How does F-22 Thrust Vectoring work?

[dunkellic]

Originally Posted by Viper5

That would be 1D and 2D vectoring...

funny thing, while that would be much more logical it is actually 2D and 3D thrust vectoring and as creepingshadow said, 2D means up and down and 3D up and down plus left and right vectoring

Thrust Vectoring Control became a big issue in the 1980's and early 1990's with the majority of aerospace companies pushing ahead with related programs. There are two basic types of TVC, 2D and 3D. Two dimensional vectoring (2DTVC) works by directing the exhaust up or down (pitch vectoring), the F-22 Raptor features such a system. While three dimensional vectoring (3DTVC) adds the ability to direct the thrust left to right (yaw vectoring).

...

my source is: Eurofighter Technology and Performance : Propulsion
that is also the source of following excerpt, concerning tv and the typhoon

Thrust Vectoring ControlThrust Vectoring

Thrust Vectoring Control became a big issue in the 1980's and early 1990's with the majority of aerospace companies pushing ahead with related programs. There are two basic types of TVC, 2D and 3D. Two dimensional vectoring (2DTVC) works by directing the exhaust up or down (pitch vectoring), the F-22 Raptor features such a system. While three dimensional vectoring (3DTVC) adds the ability to direct the thrust left to right (yaw vectoring).

The are several real benefits to employing thrust vectoring, for example; decreased take-off and landing distances, higher achievable angles of attack, improved control at low speeds/altitudes, reduction in size and number of control surfaces and reduced supersonic drag (by using the vectoring equipment to adjust trim rather than the control surfaces). There are however questions over just how useful TVC will be in future air battles with the increasing move towards beyond visual range engagements.







As well as the potential for increasing the EJ200's thrust there are also plans to incorporate a Thrust Vectoring Control, or TVC nozzle.

The EJ200's TVC nozzle is a joint project lead by Spain's ITP and involving Germany's MTU. Preliminary design of the system began in mid-1995 at ITP, the proceeding years involved work by both ITP and MTU to deliver a fully functional EJ200 integrated system. The outcome of this research led to the first 3DTVC equipped EJ200 undergoing rig trials in July 1998. The nozzle requires relatively few modifications or additions to be made to the EJ200; a new hydraulic pump, reheat liner attachment upgrades, casing reinforcement, new actuators and associated feed equipment. More importantly the equipment fits within the engines current installation envelope and therefore no changes will need to be made to the Typhoon to accommodate the system.

There are essentially three types of vectoring nozzle; ones in which the entire post-turbine section is moved, those which feature external nozzle attachments for directing thrust (e.g. the X-31 paddles) or ones in which thrust is vectored within the divergent section. The ITP system uses the later design requiring no external equipment (which adds weight and offers relatively poor efficiency) and reducing distortion on the major engine structures (a problem with using the first method).
CAD image of nozzle during vectoring © ITP R&D



The new Thrust Vectoring Nozzle, TVN is a convergent/divergent type containing three concentric rings linked via four pins forming a unified Cardan joint. Each of these rings serves a purpose, the inner ring is connected to the nozzle throat area with the secondary ring forming a cross-joint connection with the pivoting outer ring. This outer ring is in turn connected to the divergent section (green on the CAD diagram) via several struts or reaction bars (black on the CAD diagram to the left). The outer ring is controlled by either three or four hydraulically powered actuators situated at the North, South, East, West, South West and South East positions. By minimising the number of required actuators (either three or four) ITP claim there is little additional weight, reduced actuator power demands and increased reliability over previous systems. Additionally the nozzle utilises a partial balance-beam effect to minimise the actuator load requirement. This effect uses the exhaust gases themselves to close the nozzle throat area, according to ITP this gives a 15% reduction in actuator loads in certain circumstances.

Vectoring configurations © ITP R&D



The baseline vectoring configuration uses three actuators (North, South East and South West). By moving each actuator either in or out the outer ring (red) can be tilted in any direction (see CAD diagram to right, top picture) thus offering both pitch and yaw control. Any net directional movement in the outer ring is then translated via the struts into a larger movement of the divergent section, vectoring the thrust. As well as vectoring control (via movement of each actuator) it is possible to alter the throat area directly by moving all three actuators outward or inward in parallel. In both cases the outer pivot and the inner (green) throat area ring are fixed in the axial direction which reduces the required number of actuators.

