Sikorsky Aircraft has rescheduled the maiden flight test of its new CH-53K King Stallion heavy-lift helicopter in order to complete testing fixes to its gearbox and other problems.
Unnamed US Navy programme officials were reported by The Wall Street Journal as saying that the gearbox problems have been resolved, but still require additional testing.
Originally scheduled to make its first flight in June 2014, the helicopter experienced problems with the gearbox, drive shaft and other parts during ground tests, which postponed the schedule to late-2014 and then to mid-2015.
When questioned about the helicopter's progress, Sikorsky directed questions to the US Navy.
US Navy Aviation Program Office spokeswoman said: "We are still undergoing ground tests to measure and verify the ability of the drive system, transmissions, engines and flight control system to safely fly the CH-53K helicopter across multiple flight scenarios.
"At this time, we do not have a specific date for a first flight, but do anticipate prior to the end of this calendar year, fall of 2015."
Subject to the completion of flight tests, the US Department of Defense is expected to announce a final decision of when to begin production in 2016.
The US Marine Corps (USMC) is planning to procure 200 helicopters at a cost of approximately $25.5bn.
Unveiled in May 2014, the helicopter is scheduled to replace the ageing fleet of CH-53E Super Stallions, which was extensively used in Iraq and Afghanistan.
According to the Government Accountability Office (GAO), the helicopter can carry more armoured vehicles, equipment and personnel further inland from ships. It is scheduled to enter service with the USMC in 2019.
Image: The CH-53K King Stallion helicopter during the roll-out ceremony at the Sikorsky Headquarters in Stratford, Connecticut, US. Photo: courtesy of Sgt Mallory S VanderSchans.