PAK FA preliminary Stealth Assesment - Ausairpower

[Drsomnath999]

APA has released a new paper on stealth assesment on pak-fa ,but as this is a long article i am posting only few important paragraphs which are relevant


A Preliminary Assessment of Specular Radar Cross Section Performance in the Sukhoi T-50 Prototype

Air Power Australia Analysis 2012-03
12th November 2012

Introduction

The Russian Sukhoi/KnAAPO T-50/I-21/Article 701 PAK-FA (Перспективный Авиационный Комплекс Фронтовой Авиации) was the first manned combat aircraft design intended to possess low observable capabilities in the radar bands to be developed and publicly flown by a nation other than the United States, the first public flight shown in early 20101.

This paper extends earlier research focussed on the design of the T-50, and the Chengdu J-20, to provide a more accurate and quantitative preliminary assessment of the specular Radar Cross Section [RCS] of the T-50 design2,3.

A full and comprehensive assessment of the RCS of any Low Observable [LO / -10 to -30 dBSM, Refer Table A.1] or Very Low Observable [VLO / -30 to -40 dBSM, Refer Table A.1] aircraft design is a non-trivial task, as careful consideration needs to be given to all major and minor RCS contributors in the design, of which there can be a large number in a complex design such as a combat aircraft.

If such an assessment is to be genuinely useful, it must consider the vehicle's RCS from a range of different angular aspects encompassing azimuthal sectors and also elevation or depression angles characteristic of the surface and airborne threat systems the LO/VLO design is intended to defeat [Refer Figures A.3 and A.4].

The assessment of RCS must always be performed at the operating wavelengths typical of the surface and airborne threat systems the LO/VLO design is intended to defeat [Refer Table A.2].

Definitions of these and other terms employed in this document are summarised in Annex C. Reference data for RCS scales, radio-frequency bands, engagement geometries are summarised in Annex A. A summary of representative threat systems is available in Annex A, in an earlier publication3.

The T-50 was developed specifically to compete against the F-22 Raptor in traditional Beyond Visual Range (BVR) and Within Visual Range (WVR) air combat. As a result, the T-50 shares all of the cardinal "fifth generation" attributes until now unique to the F-22 - stealth, supersonic cruise, thrust vectoring, highly integrated avionics and a powerful suite of active and passive sensors.

The PAK-FA therefore firmly qualifies as a "fifth generation" design. In addition, it has two further attributes not introduced in the F-22 design. The first is "extreme plus agility"2, resulting from advanced aerodynamic design, exceptional thrust/weight ratio performance and three dimensional thrust vectoring integrated with an advanced digital flight control system. The second attribute is exceptional combat persistence, the result of an unusually large 25,000 lb internal fuel load. The former entailed some shaping compromises, at the expense of specular RCS performance.

The basic shaping design observed on prototypes of the PAK-FA will deny it the critical all-aspect stealth performance of the F-22, critical in BVR air combat and deep penetration operations. Despite this, the extreme manoeuvrability/controllability design features of the PAK-FA, which result in extreme plus agility, result in the potential for the PAK-FA to become the most lethal and survivable fighter ever built for air combat engagements.

The publicly displayed PAK-FA prototypes do not represent a production configuration of the aircraft, which is to employ a new engine design, and extensive VLO treatments which are not required on a prototype.

This assessment, like the earlier assessment performed on the J-20 design, cannot be more than preliminary for a number of important reasons:
The final airframe shaping remains unknown, and changes may arise through the development cycle, to improve aerodynamic performance, operational characteristics, and LO/VLO performance;
The state of Russian Radar Absorbent Materials (RAM), Radar Absorbent Structures (RAS) and radar absorbent coatings technology is not well understood in the West;
The state of Russian technologies for sensor aperture (radar, EO, passive RF) structural mode RCS reduction is not well understood in the West;
The state of Russian technologies for RCS flare spot reduction, in areas such as navigation/communications antennas, seals, panel joins, drain apertures, cooling vents, and fasteners is not well understood in the West.
Achievement of credible LO or VLO performance is the result of a design having intended RCS characteristics in all of these categories4.

Proper airframe shaping, as stated in Denys Overholser's famous dictum, is a necessary and essential prerequisite for good LO or VLO performance. If shaping design is deficient, no amount of credible materials application and detail flare spot reduction can overcome the RCS contributions produced by the airframe shape, and genuine VLO performance will be therefore unattainable. While this is self-evident, it is often not well appreciated.

If airframe shaping is credible, then careful and well considered application of Radar Absorbent Materials (RAM), Radar Absorbent Structures (RAS), radar absorbent coatings, aperture RCS reductions, and minor flare spot reduction techniques will yield a VLO design.

Modelling of the shape related RCS contributions of any VLO design is of very high value, as it determines not only whether the aircraft can achieve credible VLO category performance, but also where the designers will be investing effort in RAS, RAM and coating application to achieve this effect. Moreover, it exposes the angular extents within which the aircraft has poor RCS performance, and thus provides a robust basis for development of tactics and technique to defeat the design.

This paper will focus mostly on shape related RCS contributions, both due to the high value of knowing weaknesses in the design, but also due to the uncertainties inherent in estimating the performance of unknown technologies for RAS, RAM, coatings, aperture RCS reductions, and minor flare spot reduction. Where applicable, reasonable assumptions will be made as to the performance of absorbent material related RCS reduction measures.

