TÓPICO OFICIAL DO FX-2: GRIPEN NG

[Túlio]

Ficou faltando a da F-414, que nem no Site da GE eu achei mais do que tu, ou seja, quase necas de dados...

[knigh7]

Essa é do meu livro

[knigh7]

O Governo Suíço foi um mais preciso ao divulgar o peso vazio do Rafale: 10.220kg

Segue os dados do caça, até como fonte de referência:

[knigh7]

Olha, nesse site o autor utilizou dados corretos oficiais (portanto tem uma certa credibilidade) na comparação das turbinas.

Aliás, ele é o PICARD dos fóruns estrangeiros. Os francófilos gostam demais dele. Ele é francês.

Vale a pena analisar:

https://defenseissues.net/2014/12/06/fi ... mparision/

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Fighter aircraft engine comparision
Posted by Picard578 on December 6, 2014

Introduction

This article will compare several engines used in modern fighter aircraft: EJ200 (Typhoon), M88 (Rafale B/C/M), RM-12 (Gripen A/B/C/D), F-135 (F-35A/B/C), F-119 (F-22A), F404-GE-402 (F-18C/D), F-414-400 (F-18E/F, Gripen E/F), AL-31F (Su-27, Su-30, J-11).

Thrust to drag

Since frontal area dominates drag, and engine frontal area dominates aircraft frontal area, thrust to drag ratio will take a form of thrust divided by the engine frontal area (inlet diameter used).

EJ200: 3.848 cm2, 90 kN, 23,13 N/cm2

M88-2: 3.805 cm2, 73,9 kN, 19,42 N/cm2

RM-12: 3.948 cm2, 80,5 kN, 20,39 N/cm2

F-135 (CTOL): 10.715 cm2, 191,35 kN, 17,86 N/cm2

F-135 (STOL): 10.715 cm2, 182,4 kN, 17,02 N/cm2

F-119: 6.136 cm2, 164,58 kN, 26,82 N/cm2

F404-GE-402: 3.959 cm2, 78,7 kN, 19,88 N/cm2

F-414-400: 4.745 cm2, 97,37 kN, 20,52 N/cm2

AL-31F: 6.433 cm2, 122,58 kN, 19,05 N/cm2

AL-41F: 6.433 cm2, 175 kN, 27,2 N/cm2

As it can be seen, EJ200 has the second best thrust-to-drag ratio after the F-119, while the F-135 has the lowest thrust-to-drag ratio. EJ230 has a ratio of 26,9 N/cm2, while the F-414EPE will have a ratio of 24,62 N/cm2. M-88ECO will have a ratio of 23,65 N/cm2.

(This is one of reasons why single engined fighters typically have better peformance than twin engined fighters despite lower thrust-to-weight ratio. Engine frontal area is one of major contributors to drag in all “normal” flight conditions. Taking two engines that use same technology and general design, frontal area – and drag – will increase with square of dimensions’ increase, while weight – and thus thrust – will increase with cube of dimensions’ increase. Engine that is 20% larger in all three dimensions will have 44% greater frontal area and 72,8% more weight and thrust – thus its thrust-to-drag ratio will be 20% greater than that of the smaller engine. If engines are of the same size and characteristics, then twin engined aircraft will be larger and have higher inertia and inferior transient performance. This of course assumes identical design goals and avaliable technology. For example, F-119 is 239% larger in volume than the EJ200, has 59% greater frontal area and 15% better thrust-to-drag ratio.).

NOTE: M88-2 has been tested at 18.700 lbf in 1990, which would give it 21,86 N/cm2.

Thrust to weight

Engine thrust to weight ratio is an important (though not the only) factor in determining aircraft’s thrust-to-weight ratios, just as engine’s thrust-to-drag ratio is an important factor in determining aircraft’s thrust-to-drag ratio.

EJ200: 2.180 lbs, 20.250 lbf, 9,17:1

M88-2: 1.977,5 lbs, 16.620 lbf, 8,40:1

RM-12: 2.326 lbs, 18.100 lbf, 7,78:1

F-135 (CTOL): 6.444 lbs, 43.000 lbf, 6,67:1

F-135 (STOL): 10.342 lbs, 41.000 lbf, 3.96:1

F-119: 3.900 lbs, 37.000 lbf, 9,49:1

F404-GE-402: 2.282 lbs, 17.700 lbf, 7,76:1

F414-400: 2.445 lbs, 21.890 lbf, 8,95:1

AL-31F: 3.460 lbs, 27.560 lbf, 7,97:1

AL-41F: 1.850 kg, 17.845 kgf, 9,65:1

EJ230 has a thrust-to-weight ratio of 10,60:1 and F-414EPE will have a thrust-to-weight ratio of 10,74:1. M-88ECO will have a ratio of 9,32:1.

