Re: Critical engine on 747
Well, which first single engine failure is the worst?
Logically, as the 747 engines are chosen to have roughly equal thrust, the failure of an outboard engine generates more asymmetric yaw than inboard engine out.
Then, if there is a crosswind, logically failure of an upwind engine is worse than failure of its downwind mate.
What about the torque?
In a piston prop or a turboprop, the major rotating part that interacts with air is the propeller, so naturally a propeller creates spiral wash which moves towards the direction of rotation - and interacts with the aerodynamic surfaces, too.
But turbofans? For one thing, B747 is well out of its jet blast, right?
For another, what is the direction of the torque created by a turbofan? The air passing the fan must spiral along the direction of rotation, as the fan is imparting speed on the air. But the bypass air moves some distance inside the bypass ducts, unlike the propwash of a turboprop, which is free to spiral around the engine core... then the air entering the core is compressed by the compressor, which should make it continue spiralling. But then the core jet is slowed down by the turbine. Would it also be losing its torque in the turbine?