AOA
Posted: Wed Nov 24, 2021 3:35 am
by Kai
Mark’s latest safety posting:
Now I am confused (nothing to worry about- it happens every now and then).
A while back we had a few isolated cases in this country with people falling out of the sky, alas some fatal, although none Sonex. Since those dangerous LSA’s and the maniacs flying them are always in our authorities’ focus, the discussion about an approved mandatory audio stall warning device installation at least à la the ‘Cessna Switch’, in all LSA’s came up. It went so far that I had to get in touch with Sonex Tech with an inquiry about the installation of such a device in the Sonex/Waiex range.
Let it be said that I persoally hated the idea. Having all and sundry throttle jockeys hacking away at their wing leading edges for openings to fit the contraption, not to mention suddenly having som 400 aspiring test pilots falling out of the sky, was certainly less of a temptation.
To nobody’s particular surprise and my intense relief the answer came back that sorry, we can’t help, no research data available, no test installation completed, do not open up/puncture the wing structure- especially not the wing leading edge, etc, etc. Which all was what I wanted to hear.
BUT
Now Mark writes something along the lines of:……. This reinforces the need for all builders of homebuilt aircraft to install an AOA device, preferably with an acoustic signal…….
That’s news! Is this the new Sonex policy?
If so- is there anything available from Sonex, i.e. tests, recommendations, installation, equipment??
Thanks
Kai
Re: AOA
Posted: Wed Nov 24, 2021 7:32 am
by GraemeSmith
I don’t think I was around to hear that.
Things change. The FAA started actively promoting AOA installations for GA in 2015:
https://www.faa.gov/newsroom/faa-and-ga … e-campaign.
And the planes are EXPERIMENTAL - meaning you can buy any of the products now on the market and try them yourself (or choose not to). Many of the EFIS vendors are now including AOA sensing built into their pitots. You can make your own to either work with your EFIS or even use a simple pressure gauge and a couple of tubes and calibrate it to create a “Lift Reserve Indicator” which is a form of AoA.
Heck even the quite old MGL ENIGMA will generate a “virtual” AoA without a probe after you fly it through a calibration routine.
Have at it and find out what the many vendors are offering. But don’t beat on Mark and Sonex - IMHO that’s not fair.
Re: AOA
Posted: Wed Nov 24, 2021 9:36 am
by Sonex1517
The Sonex Builders and Pilots Foundation has an article on building your own LRI. I have one in my Sonex and it is a great tool for reference.
https://img1.wsimg.com/blobby/go/e83c7c … 4222140376
Re: AOA
Posted: Wed Nov 24, 2021 10:05 pm
by karmarepair
Kai wrote:Mark’s latest safety posting:
<snipped - RRY>
BUT
Now Mark writes something along the lines of:……. This reinforces the need for all builders of homebuilt aircraft to install an AOA device, preferably with an acoustic signal…….That’s news! Is this the new Sonex policy?
I didn’t read Mark’s message that way.
It felt like a bit of reaction to Graeme’s work on accidents and incidents, which I at least found a little dis-heartening. I saw Mark opening up a dialog, and engaging with one of the Homebuilt world’s most studious and careful compiler of accident statistics. My take aways:
- Sonex accident rates are roughly in line with other experimentals.
- Experimental hours flown are going up, and the accident rate is going down.
- We as a community can still do better, and AOA indication is one of the things EAA is looking at, in an industry working group, which Sonex is a part of.
AOA indication has been a feature of general aviation for a LONG time. The vane type sensors were invented in the 1940s. Reed type stall horns have been installed on every Cessna 100 series since, what, the 1970’s? But even these simple AOA indicators (“Idiot Lights” rather than gauges) are rare in homebuilts, including Sonex, even though Tony Bingelis described how to do it back in the 1980’s (https://www.eaa.org/eaa/aircraft-buildi … ng-devices?), and there have been several articles in Sport Aviation and Kitplanes since then. I, for one, think we can do better, and it sounds like Sonex feels that way too.
That alone is not going to make Experimental aviation as safe as walking to the corner mailbox (I wish we had a better system for transition training, but I know that various people are working on that issue), but it’s a step.
As to myself, the next time I fly the aero club’s Cherokee, we are going to practice engine out during climb scenarios, by establishing VsubY climb, and then pulling power, and pitching down to establish VsubG. I’m also going to see if I can arrange some instruction in a local low wing LSA, and practice the same maneuvers.
