"I went to law school," he reminded her.
"Bernoulli's principle says the faster a gas moves, the lower its pressure. So the pressure within a moving stream is less than the air surrounding it" she said. "Since air moves faster across the top of the wing, it creates a vacuum which sucks the wing upward. The wing is strong enough to support the fuselage, so the whole plane is lifted up. That's what makes a plane fly."
"Okay.. ."
"Now. Two factors determine how much lift is created - the speed the wing moves through the air, and the amount of curvature. The greater the curvature, the greater the lift."
"Okay."
"When the wing is moving fast, during flight, going maybe point eight Mach, it doesn't need much curvature. It actually wants to be almost flat. But when the aircraft is moving slower, during takeoff and landing, the wing needs greater curvature to maintain lift. So, at those times we increase the curvature, by extending sections in the front and back - flaps at the back, and slats at the leading edge."
"Slats are like flaps, but in the front?"
"Right."
"I never noticed them before," Richman said, looking out the window.
"Smaller planes don't have them," Casey said. "But this aircraft weighs close to three-quarters of a million pounds, fully loaded. You've got to have slats on a plane this size."
As they watched, the first of the slats moved outward, then tilted down. The men on the wing stuck their hands in their pockets and watched.
Richman said, "Why are the slats so important?"
"Because," Casey said, "one possible cause of 'turbulence' is slat extension in mid flight. Remember at cruise speed, the wing should be almost flat. If the slats extend, the plane may become unstable."
"And what would make the slats extend?"
"Pilot error," Casey said. "That's the usual cause."
"But supposedly this plane had a very good pilot."
"Right. Supposedly."
"And if it wasn't pilot error?"
She hesitated. "There is a condition called uncommanded slats deployment. It means the slats extend without warning, all by themselves."
Richman frowned. "Can that happen?'
"It's been known to occur," she said. "But we don't think it's possible on this aircraft." She wasn't going to get into the details with this kid. Not now.
Richman still frowned. "If it's not possible, why are they checking?'
"Because it might have happened, and our job is to check everything. Maybe there's a problem with this particular aircraft. Maybe the control cables aren't properly rigged. Maybe there's an electrical fault in the hydraulics actuators. Maybe the proximity sensors failed. Maybe the avionics code is buggy. We'll check every system, until we find out what happened, and why. And right now, we haven't got a clue."
Four men were squeezed into the cockpit, hunched over the controls. Van Trung, who was certified for the aircraft, sat in the captain's seat; Kenny Bume was in the first officer's seat on the right. Trung was functioning the control surfaces, one after another - flaps, slats, elevators, rudder. With each test, the flight deck instrumentation was verified visually.
Casey stood outside the cockpit with Richman. She said, "You got anything, Van?"
"Nothing yet," Trung said.
"We've got diddly-squat," Kenny Burne said. "This bird is cherry. There's nothing wrong with this plane."
Richman said, "Then maybe turbulence caused it, after all."
'Turbulence my ass," Burne said. "Who said that? Is that the kid?"
"Yes," Richman said.
"Straighten the kid out, Casey," Burne said, glancing over his shoulder.
'Turbulence," Casey said to Richman, "is a famous catchall for anything that goes wrong on the flight deck. Turbulence certainly occurs, and in the old days, planes had some rough times. But these days turbulence bad enough to cause injuries is unusual."
"Because?"
"Radar, pal," Burne snapped. "Commercial aircraft are all equipped with weather radar. Pilots can see weather formations ahead and avoid them. They've also got much better communications between aircraft. If a plane hits rough weather at your flight level two hundred miles ahead of you, you'll hear about the sigmet, and get a course change. So the days of serious turbulence are over."
Richman was annoyed by Burne's tone. "I don't know," he said "I've been on planes where turbulence got pretty rough - "
"Ever see anybody get killed on one of those planes?"
"Well, no..."
"Seen people thrown from their seats?"
"No..."
"Seen injuries of any kind?"
"No," Richman said, "I haven't"
"That's right," Burne said.
"But surely it is possible that - "
"Possible?" Bume said. "You mean like in court, where anything is possible?'
"No, but - "
"You're a lawyer, right?"
"Yes, I am, but - "
"Well you better get one thing straight, right now. We're not doing law, here. Law is a bunch of bullshit. This is an aircraft. It's a machine. And either something happened to this machine, or it didn't. It's not a matter of opinion. So why don't you shut the fuck up and let us work?"
Richman winced, but didn't back down. "Fine," he said, "but if it wasn't turbulence, there'll be evidence - "
"That's right," Burne said, "the seat-belt sign. Pilot hits turbulence, the first thing he does is flash the seat-belt sign, and make an announcement. Everybody buckles up, and nobody gets hurt. This guy never made an announcement"