Military

Second Experimental Block II Chinook Enters Assembly Ahead of Schedule

By Dan Parsons | September 28, 2018
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A CH-47F Chinook helicopter with 3rd General Support Aviation Battalion, 82nd Combat Aviation Brigade maneuvers to pick up an M119A3 howitzer during sling load operations on Fort Bragg, N.C., May 4. Sling loading artillery pieces allow the artillery commander to place artillery equipment at a better location to provide ground forces with artillery support. (U.S. Army photo by Sgt. Steven Galimore)

A CH-47F Chinook helicopter with 3rd General Support Aviation Battalion, 82nd Combat Aviation Brigade maneuvers to pick up an M119A3 howitzer during sling load operations on Fort Bragg, N.C., May 4. (U.S. Army photo by Sgt. Steven Galimore)

Boeing has loaded the second of three Ch-47F Block II aircraft into final assembly, and soon will have all three experimental performance-enhanced Chinooks being built up to achieve first flight next year.

Both the first two aircraft entered assembly ahead of schedule and Boeing has been able to modestly speed up building the prototypes that will test the upgrades the Army eventually could retrofit onto 500 legacy Chinooks, Randy Rotte, director of cargo helicopters and future vertical lift at Boeing, told R&WI in a Sept 27 interview.

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“We went from three days early to seven days early on the second one; it’s possible some of that was parts come in earlier couple with we got a little bit better at loading in the jig. … I don’t know if that trend is going to continue with the third one, but I’d be willing to bet it will be early.”

The program achieved milestone B in April 2017 and Boeing is now producing the evolutionary upgrade package for the U.S. Army and Special Operations Forces under a $276 million contract awarded in 2017.The first aircraft entered the final assembly line eleven months later, three days ahead of schedule.

About six weeks later, in mid-August, the second EMD aircraft loaded into the final assembly line seven days early, Rotte said.

The third EMD Chinook’s structure is being assembled and should enter final assembly “soon,” he said.

“All three are currently ahead of schedule and we’re actually, so far, under cost,” Rotte said.

A major component of the Block II upgrades is the advanced Chinook rotor blade (ACRB), which when installed should provide more than the Army-require 1,500 pounds of lift at 4,000 feet elevation and 95-degree temperature. Boeing has demonstrated at least 1,600 pounds of additional lift with its new composite blades.

Block II was designed to achieve specific performance enhancement metrics, including a 22,000 pound payload and high/hot hover performance at 4,000 ft on a 95-deg F day. Maximum takeoff weight is boosted to 54,000 pounds with the goal of carrying a joint light tactical vehicle.

Included in the upgrade package are improved avionics, speed enhancements and a beefier drivetrain that will transfer greater power from the 20% more powerful Honeywell T55 engines to all new, swept-tip advanced Chinook rotor blades. Without any other upgrades, the blades are designed to provide an additional 1,500 pounds of lift.

The first 18 inches of the new rotor blades are identical to the current blades so they can be installed on older Chinooks. Rotte said they could be offered as a single-component upgrade for Block I aircraft.

“The fact that the first 18 inches of the blades are identical was all about not having to make
changes to the hub if we didn’t want to and the potential of those being retrofittable to a Block I Chinook,” he said.

But having super-performance rotor blades does not provide capability enhancement for all Chinook operators. At sea level, the aircraft performs well in its current configuration and has plenty of lift margin, Rotte said. When operating in “high/hot” conditions, the blades provide extra performance lost to the inefficient operation of the engines at altitude and loss of lift in thinner air.

“When I’m flying at sea level, I don’t need additional lift from my blades, because the engines operate really well at that lower altitude and in cooler temperatures,” Rotte said. “When you start getting high and hot, the engines don’t produce as much power. That’s where the blades kick in.”

At sea level, a Block I Chinook with advanced rotor blades would not be able to access the increased lift capacity because its legacy transmission could handle the torque they create. Even with an upgraded drivetrain, the legacy Chinook airframe is limited to 50,000 pounds takeoff weight. Block II beefs up the airframe to support 54,000 pounds.

“So now, this holistic set of improvements on Block II gives you more capability at high/hot as well as more capability as sea level standard,” Rotte said. “You had to touch all three of those areas to make that happen.”

First delivery of a production Block II Chinook to the Army is expected in 2023. The Army plans to eventually upgrade more than 500 Chinooks — its entire fleet of CH-47Fs — to Block II configuration. The Army is still in the process of bringing all of its Chinooks to F-model configuration. Boeing will bring in an estimated $14 billion and change to bring the Army’s entire fleet to F-model configuration.

Included in the upgrade package are improved avionics, speed enhancements and a beefier drivetrain that will transfer greater power from the 20% more powerful Honeywell T55 engines to all new, swept-tip advanced Chinook rotor blades. Without any other upgrades, the blades are designed to provide an additional 1,500 pounds of lift.

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