All Schematic Locations in Chapter 3

You'll be making your way through the Engineering Deck, and at one point, you'll have an objective to activate a control console. After you do that, a door labeled "To the Centrifuge" will open up near the Save Point. Take this elevator down. When you arrive, follow the corridor until you reach the Decontamination Room. Head inside, and get ready, because activating the console in here will lock you in and spawn some enemies. You'll face two Lurkers first, then an "Appendage," and finally a Leaper. For the Lurkers, use your Plasma Cutter's horizontal slash to take out their tentacles. Then, switch to the Pulse Rifle and use its proximity mines on the Appendage and Leaper. If you want to make it easier, hit the Leaper with Stasis to slow it down while you blast it. Once they're all down, the decontamination will finish, and the doors will unlock. Go through the "To Centrifuge" door, and right in front of you, you'll see an open locker. That's where the Medium Med Pack schematic is! This lets you buy Medium Med Packs from the store.

Keep progressing through Chapter 3 until you get the objective to "Manually Ignite the Engines." You'll eventually find yourself in a room with a bunch of tentacles. You need to shoot the pustules on them to make them disappear. After you shoot the first pustule, look for a small elevator and take it down. Once you're on the lower floor, some small insect-like enemies will attack you. Burn them with your Flamethrower. Then, walk around the walkway until you find a small room you can enter. The Ripper Blades schematic will be on your left as you step inside. This schematic lets you buy ammo for the Ripper Gun.

This one is pretty straightforward. Continue with the "Manually Ignite the Engines" objective until you reach the engine room itself. The Flamethrower Fuel schematic is sitting on a chair, just to the right of the console you need to activate to get the engines going. Grabbing this means you can buy more fuel for your Flamethrower.