To answer your specific question. There is NOT necessarily a
reduction in "g" allowable due to age. There is a reduction as the
airframe metal fatigues but only as the flaw (crack) reaches a
certain size. So as long as there are NO cracks, the airframe can
withstand as many "g"s when 40 as when new.

The question then becomes "does my airplane have any cracks?". The
answer to that question would require a teardown, paint strip and NDT
testing of every part and you'd likely damage more parts than had
cracks (if any) in the process.

If the airplane had a straight and level existence, wasn't used for
flight training or aerobatics then the tach time age on the airframe
would be a good indicator of the life left and the probability of a
cracked part. I would say that a major crack should NOT happen under
normal 1-2 "g" loading until at least 10,000 hours. Minor cracks can
occur in secondary structure (fairings and wing tips) but those can
be picked up when seen and shouldn't happen until 4000 hours or so.


--- In musketeermail@yahoogroups.com, Ann Kirby <abk100@y...> wrote:
>
> Is there any data to substantiate a degradation in the
> G loading stress factor with age? It sounds plausable,
> but not good. Not worried, but curious.
>
> Dan, Sierra N9299S
>
>
> --- Bob Steward <n76lima@m...> wrote:
>
> >
> > >OK, I know I am going to catch a lot of grief with
> > this question.
> > >If overload my gross by 40 pounds and by the time I
> > fly a 1/2 hour, I
> > >would be back under gross. Do you think this could
> > become a major issue or
> > >can our planes handle it?
> >
> > The insidious nature of the busting of GW is that it
> > doesn't immediately
> > bite you in the butt if you are not at the edges of
> > the flight envelope.
> >
> > Yes, of course you can overload the plane and take
> > off from a long runway
> > at a low density altitude that doesn't have any 50
> > foot trees at the end.
> >
> > The other factor is that the stall speed and the
> > power off sink rate go up
> > with additional loading.
> >
> > You aren't going to break the plane from the 40#
> > stress. The plane has a
> > 3.8G structural safety factor (when new) and 40#
> > isn't going to cause a
> > failure in smooth air and with a light touch on the
> > controls so you never
> > spike the G loading.
> >
> > That being said, why do you NEED to push the loading
> > over the approved limits?
> >
> > Do your passengers know that you are flying a test
> > mission and they are the
> > guinea pigs?
> >
> > When the engine acts up before you get to pattern
> > altitude and you need
> > every knot of airspeed and every foot of altitude to
> > get it on the ground
> > safely, will you still be thinking it was a good
> > idea to carry that extra 40#?
> >
> > Bob Steward, A&P IA
> > Birmingham, AL
> >
> >
> >
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