Shoot 'Em Up
Sometimes you have to destroy the aircraft in order to save it.
- By Carl Hoffman
- Air & Space magazine, November 2002
Someday, on a mission to extract a special operations team, a pilot will fly into enemy territory in an MH-60S, a forthcoming U.S. Navy version of the Sikorsky Black Hawk helicopter, and an anti-aircraft round will drill into the MH-60’s rotor drive system. For the shooter on the ground, hitting the helicopter won’t be easy—it will be moving fast, the rotors and shaft spinning faster—but there are always lucky shots. The pilot will feel a jolt and wonder if his aircraft can survive the strike.
Joe Manchor is about to find out, long before the pilot has to. Dressed in sneakers and blue jeans, the lead engineer on the live-fire test and evaluation of the MH-60S has a prototype of the helicopter locked onto a steel platform, dead in the sight of a nasty-looking gun. We’re at the Naval Air Warfare Center’s Weapons Survivability Laboratory at China Lake, California. The rig is 10 miles into China Lake’s hidden city, 3,800 square miles—an area the size of Delaware—of high Mojave scrub and mountains. Outside the sky is deep blue, the winter sun glaring, but we’re hunkering in a windowless control room protected by a 20-foot-tall wall of steel plate. Two hundred yards away on a test pad stands the helicopter, prepped for its final judgment. Though it was built with care and is worth over $10 million (and no doubt coveted by dozens of aviation museum curators), it is being sacrificed for the future glory of the MH-60s that will go to war.
The helicopter is bolted to a system of steel beams and remotely controlled airbags and actuators that took eight months to design and build. Mounted on another steel frame 30 feet from the MH-60 and level with its rotor mast stands the remotely operated, electronically fired gun. Exactly what bullet it’s about to shoot is classified, but the gun is capable of firing a 7.62-, 12.7-, 14.5-, 23-, or 30-mm anti-aircraft round. If the test works as planned, the gun will fire 0.0012 second before the helicopter’s pitch control link spins into its sights, enabling the projectile, traveling at 2,510 feet per second, to smash into its laser-painted bull’s-eye. High-speed video cameras will record the shot, allowing Manchor and his team to analyze what happens as the bullet finds its mark.
Such sacrifices are routine at China Lake, where combat aircraft both old and new are methodically destroyed by guys like Manchor. The tests have changed the way airplanes and helicopters are designed and have enabled pilots to get safely home in aircraft riddled with holes. “We lost 5,500 helicopters and airplanes in Vietnam,” says Robert E. Ball, Distinguished Professor, Emeritus, at the Naval Postgraduate School in Monterey, California, “and in Desert Storm, four [F/A-18] Hornets got hit by infrared [-guided] surface-to-air missiles and all came back.” Ball’s textbook on aircraft survivability is the discipline’s bible.
As effective as live-fire survivability testing seems, however, it is controversial. Contractors and program managers chafe over the time-consuming and destructive testing, which will reveal flaws in expensive hardware only after its development is well under way—sometimes at the stage of full-scale production. Today’s single shot at the MH-60’s pitch control link—a slender rod that adjusts the pitch of the rotor blades—has taken several days to set up. The complete MH-60 live-fire test sequence will take three years. Should serious vulnerabilities be uncovered, key components will have to be redesigned.
Survivability, according to WSL director Jay Kovar, is determined by the answers to a series of three questions: “Can he see me? If he can see me, can he hit me? If he can hit me, can he kill me?” The operation run by Kovar, a strapping former nationally ranked discus thrower, focuses on the last question in the series.
In the opening days of World War II, airplanes were easy to see, hit, and kill. On May 14, 1940, the British lost 23 of 64 Blenhiem and Fairey Battle bombers. And when Germans invaded the Soviet Union a year later, more than 1,400 Soviet airplanes were lost in a single day. As the war ground on, air forces tried to decrease the visibility of aircraft or increase their defenses. “Think about it,” says Robert Ball. “Eight of the 10 men in a B-17 were manning machine guns, and the weight of the guns and ammunition was about twice the weight of the bombs carried.”
By the time of the Vietnam War 20 years later, little had changed. “There was very little attention paid during the design of any aircraft of that era to the damage that enemy guns or guided missiles might do,” says Ball. Increasingly sophisticated high-altitude surface-to-air missiles forced pilots to fly low, which made them vulnerable to small arms fire.
“All of the planes flying in Vietnam were designed for a completely different environment,” says Chuck Myers, the former director of air warfare in the Office of the Secretary of Defense. “The F-4’s mission was to intercept incoming bombers and hit them with Sparrow missiles. The F-105 was designed as a low-altitude nuclear-strike airplane to drop bombs and leave. You didn’t worry about bullets. But those planes were terribly vulnerable. We sent them into the conventional [warfare] morass of Vietnam, and when those SOBs got hit with bullets they came apart.” Ditto with helicopters, which were used in combat in large numbers for the first time in Vietnam. By 1970 some 1,500 had been shot down; their fast-spinning turboshaft engines and light materials proved highly vulnerable to 23-mm anti-aircraft fire.
With losses so high, the Air Force Systems Command dispatched a fact-finding team to Vietnam in 1966 to determine the cause. The directive setting up the mission included the conjecture that aircraft were crashing from catastrophic structural damage. But Dale Atkinson, then an aerospace engineer at the Air Force’s flight dynamics laboratory, thought otherwise. After examining damaged aircraft and talking to surviving crew members and wingmen, Atkinson concluded that airplanes were taking hits and still flying, only to crash because of the fuel system fires and explosions ignited by incendiary ammunition and because of flight control damage.
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.
