On Thu, 20 May 2010 06:49:58 -0700, Ron Wanttaja
wrote:

Oliver Arend wrote:
After reading

http://www.faa.gov/aircraft/gen_av/l...dia/Zodiac.pdf

I'm wondering how much trouble is hidden in other kitplane designs?
Obviously, the RV fleet seems to be rather untroubled....

Obviously?

http://www.kalinskyconsulting.com/rvproj/nosegear.htm

I've been looking at homebuilt accidents for quite a while now. I got
into it hoping to find, among other things, common threads in accidents
that might indicate design flaws. As it turns out, clear-cut cases are
rare.

One factor is probably the relative scarcity of most homebuilt types,
which reduces the sample size. Its hard to spot trends from ~5
accidents per year for a given type, especially when over half of them
are going to be due to pilot error.

Ron Wanttaja

oliver's thread should be titled 'quality of kitplane design' because
this really hits the black hole in most of aviation.

nobody ever publishes the design calcs so you have absolutely no way
of knowing what assumptions the designer made, you have no idea where
they may have made a calculation error and you have no idea what the
designer simply forgot to do.

of course even if you actually saw the calcs would you even recognise
a problem?

as it happens I have seen chris's design calcs for the UL. they are
many pages of tightly written calculations. I didnt fully understand
what he'd calculated. it took a very experienced and schmicked up aero
engineer to say 'hang on a mo' there's a calc error there'. ' gee that
bit of the structure looks a bit flimsy'.'hang on that isnt the way to
calc that'.
in the meantime dozens had been built.

the schmicked up aero engineer tells me that the corrections the poms
made and the corrections described on the EAA website dont actually
fix all of the problems that he is aware of.

the short answer to oliver's question is that you will never know.

calculation competence isnt the full answer either.
The W8 Tailwind had no design calcs done that I'm aware of and yet the
TLAR approach has produced a competent aircraft.
My copy of Wittmans W8 is 25 years old. 750 or so hours and decidedly
airworthy.

The truth is that this design competence problem wont go away until
design calcs are published so that some sort of peer review can occur.
can anyone see that happening anytime soon? I cant.

we also need a history of published design calcs out there so that
people can build up the competent review skills.

the solution in the meantime is to wear a parachute during test
flying. actually fly a full test program including a dive to VD and a
60 degree banked turn both to the left and to the right at Vne.
it wont prove everything but it will give you some increased
confidence.

btw I saw a really beautifully built RV6 landed a kiss on greaser on
its test flight then go plonk on to its nose as the nose leg broke
off. vans denied a problem. tisc tisc.

Stealth Pilot