Haueter was frustrated by the lack of progress. Many clues pointed to the rudder system, but he and Phillips could not find any proof that it had failed. The power control unit not only passed every test, it seemed to have the strength of a superhero. So, in May 1995, Haueter decided they should step back and take a broader look at the plane, instead of just focusing on the rudder. Maybe they would discover some wild idea that would lead them to the solution.
He, Phillips, and Vikki Anderson, the lead investigator for the FAA, flew to Greensboro, North Carolina, and rented a car to drive to Winston-Salem, where USAir had a big maintenance hangar. The tan-colored hangar was big enough to hold three 737s for inspections that USAir called Q checks, the major overhauls where planes were stripped to their frames so mechanics could replace anything that did not meet FAA standards. A 737 got a Q check every 11,000 flight hours, or roughly once every three to four years. It was a great place to look for inspiration because everything in the planes was exposed. The 737s looked like they were naked.
A steady rain fell outside the hangar as they wandered around one of the stripped planes, looking at the maze of cables and wires that were normally hidden by the floorboards and the aluminum skin. They scrutinized the wing, trying to see anything that might have caused the smoke the witness had reported, and crawled into one of the baggage compartments. Phillips was struck by how much older planes smelled like coffee. They carried so many thousands of gallons of coffee over the years that it seemed to permeate everything. It was a familiar, comfortable smell.
They sat in the cramped baggage compartment and talked about the possibility that an obese passenger fell through the floor and landed on the rudder cable—an idea that had been dubbed “the fat guy theory.” Would the fat guy have pulled on the cable enough to move the rudder? Probably not, but it might be worth testing, Phillips said. They looked at the plane’s tail and discussed what might have happened if a bird had struck the vertical fin. Could that have turned the rudder?
USAir mechanics had tagged along to answer questions. “Do you have any ideas?” Anderson asked them. “Is there anything, no matter how far out, that you have noticed about the plane?” They had a few suggestions, but they were all theories that the NTSB had considered before. Anderson went up to the cockpit and sat in one of the seats. She stepped on the rudder pedals, turned the wheel, and moved the control column up and back. She was struck that it was such a simple airplane, about as sophisticated as an old VW Beetle.
She and Phillips went to the wheel wells, where the hydraulic lines converged and where the landing gear was stored in flight. A USAir mechanic who accompanied them was concerned about the vulnerability of the hydraulic lines there. If a tire blew out, it could do serious damage, he said. Boeing had once had screens that protected these fragile components, but the company had stopped using them.
“I’ve always wondered about things being in such a small place,” the mechanic said.
“I have, too,” Phillips said. But he had found no evidence of such an explosion in the wreckage.
They spent lots of time around the tail, looking at the power control unit and how it fit inside the vertical fin. Could a bird have broken through the tail and hit the cables or rods that led to the PCU? Haueter doubted it. The angle of the vertical fin would make it hard for a bird to break through. It would be deflected before it could pierce the skin.
Rain was pouring down as they had lunch at a pub near the hangar and then took a commuter flight back to Washington. It had been a good chance to see the innards of the plane, but they felt no closer to knowing what had happened.
Boeing had a theory about the pilots’ feet. The company wanted to test the damaged pilot seat tracks to determine if they indicated where Emmett and Germano were sitting. The pilots might have been so far from the rudder pedals that they had to stretch to use them. Maybe that caused one of the pilots to push too long and hard on one of the pedals.
The seat tracks, metal strips that allowed the pilots to slide their seats forward and backward, were brought to the NTSB’s metals lab in Washington. Metallurgists inspected the tracks, but they were so mangled that the experts could not find proof of whether the seats were too far back. Besides, the position of the seat was not important, since each pilot had a crank that adjusted the rudder pedals forward and backward, so even when a pilot had the seat back as far as it would go, the pedals could be in the proper place. At six-three, Emmett was so tall that it was logical that he would have his seat back.
Cox felt that Boeing was going to ridiculous extremes to blame the pilots. “Boeing is desperately trying to do anything they can to clear their airplane,” he said. He was resolute that the pilots were not at fault. “I still think it’s a systems problem with the airplane.”
A few days later Cox and the other investigators flew to the NASA-Ames Research Center near San Francisco to take a ride in one of the world’s most advanced flight simulators. The idea—also suggested by Boeing—was to see if Germano and Emmett had been so startled by the wake turbulence that they could not recover the plane.
The NASA vertical motion simulator, or VMS, was part of SimLab, the world’s most advanced laboratory for studying pilots. The lab gave out patches with the simulator’s logo, which had four stars and arrows pointing in every direction. It looked like a recipe for motion sickness.
The VMS resembled a wandering elevator inside a cavernous ten-story building. Like Boeing’s M-Cab simulator, it could be programmed to perform like many different aircraft—fighter planes, big transport jets, even the space shuttle. It felt more realistic than other simulators because the cab could go up and down sixty feet, compared with just a few feet on M-Cab. That gave pilots a better illusion of the ups and downs in a plane. For the Flight 427 test, airsickness bags had been taped to the walls, just in case.
Malcolm Cohen, a NASA expert on the inner ear, had been invited to determine if the pilots had lost their bearings when the plane started to flip. He rode twelve times—several with his eyes closed—and was surprised at how smooth the ride was. He said it was so smooth that the pilots should not have been disoriented. Cox had watched the simulator go back and forth a few times before his turn and said it would be “an E-ticket ride,” like the most thrilling ones at Disney World. He then walked across the ramp, buckled himself into the left pilot’s seat, and put on the headphones. The safety board had brought along the cockpit tape so riders could listen to the crew.
The cab moved down to one side of the big tower, as if the NASA people were getting ready to fire it from a slingshot. The ride began. It was much smoother than M-Cab, without the jerks of the mechanical stops. Again and again, Cox rode the simulator, concentrating on a different element each time. He watched the instrument panel on some rides and looked out the windows on others. The simulator’s windows showed a computerized display of the ground and sky that changed as the plane moved.
He had seen a similar display in Boeing’s M-Cab, but he noticed something new this time. He was surprised at how quickly the plane went nose down and the windscreen filled with the ground. It seemed like the pilots were helpless to do anything. To Cox, it was more evidence that the crew was fighting to survive, but the plane was not responding.
Haueter hardly ever got scared when he flew, but he did get the jitters during a flight in a USAir plane in the summer of 1995. The plane was just like Ship 513, a 737–300. It was approaching Washington National Airport when it hit turbulence. Startled, Haueter sat up straight and quickly looked around to find the horizon through the windows, to see if the wing had rolled down too far. What was going on? Had the plane had a rudder hardover? Unfortunately, the people beside him had pulled down the window shade. He looked out the windows on the other side, but he couldn’t tell how far the plane had rolled. A quick thought flashed through his mind: Wouldn’t it be ironic if the chief investigator for 737 crashes was killed in one?