This article says 'flying on three engines (for an A380) is not preferable:
This is a very strange leap of logic.
The engines have many redundant components and systems. For instance, there are two ignition systems, only one of which is used per flight. MEL relief does exist to allow operation with some of the redundancy unavailable for a limited time. The reason I asked for the Captain’s exact comment, was so that we could possibly resolve just what sort of redundancy he was talking about.
Is this merely due to it not being 'ideal' (in the unlikely event of a further engine failure) or is it a comment about inefficiency?
Do QFi or other operators allow A380s to depart knowing that one engine is unavailable, or does it not meet the minimum (operable) equipment threshold?
Engines are not there for reasons of redundancy. Most flights would be unable to take off with only three engines. There are all sorts of issues with such take offs, not the least of which is that there is insufficient rudder control available to allow full power on the remaining engines until you are already had a very high speed. 3-engine ferries can be done, but not by Australian airlines, and they require specially trained crews, and can only happen in quite restricted circumstances.
Beyond that, all take offs are assessed for the loss of an engine. If you start with one out already, you’re now looking at the loss of two. The climb away scenario of a quad with two out is not pretty.
You won't find me flying with an airline that thinks it's ok to take off with pax on an aircraft that is one engine down.
In the referenced article, Asiana lost an engine in the cruise, and continued to destination. I don’t understand how ML has jumped from that to any thought of 3 engine take offs. Loss of an engine within about 1,500-2,000 miles of destination will normally allow you to continue, as long as the engine failure itself is a clean one (i.e. loss of a mechanical fuel pump simply snuffs the engine, whilst throwing a blade trashes it). There is nothing particularly worthy of comment in the article.