Using charts on an easel, McCorkle described how the accident had unfolded. He didn’t name any of the pilots, but he explained that Wright and Bianca had missed their 3,000-foot checkpoint, forcing Brow and Gruber to follow in what none of the pilots seemed to sense was a pellmell descent. McCorkle’s third chart traced Brow’s speed and altitude over the last seconds of the flight, as reconstructed from his Osprey’s Crash Survivable Memory Unit, a device that records airspeed, altitude, and other data. Six seconds before impact, McCorkle noted, the Osprey was 350 feet high and traveling at 41 knots. One second before it hit the ground, it was at 210 feet and 30 knots. “In summary, the data shows that the mishap aircraft was in a high rate of descent at a relatively low forward airspeed,” McCorkle said. “These characteristics can lead to a condition known as power settling, or vortex ring state.”
With that, McCorkle introduced a new, and for many people occult-sounding term into the debate over the Osprey. “Vortex ring state” was esoteric not only to the general public but in the aviation world as well. McCorkle had never heard of it himself until he saw the report on the accident at Marana. It was a term from fluid mechanics, an expression even an aeronautical engineer could go a career without hearing very often. Vortex ring state described a condition a rotor could get into as a result of what Navy and Marine Corps pilots called “power settling” and Army and Air Force pilots knew as “settling with power.” What it all amounted to was a way to describe a rotor that was no longer creating thrust and lifting as it should because it was descending into its own downwash too quickly.
A rotor creates thrust both by pushing air downward and by pulling air through the “rotor disk,” the circle a rotor’s blades describe as they rotate. At the tips of the blades, some downwash circles back over top of the rotor disk and is pulled back through. This disturbed air interferes with a rotor’s ability to create thrust only minimally—unless the rotor descends into its own downwash at the same velocity the downwash is moving. In that case, most or all of the downwash recirculates through the rotor disk rather than racing downward faster than the rotor and creating thrust. The downwash is now churning in a “vortex ring,” an air flow pattern seen in smoke rings, and the rotor has entered “vortex ring state.” When a rotor goes into vortex ring state, it no longer creates the thrust it should, and the aircraft begins to descend faster than the pilot wants.
When an aircraft descends too quickly, a pilot’s natural tendency is to add power to arrest the descent, but in vortex ring state, adding power produces the opposite of the desired effect. In a rotorcraft, adding power also adds pitch to the rotor blades, increasing the angle at which they hit the air. Adding power and pitch to a rotor in vortex ring state only creates more disturbed air and pulls it back through the rotor disk faster. Instead of flowing as it should and creating thrust, the air begins bouncing in and around the rotor disk chaotically and the aircraft loses lift even faster. Helicopter pilots are taught about the hazard and told that the best way to get out of it is to reduce power to slow the rotor while flying into “clean air” by tilting their helicopter’s nose forward. That tilts the rotor forward and increases forward airspeed. Without sufficient altitude, though, there may be too little time to do that, so pilots are urged simply to steer well clear of vortex ring state by never descending too quickly at slow speeds. It’s the rotary wing aviation equivalent of an ancient cartographer writing on a map “Here Be Dragons.” Helicopter pilots learn the rule and avoid that edge of the flight envelope out of habit. They simply don’t go there.
