Bell Boeing Quad TiltRotor
The Bell Boeing Quad TiltRotor (QTR) is a proposed four-rotor
A quadrotor, also called a quadrotor helicopter or quadrocopter, is an aircraft that is lifted and propelled by four rotors. Quadrotors are classified as rotorcraft, as opposed to fixed-wing aircraft, because their lift is derived from four rotors...

 derivative of the V-22 Osprey
V-22 Osprey
The Bell Boeing V-22 Osprey is an American multi-mission, military, tiltrotor aircraft with both a vertical takeoff and landing , and short takeoff and landing capability...

A tiltrotor is an aircraft which uses a pair or more of powered rotors mounted on rotating shafts or nacelles at the end of a fixed wing for lift and propulsion, and combines the vertical lift capability of a helicopter with the speed and range of a conventional fixed-wing aircraft...

 developed jointly by Bell Helicopter and Boeing. The concept is a contender in the U.S. Army's
United States Army
The United States Army is the main branch of the United States Armed Forces responsible for land-based military operations. It is the largest and oldest established branch of the U.S. military, and is one of seven U.S. uniformed services...

 Joint Heavy Lift program. It would have a cargo capacity roughly equivalent to the C-130 Hercules
C-130 Hercules
The Lockheed C-130 Hercules is a four-engine turboprop military transport aircraft designed and built originally by Lockheed, now Lockheed Martin. Capable of using unprepared runways for takeoffs and landings, the C-130 was originally designed as a troop, medical evacuation, and cargo transport...

, cruise at 250 knots, and land at unimproved sites vertically like a helicopter.


Bell developed its model D-322 as a quad tiltrotor concept in 1979. The Bell Boeing team disclosed in 1999 a Quad TiltRotor design the companies had been investigating for the previous two years. The design was for a C-130-size V/STOL transport for the US Army's Future Transport Rotorcraft program and would have 50% commonality with the V-22. This design was to have a maximum takeoff weight of 100000 lb (45,359.2 kg) with a payload of up to 25000 lb (11,339.8 kg) in a hover. The design was downsized to be more V-22-based and to have a payload of 18000 to 20000 lb (8,164.7 to 9,071.8 kg). This version was referred to as "V-44". Bell received contracts to study related technologies in 2000. Development was not pursued by the US Department of Defense.

During 2000-06, studies of the aerodynamics and performance of a Quad Tilt Rotor were conducted at the University of Maryland, College Park
University of Maryland, College Park
The University of Maryland, College Park is a top-ranked public research university located in the city of College Park in Prince George's County, Maryland, just outside Washington, D.C...

. This effort was initially funded by NASA/AFDD and subsequently by Bell. An experimental investigation in helicopter mode with ground effect found that it was possible to reduce the download on the aircraft from 10% of the total thrust to an upload of 10% of the thrust. A parallel Computational Fluid Dynamics (CFD) study confirmed these findings.

Joint Heavy Lift studies

In September 2005 Bell and Boeing received a cost-sharing contract worth US$
United States dollar
The United States dollar , also referred to as the American dollar, is the official currency of the United States of America. It is divided into 100 smaller units called cents or pennies....

3.45 million from the U.S. Army's Aviation Applied Technology Directorate for an 18-month conceptual design and analysis study lasting through March 2007, in conjunction with the Joint Heavy Lift program. The contract was awarded to Bell Helicopter, which is teaming with Boeing's Phantom Works
Boeing Phantom Works
The Phantom Works division is the advanced prototyping arm of the Defense and Security side of The Boeing Company. Its primary focus is developing advanced military products and technologies, many of them highly classified, and has produced breakthroughs in defense, space and security.Founded by...

. The QTR study is one of five designs; another of the five is also a Boeing program, an advanced version of the CH-47 Chinook
CH-47 Chinook
The Boeing CH-47 Chinook is an American twin-engine, tandem rotor heavy-lift helicopter. Its top speed of 170 knots is faster than contemporary utility and attack helicopters of the 1960s...


During the initial baseline design study, Bell's engineers are designing the wing, engine and rotor, while the Boeing team is designing the fuselage and internal systems. A similar arrangement is used on the V-22
V-22 Osprey
The Bell Boeing V-22 Osprey is an American multi-mission, military, tiltrotor aircraft with both a vertical takeoff and landing , and short takeoff and landing capability...


