For perspective, the Canadian Sea King helos are rumored to take 50+ man-hours for every hour in the air, comparable to the C-5 but on a much much smaller airframe.
http://www.defenseindustrydaily.com/saving-the-galaxy-the-c-...
"When it was introduced, back in 1970, the C-5 Galaxy was the largest plane in the world. It also has the highest operating cost of any US Air Force weapon system, owing to extremely high maintenance demands as well as poor fuel economy. Worse, availability rates routinely hover near 50%."
As for the Sea King, I have often read of maintenance ratios of 30 man hours maintenance per hour of flight but 50 is not surprising, either. By comparison, the fantastic (Hughes) MD-500E has a ~.42 man-hours/flight-hours ratio for the airframe, excluding the engine, and that's a very well sorted ship that's far simpler than the Sikorsky.