In a game filled with a plethora of choices like Mass Effect Legendary Edition, it's probably odd to come across a guide for a mission that must be accomplished. The option to let Archangel die is not on the table (until, that is, much later in the game in a separate accident). So why is it that so many players are searching for answers on how to save the turian if he has to be saved as part of the main mission?
Frankly, because he dies easily, even on modes less than Insanity. The storyline hyped him up to be doomed and the gameplay matches up with that. He can die nearly instantly. Worst of all, without a prior save, gamers can actually lose an entire playthrough during a sequence in which he dies faster than the objectives can be completed. Don't let this happen! These are the best ways to maximize success.
Switch The Friend Or Foe Registry
After landing, push forward until running into Jaroth, the leader of the Eclipse. Just next to him is a room with his vaulted heavy mech inside of it, along with some Element Zero and a datapad to turn in to Aria T'Loak. She'll give Shepard a mission that leads to some secret treasure!
Use the station next to the mech and interact with it to bypass the Friend or Foe ID. Save first (there is a minigame that players will need to beat in order to succeed on this hacking attempt).
Later on, a cutscene will play out and a battle will go down where the heavy mech gets dropped in. Do not shoot the mech, it will help Shepard take out a large group of mercenaries.
Stop The Repairs To The Gunship
It's not possible to miss this interaction, but it is possible to miss the chance to keep the gunship disabled. After speaking with Garm, Tarak, and Jentha, head over to the gunship and advance the mission past this preparation phase.
When the conversation is wrapped up, he'll get a message to send in the teams. Use the renegade interrupt when it pops up. This will kill Sergeant Cathka.
More importantly, this will also stop the repairs to the gunship, stripping away a layer of its defenses during the final fight when saving Archangel.
Leave A Squad Member With Archangel
After meeting up with Archangel, Shepard will have the chance to leave a squadmate with him. Always choose a squadmate to leave with Archangel. There is no ideal choice for who to leave behind, any of them will work just fine.
The battle ahead will be harder for Shepard, yes, but making this decision will drastically reduce the amount of damage Archangel takes while Shepard and the other teammate are off fighting.
Congratulations on saving Archangel. He's not a handsome fellow, but he is a fan favorite!