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I have had a long hiatus (almost 4 years) since actively building a Sonex tail kit and am hoping to get back into it soon. I will try to be as sensitive to this topic as I can, since I know how tight knit the Sonex community is. However, my perception regarding overall safety of the Sonex line has changed somewhat since I first bought Sonex Plans #1398 and started building. What I once viewed as a sturdy little fun flyer with an impeccable safety record, now seems to have had a couple of rough years, safety wise. Obviously, some of that can be contributed to increased numbers of completed aircraft in the fleet, but I'm worried there is more to it. Comparing a search of the NTSB database for "Model: Sonex" vs say, "Model: RV-12", the number is a little concerning. Now, let me be clear, I don't want to build an RV-12. I have come to love the Sonex; it's design philosophy, the way it flies (took a ride in Sonex #199 way back when), and the whole Sonex family, especially the Monnett's. I respect the company and community they have built. The Sonex IS the plane I want to build. But, as a husband and father of 5, I owe it to my family to weigh the risks associated with everything I do. Obviously there is risk in our chosen hobby, but I want to make sure I have done my part to mitigate as much risk as possible.

What are others thoughts on Sonex safety? Has it just been a couple of bad luck years, or, is there something more at play? Is there a common thread running through any of the accidents (engine/carb, structure, etc.)? What can we learn to make each of us safer Sonex builders and pilots?

Josh,

This is certainly nothing that pilots and builders should be shy about talking about (IMO). You are correct in your observation of a bad run of accidents lately. There has certainly been some good discussion about it on this board. As a low time and young pilot, I shared many of your concerns as well.

Just some general thoughts:

-Look over the NTSB reports rather than just the number of accidents, and try to learn from them. It doesn't help to look at the probable cause and say to yourself, "I would never do that", but rather to look at it and say "How can I prevent myself from doing that."
-Evaluate whether or not you feel there are any accidents inherent to the airframe design itself. Of course several of the accidents are still in preliminary, but on first brush it would not seem so.

A disproportionate number of fatal accidents have come from engine failures, either for unknown reasons or from the fuel system. I personally feel that this underlies how critical paying attention to safety in this area is. There is no substitute for sound judgement and using proven methods in aviation. (Anyone who is planning on using a Corvair engine can tell where I get this philosophy from!)

In the end, it is impossible to remove all risk from aviation. But I think that the mere act of posing the questions you are posing speaks to your commitment to development and safety in the field of homebuilding, in order to minimize the risk of human factors where at all possible.

Best,
Mike

If you search the NTSB for RV, you will find a lot of accidents. Simply because there are a lot of RVs flying. Same search using Cessna and you will find a lot because there are a lot of Cessna flying. Sonex has few accidents because there aren't many flying.

The airframe is as safe as any, tough as nails, no bad flight characteristics, will get you safely to the ground if you use your head. But the one thing the Sonex has that other kits don't, is an amateur built engine in the Aerovee in many cases. RVs and Cessnas don't, they use Lycomings. Sure, Jabiru accidents occur, and usually for similar causes, fuel exhaustion or non standard modifications or maintenance. And it certainly doesn't help the situation that the CEO of Sonex was killed in an Aerovee powered Sonex.
I've had an engine out in my Jabiru caused by owner stupidity. I was able to dead stick it back to the runway. Would have happened no matter the power plant. I would fly behind a properly built and maintained Aerovee.
My point is the Sonex airframe is proven. Then engines are only as good as the folks who built them, installed them, modified them and maintain them. And keep enough fuel for them.

Josh,

I will second everything that Mike and John just posted. I would also like to add a couple of more thoughts on the subject.

First, there have been too many instances where the pilot attempted to return to the airport at low altitude after loosing engine power for whatever reason. They did not make it. On the other hand, a few Sonex pilots in recent accidents have maintained control and landed straight ahead and walked away with minor or no injuries, including a couple who landed in the tree tops.

A Sonex stalls at less than 40 MPH. If you loose an engine, that should be no worse than running your four wheeler off a trail at 40 mph, as long as you don't stall and spin. So, do not attempt the impossible turn! I am thinking that because the aircraft is so manuverable, pilots think that they can cheat physics and make a low altitude turn to return to the runway. Train yourself not to give into this temptation!

