Originally Posted by
abelenky
A former instructor and I recently had almost this same exact conversation, and here's how it came out.
First and foremost, as PIC, you absolutely can, should and MUST speak up if you aren't comfortable going. So I absolutely defend your choice in that regard.
However, here's what my former instructor and I went through when discussing it.
My C172 has a MTOW of 2400 lbs. That means it can climb, and do 3+ G turns at that weight, and do that with a safety factor of around 150%.
That means it could fly straight-n-level, un-accelerated flight at 2400lbs. x 3G = 7200lbs. and STILL have a safety factor of 150%.
WHOA: 7200lbs!
(granted, the plane won't take off at that weight. If it did, the climb performance will be non-existent, and its possible the landing gear may collapse on landing. But in the air, it would be theoretically fine)
As a result, I'd ask yourself: Are you planning on doing 3G turns? Are you taking off or landing at a short runway? Do you have obstacles at the end of the runway? Is it a hot day, or are there other factors affecting density altitude or airplane performance. Is the wind against you?
If the answer to ALL those questions works in your favor, you have to make a tough call. Flying illegal is illegal. If you got ramp-checked, or if there was an accident then it'd be your ass. But will the airplane perform at that weight? It seems likely it will.
The analogy of speeding 75 MPH in a 60MPH is pretty good. You might get a ticket, but the car won't fall apart around you.
The 3.8g testing requirement is not designed for people planning to go out and pull 3.8g's; this is the maximum that the faa feels is likely during a normal flight (such as, during turbulence). Very few people who take a 172 to the load limit had any plans to do that. And, by the way, at 3.8g's, you're 304 lbs overweight. So now, you hit some turbulence and you're temporarily 300 lbs over the design limit. By the way, that fudge factor (not 150% by the way) is designed to account for the fact that the testing was done on a brand new airplane, not one which has been flexing and slowly fatiguing for years.
Yes, the airplane would have flown, but you're a lot closer to your margins than this guy would have you think, especially if it's a bumpy day. There is a reason for a lot of the things the faa does, no matter how smart some pilots think they are.