NOTE: F-135 weights were provided by Bill Sweetman here (comments section), citing Erin Dick. They are also listed here.

NOTE 2: M88-2 has been tested at 18.700 lbf in 1990. This would give it a TWR of 9,17.

Fuel consumption

Fuel consumption depends on both thrust and thrust-specific fuel consumption. Since aircraft with higher TWR can reduce thrust and still match performance of lower-TWR aircraft, both thrust-specific and total fuel consumption, at dry thrust and afterburner, will be compared.

Dry thrust:

EJ200: 21-23 g/kN s, 60 kN = 4.536-4.968 kg/h

M88-2: 0,8 kg/daN h, 48,8 kN = 3.904 kg/h

RM-12: 23,9 g/kN s, 54 kN = 4.646 kg/h

F-135: 0,89 kg/daN h, 124,6 kN = 11.089 kg/h

F-119: N/A (est: 0,8 kg/daN h, 116 kN = 9.968 kg/h)

F404-GE-402: 82,6 kg/kN h = 4.039 kg/h

F414-400: 0,84 kg/daN h, 57,8 kN = 4.855 kg/h

AL-31F: 0,87 kg/kgf*h, 7.575 kgf (74,5 kN) = 6.590 kg/h

AL-41F: 19,18 g/kN s, 113,9 kN = 7.865 kg/h

EJ200 consumes 82,8 kg/kN h, M88-2 consumes 80 kg/kN h, RM-12 consumes 86 kg/kN h, F-119 consumes 80 kg/kN h, F404-GE-402 consumes 83 kg/kN h, and F414-400 consumes 84 kg/kN h. F-135 is not capable of supercruise, but for completeness’ sake it does consume 89 kg/kN h. AL-31 consumes 88,5 kg/kN h and AL-41 consumes 69 kg/kN h.

Afterburner:

EJ200: 47-49 g/kN s, 90 kN = 15.228-15.876 kg/h

M88-2: 1,7 kg/daN h, 73,9 kN = 12.563 kg/h

RM-12: 50,6 g/kN s, 80,5 kN = 14.664 kg/h

F-135: 1,92 kg/daN h, 191,35 kN = 36.739 kg/h

F-119: N/A (est: 1,85 kg/daN h, 164,58 kN = 30.447 kg/h)

F404-GE-402: 177,5 kg/kN h, 78,7 kN = 13.969 kg/h

F414-400: 1,85 kg/daN h, 97,9 kN = 18.112 kg/h

AL-31F: 1,92 kg/kgf*h, 12.501 kgf (122,58 kN) = 24.002 kg/h

AL-41F: 54,11 g/kN s, 175 kN = 34.089 kg/h

Neither EJ230 or M88ECO offer improved SFC over basic variants. F414EDE/EPE could reduce SFC to 0,81 kg/daN h and 1,78 kg/daN h, comparable to the M88.

In the afterburner, EJ200 consumes 169,2-176,4 kg/kN h, M88-2 consumes 170 kg/kN h, RM-12 consumes 182 kg/kN h, F-135 consumes 192 kg/kN h, F-119 consumes 185 kg/kN h, F404-GE-402 consumes 177,5 kg/kN h, F414-400 consumes 185 kg/kN h, AL-31 consumes 195,8 kg/kN h and AL-41F consumes 194,8 kg/kN h.

Overall, M88 is the most fuel-efficient engine, followed by the EJ200 and F119, though all are less fuel efficient than AL-41 at subsonic regime. AL-31 is the least fuel-efficient engine.

Bypass ratio

Main function of low bypass ratio is to enable the engine to achieve high thrust-to-weight and thrust-to-drag ratio at dry thrust; both these qualities are required for supercruise.

