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Industria de Turbo Propulsores, S.A.
Thrust Vectoring Nozzle for Modern Military Aircraft Daniel Ikaza Industria de Turbo Propulsores S.A. (ITP) Parque Tecnológico, edificio 300 48170 Zamudio, Spain daniel.ikaza@itp.es presented at NATO R&T ORGANIZATION Symposium on ACTIVE CONTROL TECHNOLOGY FOR ENHANCED PERFORMANCE OPERATIONAL CAPABILITIES OF MILITARY AIRCRAFT, LAND VEHICLES AND SEA VEHICLES Braunschweig, Germany 8th-11th May 2000 Thrust Vectoring: advantages and technology Thrust Vectoring is a relatively new technology which has been talked about for some time, and it can provide modern military aircraft with a number of advantages regarding performance (improved manoeuverability, shorter take-off and landing runs, extended flight envelope, etc...) and survivability (control possible in post-stall condition, faster reaction in combat, etc...). Additionally, as a byproduct of Thrust Vectoring, there is also the capacity to independently control the exit area of the nozzle, which allows to have always an “adapted” nozzle to every flight condition and engine power setting. This means an improvement in thrust which in cases can be as high as 7%. Fig. 1.- CFD Model of a TVN
ABSTRACT This paper describes the technical features of the Thrust Vectoring Nozzle (TVN) developed by ITP and its advantages for modern military aircraft. It is presented in conjunction with two other papers by DASA (Thrust Vectoring for Advanced Fighter Aircraft High Angle of Attack Intake Investigations) and MTU-München (Integrated Thrust Vector Jet Engine Control) respectively.
There are several types of Thrust Vectoring Nozzles. For example, there are 2-D (or single-axis; or Pitch-only) Thrust Vectoring Nozzles, and there are 3-D (or multi-axis; or Pitch and Yaw) Thrust Vectoring Nozzles. The ITP Nozzle is a full 3-D Vectoring Nozzle. Also, there are different ways to achieve the deflection of the gas jet: the most efficient one is by mechanically deflecting the divergent section only, hence minimizing the effect on the engine upstream of the throat (sonic) section. The major aerodynamic aspects of the design of a Thrust Vectoring Nozzle include the correct dimensioning of the vectoring envelope, accounting for the difference between “geometrical” and “effective” vectoring; as well as the sealing pattern of the master and slave petals at and around the throat section.
Paper presented at the RTO AVT Symposium on “Active Control Technology for Enhanced Performance Operational Capabilities of Military Aircraft, Land Vehicles and Sea Vehicles”, held in Braunschweig, Germany, 8-11 May 2000, and published in RTO MP-051.
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with the very demanding aircraft requirements in terms of weight, life, safety, etc... The experience acquired during the ground test phase has helped ITP learn a lot about the behaviour of the nozzle, showing areas in which the design has to be modified, providing data for the integration of nozzle and engine controls, etc... The main outcome of the tests has been the confirmation that the concept designed is valid and it works smoothly. A decisive contribution is being done by ITP’s partner company MTU of Munich, Germany, by developing the electronic Control System.
Fig. 2.- TVN ground tests at ITP
ITP Design The ITP concept consists of a patented design featuring the so-called “Three-Ring-System”, which allows all nozzle functions (Throat Area, Exit Area, Pitch Vectoring and Yaw Vectoring) to be performed with a minimum number of actuators, which, in turn, leads to an optimized mass and overall engine efficiency. The nozzle is controlled by four independent hydraulic actuators, each one with its own servovalve and position transducer. The level of redundancy will depend on the exact application. There is also, only at design level, a simplified variant of the nozzle, with three actuators only, which has basically the same functions of the 4-actuator one, except the independent exit area control. This variant would be a little lighter, but it misses the thrust improvement capability.
This programme is making the Thrust Vectoring technology available in Europe for existing military aircraft such as Eurofighter, in which the introduction of Thrust Vectoring could be carried out with a relatively small number of changes to the aircraft and to the engine, and could provide it with an improved performance.
CONTENTS 1.- DEFINITIONS AND ABBREVIATIONS 2.- BACKGROUND 3.- BENEFITS OF THRUST VECTORING AND NOZZLE EXIT AREA CONTROL 4.- TYPES OF THRUST VECTORING 5.- ITP DESIGN: BASELINE AND OPTIONS 6.- ITP THRUST VECTOR PROGRAMME 7.- CONCLUSIONS
The reaction bars of the ITP nozzle present an arrangement which allows for high deflection angles, without the risk of petal overlapping and/or disengagement. The present prototype has demonstrated deflections up to 23º, but studies have been performed of variants of the nozzle with deflection angles of up to 30-35º.
8.- ACKNOWLEDGEMENTS
Finally, the ITP design makes use of a partial “BalanceBeam” effect, which takes advantage of the energy of the gas stream, on one hand to help close the nozzle under high pressures, hence reducing the maximum load required from the actuators; on the other hand to allow self-closing of the nozzle in case of hydraulic loss under low pressure conditions, specially interesting to retain thrust for take-off.
A8
Nozzle throat area
A9
Nozzle exit area
ATF
Altitude Test Facility
CFD
Computational Fluid Dynamics
ITP TVN programme - Past, Present and Future
DECU
Digital Engine Control Unit
ITP has dedicated a research programme on Thrust Vectoring technology which started back in 1991, and which met an important milestone as is the ground testing of a prototype nozzle at the ITP facilities in Ajalvir, near Madrid, in 1998. Altitude testing is scheduled for 2000.
