Combat Aircraft technology and Evolution

AnantS

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Np, I see 4 Helicopter - Turbine Engines and 3 Turboprop engines? Is that correct guess?
 

gadeshi

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Np, I see 4 Helicopter - Turbine Engines and 3 Turboprop engines? Is that correct guess?
Almost :)
4 helicopter and 3 shipborn turbines.

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asianobserve

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Adaptive cycle engine enters final phase of development

The US Air Force has awarded two five-year development contracts to GE Aviation and Pratt & Whitney worth up to $1 billion each to continue development of a next-generation military jet engine and prepare for an anticipated competition in the early 2020s for the chance to power a new combat aircraft and possibly re-engine the Lockheed Martin F-35.

The awards of the Adaptive Engine Transition Programme (AETP) contracts to GE and P&W on 30 June extends a nearly 10-year effort to introduce a fuel-saving cruise mode into an engine intended for a supersonic fighter. Both contractors will develop and test multiple new centreline engines sized at a 45,000lb-thrust level.

“We believe GE is best positioned to integrate the adaptive suite of technologies into existing and next-generation combat aircraft,” says Dan McCormick, general manager of GE Aviation's Advanced Combat Engine programmes.

P&W senior director of advanced programmes and technology Jimmy Kenyon says the company can leverage experience as the propulsion supplier for the F-22 and F-35 to "provided a highly capable adaptive engine with the ability to power a wide range of future and legacy aircraft applications".

The USAF is developing concepts for replacing the Lockheed F-22 after 2030, which includes updating existing designs with new technology. Re-engining the F-35 with an adaptive cycle, 45,000lb-thrust engine is also under study.

An adaptive-cycle engine is intended to address a design limitation in modern powerplants. An engine optimised for subsonic speed is more fuel-efficient, but cannot easily exceed the speed of sound. A supersonic engine, however, can accelerate over Mach 1.0 but is limited in range because it guzzles fuel.

The AETP programme continues development of a technology that could make supersonic engines 25% more fuel-efficient, thus extending the range of a fighter by as much as 30%, according to GE.

There are two kinds of airflow in modern engines. One airflow enters the engine core, mixes with fuel, combusts and generates energy to power the gas turbine machinery and create thrust. Another portion of the airflow enters the inlet and then bypasses the core, generating thrust without the need to consume any fuel directly. An adaptive cycle engine proposes to add a secondary stream of bypass airflow in cruise speed conditions. This secondary duct can be shut off when it’s necessary to accelerate rapidly.

The USAF launched the technology development programme in 2007 with adaptive versatile engine technology programme with GE. P&W and GE then participated in the adaptive engine technology demonstration (AETD) programme that began in 2012. AETD is expected to end later this year.

https://www.flightglobal.com/news/a...engine-enters-final-phase-of-developm-426886/



 
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asianobserve

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Measuring Stealth Technology's Performance

How low-observable technology enhances aircraft survivability
Jun 28, 2016
Dan Katz | Aviation Week & Space Technology

For the non-U.S. nations buying the Joint Strike Fighter, Lockheed Martin’s F-35 will be their first experience operating stealth aircraft. Since development of the aircraft began 15 years ago, radar technology has advanced and debate over the value of stealth has escalated. But several nations have now selected the F-35 in open competitions, citing in part the combat capability enabled by low observability. As the F-35 debuts at air shows outside the U.S., Aviation Week reexamines the fundamentals of stealth and whether it provides an advantage over the latest adversary radars.

Stealth Basics

Stealth is the science of reducing an object’s detectability to radar. The goal is to minimize the electromagnetic energy reflected back to a radar so it cannot distinguish the return from the signals created by environmental clutter and noise of its internal electronics.

