The "System Demonstration Test Articles" were ordered by the Naval Air Systems Command through a $435 million cost-plus-incentive contract.
"The SDTA contract represents an exciting and significant milestone in our program," said Col. Robert Pridgen, the Heavy Lift Helicopters program manager for NAVAIR.
"We are well on our way to making the CH-53K a reality for our Marines and our naval fleet. "The capability this aircraft brings, in every clime and place, is critical to sustaining the future missions of the Marine Air/Ground Task Force."
The CH-53K being developed features three engines, new composite rotor blades and a cabin that is wider than other CH-53 variants. It has a cruise speed of 196 mph, a range of 454 nautical miles and a service ceiling of more than 14,000 feet.
"The four SDTA aircraft are based on the configuration of the fourth and final flight test aircraft currently being assembled on the prototype production line," said Dr. Michael Torok, Sikorsky's CH-53K Program vice president. "We truly appreciate the high level of confidence the Navy and Marine Corps have shown to the CH-53K team as we move forward with this important next phase of the program."
Sikorsky said the four helicopters were added as an additional contract line item under an existing $3.5 billion System Development and Demonstration contract awarded in 2006.
Sikorsky will deliver the first SDTA aircraft in 39 months. The fourth will be delivered in early 2017.
Notable deaths of 2014 [PHOTOS]