CL X-Xay,
Engine out ferry is a very specific operation, with it's own limitation and performance requirements.
The conditions for an engine out ferry are very type specific.
For example, on a DC-4, the prop. on the failed engine must be removed, a DC-6/7 can just have the prop. feathered.
Engine out ferry of a B707 was available, but few airlines ever used it, because it was virtually impossible to produce a V1/Vr/V2 that could cope with a further engine failure on T/O ----- the Vmca2 was so high, compared to any reasonable speed at which you could keep the aeroplane on the ground.
In the case of some B747, Vmca2 was low enough that a "survivable" set of figures could be produced. As I remember, it was normal to remove the fan and blank the core engine, much reducing the drag of the failed engine ---- ie: the failed engine configuration was the same as if the engine was a fifth pod.
Because of the very "iffy" nature of 3-Engine (or in the case of the DC-10/MD-11 2-engine) ferry, very few airlines ever exercised to option. Given that an engine change is a straight forward operation, and carrying a fifth pod is straightforward, or there are plenty of L-382 or AN-125's around, changing the failed engine is the much preferred solution, short of WW111.
Tootle pip!!