EJ200: 0,4:1

M88-2: 0,3:1

RM-12: 0,31:1

F-135: 0,57:1

F-119: 0,3:1

F404-GE-402: 0,34:1

F414-400: 0,25:1

AL-31F: 0,59:1

AL-41F: 0,59:1

M88-2 has, interestingly enough, lower bypass ratio than the EJ200, indicating greater focus on supersonic performance. F-135 is quite obviously optimized for subsonic/transonic performance, and combined with unaerodynamic airframe (too fat for proper area ruling) and engine’s own low thrust-to-drag ratio, it is unrealistic to expect the F-35 to achieve any kind of sustained supersonic cruise. AL-31 is also optimized for subsonic-supersonic performance, but is paired to the far superior airframe. F-414 is the closest to being a turbojet out of all engines listed.

Percentage of maximum thrust achievable on dry power:

EJ200: 67%

M88-2: 66%

RM-12: 67%

F-135: 65%

F-119: 70%

F404-GE-402: 62%

F414-400: 69%

AL-31F: 61%

AL-41F: 65%

F-119 is the best while most other engines trail very closely behind it. AL-31 is the worst, and the F404 is the second worst.

Mechanical reliability and maintainability

Mechanical reliability depends in part on mechanical complexity. While most engines use the same basic architecture, there are things they very clearly differ in.

EJ200 has 8 compressor and 2 turbine stages

M88 has 9 compressor and 2 turbine stages

RM-12 has 10 compressor and 2 turbine stages

F-135 has 9 compressor and 3 turbine stages

F-119 has 9 compressor and 2 turbine stages

F404-GE-402 has 10 compressor and 2 turbine stages

F414-400 has 10 compressor and 2 turbine stages

AL-31F has 13 compressor and 2 turbine stages

AL-41F has 13 compressor and 2 turbine stages

While this is a vast oversimplification, going by number of stages alone, EJ200 would be the most reliable and easiest to maintan, while AL-31 would be the least reliable. EJ200 also has the fewest 1st stage fan blades of any modern fighter aircraft engine. F-119 has an additional failure point in form of the thrust vectoring nozzle, and the F-135 variant used on the F-35B has two additional failure points – TVC nozzle and a lift fan, plus a third failure point in form of doors for the lift fan which techically are not part of the engine. In the F-135s case, several weight reduction measures also made it far more vulnerable to the combat damage.

Many of these engines also use modular design to simplify maintenance. Number of modules is as follows:

EJ200: 15

M88: 21

RM-12: 6

F-135: 5

F-119: 4

F404-GE-402: 6

F-414-400: 6

As it can be seen, M88 and EJ200 would be easiest to maintain, especially the M88.

Service life is as follows:

EJ200: 6.000 h

M88: ??

RM-12: 4.000 h

F-135: 2.000 h

F119: 6.000 h (?)

F404-GE-402: 4.000 h

F414-400: 6.000 h

AL-31F: 1.500 h

AL-41F: 4.000 h

Overall, EJ200 is the most user-friendly engine.

IR signature

Engine inlet temperature can be used to approximate IR signature when combined with thrust. It is not a perfect measure as there are other factors influencing IR signature as well.

EJ200: >1.800 K, 20.250 lbf

M88: 1.850 K, 16.620 lbf

RM-12: >1.717 K, 18.100 lbf

F-135: 2.255 K, 43.000 lbf

F-119: ?, 37.000 lbf

F404-GE-402: 1.717 K, 17.700 lbf

F414-400: ?, 21.890 lbf

AL-31F: 1.685 K, 27.560 lbf

AL-41F: 1.887 K, 39.340 lbf

M88 has an additional cooling channel beyond one typically present, as well as second set of nozzles which partly hide the afterburning plume and inner nozzle. F-119s nozzles, meant to reduce RCS, also reduce IR signature of the exhaust plume by increasing its area/volume ratio. F-135 on the other hand has relatively thin skin, and the F-35 is thin-skinned itself, thus increasing IR signature. EJ200 is another engine that had its skin thinned in order to save weight.

Combination of thin skin, high thrust and very high inlet temperature means that the F-135 has the highest IR signature, while the M88 has the lowest IR signature due to low thrust and IR signature supression measures; F404 should have the second lowest IR signature. Further, higher operating temperature means greater stress on components and thus more frequent maintenance, other things being equal.

Conclusion

Overall, the F-119 is the best engine where performance is concerned, followed rather closely by the EJ200 and F-414-400. EJ-230 is better than the F-119. RM-12 is the second worst and F-135 is the worst Western engine while the AL-31F is the worst engine overall (not surprising considering its age; AL-41F does match modern Western fighter engines in at least some performance parameters, but at cost of the service life).

