The dual crashes of Ethiopian Airlines Flight 302 and Lion Air Flight 610 less than five months apart have raised a discomfiting prospect: that a seemingly random could send a nearly new, state-of-the-art aircraft into a nosedive. It's a prospect so frightening that most countries have banned the Boeing 737 Max 8 and Max 9 until the problem is sorted out.
What many people don't realize is that these two crashes are far from the only examples of automation malfunctions that have sent planes plummeting in the past few years. Here are some standout examples.
was en route from Singapore to Perth, Australia at 37,000 when unexpectedly the flight deck was filled with flashing lights and the sound of klaxons. The pilots were baffled—they could see out the window that the horizon remained level and the plane was flying normally. Then, boom! The plane’s nose jerked vigorously downward. The jolt flung passengers standing in the galley crashing into the ceiling, knocking them unconscious. Within two seconds, the plane dived 150 feet.
The pilot’s controls seemed to have no effect at first, but they gradually regained authority. The flight crew coaxed the plane back to its cruising altitude and headed for an emergency landing. Suddenly, the plane dived another 400 feet, again throwing passengers and crew around the cabin. Declaring an emergency, the flight crew coaxed to plane to an emergency landing at Exmouth, Australia, where 39 people were taken to hospital and 14 were medevaced to Perth with broken bones, lacerations, and spinal injuries.
Investigators later found that a malfunction had occurred in the plane’s Air Data Inertial Reference Unit, or ADIRU. This is a piece of electronics that determines where a plane is and how it’s moving. The error caused it to feed faulty information to the autopilot.
A Dassault Falcon 7X business jet was descending through 13,000 feet en route to Sultan Abdul Aziz Shah Airport near Kuala Lumpur, Malaysia, when it began to . Airspeed bled away, setting up the plane for a stall that would've sent it plummeting to earth. The French-speaking copilot at the controls realized he couldn't communicate the situation to his English-speaking captain quickly enough, so instead he went straight into a maneuver that he’d learned during his days as a military pilot: He threw the plane into a steep bank so that the nose veered sideways and slid back toward the horizon. After two minutes of erratic behavior, with the plane experiencing loads of up to 4.6g, the rudder inexplicably returned to neutral.
The plane landed safely. In the aftermath, Falcon 7Xs were grounded around the world until officials were able to trace the source of the problem: a bad solder joint that caused a control unit to transmit erroneous signals.
A was climbing toward 31,000 feet after departing from Bilbao, Spain when the co-pilot flying the plane noticed that the autopilot was acting strangely. When he turned it off, the nose dropped and the plane went into a dive. The co-pilot struggled with the controls but the plane would not respond. Within 45 seconds, the plane was descending at 4,000 feet per minute. With the help of the captain, he was able to pull back on the stick enough to get the plane to level off at 27,000 feet.
After conferring with technicians on the ground, the flight crew turned off one of the ADIRUs and the plane’s tendency to dive went away. The plane continued on its scheduled route and landed safely. Investigators later determined that two of the plane's angle-of-attack sensors had frozen in place, causing them to feed bad data.
, a Canadair CRJ-200 cargo jet, was en route to Tromso, Norway, when an alarm klaxon went off and the autopilot disengaged. The captain’s flight display showed that the nose was drifting too high, putting the plane at risk for a stall. The flight director, a display on the instrument panel that gives pilots control advice, told the pilots to put the nose down. Throughout training, the pilots had been taught that they must trust their instruments when they have no visual references, so the captain instinctively obeyed, pushing the plane forward so aggressively that it entered a negative-g dive that left the flight crew hanging in their straps. They could sense that something was terribly wrong, but amid the fear and disorientation they were unable to determine what.
“Turn right!” the first officer barked.
“Come on, help me!” The captain pleaded. “Help me! Help me!”
Though the plane was in a steep dive, a fault in the ADIRU had caused the flight computer to erroneously conclude that the plane was pitched too high, leading the flight director to issue a fatally incorrect recommendation. Quickly the plane passed its maximum operating speed.
“Yes, I’m trying!”
“Mayday, mayday, mayday!”
Just 80 seconds after the bug cropped up, the plane at 508 knots.