The missile that has rattled enemy pilots since 1958.
- By Preston Lerner
- Air & Space magazine, November 2010
USAF/TSGT Fernando Serna
(Page 4 of 5)
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.
MARCH 1991. The war with Iraq was over, but the cease-fire was still in place, and Captain Tom Dietz and his wingman, Lieutenant Bob Hehemann, were patrolling the skies 50 miles north of Baghdad in their Air Force F-15 Eagles. During the fighting, they’d used Sidewinders to down four Iraqi jets making a run for the Iranian border. But according to the rules of engagement in force since the cease-fire, the Iraqis were allowed to fly helicopters. So when Dietz locked up a pair of targets on his radar scope, he assumed that’s what they were—until he realized that they seemed to be flying at 345 mph. “Let’s go investigate this,” he radioed Hehemann.
They pushed their throttles forward to military power. At a range of about five miles, Dietz started to make out the details of one bogey: Canopy. Sloped tail. Swept wings. Suddenly, his radio crackled: “VID Fitter.” Hehemann was visually identifying the Iraqi aircraft as a Sukhoi Su-22 fighter-bomber (“Fitter” is the Su-22’s NATO name). They would later learn that it was returning from a mission to bomb Kurdish civilians. Dietz, closing quickly, immediately activated the master switch, which cooled the seeker head of his Sidewinder by flooding it with argon gas. A second or two later, he uncaged the missile, got a good tone, and fired.