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Piasecki Refreshes Hybrid Chinook Concept
Guy Norris April 29, 2024
Credit: GN/AWSTAURORA, Colorado—Piasecki Aircraft says an updated version of long-running concept studies of a radically modified Boeing CH-47 Chinook combining the helicopter’s existing twin-rotor system with a tiltwing and twin tilting ducted fans has become more relevant with the U.S. Army’s growing drive for longer range troop transport and logistics support.
Company President and CEO John Piasecki says a modernized version of the concept would also fit with the service’s recent decision to overhaul its aviation modernization plans following the cancellation of the Future Attack Reconnaissance Aircraft (FARA) program.
Canceling FARA and the Sikorsky UH-60V Black Hawk has freed up resources for the Army to commit to a multiyear procurement of the UH-60M Black Hawk along with associated upgrades. The service will enter the upgraded CH-47F Block II Chinook into production, with a path to full-rate production.
The Army’s decision to continue as planned with development of the Bell V-280, the winner of the Future Long Range Assault Aircraft (FLRAA), is the real driver for the proposed hybrid Chinook, Piasecki says. He spoke to Aviation Week April 25 at the Army Aviation Association of America’s summit here.
“The Army has expanded its future vertical lift capability with the V280, so you’re going to have to sustain the troops at longer ranges. So, it’s a concept for upgrading the CH-47,” he adds.
In 2008 Piasecki and Boeing revealed they had worked together on a “minimum” modification of the Chinook, called the Tilt Duct CH-47, which included a simplified version of the Vectored Thrust Ducted Propeller flown on Piasecki’s X-49A Speedhawk. Other proposed changes to the basic CH-47 at the time included bigger engines to drive the rotors and props, relocating the fuel tanks under the cabin, streamlining the aft fuselage and fairing the hubs to reduce drag.
Piasecki’s updated vision adds a set of high-aspect ratio tilt wings, each about the length of one of the helicopter’s existing rotor blades. The wings are mounted on pivots located around mid-fuselage. The concept retains the tilting ducted fans which now closely resemble units in development by the company for the U.S. Air Force-funded Aerial Reconfigurable Embedded System (ARES) vertical-takeoff-and-landing (VTOL) uncrewed aircraft system (UAS). The tilt ducts are mounted on struts on either side of the aft rotor pylon.
“It takes off vertically with the wings angled down and the ducts positioned vertically. Then it transitions into forward flight and unloads the rotor so you can carry more without damaging the system, and you can go fast so you can get the throughput needed to support troops over much longer distances,” Piasecki says. The added lift from the wing and thrust from the ducts would help delay the onset of retreating blade stall, enabling higher speed flight, he adds.
Like the earlier study, the updated modification would also include more powerful engines. Piasecki says this would see the CH-47’s existing Honeywell T55 turboshafts replaced with the more powerful 7,500 shp GE Aerospace GE38 engine developed for the CH-53K heavylift helicopter.
“These engines have got more power than this drive system can handle. So we would max out the power to the rotors for maximum lift, then we would shunt the excess power output to the fan so they produce lift in hover as well,” Piasecki says.
“The net effect is your useful load is increased, even though you’re putting the wing and thrusters on it. Then you can use the engines to go faster and they’ve got better (performance) specifics,” he notes.
