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Marc W

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One of our EAA members flies a Sonex with a VW engine and a Zenith 750 with a Continental O-200. He just got his annual insurance bill. The insurance for the 750 is higher than the insurance for the Sonex. Both are two seat airplanes. The Sonex is a taildragger and has the VW engine. The Zenith is a nose dragger with a Continental. It doesn't make sense.

He called the insurance company to see if there was a mistake. They told him no mistake. Zenith 750's have a higher rate of engine failures.
 

BJC

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Wanttaja

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One of our EAA members flies a Sonex with a VW engine and a Zenith 750 with a Continental O-200. He just got his annual insurance bill. The insurance for the 750 is higher than the insurance for the Sonex. Both are two seat airplanes. The Sonex is a taildragger and has the VW engine. The Zenith is a nose dragger with a Continental. It doesn't make sense.

He called the insurance company to see if there was a mistake. They told him no mistake. Zenith 750's have a higher rate of engine failures.
My own results are different, with the CH-750s having power issues in ~35% of its accidents, and Sonexes at 50%.

However, the Sonex *does* have a lower fleet accident rate (number of accidents vs. the number of aircraft). The 750 has a much lower fatality rate, though.

At the company's request, I did an in-depth analysis of Sonex accident rates and causes. You can find it at:


Ron Wanttaja
 

Vigilant1

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One of our EAA members flies a Sonex with a VW engine and a Zenith 750 with a Continental O-200. He just got his annual insurance bill. The insurance for the 750 is higher than the insurance for the Sonex. Both are two seat airplanes. The Sonex is a taildragger and has the VW engine. The Zenith is a nose dragger with a Continental. It doesn't make sense.

He called the insurance company to see if there was a mistake. They told him no mistake. Zenith 750's have a higher rate of engine failures.
My own results are different, with the CH-750s having power issues in ~35% of its accidents, and Sonexes at 50%.

At serious risk of being in error, 2 questions/observations:
1) The insurance companies have access to information on the accrued flying hours for the aircraft they insure, right? (my insurer asks me this every year). So, they can do something that is very hard for the FAA, Ron, or just about anyone else to do: Make a direct calculation of accidents and losses by type per flying hour. If they say they are experiencing more engine-related losses for one type over another, I'd think that is useful information

2) If power loss accompanies 35% of CH-750 accidents and 50% of Sonex accidents, that doesn't necessarily mean the Sonex engines are less reliable than the engines in the CH-750 fleet. If, for example, the total number of CH-750 accidents is twice that of the Sonexes, then it means more engines in the CH-750 fleet failed than Sonex engines did. Similarly, the Sonex "percent of accidents with engine failures" could be "improved" if the aircraft had treacherous handling that caused a lot of them to crash for non-engine related reasons. Further (getting back to the point above), we'd need to know the hours flown by each fleet to make a direct statement about per-hour engine reliability (though Ron has some good secondary methods of inferring fleet hours).

Ron, thanks again for the important work you do.
Mark
 
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Wanttaja

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At serious risk of being in error, 2 questions/observations:
1) The insurance companies have access to information on the accrued flying hours for the aircraft they insure, right? (my insurer asks me this every year). So, they can do something that is very hard for the FAA, Ron, or just about anyone else to do: Make a direct calculation of accidents and losses by type per flying hour. If they say they are experiencing more engine-related losses for one type over another, I'd think that is useful information
I'd love it if we could get the insurance companies to turn loose some of their data on flying hours. May ping EAA to see if they can talk the companies into releasing such data with the any information that could trace to individual aircraft or owners extracted.

The only thing is that the insurance companies are generally very protective of their data...
2) If power loss accompanies 35% of CH-750 accidents and 50% of Sonex accidents, that doesn't necessarily mean the Sonex engines are less reliable than the engines in the CH-750 fleet. If, for example, the total number of CH-750 accidents is twice that of the Sonexes, then it means more engines in the CH-750 fleet failed than Sonex engines did.
I should be clearer in my methodology.

My process identifies how many accidents occur to a given type, then determines how many of those accidents are due to engine issues. So the actual *number* of accidents is immaterial...except in cases where there are a low number of accidents.

So for the ~22 years covered by my database, there were 56 Sonex accidents, with 28 accidents due to power loss. There were 34 CH-750 accidents (the 750 got introduced late) of which 12 were due to a loss of engine power. That's where the 50% and 35% came from.

