Defense Media Network

The U.S. Army Is Pondering a “Growth Variant” of the CH-47 Chinook

Time to supersize a 50-year-old legend?

The first helicopter in the CH-47 Chinook series, known as the time as a YCH-1B, made its maiden flight on Sept. 21, 1961. By the time the U.S. Army and aircraft manufacturer Boeing celebrated its 50th anniversary this year, the tandem, twin-rotor Chinook had left an indelible mark on aviation history and the nation’s top soldiers were pondering a future “growth variant” that would extend the life of the Chinook fleet beyond 2020.

The first step toward extending the Chinook’s already impressive lifetime was the establishment in September of a modernization program office within the acquisition headquarters for the Army aviation community at Redstone Arsenal, Ala. Also in September, Boeing officially opened its renovated Building 361 in Ridley Park, Pa., where the company assembles Chinooks.


Chinook Progress

Chinooks poured off the assembly line in CH-47A through MH-47G models during the helicopter’s first half-century. Boeing is in the process of rebuilding CH-47D Chinooks to bring them up to the current CH-47F standard.

One important difference between the D and F models: the D, which dates to 1982, was built with rivets while the F has a monolithic fuselage. “Rivets and the constant vibration of rotary wing flight don’t go well together,” said an Army aviator.

The Army has long planned to upgrade 397 Ds to F status and to add additional, new-build CH-47Fs. The “program of record” calls for 510 CH-47Fs. Boeing has delivered 143 CH-47Fs, is completing a multi-year contract for 215, and is expected to receive a second multi-year contract. The Army claims that awarding a multi-year contract trims about 15 percent from the price of an aircraft.

For special operations forces, Boeing built 62 specially-equipped MH-47Gs, all of which were rebuilt from earlier CH-47D, MH-47D and MH-47E airframes in a service-life extension program. (Three MH-47Es have been lost in operational accidents or in combat). The final MH-47G, optimized for long-distance, low-level night operations, was delivered last March 14.

On CH-47F and MH-47G models, the army introduced the Rockwell Collins common avionics architecture system (CAAS) cockpit, also used on other new Army aircraft, and the BAE Systems digital advanced flight control system (DAFCS).

The new office at Redstone, to be headed by Col. Bob Marion, will draw up the Army’s requirements for the “growth variant” of the Chinook, or CH-47H, that the service wants after 2020. An early decision that must be made is whether to create a “Chinook on steroids” by significantly widening the fuselage of the CH-47H in order to increase the load the “growth variant” can carry. That step is technically feasible but would mean that the new Chinook version could no longer be transported aboard a C-17 Globemaster III airlifter.

One key to the success of the Chinook has been the T55 gas turbine engine, originally built by Lycoming and now a Honeywell product. Although the basic design is as old as the Chinook, the engine has growth potential today. Army officers say a projected T55-GA-715 coupled with an improved rotor hub and transmission could replace the current 4,870 shaft horsepower T55-GA-714A. Or, the service could seek an entirely new engine. Studies show the Chinook could accommodate a 7,500 shaft horsepower engine, and powerplants in that range are readily available.


Sikorsky Stallion

As a sidelight to the ongoing Chinook saga, Sikorsky is preparing to offer its new-generation CH-53K Super Sea Stallion heavy-lift helicopter to the Army as a higher-tech alternative to the post-2020 “growth variant” CH-47H Chinook.

The Marine Corps wants 200 CH-53K helicopters starting in 2018 to replace its CH-53E versions – the CH-53E being one of the few aircraft in U.S. service that has never had a service-life upgrade. If Sikorsky could find a wider purchasing base for the CH-53K, the Marine program would stand a better chance of survival as budget debates continue in Washington.

What happens to the future of the Chinook, and whether a CH-47H can make its debut after the CH-47F line shuts down in 2019, will depend on a larger picture of Army aviation that one observer calls “a moveable feast.” The Army has ambitious long-term plans for a family of Joint Multi-Role (JMR) aircraft to replace every helicopter now in service and for an Armed Aerial Scout (AAS) to replace the OH-58D Kiowa Warrior. In the shorter term, the service also wants to maintain multi-year contracts for AH-64D Apache Longbows and UH-60M Black Hawks in addition to CH-47Fs.

Not everyone believes another aircraft can replace the venerable Chinook.

Said Marion: “It works better than any other cargo helicopter in the world.”


Robert F. Dorr is an author, U.S. Air Force veteran, and retired American diplomat who...