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The Bell Boeing Quad TiltRotor (QTR) is a proposed four-rotor derivative of the Bell Boeing V-22 Osprey developed jointly by Bell Helicopter and Boeing.The concept is a contender in the U.S. Army's Joint Heavy Lift program (a part of Future Vertical Lift program).
Around 2005 [13] –2010, [14] Bell and Boeing teamed up again to perform a conceptual study of a larger Quad TiltRotor (QTR) for the US Army's Joint Heavy Lift (JHL) program. The QTR is a larger, four rotor version of the V-22 with two tandem wings sets of fixed wings and four tilting rotors.
Engine balance refers to how the inertial forces produced by moving parts in an internal combustion engine or steam engine are neutralised with counterweights and balance shafts, to prevent unpleasant and potentially damaging vibration. The strongest inertial forces occur at crankshaft speed (first-order forces) and balance is mandatory, while ...
Another advantage of tiltwing aircraft is the ease of transition between VTOL and horizontal flight modes. A tiltrotor must first fly forwards like a helicopter, building airspeed until wing lift is sufficient to allow the nacelles to begin tilting down. As a note, the MV-22 Osprey's stall speed in airplane mode is 110 knots (204 km/h; 127 mph).
Flapping results in flapback, a tilting backwards of the rotor disc. Dissymmetry of lift is also countered by cyclic feathering, i.e. a change to the angle of incidence of the rotor blades as they rotate around the hub. There is a limit to which angle of attack changes can counter dissymmetry of lift.
An USAF CV-22 in flight The Bell X-22 with four tilting ducted fans. The powered rotors of a tiltrotor (sometimes called proprotor) are mounted on rotating shafts or nacelles at the end of a fixed wing, and used for both lift and propulsion. For vertical flight, the rotors are angled to provide thrust upwards, lifting the way a helicopter rotor ...
The Buckau, the first vehicle to be propelled by a Flettner rotor. A Flettner rotor is a smooth cylinder with disc end plates which is spun along its long axis and, as air passes at right angles across it, the Magnus effect causes an aerodynamic force to be generated in the direction perpendicular to both the long axis and the direction of airflow. [1]
Longitudinal dihedral can also mean the angle between the zero-lift axis of the wing and the zero-lift axis of the horizontal tail instead of between the root chords of the two surfaces. This is the more meaningful usage because the directions of zero-lift are pertinent to trim and stability while the directions of the root chords are not.