All problems with the F-135 are connected to the fact that the F-35 is a strike fighter by design, and not a proper multirole fighter; on the other hand, EJ200, M88 and the F-119 are designed for fighter aircraft whose primary role is air superiority. As a result, F-135 is optimized for different operational conditions and regimes compared to other engines listed here, and it is unrealistic to expect the F-35 to achieve even marginal supercruise performance. On the other hand, it can be seen from the article, and notes below, that the F-119s advantages stem mainly from its large size.

That being said, pure performance is not the only important factor. Just as important, if not more so, are reliability and ease of maintenance in the field. EJ200 is likely the most reliable engine, while the M88 is easiest to maintain. When all factors are taken into account, EJ200 would be the best choice for a fighter aircraft – assuming that thrust is sufficient, of course.

Notes

Turbojet J85-GE-21 with 5.000 lbf / 22 kN / 2.243 kgf of afterburning thrust would have a thrust-to-weight ratio of 11,74 and thrust-to-drag ratio of 13,84 N/cm2. J97-GE-100 has 8.000 lbf / 35 kN /3.629 kgf has a thrust-to-weight ratio of 11,5:1 and thrust-to-drag ratio of 14,27 N/cm2. Low thrust-to-drag ratio despite these engines’ high thrust-to-weight ratio and lower frontal area than that of the comparable turbofan can only be explained by their small size, confirming the conclusion about single vs twin engines from first section of the article. For comparision, J79-GE-17 turbojet (J97 was/is used on the F-104, F-5, F11F-1F, IAI Kfir, A-5 and F-16/79) has 17.835 lbf / 79,3 kN / 8.090 of afterburning thrust, thrust-to-weight ratio of 4,6:1 (40% of the J97-GE-100) but thrust-to-drag ratio of 10,67 N/cm2 (75% of the J97-GE-100).

If the F119 is reduced to the EJ200s size, it would be 4 meters long and 93 cm in diameter, compared to 74 cm for the EJ200. Inlet diameter would be 68,5 cm, dry weight ~1.000 kg, and thrust 91,4 kN (9.320 kgf). Thus it would have a TWR of ~9,32:1 and thrust-to-drag ratio of 24,8 N/cm2, or 92% of the current value, again confirming that larger engine offers better performance than two smaller engines.

[knigh7]

Ficou faltando a da F-414, que nem no Site da GE eu achei mais do que tu, ou seja, quase necas de dados...

Aqui em casa em tenho pilhas de materiais sobre o Rafale, Gripen, F-35, F-22, SH e Typhoon

[Túlio]

São dados excelentes mas que dizem só das turbinas em si, não do que fazem quando instaladas em um caça. Por exemplo, há algum monomotor além do Gripen com F-414 ou M88 para comparar? Porque meu ponto é: só depois de instalar e testar é que se sabe o que aquela turbina possibilita ao avião, desenho dos inlets incluído.

[knigh7]

Sim, é por isso que eu estou passando agora os dados oficiais do desempenho das turbinas com a autonomia das aeronaves:

Revista da Dassault, FOX3 dando a autonomia do Rafale em configuração limpa, a baixa altitude:



Dá cerca de 1250km provavelmente entre 0 e 3000 pés.

[Túlio]

PUTZ, começo a achar que um Rafale BR com WAD (ideia nossa, nem o Gripen ia ter isso, e facilitada pela AEL ser subsidiária da mesma empresa quer faz o do F-35) talvez fosse mesmo melhor do que o Gripen E/F...

Claro, se é pra torrar dinheiro dos meus impostos como se não houvesse amanhã, sempre vou ser mais SUPER FLANKER com WAD...

[knigh7]

Há dados da SAAB com a F-414G com aeronave demonstradora limpa, sem cargas externas. 2.500km sem especificar a altura, entretanto deve ser a grande altitude para otimizar o consumo.

[knigh7]

PUTZ, começo a achar que um Rafale BR com WAD (ideia nossa, nem o Gripen ia ter isso, e facilitada pela AEL ser subsidiária da mesma empresa quer faz o do F-35) talvez fosse mesmo melhor do que o Gripen E/F...

Espera que ainda tem muito a discutir e mostrar...

P.S.: vou jantar

[Túlio]

PUTZ, começo a achar que um Rafale BR com WAD (ideia nossa, nem o Gripen ia ter isso, e facilitada pela AEL ser subsidiária da mesma empresa quer faz o do F-35) talvez fosse mesmo melhor do que o Gripen E/F...

