Gross Weight

Excellent post!

I have two comments...

If you fly overgross, you're breaking the rules. Where
will the rulebreaking stop? The answer is really nowhere.

I agree. But as you pointed out earlier, keeping within max gross won't
keep you safe, either. In other words, every flight includes making
decisions about performance that are arbitary, or more precisely, that
are based on experience. If experience didn't matter, why would we keep
log books? If the rules were enough, why would we need anything else?

You can study the design, and the available
modifications and authorizations, to determine
if it is performance, rather than structural integrity
of some component, that limits gross weight.

If it is structural issues -- which I would suggest it very rarely is
-- you'll still have a huge safety margin when 5% or 10% over-weight.
You are not going to be getting that close to the 'g' envelope, and
your landings are hopefully not going to be hard enough to be given 10%
of collapsing the gear!

Further, if you look at accident reports where over-weight operation
was a factor, I doubt you'll find many where structural issues came
into play. In fact, I can't recall reading a single one, and like most
pilots, I eat 'em up to try and learn from others' mistakes. As I said,
the failure mode that matters most is failing to fly, or failing to get
out of ground effect.

If it is structural issues -- which I would suggest it very rarely is
-- you'll still have a huge safety margin when 5% or 10% over-weight.
You are not going to be getting that close to the 'g' envelope, and
your landings are hopefully not going to be hard enough to be given 10%
of collapsing the gear!

The answer to this is - it depends. I agree - the average flight does
not take you anywhere near the limits of the g-envelope. However,
momentary loads of 3 gees or more are not unheard of when flying in
moderate turbulence. So for a VFR flight under a stratus overcast,
sure, I wouldn't worry. For an IFR flight in cumuliform cloud, with
scattered embedded T-storms, I would reconsider. Note that while the
ultimate design load is 150% of the rated load, there is no requirement
for the structure to withstand the ultimate design load without damage.
Deformation is permissible. Repeated deformation due to excess loads
may be a problem. This all assumes the key structural components were
correctly manufactured in the first place, and have not deteriorated.
With an aging fleet, that may not be all that valid. However, I will
grant you that for a utility category aircraft, this is not an issue
worth considering.

The same issue comes up with regard to landings. Long smooth runway in
daylight and light winds, in a plane I've flown before many times? No
problem. Unfamiliar airplane and short strip with gusty crosswinds? I
think I want all the protection I can have. How tough is the gear,
anyway? When effectively the same gear is being used on an airplane
with a significantly higher gross weight, that tells you something (the
gear has plenty of margin). When you have a max landing weight lower
than the max takeoff weight, that tells you something too (the gear has
no margin - it is maxed out). Just something to think about.

Further, if you look at accident reports where over-weight operation
was a factor, I doubt you'll find many where structural issues came
into play. In fact, I can't recall reading a single one,

See the NTSB references in my reply to cwk.

Michael

The same issue comes up with regard to landings. Long
smooth runway in daylight and light winds, in a plane I've
flown before many times? No problem. Unfamiliar airplane
and short strip with gusty crosswinds? I think I want all
the protection I can have.

Agreed 100%. As I said before, it's about JUDGEMENT.

See the NTSB references in my reply to cwk.

I looked at these, both of which were for Cessna 402Cs, which I think
immediately says something about whether we're dealing with a general
or model-specific issue. The first, for N819BW, happened when the spar
broke where it had been subject to mechanical damage AND deep machining
marks. Hardly sounds like being over-weight was the cause here. The
second, N405MN, can't really be put down to anything, since very little
of the airplane was recovered. Again, hardly a clear case of
over-weight operation causing structural failure.

"Mike Granby" wrote

Further, if you look at accident reports where over-weight operation
was a factor, I doubt you'll find many where structural issues came
into play.

Right. I seem to remember that maneuvering speed (the max speed for not
over stressing the airframe in turbulence, or hard maneuvers) is higher, for
a more heavily loaded aircraft.
--
Jim in NC