Boeing and the U.S. Army inducted the first CH-47F Block II engineering and manufacturing development (EMD) helicopter into final assembly earlier this summer. “Our progress from contract award to final assembly in less than a year is a direct result of the efficiency and reliability of the program,” said Chuck Dabundo, vice president, Boeing Cargo Helicopters and H-47 program manager. “Block II upgrades will help keep Chinooks in operation for the U.S. Army into the 2060s.”

The contract to develop the next-generation Chinook for the U.S. Army conventional and special operations forces was awarded to Boeing in July 2017. The Block II program incorporates several upgrades to increase lift capability and reduce maintenance costs, including Advanced Chinook Rotor Blades (ACRB), an upgraded fuselage, new fuel system, and new drivetrain.

The first Block II aircraft is expected to be completed in 2019, with flight testing scheduled shortly thereafter. First delivery is expected in 2023. Eventually, the Army will upgrade more than 500 Chinooks to the new configuration.

“The U.S. Army is just about out of the CH-47D business,” said Tom Neupert, technical chief, Army Aviation Programs, Cargo. “The remaining aircraft are in the Guard and Reserve and we no longer will have CH-47Ds in the U.S. Army next year.” The Army plans on 473 CH-47Fs and those deliveries are almost complete. “Block II will provide us with the continued capability until such time as the FVL [Future Vertical Lift] decision is made very far out there in the future,” he said.

Neupert detailed the myriad changes and upgrades to Block II aircraft at an industry conference earlier this year. The changes include flight controls, cab, electronics, radios, a stronger pylon, stronger aft section, and a stronger nose that is longer nose to provide more space for electronics. The development of the Advanced Chinook Rotor Blade (ACRB) has been the most challenging of the changes to the rotor system. “We're still utilizing the same [rotor] hub but we're making improvements to that; the same general drive train with some improvements to that. We're hoping to modernize the electrical system a little bit to get additional emergency power going to LED lighting inside and outside the aircraft. The fuel system on the E and F models has three tanks in the pylons on either side, and we're going to a single fuel on either side,” he said. 

Discussing the new ACRB main rotor blades, Neupert said the cup section connects all the hinge points, which are the same on the legacy rotor blades. “The existing blade is a great blade, kind of like a two by eight cutting through the air, a very simple airfoil and incredibly strong,” he said. The new blade is more complex, with “multiple airfoils, an anhedral dihedral tip, and a little bit of a swept tip that provides 1,600 pounds of increased lift in hover. We're still doing some tweaks on it to optimize it,  but it will provide the additional high hot lift capability.”

The ACRB is a fully articulated rotor system and will be easier to maintain than the current design, Neupert said. “The current rotorhead is all oil lubricated in the flapping the lead lag hinge and the pitch change hinge. The lead lag hinges on the new blade will be grease lubricated to eliminate the traditional leak problem. If you've been around a Chinook that's been flying for more than 50 hours you see a lot of oil that's been dripping down the side of the aircraft from those vertical pin bearings.”

Changes to the drivetrain include fashioning the forward transmission rotorshaft from C61 steel and uprating it to 4,960 horsepower. While the combining transmission will not be changed, it will be uprated to 8,266 horsepower twin engine or 4,600 hp single engine. The drive shafting along the spine of the aircraft will be thicker to carry the increased load and will have to be requalified from a fatigue standpoint. The aft transmission gears, cartridges, and housing are also being changed and need to be requalified to 4,960 horsepower. The aft shaft and bearing also are being requalified. Neupert said an old D model has been converted to a test fixture for drivetrain requalification at the Army's Aberdeen, Maryland proving ground and that after those tests the fixture will also be used for the ballistic tests on the new rotor blades.

The other major change is the fuel system. The legacy E and F model system had one big tank and two smaller tanks on each side; however, Neupert points out, “By changing to one big tank [on each side] you get rid of a lot of parts and that saves weight and improves reliability.” The large tank was challenging from both a ballistic and crashworthiness point of view, he said. “But will deliver reduced weight [and] maintenance and a little more fuel.” Neupert said the new monolithic fuel cell survived drop testing from 65 feet. 

He said, even with the multiple upgrades to the aircraft in the Block II program, the upgrade still provides room for the aircraft to grow in terms of avionics and engines. “The structure in place for a bigger engine to increase lift,” he said. However, for now,  “It's a really exciting time in the program. We've got flight test coming up next year. We've got all this component level testing. A lot of moving parts that have a lot of tight schedules and requirements that are moving together.”