Boeing Vertol CH-47 Chinook
The CH-47 Chinook was developed by Piasecki/Vertol almost immediately following the development of the CH-46 Sea Knight in 1957; both craft were based off the tandem rotor design of the H-21 “Flying Banana,” but emphasized improvement on overall payload capacity, and replaced the H-21’s piston-powered engines with the newer turboshaft design. While Vertol initially planned on only developing a single tandem rotor aircraft, the US Army’s search for a heavier cargo helicopter incentivized the development of the Chinook, which was essentially an upscaled variant of the original Sea Knight; the financial strain caused by the simultaneous development of two new helicopters for the US military brought Vertol to the point of ruin, prompting a buyout by Boeing in 1961. However, Boeing saw potential in both craft, and continued development on the project. The Chinook was delivered to the US Army in 1962, quickly becoming popular as the Army’s premier heavylift cargo craft, with 354 delivered and 22 units simultaneously serving in Vietnam. The Chinook could carry 33 fully-equipped troops, or 6,000 pounds of internal cargo (as much as 13,000 pounds externally).
 AirVectors. “The Boeing Chinook,” accessed October 18, 2013.
 AirVectors. “The Boeing Sea Knight,” accessed December 12, 2013.