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50 cents

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jakereyna(at)yahoo.com
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Posted: Wed Jun 17, 2009 4:14 am Post subject: 50 cents

I ran a query at ntsb.gov for fatal accidents in amateur built airplanes since January 1, 2006. On average, there are 70 accidents causing 100 fatalities annually. Since we know there have been 10 fatalities in Zodiacs in the same time period, average 4 per year (I do some rounding), leaves the XL with a 4% fatality rate. That seems reasonable, but what about the other 96%. 



If you take the time to look at the data, you will see that the fatality rate is higher in other amateur built airplanes. Are the recent XL accidents an anomaly? 



There are those that continue to believe there is a flaw with the XL, but they fail to accept that once you leave the ground the odds change significantly. Flying is a battle against Nature, things like gravity, wind and heat. Gravity will always win this battle. The biggest flaw associated with the XL or any other airplane is the pilot.



Some will not be convinced all is well regardless of the data and testing. This creates a great opportunity for those interested in an excellent airplane at a reduced price. There are a handful of builders that lack confidence in the XL and should be willing to part with their project at a significantly reduced price, after all, they believe the airplane is unsafe. For those of you that know otherwise, I suggest offering them 50 cents on the dollar for their project. There are some great deals out there with the real possibility of acquiring a complete XL kit, engine, instruments, etc. for $25,000. Depending on the level of completion, it may have to be registered as an ELSA.



When life gives you lemons ....



Jake

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psm(at)att.net
Guest

Posted: Wed Jun 17, 2009 4:37 am Post subject: 50 cents

Hi Jake,



Thank you for looking at some data before pronouncing the XL 

safe.  That puts you several notches above many posters on this open forum.



I do have a few questions about your data.



First, how many of the 100 fatalities were caused by in-flight 

structure failures?  How many of those were in Zodiac XLs?  This 

would give you the percentage of actual fatalities caused by 

in-flight structure failures as opposed to any sort of accident.  I 

think a closer examination would show that structure failures are 

quite rare compared to things like flying into the ground.



Second,  of the in-flight structure failures how many were preceded 

by mid-air collisions.  I have noticed a rash of those lately.  Each 

one generates two accident reports (one for each plane in the 

collision).  So for a fair comparison with the Zodiac XL breakups 

(which generally don't include hitting another airplane)  you must 

subtract two times the number of in-flight structure failures from 

the list of these accidents for each mid-air collision.



Third, how many flight hours have been recorded in Zodiac XLs in your 

sample period, and how many total GA hours were flown in the same 

period.  If the Zodiac XL has the same accident rate as the general 

fleet then the number of accidents should be compared - per 100,000 

hours flown - to the entire GA fleet per 100,000 hours flown by the 

entire fleet.  This would give a reasonable measure of the risk, per 

flight hour, rather than the simple accident rate without considering 

flight activity.



I'm afraid your statement that the Zodiac XL has a 4% fatality rate 

was not computed in a reasonable fashion.  Your calculation should be 

described: "4 percent of fatalities occurred in Zodiac XLs".  When 

you adjust your computations to reflect actual risk in the XL 

compared to the rest of the GA fleet I think you will get an 

unpleasant surprise.  If you further adjust your study to include 

only single plane structure failures in flight I think your 

unpleasant surprise will increase by an order of magnitude.  If you 

further adjust your numbers by eliminating the accidents easily 

explained by events like rookie pilots taking off in thunderstorms 

and suffering the expected result, then your numbers will be really scary.



I look forward to your updated report.



Paul

XL grounded

At 05:13 AM 6/17/2009, you wrote:

 	  Quote: 	
		  I ran a query at ntsb.gov for fatal accidents in amateur built 

airplanes since January 1, 2006. On average, there are 70 accidents 

causing 100 fatalities annually. Since we know there have been 10 

fatalities in Zodiacs in the same time period, average 4 per year (I 

do some rounding), leaves the XL with a 4% fatality rate. That seems 

reasonable, but what about the other 96%.



If you take the time to look at the data, you will see that the 

fatality rate is higher in other amateur built airplanes. Are the 

recent XL accidents an anomaly?



There are those that continue to believe there is a flaw with the 

XL, but they fail to accept that once you leave the ground the odds 

change significantly. Flying is a battle against Nature, things like 

gravity, wind and heat. Gravity will always win this battle. The 

biggest flaw associated with the XL or any other airplane is the pilot.



Some will not be convinced all is well regardless of the data and 

testing. This creates a great opportunity for those interested in an 

excellent airplane at a reduced price. There are a handful of 

builders that lack confidence in the XL and should be willing to 

part with their project at a significantly reduced price, after all, 

they believe the airplane is unsafe. For those of you that know 

otherwise, I suggest offering them 50 cents on the dollar for their 

project. There are some great deals out there with the real 

possibility of acquiring a complete XL kit, engine, instruments, 

etc. for $25,000. Depending on the level of completion, it may have 

to be registered as an ELSA.



When life gives you lemons ....



Jake

- The Matronics Zenith-List Email Forum -

Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

http://www.matronics.com/Navigator?Zenith-List

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