Now...what do we count as "power failure" in these cases. I actually can calculate this about a half-dozen ways. The statistics above are for loss of engine power *for any reason*... including the pilot running out of gasoline.

Another way I calculate it is based *only* on whether it was related to mechanical issues with the engines, OR whether the cause of the power loss was undetermined. Using this method, the percentage of power loss cases drops to 39% for the Sonex, and 29% for the Zenair CH-750.

I can also calculate it based on leaving out the "undetermined" cases, or cases where the engine issue was the primary one, and leave off cases where some other issues contributed.

But it doesn't make that much difference. Like I said in the earlier posting, the issue is the reliability of the engine *package*.

I run these analyses as a hobby, and one thing that makes it worthwhile is discovering some fundamental issue that was not previously known. One of these is the revelation that homebuilt aircraft *type* doesn't make THAT much different to accident rate...that the primary driver is the type of engines installed. And so far, traditional engines (Lycomings, Continentals, etc.) are the winners in the reliability sweepstakes.

Take those 34 Zenair CH-750 accidents. Eight of the aircraft mounted traditional engines, another 11 included purpose-built four stroke engines (Rotax 912, Jabiru, etc.) and 11 more had auto-engine conversions (which I include the Aerovee).

The Sonex? No traditional engines, 20 purpose-built four strokes, and 26 cases with auto-engine-derived powerplants. Three of the accidents with the purpose-built four strokes were due to engine issues (based on my second definition above), but 14 of the auto conversions.

Similarly, the Sonex "percent of accidents with engine failures" could be "improved" if the aircraft had treacherous handling that caused a lot of them to crash for non-engine related reasons.
Certainly. This is the kind of finding I was originally hoping to find in my analysis, but, again, it's kind of obscured by the engine reliability issues.

The difficulties of performing deadstick landings on high-drag airplanes like the CH-750 have previously been noted in this thread. About ten years ago, the FAA released Advisory Circular AC 90-109, "Airmen Transition to Experimental or Unfamiliar Airplanes." Appendix 4 addresses the issues and suggested training for high drag/low-inertia aircraft. I was on the committee that wrote the AC, and actually was the author of Appendix 4.

Ron Wanttaja
 

b7gwap

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Data will set you free.

For me, hanging a Lyc is peace of mind, but ultimately, after phase 1 is complete, some of the first flying I plan to do in my 750 is practicing power off landings. Stalling at 35 mph is a blessing in such a situation from a survivability perspective, but the drag to inertia ratio is not something that leaves the pilot very many choices of landing site depending on altitude. I need to build that tactile and sight picture as soon as possible in the flight test regime.

thanks everyone, safe flying.
 

TFF

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I think a Zenith owner might stick their noses in different places over a Sonex, but a bigger plane might be better if you are being taken for an unexpected ride. I think some of the outcome to this is biased to expected mission. There was someone who was using a single seat biplane for his fishing trips in the Pacific Northwest. Nothing too crazy, but he was meeting up with people on gravel bars. There is another small biplane in Alaska on bush wheels. Where does that go with classifications if something goes wrong?
 

Vigilant1

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I'd love it if we could get the insurance companies to turn loose some of their data on flying hours. May ping EAA to see if they can talk the companies into releasing such data with the any information that could trace to individual aircraft or owners extracted.

The only thing is that the insurance companies are generally very protective of their data...
Having that flying hour information ("the denominator") would let folks make better choices, reduce crashes and save lives.
A cynic might say an insurance company has no vested interest in releasing proprietary info ("it degrades any competitive advantage that this actuarial info provides a company") or even any interest in reducing losses (" they are already included in the insurance premiums"). But, eventually, higher insurance premiums induce more owners to " go bare" or to just stop flying, and both of these actions result in lower revenues for insurers.
 
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Pops

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I'd love it if we could get the insurance companies to turn loose some of their data on flying hours. May ping EAA to see if they can talk the companies into releasing such data with the any information that could trace to individual aircraft or owners extracted.

The only thing is that the insurance companies are generally very protective of their data...

I should be clearer in my methodology.

My process identifies how many accidents occur to a given type, then determines how many of those accidents are due to engine issues. So the actual *number* of accidents is immaterial...except in cases where there are a low number of accidents.

So for the ~22 years covered by my database, there were 56 Sonex accidents, with 28 accidents due to power loss. There were 34 CH-750 accidents (the 750 got introduced late) of which 12 were due to a loss of engine power. That's where the 50% and 35% came from.

