It is rare to spot something truly new in one of the hundreds of reports issued each year by US Department of Defense's legion of internal think-tanks, much less learn of the existence of an undisclosed, revolutionary helicopter development project. But it can happen.
And so it is with the recently published, 175-page report of the Defense Science Board Task Force on Mobility . Under the subheading, "Future capabilities" (page 56), it casually unveils a US Marine Corps proposal to build the largest helicopter in history. It lists two candidates to replace the USMC's venerable CH-53E - the CH-53X and the CH-53X+.
The CH-53X is now called the Heavy Lift Rotorcraft (HLR), and is correctly described by the DSB as a proposal to develop a new variant of the CH-53E that can transport a 27,000lb payload about 110nm.
Then comes the news about the CH-53X+. Here's what the report says:
"The CH-53X+ is designed to carry a 40,000-pound payload to a range of 250 nautical miles. It would require making major aerodynamic and structural changes to the CH-53E. Maintaining current disc loading would require a 116- to 120-foot-diameter rotor. This modification would in turn require a redesigned fuselage and an extended tail rotor boom.
"Some members of the helicopter design community have observed that the capabilities projected for the CH-53X+ represent a major challenge. The introduction of a new engine, a much larger rotor, higher disc loading, a new tail boom, and (probably) a new transmission amounts to a new aircraft, with many design unknowns.
"Further, a helicopter with a rotor diameter of 120 feet and takeoff weight of approximately 160,000 pounds may not be compatible with existing ships. The anticipated requirement to carry more than 40,000 pounds to ranges of 250 to 300 miles is similar to the capabilities of the Russian Mi-26 HALO helicopter. The existence of the Mi-26 suggests that the technology for such an aircraft already lies beyond technology readiness level 6. However, it is not clear that the airframe of this aircraft has the dimensions to allow internal carriage of ISO containers or Stryker vehicles."
Ordinarily, this little blurb would make quite the news story. But there's a problem - neither Sikorsky nor the Naval Air Systems Command nor the US Marine Corps' requirements branch apparently has knowledge of nor interest in such a massive new helicopter. Representatives of each organisation have theorised that the DSB may have confused the CH-53X+ proposal with a possibly aged - and long-forgotten, if it ever existed - concept for a CH-53 variant for the separate Joint Heavy Lift proposal, which is a US Army-led programme.
So perhaps for now we'll call the CH-53X+ a mystery. But if anyone spots a new variant of a CH-53E that has a fuselage the size of a Lockheed Martin C-130 Hercules, give us a ring.