Be careful with this one. Small planes are one thing. Commercial jetliners are another realm completely. And do you mean somebody who knows nothing at all about flying? How about a private pilot who has flown four-seaters, or a desktop simulator buff who has studied a jetliner’s systems and controls?
The outcome in all cases is liable to be a catastrophe, but some would fare better than others. It depends too on the meaning of “land.” Do you mean from just a few hundred feet over the ground, in ideal weather, with the plane stabilized and pointed toward the runway, with someone talking you through it? Or do you mean the whole, full-blown arrival, from cruising altitude to touchdown?
I saw the MYTHBUSTERS thing 2007, the Discovery Channel show “Mythbusters” set things up in a NASA simulator stripped down to represent a “generic commercial airliner.” The hosts took the controls, while a seasoned pilot, stationed in an imaginary control tower, carefully instructed them via radio. On the first try, they crashed. The second time, they made it.
But all they really did was land a make-believe airplane from a starting point already close to the runway. The scenario most people envision is the one where, droning along at cruise altitude, the crew suddenly falls ill, and only a brave passenger can save the day. He’ll strap himself in, and with the smooth coaching of an unseen voice over the radio, try to bring her down. For somebody without any knowledge or training, the chance of success in this scenario is zero.
This person would have to be talked from 35,000 feet all the way to the point where an automatic approach could commence, complete with any number of turns, descents, decelerations, and configuration changes (appropriately setting the flaps, slats, and landing gear). I reckon that would be about as easy as dictating organ-transplant surgery over the telephone to somebody who has never held a scalpel. It’d be tough even for a private pilot or the most obsessive desktop sim hobbyist. Our would-be hero would have a hard enough time finding the microphone switch and correctly configuring the radio panel, let alone the maneuvering, programming, navigating, and configuring it would take to land safely.
A few of you might remember the film Airport ’75. A 747 is struck near the flight deck in midair by a small propeller plane, and all three pilots are taken out. I almost hate to say it, but dangling Charlton Heston from a helicopter and dropping him through the hole in the fuselage wasn’t as far-fetched a solution as it might sound. It was about the only way that jumbo jet was getting back to earth in fewer than a billion pieces. The scene where Karen Black, playing a flight attendant, coaxes the crippled jumbo over a mountain range was, if less than technically accurate, useful in demonstrating the difficulty any civilian would have of pulling off even the simplest maneuver.
As noted in Cecil’s list, a few years ago, here in New England, after the lone pilot of a Cape Air commuter plane became ill, a passenger took over and performed a safe landing. The TV news had a field day with that one, though the passenger was a licensed private pilot and the aircraft was only a ten-seat Cessna. Otherwise, there has never been a case where a passenger needed to be drafted for cockpit duty. I guess that means either it never will happen, or it is destined to happen soon, depending how cynical you are about statistics.