Chapter 3 - The Might and Raq Power of F22
Chapter 3 - The Might and Raq Power of F22
Rafael used close-coupling canards (again, means canards being close to the delta wing), ignore trim and pitch controllability. The two canards provice great vortex lift, boost agility, but its trimming ability is minimial, resulting in great subsonic performance and bad supersonic performance. But take note of (placement of) the canards on the LERX, the French did a very good job there.
It is well known that the close-coupling canards used by the Gripen and Rafael ignores trimming and pitch controllability. The two canards provice great vortex lift, boost agility, but the trimming ability is minimial. F22 caters the need for both subsonic agility and especially supersonic maneouverability. It emphasizes on taking good position through its sheer speed, even without turning on afterburners it could supermaneouvre at around Mach 1.5. (I wondered, won't those pilots die maneouvring at high G's while maintain speed of Mach 1.5)!
In supersonic maneouvres, roll maneouvre at supersonic speed is difficult to achieve regardless of F22, T50 and J20. But it's great for escape and acquring geat positions in dogfights. But even 5th generations have difficulties opening their weapon bay during a roll at supersonic speed to launch a missile. To achieve first-shoot ability, sustained turn-rate under supersonic speed would be the most important, and this is F22's greatest strong point!
Many people argue supercruise exists for a long time, like the Mig25, although it's still only high thrust engines with temporarily turning on afterburners to gain momentum to achieve short term super cruise without having afterburner on the whole time. Even the British Lightning can achieve supercruise at Mach 1.1, some even say that J-12 could cruise at Mach 0.94 without afterburners, claiming to be super subsonic cruising.
But all those are fake supercruise without exception, especially that none can perform maneouvres while maintaining supersonic speed. F22 could perform exotic maneouvres while flying at Mach 1.5. On the contrary, the famous Mig 25 has archaic trimming, making it very sluggish in supersonic speeds. The Americans described it as "useful for escaple, useless for attack."
Quoting from expert again, "F22's maneouvrability at supersonic speed is one of the important design criterias, it is also the determining symbol for generation gap. Apart from the supercruise, excellent acceleration and climb performance, sustained turn-rate at supersonic speed is also greatly improved. From open sources, this plane could achieve 6.5G at M1.7. Considering F15 sustained turn-rate at similar conditions is far inferior, and Su27 could only achieve this in mid-altitude and at speed of M0.9, this is undoubtedly a suprising achievement".
It could achieve such high-G turn in supersonic because of its insane engines, but this is also credited to its lift-drag ratio and trimming ability.
Speaking of lift-drag ratio, it is not diffuclt to understand; To sustain a high-G turn requires lift from the wings, but drag comes along and grow exponentially (the value of drag coeffecient to wings positive angle of attack is exponentially related, and inversely related to the wingspan). If the drag coeffecient is too big, drag increases too rapidly and rapidly uses up thrust of the engines. Although the plane could still pull off high-G maneouvres, it cannot be sustained because the engine will not provide enough thrust. This is the reason why Mirage III's instantenous turn-rate is good but the sustained turn-rate is low. At today's aeronautic level, it is not difficult to develop high lift-drag ratio wings or wings with good supersonic performance. However, designing wings achieving both objectives requires enormous efforts. This is something that F22 should be proud about!
Trimming ability is often neglected by people. Wing's high lift is fundamental to high-G maneouvres, but as lift increases, so does pitching moment. If the aircraft cannot provide sufficient moment for counter-balance, it could easily flips backward and lose control; or nose-down moment could prevent the desired angle-of-attack from being reached. Especially during supersonic flights, as the centre of lift travels toward the aft, there is a significant nose-down moment. So supersonic manevoures require significant trimming ability. The plane famous for supersonic speed, the Mig 25, cannot perform supersonic manevoures because of its trimming limits. When it cruises in supersonic speed, its horizontal tail's already rotated to its limit, with very little margin left for maneouvres. Although the airframe is capable of handling much more G forces, it can only perform up to 3G at Mach 2.
In another word, F22 is scary not only because of its stealth, but rather its insane supercruise and supermaneouvre capability at supersonic speed. During military exercises, F15s and F16s have difficulties beating F22 even when the F22 carries corner reflectors. F22 could use its speed and supersonic maneuverability to gain position to launch missiles, and its sheer speed also add a lot of momentum to its missiles. This implies a first shot ability, and even if the missiles miss, F22 could exit and occupy another good position to attack. 3rd generations aircraft couldn't keep pace with F22's rhythm.
In those exercises, pilots say that "when engaging the F22, its game over as soon as its enters supercruise. We can't catch up even with afterburner. If we keep chasing then it's bingo (out of oil) and the exercises would be over. We would have to quickly return to refuel by tanker planes, while F22 still has lots of fuel remaining."
(It would be great to find the original statement.)
The author seems very knowledge about the decision-making and research behind the Chinese 5th generation fighter plane, not just the J-20 and SAC's entry as well. It's fascinating to read, thanks again.