Without question the finest transport helicopter ever designed. The Mk 3 is based on the US SOE version with larger external fuel tank to allow greater volume in the cabin (but not weight). To compensate for the reduced hover performance, the US version is fitted with a refuelling probe. (Heilcopters are power hungry in the hover but don't need as much horsepower in the cruise). As a result of the design it has a lower lifting capacity than the Mk 2 it will never be as capable as the latter so talk of harmonising the fleet is just pie in the sky. And let's not even start talking about the different handling characteristics!