Large “fourth-generation” fighters such as the F-15, Su-27 and Tornado have radar cross-sections (RCS) of 10-15 m2. The F-16 and “Gen-4.5” fighters—Typhoon, Rafale, Su-35 and Super Hornet—are believed to be in the 1-3-m2 range. The F-35 and F-22 RCSs are said to equal a golf ball and marble, respectively. Based on Sukhoi’s claims that its Su-35 can detect 3-m2 targets at 400 km in a narrow-angle, maximum-power search, Aviation Week estimated how far away it can detect these fighters. Note the detection range in a standard search is half as much. Credit: Colin Throm/AW&ST

The metric of detectability is called radar cross-section (RCS), which normalizes the reflectivity of targets by comparing them to metal spheres. Human beings have an RCS of about 1 m2— they return as much radar energy as a sphere with a geometric cross-section of 1 m2. Since RCSs vary by orders of magnitude, it also is common to use the logarithmic unit “decibel square meters” (dBsm), in which 100 m2 converts to 20 dBsm and 0.1 m2 to -10 dBsm.

RCS varies with the angle and frequency of the radar signal. The sector of greatest interest is ±45 deg. in azimuth and ±15 deg. in elevation, and the frequency band of greatest concern is X-band (8-12 GHz), where most fire-control radars operate. “All-aspect stealth”—minimizing detectability from any angle—and “broadband stealth”—reducing observability over a broader frequency range—can be achieved with greater cost or engineering tradeoffs.

Stealth technology reduces RCS by shaping an aircraft to “scatter” radar waves away from the emitter and using radar-absorbent material (RAM) to reduce reflections by turning the energy into heat. Traditionally, shaping accounts for 90% of stealth’s RCS reduction and materials 10%.

Shaping starts with a focus on “specular” scattering, in which waves bounce off a structure like billiard balls. Flat surfaces reflect most energy at an angle equal to the incident wave and are therefore preferred and oriented to minimize returns to the radar.

Engine intakes, cockpits, 90-deg. corners and other “multiple-bounce structures” reflect the most incoming energy back to their sources. Right angles are avoided entirely. Cockpit canopies are “metallized” with a few nanometers of gold or indium tin oxide to make them reflect radar energy. Engine fan faces can be shielded from radar illumination by external screens (F-117 and RQ-170), internal blockers (F/A-18E/F) or serpentine-shaped inlets (B-2, F-22 and F-35), all of which incorporate RAM.

Weapons and other stores are carried internally. Missiles, bombs and fuel tanks increase RCS with their pylons, round bodies, cruciform tailfins and sensor apertures. They also create multiple-bounce geometries with the airframes, which can increase RCS.

This front view of the F-117 shows the screens covering the engine intakes. The screen blocks most radar waves and traps the rest inside. Note also the hexagonal auxiliary intakes with edges aligned with the main intakes and side of the fuselage and the sawtooth pattern surrounding the canopy. Credit: U.S. Air Force

Edges diffract radar energy in a narrow, fan-like pattern but still at an angle equal to the incoming wave, and wing and tail tips diffract waves in all directions. Both are kept narrow to minimize RCS, and edges are angled away from the direction of the threat.

Fuselage facets, control surfaces, leading and trailing edges, and gaps are oriented to concentrate reflections into a minimum number of angles. This “planform alignment” reduces detectability at every other angle. The surface is then covered with RAM, with special treatments for edges and tips.

When waves strike surfaces at grazing angles, they induce currents that travel until they hit a discontinuity, where they radiate waves and bounce back to radiate again. The longer they travel, the weaker they become, particularly if the surface contains RAM, but any discontinuity—an edge, gap or step in the surface, or a material change—reflects them. Gaps around access panels must be covered with conductive tapes or caulks to bridge any electromagnetic discontinuities. Access panels and doors that open in flight, such as those for landing gear and weapon bays, have edges angled to reflect traveling waves away from the threat sector, often creating a “sawtooth” appearance.

Estimating RCS

There are formulas to calculate the RCS of simple shapes and computer programs to estimate those of more complex structures, but due to the difficulty in accounting for nonspecular mechanisms, interaction among structures and RAM, it is better to rely on RCSs determined by testing. Those numbers, sometimes cloaked in terminology of objects, have been discussed publicly.

