A small time example if I may...
Whilst criusing at around FL380 halfway across the Indian Ocean (heading West) in an almost empty (heading to Jeddah for the pick-up!), B742, we had indications of a quickly rising vibration level as well as some evidence of mechanical vibration...we decided an immediate shutdown was the prudent thing!
So, other 3 engines to max continuous after the shutdown as the airplane began it's driftdown, we were too high for 3 engine cruise, even on MC power.
Now we had two problems...
#1 We were decending on track on an international airway! (The problem was that other aircraft were tracking in the opposite direction only a couple of thousand feet below us!)
#2 HF comms with ATC India was v/slow at best, non-responsive at worst.
Captains decision time...
We immediately turned 30 degrees left and proceeded out there until we were about 30 miles abeam our original track, and then turned right to parallel our track. There were no published airways out that way!
Immediately post the engine shutdown, we also started to try and call ATC on HF to request a lower level.
Out there 30 miles abeam the airway, we finally stabilized at about FL340, at about the same time we got voice contact with ATC. We requested FL340, and when approved, we turned to regain our flight planned track, and gave a new estimate for the next reporting point.
At the point of track resumption, we reported level at FL340, and continued on to our destination.
You understand, there is no radar coverage of air traffic out there in mid ocean areas.
It turned out to be a bearing failure in the accessory gearbox!
Anyway, the point of all this was to show that the Captain has the authority to make decisions as he sees fit to maintain the safety of the airplane and all those aboard.
This is a minor case, but demonstrates the point, he in fact had no option!
Cheers...FD...
