In 1960, Boeing bought Vertol Aircraft Co., a helicopter manufacturer in Philadelphia, Pa. The company had three tandem-rotor helicopters under production: the Chinook for the U.S. Army, the Sea Knight for the U.S. Navy and Marines, and the commercial 107-11 for the airlines.
Vertol had started out as the P-V Engineering Forum, owned by Frank Piasecki, which established the “banana shaped” two-rotor helicopter in 1945. Piasecki left the corporation in 1955, and it was renamed Vertol the following year.
The first in the long line of Chinooks was the YHC-1B tandem-rotor transport helicopter that rolled out in 1961. It was designed to serve the U.S. Army and Air Force as a medium-lift helicopter and evolved into several versions.
The first fully equipped Army Chinook, designated the CH-47A, entered service in August 1962 with a gross weight of 33,000 pounds (14,969 kilograms). Boeing introduced the CH-47B in 1966 with an improved airframe and power plant provided by the T55-l-7C engines. The gross weight rose to 40,000 pounds (18,144 kilograms). The CH-47C was developed in 1967 in response to the Army’s request for transporting a 15,000-pound (6804-kilogram) payload a distance of 30 nautical miles (56 kilometers) radius on a 95-degree Fahrenheit (35-degree Celsius ) day at 4,000 feet (1219 meters). It was powered by T55-l-11 engines and had a gross weight capability of 46,000 pounds (20,865 kilograms).
Chinooks were first used in combat in 1965 during the Vietnam conflict. During the last days of the war, one Chinook is reported to have carried 147 refugees in a single lift. CH-47A, B and C models served with until the war’s end in 1975.
The Mil Mi-26 is a twin-engine heavy transport helicopter designed and manufactured by Mil Moscow Helicopter Plant, Russia, for both military and civilian roles. It is the second largest and powerful helicopter in the world, and entered into service in 1985.
The helicopter’s maiden flight took place in December 1977. About 276 Mi-26 helicopters are currently in service worldwide.
Mi-26 helicopter variants
The Mi-26 has 13 variants, which include Mi-26A, Mi-26M, Mi-26MS, Mi-26NEF-M, Mi-26P, Mi-26PP, Mi-26PK, Mi-26S, Mi-26T, Mi-26TP, Mi-26TS, Mi-26TZ and Mi-27.
The Mi-26A is an advanced version of the Mi-26 and completed its flight test in 1985. It is upgraded with a structured PNK-90 flight navigation system for automated approach and decline.
Another variant, the Mi-26M is an upgraded version of Mi-26. It is incorporated with a flight navigation system, D-127 turboshaft engines, an electronic flight instrumentation system and aerodynamic rotor blades for better performance.