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Sikorsky's CH-53K could reach its maximum lift capability by 2017, but the US Naval Air Systems Command is prioritising a smaller flight envelope for an operational assessment.

The manufacturer recently completed a key test for the US Marine Corps after flying the helicopter 100ft above the ground with a 12,250kg (27,000lb) payload. The USMC is still targeting a 13,600kg payload capacity, though early analysis indicated the helicopter would struggle to meet that threshold.

During the payload evaluation, the helicopter demonstrated some excess power when it continued to climb after lifting the 12,250kg load, Rear Adm Dean Peters, NAVAIR program executive officer told reporters at Farnborough on Tuesday. Still, the USMC is not looking to immediately exceed its payload requirement.

“Our priorities are to get an envelope that the operational testers can utilise for an operational assessment,” Peters says. “So it’s not necessarily a priority to get to the maximum lift capability or even to the maximum airspeed that the aircraft can achieve.”

The CH-53K must be capable of lifting a 12,250kg load at 6,000ft density altitude at a temperature of 35°C, though this will rise in cooler and lower conditions, Peters says. The King Stallion promises better range than its predecessor, the 1980-era CH-53E Super Stallion, and triple the payload in hot weather.

“There’s lots of times where we’ll be at sea level at a lower density altitude and probably at a lower temperature,” he says. “So that navy hot day requirement is an extreme environment.”

Peters remains optimistic on the King Stallion's progress, despite an eight-month delay to low-rate initial production following a main gearbox failure last year.

While the USMC has already proved the CH-53K’s manual blade fold, testing remains to be completed on the platform's automatic blade and tail fold mechanism.