Much like the military already do then
Indeed crab.. Our Airbus heli type has "height loss on eng failure" charts (commonly called "flyaway" charts) which gives us a well defined height on which to base our "flyaway" call on.... Works very well with the old "towering OGE" departures, or assessing the height to conduct a hoist/winch. It does have a whole bunch of conditions though (2 sec reaction time, pitch to 15 deg ND, Nr>97%, 40KIAS reduce pitch, ect ect.
We even have a Vtoss presented to us to consider..
I was always under the impression that us mil guys were way behind the drag curve (pardon the pun) when it comes to flying the pucker profiles to achieve the lowest risk approaches / departures. (Our assessments of "flyaway" and "committed" were very subjective but are getting less so as we get access to more performance data on our aircraft)
I find it hard to believe any of the civvy OEM's and operators would not have access to very specific performance data / criteria for approaches, departures and hovers in the OEI case. (Perhaps I am confusing this with Category A or PC1? Hopefully someone can enlighten me, happy to be educated on this!)