Stall/spin accidents in our community

Discussion topics to include safety related issues and flight training.

Re: Stall/spin accidents in our community

Postby kmacht » Fri Mar 03, 2017 11:03 am

Talking about stall/spins here helps raise awareness but I don't think it is asking the underlying question. Why are they stalling/spinning in in the first place? It is pretty rare for someone to stall/spin in a plane on a normal routine flight where nothing else goes wrong. Throw in an engine failure, airframe issues, distractions in the cockpit or doing something stupid like buzzing and the chance of it happening goes up significantly.

I just did a very unscientific look at the NTSB aviation accident database and am worried about what I see. Keep in mind that what is below is just a very broad look at some raw numbers without any analysis or vetting. If I or maybe someone else has some more time in the future it would be helpful to do some categorizing and sorting through the accidents to get a more accurate picture but here are the raw numbers. A search for Sonex/Waiex/Onex shows 39 accident listings. The sonex website shows 571 aircraft currently complete and flying. That gives an accident rate of around 6%. This means that 1 in 20 are getting into accidents of some sort.

I figured that maybe that is the going rate for homebuilts so I then looked at RV's. The RV 10 and 12 have the closest completion numbers to Sonex. The RV-12 has 496 completions with 6 accidents and the RV-10 has 821 completions with 12 accidents listed in the database. That gives a 1.2% and 1.4% accident rates or 1 in 75.

I'm positive those numbers when refined will change some but this post isn't about getting exact numbers. What I am more interested in is why the sonex line appears to have such a high accident rate and is there anything we can do to lower it.

It can't just be builder error as two factory aircraft are now included in those numbers. It isn't flight experience as the accidents have included both low time and very high time pilots. Other than the one Waiex with questionable build practices I don't think there have been any reported issues with the airframe. There has been lots of talk about engine issues, carb issues, etc on the forum so maybe there is something there. Could it be as simple as the Sonex product line taking off over the past few years and more aircraft are in or just out of the phase 1 flight tests where issues are most likely to crop up? Maybe it has something to do with how the plane stalls. Mine stalls so gently that it is easy to ignore it as you get close to the actual mush/break and I'm not sure I would recognize it in time if distracted while maneuvering low to the ground. Maybe it is something else that we haven't even discussed in the forums here yet.

I don't think the answer is going to be as easy as finding one single re-occurring cause in the statistics. If it was then it would have been fixed by now. What I think we need to do as a group is start looking for what can be done to make our flying safer. A few people have suggested LRI's which I initially thought I didn't need but after reading some of the posts here am reconsidering adding one to my plane. Maybe a dedicated forum section or thread to post up engine issues found while building or after flying for a while. Not a post asking for help but a post to just documenting things you have run into so others can see and learn from them. How about an annual condition inspection thread or forum? Post up what you have seen or found during your annual inspections. What works during the initial build may not be holding up after a year or two. Maybe a "never again" type section where people can post up anonymous things that people have experienced/done in their sonex that others could learn from.

I would urge the sonex foundation and other builders to think about what types of things can be done here to help improve the accident rate. The sonex product line has matured a lot since the early days of building from a set of plans and some bent channel. The actual building issues are far fewer than they were even 5 years ago. It is time to start focusing on how to support the flying fleet out there so they stay safe and reverse the reputation that the Sonex is starting to get outside of this forum.

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Re: Stall/spin accidents in our community

Postby gammaxy » Fri Mar 03, 2017 12:12 pm

I think the LRI is useful, but it's not clear to me how it would make stall/spin accidents in a Sonex less likely.

I was practicing accelerated stalls yesterday and the ASI was indicating ~45mph at the stall which is about what it indicates during normal stalls. For my load factor, I would have expected to see ~80+mph on an airplane with a more typical pitot/static system. It seems that by placing the static port below the wing, the Sonex ASI already acts somewhat like a LRI in that the airplane stalls at approximately the same indicated speed regardless of positive load factor (at the expense of the indicated altitude being incorrect during the maneuver).

My point is, I doubt people are stalling or spinning while their ASI is reading typical approach or departure speeds. I don't see how the LRI would remedy that problem.

