Aerodynamic modification kit

[Zahnatom]

1 hour ago, F-2 said:

Yes your right but the claim was 10% better ITR vs 15% on the AMK, so at least a good chunk of the benefit was possible early on if not the full thing.

yep.

if i understand the paper that i linked correctly, then the ITR is artifically limited due to unwanted rolling and yawing at high AoA. this effect is reduced by introducing different fuselage strakes(i'm not a mechanical engineer lol).

the extended flaperons are unfortunately not discussed in the paper but the cited source ("Hitzel, S. M., Osterhuber, R., “Enhanced Maneuverability of a Delta-Canard Combat Aircraft by Vortex Flow Control”, Journal of Aircraft, Volume 55, Number 3, pp1090-1102, May-June 2018") should include more of that

Edited January 25, 2023 by Zahnatom

[Spectre11]

9 hours ago, Zahnatom said:

yep.

if i understand the paper that i linked correctly, then the ITR is artifically limited due to unwanted rolling and yawing at high AoA. this effect is reduced by introducing different fuselage strakes(i'm not a mechanical engineer lol).

the extended flaperons are unfortunately not discussed in the paper but the cited source ("Hitzel, S. M., Osterhuber, R., “Enhanced Maneuverability of a Delta-Canard Combat Aircraft by Vortex Flow Control”, Journal of Aircraft, Volume 55, Number 3, pp1090-1102, May-June 2018") should include more of that

 

The ITR is limited because the AoA is limited to a point by which maximum lift cannot be exploited. The AoA limit and limiting roll authorities at higher AoAs serve the purpose to avoid the problem area where the aircraft tends to exceed the beta angle limits as airflows become too unstable. When the issues were discovered relatively late in the flight test programme the fix was to reduce the max AoA limit and roll rate at high AoA. This reduced the aircraft's maneuverability. The Eurofighter Enhanced Maneuverability programme (EFEM) was launched to address the shortfalls and the original strakes trialed onboard DA5 represented a first step. These wing apex strakes or LEX generate powerful vortices which energise the airflow over the wings, increasing total lift and delaying airflow separation at higher angles of attack. The stabilisation of the airflow allowed the AoA limit to be increased and the lateral/directional stability issues to be addressed. The AMK represents the next step, where the shape of the LEX is slightly altered and the fuselage strakes are changed in shape from almost rectangular to delta. Once again this helps to produce even more powerful vortices and combined with the LEX increases lift and stability. It also causes a forward shift of the pressure point aka lift centre. To compensate for this the flaperons were enlarged. A side effect of this is greater control authorities in the roll axis increasing the roll performance across the envelope. This in sum increases the nose pointing authority, maximum lift and thereby ITR. STR benefits to a certain extend due to the improvements in lift/drag ratio and the minimum speed is reduced translating into lower rotation and approach speeds during takeoff and landing. Roll performance is notably increased at higher AoA as the airflows are now much more stable at high AoA and roll rates.

[Zahnatom]

27 minutes ago, Spectre11 said:

The ITR is limited because the AoA is limited to a point by which maximum lift cannot be exploited. The AoA limit and limiting roll authorities at higher AoAs serve the purpose to avoid the problem area where the aircraft tends to exceed the beta angle limits as airflows become too unstable. When the issues were discovered relatively late in the flight test programme the fix was to reduce the max AoA limit and roll rate at high AoA. This reduced the aircraft's maneuverability. The Eurofighter Enhanced Maneuverability programme (EFEM) was launched to address the shortfalls and the original strakes trialed onboard DA5 represented a first step. These wing apex strakes or LEX generate powerful vortices which energise the airflow over the wings, increasing total lift and delaying airflow separation at higher angles of attack. The stabilisation of the airflow allowed the AoA limit to be increased and the lateral/directional stability issues to be addressed. The AMK represents the next step, where the shape of the LEX is slightly altered and the fuselage strakes are changed in shape from almost rectangular to delta. Once again this helps to produce even more powerful vortices and combined with the LEX increases lift and stability. It also causes a forward shift of the pressure point aka lift centre. To compensate for this the flaperons were enlarged. A side effect of this is greater control authorities in the roll axis increasing the roll performance across the envelope. This in sum increases the nose pointing authority, maximum lift and thereby ITR. STR benefits to a certain extend due to the improvements in lift/drag ratio and the minimum speed is reduced translating into lower rotation and approach speeds during takeoff and landing. Roll performance is notably increased at higher AoA as the airflows are now much more stable at high AoA and roll rates.

about the rolling:

I've noticed that the Eurofighter does not roll around the fuselage but rather does some kind of barrel roll. In some paper(can't remember where) they mentioned that its because the pilot's head is quite high and rolling around the fuselage would exert latteral forces on the head of the pilot. Is that correct?

