Shoot 'Em Up- page 2 | Military Aviation | Air & Space Magazine
A live-fire test on a North American F-86. During the Vietnam War, engineers looked for ways to toughen aircraft against ground fire and surface-to-air missiles. (U.S. Navy)

Shoot 'Em Up

Sometimes you have to destroy the aircraft in order to save it.

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(Continued from page 1)

Back at the lab, Atkinson and his colleagues began conversations with engineers at the Army’s Aberdeen Proving Ground in Maryland and the Navy’s laboratory at China Lake, establishing an informal interservice network of people concerned about decreasing the vulnerability of U.S. aircraft. In 1970 China Lake conducted its first vulnerability test, on a McDonnell Douglas A-4 Skyhawk, and a year later Atkinson’s network officially became the Joint Technical Coordinating Group for Aircraft Survivability. Its research, tests, and recommendations proved effective. F-4s, for instance, were modified late in the war with self-sealing fuel lines and tanks and redundant and independent hydraulic systems.

But it’s one thing to modify operational aircraft based on combat experience, another altogether to design and build survivable aircraft from the start—and prove their robustness through live-fire testing in the laboratory. Indeed, says Atkinson, who retired in 1992 from his position as staff assistant for survivability and battle damage in the Office of the Secretary of Defense, “aircraft design takes so long that we were able to make those changes on the F-4 only because the war went on for so long.” Even as Atkinson’s coordinating group pushed for survivability and live-fire testing to be made an integral part of aircraft design, events conspired against them. The Vietnam War ended. “When there’s no war, people’s interest in survivability just dies out,” says Atkinson. At the same time, the Air Force left Vietnam determined to modernize its fleet. But rather than focusing on vulnerability—“Can he kill me?”—the service decided to try solving the first problem in the survivability progression: “Can he see me?” Stealth technology claimed billions of post-Vietnam development dollars. “All the services tried to take money out of vulnerability and testing,” says retired colonel James B. Sebolka, former military assistant to the director of live-fire testing in the Office of the Secretary of Defense. “Everyone wanted stealth. The thinking was: If we could avoid getting hit, no worries.”

Reducing vulnerability was perceived as adding weight and complexity at the expense of performance and cost, pricey insurance for a benefit whose success in combat is difficult to quantify. “A program manager’s whole career is dependent upon staying within cost and meeting timelines and performance requirements,” says Sebolka, “and there’s no incentive whatsoever to say ‘Hot damn! I want to see the most rigorous live-fire program to save some GI who goes to combat 15 years after I retire.’ ”

The result: “We fielded the F-15, F-16, F/A-18, AV-8B, the M-1 tank, and the Bradley Fighting Vehicle [in the late 1970s and early 1980s], none of which had seen combat or ever been realistically tested in full combat conditions,” says Jim O’Bryon, director of live-fire testing and deputy director of operational testing and evaluation in the Office of the Secretary of Defense until his retirement last year. In 1984, concerned about the vulnerability of those expensive, virgin weapons systems, Sebolka, Atkinson, and the live-fire gang on the Joint Technical Coordinating Group for Aircraft Survivability pushed through funding for the Joint Live Fire Program, the first program for methodically testing already fielded systems. Vulnerabilities were immediately uncovered: In 1987 China Lake testers discovered that the AV-8B Harrier—an airplane designed for close air support—“was the world’s most vulnerable airplane to small arms,” says Chuck Myers, “an airplane we never would have bought if it had been subjected to live-fire tests.” As the Harrier lifts off, it produces very hot engine downdraft adjacent to hydraulic lines, so if bullets hit the hydraulic lines, says O’Bryon, “you’ve got a ready-made fire, all while you’re hovering, so you’re in the worst possible situation.” The fixes suggested for the Harrier were “either too costly, too heavy, or too difficult to implement,” according to Joe Manchor, who worked on the program. “The AV-8B is the classic example of why vulnerability testing should be done early,” he says.