The combined rate of descent and speed at which any particular rotor-craft might go into vortex ring state depends on various factors—the size and shape of its rotors, its flying weight, wind conditions, etc. The rule of thumb for most helicopters, though, is to avoid descending faster than 800 feet per minute when flying forward at 40 knots or less. Where the actual line existed for the Osprey was something the program’s developmental test pilots hadn’t determined, though hundreds of test flights to explore that part of the Osprey’s envelope had been planned. Nolan Schmidt, the Osprey program manager and a Marine Corps colonel at the time, told me years later that those tests were scrapped in 1998 to save time and money. The Navy Department was going to cut the Osprey program’s budget for the coming fiscal year by $100 million, Schmidt said. After consulting with the Boeing engineer in charge of flight-testing, Philip Dunford, Schmidt said, the program managers decided they could save about $50 million and a lot of time if they didn’t do all the tests planned for the Osprey at high rates of descent. A few tests already done had indicated that the Osprey could safely descend at 1,200 feet per minute below 40 knots airspeed anyway, so Navair and company managers decided to simply adopt the standard rule for helicopters. It was enough to know there were dragons lurking beyond a descent rate of 800 feet per minute at 40 knots or less, so why test? “There was no practical need for any rotorcraft that we knew of to have to exceed that boundary anyway,” one of the Osprey’s developmental test pilots in those days told me. The flight clearance placard setting the limits on how the MOTT could fly the Osprey simply adopted the standard from helicopter flight manuals. “Avoid descent rates of 800 fpm [feet per minute] or greater at airspeeds less than 40 KCAS,” it said, “KCAS” being the abbreviation for “knots-calibrated air speed.” Precisely what might happen if a pilot flew beyond that edge of the envelope wasn’t spelled out in the MOTT’s flight clearance placard, but there was no need to go into detail. The rule was labeled a “Warning,” which meant failing to observe it risked loss of the aircraft and death. For pilots, “Warning” is the flight manual equivalent of a skull and crossbones.
At his May 9 news briefing, McCorkle was asked whether the Osprey that crashed had been “descending within the flight envelope.”
“He was descending over a thousand feet per minute,” McCorkle said, noting that the recommended limit was no more than 800 feet per minute at 40 knots or less. Why the pilot had descended so fast was still being studied, McCorkle said. The right rotor of the Osprey, he added, might have gone into vortex ring state only when the pilot moved his control stick to the right four seconds before the crash. “I think that that’s probably what caused it,” McCorkle said.
“Is it correct to say that pilot error is to blame for this accident?” a reporter asked.
“No, it’s not correct to say that,” McCorkle said. “I would really appreciate it if you wouldn’t speculate on that until after the mishap board has reported out. We feel like we have enough information to say that it was not mechanical. There are a lot of things the board is looking at. And why was the pilot at this rate of descent? Why was he in this position at this time? And it would be very inappropriate at this time to say that it was pilot error.”
The main thing McCorkle wanted people to understand was that the crash wasn’t being blamed on a flaw in the Osprey. Developmental test pilots at Pax River were going to do a full range of tests to explore where the edge of the Osprey’s envelope for going into vortex ring state lay, he said. Meanwhile, OPEVAL would go on. “We have waited really a heck of a long time to put the airplane back into the air,” McCorkle said.
* * *
McCorkle was back in the Pentagon press briefing room on July 27, 2000, to announce the final results of the Marana investigation. This time, cameras were barred. When CNN Pentagon correspondent Jamie McIntyre protested that newspaper reporters would be allowed to quote McCorkle by name but TV reporters wouldn’t be able to use videotape of him speaking, McCorkle told McIntyre the ban on cameras was “strictly my decision.” He really had nothing new to say about the crash beyond the fact that the investigation was closed, McCorkle said. “In fact, I did not desire to do this.” McCorkle said others, whom he didn’t name, had told him making no comment on the final results might lead to suspicion the Marine Corps was trying to hide something, so he had agreed to do a “roundtable” with reporters. “It won’t break my heart if nobody writes a word in the newsp
apers except to say, you know, the investigation is complete,” McCorkle said.
Then McCorkle explained why he was so reluctant to go on camera. He had spent more than two hours that morning with the widow of the pilot whose Osprey had crashed. He had spent an hour on the phone the night before with the copilot’s widow. “I personally just feel like it’s just time to put it to bed, which I wanted to do off the record,” McCorkle said.
Beyond being distraught at the loss of their husbands, Trish Brow and Connie Gruber had been upset for weeks about news coverage of the crash. Much of it had implied, some had outright said, that the cause of the crash was “pilot error.” The widows resented the idea that their husbands were to blame. McCorkle had always refused to use the term pilot error, saying it would be illegal for him to declare a cause until the mishap board had finished its investigation. Now Marine Corps public affairs officers had given reporters a news release attributing the crash to “human factors.”
