Staff Writer (Updated: 4/25/2016):
The CH-46 utilizes two Lycoming turboshaft engines to drive the powerful main rotor blades. Crew accommodations amount to two or three standard personnel with spacing in the cabin for an additional 15-25 troops and 15 stretcher patients. The Sea Knight, like its Chinook counterpart, can also carry external sling loads if need be.
The CH-46 was designed from the Model 107 which was actually evaluated by the US Army through three YCH-1A designated prototypes. Though the Army elected to take the larger C-47, which would become the Chinook, the US Marine Corps accepted their CH-46's as the Sea Knight in 1961 to replace their aging UH-34 series. By 1964, deliveries were in full swing and the CH-46 entered service. Along with USMC use, the US Navy also procured several Sea Knights for sea-borne ship replenishment duty.
The CH-47 saw several variants derived from initial models and service experience, each differing in avionics upgrades, subtle redesigns and powerplant changes. Canada accepted the CH-46 as the "Voyageur" and the "Labrador" to fill roles in search and rescue and transport respectively. Additionally, the CH-46 has appeared with Japanese forces as the KV 107 model series in various roles and with Sweden as the HKP-4 series.