T-50 Prototype Very Low Observable Airframe Shaping Design Features

Figure 1. The lower fuselage of the prototype displays interesting incongruities. There is an abrupt transition between the carefully sculpted faceting of the inlet nacelles, and the smoothly curved aft engine nacelles and conventional aft fuselage. The faceting strategy is similar to the F-22 design rules, with singly or doubly curved transitions between planes (C. Kopp/Sukhoi image)2.

An extensive qualitative analysis of RCS reduction shaping feature design in the T-50 aircraft was performed in 2010. That analysis yielded the following observations, cited here for convenience2:

1.The forward fuselage is closest in general configuration to the YF-23, especially in the chining, cockpit placement, and hump aft of the cockpit canopy, although the blending of the upper forward fuselage into the upper carapace is more gradual.

2.There are important differences from the YF-23. The chine curvature design rule is purely convex, like the chine design on the F-22A. The nose height is greater, to accommodate an AESA with a much larger aperture than that intended for the YF-23 or F-22A.

3.If flare spots are properly controlled by the application of materials and serrated edge treatments around the canopy, and a good bandpass radome design using a frequency selective multilayer laminate is employed, the shaping related RCS contribution of the forward fuselage in the S/X/Ku-bands will be similar to that observed with the F-22A, YF-23 or F-35.

4.The edge aligned movable LEX are readily treated with leading edge absorbers and will not present a major RCS flare spot. The treatment of the movable join will present the principal challenge in this portion of the design. The obtuse angle in the join between the LEX and forward fuselage is characteristic of good design and is very similar to the angles used in the F-22.

5.The edge aligned trapezoidal main engine inlets are similar in configuration to the F-22, but with important differences. The inlet aspect ratio is different, and the corners are truncated in a manner similar to the YF-23. If properly treated with leading edge inserts and inlet tunnel absorbent materials, the inlet design should yield similar RCS to its US counterparts.

6.The placement of the engine centrelines well above the inlet centroids, in the manner of the YF-23, results in an inlet tunnel S-bend in the vertical plane. Sukhoi have not disclosed whether an inlet blocker will be employed. The use of an S-bend in the PAK-FA would permit an increase in the number of surface bounces further increasing attenuation and reducing RCS.

7.In the S/X/Ku-bands the basic shaping of the forward fuselage will permit the attainment of genuine VLO performance with the application of mature RAS and RAM, where the centre and aft fuselage do not introduce larger RCS contributions from the forward aspect.

8.The wing design from a planform perspective is closest to the F-22A, and the upper fuselage similar to the YF-23, permitting the achievement of similar RCS performance to these US types, from respective aspects.

9.Where the PAK-FA falls well short of the F-22A and YF-23 is the shaping design of the lower fuselage and side fuselage, where the general configuration, wing/fuselage join angles, and inlet/engine nacelle join angles introduce similar intractable specular return problems as observed with the F-35 Joint Strike Fighter design. These are inherent in the current shaping design and cannot be significantly improved by materials application. .... the PAK-FA prototype design will produce a large specular return in any manoeuvre where the lower fuselage is exposed to a threat emitter, and this problem will be prominent from the Ku-band down to the L-band.

10.This problem is exacerbated by the inboard ventral wing root fairings, claimed by some Russian sources to be pods for the concealed carriage of folding fin close combat AAMs, such as the RVV-MD/R-74 series. While these fairings do not introduce large RCS contributions from fore or aft aspects, they will adversely contribute to beam aspect RCS, especially for threats well below the plane of flight of the aircraft.

11.The tailboom shaping is reminiscent of the F-22 and F-35 designs, and will not yield significant RCS contributions from the front or aft aspects.

12.In the lower hemisphere, it will suffer penalties due to the insufficiently obtuse join angles between the wings and stabilators, and outer engine nacelles.

13.The upper fuselage fairings which house the all moving vertical tail actuators are well shaped, and the join angles are well chosen.

14.The outward cant of the empennage fins is similar to United States designs, and like the YF-23 tail surfaces, these are fully articulated with the VLO benefit of removing surface impedance discontinuities at the join of a conventional rudder control surface.

15.The axi-symmetric 3D TVC nozzles present the same RCS problems observed with the fixed axi-symmetric nozzles used in the F-35 JSF, and the application of serrated shroud treatments and tailpipe blockers as used with the F-35 JSF will not overcome the inherent limitations of this canonical shaping design. Observed from the aft hemisphere in the L-band through Ku-bands, the PAK-FA prototype configuration will produce to an order of magnitude an equally poor RCS as the F-35 Joint Strike Fighter5.

16.The centre fuselage beavertail follows a similar chine design rule as the forward fuselage does, and will not present a significant RCS contribution from behind.

These observations reflected the design of the first prototype. Subsequent prototypes, publicly displayed, do not fundamentally differ in any of these design features.

The qualitative analysis yielded the conclusion that with proper application of materials technology, detail feature RCS reduction treatments, aperture structural mode RCS reduction measures, the T-50 had potential to yield viable VLO performance in the forward sector, and with a nozzle design similar to the F-22A, had potential for viable VLO performance in the aft sector. Performance in the beam sector and lower hemsiphere were identified as problematic. This conclusion was a result of several specific shaping features, specifically the lower fuselage tunnel design, and the absence of obtuse angle joins between the aft fuselage sides and wing / stabilator joins, and the obtuse join angles in the fuselage tunnel.

Quantitative RCS modelling will demonstrate that these observations were valid.