Re: AOA
Posted: Thu Nov 25, 2021 2:19 am
by Kai
No,
No beating on Graeme or Sonex intended!
Our predicament was indeed before 2015. The issue was that should one decide to install a stall warnng or AOA device, it should be something that Sonex had tried out and tested. Our national CAA was horrified at the thought of self proclaimed test pilots scooting around and testing either something they had dreamed up themselves, or storebought something that they thought looked good. Since this was going to be mandatory safety equipment, what they wanted was something that was developed and tested by a reputable manufacturer for the specific aircraft.
The idea of a RLI of course came up- however: it is not acoustic, which was an absolute requirement. ASAS had a spoon operated switch in their program intended for Vans aircraft, which looked promising. However, Sonex had (at least back then) no experience with it and could consequently offer no installation advice.
I would be very interested if something was coming along in the Sonex pipeline.
Thx
Kai
Re: AOA
Posted: Thu Nov 25, 2021 9:02 am
by SonexFactoryTech
Kai wrote:To nobody’s particular surprise the answer came back that sorry, we can’t help, no research data available, no test installation completed, do not open up/puncture the wing structure- especially not the wing leading edge, etc, etc. Which all was what we wanted to hear.
The specific question Kai asked of us on October 23, 2015 and our specific answer is here:
Kai:
“The AD will require at least the installation of an inexpensive audio stall warning system (not necessarily an AOA). The question is if Sonex has any experience with such systems- any recommendations, operational and installation?”
Sonex Aircraft Tech Support:
“We do not have any direct experience here at Sonex with any sort of stall warning system. However there may be some experience within the Sonex builder community. You may want to post the question on the builder forums at www.sonexbuilders.net and see what kind of response you get there.”
I feel the actual exchange is somewhat different than what is portrayed in Kai’s post.
We had tested an audible stall warning system that never came to fruition. My personal airplane was fitted with an LRI AOA (non-audible) from its very first flight in 2004. I spoke of it positively at every builder workshop. I spoke of it positively at every AirVenture forum I delivered. I spoke of it positively in every one-on-one conversation I’ve had with builders when the topic came up. We have NEVER discouraged the use of AOA instruments but we will NEVER offer specific advice on third-party products for which we have no experience. We will offer specific advice against doing things that may compromise the structure and safety of the airframe. For instance, cutting out the leading edge anywhere but between the most outboard ribs is ALWAYS discouraged for any reason, even the installation of an AOA/Stall warning system.
Use the information provided on this forum with caution, particularly when it invokes an indirect quote of what “Sonex” said.
Sonex Aircraft Tech Support
Re: AOA
Posted: Thu Nov 25, 2021 10:03 am
by DCASonex
Since most all of us wear some form of headset when flying, any auditory alert need to be made through the audio panel and to override any other input. personally I would prefer an nice bright light to any audio alert, but currently only have the gauge on my LRI.
David A.
Re: AOA
Posted: Thu Nov 25, 2021 10:11 am
by Scott Todd
Lets stir the pot a bit. There is nothing wrong with using AOA. Many people like them and think they help in some way. But lets face it, most of the airplanes out there don’t have one. There is a simple alternative already built into the Sonex family of airplanes. LOOK OUT THE WINDOW. Try practicing engine outs and don’t let the nose go above the horizon. I’ve been teaching this for nearly 30 years. Feel the stick force. Practice, practice, practice. If it ever quits, LOOK OUT THE WINDOW. If the nose doesn’t go above the horizon, it won’t stall. I know, what about turning? Well in those shallow turns, which you should be shallow in an emergency, the nose STILL shouldn’t go above the horizon.
Now that I’ve calmed down…In a well maintained airplane with simple systems, like a Sonex, if it quits, its something bad. They never quit at several thousand feet, and if it does, run the checklist. They mostly quit when you are low. Don’t they Lou? Most likely you won’t have time to run the emergency checklist, put the map away, or even tighten the seat belt. You shouldn’t be distracted by ANYTHING in the cockpit. You need to immediately focus on flying the airplane to that clearing or road. It may not be the best glide speed but with a little practice, it will be close and you won’t stall it. I like to teach the nose NEVER goes above the horizon unless in the final flare. Aerobatics or playing is different.
There will be haters but don’t hate until you go out and try it. Just don’t let the nose go above the horizon. It works.
