August 2016

AugustU.S. Marine Corps/Boeing Vertol CH-46 Sea Knight
HRB-1/CH-46A first flight: August 1962
USMC CH-46E retirement: August 1, 2015

One of the most versatile transport aircraft the Navy and Marines ever employed, and the Corps’ longest-serving helicopter, the 50(+)-year veteran Boeing Vertol CH-46 Sea Knight carried Marines into battle, resupplied soldiers and evacuated the wounded under fire soon after arriving in Vietnam in late 1965. After initial growing pains with the new type, they served with distinction as the Marines’ primary medium-lift assault helicopter in nearly every Marine Corps campaign since, including the Myaguez Rescue (1975), conflicts in Grenada (1983), Beirut and Lebanon (1982-84), Operations Desert Shield/Storm (1991), Bosnia, Haiti (1994-96), Rwanda Evacuations (1994), Somalia Evacuation (1994), wars in Afghanistan and Iraq, and countless numbers of humanitarian assistance, disaster relief and rescue missions worldwide. 

The National Air and Space Museum Steven F. Udvar-Hazy Center hosted a formal retirement ceremony on August 1, 2015 for the CH-46E Sea Knight along with the United States Marine Corps and the National Museum of the Marine Corps. The aircraft has been temporarily loaned to the Smithsonian Air & Space Museum and placed on display. 

However, the H-46’s age (at the time of its retirement, it was the oldest helicopter in service with the US military), empty weight growth, engine reliability and power degradation, supplier base erosion, parts obsolescence, and operational capability limitations have made it long overdue for retirement.  In the medium-lift assault role, the Corps’ CH-46E has been replaced by the more advanced, survivable and more supportable Bell Boeing MV-22B Osprey tiltrotor.

In 1956, Vertol Aircraft Corporation initiated a $1 million company-funded program that began preliminary and detailed engineering design of a new, twin-turbine, tandem-rotor helicopter for commercial and military applications. In May 1957, construction was started on the sole Vertol Model 107 (V-107) prototype which made its first flight less than one year later on April 22, 1958. It utilized Vertol V-44/H-21 rotor and drive system components but was powered by two 850 shp Lycoming T53-L-1 turbines loaned by the US Army.

After receiving proposals and a comparative evaluation between the Vertol 107M (M-for-Marines) and the Sikorsky HR3S-1, the Navy announced its decision in February 1961 by declaring Vertol's design as the winner of the competition to replace the Marine’s piston-engine helicopters then in use.

Rollout of the first aircraft, designated HRB-1 (Helicopter Transport Boeing-1) occurred in April 1962. The first flight of the first prototype in the USMC configuration took place on August 4, 1962 piloted by Boeing Vertol’s Joe Cox and Ron Mecklin. The first forward flight occurred on August 10. Flight testing would continue at Boeing Vertol’s Flight Test Center and at the Navy’s Patuxent River Naval Air Station, Flight Test Center in Maryland.

USMC HRB-1 helicopters would be equipped with a powered rotor blade fold system, USMC avionics, hydraulically-powered rear-loading ramp, and an upgraded dynamic system that included T58-GE-8B turboshafts with 1250 shp each. It would also include a rescue hoist, self-sealing fuel tanks, a strengthened floor and other modifications.

In September 1962, the Marine’s HRB-1 was redesignated CH-46A and named ‘Sea Knight’.

Boeing Vertol delivered the first CH-46A Sea Knight to Marine Medium Helicopter Squadron-265, Marine Corps Air Station (MCAS), New River, North Carolina, on July 10, 1964.

As part of the contract awarded in September 1961, the Navy ordered a cargo/utility variant  that could perform ship-to-ship Vertical Replenishment (or VertRep) resupply missions. The Navy originally ordered ten UH-46As, then converted fifty USMC CH-46As for the search and rescue (SAR) role as HH-46As. Later, these A’s were upgraded to HH-46Ds for the combat supply and rescue missions. 

After 40 years of service, the Navy retired their H-46D Sea Knight helicopters on September 24, 2004.

The last ‘new’ factory-fresh Sea Knight ever built in the U.S. was accepted by the Marines on February 2, 1971.  Subsequently, all remaining CH-46A/D/F-models (approx. 275 aircraft) were upgraded to the CH-46E configuration at Marine Corps depots with improved avionics, hydraulics, dynamic component upgrade kits and fiberglass rotor blades supplied by Boeing and other suppliers. The engines were now improved T58-GE-16 or -16As with 1,870 shp each.

From April 1962 to February 1971, Boeing Vertol produced 624 H-46s for the Navy and Marines. In 1967, H-46 production had reached its peak with 19 aircraft delivered every month. Adding the CH-47 Chinook to that monthly total, the Army, Marines, and Navy were receiving a tandem-rotor transport helicopter every day from the Boeing Vertol Morton and Ridley Township, Pennsylvania factories. 

Note that the really last Marine Corps Sea Knight retirement occurred September 25, 2015 with the final ceremonial flight of VMR-1’s MCAS Cherry Point, North Carolina last three HH-46E SAR aircraft. For years they’ve been known as ‘Pedros’, a call-sign that dates to early SAR operations in 1965.

(photos by USMC, main photo by Boeing; text by Ken Bartie)

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