[Spectre11]

30 minutes ago, Zahnatom said:

about the rolling:

I've noticed that the Eurofighter does not roll around the fuselage but rather does some kind of barrel roll. In some paper(can't remember where) they mentioned that its because the pilot's head is quite high and rolling around the fuselage would exert latteral forces on the head of the pilot. Is that correct?

You'll notice from photographs and videos that there is enough clearance between the pilots head and the canopy. The barrel rolling is more the result of its pitch instability and the lateral forces that kick in while rolling and the FCS trying to compensate for this. This phenomen is somewhat less pronounced on later aircraft where the control laws have been further refined.

[F-2]

7 hours ago, Spectre11 said:

The ITR is limited because the AoA is limited to a point by which maximum lift cannot be exploited. The AoA limit and limiting roll authorities at higher AoAs serve the purpose to avoid the problem area where the aircraft tends to exceed the beta angle limits as airflows become too unstable. When the issues were discovered relatively late in the flight test programme the fix was to reduce the max AoA limit and roll rate at high AoA. This reduced the aircraft's maneuverability. The Eurofighter Enhanced Maneuverability programme (EFEM) was launched to address the shortfalls and the original strakes trialed onboard DA5 represented a first step. These wing apex strakes or LEX generate powerful vortices which energise the airflow over the wings, increasing total lift and delaying airflow separation at higher angles of attack. The stabilisation of the airflow allowed the AoA limit to be increased and the lateral/directional stability issues to be addressed. The AMK represents the next step, where the shape of the LEX is slightly altered and the fuselage strakes are changed in shape from almost rectangular to delta. Once again this helps to produce even more powerful vortices and combined with the LEX increases lift and stability. It also causes a forward shift of the pressure point aka lift centre. To compensate for this the flaperons were enlarged. A side effect of this is greater control authorities in the roll axis increasing the roll performance across the envelope. This in sum increases the nose pointing authority, maximum lift and thereby ITR. STR benefits to a certain extend due to the improvements in lift/drag ratio and the minimum speed is reduced translating into lower rotation and approach speeds during takeoff and landing. Roll performance is notably increased at higher AoA as the airflows are now much more stable at high AoA and roll rates.

Hey so apparently the Eurofighter has a AoA/G override. Does that me we should be able to get AMK performance when Load permits?

 

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Raising the tempo

15 April 1997

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The Eurofighter EF2000 programme is about to enter what may prove to be its most critical phase, with funding and workshare again presenting the stumbling blocks. Despite this, however, the project remains robust in many areas. 

The four Governments involved in the project need, by the end of May, to sign memorandum of understanding (MoU) 6, covering production, and MoU 7 (logistical support), to push the multi-national programme towards "industrialisation" and production. While the UK is committed to the programme, and few problems are expected from Spain, Germany is again causing a storm of doubt, and Italy is expected to arrive at the table only at the last moment. There is concern in military and some Government circles that the MoUs will not be in place in time for the relevant contracts to be signed during the Paris air show at Le Bourget in mid-June. 

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National requirements are still fixed at 232 aircraft for the UK, 180 for Germany, 121 for Italy and 87 for Spain - making a total of 620 aircraft (522 single-seaters and 98 fully operational two-seaters). These numbers are relevant because they form the basis for the division of production work, which makes the possibility of further reductions a serious concern for the national aerospace industries involved. They are worried that they may be forced to use their own money to keep the programme on schedule and allow them to meet existing target dates. 

Production is due to start in 2000, for first deliveries a year later. The aircraft delivered will be to the initial-operational-capability (IOC) standard, with almost complete air-to-air capability. The final-operational-capability (FOC) EF2000 will not be available before the year 2003, but it is expected that all the IOC aircraft will then be retrofitted and upgraded to the higher standard. 

