CH-47A Chinook Vietnam

The Boeing CH-47 Chinook is an American twin-engined, tandem rotor, heavy-lift helicopter developed by American rotorcraft company Vertol and manufactured by Boeing Vertol (later known as Boeing Rotorcraft Systems). The CH-47 is among the heaviest lifting Western helicopters. Its name, Chinook, is from the Native American Chinook people of modern-day Washington state.
The all-weather, medium-lift CH-47A Chinook was powered initially by Lycoming T55-L-5 engines rated at 2,200 horsepower (1,640 kW), but then replaced by the T55-L-7 rated at 2,650 hp (1,980 kW) engines or T55-L-7C engines rated at 2,850 hp (2,130 kW). The CH-47A had a maximum gross weight of 33,000 lb (15,000 kg), allowing for a maximum payload around 10,000 lb (4,500 kg). Initial delivery of the CH-47A Chinook to the U.S. Army was in August 1962. A total of 349 were built.
Chinooks arrived in Vietnam with the 1st Air Cav in 1965
The most spectacular mission in Vietnam for the Chinook was the placing of artillery batteries in perilous mountain positions inaccessible by any other means, and then keeping them resupplied with large quantities of ammunition. The 1st Cavalry Division found that its CH-47s were limited to a 7,000-pound (3,200 kg) payload when operating in the mountains, but could carry an additional 1,000 pounds (450 kg) when operating near the coast. The early Chinook design was limited by its rotor system which did not permit full use of the installed power, and users were anxious for an improved version which would upgrade this system.
The Chinook soon proved to be such an invaluable aircraft for artillery movement and heavy logistics that it was seldom used as an assault troop carrier. Some of the Chinook fleet was used for casualty evacuation, and due to the very heavy demand for the helicopters, they were usually overburdened with wounded. Perhaps the most cost effective use of the Chinook was the recovery of other downed aircraft.
The CH-47s in Vietnam were generally armed with a single 7.62-mm M60 machine gun on a pintle mount on either side of the aircraft for self-defense, with stops fitted to keep the gunners from firing into the rotor blades. Dust filters were also added to improve engine reliability. At its peak employment in Vietnam, 22 Chinook units were in operation. Of the nearly 750 Chinook helicopters in the U.S. and South Vietnam fleets, about 200 were lost in combat or wartime operational accidents.