McCorkle began the briefing by reading a statement that said “an unexpected tailwind and the pilot’s extremely rapid rate of descent into the landing zone created the conditions that led to the accident. Although the report stops short of specifying pilot error as the cause, it notes that the pilot of the ill-fated aircraft significantly exceeded the rate of descent established by regulations for a safe flight.” The statement omitted all the pilots’ names but described what had gone wrong in far more detail than McCorkle had given in his earlier briefings: how the lead aircraft, flown by Wright and Bianca, had begun the descent into Marana too high; how Brow and Gruber had followed them; how none of the pilots seemed to have realized they were descending dangerously fast; how Brow’s attempt to slide his Osprey to the right before landing probably had put the rotor on that side into vortex ring state, causing the aircraft to roll out of control.
When he started taking questions, McCorkle also revealed, again without using names, that he had suspended Wright’s and Bianca’s designations as “tiltrotor aircraft commander” for six months. To get the designation back, each would have to requalify by taking tests and check rides. McCorkle wasn’t going to blame any of the pilots for the crash. The pilot of the lead aircraft—Wright—should have waved off and gone around, he said, if not earlier, then at the very latest when his copilot—Bianca—told him they were “a little high” and said it was Wright’s call whether to try to land or wave off. “Now, did he cause Dash Two to crash?” McCorkle said. “No, because Dash Two could have said, ‘I’m going around,’ you know, ‘whether you want to go around or not.’ ” There were “several links in the chain” that led to the accident, McCorkle noted. “And none of them—nothing—was ever done with intent.” All four pilots involved had behaved professionally. This wasn’t an accident “caused by cowboys,” he said, though mistakes had been made.
When a reporter asked if anything in the accident report would prevent the Osprey going into Full Rate Production, McCorkle brightened. “I’m really happy that you asked that question,” he said. The MOTT had started flying OPEVAL missions again in late May and finished in mid-July, using a revised flight clearance that forbade descending at more than 800 feet per minute anytime the Osprey’s nacelles were tilted upward beyond 80 degrees. The Osprey had “met or exceeded all the key performance parameters,” McCorkle said. “We’re hoping for the Milestone III decision for full rate development to be sometime in October.”
CHAPTER TEN
YOU WANT IT BAD, YOU GET IT BAD
On the last day of his life, December 11, 2000, Lieutenant Colonel Keith Sweaney rose before the sun, had coffee with his wife, Carol, and was on his way to work by 5:30 a.m. Most days the MOTT leader drove a dozen miles from his Stafford, Virginia, home to his office at Quantico Marine Corps Base, where his headquarters had moved after OPEVAL ended in July. Today, though, Sweaney wheeled his spanking new silver Mitsubishi Eclipse sports coupe onto Interstate 95 and hotfooted it south to New River Marine Corps Air Station on the North Carolina coast. He covered the 305 miles in a brisk five and a half hours.
If Sweaney was in a hurry to get to New River, he had good reason. His orders were to spend a week there preparing for his next prestigious assignment. In a couple of months, Sweaney was scheduled to leave the MOTT and take command of the Marine Corps’ first operational Osprey squadron at New River. The Pentagon hadn’t approved Full Rate Production yet, but the Marines hoped it would soon, clearing the way for them to put the Osprey into service at last. “I’m confident it should be approved, and I’ve seen nothing to lead me to believe that it won’t,” General Jim Jones, the commandant, had told the Associated Press a few days earlier. Sweaney was the logical choice to head the new squadron, the most experienced Osprey pilot in the Marine Corps, but he needed refresher training. Over the past five months he had spent most of his time wrapping up OPEVAL and writing the MOTT’s report on the testing. The report wasn’t done until October, when Sweaney gave a briefing on it to Philip Coyle, the Pentagon’s director of operational test and evaluation. The MOTT’s Ospreys had been sent to New River, so Sweaney hadn’t had much opportunity to fly. This week, he was scheduled to catch up by making five flights in Ospreys assigned to the Marines’ tiltrotor training squadron at New River.
Eager as he was to get back into the cockpit, Sweaney was looking forward even more to leaving behind the pressure-packed job of leading the MOTT through OPEVAL and the trauma of Marana. The unit’s pilots and maintainers had needed time to recover from the shock of the Arizona crash, and their higher-ups hadn’t given them much. The deadline for completing OPEVAL so the Pentagon could rule on Full Rate Production was tighter than ever after the mishap and the resulting delay in the schedule.
