Andrew Rowley wrote in message . ..
(Koopas Ly) wrote:

I think I understand now. Let me see if I get it...

To rework the analysis, I'll assume that the weight of the airplane is
mainly supported by the wings, and that other components such as the
engine mount are essentially invariant in static 1g weight. In other
words, by overloading the airplane with other bodies, ballast, and
such, the weight of the engine mount does not change. If that is so,
I can see how such *individual* components may be "g limited" with
respect to their own inertia. Does this follow your reasoning?

almost... the engine mount needs to support the weight of the engine
multiplied by the number of Gs. so if the engine weighs 100kg at 3.8G
the mount is supporting 380kg. At 5G it has to support 500kg. So force
on the wings at high Gs may go down as your total weight goes down,
but the force on other items (engine mount, baggage floor, basically
any part of the airframe that has to support something) does not.

Thanks for the clarification.

What is the critical "item" that will break at 3.8 g's on a light GA
airplane like a C172? Is it the engine mount? I see that's it's
often mentioned as the "weakest link".

It's my opinion that the definition of Va taught to private pilots
leads to a false understanding that the wings will break at 3.8 g's.
The nuance we've discussed is not stressed. Why? I don't know.

Best regards,
Alex