DOF
Degree of freedom
The next major goal will be the realisation of a flight programme, in order to validate the system in flight, and evaluate the capabilities and performance of the system as a means of flight control. The design used for the ground prototype has been a simple one, for short life and limited safety. For the flight standard, a number of changes will be introduced, in order to comply
1. - DEFINITIONS AND ABBREVIATIONS
Con-Di Convergent-Divergent
ESTOL Extremely Short Take-Off and Landing FCS
Flight Control System
R&D
Research and Development
RCS
Radar Cross Section
SFC
Specific Fuel Consumption
SLS
Sea Level Static
TVN
Thrust Vectoring Nozzle
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2.- BACKGROUND The Thrust Vectoring Nozzle developed by ITP was initially designed to fit and be compatible with an EJ200 engine, which powers the European Fighter Aircraft EF2000. This aircraft is developed by the European consortium Eurofighter, constituted by the companies British Aerospace (UK), DASA (Germany), Alenia (Italy) and CASA (Spain). Similarly, the above engine EJ200 is developed by the European consortium Eurojet, constituted by the companies Rolls-Royce (UK), MTU (Germany), Fiat Avio (Italy) and ITP (Spain). The current EJ200 engine is equipped with a variablegeometry Convergent-Divergent (Con-Di) Nozzle, developed by ITP. This nozzle can modify the area to match the engine running point and afterburner setting, but it has no vectoring capability. Through a dedicated R&D programme, ITP have now introduced a new Thrust Vectoring Nozzle which could be applied to EJ200 to significantly enhance the capabilities of EF2000 Aircraft.
Introduction to Military Aircraft Nozzles In a military aircraft engine with reheat (also called afterburner or augmentor), the nozzle presents a convergent section, which has the task to accelerate the gas jet in order to generate thrust, yet with the characteristic that it must be capable of varying the throat area according to the requirement of the engine running point. These are called “variable geometry convergent” nozzles. Some nozzles, additionally, comprise a divergent section downstream of the convergent section, which overexpands the jet between the throat area and the exit area in order to extract yet some extra thrust. These are called “Variable geometry convergent-divergent” (or Con-Di) nozzles. Depending on the level of control upon this divergent section, variable geometry Con-Di nozzles can be of two types: •
•
One-parameter Nozzles: also called 1-DOF nozzles; the Convergent section (hence Throat Area) is fully controlled, and Divergent section (hence Exit Area) follows a pre-defined relationship to the convergent section behaviour (throat area). The current EJ200 nozzle is of this type.
3.- BENEFITS OF THRUST VECTORING AND NOZZLE EXIT AREA CONTROL Although the description of benefits of Thrust Vectoring and nozzle exit area control for modern military aircraft is in fact the subject of a separate paper by DASA, a brief description of some of them is given here for reference. They can be basically grouped in four categories: •
Enhanced performance in conventional flight
•
Post-Stall flight
•
Increased Safety
•
Reduction of aero controls
Enhanced performance in conventional flight The concept of Thrust Vectoring is often associated with spectacular loop-type manoeuvres performed by small aircraft in airshow demonstrations or combat simulations, and the operational use of these capabilities is often regarded with a lot of skepticism, due to the trends of modern air combat. However, there is a lot more to Thrust Vectoring than these funny manoeuvres, and in fact the greatest argument in favour of Thrust Vectoring is not found in combat characteristics but rather in conventional performance, as described in more detail below:
Stationary Flight Trimming The use of the Nozzles as a complementary control surface allows the aircraft to better optimize its angle of attack in stationary level flight for a given flight point and load configuration, hence reducing the drag, which in turn leads to strong benefits in SFC, and therefore range. INCREASED SUSTAINED TURN RATE CASE STUDY:
Conventional Trimming :
Drag
Velocity Vector
Available Weight
Also there are some intermediate solutions such as “floating” and some other “passive” means of exit area control, which are outside the scope of this paper. One solution or the other is chosen according to the particular requirements of each case, in terms of weight, cost, reliability, thrust, priority missions, etc… In the case of Thrust Vectoring Nozzles, they also have the task to direct the jet to generate side thrust to transmit it to the aircraft structure, so that the aircraft can make use of it as a means of flight and manoeuvre control.
Thrust Rear Flaps Trimming
Flaps 6º up Max. Lift: Ref. Max. Load Factor: Ref. Max. Turn Rate: Ref.
Thrust Vectoring Trimming: Lift Drag
Velocity Vector
Two-parameter Nozzles: also called 2-DOF nozzles; the Convergent section (Throat Area) and Divergent section (Exit area) are fully controlled independently. This type can match the Divergent section to the exact flight condition in order to obtain an optimised thrust.
30,000 ft Mach 1.8
Lift
Weight
Available Thrust
Flaps 2º up Nozzles 4º up Lift Coef.: Ref +14% Load Factor: Ref +9% Turn Rate: Ref +9%
Thrust Vectoring Trimming
Fig. 3.- Increased Sustained Turn Rate with TVNs
Stationary and Transient Manoeuvres Similarly to the above case, the nozzles can be used to increase the maximum load factor that is achievable under certain circumstances while maintaining the aircraft trimmed. This applies both for stationary manoeuvres (sustained turn rate) and for transient manoeuvres (rapid deceleration).
Nozzle Exit Area Control As described in the Introduction to military aircraft nozzles, in one-parameter Con-Di nozzles the divergent section (hence A9) follows a pre-defined relationship to the
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convergent section (hence A8). This relationship is optimised for an average of all missions, which normally means low A9/A8 Ratio for dry operations (without reheat) and high A9/A8 Ratio for operations with reheat. In rough terms, this is reasonably optimised for low speed dry operations (cruise, climb, etc...) and for high speed reheat operations (high speed strike, etc...), but is not optimised for low speed reheat operations (take-off) and high speed dry operations (supersonic cruise).
