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Saab Gripen vs F-35

Posted by picard578 on March 16, 2013

AIRFRAME PERFORMANCE

Contrary to some claims, F-35 has rather simple and conventional aerodynamics. Basic configuration is similar to F-16, however lack of LERX, and use of lower-performance but stealth-friendly chimes for high AoA lift enhancement, means that it will have far less body lift than F-16 to help compensate for its high wing loading, and wing lift will also be smaller at high AoA. Result will be (for a modern fighter) disastrous turn rate.

Further, it has internal carriage, which adds drag compared to low-drag AAMs and pylons, and its far higher weight also means more inertia that has to be overcome.

Gripen is, on the other hand, built for maneuverability. Close-coupled canards, wing-body blending, and wing shape all help increase lift during maneuvers, allowing aircraft to both achieve higher angles of attack, and to turn tighter at same angle of attack. Particularly canards create vortices that reattach air flow to the wing at high angles of attack. Aside from helping air flow over the wing, Gripen’s canards also help air flow over the body. Canard also has advantage over tail as the control surface – as center of gravity for modern aircraft is towards rear of the aircraft, usage of canard results in longer moment arm than it is case with tail. Further, Gripen has large degree of wing-body blending, and it’s wing loading is also far lower than that of F-35.

While thrust-to-weight ratio is below 1 for both aircraft, Gripen has far lower drag than F-35, partly compensating for F-35s superior thrust-to-weight ratio. While F-35 achieves maximum of Mach 1,6, clean or not, Gripen can achieve speeds of over Mach 2 clean.

 

SITUATIONAL AWARENESS

First thing that can be noticed about both Gripen and F-35 is that neither has rearward visibility from cockpit. In Gripen’s case, attempt was made to attenuate the problem by installing rear-view mirrors onto the canopy forward frame. However, while Gripen’s visual and IR signatures are far lower than F-35s, Gripen itself does not have IRST, which means that F-35 may be able to detect it first.

 

WEAPONS

In gun department, Gripen uses German BK-27, a 27-milimeter revolver cannon which was also supposed to be equipped to F-35, but in the end, F-35 received 25-milimeter rotary-barrel GAU-22. In air-to-air combat, BK-27 has a large advantage over GAU-12 in that delay between pilot pressing the button and full rate of fire being achieved is just 0,05 seconds, as opposed to 0,4 seconds for GAU-22. Further, on F-35, trap door must open if gun is internal (and assuming it wasn’t open already), possibly adding another 0,5 seconds to process. Maximum rate of fire is 1 700 rpm for BK-27, and 3 300 rpm for GAU-22. Muzzle velocity is 1 025 m/s for BK-27 and 1 040 m/s for GAU-22, but BK-27s shells – weighting 260 g as opposed to GAU-22s 184 g for HEI and 215 g for AP – will bleed off speed slower, and be less affected by wind and other air turbulences.

Therefore, in first half of second – which is crucial in dogfight; rarely will opponent fly in the same directon for full second or more – BK-27 will fire 14 projectiles massing 3,64 kilograms, and GAU-22 will fire 16 projectiles massing 2,94 – 3,44 kilograms, but only assuming that F-35 pilot opened gun doors beforehand – if he didn’t, GAU-22 will not fire any projectiles at all. GAU-22 may be a sign that US have (finally) understood that 20 mm cannons are not sufficient for modern air-to-air combat, similar to WW2, when they delayed introduction of 20 mm cannons instead of 50 caliber machine guns as main fighter armament well into Korean War. However, it is more likely that it was thought of as compromise between air-to-air and air-to-ground combat, considering that F-35 is primarly ground attack aircraft.

 

FORCE PRESENCE AND SUPPORTABILITY

While F-35A costs 197 million USD flyaway, Gripen C costs 40 million USD flyaway. As such, Gripen can provide almost 5 times as large force as F-35A can. Further, due to Gripen’s lower maintenance and turnaround times, same force will be able to fly far more sorties. Gripen is also designed to operate from roads, and has STOL capability, something that F-35A lacks, though not the (even more expensive) F-35B.

 

5-TH GENERATION?

According to this article, Lockheed Martin’s definition of 5-th generation fighter is following:

– stealth
– high maneuverability
– advanced avionics
– networked data fusion from sensors and avionics; and
– the ability to assume multiple roles.

Comparing F-35 and Gripen, it can be seen that while F-35 is stealthier on radar, Gripen has far lower IR and lower visual signature. Unlike F-35, it also has high maneuverability, and both aircraft have advanced avionics and multirole capability, while networked data fusion will be avaliable on Gripen NG. F-22 has high maneuverability but is not multirole, while Rafale and Typhoon only lack stealth. Thus, F-22, F-35, Typhoon, Rafale and Gripen NG are all equally 5-th generation aircraft, with Gripen C/D being just one step away.

 

And while another article defines fifth generation fighter as “being able to operate in anti-access environment featuring integrated air defenses…”, that capability can also be achieved in several ways, radar stealth being just one aspect of survivability, and rather limited one considering proliferation of passive sensors.

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