Boeing Vertol CH-46 Sea Knight

Sea Knight hospital ship

A Sea Knight lands on the US Navy Hospital Ship Sanctuary to unload casualties, 1969.

Produced alongside the CH-47 Chinook, the CH-46 Sea Knight was developed by Vertol beginning 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. The Sea Knight was initially designed for the US Army’s large-scale helicopter competition, but lacked the bulk and power required to meet the Army’s standards. This in mind, the Sea Knight was rejected in favor of the larger CH-47 Chinook, Boeing Vertol’s up-scaled innovation on the initial Sea Knight concept. This may have been the operational end for the Sea Knight, but the USMC, in need of smaller, more storable craft than the army (as marines would often deploy from aircraft carriers, which had limited deck space) took notice of the agile transport, and officially adopted the Sea Knight in 1964. Also known as the “frog” for its rear sponsons (which resemble the crouched legs of an amphibian), the Sea Knight saw extensive use with the Navy and the Marine Corps during the Vietnam War, and was equipped to carry 17 marines or 4,000 pounds of internal cargo.

[1] AirVectors. “The Boeing Sea Knight,” accessed December 12, 2013.

[2] AirVectors. “The Boeing Chinook,” accessed October 18, 2013.