Optimum A9/A8 ratio including afterbody effects
Reheat Supercruise: 7% Thrust increase
Air superiority
Supersonic
ESTOL
Independent A9 control
Fixed Schedule
In the Altitude/Mach-number envelope, Thrust Vectoring permits an extension of the envelope in the low speedmedium height region. In the Altitude/Mach-number/Angleof-attack envelope, Thrust Vectoring permits operation at much higher values of Angle of attack.
A better control of the aircraft is achieved with Thrust Vectoring, especially at low speed conditions, where conventional aerodynamic controls are not effective, and where a good number of combat scenarios are to take place.
EXIT AREA OPTIMIZATION Dry
The use of Thrust Vectoring permits the aircraft to hold stationary flight in an area of the envelope where conventional controls are not sufficient.
Take-off: 2% Thrust increase
Subsonic
Throat Area
Fig. 4.- Optimization of Nozzle Exit Area
The use of an independently controlled divergent section allows A9 to be optimised for any engine running condition at any flight point, and has an improvement especially in those conditions where one-parameter A9/A8 Ratio is not optimized.
The ESTOL concept (Extremely Short Take-Off and Landing) is becoming more and more appealing to military aircraft operators, and it consists of performing the Take-off and Landing manoeuvres with the aircraft stalled. It reduces take-off and landing runs by a large amount. This is only possible with Thrust Vectoring Nozzles, that operate when the aerodynamic controls are no longer useful.
Increased safety This is probably one of the strongest arguments in favour of Thrust Vectoring. The existence of redundant means of aircraft control allows for a better survivability.
For example, for a supersonic cruise case (Mach 1.2, altitude 36,000 ft, engine at Max Dry condition) of EJ200 engine on Eurofighter, the use of independent A9 control could lead to an improvement of up to 7% in installed net thrust relative to the current performance. This is due to the combination of two effects: increase of nozzle internal thrust; and reduction of nozzle external drag. In addition to thrust increase, independent A9 control also permits reduction in SFC for certain flight points.
Rudder
Foreplane
Nozzles
Reduction of take-off and landing runs The rotation of the aircraft for take-off and landing can be accelerated by using Thrust Vectoring. Also, Thrust Vectoring can be used to increase angle of attack, hence lift, while maintaining a trimmed aircraft. The combination of all these effects gives an important reduction in the take-off and landing runs for an aircraft such as Eurofighter.
Global mission performance The combined effect of all the above items across a typical combat mission could add up to some 3% Fuel saving by using Thrust Vectoring.
Post-Stall Flight The most spectacular benefit of Thrust Vectoring, although possibly not the most important, is the fact that it can exert an active control of an aircraft while the main aerodynamic surfaces are stalled, hence not suitable for control, and this opens a whole new domain of flight conditions where flight used to be unthinkable.
Extension of flight envelope
Leading Edge Slats
Flaps
Fig. 5.- Redundant Flight Controls with TVNs In peace time, an aircraft crash by loss of aerodynamic control could be avoided by the use of Thrust Vectoring. In war time, damage to aerodynamic control surfaces can be compensated with Thrust Vectoring.
Next Step: reduction of aero controls Once the Thrust Vectoring system has been sufficiently validated, it will be a primary control for the aircraft. This
Trimmed Aircraft http://www.grc.nasa.gov/WWW/k-12/airplane/trim.html
W· Wing Lift d • distance
w
Center of Gravity (cg)
w
T· Tail Lift d t· distance
T
For trimmed flight, no rotation about cg.
Equation:
(W x~) + (T x d tl = 0
(Lift of Wing x distance from cg) + (Lift of Tail x distance from cd) - 0
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EXISTING 3-D THRUST VECTORING SYSTEMS
means that it will allow a gradual reduction of existing conventional aerodynamic control surfaces such as horizontal and vertical stabilizers. This will have an impact, and there will be a reduction in: •
Mass
•
Drag
•
Radar Cross Section (RCS)
DEFLECT WHOLE NOZZLE
The extent of these impact could only be properly assessed in the future, and it will probably not be fully exploited until the next generation of combat aircraft, but mass reductions of 15%-20% of the total aircraft are conceivable.
4.- TYPES OF VECTORING NOZZLES From the point of view of the type of actuation means, TVNs can be classified: •
•
Fluidic Actuation: The deflection of the gas flow is achieved by injection of secondary airflows. This type is specially suitable for fixed-area high expansion nozzles, such as those used in rockets and missiles. Mechanical Actuation: The deflection of the gas flow is achieved by mechanical movement of the nozzle, which is powered by hydraulic or pneumatic actuators. This type is specially suitable for variable geometry military aircraft nozzles. *
*
*
From the point of view of the direction of vectoring, TVNs can be classified: •
Single-Axis TVNs: (also called 2-D or Pitch-only) The deflection of the gas flow is achieved in vertical direction only. They replace and/or complement horizontal control surfaces. This type is suitable for all types of variable geometry military aircraft nozzles.
•
Multi-Axis TVNs: (also called 3-D or Pitch and Yaw) The deflection of the gas flow is achieved in any direction. They replace and/or complement horizontal and vertical control surfaces. This type is specially suitable for round nozzles. *
*
Mechanical Actuation, Con-Di Military Nozzles
*
If we focus on 3-D, Con-Di military aircraft TVNs with mechanical actuation, there are several ways to materialise the vectoring:
EXTERNAL FLAPS
DIVERGENT SECTION
Fig. 6.- Existing types of 3-D TVNs Regarding the nozzles of the third type, that is, those that deflect the flow by orienting the divergent section only, they generally need actuation means for: •
Controlling convergent section (hence A8)
•
Controlling divergent section (hence vectoring and A9)
Where other designs make use of two separate actuation systems, the ITP design has a unified actuation system with a minimum total number of actuators.