 

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Testing the aircraft 

The development programme is finally progressing without serious problem. All seven prototypes have been built, and are due to be flown for a total of 4,700h in test flights. As seven aircraft are not sufficient to complete the integration and certification of the different national weapons systems, five initial production aircraft (IPA) will be added to the test programme, and these are expected to be flown for another 800h. In theory, these could be brought to FOC standard and then used in front-line service, but it is expected that, in the end, they will be used at the various air-force test centres. 

The most critical item in the early days of the programme was the digital flight-control system (DFCS). The initial package (FCS 0) was used early on, just to put the first prototype aircraft safely in the air. Tests were then carried out on FCS 1 with the Eurojet EJ200 engines, and FCS 2 is now being standardised on all prototypes. This will allow the flight envelope to be opened to higher angles of attack (AoA), heavier weights and higher g. The FCS 2A will allow the demonstration and testing of "carefree handling", while FCS 2B will allow departure testing. FCS 3 will be fitted into the IOC aircraft. 

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Flight-test progress 

The EF2000 has been flown up to 650kt (1,200km/h), sustained 6.5g and Mach 1.8, with a maximum stabilised AoA of 20 degrees. By early June it will have reached Mach 2, 750kt, 7.5g and 25-27 degrees AoA. These will be the maximum limits of the EF2000 demonstration routine at the Paris air show where, it has been decided, the Italian DA7 prototype will be used to fly a routine which will, for the first time, give the public a glimpse of the fighter's true capabilities. 

The initial EJ200-1A engines have been replaced by 1Cs (which meet about 95% of target performances), while the first production-standard engines (3As) will be fitted on the Italian DA3 prototype in the second half of 1997. The only problem with the engine has been observed during throttle chopping in combat conditions, but this is regarded as "a marginal problem" by manufacturer Eurojet. The engines are being put through the second six-week "customer-testing" phase at Turin by a joint force of about 50 technicians and test pilots from the four air forces. 

The EF2000 has been tested once, almost by accident, in "supercruise" mode - flying at supersonic speed, with the engine at full dry power (without afterburner). On the occasion in question, a prototype aircraft, carrying more than 50% fuel and six dummy missiles, was taken to Mach 1.4 at 40,000ft (12,200m) with the afterburners engaged. The pilot eased back the throttle, cutting the afterburners, and the aircraft continued at more than Mach 1. As a result, Eurofighter is now to devote more test hours with the final engines to see whether the aircraft is capable of flying operationally in supercruise - a capability which could boost dramatically the potential of the aircraft, in terms of combat radius and stealth. The only other fighter so far developed to this requirement is the Lockheed Martin/Boeing F-22. 

A "cockpit committee", made up of industry and air-force test pilots, is still discussing the cockpit size, the placement and travel of the stick, and the head-up display and cathode-ray tube (CRT) symbology. Among the decisions to emerge from the debates is the possibility that CRT displays will be replaced by more advanced liquid-crystal displays. Another is to provide a g/AoA-limiter override button, which would allow an operational pilot in an emergency situation to disconnect the computer control which prevents the aircraft from going outside the designed speed/AoA/g limits. It is also felt that the EF-2000 should have a "panic button" to restore the aircraft to wings level, in a slightly climbing attitude. 

Since flight tests began, the aircraft has remained more or less unchanged, with no major engineering-changes proposed. The aircraft is still under 10t empty weight, although by only a few grammes. The magic line will be crossed soon, as the aircraft is to be strengthened to meet new-air-to-ground requirements, pushed mostly by the Royal Air Force. 

Originally, these requirements were not so important for at least two of the four air forces and, during the cost-cutting exercises, some of the originally planned air-to-ground features (such as in the DFCS and the ECR-90 radar) were dropped. It became clear, however, that a "pure-fighter" EF2000 was not going to reach its full potential on the market outside the four original customers. Most possible future clients are interested in a fighter-bomber. 

It also became clear that an EF2000 with air-to-ground capabilities could be interesting even to the original four partners. The German air force is to order another 40 EF2000s in the next century, to replace some of its Panavia Tornado IDS, and the RAF is not ruling out a follow-on order for strike EF2000s to replace at least some of its fighter bombers. On the international market, the idea is to propose a multi-role EF2000, with relaxed air-to-air capabilities, but improved strike performance. 

