Boeing Vertol NCH-46A Sea Knight

The Boeing Vertol NCH‑46A Sea Knight is a twin‑engine, tandem‑rotor transport helicopter that entered U.S. Marine Corps service in 1960. Developed by Boeing Vertol, later known as Boeing Rotorcraft Systems, the Sea Knight evolved from the earlier CH‑46A, incorporating a lengthened airframe, upgraded Allison T56‑A-1 turboprop engines, and strengthened transmission to increase payload and range. Its distinctive tandem rotor configuration eliminated the need for a tail rotor, providing exceptional lift capacity—up to 10,000 lb internally or 12 passengers on the side doors—while maintaining a compact footprint for shipboard operations. The NCH‑46A could be launched and recovered from assault‑type landing‑craft, hover‑hoisted from amphibious vessels, and operate in austere environments, making it a versatile workhorse for troop transport, cargo lift, medevac, and electronic‑warfare missions throughout the Vietnam War and later conflicts.

The Sea Knight’s service demonstrated the practical advantages of tandem‑rotor design, influencing future heavy‑lift helicopters such as the CH‑47 Chinook. Its reliability, adaptability, and long‑range capability cemented its place in military aviation history, and the type remained in active duty until its retirement in the early 2000s, leaving a lasting legacy of amphibious air mobility for modern forces.