Re: AOA
Posted: Thu Nov 25, 2021 11:14 am
by pappas
I agree with Scott. My trouble started at 3500 MSL, which is about 2400 AGL in that area of the desert. Still, my final touchdown was between 6 and 7 miles away from the point I turned towards my intended landing area and I was trying to burn off altitude by slipping pretty hard at the end.
I reviewed the flight data from the Dynon and I did not maintain a constant max glide speed. (I wonder if I was more nervous than I remember?) Nah!.. Probably could have made over 7 miles altogether if I needed to and was more attentive to my airspeed.
Keeping the nose below the horizon is really good advice. I also like to look at the wingtips. As long as they are flat with the horizon, I am at pretty close to best glide.
Re: AOA
Posted: Thu Nov 25, 2021 3:42 pm
by Kai
Regarding the Sonex Factory Tech posting above- right on the button and I can offer no argument! I have neither any wish nor intent to enter any sort of discussion with either them or the rest of the staff. They have always provided the help and assistance I sought to my full satisfaction, which I hope will remain so.
However, our predicament back in ‘14/‘15 was, that the Dept of Transportation controlled CAA, more or less demanded an immediate mandatory installation of a ‘fit and forget’ acoustic AOA (or, more precisely, at least an acoustic stall warning device) in all operational LSA’s. Something the airplane manufacturer had tested, knew would work, and could recommend. And, mind you, absolutely not anything found on builder’s networks.
Now, there are seven flying Sonexes in this country (not a lot). All 7 owners, who had flown their aircraft successfully and without the slightest difficulty for years by looking out of the window every now and then, heaved a sigh of relief when it became clear that Sonex as a manufacturer did not have anything finished, tested, and recommended to offer- which meant that we 7 were let off the hook as the airplanes were all built according to a loophole (oversight?) in our national LSA regulations- the 51% rule, and were consequently excempt from anything mandatory. None of us had the slightest interest in starting private development work- which by the way and as mentioned previously, the CAA would not allow.
So, our Sonex SW/AOA problem went away, at least for those already on the register- sort of. For what then happened was that the CAA (always heavily influenced by what happens in the US) rewrote the regulations which they dumped on our heads: all LSA’s, either assembled by manufacturer or homebuilder, to be granted a permit to fly after May 1, 2016, now must have this confounded device. If the finished factory built airplane, or the construction drawings for that matter, do not include this SW/AOA thing: sorry- no permit! To put it carefully, the admission of new LSA’s has dropped significantly since then.
Hence my interest in anything Sonex has, or is planning to develop. The ways of official bodies are indeed not always the easiest to comprehend.
Thx
Kai
Re: AOA
Posted: Thu Nov 25, 2021 6:53 pm
by lpaaruule
I agree with the plan to keep the nose below the horizon. In an emergency hopefully a pilot would be intensely focused, maybe so much that an audible alarm would go unnoticed (I think that it where a stick shaker helps)
I wonder if distractions such as shown in this AvWeb video are more applicable to the use of an AoA indicator.
Re: AOA
Posted: Fri Nov 26, 2021 11:54 am
by jerryhain
[quote=“Scott Todd” I know, what about turning? Well in those shallow turns, which you should be shallow in an emergency, the nose STILL shouldn’t go above the horizon.
[/quote]
I agree, with the sole exception being you have the altitude to do a 180 back to the runway, bank angle should be 45° plus or -5. Less than that you fly too far away and you may not get back to the runway, more than that you’re just giving up altitude.
Re: AOA
Posted: Fri Nov 26, 2021 12:32 pm
by Scott Todd
If you’re turning back, you’ve decided you have the altitude and/or speed to make it. If you have the altitude, it will be a descending turn. If you have the speed, it should still be a descending turn. Either way, the nose shouldn’t come above the horizon. If it does, you’re too slow. I teach it all the time and the critical teaching point is to keep the nose below the horizon. As a teaching point, its about avoiding stall/spin. Some people, usually the STOL crowd learning back country and short unimproved strips, really master the turnback and we start to push the limits. This is where AOA helps. But the average reader here is a long way from this. Especially in a Sonex!
