Looking beyond delivery of the last CH-47F/G Chinook model in 2019, Boeing and the US Army are nearing a decision about taking the next step with the venerable heavylift helicopter design.

In discussion are several options ranging from a radical redesign offering 50% more lifting power to slight improvements of the existing configuration and several alternatives in between, says Pat Donnelly, Boeing's CH-47F/G programme manager.

To support a possibly lengthy development phase, decisions about the tandem rotor's future are required soon despite more plans to continue delivering the current model of the Chinook for eight more years.

"We'll be making those decisions more than likely this year," Donnelly says.

The minimum change could involve optimising the rotor hub and transmission to support a 1t lift improvement provided by a common rotor blade currently in development for the F-model, he says.

Alternatively, the army could choose to maximise the lifting capability of the current airframe, raising its lifting power by 30% to about 29,500kg (65,000lb), Donnelly says.

That option would require integrating a new engine, replacing the 4,868shp Honeywell powerplant with a 7,500shp-class turboshaft, he says. Boeing would seek to leverage existing engine cores, rather than develop an all-new propulsion system.

Boeing also has shown army officials a Chinook design that is not limited by current transportability requirements. If a Chinook does not have to fit inside a Boeing C-17, the airframe can be enlarged to lift more than 34,000kg, or about a 50% improvement.

Such a configuration may strain Boeing's ability to describe the design as a growth version of the Chinook. "Is a 75,000lb Chinook still a Chinook or is that a new concept?" Donnelly asked rhetorically.

The army's decision-comes as France and Germany consider buying a new heavylift helicopter to replace aging Sikorsky CH-53s. Boeing has teamed up with Eurocopter to offer a larger version of the CH-47 airframe to Germany that can lift about 33t.

"The French and Germans have expressed an interest in the next generation [Chinook] requirement," Donnelly says.

Meanwhile, the army has been considering options for a new generation of rotocraft, but the emerging joint multirole (JMR) programme is currently focused on developing a replacement for the Sikorsky UH-60 Black Hawk and Boeing AH-64 Apache in 2025.

A heavylift version of the JMR vertical lift technology to replace the Chinook is not planned to be fielded until 2040, Donnelly says.

That strategy has created a potential gap for a growth version of the Chinook to sustain the army's requirement for a heavylift rotorcraft for the next 30 years.

Boeing also needs to start working on a growth design now to avoid a prolonged shutdown at the CH-47F/G production line in Philadelphia, he adds.

Source: Flight International