5.- ITP DESIGN: BASELINE AND OPTIONS One of the biggest problems encountered when designing a Thrust Vectoring Nozzle is how to find a mechanical configuration comprising casing, rings, etc…, which must be compatible with both functions of the nozzle: on one hand, open and close the convergent section to control throat area (optionally open and close the divergent section to control exit area); and on the other hand to direct the nozzle in directions different to axial, to obtain the jet deflection that provides vectored thrust. The other big problem of a Thrust Vectoring Nozzle is how to find an actuation system (hydraulic, pneumatic, electromechanical, mixed, etc..) capable of generating the movements required in the nozzle, to accomplish all the above functions, and reasonably limited under criteria such as weight, size, etc… Many different configurations have been studied at ITP for TVNs, the result being a “baseline” configuration, plus a series of options available for every particular application. The main option is the A9 modulation capability, aimed at optimising the thrust as described above in the chapter “Benefits of Thrust Vectoring and nozzle area control”.
Baseline
•
Deflect whole nozzle. The disadvantages are: a large mass has to be moved; and there is a big impact on performance upstream of the nozzle.
•
External Flaps. The disadvantages are: there is a need for additional mass; and the efficiency of vectoring is very low.
The baseline ITP TVN design is a Convergent-divergent axisymmetric (round) nozzle with multi-axis Thrust Vectoring, mechanically actuated, and where the deflection of the gas flow is achieved by orienting the divergent section only. This way the moving mass is minimized, and the distortion to the engine turbomachinery upstream of the nozzle is negligible.
•
Deflect Divergent section. This is the preferred solution. the size of the nozzle is optimised and the effect on performance is negligible. The ITP Nozzle is of this third type.
It has three degrees of freedom (DOFs), namely: Throat area (A8), Pitch vectoring and Yaw vectoring. Any oblique vectoring is made of a combination of pitch and yaw. Exit area (A9) follows a certain relationship to A8. The actuation system consists of only three independent hydraulic actuators, a fact which is made possible by the basic feature of the design: the “Three-Ring-System”.
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OUTER RING
X
ACTUATORS
Fig. 9.- Nozzle Movement in vectoring Fig. 7.- Three Ring System (3 actuators)
A9 Control option: optimised thrust This system consists of three concentric rings which are linked by pins and form a universal (or “cardan”) joint. The inner ring is linked to the convergent section of the nozzle, the outer ring is linked to the divergent section through the reaction bars, and the intermediate ring acts as the crossbar between the inner and outer rings. The actuators are linked to the outer ring only. The design of the rings and reaction bars is such that a small tilt angle on the ring is amplified to a large deflection angle on the divergent section. The outer ring can be tilted in any direction while the inner ring can only keep a normal orientation to the engine centreline, but they both are forced to keep the same axial position along the engine. This is the key factor that permits a full control of the nozzle by acting on the outer ring only, hence minimizing the total number of actuators. For pure throat area movements, all three actuators move in parallel, hence all three rings follow axially, and A8 is set to the appropriate value. A9 follows a pre-defined relationship to A8 according to the dimensions of the mechanism. For Pitch and/or Yaw vectoring movements, the three actuators move differently, hence defining a tilt plane of the outer ring. The divergent section will deflect in the direction of that plane. Throat area (A8) is not affected unless this movement is combined with a throat area movement.
This option consists basically of the baseline design, except for the fact that the outer ring is split in two halves, forming a “hinged” outer ring. It has four degrees of freedom (DOFs), namely Throat Area (A8), Exit Area (A9), Pitch vectoring and Yaw vectoring. Again, any oblique vectoring is achieved by combination of pitch and yaw. The actuation system consists of four independent actuators, also linked to the outer ring only.
THREE RING SYSTEM
SPLIT RING
Z PITCH, A9
X Y YAW, A8
ACTUATORS
Fig. 10.- Three Ring System (4 actuators)
The same Three Ring principle is used as in the three actuator version, and A8 and vectoring movements are operated in a similar way, yet this time with four instead of three actuators. Additionally, pure A9 control movements are performed by moving top and bottom actuators in parallel while the other two stay static, hence “hinging” the outer ring open or close. The divergent section opens or closes relative to the nominal position, acquiring an “oval” shape. Hence this movement is sometimes referred to as “ovalization”. Of course, A9 movements can be combined with A8 movements and/or vectoring movements. Fig. 8.- Ring Movement in vectoring
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SIMPLIFIED TWO-RING SYSTEM FOR PITCH-ONLY APPLICATIONS PITCH, A9
SPLIT RING
X Y A8
Fig. 13.- "Two-Ring" Pitch-only Nozzle
Fig. 11.- Ring Movement in A9 control
Other features: "hinged" Reaction Bars The design of the reaction bars presents “hinged struts” which allow an optimised smooth movement of petals. Where other designs are limited to about 20º geometric deflection by the disengagement and/or interference between petals, the ITP design allows for growth if required, and studies have been carried out for deflections up to 30º-35º.
SIMPLE REACTION STRUTS Disengagement
VECTORING Interference
Fig. 12.- Nozzle Movement in A9 control Fig. 14a.- Vectoring with simple reaction bars With this configuration there could be an improvement in installed net thrust of up to 7% in certain conditions.
HINGED REACTION STRUTS
In fact, this A9 option could well be considered as the baseline, leaving the non-A9 configuration as a “simplified option”.
VECTORING
Optimized Movement
Third Member of the Family: "Two-Ring" Pitchonly Nozzle This is a simplified version of the ITP Nozzle where the intermediate Ring is deleted, hence reducing some weight and complexity. Outer Ring is split in two as in previous version. It retains the four actuators and it has three DOFs (A8, A9, Pitch Vectoring). It is suitable for application in aircraft with no Post-Stall capability, but where the benefits in conventional flight are important.