Conclusions

This study has explored the specular Radar Cross Section of the Sukhoi T-50 prototype aircraft shaping design. Simulations using a Physical Optics simulation algorithm were performed for frequencies of 150 MHz, 600 MHz, 1.2 GHz, 3.0 GHz, 6.0 GHz, 8.0 GHz, 12.0 GHz, 16.0 GHz and 28 GHz without an absorbent coating, and for frequencies of 1.2 GHz, 3.0 GHz, 6.0 GHz, 8.0 GHz, 12.0 GHz, 16.0 GHz with an absorbent coating, covering all angular aspects of the airframe.

If the production T-50 retains the axisymmetric nozzles and extant ventral fuselage design, the aircraft would still deliver robust Very Low Observable performance in the nose aspect angular sector, providing that effective RCS treatments are applied to suppress surface travelling waves, inlet and edge reflections.

If the production T-50 introduces a rectangular faceted nozzle design, and refinements to lower fuselage and side shaping, the design would present very good potential for good Very Low Observable performance in the S-band and above, for the nose and tail aspect angular sectors, with reasonable performance in the beam aspect angular sector. The extent to which this potential could be exploited would depend critically on the design of the nozzles and other shaping refinements.

In conclusion, this study has established through Physical Optics simulation across nine frequency bands, that no fundamental obstacles exist in the shaping design of the T-50 prototype, which might preclude its development into a genuine Very Low Observable design with constrained angular coverage.

IMAGE GALLERY

Figure 3. The T-50 has five major lobes in the left and right beam aspect angular sectors, for convenience labelled A through E, with the flat lower fuselage mainlobe labelled F (KnAAPO image).

Figure 4. Mapping of the five major lobes in the left and right beam aspect angular sectors at 16 GHz (KnAAPO image).

Figure 5. The T-50 from behind, showing the corner joins in the inlet tunnel, and fuselage sides (KnAAPO image).




SOURCE:
A Preliminary Assessment of Specular Radar Cross Section Performance in the Sukhoi T-50 Prototype

 

[Godless-Kafir]

Super like...Great article. Its to late here to read completely but will be back to analyse in detail.

Thanks Som.

 

[ersakthivel]

APA has released a new paper on stealth assesment on pak-fa ,but as this is a long article i am posting only few important paragraphs which are relevant


A Preliminary Assessment of Specular Radar Cross Section Performance in the Sukhoi T-50 Prototype

Air Power Australia Analysis 2012-03
12th November 2012

Introduction

The Russian Sukhoi/KnAAPO T-50/I-21/Article 701 PAK-FA (Перспективный Авиационный Комплекс Фронтовой Авиации) was the first manned combat aircraft design intended to possess low observable capabilities in the radar bands to be developed and publicly flown by a nation other than the United States, the first public flight shown in early 20101.

This paper extends earlier research focussed on the design of the T-50, and the Chengdu J-20, to provide a more accurate and quantitative preliminary assessment of the specular Radar Cross Section [RCS] of the T-50 design2,3.

A full and comprehensive assessment of the RCS of any Low Observable [LO / -10 to -30 dBSM, Refer Table A.1] or Very Low Observable [VLO / -30 to -40 dBSM, Refer Table A.1] aircraft design is a non-trivial task, as careful consideration needs to be given to all major and minor RCS contributors in the design, of which there can be a large number in a complex design such as a combat aircraft.

If such an assessment is to be genuinely useful, it must consider the vehicle's RCS from a range of different angular aspects encompassing azimuthal sectors and also elevation or depression angles characteristic of the surface and airborne threat systems the LO/VLO design is intended to defeat [Refer Figures A.3 and A.4].

The assessment of RCS must always be performed at the operating wavelengths typical of the surface and airborne threat systems the LO/VLO design is intended to defeat [Refer Table A.2].

Definitions of these and other terms employed in this document are summarised in Annex C. Reference data for RCS scales, radio-frequency bands, engagement geometries are summarised in Annex A. A summary of representative threat systems is available in Annex A, in an earlier publication3.

The T-50 was developed specifically to compete against the F-22 Raptor in traditional Beyond Visual Range (BVR) and Within Visual Range (WVR) air combat. As a result, the T-50 shares all of the cardinal "fifth generation" attributes until now unique to the F-22 - stealth, supersonic cruise, thrust vectoring, highly integrated avionics and a powerful suite of active and passive sensors.

The PAK-FA therefore firmly qualifies as a "fifth generation" design. In addition, it has two further attributes not introduced in the F-22 design. The first is "extreme plus agility"2, resulting from advanced aerodynamic design, exceptional thrust/weight ratio performance and three dimensional thrust vectoring integrated with an advanced digital flight control system. The second attribute is exceptional combat persistence, the result of an unusually large 25,000 lb internal fuel load. The former entailed some shaping compromises, at the expense of specular RCS performance.

The basic shaping design observed on prototypes of the PAK-FA will deny it the critical all-aspect stealth performance of the F-22, critical in BVR air combat and deep penetration operations. Despite this, the extreme manoeuvrability/controllability design features of the PAK-FA, which result in extreme plus agility, result in the potential for the PAK-FA to become the most lethal and survivable fighter ever built for air combat engagements.

The publicly displayed PAK-FA prototypes do not represent a production configuration of the aircraft, which is to employ a new engine design, and extensive VLO treatments which are not required on a prototype.

