The Dream Machine

by Richard Whittle

  Developmental test pilots had done some autorotation flight tests in the Osprey during that period, descending at high altitude with the engines idling and disconnected from the rotors. The rotors autorotated, but the pilots concluded it was too dangerous to try landing the Osprey that way. Even landing a helicopter by autorotation is tricky. To do it successfully, a pilot has to let the helicopter float toward the ground, then pull up at the last moment and flare to a landing. This requires milking the last bit of lift out of the rotor or rotors, whose inertia has kept them turning without engine power. The relatively small size and large twist of the Osprey’s proprotors gave it a high rate of descent in autorotation and too little inertia to provide the necessary lift at the end of such a landing, the pilots found. Even so, recalled one former Osprey developmental test pilot, in the late 1990s there were “a number of people at Bell and Boeing who were making claims” that the Osprey could autorotate to a safe landing. “Us test pilots were going, ‘No, you can’t. It’s a stunt in the simulator,’ ” this pilot said. “When you make a survivable one in a simulator, you make nine of them that aren’t.” The maneuver was so tricky, test pilots would bet beers on who could do it in the Osprey simulator without crashing.

  Still, the test pilots agreed with those running the program that while the Osprey’s inability to autorotate to a landing like a helicopter was a disadvantage, it wasn’t a crippling one. Given the reliability of modern turbine engines, they calculated that the odds of losing both in ordinary flight were astronomical. There was certainly a chance an Osprey might have an engine shot out while coming into a “hot” landing zone. With the nacelles separated by about forty-five feet, though, having both engines shot out at once was unlikely, they concluded, and the interconnecting driveshaft would let one engine power both rotors so a pilot could land in helicopter mode safely even with one engine out.

  Rivolo didn’t buy such arguments. When he found out just before the Osprey’s Operational Evaluation began in 1999 that Navair had long ago dropped the idea of doing autorotation landings in flight tests, he told me, “At that point is when I really got angry.”

  After the April 2000 crash at Marana, Rivolo also began to see vortex ring state as a reason the Marines shouldn’t fly troops into combat in the Osprey. Like a lot of pilots and even aeronautical engineers, Rivolo didn’t know much about vortex ring state then. The phenomenon had been recognized for decades, but little research had been done on it, for a couple of reasons. First, it was generally agreed that helicopter pilots could steer clear of vortex ring state by never descending too quickly at slow forward speed—no faster than 800 feet per minute at 40 knots or less was the standard limit. Secondly, if a helicopter should go into vortex ring state, the pilot usually recognized it right away—the machine would shudder and shake—and it was relatively easy to fly out of, unless the aircraft was too close to the ground. The pilot just had to tilt the helicopter’s nose forward and fly into “clean air” so the rotor could stop churning in its own downwash. The way the Osprey at Marana had snap-rolled to the right when it went into vortex ring state, however, led Rivolo to suspect the phenomenon was more dangerous for a tiltrotor because of its side-by-side rotors.

  After Marana, Rivolo looked around for an expert who could help him understand vortex ring state. He found J. Gordon Leishman, a forty-two-year-old professor of aerospace engineering at the University of Maryland, who had studied the intricacies of helicopter rotors and the air flows that affect them. Leishman was the author or co-author of dozens of scholarly papers on the topic and had written a book called Principles of Helicopter Aerodynamics, published in May 2000 by Cambridge University Press. Rivolo offered Leishman an IDA contract to run calculations on the wakes of the Osprey’s rotors using a computer model Leishman and his graduate students had devised. The goal was to see how the air currents the rotors created might affect the Osprey’s risk of going into vortex ring state. Leishman concluded that the downwash and other air flows around the Osprey’s rotors collided with each other in ways that were different from a helicopter’s and made the tiltrotor’s aerodynamic behavior in descending flight hard to predict.

  Armed with Leishman’s findings, Rivolo tried but failed to persuade Pentagon test director Phil Coyle to declare in his November 2000 report on the Osprey’s Operational Evaluation that the Osprey was “not operationally suitable”—a conclusion Rivolo knew might keep the Marines from getting the program through Milestone III anytime soon. Coyle’s office also refused to let Rivolo present his views to the Blue Ribbon Commission. A few months later, however, Rivolo and Leishman were two of the experts the NASA committee on the Osprey invited to deliver presentations. Spivey didn’t like what either one said.

