Reading Collective Bias's story about the S55T reminds me of an incident I had some years ago when a leak in the cockpit roof caused a drip resulting in a bridging of the hydraulics Primary off, Secondary off test switch.
Both sets of hydraulics failed on me leaving only the emergency system - driven I think by transmission oil pressure on the lateral jacks. All could have been restored by switching off the electrical master switch (fail safe on) but I lacked the courage and free hand to reach for the switch.
From that incident on I made a special effort to learn the aircraft systems and not just skim over the text to pass the type rating exams.
Yes I did manage to get the aircraft down and land it after 20 minutes flying in that condition - pure luck.
Jim