Kitplanes magazine article on the safety of Zeniths: "Safety is no accident"

The November 2010 issue of Kitplanes magazine (and it's still September as I write this!) has a story on the safety of Zeniths, presented as part of a series of articles on homebuilt (kit) aircraft safety. As the article's clichéd title states, safety is no accident, so I'm reprinting it here (with the gracious permission of Kitplanes magazine).
  • View article (Wanttaja, Ron. "Safety Is No Accident." Kitplanes November 2010: 17 - 22).

Overall, the article is rather boring in that it does not reveal anything new - as I suppose it should since it's based on accident statistics (old news). The Zeniths as a whole fall pretty much as expected - right in the middle of pack of homebuilts. Following are some observations:

As far as I can tell, the stats don't factor in the severity of accidents (ie. a prop strike or bent gear leg compared to a not quite fatal yet serious accident). As many homebuilders know, this can make a huge difference! A lot of airplanes, such as the STOL CH 701, are operated in unimproved (or unapproved) areas (short, bumpy, enclosed, slanted, often-remote strips) and may suffer from everyday "use and abuse" in such an environment. Many of our STOL airplanes (as well as some Zodiacs) are operated by adventurous "bush pilots" and this may also result is some higher statistics. That gives the CH 701 a slightly above average "overall accident rate" (Figure 7). However, the STOL CH 701 rates as the lowest percentage of fatal accidents of all types (Figure 6).

Figure 4 is interesting: According to the graph, Zenith builders experience a much higher than "normal" percentage of accidents due to "undetermined loss of power." The context is important here: Zenith builds airframe kits: there is no specified standard engine installations for CH designs (except in non-kit factory-built versions), and the builder chooses the engine and typically performs the installation himself. This freedom allows for innovation and experimentation with many alternative engine types and is appreciated by many builders, but results with the higher than "normal" percentage of accidents due to "undetermined loss of power" (be it from a radiator, reduction drive, etc.). The following graph (figure 5) further illustrates this.

Figure 4 also shows significantly fewer accidents due to "builder error" and "maintenance errors" which speaks well for the construction of Zeniths and their builders. The last item of Figure 4 is "maneuvering at low altitude" and here the Zenith accident rate is much lower than the norm. This is significant because I know that many Zeniths, especially STOLs, are operated (sometimes nearly exclusively) at low altitude. I think that Zenith's excellent slow flight characteristics, as well as great visibility, help to make this rate much lower than the norm.

As the article states, "Figure 1 shows some pleasant news for Zenith fans. The rate of Pilot Error accidents is quite a bit lower than average." Figure 2 shows that pilots have low "time in type" when accidents do happen (36% of all Zenith accidents happen in the first 10 hours; 50% of CH 701 accidents involved pilots with less than 10 hours in type). While the author finds this "troubling" I find this to be a revealing statistic: Clearly, pilots (often the builder and owner of the aircraft) will benefit from type-specific training (before their first flight), especially with an airplane such as the STOL CH 701 with its unique short take-off and landing capability (and as indicated above, when accidents do happen in a CH 701, the fatality rate is the lowest of all aircraft types). STOL pilots can also take comfort in knowing that once they build time in type, the accident rate will be significantly lower (once they are familiar with their airplane). I guess this is all common sense that the statistics support (and one of the reasons there's a 40-hour phase 1 flight test program for most amateur-built planes). Also, the stats do not factor in pilot experience. Zenith customers tend to be low-time pilots or experienced pilots who often are not current (returning to aviation as Sport Pilots), which is one of the reasons that accidents tend to happen early on.

Incidentally, we should not forget that meaningful statistics on homebuilts by type are difficult to obtain since for all intents and purposes, each specific homebuilt is a "one-of-a-kind" airplane constructed by the amateur builder (who is the official manufacturer of the airplane), who then goes to maintain his (or her) airplane as he sees fit. As such, huge variations exist among types, meaning that not all Zeniths (be they a 701 or 601, etc.) are created equally. To further complicate matters, the individual aircraft is registered by the builder with the name that the builder chooses, making it difficult to obtain accurate numbers. (It's only after an accident happens that corrections and investigation are made).

As Wanttaja, the writer of the Kitplanes article, himself states, some of the results may be a statistical glitch. In some cases, it may appear that some of the overall Zenith-related statistics are higher than expected or higher than the norm. As mentioned above, this may be explained by the prevalent use of alternative engines and operating the aircraft in off-airport environments.

As noted in the article, the stats do not include the post-2007 Zodiac CH601XL "wing-failure accidents" since the time-frame of Wanttaja's database is 1998 to 2007. It's interesting to note that the Zodiac CH601XL design was introduced in 2001, many years before the "wing-failure accidents." The article incorrectly states that many of the CH601XL accidents involved LSAs, but it's my understanding most involved amateur-built (experimental) aircraft operated by Sport Pilots.

The folks that pay the most attention to aviation safety statistics are probably in the insurance industry. Bob Mackey of Falcon Insurance (which administers the EAA insurance program) recently posted the following on Oshkosh 365 (on 9/21/2010):
"The Zenith aircraft are looked at favorably by the insurance companies but there was a slight bump in the road with some of the issues that arose with the CH-601XL. A few of the insurance companies stopped offering insurance on the CH-601XL for a while and new ones are being required to show proof the wing mod has been done.We are finding insurance readily available as long as the mod has been completed... I do recommend that you plan ahead so that you built up some experience in make and model before you reach the completion of your airplane. If you finish and you have no make and model experience the insurance companies are going to require 3 to 5 hours make and model time before you proceed with first flight. If you've got experience in other similar homebuilt airplane make sure you mention this to your insurance agent because it can help with the rates. Further the EAA Flight Advisor Program is a requirement with some of the insurance companies. Bob"
We also recently heard from an AMD Zodiac 650LS (SLSA) owner that he received competitive full insurance coverage (with a hull value of $120,000) from Aviation Insurance Resources (AIR) in Frederick, MD: "This is good news since insurance companies don't take any chances when they insure a plane or anything else."

While the Kitplanes article generally does not provide new information, we can all try to learn from it: Notable areas to improve are clearly with the installation and maintenance of engines, and pilots need to pay more attention to those first few hours in type. To succeed, builders and pilots need to realize that outside help is a good thing - and they must seek it out. Experienced Zenith kit builders and pilots have a role to play in this by offering to help fellow builders - in looking over the shoulder of a local builder or taking him (or her) flying a few hours before the first flight of his new creation.

I seldom comment on the "safety" of building, maintaining and operating your own kit airplane because these issues are generally not in Zenith Aircraft Company's control. There are many excellent books and publications available on aviation safety, and extensive resources are available from EAA, such as the technical and flight adviser programs. As builders, mechanics, and pilots, we all need to be continuously safety conscious so that we can continue to enjoy our hobby of building and flying our own airplanes, and as mentioned above, it is my hope that builders and pilots can help each other to successfully complete and fly their own aircraft.


The postings on this site are my own and don't necessarily represent Zenith Aircraft Company's positions or opinions.

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Comment by Bob Pustell on October 2, 2010 at 1:37pm
This is an old statistic, but as of a decade or so ago when I read it, the statistically safest fleet was strut braced high wing Cessnas. Maybe it is because the planes are strong, maybe the pilots are meek and careful, maybe the high wing helps survivability, who knows. The raw data was, however, that that fleet was the safest general aviation fleet out there.

It is very interesting to see that the strut braced high wing 701 came out so well in terms of overall safety. Is there a common link? Dunno.

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