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Wednesday, September 1, 2010

U.S. Army’s Advanced CH-47F Chinook Proves Its Value

By Douglas Nelms

Boeing’s newest Chinook program hit the century mark in July with rollout of the 100th CH-47F. The “F” model Chinook first flew in April 2005, became operational in mid-2007, and has proven to have exceptional reliability and combat sustainability in Iraq and Afghanistan, according to LTG William Phillips, principal military deputy to the Assistant Secretary of the Army for acquisition, logistics and technology. Speaking at the rollout ceremony, Phillips said that the CH-47F has had an operational readiness record well in excess of 80 percent with over 50,000 flight hours and some 2,600 missions. The “F” model is also the Army’s first Chinook with a fully digital cockpit. It has a Rockwell Collins Common Avionics Architecture System (CAAS) interfacing with a Digital Advanced Flight Control System (DAFCS). BAE Systems provides hardware for the DAFCS to Boeing, where it is loaded with the flight control laws that essentially operate the aircraft, said Paul Cooke, business development director, defense avionics for BAE Systems.

The DAFCS is essentially a three-axis autopilot for pitch, roll and yaw, he said. “This gives the pilot stability in those axis, maintains airspeed, altitude, bank angle and heading, and performs automatic heading adjustments from the pilot’s settings. In the coupled mode [with the CAAS], the pilot does all of his planning on the CAAS, then the CAAS and DAFCS work together over the 1553 avionics bus,” Cooke said. Boeing noted that “these greatly reduce the pilot workload, providing better situational awareness [and] dramatically improved flight control capabilities.” The system allows pilots to pre-program mission requirements prior to takeoff, feeding the information to the aircraft’s control systems from a mission card. This includes flight path to destination, initial descent point, hover position at a default altitude, and return route. The computerized mission planning system also allows the pilot to change the flight plan in route in the event of situations such as new enemy locations or a change of mission, Killen said.

The automatic descent and hover to a pre-selected point capability also provides precision stabilized hover-hold for external load pickups and drop-offs. In the event of a brownout or whiteout condition, the pilot can immediately stabilize the aircraft in position, then “beep” the aircraft down using a radar altimeter combined with a velocity and acceleration cue depicted in the multifunction display (MFD) screens. Flight and aircraft information is provided on five MFD screens, with required information available on any screen. “The pilots will always have flight information, such as VSI, on the screens, and can pull up any emergency or warning information as required,” said LTC Bradley Killen, project manager for the CH-47 program. The CAAS hardware systems include MFD-268C3 units, CDU-7000 control display units, PSM-8600 processor switch modules and VPM-8600 video processor modules, as well as NVIS-compatible AMLCD screens and controls.

The Army plans to order a total of 464 CH-47Fs, obtained through a program combining rebuilt D models and new builds. As CH-47Ds are replaced by F models, they return to Boeing where usable dynamic components such as rotor and transmission systems are reconditioned to zero time, then placed in totally new airframes. Whereas earlier Chinook airframes were manufactured by riveting metal sheets together, F-model airframes are high-speed machined, reducing parts count by about 50 percent while making the fuselage stronger. The aircraft is already rated at a 24,000-pound payload, and Boeing is currently assessing the new monolithic airframe to see if its structural strength will allow higher gross weights. The CH-47F is powered by two FADEC-controlled Honeywell T55-GA-714 engines rated at 4,733 shp each. These replace the T55-GA-712s rated at 3,750 shp used on the CH-47D.

As the F models roll out of Boeing’s Ridley Township, Pa. facility, they are being delivered in batches of roughly 12–14 aircraft to the Army units designated to receive them. The 99th CH-47F completed the sixth batch, assigned to the 10th Mountain Division in New York. The destination of the 100th CH-47F and remaining seventh batch is yet to be announced, but expected to go to the 25th Division in Hawaii.

The aircraft are being produced and delivered through two separate contracts, Killen said. The first contracts expires in FY2012, with the second contract being picked up in FY2013 and running through 2018. Killen also noted that “F” model training for both pilots and maintainers is being conducted through the Army’s New Equipment Training program, with NET teams assigned to each unit receiving a batch of CH-47Fs. (September 2010 Program Insider, from Rotorcraft Report)

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