Between the Super Hornet and a Vietnam-era F-4 Phantom, there is no comparison: A Super Hornet has self-sealing polyurethane fuel tanks located away from ignition sources; short, self-sealing feed lines; redundant fuel pumps; wing tanks lined with open-cell foam; fire extinguishing systems in its dry bays; fire walls between the engine and the auxiliary power unit; redundant flight control computers with four separated electrical signal lines to actuators; and redundant, independent, and separated hydraulic power systems. Despite being 25 percent larger than the earlier F/A-18 Hornet, the Super Hornet’s vulnerable area is the same. Says Tyson: “The F/A-18E/F is the most thoroughly tested and aggressively protected tactical aircraft in the U.S. inventory.”
Yet only 34 of the 622 shots in the Super Hornet survivability test program were shot at a genuine Super Hornet, and even then, the aircraft was never loaded with the munitions it would carry to battle. This testing history highlights an important part of the legislation requiring live-fire testing: The 1986 Live Fire Test Law allows a waiver from realistic, full-up, systems-level testing if it would be “unreasonably expensive and impractical.” Had E/F hardware been used exclusively, according to live-fire test engineers, the tests would have cost several millions more than the $60-million-plus spent on the program, which, they say, met the ultimate goal—understanding the vulnerability of the aircraft’s various systems.
“In order to be granted a waiver,” notes Tim Horton, the head of the Survivability Division at China Lake, “the service, the defense department, and Congress must first approve a comprehensive alternative to a full-up test program that ensures the system will be tested adequately to meet both the spirit and intent of the law. In the case of the F/A-18E/F, a waiver was approved at all levels.”
But to Jim O’Bryon, the waiver process is a loophole, through which every aircraft program has been slipped since passage of the law. “What you want to learn in live fire is what you’d learn on the first day of combat,” says O’Bryon, “but the services hold that if they test all the pieces and use modeling and simulation, that means they’ve tested it all. But it’s not true. Not a single model based on physics exists today that can predict the effect of fire, the number-one killer. And you can’t do user casualty estimates from doing component testing. Can you predict how a car is going to react in a crash by testing the bumper alone? You have to test the whole thing.”
The day after my tour of the boneyard, I meet up with Manchor in the K-2 test pad control room. After the shot is fired, Manchor will try to run the helo at full power for 30 minutes—to simulate the time it would take for a pilot and crew to make it back to friendly territory.
“Okay, starting engine one,” says Chris Fisher, toggling a switch beneath a computer monitor displaying the helicopter engine’s vital signs. One of the five television screens shows the helo in full view, its rotors starting to spin. “Good start on one,” he says. “Moving to two.” The rotors spin faster, and Manchor watches oil pressure and engine temperature rise. Computers have already modeled the effects of this shot at the control link, and real shots have been fired at identical links under load in a static test stand, but those tests don’t show what this test will: what happens in response to a hit when all the forces are at work on the MH-60 in a hover. “We want to see if it fails, and if it fails gracefully or catastrophically,” says Manchor. A graceful failure means that even if it breaks, nothing else happens and the helicopter continues to fly.
The possibility of a catastrophic failure is the reason we’re hunkered down behind steel plates. The link could fail and start a cascade of other, far more deadly failures. Tests on the AH-1 Cobra are a classic example. Shots at the rotor blades and rotor drive controls under static load produced no surprises. But the results were very different when in 1996 the WSL conducted the first test of fast-moving rotor blades and rotor-drive train components while the Cobra was strapped under full power in a hover—a helicopter’s most stressful flight envelope. (The test was conducted not to teach the engineers how to improve the survivability of the helicopter but to develop methods for testing rotor components.) A video of the test shows shots at the end of the blades taking out chunks but affecting no other part of the helicopter; a shot near the rotor root, however, caused the rotor system to start vibrating, and in milliseconds the blades, traveling at 500 mph, sliced through the helo’s tail while the rotor mast transmission went flying 600 feet. One shot and the Cobra was dead.
In a few minutes Fisher pushes the helo to full power and lifts it off. Air bags atop and below four attach points deflate slightly, leaving the MH-60 in a hover. When Manchor sees the red dot of a gun-mounted laser reflecting off a piece of tape on the control link, which is spinning at some 250 revolutions per minute, he nods. “Start sequence,” says Tim Taylor, who is operating the firing system. “Five, four, three, two, one…”
Exactly what happened 0.0012 second later is classified, but Manchor will say that the tests showed “nothing unexpected,” and later, at the China Lake boneyard, I can see from a distance that the MH-60 is intact.
Over the next three years Manchor’s tests will grow potentially more destructive (when he starts shooting the rotors themselves, for example), and it seems hard to fault their realism. Then again, this is a helicopter, which is expected to fly into the kind of threats it’s being tested against. What worries people like Chuck Myers and Jim O’Bryon is that new stand-off precision weapons and low-observable technology may make people think they’ll never get hit, undermining the work at China Lake. “People on [the Joint Strike Fighter] say the plane will never have to fly lower than 15,000 feet,” says Myers. “But the day will come when it’s daylight and overcast, and you’ve got troops fighting other troops in jungles or forests or a city, and you’ll have to. In peace people think you’ll never get hit. But I flew B-25s in World War II and got hit. I flew F-9s off carriers in Korea and I got hit. If your testing causes improvements that extend the time you can stay with your aircraft for three to 10 minutes, man, that’s a big thing!”
Just how big was proven in early March, when U.S. and Afghan forces attacked al Qaeda and Taliban holdouts in one of the biggest battles of the Afghan war. Seven Apache helicopters provided close air support. The Apache had been subjected to—and redesigned based on—live-fire testing. All seven helicopters were hit. And all seven managed to limp home.