A year or so ago I did some limited research into stall horns. The impression I got was that the fatal accident rate in certified aircraft decreased significantly about the time they became common. Unfortunately, it's basically impossible to know whether the cause of the decrease was actually due to the stall horns--the pilots they save likely never realize the horn saved them. I remember hearing the horn a couple of times during my training while practicing emergency off-field landings. I do feel like there might be some value in making stall horns more common on Sonex. Personally, I'd like one a little nicer than the "on-off" buzzer style. I'd like one that changes tone or intensity as I get closer to the stall.
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Re: Stall/spin accidents in our community

Postby radfordc » Fri Mar 03, 2017 2:44 pm

I doubt that any cockpit instrument will ensure pilots don't stall and spin when they are under stress...such as experiencing engine problems. Instinct is hard to overcome....and it seems instinctual to pull back on the stick when the ground is coming up fast. Training and experience should be the answer. I know that I felt better able to deal with engine problems after having flown ULs for over a 1000 hours and having many, many engine out landings...both intentional and otherwise. It sure helped when I had to make an engine out landing in a Sonex. Glider pilots make a deadstick landing every flight and seem to be OK with that. Do you suppose that if actual engine off landings were a required skill that stall/spin accidents would decline?

I think the first reaction to a serious engine problem could be "shut off the mags and fuel and fly the airplane". I doubt many pilots would agree, and it seems more common to focus on the engine issues and not so much on flying the plane.
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Re: Stall/spin accidents in our community

Postby Bryan Cotton » Fri Mar 03, 2017 3:16 pm

How many of ur regularly practice slow flight, stalls, and spins? When I used to tow and fly gliders, it was a ton of slow flight. I did often practice stalls in everything I flew. I am overdue on spin practice. I don't subscribe to the modern theory of stall awareness. Go out and do them.
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Re: Stall/spin accidents in our community

Postby vwglenn » Fri Mar 03, 2017 3:36 pm

The single biggest thing you can do is to practice before it happens. Being prepared for the worst will help you when the worst comes. Studies have shown that mid to higher time pilots are more apt to make pilot error mistakes. Low time pilots and ATPs are less likely.

I don't think the comparison between the RV-12 and the Sonex is a good one when you're talking about stalls and spins. It's simply a pilot thing which, as eluded to earlier, is something of an intangible and won't be known until the length of time the -12 is in service becomes equivalent to the Sonex. Until you can look at it over the same time interval or overall hours in service, that probably won't ever come to a realistic comparison.

The thing that concerns me is not the pilot error issue but the engine failure issue. Specifically engine failures in the same regime of flight...on takeoff and climb with no definitive information as to why. This is the most deadly time to lose that engine and probably the hardest to fight your alligator instincts to get back to the runway or avoid the ground by pulling back on the stick and spinning it in. I would say this is the area that needs the most scrutiny. Using the number of accidents (39) mentioned above as a base line, I would say a half of those could be tracked back to a verifiable cause or contributing factor which makes the accident explainable and either preventable or simply a freak occurrence. Half of what's left (8 or 9 of 20) happened while in takeoff/climb regime of flight with bad results and no explanation. This looks like a trend to me. I'm now hyper aware and mentally prepared every time I swing out onto the runway.

Is it going to stop me from flying my Sonex? Nope.
Will I take extra steps to mitigate potential pit falls? Yep.
Am I scared? Nope. Not until there is something to be scared of.

I'm infinitely more frightened of people staring at their phones while driving and much much more likely to die as a result. I still drive my car everyday.
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Re: Stall/spin accidents in our community

Postby fastj22 » Fri Mar 03, 2017 11:12 pm

A LRI or AOA gauge will not by itself save you from spinning into the ground. All it will tell you is when the wing won't continue to fly. If you pay attention to it, it might allow you to walk away. If you don't have one, or choose to ignore it, who knows.

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Re: Stall/spin accidents in our community

Postby LarryEWaiex121 » Sat Mar 04, 2017 11:00 am


I agree with most of your post.
Again, I go back to the engine failure rate and our accident rate in the Sonex community. I don't have the resources to definitively say what is the main cause but suspect that fuel/carburation matters play a part in many of the accidents.
The comparison to the RV line is interesting in the initial numbers breakout. I would say without hesitation that the biggest reason that the raw numbers show this spread is hidden in a couple of well known facts. One, the RV 10 airplanes in particular, are very routinely "professionally built" by contractors and not some guy in his garage. Two, they are using either certified engines or copies of certified engines with essentially everything except the pedigree.
Its a shame we don't have a certified engine at affordable cost for the Sonex line. Unfortunately, the cost, simplicity matter all force choices on us as builders. Personally I do all I feel that I can to keep my machinery up to snuff. I do my routine maintenance, I do my leakdown tests, etc. Beyond doing your due diligence its difficult to predict other issues.
In the end, one has to approach every flight with a healthy caring for the unpredictable and have your head screwed on with a plan. Easier said than done but, we all as a group have to try a bit harder. The numbers are kinda ugly.

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