Beyond the baseline case the TVN includes a pro-baseline configuration offering the ability to alter the divergent section exit area as well as vectoring thrust and altering the throat area. To achieve this the outer ring is split into top and bottom halves and four actuators (in the N, E, S and W positions) are utilised (see CAD diagram to right, bottom picture). By moving each actuator in a unified/combined manner the thrust can be vectored and the throat area altered. However by moving just the N and S actuators the split ring hinge can be opened and closed. In turn this moves the upper and lower strut series either in or out opening or closing the exit area. In a traditional Con-Di nozzle the exit area is directly related to the throat area. The problem with this approach is that it is extremely difficult to optimise the nozzle shape to different flight profiles, e.g. subsonic cruise, supersonic dash. By allowing dynamic control of the exit area the nozzle shape can be altered on the fly. According to ITP this allows for significant improvements in achievable thrust in all flight profiles.

The three ring system is not the only unique feature of the nozzle. In previous convergent/divergent systems the reaction bars or struts have been connected to the divergent section at a single point. This limits their deflection range thus imposing limits on achievable thrust vectoring (typically to no more than 20°). The ITP TVN however uses a dual point hinged connection allowing a far greater range of movement to be achieved (according to ITP, studies indicate 30°+ can be achieved). By careful placement of the struts, problems with the nozzle petals overlapping or colliding are also removed.Click either image for alternative versions



Rig trials of 3DTVC equipped EJ200 © ITP R&D



Since rig trials commenced in 1998 the TVC equipped EJ200-01A has run for 80 hours (February 2000) of which 15 hours were at full reheat (including sustained five minute burns) during 85 runs. These trials have included over 6700 vectoring movements at the most severe throttle setting and 600 throttling cycles under the most demanding vectoring conditions. These trials demonstrated full, 360° deflection angles of 23.5° with a slew rate (the rate at which the nozzle can be directed) of 110°/s and a side force generation of some 20kN (equal to approximately to one third of the total EJ200 baseline output). These vectoring trials have included both programmed ramp movements and active joystick control. The studies have also verified the MTU developed DECU (Digital Engine Control Unit) software and FCS connections.

During the summer of 2000 a round of altitude trials commenced at the University of Stuttgart, Germany. These are focused on determining the effects of temperature and pressure variation on the nozzle materials, shape and performance. Additionally ITP are continuing work on further reducing the weight of the system.

In November 2000 ITP announced that an agreement had been reached with Germany and the U.S. to utilise the X-31 VECTOR test aircraft for flight trials of the nozzle. This will see a modified EJ200/TVN combination fitted to the X-31. The modification work required will involve all members of the EuroJet consortium. Additional input is likely from EADS and Boeing as well as NETMA in providing the required EJ200's and equipping the X-31. The Spanish government has agreed to pay for flight certification of the system and provide test pilots. The first flight trials are expected in late 2002 to early 2003. In addition Eurofighter and EuroJet have expressed a desire to commence flight trials of DA1 equipped with the nozzle sometime from 2003. How this fits in with the X-31 test phase is currently unclear.

ITP have suggested that a Eurofighter fitted with the nozzle will benefit in a number of areas including; reduced after body drag (through tighter nozzle shape control), an estimated 7% improvement in installed thrust for the supersonic cruise regime (M1.2 non-reheat at 35000ft) and a 2% improvement in maximum take-off thrust.

At this stage there are no definite plans to fit the nozzle to any production Eurofighter. However Eurofighter, EuroJet and a number of consortium nations and other companies have indicated a desire to include the nozzle (if possible) in Tranche-3 aircraft (due from 2010). This would fit with the stated desire of the four consortium nations to incorporate new technologies in sucessive Eurofighter production runs. The current Eurofighter struture has already been strengthened in anticipation of increased loads created by TVC as well as higher output EJ2x0 series powerplants.