NATIONAL HARBOR, Md. –Sikorsky successfully completed an initial series of tests required by the Naval Air Systems Command (NAVAIR) to verify the structural strength of the Marine Corps’ next-generation CH-53K heavy lift helicopter, the company said here Wednesday at the Sea Air Space convention.

Conducted on a full-size, non-flying aircraft called the static test article (STA), the tests are part of a three-year program to validate the helicopter has the structural integrity to operate safely over its entire flight envelope–from its empty gross weight of 44,000 pounds up to its maximum gross weight of 88,000 pounds with external load, according to a company statement. The STA consists of the cockpit, the cabin, fuel sponsons, a transition section and the tail rotor pylon. The complete assembly is suspended off the ground by the shaft of its main rotor gearbox.

The prototype CH-53K. Photo: Sikorsky
The prototype CH-53K. Photo: Sikorsky

Surrounding support beams hold the numerous hydraulic cylinders that apply the flight and inertial loads to parts of the airframe assembly. Also attached to the STA are component-representative weights that simulate the presence of the engines and landing gear, among other key systems and components.

Sikorsky CH-53K Program Vice President Mike Torok said Wednesday the actual first flight aircraft is approximately 95 percent complete, with main gearbox testing as the only “significant” test remaining. Torok said Sikorsky previously ran gearbox testing, but decided to make some changes and that the company will resume testing “real soon.”

The company has completed a total of six test conditions on the STA, all conducted during 2013 and early 2014. The first four test conditions satisfy pre-flight requirements ahead of a CH-53K flight test aircraft taking to the skies for the first time in the first quarter of fiscal year  2015. Replicating the maximum load conditions encountered while in flight, the four pre-flight tests measured the structural strength of the tail rotor pylon during high and low speed flight maneuvers, the landing gear during impact with the ground and the full airframe structure while under maximum rotor power.

Sikorsky expects the first system development test aircraft (SDTA) airframe to arrive toward the end of the summer as fabrication is underway, Torok said. Company spokesman Frans Jurgens said Wednesday the SDTA aircraft are operational test and evaluation (OT&E) aircraft that are counted as part of the 200 program of record aircraft, even though the company is still under a system development and demonstration (SDD) contract and not yet in production. Jurgens the SDTA are to be used by the Marine Corps to evaluate the CH-53K to perform the mission.

Sikorsky in June received a $435 million Navy contract to build four production-representative SDTAs in support of an initial operational capability (IOC) goal of FY ’19, according to a company statement. The Navy included the SDTA helicopters as an additional line item under the existing $3.5 billion SDD contract initially awarded in 2006. The contract schedule requires Sikorsky to deliver the first SDTA aircraft in 29 months, as of Wednesday, and the fourth by the end of March 2017, when the Marines will begin operational evaluation.

The Marine Corps, per the current program of record, intends to order 200 CH-53K production aircraft and stand up eight operational squadrons and one training squadron to support operational requirements. Eventual production quantities would be determined year-by-year over the life of the program based on funding allocations set by Congress and Defense Department acquisition priorities.

Sikorsky briefing slides presented Wednesday said important program milestones include: first SDTA assembly in FY ’15, first SDTA aircraft delivery and Milestone C in FY ’16, the fourth SDTA aircraft delivery in FY ’17, and IOC in FY ’19.

Sikorsky is a division of

United Technologies Corp. [UTX].