What's the relationship between AOA and airspeed?
&quot;Can we get into a stall without reaching the critical AOA?&quot; -- no.
&quot;We know that any aircraft will stall at its stall speed (for a specific weight, CG position, etc.)&quot;-- we need to add &quot;G-loading&quot; to this list of parameters.  The &quot;stall speed&quot; we usually talk about is the 1-G stall speed.  Change the weight or the G-loading, and the airspeed correlating to the stall angle-of-attack changes.
&quot;On the other hand, I know that the critical AOA doesn't change with weight&quot;-- correct, but for a given G-loading, such as 1 G, the airspeed correlating to that critical AOA scales according to the square root of the weight.
&quot;What's exactly the relationship between AOA and IAS?&quot; -- if we know the IAS where the wing reaches the stall AOA at some given weight and G-loading, then we can adjust that IAS for some other condition by multiplying by the square root of the change in weight times the square root of the change in G-loading.  &quot;Change in&quot; meaning the ratio, i.e. new divided by initial.
The fundamental relationship between AOA and IAS is that net lift force at any given AOA is proportional to airspeed (IAS) squared.
Here's an extra complication that you may not want to worry about right now -- the &quot;dynamic stall&quot; -- What is the immediate cause of stall? -- scroll down to last paragraph.