Fig. 14b.- Vectoring with hinged reaction bars
Balance-Beam The ITP TVN makes use of a partial balance-beam effect, which consists of taking advantage of the energy of the gas stream to help close the nozzle in high pressure conditions. The closing movement of the nozzle is accompanied by an axial displacement of the throat, so that the volume swept against the gas pressure is modified, in particular more volume is swept in the low pressure region of the nozzle, and less volume in the high pressure region.
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BALANCE BEAM
Changes to EJ200 engine Relative to current EJ200 engine, the introduction of a TVN with "full capability" implies a number of changes:
15% LOWER ACTUATOR LOADS NOZZLE SELF-CLOSING IF HYDRAULIC LOSS DURING TAKE-OFF
Fig. 15.- Balance Beam effect
This has two benefitial effects: •
•
On one hand, in high pressure conditions, the total work performed by the actuation system upon the gas stream is reduced by as much as 15%, which results in smaller actuator dimensions and better engine efficiency. On the other hand, in case of hydraulic loss in low pressure conditions, the nozzle self-closes, which is particularly interesting to retain thrust during take-off.
Actuation and Control System The control system of the nozzle consists of three (baseline design) or four (A9 option) independent actuators, each with its own servovalve and position transducer. The servovalves are powered by the engine hydraulic pump; the electronic control loops and safety logic between servovalves and transducers are performed by the TVN Control Unit, which is built into the engine DECU, which, in turn, is connected to the aircraft Flight Control System (FCS).
TRANSD. 1
INTEGRATED CONTROL SYSTEM
GEARBOX
HYDRAULIC PUMP(S)
TRANSD. 2
•
Nozzle actuators, including Servovalves and transducers
•
Bigger Hydraulic Pump
•
DECU, including Thrust Vectoring functions
•
Casing reinforcement
•
Slight modification to engine mounts
•
Reheat Liner, especially rear attachment
•
Dressings (pipes and harnesses)
However, a reduced-capability TVN version of EJ200 is feasible with very minor changes. In any case, these changes are small if compared with the advantages obtained by introducing Thrust Vectoring.
Advantages of ITP design In summary, the ITP design presents a number of advantages relative to other designs, such as: •
Minimum number of actuators, which leads to lower weight and better overall engine efficiency.
•
Unique reaction bar design for high deflection angles.
•
Partial Balance-Beam effect for lower actuator loads.
•
Nozzle self-closing in case of hydraulic loss during takeoff allows thrust retention
•
It is the only proved example of 3-D TVN for 20,000 lbf thrust engine class.
ITP’s R&D programme on Thrust Vectoring technology started in 1991, and within this programme a good number of general studies have been performed, including:
ACT. 2 TRANSD. 3
SERVOVALVE 3
Nozzle
6.- ITP TVN PROGRAMME
ACT. 1
SERVOVALVE 1 SERVOVALVE 2
•
ACT. 3
SERVOVALVE 4
•
CFD analyses
•
Performance studies
•
Concept design: Baseline plus options
•
Trade-off studies with side loads, number of petals, etc...
•
Patents
•
Mechanical / Kinematic simulations
TRANSD. 4
ACT. 4 OUTER RING
DECU FLIGHT CONTROL SYSTEM
VNCU
FCS BUS
Fig. 16.- TVN Control System
•
Mock-ups
For a twin-engine application such as Eurofighter, a simple hydraulic system and dual electrical system provide enough safety for a primary control.
•
etc...
On the other hand, for a single-engine application, there will probably be a need for duplex hydraulic system and triplex electrical system.
Additionally, a feasibility study has been carried out together with DASA regarding the application of TVN for Eurofighter. The outcome of this study includes the definition of the requirements for the TVN on the
*
*
*
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Eurofighter, and some of the operational benefits expected for Eurofighter.
The test results obtained during the running of the prototype include the following highlights:
An initial study was done in 1994-95, and an update study is being conducted now 1998-2000, this time with MTU also taking part.
•
80 running hours, including 15 with reheat
•
Vectoring in all 360º directions, both dry and reheat
•
23,5º maximum vector angle
•
110º/sec maximum slew rate
•
20 kN maximum lateral force
•
Programmed ramps and Joystick control
•
Thermal case: sustained 20º vector in reheat for 5 minutes
•
Rapid transients Idle-Dry-Reheat while vectoring
•
100+ performance points run
•
Exit area control: 2% thrust improvement
•
Endurance: 6700+ vectoring cycles
•
Endurance: 600+ throttle cycles (with sustained 20º vector)
*
*
*
ITP and MTU have a special co-operation agreement under which MTU has developed the electronic Control System that controls the ITP TVN and actuators.