Re: AOA
Posted: Fri Nov 26, 2021 1:36 pm
by rick9mjn
to add my 2 cents… about the using a AOA and doing the impossible turn. everyone should go for 2 glider flights and one of them being a rope break, and it being winter time in the US. another idea, is to a GOOGLE search on u tube for “glider rope break”
…good day…/ rick
Re: AOA
Posted: Fri Nov 26, 2021 3:13 pm
by markschaible
Hello All,
Great discussion on AOA and flying technique! I’m breaking from my norm in replying directly to this thread vs. to the Sonex posts section where I want to begin creating a permanent archive in the Sonex posts section on these topics so that folks can quickly see “what the factory says” beyond what’s on our web site. We will write-up something on the topic of AOA to post to the Sonex section for that purpose. I do want to reply directly to this thread today in a more casual manner on a number of areas to keep the momentum of positive dialogue going!
Regarding AOA and stall warning devices, at the EAA Safety Committee we are at the very beginning stages of organizing a new outreach and education campaign to promote the wider use of AOA devices in EAB aircraft, and as I mentioned, we are advocating for devices with audible warnings because you should be looking out the window, especially in some of the most vulnerable scenarios in the traffic pattern. I also recall a conversation a few years ago about there being a number of loss of control accidents involving pilots practicing turns around a point.
There are a lot of great native solutions in most modern avionics packages nowadays, including our in-house favorite MGL Avionics, to add AOA capability to your aircraft, in many cases with the option for audible warnings. Admittedly, we haven’t done much of anything with AOA at the Sonex factory because AOA pitot probes are really expensive, and we like the simple and inexpensive pitot-static probes that you can get from Aircraft Spruce. We do have a unique one-off pitot-static-AOA probe on “Sharky,” our gray-colored SubSonex prototype with the shark mouth nose art. The probe is retractable to help avoid people spearing themselves on the nose cone mounted proboscis, and has ports for pitot and AOA with static holes on each side of the probe. We haven’t even really done much with that, however, as it would be an expensive little bugger to produce and sell with the retractable feature. Hmm, maybe we should do a simpler non-retractable version suited for under-wing mounting as a new, inexpensive AeroConversions product – literally just had that thought today, so don’t start pressuring us for it yet – there’s never enough hours in the day!
As Kerry mentioned in his earlier post, we dabbled in stall warning/AOA warning devices probably about 10-15 years ago when AOA wasn’t such a standard feature in avionics. We had a concept for a simple and tiny single port probe to put on the wing, connected to a little plastic box about the size of pack of cigarettes that took a 9 volt battery. It had a calibration button, and the concept was that it would give an LED light stall warning, and I think we were also thinking about an audible warning at that time as-well. That project hit a stop when we had trouble with the performance of the probe design and other, more pressing R&D and customer support priorities got in the way. I still think that concept is a great one, especially with the modern advances in bluetooth technology, and if produced inexpensively with a probe design that actually works, would be a fantastic low-cost retrofit for all kinds of homebuilt and ultralight aircraft, especially those that do not have avionics outfitted with native AOA capability. With the nightmare that is the electronics supply chain right now, don’t hold your breath for anything along those lines to come from Sonex or AeroConversions any time soon, although it would be cool if we could eventually pick that project back-up. If someone wants to beat us to it, I won’t be upset as I think it would be a great safety-enhancing product for sport aviation if done right.
I’m not sure if it was specifically mentioned in this thread, but I believe it was the general focus of the tech support conversations with Kai: the Van’s Aircraft AOA port installation. This involves popping the mandrel out of a rivet in the top of the wing forward of the main wing spar and connecting your AOA air data port to the back side of that blind rivet. According to Van and his customers, it works great. The drawback in our assessment is that it requires cutting an inspection plate hole in the bottom of your leading edge skin, and for structural reasons we never recommend cutting holes in the D-tube section of the leading edge unless it’s done in the outboard-most rib bays of the wing. I’m also not sure how they avoid creating a water trap in that installation with a downhill section of air data tubing – I’ll have to ask Van the next time I talk to him, or maybe some of you are familiar with the installation and can enlighten me and the group.
Of course, being homebuilt aircraft, any AOA or stall warning device, even those that include factory instructions or are otherwise “factory blessed” must be calibrated by the builder during the Phase I test flight – there’s pretty-much no getting around that, so don’t expect your stall warning or AOA to be accurate on the first flights of your aircraft until you calibrate the system. That’s an important point that it seems people don’t always think of, and it’s a great point to argue with those foreign agencies wanting “factory” AOA systems: These are not factory-built production aircraft, so no AOA system installation is going to come without customer flight testing & calibration, therefore ANY reputable AOA product on the market should be considered acceptable to foreign CAA’s regardless of whether the aircraft designer has experience with them. Of course, that doesn’t mean that foreign CAA’s are going to accept the logic of that argument.