Espera que ainda tem muito a discutir...

OK, só lendo (e aprendendo) a partir daqui...

[knigh7]

Vamos lá.

A Dassault divulgou a autonomia do Rafale em baixa altitude, em configuração limpa. 90 min a 450kt, o que dá cerca de 1.250km


Eu NÃO tenho o manual de voo do Rafale (na época do Fx2 eu procurei muito e não encontrei disponível para o público). Mas com base em outroas aeronaves semelhantes acho que dá para ter uma ideia aproximada do consumo de combustível em grande altitude nessa mesma velocidade e configuração limpa com tanque intrerno cheio. Até porque a diferença entre as aeroanves analisadas é pequena.

A diferença de consumo a 450kt =0.67mach sem arrasto de interferêcia (0 drag index) com tanque interno cheio e configuração limpa do F-16bl50 e o Hornet entre 2.000/2.500 pés e 30.000 pés é de 101% a 122%.









Hornet

450kt (0.67 mach), aeronave limpa, sem drag com tanque interno cheio: 34 mil lb

Sea level: 8.000lb/h
A 2.500 pés 7.350lb/h
5 mil fts 6.700lb/h
30 mil fts 3.300lb/h
Consumo a mais 122%
----------------

F-16 com 28 mil lb (aeronave limpa e tanque interno cheio sem drag) a 450kt

Sea level: 5.475lb/h
A 2.000 pés 5.162lb/h
A 4.000 pes: 4.850lb/h
A 30.000 pés: 2.568lb/h
Consumo a mais: 101%

[knigh7]

Ou seja, se o Rafale tem uma autonomia de 1250km em configuração limpa, a 450 kt voando a baixa altitude, é provável que ele tenha o dobro da autonomia voando a 30.000 pés. Mas não pude levar em conta o consumo necessário para o Rafale subir até os 30.000 pés para o voo a grande altitude.
Como a SAAB divulga a autonomia do GripenE como 2.500km, sem cargas externas, obviamente a grande altitude, devem ter autonomias parecidas sem cargas externas.

O ideal seria se a Dassault tivesse divulgado a autonomia do Rafale a grande altitude em configuração limpa, mas pelo o que eu saiba, ela divulgou há muitos anos atrás um lacônico "maior que 2.100km".

Vale ressaltar que é um cálculo aproximado apenas para termos uma ideia da autonomia entre os 2 na mesma configuração. E se do Rafale for 2.600km ou 2.400km não será isso que mudará o quadro, já que a própria autonomia inclui outras variáveis.

[knigh7]

Com cargas externas, em ataque a longo alcance ~800MN, fica o que eu havia mencionado há 2 páginas atrás

Olha, sem querer discutir muito esse assunto, "falando por cima", segundo a Dassault, o Rafale leva 2 toneladas de bombas a 1.465km. No caso do GripenE, segundo a SAAB, tem um raio de ação em configuração de ataque de 1.500km. Entretando, essa configuração de ataque do caça sueco deve ser no máximo de cerca 1 tonelada de cargas. Mais do que isso (por exemplo, 1.500kg) passaria exigir demais da aeronave e toda a vez que ela chega próxima do limite projetado (pois ela deve estar fazendo com base em 2 tanques de 450gal, de maior capacidade) o desempenho vai caindo muito. Se a SAAB tiver calculado com apenas 500kg de bombas (por exemplo 1 GBU-16 ou 2 GBU-12) e se dobra a carga colocando no lugar 1 GBU-10 ou 2 GBU-16 o coeficiente de arrasto aumenta pouco para uma aeronave como o F-16 block50/52 ou o Hornet (não o SH) para ficar como exemplo de um caça mais próximo do GripenE.

No site Avialogs:
http://www.avialogs.com/
há uma centena de manuais de voo , inclusive do F-16 e do Hornet, que vc pode consultar e constatar o que eu escrevi.

Então a grosso modo, um Rafale, em ataque a longa distância, leva o dobro da carga de um Gripen E.

[knigh7]

A propósito:

A Dassault divulgou dados de autonomia do GripenNG na concorrência do FX2 que são bem inferiores aos divulgados pela SAAB para configurações ar-ar e ar-solo.

Provavelmente o que deve ter acontecido é a fabricante francesa ter calculado com base em tanques de 300gal enquanto que a SAAB fez com base em tanques de 450gal.

Obs: aquela comparação desempenho entre as turbinas vai render bastante coisa para debater.