tman 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.

You shouldn't be scared, you should be confident. (And above all safe.)

In more cavalier flying days I have done this once or twice, right at or
slightly over gross, in a 172 on an ideal day. For the purpose of
discussion let's assume you're going to do it.

Where's your CG and how will it influence takeoff and climbout? What
happens if the engine quits on departure? How much extra runway do
you have, and what does your density altitude look like? An airplane
that is overgross might still perform better in straight climbout than
an undergross airplane on hot, humid day. If you've got 11,000 feet of
runway ahead of you with the elevation at near sea level, and no
obstacles to clear, and it's cold and dry, that will help. If you're
going to be going over mountains or it's turbulent, you need to know
what to expect.

My biggest concern here would be the "never had anybody in back" factor.
When you launch and land with four adults on board, even under gross
it's a different feel. If you've experienced that and you already know
what to expect with an airplane near max gross, you will be able to
recognize how the airplane is handling differently once you're over
gross. Without that previous experience it would be pretty tough to
tell whether you're experiencing a situation caused by being over-gross,
or something that feels normal with four adults on board. The
additional stress and distraction on the PIC could be more of a factor
than that placed on the airframe.

Finally, I personally -hate- feeling like I'm a half-ass pilot or that I
just put my pax at the edge of my envelope without their knowledge. If
they're all aware of it and they understand, that's one thing, but if
something happens you might end up feeling like a total heel, or worse.

If I were going to do this flight I would run around the pattern a few
times with pax in back so you get a feel for what's supposed to happen.

Keep your airspeeds up, keep your pitch and bank rates low, watch your
angle of attack (!!!), stay coordinated and fly like you're carrying a
load of nitroglycerin. Work your CG figures for both takeoff and
landing, and also empty in case you have to divert. If you're "scared"
you're more likely make mistakes.

Having said all that, I don't think I'd make the flight myself. But I
have before, in a 172 at maybe 40lbs over gross, and nothing broke.

-c