Gross Weight

Mike Granby wrote:

Do any of you "slippery slope" gentlemen ever exceed the speed limit on
the way to the airport?

One could argue that the speed limit is a lot more of an arbitrary number
than an aircraft's gross weight figures.

Consider the fact that in the US, the typical highway speed limit was 65
mph, then dropped to 55 mph over the late '70s, 80s, and 90s, then raised
back to 65 or in some states, even higher, in the late 90s.

--
Peter


















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Addressing this as an intellectual problem, "it depends". With CG in
the middle of its range, smooth air, low density altitude, aircraft and
engine in excellent condition, a long runway, and a pilot capable of
flying and landing smoothly, I'd guess most light planes would easily
handle 10% over certificated weight. Long range ferry pilots often
take off overloaded, and I understand it's also common practice in
Alaska, where many of the above conditions do not exist.

Interesting to see how many people get fired up about this. When you
fly, you have to use your brain for all aspects of the flight, not just
quote the rules.

One could argue that the speed limit is a lot more of
an arbitrary number than an aircraft's gross weight figures.

Like the max gross on the Warrior 161 that can be changed by putting a
sticker in the POH? Or the max gross in that Cessna that can be changed
by limiting the flap travel? Or the max gross on the PA-32-260 which is
the same as that on the PA-32-300, despite having a lot less power for
take-offs in marginal conditions? Once you start deciding for yourself
what is acceptable and was isn't in terms of speed, and ignoring the
"experts" who set the limits, you're in the same position as busting
max gross. You're thinking for yourself, and ignoring the rules. Thus,
if one is likely to make you an across-the-board rule breaker, so is
the other. There are good arguments against over weight operation, but
this slippery-slope argument isn't one of them.

Also, let's do away with this by-the-book argument. None of us fly
light aircraft by the book. We don't take-off from fields that are
*exactly* what is stated as required by the book and we don't land into
fields that are *exactly* what the book says we need to stop. We add a
safety margin that we are comfortable with, and that is based upon our
own experience of the aircraft that we've built-up over time. The book
figures are, as we always reminded, with a new aircraft with a pilot
who is probably a damn sight better than we are. So, since our aircraft
aren't new, and since we're not that good, we might as well say that on
every take-off, we're a test pilot, since we're operating in conditions
that aren't documented in the POH.

The fact is that over-weight operation is not particularly dangerous
unless you're out of balance or in marginal conditions re the take-off
in the first place. The structural effects aren't going to be a
problem, and the stall speed effects aren't going to be a problem. The
failure mode that matters is failing to get out of ground effect, or
failing to get into the air at all. And that is something that can
happen whether or not you stick to max gross, and that you have to use
your judgement to decide upon based upon your knowledge of the airplane
and what you're comfortable with. So while it isn't legal, it isn't
particularly dangerous, and it is far more common than most people
would admit.

When you fly, you have to use your brain for
all aspects of the flight, not just quote the rules.

Amen.

Mike Granby wrote:

Once you start deciding for yourself
what is acceptable and was isn't in terms of speed, and ignoring the
"experts" who set the limits, you're in the same position as busting
max gross.

I was thinking more along the lines of the fact there are demonstrative
loss of performance characteristics when operating over a specific
aircraft's gross weight limitation and probably a much higher risk of
accident versus than that of operating an automobile at a speed higher than
what was arbitrarily chosen by the government without regard to the
specific vehicle type.

--
Peter


















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I was thinking more along the lines of the fact there are
demonstrative loss of performance characteristics when
operating over a specific aircraft's gross weight limitation
and probably a much higher risk of accident versus than
that of operating an automobile at a speed higher than
what was arbitrarily chosen by the government without
regard to the specific vehicle type.

Well, quite, but that's a conclusion that *you* are coming to, and in
doing so, you are ignoring the rules. And yet if someone comes to a
different decision and decides that, for example, being 5% over-gross
is safer than being 15% over the speed limit, that somehow makes them a
slippery-sloper who will suddently start to break other rules, while
the speeder's judgement as to what rules to follow is considered
without such dangers. Doesn't make sense........

Fred Choate wrote:
Here is a topic that was of discussion at work today:

How much is too much over gross weight? For example.....the 172 has a gross
weight of 2300 lbs, but what if you are 2345 at time of takeoff.....is that
too much over, even if you are going to be burning enough fuel before your
first scheduled stop to be under weight for landing?

Just to add a little gasoline to the legal vs. practical argument,
there are a good number of STCs out there that allow for gross weight
increases. Power Flow has one for the C-172N that with relatively small
modifications (limit flap travel, a cowl cooling lip that some N's
already have) makes it legal to carry an extra 100lbs.

http://www.powerflowsystems.com/prod...htincrease.htm

It would seem to me that the real risks come from (1) CG limits and (2)
takeoff performance. If you overload the plane beyond a certain point,
it just isn't going to fly. Somewhere below that line, you'll fly in
ground effect only, or have miserable climb rates. In either case, the
lethal failure is the failure to abort soon enough. This is an
experiment best conducted on a very long paved runway with no 50' trees
at the end. In the back-country, where overloading is often committed,
you're committed to flying soon after the plane starts rolling. Can an
average GA plane take off with a load great enough to cause damage in
the event of hitting some chop? I don't know, but I suspect that should
be the least of one's worries.

CG seems a more pernicious issue to me, as the plane's behavior can
fool you. Chances are you won't realize you're thoroughly screwed until
after you're up in the air without any good options. In addition to
takeoff CG, I'd also compute CG with half fuel and very little fuel,
just in case.

And then there's the conditions at the moment of takeoff. A C-172 at
gross on a hot humid day is in a lot worse situation than the same
plane 50lbs over gross in the middle of winter at -10c. One's legal,
the other's not, but which would you rather be in with a short runway
and tall trees?

As a low-time pilot, I choose to maintain wide safety margins,
including abiding by the book where I am not sure.

-cwk.

Jose wrote:
How much is too much over gross weight? For example.....the 172 has a gross
weight of 2300 lbs, but what if you are 2345 at time of takeoff.....is that
too much over

My answer is that anything over book is too much. It nibbles away at
flight regimes that you might need, and discover too late that you are in.


As a practical matter, if being 45 pounds over gross makes the difference
between somebody going or being left behind, I can tell you that you'll be as
popular as a turd in the punchbowl if you leave that person behind.

As a former part 135 charter and cargo pilot, I can also tell you that you
wouldn't hold on to your job for long if you hold on to your principles so
tightly. Some leeway is expected, as nobody operates in the perfect world
except the FAA... and apparently, you.




--
Mortimer Schnerd, RN

VE

In article ,
"Hotel 179" wrote:

If you are flying in Alaska, the regs allow a 15% fudge factor if you are
below a certain weight.

Not true. The 15% increase is for specific airplanes with approval.

--
Dale L. Falk

There is nothing - absolutely nothing - half so much worth doing
as simply messing around with airplanes.

http://home.gci.net/~sncdfalk/flying.html

As a practical matter, if being 45 pounds over gross makes the difference
between somebody going or being left behind, I can tell you that you'll be as
popular as a turd in the punchbowl if you leave that person behind.

Leave some gas behind and alter your flight plan if necessary.

If your limit is 45 over gross, how far over your limit is ok?

Jose
--
Nothing takes longer than a shortcut.
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