This assessment, like the earlier assessment performed on the J-20 design, cannot be more than preliminary for a number of important reasons:
The final airframe shaping remains unknown, and changes may arise through the development cycle, to improve aerodynamic performance, operational characteristics, and LO/VLO performance;
The state of Russian Radar Absorbent Materials (RAM), Radar Absorbent Structures (RAS) and radar absorbent coatings technology is not well understood in the West;
The state of Russian technologies for sensor aperture (radar, EO, passive RF) structural mode RCS reduction is not well understood in the West;
The state of Russian technologies for RCS flare spot reduction, in areas such as navigation/communications antennas, seals, panel joins, drain apertures, cooling vents, and fasteners is not well understood in the West.
Achievement of credible LO or VLO performance is the result of a design having intended RCS characteristics in all of these categories4.

Proper airframe shaping, as stated in Denys Overholser's famous dictum, is a necessary and essential prerequisite for good LO or VLO performance. If shaping design is deficient, no amount of credible materials application and detail flare spot reduction can overcome the RCS contributions produced by the airframe shape, and genuine VLO performance will be therefore unattainable. While this is self-evident, it is often not well appreciated.

If airframe shaping is credible, then careful and well considered application of Radar Absorbent Materials (RAM), Radar Absorbent Structures (RAS), radar absorbent coatings, aperture RCS reductions, and minor flare spot reduction techniques will yield a VLO design.

Modelling of the shape related RCS contributions of any VLO design is of very high value, as it determines not only whether the aircraft can achieve credible VLO category performance, but also where the designers will be investing effort in RAS, RAM and coating application to achieve this effect. Moreover, it exposes the angular extents within which the aircraft has poor RCS performance, and thus provides a robust basis for development of tactics and technique to defeat the design.

This paper will focus mostly on shape related RCS contributions, both due to the high value of knowing weaknesses in the design, but also due to the uncertainties inherent in estimating the performance of unknown technologies for RAS, RAM, coatings, aperture RCS reductions, and minor flare spot reduction. Where applicable, reasonable assumptions will be made as to the performance of absorbent material related RCS reduction measures.

T-50 Prototype Very Low Observable Airframe Shaping Design Features

Figure 1. The lower fuselage of the prototype displays interesting incongruities. There is an abrupt transition between the carefully sculpted faceting of the inlet nacelles, and the smoothly curved aft engine nacelles and conventional aft fuselage. The faceting strategy is similar to the F-22 design rules, with singly or doubly curved transitions between planes (C. Kopp/Sukhoi image)2.

An extensive qualitative analysis of RCS reduction shaping feature design in the T-50 aircraft was performed in 2010. That analysis yielded the following observations, cited here for convenience2:

1.The forward fuselage is closest in general configuration to the YF-23, especially in the chining, cockpit placement, and hump aft of the cockpit canopy, although the blending of the upper forward fuselage into the upper carapace is more gradual.

2.There are important differences from the YF-23. The chine curvature design rule is purely convex, like the chine design on the F-22A. The nose height is greater, to accommodate an AESA with a much larger aperture than that intended for the YF-23 or F-22A.

3.If flare spots are properly controlled by the application of materials and serrated edge treatments around the canopy, and a good bandpass radome design using a frequency selective multilayer laminate is employed, the shaping related RCS contribution of the forward fuselage in the S/X/Ku-bands will be similar to that observed with the F-22A, YF-23 or F-35.

4.The edge aligned movable LEX are readily treated with leading edge absorbers and will not present a major RCS flare spot. The treatment of the movable join will present the principal challenge in this portion of the design. The obtuse angle in the join between the LEX and forward fuselage is characteristic of good design and is very similar to the angles used in the F-22.

5.The edge aligned trapezoidal main engine inlets are similar in configuration to the F-22, but with important differences. The inlet aspect ratio is different, and the corners are truncated in a manner similar to the YF-23. If properly treated with leading edge inserts and inlet tunnel absorbent materials, the inlet design should yield similar RCS to its US counterparts.

6.The placement of the engine centrelines well above the inlet centroids, in the manner of the YF-23, results in an inlet tunnel S-bend in the vertical plane. Sukhoi have not disclosed whether an inlet blocker will be employed. The use of an S-bend in the PAK-FA would permit an increase in the number of surface bounces further increasing attenuation and reducing RCS.

7.In the S/X/Ku-bands the basic shaping of the forward fuselage will permit the attainment of genuine VLO performance with the application of mature RAS and RAM, where the centre and aft fuselage do not introduce larger RCS contributions from the forward aspect.

8.The wing design from a planform perspective is closest to the F-22A, and the upper fuselage similar to the YF-23, permitting the achievement of similar RCS performance to these US types, from respective aspects.

9.Where the PAK-FA falls well short of the F-22A and YF-23 is the shaping design of the lower fuselage and side fuselage, where the general configuration, wing/fuselage join angles, and inlet/engine nacelle join angles introduce similar intractable specular return problems as observed with the F-35 Joint Strike Fighter design. These are inherent in the current shaping design and cannot be significantly improved by materials application. .... the PAK-FA prototype design will produce a large specular return in any manoeuvre where the lower fuselage is exposed to a threat emitter, and this problem will be prominent from the Ku-band down to the L-band.

10.This problem is exacerbated by the inboard ventral wing root fairings, claimed by some Russian sources to be pods for the concealed carriage of folding fin close combat AAMs, such as the RVV-MD/R-74 series. While these fairings do not introduce large RCS contributions from fore or aft aspects, they will adversely contribute to beam aspect RCS, especially for threats well below the plane of flight of the aircraft.

11.The tailboom shaping is reminiscent of the F-22 and F-35 designs, and will not yield significant RCS contributions from the front or aft aspects.

