(Koopas Ly) wrote:

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.

I don't know. The engine mount is just one to pick as an example - but
as others have said it isn't the most likely. It could be almost
anything - on aircraft with tip tanks it could be the attachments for
those for example. All up I don't think it matters - these are just
possible reasons why Va doesn't get higher as weight decreases.

You may be right, but the aerodynamics taught to private pilots is
rather simplified in general. I did find out about it in my training,
but it was probably a result of asking the same question you are
asking - why does it decrease not increase.

Physics is something some people find very difficult, so requiring
that everybody understands why Va decreases with decreasing weight may
be too difficult.