Almaz-Antey says the S-400’s 92N6E “Gravestone” fire-control radar can detect a 4-m2 radar-cross-section target at 250 km. Based on this figure, Aviation Week estimated its detection range against modern fighter aircraft. Credit: Colin Throm/AW&ST

Conventional aircraft of similar geometries and size tend to have similar RCSs. The Boeing F-15 has a frontal RCS of around 10 m2. The Sukhoi Su-27 RCS is also in the 10-15-m2 range and the Panavia Tornado is likely in this neighborhood as well. The figure is larger if external stores are carried. The initial Boeing F/A-18’s RCS is believed to be in the 10-m2 realm, but F/A-18C/Ds began incorporating RAM in 1989. The smaller Lockheed Martin F-16’s RCS is believed to be around 1-3 m2; the later C model is slightly stealthier than the F-16A, and signatures have also been reduced under Have Glass programs, which include application of RAM.

Later “Generation 4.5” fighters all employ RCS reduction to some extent. The Eurofighter Typhoon program sought to reduce RCS by a factor of four compared to Tornado. The Sukhoi Su-35 claims reduction of 5-6 times over the Su-27. This likely puts the Su-35, along with Dassault Rafale, in the 1-3-m2 range. The F/A-18E/F, which Boeing says employs the most extensive RCS-reduction measures of any nonstealth fighter, is reported at 0.66-1.26 m2.

While low observability is a spectrum and not a binary quality, “stealthy aircraft” usually implies an RCS of less than 1 m2. Russia’s new T-50 PAK FA is believed to be in the 0.1-1-m2 range. Cruise missiles come in at 0.1-0.2 m2. The F-117 was said to have an RCS equal to a small bird (0.01-001 m2). The F-35 RCS is compared to a “golf ball” and the F-22’s to “a marble”; these objects have RCS of 0.0013 m2 and 0.0002 m2, respectively.

Detectability vs. Radar

How does stealth affect survivability? Since radar waves expand spherically going to and returning from targets, the range at which an aircraft can be detected is proportional to the fourthroot of its RCS. Every tenfold reduction decreases detection range by 44%.

The most advanced Russian fire-control radars yet deployed are the Irbis-E on the Su-35 and the ground-based 92N6E Gravestone, part of the formidable S-400 surface-to-air missile (SAM) system. The manufacturers of the Su-35 and S-400 claim good performance against “stealthy” targets, but their own numbers do not substantiate this.

Sukhoi states the Su-35 can detect a 3-m2 target at 400 km (250 mi.). That is a good range against an F-16 or Typhoon, but it means this newest Flanker cannot detect an F-35 until it is within 36 mi., and inside 22 mi. for an F-22. And the U.S. fighters can launch their medium-range AIM-120 AMRAAMs from more than 60 mi. away. Also, that detection range is for a maximum-power, narrow-angle search. In conventional search mode, the detection range is half as much.

Almaz-Antey’s S-400 is feared for many reasons, including its longest-range (380-km) missile, but it cannot fire until its Gravestone radar has a target. According to the manufacturer, Gravestone detects a 4-m2 target at 250 km (155 mi.). Again, good against “reduced RCS” fighters, but the F-35 would not be seen until 21 mi. away and the F-22 13 mi. away. The U.S.’s internally carried Small Diameter Bombs can be dropped from more than 40 mi. away.

Much of the debate over the continued value of stealth has been generated by developments in lower-frequency radars (to be addressed in the next installment of this series), able to detect aircraft optimized for X-band stealth at longer range. But these are search radars that lack the resolution to provide targeting data. The S-400’s 91N6E “Big Bird” search radar can detect 1-m2 targets at 338 km (210 mi.), almost twice the range of the Gravestone, but its batteries cannot launch until the fire-control Gravestone has a target.

