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Air Power
Boeing CH-46 Sea Knight

The Boeing CH-46 Sea Knight helicopter has served the US Navy and Marine Corps faithfully since the early 1960's. This venerable aircraft's primary mission areas in the Navy (as the H-46D) include Combat Logistics Support and Vertical Replenishment (VERTREP), Search and Rescue, and Special Operations. As a Marine Corps platform, the H-46E is used primarily during cargo and troop transport. The unique tandem-rotor design of the Sea Knight permits increased agility and superior handling qualities in strong relative winds from all directions, allowing, in particular, rapid direction changes during low airspeed maneuvering. This capability has resulted in the safe, efficient and graceful transfer of many millions of tons of cargo and many thousands of passengers over the years.

Readily identified among current Navy and Marine Corps helicopters are the H-46 series Sea Knights, with their tandem rotor configuration setting them apart from the single rotor design of other Navy/Marine helos. Tandem rotors have been a feature of all production helos built by Boeing/Vertol, and its original predecessor company, Piasecki.

The H-46 “Sea Knight” helicopter is one of the largest helicopters in the US Navy inventory. The “Sea Knight” is a twin-turbine powered, dual-piloted, tandem rotor helicopter designed by the Boeing Company Vertol Division. The aircraft is 16 feet 8 inches tall. There are six rotor blades on the aircraft, each measuring 25 feet 6 inches. With blades spread, the aircraft is 84 feet 4 inches long. The average weight of the H-46 is 18,000 pounds, with a maximum lift capability of 6,000 pounds. It can carry 25 combat-loaded troops, or can be outfitted to carry medical evacuation litters in case of disaster. It has the fuel endurance to stay airborne for approximately two hours, or up to three hours with an extra internal tank.

The helicopter has the ability to land and taxi in the water in case of emergency, and is able to stay afloat for up to two hours in two-foot seas. Because of its tandem rotor design, the “Sea Knight” is an extremely versatile aircraft. It is able to excel in various flight maneuvers, such as rearward and sideward flight, while other helicopters are extremely limited. This makes the helicopter ideal for its primary Navy mission of vertical replenishment.

The CH-46 Sea Knight was first procured in 1964 to meet the medium-lift requirements of the Marine Corps in Vietnam with a program buy of 600 aircraft. The aircraft has served the Marine Corps in all combat and peacetime environments. However, normal airframe operational and attrition rates have taken the assets to the point where a medium lift replacement is required. The safety and capability upgrades are interim measures to allow continued safe and effective operation of the Sea Knight fleet until a suitable replacement is fielded.

Production continued in subsequent years, along with modifications to improve some of the H-46's characteristics. With service in Southeast Asia came installation of guns and armor. Increased power requirements were met by installation of higher powered T-58-GE-10s in the CH/UH-46D models, which also featured new cambered (droop snoot) rotor blades. The final CH-46E, with further increased power, was preceded by the last production version, the CH-46F, before production was completed with delivery of the 524th H-46 in February 1971.

The early A models now serve as search and rescue HH-46As. CH-46s equip Marine Reserve squadrons, and conversion of earlier aircraft to the new CH-46E version was completed with fiberglass blades slated added to its other improvements.

The mission of the CH-46E Sea Knight helicopter in a Marine Medium Helicopter (HMM) squadron is to provide all-weather, day/night, night vision goggle (NVG) assault transport of combat troops, supplies, and equipment during amphibious and subsequent operations ashore. Troop assault is the primary function and the movement of supplies and equipment is secondary. Additional tasks are: combat and assault support for evacuation operations and other maritime special operations; over-water search and rescue augmentation; support for mobile forward refueling and rearming points; aeromedical evacuation of casualties from the field to suitable medical facilities.

The CH-60 Fleet Combat Support Helicopter will complement and eventually replace the Navy's aging fleet of H-46 helicopters. As a result of the advanced airframe life of the H-46 fleet, the Navy's logistics helicopter force is experiencing a near-term inventory shortfall.

The Navy Air Systems Command ordered the grounding of all CH-46 helicopters on 18 August 2002 as a precaution after discovery of a crack in a rotor component of a Sea Knight at the Cherry Point Marine Corps Air Station in North Carolina. A similar problem was found a few days later in a CH-46 deployed aboard the amphibious assault ship Belleau Wood in the Persian Gulf area. Inspection of all 291 CH-46 Sea Knight helicopters in the Navy and Marine Corps found only one with a flaw of the kind that triggered the temporary grounding of the fleet, and the full fleet was returned to service.

Primary function: Medium lift assault helicopter
Manufacturer: Boeing Vertol Company
Power plant: (2) GE-T58-16 engines
Thrust: Burst: 1870 shaft horsepower (SHP) - Continuous: 1770 SHP
Length: Rotors unfolded:84 feet, 4 inches (25.69 meters)- Rotors folded: 45 feet, 7.5 inches (13.89 meters)
Width: Rotors unfolded: 51 feet (15.54 meters)- Rotors folded: 14 feet, 9 inches (4.49 meters)
Height: 16 feet, 8 inches (5.08 meters)
Maximum takeoff weight: 24,300 pounds (11,032 kilograms)
Range: 132 nautical miles (151.8 miles) for an assault mission
Speed: 145 knots (166.75 miles per hour)
Ceiling: 10,000 feet (+)
Crew: Normal: 4 - pilot, copilot, crew chief, and 1st mechanic
Combat: 5 - pilot, copilot, crew chief, and 2 aerial gunners
Payload: Combat: maximum of 14 troops with aerial gunners
Medical evacuation: 15 litters and 2 attendants Cargo: maximum of 4,000 pound (2270 kilograms) external load