On 2008-07-29, Victor Bravo wrote:
If I left you with the opinion that I was associating the tail flexing
with the wing issues I apologize. They have nothing to do with each other
to my limited knowledge.
Well, then, there's little point in harping on it if the subject under
discussion is the cause of what appears to be in-flight structureal failure.
There are only three 601XL people I know personally. The 3/4 completed
Quick Build kit project with a Jabiru 3300 has been put up for sale by
the builder because of the wing issues. The factory built fly-away LSA
airplane has been put in the back of the hangar until this same issue
is sorted out to his satisfaction. The XL that was built and flown
crashed on the first flight, due to something that had nothing to do
with the wing or tail.
Right. Airplanes crash for lots of reasons.
One of the Heintz brothers ... said that there is no one common factor among the
accidents that are under investigation.
Let me get this straight... you're saying there is no one common
factor in the structural inflight failure crashes of... five 601XL
type aircraft ??? Jay, 601XL IS the common factor !
Just like the RV is the common factor in all of the inflight failures Jim
Logajan mentioned. The point is that, if there's no common factor in the
601XL crashes, then there's likely no design flaw - for if there was one, it
would show up as a common factor in the crashes.
Even if your scaremongering about the 601XL were on target,
Scaremongering !?!? Kindly explain where you would draw the line
between intelligently discussing a potential problem (that has
resulted in several tragedies) and "scaremongering". Would you prefer
to just not allow any discussions about a potential problem with a
specific airplane?
Your line right abouve, about the 601 being the common factor - even though
there's no evidence, at this point, that the various crashes are in fact
related by any particular cause - is scaremongering. Intelligent discussion
would be about trying to figure out what the problem is, not railing that
the design is unsafe without anything concrete to back it up.
You sound like the people who stand out in front of a courthouse
screaming "racism !" because the guy who shot four innocent people and
is on trial for murder happens to be a different skin color than the
people on the jury. That has nothing to do with whether he shot the
people or not. Because I have the nerve to hold up an argument and
make people talk about a possible design issue, does not make me a
scaremonger.
Sorry, but I disagree. You fail to advance any other cause that's backed up
by real-world data. There have been lots of crashes in RVs, but you're not
running around calling it unsafe.
Ahhh... the dull yellow light of higher brain function flickers briefly...
For someone who claims not to stoop to personal insult, this is awfully
insulting.
I do not believe there is an inherent design flaw sufficient to cause
structural failure of an aircraft that is properly built, well
maintained, and conservatively flown.
...and just as quickly is extinguished.
....as is this.
I've looked at the available data, and come to my conclusion based on what's
known and what's been disclosed. Because my conclusion is different from
yours, you claim my brain isn't working.
All you're doing is destroying your credibility. You come across like a
salesman for a competitor, trying to destroy the market for the Zodiac, not
like someone interested in improving air safety.
In aviation, particularly experimental aviation, we have to be far
more suspicious than complacent. We have to be utterly suspicious of
everything that can affect safety, and ever vigilant.
This (as well as the rest of your paragraph) is nothing more than saying
that pilots have to manage risks. That's indeed inherent in aviation.
Aviation is not dangerous, but it's terribly unforgiving. The pilot's
defense is to assess each risk and determine whether that risk is
acceptable.
You say there are no common factors in the failures... which SHOULD
prove that at least one of them was well built and being flown within
its limits. The most recent one was a formation flight, so it can be
assumed that pilot was flying in level flight and not maneuvering
excessively.
If you're referring to the crash on the way to Sun n Fun, that aircraft was
built by the Czech Aircraft Works to European LSA standards - which include
a 450 kg (990 pounds) max gross, not the 600 kg the XL was designed to. CZAW
had to modify the design to make that limit reachable. We don't know just
what modifications they made.
Until the problem is found, I intend to maintain my aircraft to the highest
standards of airworthiness possible, and fly it well within its performance
envelope and my capabilities as a 225-hour, non-instrument-rated private
pilot. That's all I can do.
Sorry Jay, I can't let you off the hook. The "highest standards of
airworthiness possible" means you would load test the wings (sandbag
test) to verify structural integrity... at various torsional moments
(wing twisting due to air loads).
This isn't something that's done for any other production aircraft during
maintenance. (Remember, mine's a factory-built SLSA, not an experimental.)
Zenair has done that test, and that's good enough for me.
"Within its performance envelope" means that you KNOW what the real
performance envelope is.
AMD tested the aircraft through a full Part 23 certification flight test
program. That's defined the envelope as well as any 152.
If other 601XL aircraft have failed inflight operating within or even near
this envelope, it means the published envelope is really not fully proven
out.
....assuming that the primary cause of the crash was a structural failure of
an aircraft that had been flown within the envelope for its entire lifetime.
Jim Logajan said:
I can only find 2 such cases in the NTSB database - and one of those
appears to have been due to over-control brought on by flight into IMC:
http://www.ntsb.gov/ntsb/brief.asp?e...09X00539&key=1
http://www.ntsb.gov/ntsb/brief.asp?e...17X00209&key=1
There are at least two other fatal Zodiac crashes that come to mind and
could be attributed to wing failure, though the NTSB has not yet released
final reports:
http://www.ntsb.gov/ntsb/brief.asp?e...15X01677&key=1
http://www.ntsb.gov/ntsb/brief.asp?e...21X00519&key=1
Changing my personalities for a moment, and assuming the role of
someone less antagonistic who only wants you to be able to fly safely,
About damned time.
I will turn off the smart-ass switch and turn on the "help this guy
live to enjoy his airplane" switch. Until a real engineer has
determined the full problem and figured out a real solution, I
sincerely advise you to implement a temporary set of restrictions in
your flight envelope to increase your structural margins.
As it happens, I already do a good number of these...
Reduce your turbulent air penetration speed and VNE speed by 25%
each.
Va is 90 knots in the Zodiac. 75% of that is 67.5 knots...and I come over
the fence on landing at 65.
Vne is 140. 75% of that is 105 knots - where I normally top out at, anyway.
Reduce the allowable gross weight of your airplane by 10%.
The Zodiac XL's 1320 pounds max gross is a regulatory number to meet the LSA
spec. The airframe was designed for a max gross of 1450 pounds. 90% of that
is 1305 pounds; I meet that anyway.
Reduce the maximum G loading by one or two G.
Limit aerobatics to low G barrel rolls.
I do not fly aerobatics, period. I'm too susceptible to motion sickness.
Reduce or eliminate maneuvers that put rolling (wing twisting) loads
on at the same time as G loads.
Such as?
Taking these precautions WILL greatly reduce the loads on your
structure, until a qualified engineer figures this all out.
I know how my aircraft has been flown throughout its lifetime, because I'm
the only one who's flown it since it passed its flight test.
You're also assuming that the Heintzes aren't qualified engineers...
--
Jay Maynard, K5ZC
http://www.conmicro.com
http://jmaynard.livejournal.com http://www.tronguy.net
Fairmont, MN (FRM) (Yes, that's me!)
AMD Zodiac CH601XLi N55ZC (got it!)