Now...what do we count as "power failure" in these cases. I actually can calculate this about a half-dozen ways. The statistics above are for loss of engine power *for any reason*... including the pilot running out of gasoline.

Another way I calculate it is based *only* on whether it was related to mechanical issues with the engines, OR whether the cause of the power loss was undetermined. Using this method, the percentage of power loss cases drops to 39% for the Sonex, and 29% for the Zenair CH-750.

I can also calculate it based on leaving out the "undetermined" cases, or cases where the engine issue was the primary one, and leave off cases where some other issues contributed.

But it doesn't make that much difference. Like I said in the earlier posting, the issue is the reliability of the engine *package*.

I run these analyses as a hobby, and one thing that makes it worthwhile is discovering some fundamental issue that was not previously known. One of these is the revelation that homebuilt aircraft *type* doesn't make THAT much different to accident rate...that the primary driver is the type of engines installed. And so far, traditional engines (Lycomings, Continentals, etc.) are the winners in the reliability sweepstakes.

Take those 34 Zenair CH-750 accidents. Eight of the aircraft mounted traditional engines, another 11 included purpose-built four stroke engines (Rotax 912, Jabiru, etc.) and 11 more had auto-engine conversions (which I include the Aerovee).

The Sonex? No traditional engines, 20 purpose-built four strokes, and 26 cases with auto-engine-derived powerplants. Three of the accidents with the purpose-built four strokes were due to engine issues (based on my second definition above), but 14 of the auto conversions.


Certainly. This is the kind of finding I was originally hoping to find in my analysis, but, again, it's kind of obscured by the engine reliability issues.

The difficulties of performing deadstick landings on high-drag airplanes like the CH-750 have previously been noted in this thread. About ten years ago, the FAA released Advisory Circular AC 90-109, "Airmen Transition to Experimental or Unfamiliar Airplanes." Appendix 4 addresses the issues and suggested training for high drag/low-inertia aircraft. I was on the committee that wrote the AC, and actually was the author of Appendix 4.

Ron Wanttaja

When I started to test fly the SSSC, I have never flown any airplane lighter than a J-3 Cub, Champ, T-Crafts, etc. On the first test flight the EW of the SSSC was 450 lb. I probably would have damaged it on the first landing if it wasn't for a friend that had over a thousand hours in a 1/2 vw in a Mini-Max about the high drag and low inertia of such a light weigh airplane. Huge difference.
 
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bkc

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??? :)


The 750 STOL requires you maintain some power all the way to landing. Otherwise it drops quickly. You can't truly 'flare' one, or it just stops, so that may be what he tried.
I do a power-off/idle flare every time I land my 750 STOL. However, my trim is set on approach so that I have to apply a bit of back pressure and I also have elevator VGs. Both of these help with elevator authority during touch down. Flare is very short, not like a cessna but more like my old tri-pacer. Many do use a bit of power to extend the flare and make landing a little easier but definitely not a requirement.

This guy has a Cruzer which I have heard flares more traditionally without power but I don’t have first hand experience.
 

Rhino

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I'm going by what Roger Dubbert told me. He said power off and/or flares were for those who liked abrupt arrivals. But that was before the advent of elevator VGs, so obviously that could alter the scenario. I know little about the flight characteristics of the Cruzer except that it cruises a bit faster, so I won't pontificate there.
 

raytol

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Can someone confirm the Viking 130 has electronic ignition subject to "electrons stop, the engine stops" syndrome of recent T-51 fame.

Don't be too quick to blame the engine.
I can definitely confirm your question. We had a battery fire and the engine stopped. The setup has 2 ignition systems available so I am recommending a switchable 2 battery system.
 

Wayne

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The Cruzer flies very much like a lighter, more maneuverable, C152. It has much better visibility than a 152 and is wider in the cockpit. It feels light to fly.

I have about 40 hours in one and the one I built is about ready to get it's FAA review. They don't come with intersection fairings and are about 850 or so pounds empty with an O200 so slow down fairly quickly but really no big deal to someone on the ball.

I wonder if there could be an impact of engines/Zenith 750's because Zenith encourages different engine installations and perhaps other manufacturers have standardized more? I like the choice we have with Zenith on powerplants, but maybe that does have a tax.
 
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proppastie

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We had a battery fire and the engine stopped.
I take it you only had one battery but could you let us benefit from the lessons learned in more detail.....what kind of battery, why the battery fire, custom design system or recommended/purchased system design from others........if explained somewhere else maybe a link....this is the kind of information we all can learn from.....thanks ahead of time
 
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