These figures are only estimates, but they are based on established formulas and public data from manufacturers and specialist engineers. The numbers convey the continuing advantage of stealth fighters, which can remain undetected until well within weapons range, even against top-end fire-control radars. These numbers suggest stealth remains a strong contributor to survivability against state-of-the-art weapon systems.
http://aviationweek.com/defense/measuring-stealth-technologys-performance
 
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gadeshi

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Article is a complete amatorish BS with wrong numbers for RCS and radar ranges both, especially for S-400.
S-400 can engage 3m2 aerodynamical targets on 400km while detecting them from 650km.
And why does author think that S-400 divizion does only have VVO radars and doesn't have Niebo-U 2m (M-Band) AESAs against which no stealth are effective?
Author does not count G4 fighters RCS with weapons on stores, and thus the numbers are wrong.
N-035 Irbis radar can detect F-22 from 90km (while its RCS estimates as 0,01m2, all the talks about marbles are advertisement BS).

Verdict: this is BS, you can dig it back :)

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gadeshi

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Russian NationalGuard (RosGuardia) tests combat deltaplane:
 

gadeshi

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Aircraft crews rescue systems evolution - a Zvezda film (in Russian):
 

StealthFlanker

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S-400 can engage 3m2 aerodynamical targets on 400km while detecting them from 650km.
No it cannot ,NIIIP 91N6E height is less than 15 meters , for target flying at 12 km ( common cruising altitude ) , the maximum radar horizon is about 460 km , your fire control radar wont see anything further than that regardless of how powerful it is ,and if by aerodynamical target you mean fighter aircraft then also no ,40N6 is not designed to attack agile target.

And why does author think that S-400 divizion does only have VVO radars and doesn't have Niebo-U 2m (M-Band) AESAs against which no stealth are effective?.
NEBO SVU work at VHF band not M band , and as explained before ,using low frequency radar doesnot mean stealth aircraft will suddenly have RCS of thousands square meters ,they will have bigger RCS because shaping become less effective due to increase in size of specular reflection lobes and increase in intensity of surface wave that will result in edge diffraction ( modern stealth design use blended facet to mitigate this problem )


But that doesnot mean you can render stealth characteristics completely useless

N-035 Irbis radar can detect F-22 from 90km (while its RCS estimates as 0,01m2, all the talks about marbles are advertisement BS)
And for what reason do you think the 0.001m2 value for F-22 , F-35 is BS ? there are loads of computer simulation show that radar scattering spike of F-35 , F-22 can be less than -20 dBsm ( 0.01m2) from frontal aspect , even without any RAM

and there are load of RAM that can absorb more than 20 dB around 8-12 Ghz too



Even if we concluded that Lockheed Martin lie about the RCS value of F-22 , F-35 while Sukhoi completely honest about Irbis-E performance , if Irbis-e can detect F-22/F-35 from 90 km ,it still worth noting that maximum detection range is taken in Velocity search look up ( when PRF is at maximum ) , to get a missiles firing solution aka range/velocity/heading/altitude you need unambiguous range measurements which mean no more than one pulse should be received from the target for each pulse transmitted by the radar. In most optimistic case you would get tracking range about 70% of maximum detection range , which is around 63 km in this case. Now throw in jamming which synergy much better with stealth aircraft over conventional aircraft due to jamming-signal ratio equation and Irbis-e would be lucky to be able to engage F-22 from further than 20 km


Now you may brought up HoJ , but there are many way to deal with it , terrance bounce jamming is an example
 
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gadeshi

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No it cannot ,NIIIP 91N6E height is less than 15 meters , for target flying at 12 km ( common cruising altitude ) , the maximum radar horizon is about 460 km , your fire control radar wont see anything further than that regardless of how powerful it is ,and if by aerodynamical target you mean fighter aircraft then also no ,40N6 is not designed to attack agile target.


