Originally Posted by
Natstrackalpha
...just because something is or is not written does not mean that you can or cannot fly an aeroplane, even if it is an airbus.
Spot on. To give a general example, nowhere in the respective manuals of the B747, DC-10 or A300 explains or promotes the use of asymmetric thrust to provide directional control in the event of total hydraulic failure, but it has been done by line crews who were out of "official" solutions with varying degrees of success (including a somewhat hairy but safe landing in the case of the DHL A300 over Iraq, and a famous recovery of a "worst case scenario" in which most onboard survived in the case of the UAL DC-10 at Sioux City).
Ultimately an aircraft is a tool for the end users (in this case pilots) to use in whatever way is necessary to perform their jobs. By and large they are engineered well enough to provide solutions outside of normal operating parameters should it be necessary.