In general, a multi-engine aircraft (fixed wing or rotary) will not crash if one engine fails. Some can fly with one engine gone, others cannot, but the ones that cannot will still have enough power to make some kind of controlled landing.
However, if you have an explosion or fire in an engine (rather than it just stops working) that's a different matter. If the engines are adjacent then it's only a matter of time ( and probably not very much time) before the other ones stops too, probably just as catastrophically.
In other words, make the explosion convincing (though not huge) and the MH47 is definitely kissing the dirt.