Hi, I have a question about this mission. I am using FSOpen (no graphical mods added), and I am playing on Medium, but for some reason, the game will not let me destroy the Tiamat. I disable its beams and engines fine enough, I even have all my wingmen attack it, but it just gives itself an invincibility cheat while the wussy Aquitane runs away (seriously, I called in for a rearm five times and emptied thousands of Tempests into it, and with aplha and epsilon continuously firing their primaries the health still freezes at some random percenatage). Is there any way to destroy this thing?
I've checked a bunch of walkthroughs, none of them say anything helpful. I've repeatedly seen advice to play on at least medium for the Aquitane's beams to be able to do enough damage, but the ship is never able to do the job. I destroy those Nahemas as soon as I can, I have Alpha wing protect the Aquitane, and I go after the Nephilims (and their bombs) as soon as the game will let me see them, but nothing works.
Any tips you have will be appreciated.

The invincibility thing is a feature of all capital ships. They can only be destroyed by bombs and beam cannons. So, while you can chip away at the Tiamat, you must rely on the Aquitaine for the kill shot.
You need to get as close to the Tiamat as you can, as soon as you can, because if I remember correctly, you are providing targeting data for the Aquitaine.
Perhaps making a note of when and where it arrives, you could then restart the mission, and greet it as it appears?

Hmm, I honestly didn't know that about capital ships. I guess I'm just too used to X-Wing Alliance and such, where you can kill capital ships with primaries (and I think FS1 too, I remember getting kill shots on a Typhon and a Demon on medium).
I don't know about racing for the Tiamat as soon as it appears, I've tried that many times before, with no success (my assumption is that doing that left the Aquitane open to the bombers, and they bombed off its beam cannons or something, despite the... "helpful" wingmen being set to protect the Aquitane).
Just for the record, the closest I got was when the Tiamat was down to 2%, but the Aquitaine jumped instead of finishing the job, but this was after focusing on the bombers first.
Thanks for the reply though, I'll keep trying.

In FS1 you could indeed destroy any ship with any weapons, but in FS2, ships bigger than a cruiser have a flag set in ships.tbl that prevents primary weapons and missiles from destroying them. Beams (and bombs) can take them out, but the bomb part isn't possible in this mission. With FSO, though, if you keep pounding the Tiamat long enough (I think in the order of several hours, use time compression), it will go down.
Then again, you won't get any big medals or promotions or parties if you destroy the Tiamat. The secret for getting the whatever medal in this mission is to keep the Aquitaine's hull integrity above some percentage.

Ah, thanks for the tip. I never got that stupid "order of galatea" medal before (I've beaten the game on easy already), and I just assumed it was for destroying the Tiamat.