You can see the vertical axis is the load factor ("G limit"), and the horizontal axis speed. The normal axis stall speed at various loads is the curve marked "
accelerated stall", and it runs up until meets the quoted G limit for that particular airframe.
The basic theory is: Pull back on the stick below this meeting point (ie. below
the manoeuvring speed), and the wing will stall, thus unloading it, before it over-stresses. Pull back on the stick above this speed, and you will overload the wing before it can stall ...
If an aircraft is certified for a max +/- G loading then presumably;
1. This G load is permissable up to the VNE. Put another way does the stress on the airframe increase with speed or does the total G load "capture all", as it were.
You can see that as the speed increases towards VNE, you enter the caution range. Gust loads here will have a consequently higher effect on the airframe, which may result in an overload. The Ultimate G limits reduce (you can see the reduction on the negative side, the positive side reduction is off the scale), I would guess due to flutter problems outside of the ability for the damping control to be effective.
2. Even I know that "compound" manouvers put additional strain on the airframe (I suppose a lomke..whatsit being the most extreme example i can think of) and back when i flew only spamcans one was always warned to be very careful of multiple inputs (like ailerons and elevator in concert when recovering from a spiral dive). So is it the case that again the G meter catches all and the spamcan warning only applies because it doesn't have one.
No - compound manoeuvres reduce the G-limit for the airframe, the G meter only measure G along the normal axis.