It is true what is said above. But also, because of all the anti-ice equipement (wich is electrical) the engines loose a lot of power so, RPM's go down. If the RPM's of your engines go below a certain point (91 or 92% IIRC) the revolutions are too low for the generator to be effective so, automatically it shuts down. And disabling any electrical equipment on your Hip. I did complete the Elbrus mission, only just... It is quite an exciting mission, even tough there is no shooting involved.