12.In the lower hemisphere, it will suffer penalties due to the insufficiently obtuse join angles between the wings and stabilators, and outer engine nacelles.

13.The upper fuselage fairings which house the all moving vertical tail actuators are well shaped, and the join angles are well chosen.

14.The outward cant of the empennage fins is similar to United States designs, and like the YF-23 tail surfaces, these are fully articulated with the VLO benefit of removing surface impedance discontinuities at the join of a conventional rudder control surface.

15.The axi-symmetric 3D TVC nozzles present the same RCS problems observed with the fixed axi-symmetric nozzles used in the F-35 JSF, and the application of serrated shroud treatments and tailpipe blockers as used with the F-35 JSF will not overcome the inherent limitations of this canonical shaping design. Observed from the aft hemisphere in the L-band through Ku-bands, the PAK-FA prototype configuration will produce to an order of magnitude an equally poor RCS as the F-35 Joint Strike Fighter5.

16.The centre fuselage beavertail follows a similar chine design rule as the forward fuselage does, and will not present a significant RCS contribution from behind.

These observations reflected the design of the first prototype. Subsequent prototypes, publicly displayed, do not fundamentally differ in any of these design features.

The qualitative analysis yielded the conclusion that with proper application of materials technology, detail feature RCS reduction treatments, aperture structural mode RCS reduction measures, the T-50 had potential to yield viable VLO performance in the forward sector, and with a nozzle design similar to the F-22A, had potential for viable VLO performance in the aft sector. Performance in the beam sector and lower hemsiphere were identified as problematic. This conclusion was a result of several specific shaping features, specifically the lower fuselage tunnel design, and the absence of obtuse angle joins between the aft fuselage sides and wing / stabilator joins, and the obtuse join angles in the fuselage tunnel.

Quantitative RCS modelling will demonstrate that these observations were valid.



Conclusions

This study has explored the specular Radar Cross Section of the Sukhoi T-50 prototype aircraft shaping design. Simulations using a Physical Optics simulation algorithm were performed for frequencies of 150 MHz, 600 MHz, 1.2 GHz, 3.0 GHz, 6.0 GHz, 8.0 GHz, 12.0 GHz, 16.0 GHz and 28 GHz without an absorbent coating, and for frequencies of 1.2 GHz, 3.0 GHz, 6.0 GHz, 8.0 GHz, 12.0 GHz, 16.0 GHz with an absorbent coating, covering all angular aspects of the airframe.

If the production T-50 retains the axisymmetric nozzles and extant ventral fuselage design, the aircraft would still deliver robust Very Low Observable performance in the nose aspect angular sector, providing that effective RCS treatments are applied to suppress surface travelling waves, inlet and edge reflections.

If the production T-50 introduces a rectangular faceted nozzle design, and refinements to lower fuselage and side shaping, the design would present very good potential for good Very Low Observable performance in the S-band and above, for the nose and tail aspect angular sectors, with reasonable performance in the beam aspect angular sector. The extent to which this potential could be exploited would depend critically on the design of the nozzles and other shaping refinements.

In conclusion, this study has established through Physical Optics simulation across nine frequency bands, that no fundamental obstacles exist in the shaping design of the T-50 prototype, which might preclude its development into a genuine Very Low Observable design with constrained angular coverage.

IMAGE GALLERY

Figure 3. The T-50 has five major lobes in the left and right beam aspect angular sectors, for convenience labelled A through E, with the flat lower fuselage mainlobe labelled F (KnAAPO image).

Figure 4. Mapping of the five major lobes in the left and right beam aspect angular sectors at 16 GHz (KnAAPO image).

Figure 5. The T-50 from behind, showing the corner joins in the inlet tunnel, and fuselage sides (KnAAPO image).




SOURCE:
A Preliminary Assessment of Specular Radar Cross Section Performance in the Sukhoi T-50 Prototype

9.Where the PAK-FA falls well short of the F-22A and YF-23 is the shaping design of the lower fuselage and side fuselage, where the general configuration, wing/fuselage join angles, and inlet/engine nacelle join angles introduce similar intractable specular return problems as observed with the F-35 Joint Strike Fighter design. These are inherent in the current shaping design and cannot be significantly improved by materials application. .... the PAK-FA prototype design will produce a large specular return in any manoeuvre where the lower fuselage is exposed to a threat emitter, and this problem will be prominent from the Ku-band down to the L-band.

10.This problem is exacerbated by the inboard ventral wing root fairings, claimed by some Russian sources to be pods for the concealed carriage of folding fin close combat AAMs, such as the RVV-MD/R-74 series. While these fairings do not introduce large RCS contributions from fore or aft aspects, they will adversely contribute to beam aspect RCS, especially for threats well below the plane of flight of the aircraft.

I do hope the above two points are rectified with stealth compliant shaping in indian FGFA.otherwise pakfa will remain just a sukhoi adapted to stealth 5th gen shaping with internal bomb bay and not a new design,which is a sloppy approach of the russians.

Even the chinese have come up with better shaping in j-20.But they fouled up witth introducing canards.

I wonder why did the IAF kept quiet about it?we are sinking close to 20 billions in this fighter, surely they could have asked russians earlier.

.Sure they could easily have addressed the above two points 9 and 10 and easily put serpentine intake if they wished.But they didn't do it.