Prototype Nozzle In 1995 ITP launched what is called a “Technology Demonstration Phase” within the Thrust Vectoring technology R&D programme. This phase includes the design, construction and test of a prototype Thrust Vectoring Nozzle. The design of the prototype started in early 1996 and the first run took place in July 1998, becoming the key milestone in ITP Thrust Vectoring programme so far. This prototype nozzle was aimed at demonstrating as much as possible, even if some things were not necessarily required from the aircraft point of view. Therefore it was designed for high vector loads (30 kN) even if the aircraft requirement will be not higher than 15 kN. Similarly, it incorporated the A9 option to optimise thrust. A deflection of 20º was specified for any engine running condition. The prototype nozzle was constructed for an EJ200 engine vehicle, but maintaining a minimum impact on current EJ200, both regarding the hardware changes, as well as regarding the development programme. In principle, only Sea Level Static (SLS) tests were scheduled, namely the ITP testbed in Ajalvir, near Madrid. However, the nozzle was specified to take the loads of the full flight envelope, and real flight standard materials were used in its construction, so that the mechanism could be validated as far as possible. Most of the components were manufactured in ITP, hence keeping a high degree of flexibility to introduce quick changes in the design. As part of the work associated to the tests of the prototype nozzle, a new detuner (exhaust duct) had to be installed in the ITP testbed (Cell No.2) at Ajalvir. The need for this new detuner was motivated both by the different flow pattern in the cell, and also by the need for cooling. MODIFICATIONS TO TEST CELL: NEW FRONT SECTION OF DETUNER (WATER-COOLED SEGMENTS) MODIFIED DIAMETER AND LENGTH
The nozzle performed smoothly and free of failures *
*
mechanical
*
The conclusion of the ground tests in Ajalvir represents the fulfilment of the Technology Demonstration Phase. From this point onwards, the next steps to be taken include a continuation of the general studies on Thrust Vectoring, as well as the continuation of the feasibility study with DASA and MTU. Additionally, altitude tests with the prototype nozzle are scheduled for the second quarter of 2000 at the Altitude Test Facility (ATF) in Stuttgart. The next big milestone in he Thrust Vectoring programme will necessarily be a flight programme, in order to validate the TVN in flight condition. Consequently, ITP as well as all ITP’s partners are strongly pursuing this possibility. ITP THRUST VECTORING NOZZLE PROGRAMME ITP THRUST VECTORING NOZZLE PROGRAMME 1990-94
1995
1996
1997
1998
1999-2002
Concept Design, Patents, Mock-ups Preliminary and Aerodynamic Design Demonstrator Nozzle Design Advanced Material Orderings Component Manufacture Manufacture of Actuators Design of Control System (MTU) Component Testing Manufacture of Control System (MTU) Actuator and Control System Testing (MTU) Test Bed Modification Prototype Assembly and Instrumentation Integration in EJ200 Engine Ground Testing Extensive Instrumentation Results Flight Programme
Fig. 18.- ITP Thrust Vectoring programme EXTERNAL FILM COOLING
7.- CONCLUSIONS
NOZZLE
DOUBLE SKIN
WATER COOLING
EXISTING REAR DETUNER
WATER SUPPLY LINE
Fig. 17.- Modifications to Test Cell *
*
*
•
Thrust Vectoring offers great advantages for modern military aircraft, in return for relatively small changes in the aircraft, and is clearly the way to go for the future.
11-10
•
Thrust Vectoring technology has become available in Europe, helped by the R&D programme conducted by ITP, especially after the ground test of the prototype nozzle.
•
The ITP design presents some advantages relative to other designs, which may prove vital on the long term.
•
The aerospace community in Europe is actively in favour of this technology, and the institutions are willing to support this.
•
With a very small number of changes to EF2000, a demonstration flight programme would be possible and produce a very important stepping stone for the introduction of this technology into service.
8.- ACKNOWLEDGEMENTS The success of ITP’s programme has only been possible with the contribution of partners and organizations, namely: Spanish Ministries of Industry and Defence, with funding through an R&D programme MTU, of Munich, Germany, developed the electronic control system under a dedicated agreement with ITP. Eurojet and the Partner Companies (Rolls-Royce, MTU and Fiat-Avio), as ITP’s partners in the EJ200 development programme for Eurofighter, gave support to ITP. CESA, of Getafe, Spain, designed the hydraulic actuators for the TVN. Sener, of Las Arenas, Spain, who started in the programme many years ago, also contributed to the engineering work of the programme. DASA, of Munich, Germany, as partner in the Eurofighter feasibility study, provided the assessment of requirements and benefits for EF2000 with TVN.
11-11
Paper#A11
Q, by P. M. Lodge: What is the level of redundancy of the nozzle actuation? A. (D. Ikaza) Simplex for the ground tests. Simplex will also be taken to flight for EF2000
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The contract to supply Eurofighter's propulsion system was awarded to EuroJet Turbo GmbH in 1986. EuroJet is a consortium of companies from each partner nation and after workshare changes; Rolls-Royce of the UK has 36%, MTU (Motoren-und Turbinen-Union) of Germany has
Turbo GmbH
30%, FiatAvio of Italy has 20% and ITP (Industria de Turbo Propulsores) of Spain has 14%. The partnership has resulted in the EJ200 advanced turbofan and associated management systems.
EuroJet 200 Origins and Technology The EJ200 started life in 1982 as the Rolls Royce/British MoD XG-40 Advanced Core Military Engine or ACME demonstrator. This programme, split into three phases; technology (1982-88), engine (1984-89) and assessment (1989-95) developed new fan, compressor, combustor, turbine (including high temperature life prediction) and augmentor systems using advanced materials and new manufacturing processes. The first full engine commenced rig testing in December 1986 with the final XG-40 running for some 200 hours during 4000 cycles bringing the programme to a close in June 1995. Upon formation of the EuroJet consortium in 1986 much of the continuing XG-40 research was used for the new programme. The requirements were for a powerplant capable of higher thrust, longer life and less complexity than previous engines. The result was a powerplant with similar dimensions to the Tornado's RB199 yet having almost half as many parts (1800 against 2845 for the RB199) and delivering nearly 50% more thrust. A very noticeable difference between the two engines can be seen by comparing the turbine blade Cross section of EJ200 © MTU
designs. Compared to the RB199 the EJ200's blades are enormous and
show leanings towards sustained transonic and supersonic flight profiles. The EJ200 is an advanced design based on a
Single Crystal Turbine Blades
fully modular augmented twin-spool low bypass layout. The compressor utilises a three stage Low Pressure Fan (LPF) and a five stage High Pressure Compressor (HPC). The fan features wide-chord single crystal blade/disc (blisk) assemblies designed for low weight (including the removal of guide vanes), high efficiency
On the microscopic scale all metals (and their alloys) are an arrangement of crystals. How these crystals are arranged, their size and distribution depends on what the metal or alloy is and how it was forged.
