(i) in times of engine failure
(ii) whenever an engine failed
Halliday & Matthiessen (1999: 537):
From a purely descriptive point of view, each version is metaphorical from the standpoint of the other; there is no inherent priority accorded to either. Once we bring in considerations of history, however, a clear priority emerges; and it is the same priority whichever of the three diachronic dimensions we choose to invoke — the phylogenetic (history of the language), the ontogenetic (history of the individual) or the logogenetic (history of the text). In all these three histories, version (ii), the clausal comes first.
This form of construal evolved first in the history of English; version (i) emerged only as the result of a long process of later evolution. It comes first in the life of a child; children master version (i) only after a long (in terms of their young lives) process of becoming literate and being educated And it comes first in the unfolding of a text; we are much more likely to be told first that engines fail and only then to hear about a phenomenon of engine failure.
Once we take note of progression in time, then given a pair of such expressions we can identify one of the two as the more metaphorical. The process is one of movement away from what we referred to as a "congruent" form.