The CH-47 Chinook: The U.S. army’s largest – The “amphibious” helicopter

Meet the CH-47 Chinook: One would not expect the largest helicopter in the U.S. inventory to also be its fastest. One would expect a small, aggressive-looking attack helicopter such as the AH-64 Apache, the AH-1 Cobra, or the MH-6 Little Bird to be the fastest U.S. military helicopter. But in fact, it is the hulking CH-47 Chinook – a cargo helicopter measuring 98 feet long and 18 feet tall, and weighing 25,000 pounds – that holds the banner as America’s fastest, with a max speed of 196 miles per hour.

Operated by the U.S. Army, the Chinook is one of the heaviest lifting helicopters in the world. Named for the Chinook tribe of Oregon and Washington state, the helicopter entered service in 1962, and it has remained relevant ever since.

The helicopter’s story begins in 1956, when the U.S. Department of Defense decided to replace the Sikorsky CH-37 Mojave, a cargo helicopter with post engines. The Department wanted a fresh design, something that used the recently invented gas turbine-powered engines. The contract was awarded to Vetrol, and work began on what would become a timeless component of U.S. military power.

Vietnam Was a Hard Testing Ground for the CH-47

Vetrol’s final design is distinct among U.S. Army helicopters in that the helicopter features two rotors. Each is powered by a Lycoming T55 turboshaft engine and is mounted to either side of the helicopter’s rear pylon. With two rotors, rotating in opposite directions, the Chinook does not need the anti-torque vertical rotor found on most helicopters. Instead, the Chinook can apply every single watt of power toward generating lift and thrust. Additionally, the twin-rotor configuration is more stable than a single-rotor configuration in situations where weight is added or subtracted mid-flight – a helpful feature for a helicopter designed to lug troops and cargo.

The Chinook made its combat debut during the Vietnam Wαя. At the ωαя’s peak, the U.S. Army operated a full 21 Chinook companies flying 750 airframes. Chinook crews were likely to encounter enemy resistance in Vietnam, and they mounted M60 machine guns in each of the forward doors – occasionally in the rear cargo door, too. In combat, Chinook pilots were frustrated to discover that the helicopter’s two gas turbines could not handle running at full power. Furthermore, the high heat and humidity of Southeast Asia reduced the Chinook’s lifting power by a full 20% in lowlands, and a staggering 30% in the mountains.Of the 750 Chinook airframes that participated in Vietnam, 200 were lost to combat or accident.

CH-47: A Platform for Constant Improvements

Applying the hard lessons of Vietnam, designers modified the Chinook for improved combat operations, a process that continues into the 21st century. New variants of the Chinook have rolled off the assembly line every couple of years, each an improvement on its predecessor. Today, the CH-47F is in service with various upgrades. Among the improvements is a single-piece construction airframe, which reduces vibration in-flight while reducing the need for inspection and maintenance. Meanwhile, more powerful Honeywell engines are capable of providing 4,868 shaft-horsepower. The newest Chinooks can carry a payload of over 21,000 pounds. In the cockpit, the F-variant features a suite of upgraded avionics including a Rockwell Collins Common Avionics Architecture System and a BAE Systems Digital Advanced Flight Control System. Plans are already in place to fund the CH-47F with a Block 3 upgrade after 2025, which could include an even more powerful engine.