  Rivolo had come up with his own theory of vortex ring state by then, one that went well beyond Leishman’s conclusions. Rivolo believed from his own experience that, despite rules against it, pilots were apt in combat to descend too quickly at slow airspeed. He also told the NASA panel there were other ways a rotorcraft could get into vortex ring state. It could happen if a rotor were hit by a gust of wind from underneath while hovering over a mountainside, he said. It could happen during the flare of an autorotation if the pilot’s timing were off. It could happen anytime the flow of air from below a rotor equaled its downwash, which was most likely to occur close to the ground, he argued. A helicopter, with its rotor or rotors over the fuselage, could recover nine out of ten times in such circumstances but the Osprey would always crash, Rivolo asserted. This was so, he argued, because the side-by-side placement of its rotors would cause the Osprey to snap roll if one of them went into vortex ring state. Even though helicopters could get out of vortex ring state fairly easily, he added, his research suggested the phenomenon was the real reason for one out of three helicopter crashes.

  Spivey was aghast. Rivolo was saying the Osprey was a death trap. His theory of vortex ring state causing one in three helicopter crashes was also novel, to say the least. “Rex, what kind of proof do you have of what you just said?” Spivey asked him at the NASA meeting. “I see every accident that happens to rotorcraft in the United States—that comes across my desk every day. I know what I’ve been told, I know what I see in the accident reports, and I’ve never seen anything like this. What is your authority to say that?”

  Rivolo replied that while FAA statistics attributed only 8 percent of major helicopter accidents to vortex ring state, the figure really should include mishaps resulting from failed attempts to autorotate and other hard landings. “I am probably one of the few people in the world who understands vortex ring state,” Rivolo told me. “How do you make a hard landing in a helicopter? A hard landing is because the pilot lost enough power to maintain altitude. That is a vortex ring state. So every single accident the FAA classifies as hard landing is a vortex ring state. And in autorotation, most autorotations end badly because the pilot, at the bottom, enters vortex ring state. And I showed them exactly how that mechanism works.”

  Spivey was relieved to see that the members of the NASA panel and others among its advisers found Rivolo’s theory as far-out as he did. Several told Spivey they were glad he’d challenged Rivolo. Spivey was alarmed, though. Given Rivolo’s position as the IDA expert assigned to the Pentagon Office of Operational Test and Evaluation, Spivey assumed Rivolo had influence in the Pentagon. This is bad, Spivey thought.

  Spivey wasn’t there when Leishman showed the NASA panel his studies of the Osprey’s rotor wash, but he heard about the presentation later. Leishman’s calculations were complex, but he essentially concluded that because the Osprey’s rotors were side by side, they would necessarily fly through each other’s disturbed air in descending flight. The effects hadn’t been adequately studied, Leishman said, and might mean the Osprey could go into vortex ring state for reasons other than an overly rapid descent at slow forward speed—by doing evasive maneuvers to avoid enemy fire when landing in a combat zone, for example.

  When Spivey heard what Leish
man had said, he was nearly as alarmed as he’d been about Rivolo’s presentation. Spivey was sure Leishman was greatly exaggerating the strength and duration of the vortices created by a rotor. “He was talking about how dangerous it was to operate in all those vortices,” Spivey recalled. “Well, heck, helicopters do that all the time.” Spivey was also confident the tiltrotor was less vulnerable to vortex ring state than a helicopter. The few tests done by Osprey test pilots trying to put it into vortex ring state in the fall of 2000 already had suggested that.

  One day while Spivey was still stewing over Leishman’s briefing, he ran into one of the professor’s University of Maryland colleagues and complained about Leishman to him. Leishman “wasn’t being scientific,” Spivey told the man. Leishman was outraged when he heard what Spivey had done. Leishman had made a few dollars doing his study for IDA, but his interest in the Osprey was scientific. He wondered why Bell didn’t invite him down to Fort Worth to talk about his research if it bothered them, rather than snipe at him behind his back. At the same time, he knew billions of dollars were at stake for the company.