The month after the crash, when no one was flying Ospreys, had been hardest for the MOTT. First there were the funerals, then the crash investigation. The MOTT resumed flying in June at China Lake, a 1.1-million-acre naval air weapons station in the western Mojave Desert of California. Most of the pilots and crew chiefs didn’t hesitate to fly again after vortex ring state was declared the cause of the Marana crash, but some did. Some crew chiefs agreed to go back up only after Staff Sergeant Julius Banks, who had manned the rear ramp in the lead Osprey at Marana, said he would fly again. Banks, thirty-six, was the noncommissioned officer in charge of the flight line for the MOTT. A lot of younger crew chiefs looked up to him.
Many Marine Corps ground troops were wary of the Osprey after Marana, a fact General Jones knew. Jones, a career infantry officer—not an aviator—who had fought in Vietnam, understood how the grunts felt. To try to ease their minds and show the rest of the world he still had confidence in the tiltrotor, Jones went to China Lake on June 17 and flew on the first Osprey to carry passengers since Marana. He even took his wife aboard with him. Top executives from Bell Helicopter and Boeing rode along, too. “If there was the slightest doubt—I mean the slightest doubt—we would not have done this today,” Jones told reporters afterward.
After OPEVAL, the MOTT shrank. Its Air Force contingent moved to Edwards Air Force Base in California to continue testing that service’s version of the Osprey. Bell and Boeing had delivered seven more Low Rate Initial Production Ospreys that year. During the summer, six of the nine remaining Marine pilots in the MOTT, and a number of its maintainers, transferred to the Osprey training squadron at New River, VMMT-204. The Marines needed to train a lot of mechanics, pilots, and crew chiefs if they were going to have enough to field the Osprey in 2001.
With a presidential election campaign going on, the storm in the media and on Capitol Hill that had seemed to threaten the Osprey in the weeks after Marana died down almost as quickly as it had blown up. There were still rumblings of suspicion about how safe the tiltrotor really was, though. Some aeronautical engineers were beginning to study whether the side-by-side placement of the Osprey’s rotors created some vulnerability to vortex ring state that didn’t exist with helicopters. Developmental test pilots at Pax River were writing up plans to start test
ing that later in the year. Meanwhile, the Marines and their allies were taking steps to shore up the Osprey’s political support. At Representative Curt Weldon’s urging, Defense Secretary William Cohen let the Marines send an Osprey to the Republican National Convention in Philadelphia from July 31 to August 3, putting it on display along with other military equipment at the former Philadelphia Naval Shipyard. More than a hundred members of Congress were staying in housing on the shuttered base during the convention, something else Weldon had arranged. A few reporters wrote stories about whether it was proper for the Pentagon to inject itself into electoral politics that way, but Weldon knew it was a good way to get lawmakers interested in the Osprey again.
Other Osprey news that summer wasn’t so good. In August, the Pentagon inspector general’s office issued a report questioning whether the Osprey was ready for Full Rate Production. The report said the Navy Department had let the Osprey go into OPEVAL before it was ready, waiving twenty-two requirements that should be tested before the aircraft was fielded. Some waivers had to do with the Osprey’s limited flight envelope, which banned pilots from doing “air combat maneuvers” during OPEVAL. Most involved what insiders called the “ilities”—reliability, availability, maintainability—measures of how hard it would be for the Marines to keep the Osprey ready to fly in the field. During OPEVAL, the Osprey had performed far below its goals for availability. Even with the waivers, and even excluding the maintenance and parts problems that forced the MOTT to stop flying from mid-December 1999 until February 22, 2000, the Osprey’s availability rate during the tests had fallen well short of its targets. The goal for keeping all four of the LRIP Ospreys the MOTT used “mission capable,” meaning they could fly even if some systems weren’t working, had been a daily average of 82 percent. The actual mission-capable rate during OPEVAL was 57 percent. The goal for having all four Ospreys “full mission capable,” meaning every system on them was functioning, had been 75 percent. The full-mission-capable rate during OPEVAL was a mere 11 percent. The MOTT’s final report said the Osprey’s availability rate was “unsatisfactory.”
The Dream Machine Page 37
