According to this source, designers of military fighter jets seemed to have stopped centering their design on Whitcomb's Area Rule for quite a while. Yet even the twin series fighters struggle to break the sound barrier without afterburner in a combat loadout. Then why have the designers stopped caring about transonic drag reduction? Or is it because they never intend to let their jets come near Mach 1, just a little bit below it or use the afterburner and shoot past it? Does this mean newer supercruising fighters, if they intend to fly all the way up to their Mach 1.5-ish cruise speed on dry power, should still care about shaping according to the Area Rule?
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asked Feb 11, 2019 at 15:51
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1$\begingroup$ The article itself says, "With the advent of more powerful jet engines, “drag rise become less of a factor because you have enough power to bulldoze through it,” says Martin. That’s why designers of the Typhoon or the Lockheed Martin F-35 Lightning II don’t give a moment’s thought to drag rise; engines on those aircraft have plenty of brute force to overcome it." $\endgroup$– abelenkyCommented Feb 11, 2019 at 16:37
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Of course designers still care about the area rule, but it has become less important. The original area rule is just for Mach 1; at higher speeds you need to look at the cross section distribution along the Mach cones - but which ones? They change with angle of attack and Mach number, and there is no single point anymore where performance needs to be optimized. Rather, the aircraft has to perform well from subsonic to mild supersonic speeds, and the higher speeds for which the older designs from the Fifties and Sixties were optimized turned out to be irrelevant in practical use.
Next, which configuration needs to be optimized? The F-106 carried exactly one type of AA missile. Today, the typical aircraft will carry everything from dumb bombs to laser illumination pods, with fuel tanks and electronic warfare pods thrown in between. With that kind of variety in accessories who can tell which configuration exactly it is which needs to obey the area rule?
answered Feb 11, 2019 at 18:36
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$\begingroup$ To all nitpickers: Yes, I know that the F-106 could also use other missiles, but nuclear warheads on AA missiles were and still are an oddity. $\endgroup$ Commented Feb 11, 2019 at 18:37
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1$\begingroup$ Also the use of conformal tanks would ruin a Whitcomb design. $\endgroup$– user14897Commented Feb 11, 2019 at 21:56
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3$\begingroup$ @ymb1 … they are a sign of desperation. This happens when a good design is abused for tasks it was never designed for. And still they are the least drag-inducing way to carry more fuel. $\endgroup$ Commented Feb 11, 2019 at 22:53
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$\begingroup$ @PeterKämpf then what about the statement in the link about modern engine powerful enough to not care about transonic drag? I got the impression that although the jet engines have become multiple times more powerful than the 50s~60s, very few modern fighters can break the sound barrier on their dry thrust alone. Then what is the precise meaning or implication of this "powerful engine" statement? I get that F106 is the poster kid of the area rule because it needs to concentrate on M=1 drag reduction to be able to break the sound barrier at all, then what about modern fighters? $\endgroup$ Commented Feb 12, 2019 at 11:53
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2$\begingroup$ @MeatballPrincess: Using AB to penetrate the sound barrier saves fuel. However, with increasing speed comes increasing ram pressure in the intake, so the same engine will produce more thrust at a higher Mach number. That is what makes super cruise possible. The excess thrust helps most in subsonic manoeuvring: It allows the highest turn rate without loss of altitude. $\endgroup$ Commented May 19, 2019 at 3:56
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