The four air forces are discussing which modifications are to be included in the final design before production starts. The requirement now is to carry heavier and bulkier weapons, and the wing is to be strengthened and some wing pylons modified. The aircraft is to be cleared for a heavier external payload, meaning that an increased maximum take-off weight will be required, and possibly a modified undercarriage to handle these weight increases. 

The armament-control system is to get new air-to-ground software and some of the radar/DFCS modes could come back. The engineers are also evaluating what modifications to the inlet, canopy and foreplanes would be required to handle the birdstrike requirements of a fighter bomber. The EF2000 could therefore become a European McDonnell Douglas F-15E-type aircraft, with a typical mission load of four future medium-range air-to-air missiles (FMRAAMs), two advanced short-range air-to-air missiles (ASRAAMs, two underwing fuel tanks and seven 450kg bombs. 

The additional weight of the modifications is not welcomed by the fighter community, however, and every trick will be used to reduce the empty weight. A reduction of the wiring diameter, for example, could save about 30kg. There is also an argument which says that a stronger EF2000, in a pure air-to-air role with reduced weight, would have an improve lifeexpectancy. 

 

Armament 

Even if they are not officially closed yet, the discussions on air-to-air armament have nearly reached a conclusion. The EF2000 was originally to be armed by the Hughes AIM-120 active guided missile, the Alenia Aspide semi-active guided missile, the ASRAAM infra-red (IR)-guided missile and the Raytheon AIM-9 Sidewinder. Now, the Aspide and its continuous-wave illuminator are to be dropped, to make room for the FMRAAM, while the IRIS-T IR-guided missile is also to be integrated. Italy is to receive compensation for giving up Aspide integration work and testing slots. 

A decision has been reached on the external fuel tanks: the EF2000 will use 1.500litres subsonic fuel tanks (the same as for the Panavia Tornado, allowing for a cost reduction) and newly developed 1,000litre supersonic tanks. 

One of the "hot" topics is the defensive-aids subsystem (DASS), being developed by Italy, Spain and the UK (the German aircraft will be fitted for, but not equipped with, this system). The DASS is to have: 

- active jammers, with antennas fitted on wingtip pods; 

- a super heterorodyne wide-band-type electronic surveillance measures/radar-warning receiver, with antennas on the wingtip pods and on the fuselage; 

- a missile-approach warning system, (an active radar) with antennas on the wing root and the fin trailing edge; 

- and a laser warning receiver. 

The final piece of equipment is the towed decoy, proposed by the UK. The Italians are not happy with the idea of a fighter towing a long cable and a jammer, and there was a failure during early testing, when a prototype lost a towed decoy because of the aerodynamc stresses induced on the 100m cable by the spiralling decoy. The Italians are following a different approach, pushing an advanced electronic countermeasures system, the Cross Eye, under development with Italian air force funding. The Cross Eye, using antennas placed in the wingtip pods, creates a smart "trick", causing an angular error in the target radar. 

To avoid a battle between the two partners, they have been requested to look at whether the EF2000 will carry both the towed decoy and the Cross Eye. The ideal solution was to carry two towed decoys and the Coss Eye, but there is no room for all of this in the pods. There is the possibility of having a single decoy and the Cross Eye, but a final decision is not forecast soon. 

The EF2000 defensive suite is completed by a launcher for smart IR decoys and chaff. It was originally planned also to have smart decoys, and the Texas Instruments GEN-X was evaluated, but not picked up. In the future, a radio-frequency decoy is to be integrated, but for the moment the EF2000 will rely on "jaff" - chaff clouds illuminated by an RF beam from the onboard jammer. 

 

Future Development 

Although the EF2000 is still at prototype level, the engineers are already discussing possible future developments. One of the most promising projects involves the integration of thrust-vectoring nozzles. From the beginning, the EF2000 was designed with a thrust-vectoring retrofit in mind. The Spanish team is working on a simple and light, yet effective, three-ring nozzle which could be retrofitted in the future, boosting the combat performance of the aircraft, especially in the "furball", the close-combat arena, with increased pitch control. The main problem is not in developing the nozzle, but in modifying the DFCS software, which will have to be almost totally rewritten. 