operation. The three stages achieve a pressure ratio of around 4.2:1 with an air mass flow of Cross section of rotor blades
some 77kg/s (or 170lb/s). Like the fan the five stage compressor also features single crystal
blisk aerofoils. The use of single crystals and blade/disc units can both bring enormous potential advantages to how the powerplant may be operated (see fact box). Following the fan/compression stages fuel is injected via an annular combustor designed for low smoke operation. The key factors in determining jet engine efficiency and achievable work are the temperature and pressure differences attained between the engine inlet and combustor outlet. In the EJ200's case the outlet stator temperature is in excess of 1800K with a pressure ratio (achieved in just eight stages) of some 25:1. Such a high combustor temperature requires special precautions be taken with the High Pressure Turbine, or HPT which is directly downstream. To help reduce this problem the HPT uses air cooled single crystal blades. However there is a limit to what can be achieved using air cooling. In fact it eventually becomes detrimental to use cooling because it adversely effects the achievable combustion temperature and thus reduces efficiency. To overcome this the EJ200's HP turbine blades also utilise a special Thermal Barrier Coating, or TBC. This barrier is comprised of two plasma deposited layers, a special bonding coat over which a top layer of a Nickel-Chromium-Yttrium ceramic material is applied. Although this increases the life of the blade and increases the achievable operating temperature it does require regular inspection to ensure the coating remains viable. Following the single HPT is a further single Low Pressure Turbine (or LPT) stage again employing single crystal blades. In both the HPT and LPT a powder metallurgy disc is employed. A titanium alloy based mono-parametric convergent/divergent (Con-Di) nozzle completes the engine improving achievable thrust while helping to optimise the system for different flight profiles.
The vast majority of turbine blades are now made from a Nickel or Titanium based superalloy. The alloy will contain a variety of elements (their amounts are typically proprietary and well guarded!) such as Tungsten, Cobalt, Chromium, etc. The resulting material is extremely hard and difficult to machine and thus blades tend to be forged in a process called investment casting. When forged using traditional constant temperature furnaces the blade contains many small precipitates of various compounds (Cobalt, Tungsten, Ni3 Al, Ni3 Ti, etc.). This resolves certain physical problems with older generation blades (such as problems with power law creep) but unfortunately at high temperatures the blade can still deform irreversibly due to a process known as diffusional creep. To vastly reduce this creep problem (which is basically caused by the small, random
Powder Metallurgy
grain structure) a different approach to manufacture is taken in which giant single crystals are grown. This is achieved by using either a special furnace across which a temperature gradient can be applied or by slowly moving the blade mould through the furnace, a process called Directional Solidification. The resulting rotor is very resistant to both diffusional creep and power law creep and thus may be used at higher operating temperatures. Thus the efficiency of the jet engine is improved and it becomes possible to run the engine under more extreme conditions (such as cruising supersonically) for longer.
Overall the EJ200 employs a very low By-Pass Ratio (the ratio of air which bypasses the core engine or compressor
Most metal structures and items are constructed by milling a solid piece of forged material. However over recent years a different method of forming has become possible using powdered metals.
stages) of 0.4:1 which gives it a near turbo-jet cycle. Such a low BPR has the benefit of producing a cycle where the maximum attainable non-afterburning thrust makes up a greater percentage of total achievable output. At its maximum dry thrust of 60kN (or 13,500lbf) the EJ200's SFC is in the order of 23g/kN.s. With reheat the engine
The major benefit of powder metallurgy is that it can produce a component with typically >95% the density of a forged/machined equivalent but at lower cost. The actual procedure used is actually quite straightforward. The metal powder (or combination of blended powders) is compressed under high pressure into a mould of the component to be produced. It may also be possible to incorporate special compounds in the metal powder blend to enhance for example, temperature resistance or aid lubrication. The mould containing the compressed powder mix is then be fired or sintered. Upon cooling the mix crystallises to form a solid component.
delivers around 90-100kN (or 20,250-22,500lbf) of
The result is a relatively cheap component that can exhibit very similar physical properties to equivalent machined/forged items but at lower cost.
cruising at M1.2 at altitude (11000m/36000ft) without reheat and for extended periods. Later
thrust with an SFC of some 49g/kN.s. Compared to other engines these figures may actually seem relatively high, however such data must be used with caution and evaluated with all other performance data to be of any use. With reheat the engine weighs just 2286lb giving a Thrust to Weight Ratio of around 9:1. An interesting point to note is that the baseline production engine is also capable of generating a further 15% dry thrust (69kN or 15525lbf) and 5% reheat output (95kN
or 21263lbf) in a so called war setting. However utilising this capability will result in a reduced life expectancy. Much is currently being made about supercruise, that is the ability to cruise supersonically without the use of reheat (afterburn) for extended periods of time. Although never stated explicitly (as for example with the U.S. F-22) the Typhoon is capable of and has demonstrated such an ability since early in its flight program according to all the Eurofighter partnets. Initial comments indicated that, with a typical air to air combat load the aircraft was capable of information appeared to suggest this figure had increased to M1.3. However even more recently EADS have stated a maximum upper limit of M1.5 is possible although the configuration of the aircraft is not stated for this scenario (an essential factor in determining how useful such a facility is). The ability to maintain transonic and supersonic flight regimes without resorting to the use of reheat is achieved mainly thanks to the advanced materials and design of the EJ200.
For times when a quick sprint is required the Typhoon can employ reheat with an upper (design) limit of Mach 2.0.