 

[ersakthivel]

Air Combat: Russia's PAK-FA versus the F-22 and F-35
QWIP based IRST sensors will provide detect and track solutions to FGFA's BVrs opposed to superior radar stealth F-22 according to the link

 

[average american]

Air Power Australia, Flanker Analysis Examined

Unless you have stumbled across this blog by complete accident and are looking for financialcommentary or a V8 page you've probably heard of Dr Carlo Kopp. Indeed he is perhaps themost famous, or infamous, analyst within the wider Australian defence community. The "goodDr" contributes to many respectable publications such as Defence Today Magazine on aregular basis, and often reports on a number of defence related issues which are in myopinion usually genuine and thoughtful articles. However his rather uncontroversial additionsto various defence media are probably not the reason why you have heard of Dr Kopp. Hismost controversial articles and analysis all stem from the debate over the RAAF's choice of combat aircraft and its viability when facing advanced Russian Flanker derivatives. Hiswebsite "Air Power Australia" has flooded the internet with articles which invariably end withthe conclusion on the outright inferiority of all western alternatives apart from the F-22A when facing the Super Flanker threat.While the government went about considering tenders for an eventual replacement of theF/A-18C/D's and F-111 fleet Dr Kopp and other associates (a Mr Goon included) lodged asubmission to the DoD. Under Kopp's plan the RAAF would acquire ~50 F-22A's and retain 24 'upgraded' F-111S's. When this option was not chosen by the RAAF (the F-35 was chosenand then the F/A-18F as an interim solution) the Dr launched his PR campaign, arguing thatonly the F-22A could provide the RAAF with the necessary level of air dominance when facingthe advanced Flanker threat. Soon the internet was flooded by APA PDF's and his variouspages on the APA site with long and seemingly comprehensive arguments illustrating the diremistake the RAAF had made, and the inferiority of the chosen designs. To the layman (oreven someone with a casual interest in air power) his arguments are very persuasive; indeeda younger, more impressionable Ozzy was swayed by the doctor's conviction and apparenttechnical mastery. Debates on many forums included Kopp's arguments, many of which hadapparently not appeared before, it seemed that this Australian defence journalist hadswayed thousands all over the world to his view of the contemporary battle space.However after time, careful thought, significant discussion and a good dose of listening,reading and learning a slightly older, more sceptical Ozzy began to question the "good Dr's" arguments and conclusions. Indeed it soon became apparent that Carlo Kopp's work oncontemporary air combat is, for the most part, an exercise in lobbying. After closeexamination it's apparent that the vast majority of Dr Kopp's arguments are based onmistruths, bogus analysis and conclusions drawn after only examining beneficialconsiderations. Below is the first section of a PDF authored by Dr Kopp available at hiswebsite, It is in many ways a typical piece of Kopp's work which is why I decided to criticallyexamine it. There was more to the piece but I could have gone on for ever; this two pagearticle exemplifies Kopp's major arguments and clearly illustrates the tactics and devices heuses to put together a persuasive and seemingly sound argument. Below I have outlined 16major misrepresentations of fact, omissions, oversimplifications and deliberately partialanalysis Kopp made on this 2 page journey in order to arrive at the damning conclusion thatthe F-35A or F/A-18F could at best, only hope to achieve parity when facing an advancedFlanker threat.

Air Power Australia, Flanker Analysis Examined - Rebuttal to Kopp at Ozzy Blizzard's Australian Defence Times

 

[p2prada]

Carlo Kopp's articles are good as long as you are not reading his articles on stealth.

That Physical Optics solution is utter crap.

Some of his F-35 assertions are bogus as well. He downplays significant superior aspects of the F-35 and focuses only on the negative aspects. In a way he is not lying, but he is not being completely honest.

 

[average american]

I would guess the "maneuverability" part is a marketing pitch for easy to impress buyers. What's that pilot axiom, "he who sees their enemy first wins the fight" which leads to stealth and superior electronics as the critical component over maneuverability. At some point maneuverability reaches a limit defined by the g's the pilot can handle and the higher the speed, the less maneuvering that can be done anyway. So, it sounds like the Russians(and Chinese for the J-20) are polishing a turd for sale to their allies.

 

[p2prada]

The Russians are replacing all of their aircraft with PAKFA. In the case of India, PAKFA will be only one among 5 or 6 of aircraft.

The J-20 is PLAAF specific. Not for export.

Even though the F-22 is such a superior plane, they made it so superior that even the US cannot afford it. Due to that, they have ended up opting for an aircraft which may eventually be less capable than the PAKFA or even the J-20. So this is where the PAKFA will triumph, in its ability to exceed all of F-35s performance and electronics capability while being cheap enough to be exported and pose a significant threat to the F-35.

Maneuverability is a very important criteria even for the US. The USAF would not have chosen the smaller, less stealthy and more maneuverable F-22 over the larger, more stealthy and less maneuverable YF-23. Larger means more of those superior electronics.

 

[JineshJK]

I wonder what makes F-22 superior in all field for some of you!! and J-20 as a serious aircraft!! curious... expect genuine answers.
Even F-22 WVR combat capabilities are inferior to current USAF jets.(they dont celebrate for that).
It is the US and their technology, we always get 100% exaggerations from every single media available.

they made it so superior that even the US cannot afford it. Due to that, they have ended up opting for an aircraft which may eventually be less capable than the PAKFA or even the J-20.

Can you pls explain more... cause I heard only about some Electronic warfare suite modification or strip out. The stealth effectiveness of F-22 no idea..RCS claims varies from 0.1 to 0.0001!!!! Cockpit oxygen generating system problem not yet fixed(even after the accident).
I dont have any idea, please clear my doubts or share yours..

