This amazing helicopter is the latest from Kaman Aerospace.   It incorporates the "unique intermeshing rotor technology with servo-flap control".  The intermeshing rotors cancel each other's torque reactions which negates the need for a tail rotor.  This allows the K-MAX to direct all the engine's power into lifting force.  The strength of this design is apparent when considering an empty weight of 4,800 lb (2,178 kg) and an external lifting capacity of 6,000 lb (2,722  kg).  I have always wanted to build one for a flight sim after seeing a forest service K-MAX fly around Boise, Idaho years ago.