The second point is there are very few, if any, instances of a catastrophic engine failure in the Sonex accidents. Some are due to maintenance errors, some to improperly repaired engines occurring after a propeller strike. Others are for indeterminate reasons. Whatever the reason, this means that you have to pay attention to detail when you install and maintain your engine. Make sure your engine is getting proper cooling air. Make sure your fuel lines are properly routed and secured. Make sure your engine controls are robust and properly secured, safety'd and routed. Make sure your induction system is properly set up and secure and safety'd. Make sure you fully understand all of the systems and how they work and how to inspect them.

There are no smoking guns in any of the accidents that I can find. Try to learn from the mistakes of others. Try to build in as much safety as you can into your aircraft (styrofoam under the seatpan, seat belts padded with racing should and waist pads, energy aborbing foam in your seat cushions, angle of attack indicator, etc.).

Practice ultra safe flight practices when you are in Phase One and after any modifications. These practices would include using an airport with long runways, flying high, remaining within gliding distance of a suitable landing area, never flying with less than an hour of fuel reserve, only flying in good weather in daylight, etc. Also, make sure you go to the Sonex transition flight training program and maintain your pilot education throughout your flying career.

I wish you the best of luck in your decision and your aircraft building!

Jake

would like to clear up one misconception. An off field landing into the woods at 40 mph is not the same as running a car off a trail at 40 mph. Airplanes have virtually no crumple zones and very little i
in tge way of pilot protection should you hit something. This is true of not just sonex but rv, cessna, pipers, etc. Airplanes are built to be light not to withstand ant sort of impact.

As for the original question, go read the ntsb reports. After reading each one ask yourself if the same thing could have just as likely happened in another aircraft or was there something specific to the sonex. Raw numbers don't mean much without the supporting data.

Keith

Just for the record, I said four wheeler (i.e. Polaris or Artic Cat, Yamaha, etc.) off the trail, not a car. One thing an aircraft has going for it is the wings will offer some protection as they hit trees, bushes, branches, etc and slow down the impact forces.

Jake

samiam wrote:Josh,

A disproportionate number of fatal accidents have come from engine failures, either for unknown reasons or from the fuel system.

Agreed. The Sonex airframe is a damn TANK! You'd have to work awfully hard to damage the airframe. Engines are almost entirely the source of accidents in the Sonex family. That has less to do with the Sonex itself, but rather the installation and maintenance of the power plant. And I believe the EAA statistics show that a disproportionate number of first-flight accidents are due to fuel system errors. That can happen with any engine.

I used to fly single pilot, single engine, IFR at night. But now I have a family and more commitments, so I don't do that anymore. I'm not worried about the airframe; I'm worried about the engine. ANY engine.

As for handling, I find the Sonex a great handling aircraft, without quirks. I can stall straight ahead at 26kts indicated. I'm sure there is pitot error there from the high angle of attack, but the the point is I can go really slow and not have the airplane break to either side, simply by staying on the rudder pedals. I can slip with the flaps up or down, and it glides quite well. When I purposely spin the airplane I can stop the spin in little more than a half turn.

.

I will second that the Sonex airframe is a tank. You can really abuse it and it will not show any sign of it.

If you are able to have controlled flight into terrain at 40 MPH, you should survive with only a bruise to your ego.

If you have some time, go to www.sonexfoundation.com and look up some of the accident database research we've collected. We try to keep it up to date as best as possible.

After digging into the data, the overwhelming majority of all Sonex accidents, both non-fatal and fatal, can be broken down into two categories: Loss of engine power and loss of control.

Loss of engine power can either be fuel exhaustion (it's happened more than once), poor maintenance on behalf of the owner (flying after a prop strike for example), or engine failure for undetermined reasons.

Historically, loss of control accidents occur to people unfamiliar to the Sonex. People who are just beginning test flying their recently-completed airplane, or people who just purchased an already flying airplane may run into this issue.

As others have already said, your best defense against these issues is preparation. Before you fly your airplane, make sure the engine is running properly and you have no mechanical issues. Also make sure you are ready to fly, hopefully by enrolling in the T Flight program or getting flight time in other Sonexes.

Welcome back to the community and I'm glad to hear you're back to building!