 

[p2prada]

I wonder what makes F-22 superior in all field for some of you!! and J-20 as a serious aircraft!! curious...

F-22 is the best, there is no doubt about it. It has been nearly a decade and hence is a little older and has some crucial electronics missing.

If the J-20 combines a Flanker with a very low RCS, it is already superior to many other aircraft.

Even F-22 WVR combat capabilities are inferior to current USAF jets.(they dont celebrate for that).

Nonsense. There is not a single American aircraft which is claimed to have superior performance.

The F-22 has twice the range of a loaded F-15 when using intermediate thrust and exponentially more range when at Mach 1.6. Better turn rates, climb rates and acceleration to boot.

It is the US and their technology, we always get 100% exaggerations from every single media available.

Deal with it. They are not exaggerated.

Can you pls explain more... cause I heard only about some Electronic warfare suite modification or strip out.

For one, PAKFA will have a bigger nose cone radar than F-35, 900-950mm(?) vs 800mm. Apart from that PAKFA will have EF-2000 type radars all over the place. Two on the sides and one in the back. So one large dia radar and 3 medium sized radars. That's quite a lot. Apart from that PAKFA's maneuverability and performance should far exceed F-35s, along with range and endurance. So more advantages all the way.

The stealth effectiveness of F-22 no idea..RCS claims varies from 0.1 to 0.0001!!!!

RCS claim is confirmed to be 0.0001 or more accurately -40dBsm. It was released by USAF.

Cockpit oxygen generating system problem not yet fixed(even after the accident).
I dont have any idea, please clear my doubts or share yours..

It wasn't a problem with the aircraft, it was a problem with the G-suit. It was strangling pilots. So they changed it.

 

[average american]

As as of 2009 and later Russian BVR missiles did not work half the time 50 percent, so the Russian emphised maneuverability to compensate. Its not that Russian BVR missiles missed 50 percent of the time, it was they did not even launch from the plane and when they did they went in an entirely differant direction. They problems Russia has they dont have much of an electronics industry and what they do have has poor quality control. I have never ever heard of an an Russian electronic product.

 

[SATISH]

As as of 2009 and later Russian BVR missiles did not work half the time 50 percent, so the Russian emphised maneuverability to compensate. Its not that Russian BVR missiles missed 50 percent of the time, it was they did not even launch from the plane and when they did they went in an entirely differant direction. They problems Russia has they dont have much of an electronics industry and what they do have has poor quality control. I have never ever heard of an an Russian electronic product.

Would you mind giving us a proof of the above claim you made?

 

[average american]

Would you mind giving us a proof of the above claim you made?

New Delhi: Nearly half of Indian Air Force's beyond visual range (BVR) air-to-air missiles that were tested either did not home in on targets during evaluations or failed ground tests because they were ageing much before their shelf lives, a report claimed on Thursday.

As per the report by an leading English daily, the Comptroller and Auditor General (CAG) in its yet to be released report has raised serious questions on the usability of the R 77 (RVV-AE) BVR missiles, each costing Rs 2 crore, which are fitted on board the Su-30 MKIs, MiG-29s and MiG-21 Bisons.

India has been procuring these missiles from Russia since 1996 and has even ordered for more than 2,000 missiles after the Kargil conflict out of which 1,000 have already been delivered.

The missiles failure has affected the "operational preparedness" of the IAF, the daily said quoting CAG report.

Moreover, just yesterday Defence Minister A K Antony had disclosed that there were structural problems with India's lead fighter planes, the MiG-29.

IAF's air-to-air missiles are faulty: Report

Of course perhaps is just happening to the missiles Russia is selling India, but then if thats the case it just makes the matter worse but I expect it applies to all Russian Missiles.

 

[SATISH]

New Delhi: Nearly half of Indian Air Force's beyond visual range (BVR) air-to-air missiles that were tested either did not home in on targets during evaluations or failed ground tests because they were ageing much before their shelf lives, a report claimed on Thursday.

As per the report by an leading English daily, the Comptroller and Auditor General (CAG) in its yet to be released report has raised serious questions on the usability of the R 77 (RVV-AE) BVR missiles, each costing Rs 2 crore, which are fitted on board the Su-30 MKIs, MiG-29s and MiG-21 Bisons.

India has been procuring these missiles from Russia since 1996 and has even ordered for more than 2,000 missiles after the Kargil conflict out of which 1,000 have already been delivered.

The missiles failure has affected the "operational preparedness" of the IAF, the daily said quoting CAG report.

Moreover, just yesterday Defence Minister A K Antony had disclosed that there were structural problems with India's lead fighter planes, the MiG-29.

IAF's air-to-air missiles are faulty: Report

Of course perhaps is just happening to the missiles Russia is selling India, but then if thats the case it just makes the matter worse but I expect it applies to all Russian Missiles.

Did you even bother to read the whole report?

 

[JineshJK]

F-22 is the best, there is no doubt about it.

No I doubt on that..
An aircraft which failed to prove its reliability because of high maintenance cost, Lot of technical problems like - RAM coating, Oxygen Generator Problem, Over heating Avionics, navigation problem, etc.

John Young -Undersecretary of Defense(Acquisition, Technology and Logistics) about F-22 program..
"still does not meet most of its KPPs (Key Performance Parameters)." But it's not just pure operational shortcomings that have Young worried. "The airplane is proving very expensive to operate.. and it is complex to maintain."
the F-22 program is "struggling" with its low observable capabilities and "other issues."

