Just thinking about it is enough to make you queasy: A commercial airliner hits a pocket of turbulent air; its nose pitches up, then down, then heaves back up again. Meanwhile, the mighty ship yaws; it rolls to starboard; it rolls to port. In the midst of this event, which may last two to three minutes, even the most experienced fliers glance at the air sickness bags in the seat pockets in front of them … just in case.
If Boeing engineers have their way, however, that scenario may disappear, or at least be transformed into something much milder. That’s because the aerospace giant has endowed its 787 Dreamliner with a smoother ride technology that could help reduce the pitching, rolling and yawing that occurs when airliners are struck by powerful air gusts.
“We’ve focused on the kinds of frequency responses and frequency bands that cause motion sickness,” says Mike Sinnett, chief project engineer for Boeing 787 Systems. “We look at events that can last between one and five seconds and we’ve got plenty of frequency response in the airplane to work with.”
Indeed, the 540,000-lb mass of the 787 gives engineers a lot to work with. Such enormous masses don’t ordinarily respond instantly, even to the biggest wind gusts.
But the real innovation behind Boeing’s smoother ride technology lies, not in the aircraft’s mass, but in its electronics and software. To maintain stability, Boeing engineers use a combination of technologies like those in an automobile’s stability control system. Sensors around the aircraft measure changes in angular velocity and pressure distribution. Wind gusts that cause yaw, pitch or roll, for example, are detected and recorded by gyroscopic sensors. Similarly, vertical and horizontal forces on the craft are measured by accelerometers. At the same time, pressure sensors detect pressure distribution changes around the skin of the airplane through a selected (but unspecified) number of static air intake ports.
All of the sensor data is then sent to central processing units around the airplane. Boeing engineers won’t say how many or what kind of microcontrollers process that mountain of sensor data, but big commercial aircraft typically have more than a hundred electronic control modules, usually governed by a few master controllers. During flight, the controllers take in the data, apply proprietary software algorithms and determine what course of action to take. Using fly-by-wire techniques, the controllers then send signals to electric motors that actuate the rudder, elevators, spoilers, ailerons and flaperons. As a result, the aircraft autonomously actuates the control surfaces it needs to correct its own inertial reaction to the wind gusts.
“If the airplane is hit by a lateral gust, for example, we counteract it by suppressing the reaction to that lateral gust,” Sinnett says.
To be sure, other aircraft manufacturers have previously implemented such systems. But Boeing engineers say the 787’s smoother ride technology takes the state of the art to a new level.
“We don’t just sense the inertial response and then counteract it,” Sinnett says. “We sense a pressure differential and we counteract the pressure differential