ELi5 How can modern jet airliners fly on one engine without going in circles?
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Aircraft have flaps they can move to direct how air flows over their surface. This is useful for things like steering or lift. If one engine goes out the pilots can move the flaps such that the off-center thrust is compensated for. It isn’t as efficient as if both engines worked but it functions well enough to fly safely.
Most of the energy is going forward/upward from the engine, be it 1, 2, or 4 engines. Even on a single engine in the middle there is a slight push to one side as the engine spins (most pilots are familair with this from learning on prop planes). You can correct this by slightly angling the plane to offset the push to the other side.
In modern aircraft, computers correct for this as they do a majority of the flying, and as long as you have some engine power, you can keep flying and correcting for any issues pushing your nose to one side or the other and increasing or decreasing power as needed
Aircraft are designed such that even with a dead engine it is possible to create enough force with the rudder to counter the yaw force caused by flying with only one engine operating. This is possible because there is enough air flowing over the rudder as long as you stay above a certain speed (called Vmca) even while at maximum power on the working engine. If you slow below Vmca while at maximum power on one engine the aircraft’s yaw caused by the operating engine will no longer be stoppable with the rudder (to be technical Vmca is the airspeed at which directional control cannot be maintained with maximum power on the operating engine and with the most critical engine failed with no more than 5 degrees of bank). Every multi engine pilot is tested on their ability to slow to this speed while operating on a single engine, recognizing the loss of directional control, and safely recovering control.
Modern aircraft are ridiculously safe. Any modern airline jet is capable of flying an approach to landing, rejecting that landing, and taking off again on just one engine. Every airline pilot has been tested in the simulator to conduct this maneuver. They are also perfectly capable of losing an engine during the takeoff roll and continuing the takeoff and climb out on only one engine (the speed at which it is safe to continue takeoff on one engine is called V1, if something blows up before accelerating to that speed the pilots will simply stop the plane on the remaining runway. Airlines are prohibited from taking off from a runway that is too short to allow them to accelerate to v1 and then safely come to a stop on the remaining runway). All airline pilots are tested on this as well. Additionally “uncommanded inflight engine shutdowns” as the FAA refers to them occur less than 1 in a million flight hours for modern passenger jet engines.
Source: certified flight instructor for single and multi engine aircraft. And former airline pilot.
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