Sorry I don't have the forum know-how on how to link exact PDF quotes and page numbers, but here's my question:
Does rolling a natural 20 on a gunnery check during starship combat cause your fired weapon to do double damage during the attack in addition to causing a critical damage effect?
It may seem obvious, but the critical hit rules say when making an attack roll you always hit on a natural 20 and if you beat their AC with modifiers you also do double damage and possibly a critical hit effect depending on the weapon used. However, the gunnery CHECK seems to be a skill check instead of an attack roll per se, and never once uses the term attack roll. It can use your base attack bonus, but that's not always true (You can just use your piloting skill instead), so everything involved in a gunnery check could just be skills and abilities which leads me to my confusion on the issue.
Is the main and only benefit of a nat 20 on a gunnery check causing a guaranteed critical damage effect to a random starship system (If it damages the hull)? Or does it do double damage and a critical damage effect which then could cascade and cause many, many other critical damage effects to random systems as it goes over the enemy ship's CT (Critical Threshold)?
none of the starship weapons appear to list critical modifiers, and the 'combat' section (which i think is different than starship combat) states " If the total result of your attack roll meets or exceeds the target’s EAC or KAC (as appropriate for your attack), you’ve also scored a critical hit."
starships don't have EAC or KAC. so normal double damage on critical shouldn't apply. cirticals also don't matter if you strike a shield with a nat 20.
as far as getting a nat 20 on top of a crit threshold, i'm pretty sure you just blew out two random systems of theirs.
Nat 20 in ship combat is only just another way to dish out critical damage to systems, in addition to CT. If an attack is a nat 20 and the following damage results in the total reaching ship's CT, then two critical damages are rolled to random systems.
Since the effects of a nat 20 are specifically called out in the Ship Combat section, without reference these effects being in addition to double damage, I think we have to conclude that this omission means double damage does not apply.