“What do you mean, ‘feature,’ Ben?” Joe Davis asked.
“You might call it a ‘mode,’ too. It’s called an EDM, an Emergency Descent Module. It only activates within the autopilot computer’s logic circuits when it senses a rapid depressurization coupled with an indication that the pilots aren’t functioning. In other words, no control inputs for a certain number of seconds. If that happens above twenty-seven thousand feet, the autopilot begins a steep, controlled descent and automatically levels itself off at whatever altitude is safe for that area as dictated by the GPS system. That gives the pilots and passengers time to regain consciousness if they’ve passed out. We didn’t realize the feature was in this autopilot, so when we were modifying the autopilot’s logic circuits, we didn’t take this out. Instead, we confused it.”
“How do you mean ‘confused it’?” Mac asked.
“Well, because when we disconnected its prime altitude reference, we not only left the emergency descent system activated, we inadvertently, electronically led it to think that sea level was where it ought to descend to if it ever had to take over. Now, what we call a ‘standard day’ at sea level is when the altimeter setting is two-nine-nine-two, or twenty-nine point ninety-two inches of mercury. On Monday, the actual outside atmospheric pressure was a bit higher at sea level than two-nine-nine-two, so when it leveled the airplane at what it thought was precisely sea level, that was actually fifty feet above the water, thank God.”
“And tonight?”
“Tonight, General, the atmospheric pressure out there was no longer lower, it was higher than two-nine-nine-two, and if we hadn’t reset the altimeter it was watching to fool it, our little automation circuit would have tried to fly us sixty feet under sea level.”
“So, Boomerang’s program was not the problem?”
Ben shook his head as he glanced at the two Gulfstream pilots, who were both nodding. “No, sir. On Monday night, Gene — Captain Hammond here — happened to hit the autopilot disconnect button instinctively just as I hit the reset button on my computer. We assumed at first that my computer had ordered the dive and the hair-raising level-off at fifty feet, because Gene didn’t recall hitting the autopilot disconnect. But after we got back a while ago and were waiting for you, we rechecked the flight data tape printouts from Monday, and there it is, big as life. It was the autopilot disconnect that restored control, not my computer reset.”
“Yes, but the dive began while we were still remotely controlling the aircraft,” Mac added.
“True, but remember that our Boomerang system required a major upgrade in the way the autopilot system holds onto the flight controls, making it all but impossible to disconnect it once you connect it. We did that so a hostile force, such as a hijacker in the cockpit, couldn’t override the remote inputs from the AWACS. But the EDM circuit used the same equipment, and we couldn’t knock it loose with the computers.”
“All you needed was the autopilot disconnect?” Mac asked.
“That’s right. As simple as that,” Ben remarked. “We just didn’t realize the autopilot was even involved.”
“Okay, but what initiated it? What made the autopilot think there was a rapid depressurization?”
“The speed brakes. Whenever the speed brakes were deployed, a mis-wired circuit sent a completely false message to the flight data recorder and the autopilot telling them a rapid depressurization had occurred. Each time we were in full test mode and Captain Hammond pulled the speed brake lever, he was inadvertently telling the autopilot that we’d had a rapid depressurization, and off it went.” Ben got to his feet before glancing over at Joe Davis. “So, bottom line? Boomerang is ready. I have no reason to conclude that there’s anything in that program code that needs changing. In fact, I think we’ve gone substantially beyond the minimums.”
Ben en held back as the rest of the assembled team headed for the doors, and Mac MacAdams noticed. A very nervous Joe Davis was pumping Mac’s hand in an obsequious display of appreciation, but the general finally sent him on his way. Once the room was empty of everyone else, Mac moved to where Ben was sitting and straddled a chair backward, his arms folded along the back as he studied the chief software engineer.
“Anything wrong, General?” Ben asked, squirming under the unspoken scrutiny.
“No.” Mac smiled. “But I have an important question for you.”
“Yes, sir. Go ahead.”
Mac glanced around to verify the room was empty of other ears. “Ben, you know we’ll have a lot of lives at stake, both in Air Force aircraft and on the ground, when this system gets installed and turned on.”
“Yes, sir. I’m well aware of that.”
“You’re also aware, are you not, that once Boomerang is deployed, any mistakes in the basic program will be much more difficult to fix without compromising safety.”
“Of course.”
“I know you’ve been working your tail off in the last few days to fix the program, even though we now know it didn’t need fixing. I want you to know that I’m very appreciative of your efforts and your dedication.”
“Thank you, General, I…”
Mac waved him down. “This isn’t an awards presentation, Ben.” He sighed, his eyes darting around the room once more, well aware he should wait until Dan Jerrod could be located and brought in with his anti-bugging equipment.
Never enough time, he thought.
“Ben, I know all about your visit to Dan Jerrod’s office. I know precisely what you told him and what he told you. You probably didn’t realize that he only pretends to work for Uniwave. In fact, he reports directly to me and no one else.”
“I… didn’t know that, sir.”
“And you still don’t. Understand?”
“Yes, sir.”
“And we will not speak of details discussed in that meeting. But here’s what I need to know, and bear with me because I’m shooting from the hip right now and thinking out loud. I know the system tested okay, and I accept that. But I know what you were worried about. Did any portion of that problem — that extra stuff that you found that worried you — show itself tonight?”
“No, sir.”
“But you’re still worried?”
“Of course, General. I can’t explain what it was… why it was there, you know? It’s eating at me. There’s no way that extraneous code should have been inside the program at any time. I have to view it as potentially hostile.”
Mac was nodding, his mind racing to choose the right words.
“Very well. Ben, there are many things that you have no need to know, and therefore I cannot discuss with you. I can assure you, though, that thanks to your speaking up and coming to Dan, we’ve solved the riddle and uncovered and neutralized the source. In other words, we’ve terminated the problem. The unfortunate part is, I simply can’t tell you the details.”
“It was… I mean, it’s all taken care of?”
“Yes, Ben.”
“There was a threat, but it’s completely defused? I was afraid that I’d merely interfered with them, and they’d try something else. Whoever ‘they’ is.”
“I understand. I wish to hell I could give you the details, but I can’t.”
“That’s okay. I understand, sir. I’m very relieved to hear this.”
“You’re a very diligent fellow, Ben. I knew you wouldn’t stop thinking this problem through and searching for a conclusion unless I told you personally it wasn’t necessary.”