfortable to watch.

Best regards,

-a-

[Danb]

Dave this being true would it be worth the effort to change the configurations then calibrate and compare to each other the differences, after knowing the info decide which configuration you desire to have in the plane. Mine was calibrated according to instructions in the BK guide. I'd lean not knowing the how close they may be in differing configurations to setting in up with gear down no flaps, logic being most stall spins occur in the turns downwind to base? In any regard since I've been utilizing the BK for three yrs my approachs are more stable therefore my landings are easier to accomplish 

[DVA]

8 hours ago, carusoam said:

DVA,

Your point is valid.  I assume the AOA indicator will be out of calibration and alarm early for the other less critical configurations?

So “less critical configurations” is one way to illustrate it, another way would be simply, different configurations. I think you’d agree that a clean config in a slow steep turn would also warrant a good stall indication just as much as that turn to final would.

I’ve learned that the different AoAs react to off-calibrated conditions in different ways. I would not generally characterize them to alarm early in those cases, maybe favoring that they will display incorrectly.

Again, it’s all about just understanding the limitations.

Happy New Year!

[bradp]

Seems like a logical progression in the technology would be to have tie-ins for the landing gear and flaps circuit, and calibrate to each configuration state. 

 

-Brad

[DVA]

3 hours ago, Danb said:

Dave this being true would it be worth the effort to change the configurations then calibrate and compare to each other the differences, after knowing the info decide which configuration you desire to have in the plane. Mine was calibrated according to instructions in the BK guide.

So my personal opinion is to always follow the instructions from the manufacturer. For the Garmin, the manual gives me two choices: 1) Set it for final approach over the fence, or set it for approach to landing as on the glide slope. I chose the latter. The former would help with nailing landings at the best speed and the shortest distance and some people would like that help. Don Kaye fixed me with his video, so I chose the approach option. I fly a lot of IFR so having the AoA help me on a stabilized approach in IMC was far more beneficial to me. I literally just toggle my scan on an ILS approach between the HSI on the G500 and the AoA in the corner of my eye. EZPZ - I never look at airspeed or rate anymore, I can concentrate totally on the approach and have my mind set for going missed if needed.

The BK KLR-10 is a two pressure point (LRI) Lift Reserve Indicator that computes AoA. BK and others (like the Alpha Systems which BTW makes the AoA for BK under an OEM agreement) perform the AoA calculations differently than the Garmin. Garmin uses three points of pressure measurements and they claim this helps compute true AoA more accurately at higher speeds and they claim they are a true direct AoA device. I’m not sure how much more accurate it is or if it matters.

A LRI will show proper AoA in most conditions, but in some odd configs like high airspeed high-high angles the pressure data in conjunction with the math used to compute the display behavior will have enough averaging error or skew to show incorrectly on the display. I don’t understand the theory at a low enough level to try explain way, but you can read about that on your own if your interested. Garmin claims they don’t have those issues. IDK.

In any event, all of the devices regardless of manufacturer are great additions to the cockpit. Even if your AoA indication is off a bit in some configs, you can always count on the fact that if it’s rising quickly, you probably should do something about it - right now.

Finally, for those who have the option to set the AoA in different modes, I’d go play with them. I initially set up my Garmin for the over-the-fence setting to see just how much extra reserve I had on landing and I was pleasantly surprised. After I practiced a bunch with it set that way I set it up for the approach to landing setting and I love it.

Happy new year!

[DVA]

50 minutes ago, bradp said:

Seems like a logical progression in the technology would be to have tie-ins for the landing gear and flaps circuit, and calibrate to each configuration state. 

Yep!

The FAA is at the root of that issue. They consider the non-certified AoA’s a non-primary device that should not be relied on for flight, but may be beneficial for situational awareness. I guess we have the relaxed installation rules due to the fact that the install is specifically not complicated.