  Spivey wasn’t thinking about money. To him, the stakes were higher, and his faith in the Osprey had never been shaken. Spivey was sure the Osprey’s crashes could have been avoided, and such accidents could be prevented in the future, with better training. He was certain the Osprey could be made safe, and that it would save lives once it got into service. Its speed would let Marines and special operations troops outmaneuver and defeat their enemies with fewer casualties. Its speed would get those wounded to medical treatment fast enough to save them. “The fact that we lost some along the way is excruciating, but that doesn’t make you walk away from something you believe has the promise of saving more lives downstream,” Spivey reasoned. “You’re going to have mistakes along the way, unfortunately. All aircraft development has its price. Unfortunately, it comes with the territory.”

  Spivey had criticized Leishman to the professor’s colleague because the dream Spivey had devoted his life to was in danger. If he had to bite and kick a little to save it, he would.

  * * *

  The NASA committee concluded that there were “no known aeromechanics phenomena that would stop the safe and orderly development and deployment of the V-22.” The panel urged the Pentagon to resume flight-testing “without delay,” especially tests to verify how vulnerable the Osprey was to vortex ring state. The committee said the available evidence suggested the Osprey was less apt to go into it than a helicopter, based on the tests conducted before the New River crash had grounded all Ospreys. “A tiltrotor aircraft, when deep within the vortex ring state region, can encounter uncommanded roll motions due to its side by side proprotor configuration,” the panel acknowledged, but the tests suggested it was just as easy for an Osprey to get out of it. A pilot simply needed to tilt the Osprey’s rotors forward and fly into “clean air.”

  As for autorotation, the NASA panel acknowledged that for an Osprey flying in helicopter mode, “a full power-off landing may not be practical.” The preferred way for an Osprey to land with its engines out, it said, would be to tilt the rotors forward and glide to a landing airplane-style. The panel said the Osprey shouldn’t be required to autorotate.

  The NASA committee also urged the Pentagon to provide Navair more money, more people, and more Ospreys to test. “The panel believes that when fielded, the V-22 will truly revolutionize the role of transport aircraft in the defense of our country,” the report said.

  The committee’s chairman, Henry McDonald, briefed Undersecretary of Defense Pete Aldridge on the panel’s findings on August 14. The next day, Aldridge met with reporters at the Pentagon. “I’m going to reserve judgment,” he told them when asked about the Osprey. “The plan, assuming we proceed, is to resume flying sometime early next year.” The Osprey was “a very complicated airplane,” Aldridge said. “There are lots of uncertainties regarding the flying qualities. There’s still some uncertainties regarding reliability improvements. There’s uncertainty regarding how long we actually will have to keep it in flight test before we continue back on production. It’s just a very difficult problem to decide upon, and we are not going to decide quickly.”

  * * *

  On September 11, 2001, less than a month after the NASA committee finished its work, Al Qaeda terrorists hijacked four civilian passenger jets and slammed two into the World Trade Center in New York and one into the Pentagon. The fourth plane crashed in rural Pennsylvania after passengers stormed the cockpit. On October 7, U.S. ships and planes launched missile and air strikes on the Islamic fundamentalist rulers of Afghanistan, the Taliban, for harboring Al Qaeda leader Osama bin Laden. U.S. special operations troops were already in Afghanistan, aiding the Taliban’s enemies. The world was anticipating a full-fledged U.S. invasion. Four days after the U.S. air strikes in Afghanistan began, Representative Curt Weldon told the Fort Worth Star-Telegram that he was going to try to get Congress to approve extra funding for the Osprey. With its high speed and vertical takeoff and landing capability, he said, the Osprey would be perfect for ferrying U.S. troops around Afghanistan’s vast and rugged terrain. “That bird is ready to go and we should get it up in the air,” Weldon said. The causes of the Osprey crashes the year before already had been largely fixed, Weldon asserted. The Osprey could be ready to go to war in thirty to sixty days.

  Those following the Osprey’s travails could only roll their eyes. They knew Weldon couldn’t be more wrong. Navair, Bell-Boeing, and the Marines were only beginning to sort out how to rehabilitate the Osprey as the Blue Ribbon Commission and the NASA panel had said they should. Blue Ribbon Commission member Norman Augustine told the Star-Telegram it would take at least two years.

