On Apr 17, 11:27 am, "Robert M. Gary" wrote:
On Apr 17, 2:53 am, tman inv@lid wrote:

Flown C172's for quite a while, and never had anybody in the back.
Now I'm planning on quite a trip, with 2 pax and luggage.

The biggest problem with flying a little overgross is the same problem
with flying at high density altitude. The plane will perform different
and a pilot who isn't expecting this can run into serious problems.
The site picture over the nose will look a bit different. This is why
I always teach my students to climb out on airspeed. I know some CFIs
focus on the site pitch picture but that only works with consistant
weight, altitude, etc.
Many pilots have bitten the big one because they keep pulling the nose
up when climbing out of mountain airports until they stall it. They
keep trying to achieve the site picture their CFI taught them down in
the valley.

-robert, CFII

Consider this. When was the last time the airplane was weighed? Does
your engine performance exactly the same as when it was manufactured?
Do you get the same cruise speeds as published on the AFM?

Even if the airplane is perfectly airworthy, and all maintenance done
properly, you don't know if the engine is producing 160HP (or whatever
the rated power for your airplane). There is no signature in the
logbook that certifies that the airplane engine has been tested and
found to produce the specified power. I have flown rentals that flew
like a 120HP Cessna instead of a 160 HP. RPM can't tell you the true
power because every airplane uses a different pitch prop.

Chances are this airplane is a little heavier, and engine is little
weaker. Almost every rental airplane I have flown does not cruise as
the book says. Takeoff and landing performance has a lot to do with
pilot capability, but cruise performance is a good benchmark that does
not involve pilot capability.

If you have ever flown an airplane at max gross or close to it, then
you have flown it overgross. Legally the airplane may not be over
gross, but practically it is.

Not only do I recommend against flying overgross, I do not recommend
flying at gross either, unless you are the owner of that airplane and
are very familiar its performance.