EJ200 development Since the first EJ200 ran in 1991 some 14 development engines have been constructed. The first three plants were for design verification amassing some
EJ200 Specification Length, m (ft,in)
~ 4.0 (~ 13'2")
placed in Accelerated Simulated Mission Endurance Testing, or ASMET. These
Diameter, m (ft,in)
~ 0.85 (~ 2'9")
prototypes (designated EJ200-O1A) were used to verify the engine design and
Dry Thrust, kN (lbf)
>60 (>13500)
with Reheat, kN (lbf)
>90 (>20250)
two aircraft were equipped with Tornado ADV class Turbo-Union RB199-104D
By-Pass Ratio
0.4:1
engines (the D signifies the removal of the thrust reversal buckets). These have
Total Pressure ratio
25:1
Fan Pressure ratio
4.2:1
Air mass flow, kg/s (lb/s)
77 (170)
SFC dry, g/kN.s
23
SFC reheat, g/kN.s
49
~700 hours of bench test time. Another 11 engines were then constructed and
reliability. During this stage the first two Development Aircraft, DA1 and DA2 entered flight testing. Since the EJ200 had not been certified for flight these first
have a significantly lower dry thrust, some 42.5kN, than the EJ200 but are approximately the same size. In mid-1998 these RB199's were replaced with EJ200-03A models (see below). So far over 10000 hours of combined rig testing have been achieved of which some 2800 hours were in altitude testing facilities. In addition the EJ200 has completed well over 650 real flights in the various Development Aircraft from sea level to 15000m (50000ft) and from 135kts through M2.0.
The first Eurofighter to receive the (flight certified) EJ200-01A was the Italian DA3 in 1995 with its first flight in June of that year. The remaining development aircraft also use the EJ200 powerplant (both the EJ200-01A and 01C), but the DA3 remains the primary engine integration aircraft. The DA3 has been used for testing not only the EJ200 itself, but also the Full Authority Digital Engine Control (FADEC) system and Auxiliary Power Unit (APU). In April 1997 EuroJet completed and obtained flight certification on the full pre-production model engine, the EJ20003A. In January 1998 EuroJet signed production and production investment contracts with NETMA for some 1500 engines worth around DM12.5B covering the basic order of 620 Eurofighter's. Following this in January 1999 EuroJet received official orders for the first 363 engines to equip the 148 Tranche-1 Typhoon's as well as providing a number of spares. In June 1999 EuroJet obtained flight clearance for the final production standard powerplant with production release scheduled to occur by the end of 1999. The first two production engines were handed over to BAE on the 12th July 2001 at Rolls Royce's Filton plant in Bristol. They were subsequently integrated into IPA1, the first production Eurofighter, at BAE's Warton facility.
Engine Management
Production model EJ200 © Rolls Royce
The EJ200 is controlled by both an Engine Control Unit and a fuel management system supplied by LucasVarity Aerospace. The primary engine control system developed by ENOSA and Technost SpA under the leadership of Dornier (an DASA company) and Smiths Industries is a Full Authority Digital Engine Control, FADEC unit. Its responsibilities include overall engine management,
including afterburn fuel flow and control of the nozzle area. The third system comprises the Engine Monitoring Unit (EMU) developed by ENOSA, BAE Systems and Microtechnica. Its sole purpose is the self diagnosis of engine faults, it thus augments the structural health monitoring system. The EMU takes its input from both the fuel management and FADEC units as well as a full array of dedicated sensors within the engine.
Future of the EJ200 Engine uprating The EuroJet consortium were required to build an engine (often referred to as EJ2x0) which had at least a 20% growth potential. There are already plans to carry out the necessary modifications to reach this higher (Stage-1) output in the 2000 to 2005 timeframe. Such an improvement will require a new Low Pressure Compressor (raising the pressure ratio to around 4.6) and an upgraded fan (increasing flow by around 10%). This would result in the dry thrust increasing to some 72kN (or 16,200lbf ) with a reheated output of around 103kN (or 23,100lbf). Given recent increases in the weight of the Typhoon it may not be unexpected to find this upgrade performed in the near future. More interestingly perhaps is Rolls-Royce and EuroJet's plan to increase the output 30% above the baseline specification as a Stage-2 modification. Such an upgrade will require more substantial plantwide changes including a new LP compressor and turbine and an improvement in the total pressure ratio. These upgrades would yield a new dry thrust of around 78kN (or 17,500lbf) with a reheated output of around 120kN (or 27,000lbf). The indications are that these improvements will come on stream between 2005 and 2010, in time for the Typhoon's Mid Life Upgrade expected around 2016.
Thrust Vectoring Control As well as the potential for increasing the EJ200's thrust there are also plans to incorporate a
Thrust Vectoring
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). 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
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.
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 CAD image of nozzle during vectoring © ITP R&D
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. 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
Vectoring configurations © ITP R&D
careful placement of the struts, problems with the nozzle petals overlapping or colliding are also removed. Since rig trials commenced in 1998 the TVC equipped EJ200-01A has run for 80
Click either image for alternative versions
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
Rig trials of 3DTVC equipped EJ200 © ITP R&D
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 nonreheat 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. The webmasters would like to express their thanks to ITP R&D for providing the information and material on the 3DTVC nozzle and Rolls Royce for material on the XG-40 and EJ200. Sources : [1] : Rolls-Royce Online [2] : Rolls-Royce, Press Office, Derby [3] : EuroJet GmbH, Public Relations [4] : Janes All the Worlds Aircraft 1996/97 [5] : Janes Avionics 96/97 [6] : Eurofighter 2000, Hugh Harkins, Key Publishing, 1997 [7] : Defence Data On-Line [8] : DASA technical paper, Military Technology, December 1997 [9] : Engineering Materials 1, M. F. Ashby and D. R. H. Jones, Pergamon Press [10] : Industria de Turbo Propulsores S.A., Spain [11] : Smiths Industries plc. [12] : Flight International, 16-22 June 1999 [13] : Bill Sweetman, World Air Power Journal, 38 [14] : EADS NV, Military Aircraft Division, Munich, Germany
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