  Weldon’s wildly optimistic description of the Osprey’s status was part posturing. The annual defense bills were moving through Congress, and Weldon wanted to give his colleagues as many reasons as possible to keep building Ospreys. His remarks, though, reflected how much 9/11 had changed the defense debate in Washington. Earlier in the year, the key defense issue in Congress had been how to hold defense spending down. Now the nation was at war and Congress wanted U.S. troops to have whatever weapons could help them win. When the defense bills were finished that December, Congress had appropriated $1.3 billion to build eleven new Ospreys in the next fiscal year and fund the redesign and retesting Navair had told Aldridge it wanted to do. The legislation also required Aldridge to submit a report to Congress thirty days before the Osprey flew again describing what had been done to correct the flaws in its hydraulics and flight control software and what steps Navair had taken to implement the Blue Ribbon Commission’s recommendations.

  The defense bills cleared Congress and went to Bush for his signature on December 13. Four days later, Harry Dunn read in the trade newsletter Inside the Navy that Aldridge was expected within days to approve Navair’s plans to redesign and retest the Osprey. In Aldridge’s mind, the decision had been a close one. It was going to cost a lot to redo what Aldridge saw as Bell’s “sloppy engineering” of the Osprey’s nacelles, which had let its wire bundles rub its hydraulic lines. It was going to cost a lot to find out whether the Osprey was excessively vulnerable to vortex ring state and less agile than it needed to be for combat. He wasn’t sure it would be money well spent. A few months back, though, the commandant, General Jim Jones, had come to Aldridge’s office and urged him to keep the Osprey alive. The Marine Corps needed it, Jones said.

  All that summer and fall, Harry Dunn e-mailed Aldridge regularly, often daily, passing on evidence to support what Dunn called the “findings” of the “Red Ribbon Panel.” The Osprey’s rotors were inherently flawed, Dunn kept telling Aldridge. The Osprey would never be able to do the maneuvers required in combat. If it did, its rotors would stall, or be damaged by the G’s—gravitational forces—such flight would put on them, Dunn predicted. The Osprey’s rotor downwash was so powerful it would be unable to land in dusty conditions because the pilot would be blinded by the
cloud of dirt the rotors would kick up, Dunn argued. The fixes recommended by the Blue Ribbon Commission and NASA would be a waste of time and money. Dunn’s e-mails, which often lapsed into diatribe, also accused Bell-Boeing and Navair of hiding engineering information from their Pentagon overseers. He urged Aldridge to have the Defense Department inspector general investigate them.

  Aldridge had found some of Dunn’s arguments persuasive at first, but he soon wearied of Dunn’s constant barrage and stopped reading his e-mails. Now Dunn sent Aldridge another, which included the scoop by Inside the Navy’s Christopher Castelli reporting that Aldridge had approved a new program of flight tests. “It is hard and sad to conclude that all of my personal efforts (leave alone the dozens of others who did a lot of the work) have come to a total failure,” Dunn wrote. If the report in Inside the Navy was accurate, Dunn said, the “140++” combat and test pilots he had been working with were going to “pull together a bunch of our findings and reports and facts and charts and dump them out onto the media.” Dunn warned that Aldridge might soon “be reading about your inabilities to make solid, fact based decisions.”

  Aldridge confirmed his decision to let the Osprey program go forward in a December 21 Pentagon news conference. He also left the door open to canceling the Osprey later. The Blue Ribbon Commission and the NASA panel had found no fundamental flaws in the tiltrotor, but “I personally still have some doubts,” he said. The flight test plan he was approving would last two years and be much more comprehensive than Navair originally had planned. Vortex ring state was only one thing to be tested. The Osprey’s flight characteristics over a windy ship deck, while hovering, while landing in dust and debris also would be tested, along with its ability to do combat maneuvers, fly in formation, and refuel in midair. “The flight test effort will be event-driven, as opposed to schedule-driven,” Aldridge said. “We will not be driven by trying to accomplish something within a certain period of time. The Secretary of the Navy and I will do periodic reviews of the flight test results to assess progress.” In the meantime, production would be held to eleven Ospreys a year. His concerns, Aldridge said, were how stable an aircraft with rotors on its wingtips could be, and whether the Osprey’s proprotors, with their relatively small diameter, could produce the thrust needed and handle the stresses that went along with flying in combat. He wasn’t sure, he added, that the Osprey would pass its tests.