Bomber Crew

A working engine is an engine running at full speed. The following are not considered working engines:
• engines missing from your plane due to extensive damage
• engines requiring you to repair them, for example, after having burned out.

The achievement itself requires that you land with one working engine and survive the landing, that is, without your plane being destroyed. What makes this tricky is that, as your engines take damage, so does your landing gear (indicated by the two wheel icons below your wings). Without both wheels you will have a hard time not crashing and breaking stuff during the landing.

While you can do this any time during the campaign, I waited till the end. The following, in my opinion, is a must:
• High armour on your wings to protect your landing gear.
• High armour on the rest of your plane and high defence gear on your crew.
• Gunners with high levels and preferably a radio crew member with the Call Spitfires ability.
• On-board fire extinguishers and medkits.
• One high armour engine, whatever you can afford and three low armour engines. I would recommend placing the high armour engine on the inside.

What you want to do is go out on a mission where you know you will be facing quite the resistance. Flak is fine as well. Then, simply pursue the mission so you can return to base or abort it once you have taken enough damage. While doing so, don't engage the fighters. They will damage your plane and wither down your engine's health. When an engine, other than your high armour engine catches fire, let it burn. This will leave the engine stalled and in need of repair. That is fine.
Keep the enemy planes in check, that is, don't allow for planes that will position themselves right below you or behind you and only target your gunner. Also, some carry rockets and will damage your tail rather than your engines. Those can be taken out. I would recommend to have six planes engaging you at most.
If you run out of planes, because you have to take them out because they tend killing your crew, you can use flak to damage your plane further. Simply set custom waypoints and see your plane take damage.

The biggest drawback is that you might end up with a damaged landing gear. You can still attempt a landing but your plane will most likely take more damage and break up, as in be destroyed. If only one wing breaks off you might still be fine. As long as you have a landing gear remaining on the side with the working engine and a bit of luck on the landing, you should pull through.

There are a few more tips I want to give you:
• Don't wait with Calling Spitfires for too long as they take some time to arrive.
• When you feel you are being overwhelmed, use Auto Tag and cycle abilities on your gunners. Focus is great, Incendiary is better and H.E. Ammo does area damage.
• With one engine running, watch out for the last one to be destroyed or stalling. You might want to start fixing another engine and call your Engineer off at the last moment just to be sure you won't crash.
• When flying through flak, use Lean to throttle down and take more damage without having to constantly adjust your heading.
• Medics can heal crewmates slowly by standing next to them (click the green icon) or quickly by using a medkit (and the green icon).

Edit 10 November 2019: Added tip about aborting missions, thanks to the comments.