Also a great discussion in this thread about flying technique, although I wouldn’t take the leap in logic to say that we shouldn’t also be looking to develop, improve and install AOA devices as another tool to help improve safety. As always, Paul Bertorelli is spot-on with his video about flying and avoiding distractions in the pattern. Incidentally, we had the unique opportunity at Sonex to name one of the roads in our neighborhood, and we named it Red Tail Way because of the family of red tail hawks that live just on the other side of our airport gate on Hughes Road. One of them has even soared with the factory Xenos motorglider a few times.
If you subscribe to Kitplanes Magazine’s Homebuilders Portal newsletter, you may have seen that they reposted this great article about forced landings during traffic pattern operations yesterday: https://www.kitplanes.com/the-dawn-patrol-26/
Although a Sonex doesn’t have the challenging aerodynamics of these WWI replica homebuilts, there are some really great lessons to be learned in this article. I have to admit to becoming a member of the “Combine Service” myself, as I had a forced landing into a cornfield in the Rotax 447 powered ultralight that I own last year. I had a partial (almost total) loss of power on initial climb-out and it was an immediate pitch-down input and literally talking to myself out-loud to resist the temptation to attempt a turn-back that allowed me to walk away without a scratch. I was also fortunate to have landed in a bare-spot in the late-summer tall corn and although I wiped-out my landing gear and spent all of last Fall repairing the aircraft, at least I didn’t do more damage by getting into the tall stuff which I really feared would have flipped me over.
Speaking of turn-backs, many of you are aware that there is a Turn-Back Project in-process right now, in-which a couple members of the EAA Safety Committee and members of other groups are taking a scientific approach to “The Impossible Turn.” I personally have mixed feelings about this project because I believe most pilots won’t get away with it in a true emergency situation even if they had spent time practicing it at-altitude under a controlled and non-emergent setting, but I do have to admit that the work they are doing is extremely interesting and will ultimately prove valuable in some ways. For those of you who have done some of this practice in their Sonex, it can be a great and very informative exercise. I just wouldn’t be too quick to try to duplicate the maneuver in an emergency.
One very interesting tool that a member of the Turn-Back Project group is working to develop is an app called “Takeoff Advisor.” Takeoff Advisor is intended to be a preflight tool for your phone or tablet that will take information about whatever airfield you’re about to depart from, combine it with current weather information and some test flight data that you will enter for your specific aircraft, resulting in a graphical display of various options that you will likely have in the event of a loss of power on initial climb-out, including predicted results of all possible pilot actions to cope with the emergency in order to help determine your best chances of success. I’ve seen an online demo of this tool in one of our meetings and I love it. Although it does include possible turn-back scenarios which again, I’m not a big fan of predicting success there, I love it because it shows when turn-back is REALLY a bad idea, and it also shows your predicted chances of executing a forced landing in all other possible locations and which would most-likely be the best choice, whether it be an adjacent runway on the same airport, a taxiway, a field, road, etc. Using this tool during your preflight gives you a plan of action to prioritize your options of where to go should you find yourself in a takeoff/climb-out emergency.
I understand from recent updates from Turn-Back Project members that there are currently some tech challenges associated with correcting flight test data taken at-altitude and under different weather conditions to predict performance at pattern altitude and current weather. I do hope they persevere and can successfully overcome this challenge to bring the Takeoff Advisor to fruition. Aside from the whiz-bank technology itself, I really love it because it makes you THINK about this scenario during your preflight, before you even leave the ground.
Whether we have a tool like this or not, we should always be thinking about where to go and what to do in that situation on that specific day from that specific runway with the current weather conditions, and the current conditions of the crops on nearby fields! Whenever I’m driving my car in the areas that I typically fly (and subconsciously when driving anywhere at all it seems), I constantly find myself looking at fields and roads and stands of trees thinking about what crop is currently in a given field (it’s not always easy to tell from the air), how muddy a field is and how rough the furrows are, how much room there is between ditches and tree lines, etc. for a forced landing site. This is on my mind maybe because of my experience last year, or because I’m just far more-likely to find myself in that place in my ultralight, or maybe because I’m also constantly but not seriously looking for a good piece of property to put a house and a grass strip. Regardless, it’s kinda fun, and probably good practice. If you decide to make that part of your driving habits as well, just remember to always Drive the Car, Drive the Car, Drive the Car!