Sidewinder- page 3 | Military Aviation | Air & Space Magazine
During Desert Storm, most fighters packed Sidewinders: F-16s armed with the missiles await the next mission. (USAF/TSGT Fernando Serna)

Sidewinder

The missile that has rattled enemy pilots since 1958

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(Continued from page 2)

The date was April 24, 1967, and Wisely was embroiled in an epic furball: three F-4s against eight or nine MiG-17s. Twice, he was in position to fire the gun he didn’t have. Compounding the problem, his Phantom had been loaded with only one Sidewinder instead of the usual four (a fast turnaround of the aircraft between missions didn’t leave enough time for ground crews to install the full ordnance load). He was carrying four Sparrows, but he figured he was too close to the nimble MiGs to use the long-range missiles.

“We’re not going to get radar lock in this environment,” Wisely recalls radioing his backseater, Lieutenant (junior grade) Gary Anderson. “I’ll just keep pulling the airplane up, using the afterburner as necessary, then unloading it and turning so you can reach around in your seat and really check our six.”

Zooming up and down between the treetops and 5,000 feet, Wisely waited for the right shot for his single Sidewinder. Twice, he saw Sparrows punched off by other Phantoms fly harmlessly into the distance. Then he spotted a MiG sidling in behind an F-4. Wisely rushed in behind it, heard his Sidewinder growling, and fired. Another North Vietnamese pilot must have alerted Wisely’s prey. But as the MiG banked right to escape the missile, the ’Winder struck and exploded.

“It was just ‘Thank you very much, MiG,’ ” Wisely says today.

Wisely’s experience notwithstanding, guided missiles performed much worse in Vietnam than expected. Sparrow hit rates through 1968 were so anemic—eight percent—that most pilots fired them in pairs, figuring at least one would be a dud. With a hit rate of 16 percent, the Sidewinder was twice as good but not nearly good enough. Actually, the Navy version of the Sidewinder, the AIM-9D, had a nitrogen-cooled seeker head that improved its ability to track infrared radiation, enabling it to outperform the Sidewinders used by the Air Force. Nevertheless, the Navy was so upset that it commissioned a hard-driving captain named Frank Ault to figure out what was wrong.

After several months of study, Ault produced a 480-page Air-to-Air Missile System Capability Review. Popularly known as the Ault Report, it began by assessing what happened when 600 air-to-air missiles were fired in 360 Navy and Air Force combat engagements between 1965 and 1968. “Only about one in ten had any probability of achieving a kill,” the report stated. To hit its target, the Sidewinder had to be launched within a strictly defined envelope, no more than roughly 30 degrees off the tail of the adversary and at relatively modest G loading. Among his 242 recommendations, Ault suggested that the Navy create a school for post-graduate air-to-air combat training. In 1969, the Navy Fighter Weapons School, a.k.a. Topgun, was established at then Naval Air Station Miramar in California.

“Most dogfighting maneuvers, from World War I to Vietnam, were designed to put a fighter in a gun’s firing envelope,” says Robert Shaw, an author and air combat consultant who used to fly a gunless Navy F-4. “But with the Sidewinder, once you got into gun range, you were too close to fire.” Since airplanes were so much farther apart, turning with the enemy made no sense, so counterintuitive tactics—flying vertically when the target turned horizontally, for example—were developed. Also, the conventional fighting, or welded, wing, in which the leader hunts for targets while his wingman protects his rear, didn’t work in the missile environment. Instead, Shaw explains, aircraft moved farther apart and flew line abreast so that each could watch the other’s tail.

As tactics improved, so did the Sidewinder. Over the years, it underwent a series of upgrades—better seekers, more efficient fuses, stouter rocket motors, slicker aerodynamics—to expand the firing envelope and make the missile less susceptible to countermeasures. The AIM-9L added all-aspect capability—it could hit an airplane no matter what its relative angle, even approaching head on. This so-called Super Sidewinder was so deadly that in dogfights over Lebanon and during the 1982 Falkland Islands War, it posted kill ratios of better than 80 percent. And in the next decade the follow-on, AIM-9M, was even more efficient in dogfights over Iraq and Bosnia.

But by the mid-1990s, the Sidewinder seemed on the verge of being replaced by newer heat-seeking missiles with more bells and whistles. Instead, a digital makeover gave engineers the chance to “teach an old dog new tricks,” as Dave S. Adams, director of Raytheon’s short-range-missile programs, puts it. In the fifth generation AIM-9X, the analog seeker and its mechanically rotating mirror—what Adams calls a “chirps and squeaks system”—were replaced with a staring focal plane array, the pixel-based technology in a digital camera. Besides being able to track infrared energy more efficiently and see targets more accurately through its nose cone, the latest AIM-9X is also far better at distinguishing between targets and countermeasures, such as flares.

At the tail end of the missile, designers added movable jet vanes to redirect the exhaust plume of the motor and achieve a form of thrust vectoring. This allows the -9X to turn at much sharper angles after coming off the launch rail than previous models, which is a major advantage in close-in aerial combat—the proverbial knife fight in a phone booth. And by using thrust vectoring to help control the missile, designers could reduce the size of the Sidewinder’s conventional control surfaces—canards and tail fins—and clean up the missile’s aerodynamic profile. So despite using the same solid-fuel rocket motor as the -9M, the -9X flies significantly faster and farther.

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