Export clients outside NATOare expected to be offered a special downgraded version of the EF2000, with some of the aircraft's capabilities "relaxed" and with an emphasis on the multi-role performance. 

The two-seater version is still being discussed by the four partners as they try to establish the operational advantages of having some EF2000 two-seaters working alongside single- seaters. The two versions have almost the same performance and capabilities because the two-seaters are intended to be fully operational. 

 

Training 

The four client air forces are engaged in lengthy discussions on the rationale of establishing a joint crew-training centre. A qualification test and evaluation (QTE) centre could provide a good way of cutting the training bill and for having a true standardisation among the four air forces' EF2000 units, at least for basic training. Unfortunately, Germany can not easily participate in this scheme, because its air force has moved most of its training to the USA. 

Spain is proposing Torejon or Saragoza as a training base, while Italy can offer bases in southern Italy, such as Amendola or Decimomannu in Sardinia. Italy faces opposition from enviromentalists - a QTE means 100-150 daily sorties and this may not be accepted by locals. That may mean each of the four air forces opting for its own training centre. 

Source: Flight International

 

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Another is to provide a g/AoA-limiter override button, which would allow an operational pilot in an emergency situation to disconnect the computer control which prevents the aircraft from going outside the designed speed/AoA/g limits. It is also felt that the EF-2000 should have a "panic button" to restore the aircraft to wings level, in a slightly climbing attitude. 

 

[Spectre11]

3 hours ago, F-2 said:

Hey so apparently the Eurofighter has a AoA/G override. Does that me we should be able to get AMK performance when Load permits?

 

 

 

No there is no override function implemented. The FCS has been provisioned for g-override, but it isn't enabled, so if you pull the stick beyond the spring out forces nothing happens.

[F-2]

2 hours ago, Spectre11 said:

No there is no override function implemented. The FCS has been provisioned for g-override, but it isn't enabled, so if you pull the stick beyond the spring out forces nothing happens.

I saw some mention of it in Janes as well.

 

you seem very knowledgeable, have you worked on the Eurofighter in someway?

[F-2]

AMK kit on the EK mock up. Is it coming?

[Zahnatom]

1 hour ago, F-2 said:

AMK kit on the EK mock up. Is it coming?

its possible.

IIRC thats also the Eurofighter mock up with the WAD

[Swayer]

22 hours ago, Zahnatom said:

its possible.

IIRC thats also the Eurofighter mock up with the WAD

Hopefully I’m wrong , but now I don’t think we’re going to get the AMK due to it not being operational

But haven’t developers added features or weapons that were never operational ?

[Zahnatom]

21 hours ago, Swayer said:

Hopefully I’m wrong , but now I don’t think we’re going to get the AMK due to it not being operational

But haven’t developers added features or weapons that were never operational ?

i'm pretty sure they meant "Is it coming" as in "is it going to be installed on IRL Eurofighters" and not "is HB/TG going to add it"

[F-2]

https://www.key.aero/article/making-eurofighter-typhoon-today-fit-tomorrow
 

https://www.eurofighter.com/the-programme

 

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Current Programme 4 Enhancement (P4E) is under negation and shall be available in 2028 to all Nations. Aerodynamic Modification Kit (AMK) is planned to be part of the P4E growth path and will enable an AMK initial clearance assuring more flexible and heavier weapon configurations and new weapon integration. Enhanced data recording capability will be realised through a Ground Data Loader and Recorder (GDLR).

It looks like AMK will be part of P4E unless something changes 

[Zahnatom]

9 hours ago, F-2 said:

https://www.key.aero/article/making-eurofighter-typhoon-today-fit-tomorrow
 

https://www.eurofighter.com/the-programme

 

It looks like AMK will be part of P4E unless something changes 

speaking of P4E

Taurus air-launched cruise missile looks for new contracts and at technology insertions - EDR Magazine

[F-2]

10 minutes ago, Zahnatom said:

speaking of P4E

Taurus air-launched cruise missile looks for new contracts and at technology insertions - EDR Magazine

AMK opens up a lot of possibilities for different loads and weapons intergration. I’d expect more of this

[Zahnatom]

12 minutes ago, F-2 said:

AMK opens up a lot of possibilities for different loads and weapons intergration. I’d expect more of this

yep, should increase the maximum weight that can be carried.

though i dont think that was an issue so far lol