Ad ogni modo, progetti proposti di recente, come il , vedono una porzione significativa del peso dell'aeromobile sostenuta anche dalla spinta generata dai motori, oltre che da quella fluidodinamica.
Il primo esempio di applicazione in questo campo fu ad opera di Enrico Forlanini con il dirigibile Omnia Dir negli anni trenta. Una seconda tipologia di spinta vettoriale arriva invece dagli ugelli a spinta fluida. Questi deviano la direttrice di propulsione espellendo dell'aria compressa attraverso degli scarichi e riuscendo, in questo caso, a portare una variazione di traiettoria fino a toccare i 15 gradi.
Gli scarichi di questa ventola sono deviati da un ugello direzionabile congiuntamente affiancato dalla spinta del motore primario. The resulting acceleration , velocity and displacement of the aircraft are also vector quantities which can be determined by Newton's second law of motion and the rules of vector algebra. There are two component equations for the force on an aircraft.
One equation gives the the net vertical force Fv , and the other gives the net horizontal force Fh. If we denote the thrust by the symbol T , the lift by L , the drag by D , and the weight by W , the usual force equations for an aircraft in level flight are:.
The quantity T - D is called the excess thrust and is related to the aircraft's ability to accelerate. Good fighter aircraft have high excess thrust. The maneuver is not an example of thrust vectoring. If the pilot is skilled enough, he can do the cobra in nearly any type of U. In essence, the pilot abruptly pulls the control yoke full aft while flying around knots—about mph—and thus pitches the nose up dramatically so the airplane is nearly standing on its tail.
Just as abruptly, the pilot pushes the stick forward, dropping the nose back down. Continue or Give a Gift. Daily Planet. Most currently operational vectored thrust aircraft use turbofans with rotating nozzles or vanes to deflect the exhaust stream. This method can successfully deflect thrust through as much as 90 degrees, relative to the aircraft centerline.
However, the engine must be sized for vertical lift, rather than normal flight, which results in a weight penalty. Afterburning or Plenum Chamber Burning, PCB, in the bypass stream is difficult to incorporate and is impractical for take-off and landing thrust vectoring, because the very hot exhaust can damage runway surfaces.
Without afterburning it is hard to reach supersonic flight speeds. Tiltrotor aircraft vector thrust via rotating turboprop engine nacelles. The mechanical complexities of this design are quite troublesome, including twisting flexible internal components and driveshaft power transfer between engines.
Most current tiltrotor designs feature 2 rotors in a side-by-side configuration. If such a craft is flown in a way where it enters a vortex ring state, one of the rotors will always enter slightly before the other, causing the aircraft to perform a drastic and unplanned roll.
Thrust vectoring is also used as a control mechanism for airships. An early application was the British Army airship Delta , which first flew in Navy rigid airships USS Akron and USS Macon that were used as airborne aircraft carriers , and a similar form of thrust vectoring is also particularly valuable today for the control of modern non-rigid airships.
In this use, most of the load is usually supported by buoyancy and vectored thrust is used to control the motion of the aircraft. But, designs have recently been proposed, especially for Project WALRUS , where a significant portion of the weight of the craft is supported by vectored thrust.
The first airship that used a control system based on pressurized air was Enrico Forlanini 's Omnia Dir in s. This will likely be used in many unmanned aerial vehicle UAVs , and 6th generation fighter aircraft.
Thrust-Vectoring flight control TVFC is obtained through deflection of the aircraft jets into the pitch, yaw and roll directions. In the extreme, deflection of the jets in yaw, pitch and roll creates desired forces and moments enabling complete directional control of the aircraft flight path without the implementation of the conventional aerodynamic flight controls CAFC. To implement TVFC a variety of nozzles both mechanical and fluidic may be applied.
This includes, but is certainly not limited to convergent and convergent-divergent nozzles that may be fixed or geometrically variable. Within these aircraft nozzles, the geometry itself may vary from two-dimensional 2-D to axisymmetric or elliptic.
Thus, it is necessary to clarify some basic definitions used in thrust-vectoring nozzle design. Converging-Diverging Nozzle C-D : Generally found on fighter aircraft, the jet stream is taken through a reduction in area to achieve Mach 1 and then expanded through a diverging section to achieve a supersonic speed greater than Mach 1 before issuing forth.
Converging Nozzle: Nozzle used on standard subsonic transport and passenger jet aircraft.
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