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The U.S. Army recently awarded Boeing a $136 million contract for the first four CH-47F Chinook Block II aircraft, but the service has no intention of purchasing the problematic advanced rotor blades at the center of the upgrade package.
“There is not an intent, right now, for the Army to proceed at all with the ACRB,” short for the Advanced Chinook Rotor Blade, Brig. Gen. Rob Barrie, the Army’s top aviation procurement official, told Vertical Oct. 12 at the Association of the U.S. Army’s (AUSA’s) annual conference in Washington, D.C.
Through various component upgrades, Block II is designed to increase the CH-47F’s maximum gross weight to 54,000 pounds (24,500 kilograms). Improvements include an enhanced drive train and rotor system — delivering 10 percent more torque capacity — designed to operate with a more powerful drop-in engine that is in development. The aircraft’s fuselage, fuel system and wiring also are upgraded with stronger, more reliable parts.
Perhaps most important is the introduction of Boeing’s ACRB. The all-composite blades feature a swept-tip design that should provide an additional 1,500 lb. (680 kg) of lift.
The new blades hit a snag during testing when Army pilots reported that they produced excessive vibrations on the ground, in hover, and forward flight that an Army report determined “may cause a safety of flight risk.” Barrie said the composite blades also created stall on the aft rotor system during testing.
“Because of those two things and the additional work that would be required and the additional cost and additional weight of a vibration system, the Army said we’re not going to proceed with the ACRBs and that’s why it wasn’t included in the configuration” of the recently purchased Block II aircraft, Barrie said.
Boeing insists there is no safety of flight risk and continues to test the aircraft with the ACRBs installed in Mesa, Arizona. Technically, the Army has the option to fund the new blades if and when it decides they are worth the effort and cash.
The recently awarded Lot I contract includes the four aircraft themselves and unfunded options for ACRBs pending a limited user test by the Army initially scheduled for March. That testing, in which Army pilots and Boeing engineers would address the vibration issues specifically, has not been rescheduled. If the Army does not fund the new blades in time for delivery of the first four Block II Chinooks, they would be equipped with standard fiberglass blades, said Andy Builta, Boeing vice president and H-47 program manager.
“The ACRBs would be a different award, an exercise of an option at a later time,” Builta explained.
Boeing has completed 800 hours of testing on the three engineering and manufacturing development (EMD) Chinooks built in Philadelphia and flown to Mesa, Arizona, where they continue to fly. Most of that testing and the cross-country hop was performed with the ACRBs installed, Builta said.