Project cost spent- US$66 billion, and stopped at 187 units.
Darrol Olsen a former Lockheed chemical Engineer claimed that the RAM coatings are defective and not up to its specifications. It was rain vulnerable and frequent patch up needed to cover the weapon-ECM door bays.
The RAM coatings on F-22 is one of the main reason for its huge maintenance cost. Required 3hour mean time flight hour before maintenance reduced to less than 1hour.
AF Identified Structural cracks in the aft boob titanium casting, forced to modify 78 units. More than 10 years of development this is the result!!
Over heating Avionics, navigation problem, communication problem with legacy jets.
If all these problems were in development phase or after 1-2 years of service, then its Ok for a new generation new kind of fighter. But the Oxygen problem not yet fixed, even with limited flying hours, experienced pilots suffered hypoxia, memory loss, decreased level of alertness, chronic cough,etc. like health problem, how it is possible for a pilot to take critical decision or perform high g-maneuver under his worst brain condition.
I know there is always an explanation for almost all those issues, "All the problems.. Fixed, it was in 2008-2009 or 2011-2012" may be.

There is not a single American aircraft which is claimed

The F-22 has twice the range of a loaded F-15 when using intermediate thrust and exponentially more range when at Mach 1.6. Better turn rates, climb rates and acceleration to boot.

Yes it is, but not superior in the world.
F-22 have good high speed-altitude maneuvering capability, but in low speed-altitude not that good..

According to 'The Heritage Foundation', every VHF radar in the world can detect F-22 at 150-200 miles.
"The F-22's "supercruise",that is, its ability to cruise supersonically, is unusably short in duration (due to inadequate onboard
fuel capacity)—so short that current Air Force training missions to exercise supercruising combat actually schedule one tanker refueling just before
going supersonic and one more refueling before going home subsonically. Imagine having to schedule two tanker hook-ups for every F-22 sortie in the
chaos of a serious shooting war!" - The Heritage Foundation, Then and Now

F-22 shot down by German EF in mock close combat.
Famous F-18 HUD image, locking F-22 in mock close combat.
If F-18 can do that, I would say, Mig-21 is enough!. F-22 cant perform high alpha maneuver comparable to Mig-29 or Su-27 series, thats for sure.
Comparatively PAKFA aerodynamics lead in agility and low speed maneuvering with more control surface than F-22(yeah its sukhoi..), and 3D TVC.
And without HMS,IRST and High off-bore missile, how F-22 will outmaneuver or defeat enemy aircraft in WVR combat?!!
Also in BVR AESA radars need to use frequencies that compromise their stealth and position,
From Wiki F-22 combat Radius is 759km and F-15-1967km.

It wasn't a problem with the aircraft, it was a problem with the G-suit. It was strangling pilots. So they changed it.

$66 billion project and never ending G-suit problem?!, 'strangling G-suit' came from one crash investigation report, but still LM struggling to fix the oxygen generator problem or covering something. In addition, 'faulty valve in the pilots' pressure vest' and Oxygen concentration problem. The investigation report concluded as pilot error!!

So in my opinion F-22 is nothing but an impractical unreliable 5th gen aircraft failed to meet most of the AF requirements.
Of course its configuration is capable and competent in many fields like in Engine, BVR combat, ECM, Radar, Avionics, VLO design, etc but it is fragile, lacks reliability, even minor body damages are hard to afford, uncomfortable for pilots, reduced average flight hours, technical problems due to design flaws...
America with a mammoth defense budget struggling to maintain this fighter financially and technically!!... then is it worthy?

 

[average american]

maneuvering capability is just a turd the Russians keep polishing because they dont have stealth or reliable BVR air to air missiles. If their air to air missiles are not even 50 percent reliable then you can bet their SAM 500 is no better. The best radar that as Russian plane has wont be able to detect an F22 outside 15 miles, well with in the range of even the F22 and F35 medium range missiles. The first time Russian planes come up against american planes its going to be just as embarassing as it has been in the past. The best weapons, pliots and stratgy the USA has not been able to shoot the f22 down, even when its badly outnumbered.

 

[average american]

HISTORY CHANNEL- DOGFIGHT FUTURE FIGHTER JETS.flv - YouTube

 

[average american]

Meet Miss February Lockheed Martin's first 6th gen fighter concept "Miss February". - YouTube

 

[sayareakd]

maneuvering capability is just a turd the Russians keep polishing because they dont have stealth or reliable BVR air to air missiles. If their air to air missiles are not even 50 percent reliable then you can bet their SAM 500 is no better. The best radar that as Russian plane has wont be able to detect an F22 outside 15 miles, well with in the range of even the F22 and F35 medium range missiles. The first time Russian planes come up against american planes its going to be just as embarassing as it has been in the past. The best weapons, pliots and stratgy the USA has not been able to shoot the f22 down, even when its badly outnumbered.

AA, in Sarbia war, Russian Pechora SAM which is outdated system took out F117, which is most update stealth aircraft of the time and it was major major embarrassment for stealth fighter which is supposed to invisible to radar, was shot out of the sky.

in case if you ever go to Belgrade, then go to Museum of Aviation and please check up this display

 

[average american]

F117 is old technology, and shooting down one plane does not mean much if anything, stealth planes have flowen tens of thousands of mission and this is the only time one has been shot down. Seems to me flying tens of thousands of missions in to the most heavly defend space in the world and only one loss proves stealth is worth any price that has to be paid.