Airbus is bidding to sell 260 planes to American Airlines, which currently has an all-Boeing fleet. The media has focused on the financial aspects of the potential deal, weighing what American Airlines has to gain or lose as a corporation. But what about the pilots? Is there a difference, for them, between flying Airbus and Boeing aircraft?
Absolutely. Airbus and Boeing have different control systems, and most pilots strongly prefer one over the other. (The Explainer isn’t aware of a poll, and so has no way of knowing which manufacturer pilots favor overall.) Modern Airbus planes employ a “fly-by-wire” system. The pilot controls the plane by manipulating a joystick next to the main console and a set of pedals. The movement of the joystick and pedals is translated into electrical signals, which switch on and off machines that move the plane’s flaps, slats, ailerons, and rudder. Most Boeing jets don’t have a joystick, but a more traditional yoke. (The 777 is Boeing’s first fly-by-wire plane.) When a pilot yanks back on the yoke, he’s actually pulling cables that move the plane’s control surfaces with the help of some hydraulic systems. In short, there’s less electronic mediation between the pilot and the machinery in a Boeing aircraft. Some pilots think this gives them a better “feel” in flying the plane, while others prefer the video-gamelike quality of the electronic interface.
Airbus also places more restrictions on how far the pilot is able to push the aircraft. All planes, no matter the manufacturer, must fly within certain limits, known as the “flight envelope,” or risk mechanical failure. For example, if a pilot attempts too steep a climb, the wings may stall. * Airbus aircrafts won’t allow that to happen because they are programmed to ignore the pilot’s instructions if the plane’s computers think they would lead to catastrophe. The system is called “flight envelope protection,” and the pilot has a limited ability to override it by changing its default limits.
The pilot of a Boeing jet has somewhat more freedom to push the envelope. (The phrase “pushing the envelope” was popularized in The Right Stuff, Tom Wolfe’s 1979 book about the daring pilots of the space program.) * For the most part, the flaps and rudder will obey the pilot’s commands, even if those commands might lead to mechanical failure. It’s not easy to get to that point, though. A pilot would have to pull back with significant force to bring the plane into a potentially stall-inducing climb.
It’s not clear whether flight envelope protection makes air travel safer. Advocates argue that it could have prevented the November 2001 crash of an American Airlines jet in Queens, New York. FAA investigators determined (PDF) that the first mate had pushed down the rudder pedals too aggressively in response to turbulence, causing the rudder and its attachments to separate. A captain who had worked with the pilot in the past recounted an earlier incident in which he inappropriately pushed the rudders as far as they would go. (The American Airlines jet in question here was actually an Airbus, not a Boeing, which predated the automatic system. American Airlines retired its last Airbus jet two years ago.)
The problem with flight envelope protection is that pilots occasionally have to take unorthodox actions in desperate situations. Opponents of the system point to the near-crash of China Airlines flight 006 in 1985, in which the pilot managed to recover after an uncontrolled descent of nearly 30,000 feet. It’s possible, though, that a flight protection system would have prevented the descent altogether.
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Explainer thanks Robert W. Mann of R.W. Mann & Company Inc.
Corrections, July 12, 2011:The article originally stated that a too-steep climb could cause the engines to stall. In fact, it is the wings that stall. (Return to the corrected sentence.) It also originally stated that the phrase “pushing the envelope” dates to WWII. The phrase “pushing the flight envelope” dates to WWII, but “pushing the envelope” is more recent. (Return to the corrected sentence.)