But what really changed the world of survivability testing was the Bradley Fighting Vehicle, an armored troop carrier built of highly combustible aluminum. Incensed by the Army’s failure to test the Bradley realistically, Congress passed the Live Fire Test Law in 1986. The law requires survivability testing on all weapons systems, including airplanes, in realistic, full-up, armed configuration before they can proceed to full production. Finally, two decades after airplanes began falling out of the skies in Vietnam, the survivability and live-fire engineers at places like China Lake had the law to back them up. 

“I can’t think of anything more fun than burning things up and exploding things!” says J. Hardy Tyson, standing next to an F/A-18E Super Hornet that looks like it lost a fight with a fire-breathing dragon. It’s the day before the MH-60 test, and Tyson, a survivability test engineer sporting wraparound shades, and laboratory director Kovar are showing me around the lab’s boneyard. They’ve clearly been busy: I see F-4 Phantoms, F-14 Tomcats, F-16 Fighting Falcons, and UH-1 Hueys destroyed by Stingers, along with AV-8B Harriers, V-22 Ospreys, AH-1 Cobras, and an assortment of unrecognizable scraps, wings, and tails, all blackened and perforated. Tyson’s exuberance (and the evidence) notwithstanding, I’m disappointed to find out that I won’t be seeing a hail of rockets and anti-aircraft artillery shells blowing multimillion-dollar fighters into confetti. Tyson and his colleagues are scientists and engineers, after all, and every test is exhaustive. “Each test shot,” says Kovar, speaking slowly, taking care with each word, “often takes months to set up and ends in a matter of seconds.”

Long before the projectiles start flying, the engineers at China Lake review a STAR—system threat assessment report—which outlines the threats an aircraft is expected to face in combat. (Only threats that have a less-than-100-percent chance of a kill are tested.) Using computer models, engineers determine the paths of specific shots and which shot lines would “cause the aircraft to die,” as Tyson puts it. “We ask the modelers to figure out how to hit the component, and just what the probability [of that part’s failure] is if you’re flying at certain speeds, altitudes, and angles.” Then comes the delicate balancing act: Engineers must design ways to shoot bullets and missiles and explode fragments at aircraft operating under conditions that are life-like yet so precisely controlled that the tests don’t destroy the test article too soon.

Tyson began testing components of the Super Hornet in 1993, long before the first one was built. Live-fire tests on earlier F/A-18 versions had identified persistent fire problems, especially from shots to the fuel tanks along the airplane’s keel. To experiment repetitively with tests that might eat airplanes like a kid eats cookies, Tyson and a team of engineers at the lab built a full-size steel replica of the F/A-18 belly, using a design created by Northrop Grumman and imitating the Super Hornet’s fuel cells and dry bays (empty spaces adjacent to fuel tanks through which fuel lines pass). They mounted the replica in the lab’s giant high-velocity-airflow system, which uses four jet engines to mimic inflight airflows of up to 500 knots (575 mph) over various parts of the airplane, to study how fire spread in the vicinity of the tanks. Their eventual solution: a fire protection system in which a small rocket motor floods the bays with inert gases, a system similar to that which inflates car air bags. Today, the Super Hornet and V-22 Osprey are the first aircraft to have full dry-bay fire protection. In 1996 Tyson got a full-size wing, a year later he got an engine, in 1998 he got four F/A-18As to play with, and six years after starting he got his first genuine F/A-18E, a now-blackened boneyard hulk nicknamed Christine, after the indestructible vintage car in the Stephen King novel of the same name. But by that time all the development work had been done; Christine merely verified it.

“We did a series of seven tests on her,” Tyson says, leading me around the airplane, “and you can see different areas that have been impacted.” That’s an understatement. One wing’s leading edge has a hole wide enough to step through, more holes riddle the engine nacelles and intakes, and the belly is as blackened as the inside of a fireplace.

Tyson’s long series of tests—622 shots in seven years—identified not only the repercussions of bullet-ignited fires in the fuel tanks, engine nacelles, and dry bays but also a weakness on the horizontal stabilator’s attach  points. All the components were redesigned, and Tyson shows me a video of the results. Christine is mounted on the test pad and air is flowing around her at several hundred miles an hour; bullets punch through the airplane; fires flare in the racing wind, then miraculously disappear. Cameras mounted inside the wings and fuel tanks show blackness, roaring fire, and then blackness again—all in half a second.

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