A one-fifth-scale wind tunnel
Wind tunnel
A wind tunnel is a research tool used in aerodynamic research to study the effects of air moving past solid objects.-Theory of operation:Wind tunnels were first proposed as a means of studying vehicles in free flight...

 model has undergone testing in the Transonic Dynamics Tunnel (a unique transonic wind tunnel) at NASA
The National Aeronautics and Space Administration is the agency of the United States government that is responsible for the nation's civilian space program and for aeronautics and aerospace research...

's Langley Research Center
Langley Research Center
Langley Research Center is the oldest of NASA's field centers, located in Hampton, Virginia, United States. It directly borders Poquoson, Virginia and Langley Air Force Base...

 during summer 2006. The "semi-span" model (representing the right half of the aircraft) measured 213 inches in length, and had powered 91-inch rotors, operational nacelles, "dynamically representative" wings.

The primary test objective was to study the aeroelastic
Aeroelasticity is the science which studies the interactions among inertial, elastic, and aerodynamic forces. It was defined by Arthur Collar in 1947 as "the study of the mutual interaction that takes place within the triangle of the inertial, elastic, and aerodynamic forces acting on structural...

 effects on the aft wing of the forward wing's rotors and establish a baseline aircraft configuration. Alan Ewing, Bell's QTR program manager, reported that "Testing showed those loads from that vortex on the rear rotor [are the] same as the loads we see on the front [rotors]," and "Aeroelastic stability of the wing looks exactly the same as the conventional tiltrotor". These tests used a model with a three-bladed rotor, future tests will explore the effects of using a four-bladed system.

Besides the research performed jointly under the contract, Bell has funded additional research and wind tunnel testing in cooperation with NASA and the Army. After submission of initial concept study reports, testing of full-scale components and possibly a sub-scale vehicle test program was expected to begin. Pending approval, first flight of a full-scale prototype aircraft was slated for 2012.

The study was completed in May 2007, with the Quad TiltRotor selected for further development. However, additional armor on Future Combat Systems
Future Combat Systems
Future Combat Systems was the United States Army's principal modernization program from 2003 to early 2009. Formally launched in 2003, FCS was envisioned to create new brigades equipped with new manned and unmanned vehicles linked by an unprecedented fast and flexible battlefield network...

 manned ground vehicles
Future Combat Systems manned ground vehicles
The Future Combat Systems Manned Ground Vehicles was a family of lighter and more transportable ground vehicles developed by BAE Systems Inc and General Dynamics as part of the United States Army's Future Combat Systems program. The ground vehicles were to be based on a common tracked vehicle...

 caused their weight to increase from 20 tons to 27 tons, requiring a larger aircraft. In mid-2008, the U.S. Army continued the Joint Heavy Lift (JHL) studies with new contracts to the Bell-Boeing and Karem Aircraft/Lockheed Martin teams. The teams were to modify their designs to reach new JHL specifications. JHL became part of the new US Air Force/Army Joint Future Theater Lift (JFTL) program in 2008. In mid-2010, the US DoD was formulating a vertical lift aircraft plan with JFTL as a part. The DoD also requested information from the aerospace industry on technologies for JFTL in October 2010.


The conceptual design is for a large tandem wing
Tandem wing
thumb|right|QAC Quickie Q2A tandem wing aircraft usually involves two full-sized wings, both of which are full airfoils. Sometimes an aircraft of this configuration can look like a variation on the biplane, but is in fact very different. The forward wing is often technically a canard, fitted with...

 aircraft with V-22 type engines and 50-foot rotors at each of the four wing tips. The C-130-size fuselage would have a 747-inch-long cargo bay with a rear loading ramp that could carry 110 paratroopers or 150 standard-seating passengers. In cargo configuration, it would accommodate eight 463L pallets.

In addition to the baseline configuration, the Bell-Boeing team is including eight possible variants, or "excursion designs", including a sea-based variant. The design team is planning on payloads ranging from 16 to 26 tons and a range of 420 to 1000 nmi. The baseline version includes a fully retractable refueling probe and an interconnecting drive system for power redundancy.

One of the design excursions explored by the team, dubbed the "Big Boy", would have 55-foot rotors and an 815-inch-long cargo bay, making it able to carry one additional 463L pallet, and accommodate a Stryker
The IAV Stryker is a family of eight-wheeled, 4-wheel-drive , armored fighting vehicles derived from the Canadian LAV III and produced by General Dynamics Land Systems, in use by the United States Army. The vehicle is named for two American servicemen who posthumously received the Medal of Honor:...

 armored combat vehicle.

See also

External links

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