The reason why the S61 is being 'phased out' is because it does not meet the more stringent certification requirements of FAR 29 (post AL 47) alluded to in most of Nick Lappos's posts.
The S61 can meet the second segment climb and en-route performance required by most operational regulations but its legs are a little short. It will not be able meet the more stringent requirements for PC2e (with a decent payload) that the major oil companies are now requiring for new contracts.
Mars