According to Defense Industry Daily
Mar 17, 2016 00:20 UTC by Defense Industry Daily staff
The second prototype of the CH-53K helicopter made its maiden flight in January according to Lockheed company Sikorsky. In addition, the first aircraft into the test program has achieved flight envelope expansion to 120 knots for the USMC’s CH-53K King Stallion heavy lift helicopter program. The two are the most heavily instrumented of the Engineering Development Models (EDM) and will focus on structural flight loads and envelope expansion. Two more will join the flight line later this year and will focus on performance, propulsion, and avionics flight qualification.
Sikorsky CH-53K: HERE