Frans,
Don't forget that this mounting point was originally designed and
stressed to mount the outrigger on the original mono-wheel. Consider
if you will, the compressive shock loads imposed by an unforgiving
landing on rough grass, or the lateral loads imposed during turning.
I cannot recall a single incidence of this part of the
wing/flap/outrigger mounting ever failing (and there have been
numerous mono groung handling "incidents"). Your arguments are
however, all valid.
Nigel
Hi Bob,
I would draw your attention to a simple fact that when the flaps
are
extended at 82 knots a large proportion of the aircraft weight is
carried on the flap hinges.
Yes, but this load is in the opposite direction and from quite a
different nature, and most likely in an angled direction whereas the
flap exerts a "straight" line of load.
Many of us have a "no push" or "no step" mark on the flap, while it
is very unlikely that someone weighs more than the lift potential of
the flap. Apparently some people feel that not all loads are of a
similar nature. I'm a bit cautious, I have to admit, I couldn't help
wondering about this. I just prefer to limit the use of critical
parts to their intended usage.
With regards to receiving snatch blows through the aircraft "bucking
about" this is entirely without foundation since on tying down
through
these points it is possible to load up and deflect the main gear
legs
to ensure the system is constantly in tension.
We all know what happens with the doors when they are in constant
tension by the support springs: they deform. I can imagine when you
load up the structure of the aircraft while being parked in the sun
that it may deform a bit over time. Maybe just a millimeter, but that
said, while building the airplane I did the measurements down to a
precision of better than 1 millimeter. So if I tie down the aircraft
I make sure not to tie any load on the wing. Downside of course is
that if the airplane rocks in the wind that it will jerk on the tie
downs. But I don't use the flap hinges as tie down points. But who
knows? Maybe your method is better. We are just guessing here, aren't
we?
In conclusion I can advise that G-PTAG has always been tied down in
this manner and has withstood some severe gusting wind conditions
without any damage ensuing what or where ever over it's 900 hours
life
time.
It is impressive, but no guarantee by itself that it could never
have any negative consequences. You are probably right but I had an
uneasy feeling when I red about it. If it was about a bicycle I would
have ignored it, but we are talking airplanes here and I feel that if
any of us has an uneasy feeling about something that he should bring
it up.
May I thank Neville Eyre for his kind intervention on this matter
and I
I hope I didn't irritate you, I was just wondering whether using a
critical aircraft part outside the scope of its intended usage would
be safe by definition. I have to admit that I would never have
thought that just a pencil mark would compromise the strength of that
part either.
I think it is a good thing if we discuss the safety of some ideas
before they become common practice. I would really hate to read
someday that one of us lost his flap during flight and that a hinge
with an eyebolt was discovered some distance away from the
wreckage... Especially if I remember having questioned it silently
and never brought up the subject.
I guess we won't be able to obtain a definite verdict on this
matter, everyone should make his own decision. It is probably ok to
use the flap hinge for this but you can't know for sure I think.
Frans
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