Editing Thrust vectoring (section)

== Vectoring nozzles ==
[[File:Jet engine F135(STOVL variant)'s thrust vectoring nozzle N.PNG|alt=Drawing of an articulated nozzle in two positions. The first is straight, and the second is bent 90 degrees.|thumb|Jet engine thrust vectoring nozzle]]{{Multiple image
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| image2            = Sukhoi Su-35S 07 RED PAS 2013 07.jpg
| caption2          = A [[Sukhoi Su-35S]] with its thrust vectoring nozzles for [[supermaneuverability]].
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Thrust-vectoring flight control (TVFC) is obtained through deflection of the aircraft jets in some or all of 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). TVFC can also be used to hold stationary flight in areas of the flight envelope where the main aerodynamic surfaces are stalled.<ref name="spain">"Thrust Vectoring Nozzle for Modern Military Aircraft" Daniel Ikaza, ITP, presented at NATO R&T Organization Symposium, Braunschweig, Germany, 8–11 May 2000</ref> TVFC includes control of [[STOVL]] aircraft during the hover and during the transition between hover and forward speeds below 50 knots where aerodynamic surfaces are ineffective.<ref name="aiaa1">"F-35B Integrated Flight Propulsion Control Development" Walker, Wurth, Fuller, AIAA 2013-44243, AIAA Aviation, August 12–14, 2013, Los Angeles, CA 2013 International Powered Lift Conference"</ref>

When vectored thrust control uses a single propelling jet, as with a single-engined aircraft, the ability to produce rolling moments may not be possible. An example is an afterburning supersonic nozzle where nozzle functions are throat area, exit area, pitch vectoring and yaw vectoring. These functions are controlled by four separate actuators.<ref name="spain"/> A simpler variant using only three actuators would not have independent exit area control.<ref name="spain"/>

When TVFC is implemented to complement CAFC, agility and safety of the aircraft are maximized. Increased safety may occur in the event of malfunctioning CAFC as a result of battle damage.<ref name="spain"/>

To implement TVFC a variety of nozzles both mechanical and fluidic may be applied. This includes convergent and convergent-divergent nozzles that may be fixed or geometrically variable. It also includes variable mechanisms within a fixed nozzle, such as rotating cascades<ref>"The X-Planes, Jay Miller, Aerofax Inc. for Orion Books, {{ISBN|0-517-56749-0}}, Chapter 18, The Bell X-14</ref> and rotating exit vanes.<ref>"Propulsion System For A Vertical And Short Takeoff And Landing Aircraft" Bevilaqua and Shumpert, U.S. Patent Number 5,209,428</ref> Within these aircraft nozzles, the geometry itself may vary from two-dimensional (2-D) to axisymmetric or elliptic. The number of nozzles on a given aircraft to achieve TVFC can vary from one on a CTOL aircraft to a minimum of four in the case of STOVL aircraft.<ref name="aiaa1"/>