NEBO SVU work at VHF band not M band , and as explained before ,using low frequency radar doesnot mean stealth aircraft will suddenly have RCS of thousands square meters ,they will have bigger RCS because shaping become less effective due to increase in size of specular reflection lobes and increase in intensity of surface wave that will result in edge diffraction ( modern stealth design use blended facet to mitigate this problem )


But that doesnot mean you can render stealth characteristics completely useless


And for what reason do you think the 0.001m2 value for F-22 , F-35 is BS ? there are loads of computer simulation show that radar scattering spike of F-35 , F-22 can be less than -20 dBsm ( 0.01m2) from frontal aspect , even without any RAM

and there are load of RAM that can absorb more than 20 dB around 8-12 Ghz too



Even if we concluded that Lockheed Martin lie about the RCS value of F-22 , F-35 while Sukhoi completely honest about Irbis-E performance , if Irbis-e can detect F-22/F-35 from 90 km ,it still worth noting that maximum detection range is taken in Velocity search look up ( when PRF is at maximum ) , to get a missiles firing solution aka range/velocity/heading/altitude you need unambiguous range measurements which mean no more than one pulse should be received from the target for each pulse transmitted by the radar. In most optimistic case you would get tracking range about 70% of maximum detection range , which is around 63 km in this case. Now throw in jamming which synergy much better with stealth aircraft over conventional aircraft due to jamming-signal ratio equation and Irbis-e would be lucky to be able to engage F-22 from further than 20 km


Now you may brought up HoJ , but there are many way to deal with it , terrance bounce jamming is an example
You can argue me, posting the same images in every post of every topic, but this data is official from Almaz-Antei.
Will you argue them?

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StealthFlanker

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You can argue me, posting the same images in every post of every topic, but this data is official from Almaz-Antei.
Will you argue them?
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If it is wrong then i still do , it doesn't matter if the data you get came directly from Almaz-Antei ( which i doubt , they do ) , they cannot and will not go against physic laws.By the way , why do you have no problem thinking the value published by LM is just marketing nonsense, but at the same time believe every single words came from Russian manufacturers ? bias much ?
 

gadeshi

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If it is wrong then i still do , it doesn't matter if the data you get came directly from Almaz-Antei ( which i doubt , they do ) , they cannot and will not go against physic laws.By the way , why do you have no problem thinking the value published by LM is just marketing nonsense, but at the same time believe every single words came from Russian manufacturers ? bias much ?
1 - If you have stuck with generally known engineering solution, use another. That way you will not violate physics laws but will use them for your goals. NIIP uses ionospheric reflection to make its radars have off-boresight capabilities.
2 - LM has been many times caught on let's say, hypertrophated advertisement which has not confirmed further while Russians just disclose data, good or bad whatever. It's because Russians do weapons for themselves for real war, while Americans do a merchandise for weapons market.

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IndianHawk

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1 -
2 - LM has been many times caught on let's say, hypertrophated advertisement which has not confirmed further while Russians just disclose data, good or bad whatever. It's because Russians do weapons for themselves for real war, while Americans do a merchandise for weapons market.

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Well America is not exporting F22 to anyone. And Russia is exporting S400.
But American marketing skills are superior that I will concede.
 

gadeshi

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Well America is not exporting F22 to anyone. And Russia is exporting S400.
But American marketing skills are superior that I will concede.
But Americans export F-35 :)
Russians export S-400 to closest allies only (later on will be wider) but it doesn't advertise it - just open data without kickoys to give the potential customers an ability to make a sane decision but without aggressive marketing - just take it or not.
 

IndianHawk

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But Americans export F-35 :)
Russians export S-400 to closest allies only (later on will be wider) but it doesn't advertise it - just open data without kickoys to give the potential customers an ability to make a sane decision but without aggressive marketing - just take it or not.
F35 is being co-developed it's primary buyers are making components and what not . It would be pretty difficult to lie about that one with so many stakeholders. Many faults are already in public debate.
 

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