As the US Department of Defense pursues a family of high-speed rotorcraft, Boeing officials say two stalwarts of the current fleet – the AH-64 Apache and CH-47 Chinook – must be kept viable for decades to come.
The AH-64E entered service last year, but an F-model is already on the drawing boards. Some upgrades – the 3,000shp turboshaft in development under the army’s improved turbine engine programme (ITEP) – have been openly discussed.
Boeing officials also believe high-speed capabilities can be added to the 40-year-old Apache design. Possibilities include adding a retractable landing gear, wingstubs to offload lift from a single main rotor in high-speed cruise and a tail rotor that articulates 90° to provide forward thrust.
Meanwhile, Boeing is scheduled to deliver the last CH-47F in Fiscal 2019, ending a production run that began in 1961. Boeing now is proposing to remanufacture F-models with a higher gross weight.
In the past, Boeing has proposed a 31,800kg (70,000lb) class variant with a 30cm (1in) wider fuselage to accommodate up-armoured HMMWV (Humvee) trucks. Budget realities have forced the company to propose a more modest solution now. The “H-model” CH-47, as proposed, strengthens the airframe and the propulsion system to lift 24,500kg, or about 1,810kg more than the existing helicopter.
The proposals seem to clash with the company’s interests in the Future Vertical Lift (FVL) programme. Boeing has teamed with Sikorsky to develop the high-speed SB-1 Defiant for the joint multi-role technology demonstrator (JMR-TD), which is a intended to be a scaled down version of the FVL-Medium concept to replace the Sikorsky UH-60 Black Hawk after 2030.
Boeing insists there is no contradiction, however.
“The issue is it takes a long time to develop an aircraft and field it, and we [and] the army have to keep the current fleet viable and relevant,” says Mike Burke, Boeing’s director of business development for attack helicopters.
David Palm, director of business development for vertical lift, also notes that the AH-64 is not scheduled to be replaced by the attack version of the FVL aircraft until 2040. The CH-47F is not due for retirement until 2060, a full century after its first flight.
“We believe there’s going to be another – at least one more – turn of the Apache technology,” Palm says.
Boeing’s agreement with Sikorsky on the SB-1 allows both companies to transfer technologies developed for the JMR-TD programme to aircraft already in production.