=== Definitions ===
[[File:3 three thrust-vectoring aircraft.jpg|thumb|Three experimental thrust vectoring aircraft in flight; from left to right, [[F-18 HARV]], [[X-31]], and [[F-16 VISTA|F-16 MATV]]]]
; Axisymmetric:  Nozzles with circular exits.
; Conventional aerodynamic flight control (CAFC): Pitch, yaw-pitch, yaw-pitch-roll or any other combination of aircraft control through aerodynamic deflection using rudders, flaps, elevators and/or ailerons.
; Converging-diverging nozzle (C-D): Generally used on supersonic jet aircraft where nozzle pressure ratio (npr) > 3. The engine exhaust is expanded through a converging section to achieve Mach 1 and then expanded through a diverging section to achieve supersonic speed at the exit plane, or less at low npr.<ref name="aiaa3923">"Nozzle Selection and Design Criteria" Gambell, Terrell, DeFrancesco, AIAA 2004-3923</ref>
; Converging nozzle: Generally used on subsonic and transonic jet aircraft where npr < 3. The engine exhaust is expanded through a converging section to achieve Mach 1 at the exit plane, or less at low npr.<ref name="aiaa3923"/>
; Effective Vectoring Angle: The average angle of deflection of the jet stream centreline at any given moment in time.
; Fixed nozzle:  A thrust-vectoring nozzle of invariant geometry or one of variant geometry maintaining a constant geometric area ratio, during vectoring. This will also be referred to as a civil aircraft nozzle and represents the nozzle thrust vectoring control applicable to passenger, transport, cargo and other subsonic aircraft.
; Fluidic thrust vectoring: The manipulation or control of the exhaust flow with the use of a secondary air source, typically bleed air from the engine compressor or fan.<ref name="fluidic">"Experimental Study of an Axisymmetric Dual Throat Fluidic Thrust Vectoring Nozzle for Supersonic Aircraft application" Flamme, Deere, Mason, Berrier, Johnson, https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20070030933.pdf {{Webarchive|url=https://web.archive.org/web/20170815115330/https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20070030933.pdf |date=2017-08-15 }}</ref>
; Geometric vectoring angle:  Geometric centreline of the nozzle during vectoring. For those nozzles vectored at the geometric throat and beyond, this can differ considerably from the effective vectoring angle.
; Three-bearing swivel duct nozzle (3BSD<ref name="aiaa1"/>): Three angled segments of engine exhaust duct rotate relative to one another about duct centreline to produce nozzle thrust axis pitch and yaw.<ref name="code1">{{cite web|url=http://www.codeonemagazine.com/article.html?item_id=137|title=F-35B Lightning II Three-Bearing Swivel Nozzle - Code One Magazine|website=codeonemagazine.com|access-date=2015-02-01|archive-date=2014-07-19|archive-url=https://web.archive.org/web/20140719223459/http://www.codeonemagazine.com/article.html?item_id=137|url-status=live}}</ref>
; Three-dimensional (3-D): Nozzles with multi-axis or pitch and yaw control.<ref name="spain"/>
; Thrust vectoring (TV):  The deflection of the jet away from the body-axis through the implementation of a flexible nozzle, flaps, paddles, auxiliary fluid mechanics or similar methods.
; Thrust-vectoring flight control (TVFC):  Pitch, yaw-pitch, yaw-pitch-roll, or any other combination of aircraft control through deflection of thrust generally issuing from an air-breathing turbofan engine.
; Two-dimensional (2-D):  Nozzles with square or rectangular exits. In addition to the geometrical shape 2-D can also refer to the degree-of-freedom (DOF) controlled which is single axis, or pitch-only, in which case round nozzles are included.<ref name="spain"/>
; Two-dimensional converging-diverging (2-D C-D):  Square, rectangular, or round supersonic nozzles on fighter aircraft with pitch-only control.
; Variable nozzle:  A thrust-vectoring nozzle of variable geometry maintaining a constant, or allowing a variable, effective nozzle area ratio, during vectoring. This will also be referred to as a military aircraft nozzle as it represents the nozzle thrust vectoring control applicable to fighter and other supersonic aircraft with afterburning. The convergent section may be fully controlled with the divergent section following a pre-determined relationship to the convergent throat area.<ref name="spain"/> Alternatively, the throat area and the exit area may be controlled independently, to allow the divergent section to match the exact flight condition.<ref name="spain"/>

=== Methods of nozzle control ===

; Geometric area ratios: Maintaining a fixed geometric area ratio from the throat to the exit during vectoring. The effective throat is constricted as the vectoring angle increases.
; Effective area ratios: Maintaining a fixed effective area ratio from the throat to the exit during vectoring. The geometric throat is opened as the vectoring angle increases.
; Differential area ratios:  Maximizing nozzle expansion efficiency generally through predicting the optimal effective area as a function of the mass flow rate.

=== Methods of thrust vectoring ===

; Type I: Nozzles whose baseframe mechanically is rotated before the geometrical throat.
; Type II: Nozzles whose baseframe is mechanically rotated at the geometrical throat.
; Type III: Nozzles whose baseframe is not rotated. Rather, the addition of mechanical deflection post-exit vanes or paddles enables jet deflection.
; Type IV: Jet deflection through counter-flowing or co-flowing (by shock-vector control or throat shifting)<ref name="fluidic"/> auxiliary jet streams. Fluid-based jet deflection using secondary fluidic injection.<ref name="fluidic"/>
; ''Additional type'': Nozzles whose upstream exhaust duct consists of wedge-shaped segments which rotate relative to each other about the duct centreline.<ref name="aiaa1"/><ref name="code1"/><ref>"Variable Vectoring Nozzle For Jet Propulsion Engines" Johnson, U.S. Patent 3,260,049</ref>