Advanced Tandem Rotor Helicopter ( ATRH )

On 19 September 2005 the US Army, in cooperation with its Joint Service and NASA partners, announced the award of five agreements/contracts for the Concept Design and Analysis (CDA) of a Vertical Takeoff and Landing (VTOL) Joint Heavy Lift, (JHL) rotorcraft.

The baseline design specification is to maneuver an FCS/Stryker/LAV Vehicle over a 250 nautical mile (nm) radius, under 4000 foot density altitude and 950 Fahrenheit (4k95) conditions, from/to land or sea bases and operating areas. Eight specific excursions to these conditions will also be investigated that include lighter and heavier cargo (16 - 26 tons), shorter and longer mission radii (210 - 500 nm), more extreme environmental conditions (6k95), and full compatibility with a future ship. These design variations populate the desired trade space in the joint requirements process.

Boeing was chosen to evaluate the Advanced Tandem Rotor Helicopter ( ATRH ), with a maximum speed of 165 knots. This represented a revival of the Aerial Cargo Transport [ACT] proposed a decade earlier. The Boeing Advanced Tandem Rotor Helicopter exploits the system maturity of the CH-47 Chinook, the extraordinary VTOL cargo-handling versatility and the unsurpassed maritime suitability of the tandem rotor platform, which uses two equally-sized rotors that spin in opposite directions for lift. The ATRH will maximize the benefits of advanced technologies and lean approaches, and will capitalize on emerging technologies that improve weapons system effectiveness and operational costs.

The tandem rotor design is a Boeing hallmark. By 1990, Boeing Vertol (formerly Piasecki) had built more than 2.500 aircraft in this configuration.

Several of the first helicopter pioneers had constructed tandem-rotor designs, but the results had been ambiguous, because the power and control limitations did not make their load-carrying advantage apparent.In single-rotor designs because their center-of-gravity had to align closely with the axis of the rotor mast to ensure effective control. A twin-rotor helicopter could solve these problems, but early examples suffered from control problems inherent to its lateral-rotor configuration.

A young, enterprising engineer named Frank Piasecki received a Navy contract for construction of a new helicopter on January 1, 1944. The XHRP-X first took to the air on March 7, 1945. Ultimately, the HRP-1s played their greatest role with Marine helicopter squadron HMX-1, which used the type extensively to develop vertical assault tactics. Marine Corps tacticians realized that their amphibious invasion forces were vulnerable to atomic weapons, which prompted an intense search for alternative methods of delivering combat troops to the battle zone. The helicopter quickly emerged as the best option and the HRP-1 was the first model with sufficient troop-carrying capacity to make vertical assault operations practical.

Boeing developed a modernized version of the CH-46 "Phrog" that first flew on the morning of June 10, 1987, opening a new chapter in tandem-rotor technology. That aircraft was the BV-360, or the "Son of Phrog." The 360 was a 1980's technology aircraft built largely of composite materials. It was the largest composite helicopter in the world. It resembled the "Phrog" with a number of advanced systems and incorporates a number of proven cost-efficient CH-47D systems. All of these systems have contributed to the 360's increased airspeed, decreased weight, and improved reliability.

The 360 could fly at a comfortable 200 knots cruise airspeed with a top speed of 214 knots. The 360 has a high-speed articulating rotor system made of composite material that incorporates a new transonic airfoil and a planform design that can provide, according to Boeing, a 23 percent increase in cruise efficiency and permit cruise speeds in excess of 200 knots.

The 360 was designed to operate at gross weights up to 48,000 pounds, with an initial design gross weight of 30,500 pounds. The engines and transmission systems were all proven, cost- efficient CH-47D components. The aircraft incorporated a state-of-the-art glass cockpit comparable to the Osprey. The 360 utilized the CH-47D load-stabilizing triple-cargo-hook system designed to carry up to 18,000 pounds on the forward and aft hooks and the center hook to handle up to 30,000 pounds. The 360 could carry the USMC 198 howitzer. The 360 could also carry 24 fully combat troops or rig for 15 litters and fly a 200nm flight.

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