Sikorsky and the US Marine Corps on 5 May formally unveiled and christened the CH-53K as the King Stallion, a clean-sheet replacement in nearly all but name for the CH-53E Super Stallion.

"This is what I would call a fifth-generation helicopter," says Marine commandant Gen James Amos, making a smirking reference to the stealthy and supersonic fleets of Lockheed Martin F-22 and F-35 fighters.

CH-53K unveil - Sikorsky


The CH-53K will never be mistaken for being stealthy or supersonic, but it is endowed with many advanced features. Some critical technologies – such as a 5,900kg (13,000lb) transmission and gear assembly, which itself weighs more than a UH-60 Black Hawk – are mandated by the CH-53K's 39,900 maximum take-off weight, which is second only in girth to the Mil Mi-26.

The CH-53K drive train – featuring a split-torque transmission, elastomeric rotor hub and 7,200shp General Electric GE38-1B turboshaft engines – push the King Stallion decades beyond the technology of the CH-53E.

Other advance systems are necessary to fulfill the Marines' requirement for a heavy lift helicopter that can hoist twice the external load of the CH-53E, yet remain within the same rotor diameter and footprint as its predecessor.

"We tried to convince the navy to make the ship bigger, but they wouldn't," jokes Col Robert Pridgen, the CH-53K programme manager.

If the hulls of the Marines' amphibious carriers remained fixed, the CH-53K would have to pack more power and control into the same package in order to double the load carrying capacity to 12,200kg.

Fly-by-wire flight controls – the fourth such application on a Sikorsky aircraft – and an all-composite fuselage delivered by Spirit AeroSystems, GKN Aerospace and Aurora Flight Systems minimise the structural and system weight of the aircraft.

CH-53K runway - Sikorsky


The USMC launched the CH-53K programme with a contract award to Sikorsky in 2006. A slow start, however, forced the Marines to rebaseline the programme twice, delaying the initial operational capability milestone by four years to Fiscal 2019.

The development programme hit another major snag last year, Pridgen says. An accessory gear in one of the CH-53K's four main gearbox failed during a test, revealing a "small crack", he says.

The other three gearboxes were inspected and revealed no problems, so the programme is treating the crack as a one-off production flaw. Sikorsky has adjusted its production process, but there are no plans to redesign the gear in the short-term. The last of the four main gearboxes completed an initial phase of testing last week, and so far shows no signs of damage.

But the discovery took a toll on the programme's schedule. First flight has moved from "late summer" to "the end of the year".

The delay comes at a sensitive time for the programme. The CH-53K survived the impact of a partial sequestration-imposed budget cut in Fiscal 2015, but it faces a $1.04 billion cut over the next five years if Congress does not repeal sequestration in the Fiscal 2016 budget now taking shape within the Obama Administration.

Rear Adm CJ Jaynes, a programme executive officer for Naval Air Systems Command, declines to comment on the chances of the CH-53K surviving the sequestration process unscathed again in Fiscal 2016.

"I think it's really too early to tell," Jaynes says.

The CH-53K is critical to the USMC's warfighting capability, she says.

The aircraft's increased external load-carrying capacity means it can carry two up-armoured Humvees up to 110nm inland. Unlike the single-load of the CH-53E, the CH-53K also can drop off three loads at different points on the same flight.

"This helicopter is going to change the game for the US Marine Corps," she says.