|
|
[p]T[span aria-labelledby="word-first--0" role="text"][span aria-hidden="true" role="presentation"]he[/span][/span] first sign of trouble appeared just after takeoff. Inside the cockpit of PK-LQP, a brand-new Boeing 737 Max belonging to Lion Air, the stick shaker on the captain’s side began to vibrate. Stick shakers are designed to warn pilots of an impending stall, which can cause a dangerous loss of control.[p]
[br][p] They’re unmistakably loud for that reason.
But the airplane was flying normally, nowhere near a stall. The captain ignored it.
About 30 seconds later, he noticed an alert on his flight display — IAS DISAGREE — which meant that the flight computer had detected a sensor malfunction. This required a bit more attention. [p] A modern-day passenger airplane is less like a racecar and more like a temperamental printer: you spend more time monitoring and checking systems than you do actually driving the thing. So the captain passed control of the aircraft to the first officer and began the troubleshooting process from memory.[p id="qV2pgC"]Like all commercial aircraft, the Boeing 737 Max has multiple levels of redundancy for its important systems. In the cockpit, there are three flight computers and digital instrument panels operating in parallel: two primary systems and one backup. Each system is fed by an independent set of sensors. In this case, the captain checked both instrument panels against the backup, and he found that the instruments on his side — the left side — were getting bad data. So with the turn of a dial, the captain switched the primary displays to only use data from the working sensors on the right side of the airplane. Easy.[p id="qV2pgC" style="text-align: center;"]
[br][p id="J0e6O9"]All of this took under a minute, and everything appeared to be back to normal.[p id="igx1ux"]At 1,500 feet of altitude, the takeoff portion of the flight was officially complete, and the first officer began the initial climb. He adjusted the throttle, set the aircraft on its optimal climb slope, and retracted the flaps.[p id="AJM615"]Except the airplane didn’t climb. It lurched downward, its nose pointed toward the ground.[p id="1kydnL"]The first officer reacted instinctively. He flicked a switch on his control column to counteract the dive. The airplane responded right away, pitching its nose back up. Five seconds later, it dove once again.[p id="I1I8nN"]The first officer brought the airplane’s nose up a third time. It pitched back down.[p id="GoY5aE"]There was no memorized checklist that seemed to apply to this situation, so the captain reached for the airplane’s Quick Reference Handbook (QRH). The QRH is a series of simple checklists that are designed to help pilots rapidly assess and manage “non-normal” situations. The idea is that Boeing has thought of every conceivable thing that might happen to one of its airplanes, and it has included all of them in the QRH. Basically, it’s more troubleshooting.[p id="lNG58G"]But nothing in the QRH seemed to apply, either.[p id="py5EoS"]Over the next six minutes, as the first officer struggled to control the airplane and the captain searched for the right checklist, PK-LQP climbed and dove over a dozen times. At one point, the airplane pulled out of a 900-foot dive at an airspeed of almost 375 mph, which is uncomfortably close to the 737’s “redline” of 390 mph.[p id="py5EoS"]
[br][p id="02TNeo"]The flight crew had to figure something out fast before they lost control of the airplane.[p id="V5JvYa"]Then the third person in the cockpit, who was technically off-duty, “dead-heading” to his next assignment, reportedly spoke up.[p id="MUCtRM"][em]What about the runaway stabilizer checklist?[/em][p id="MUCtRM"]
[em][br][/em][p id="vzaPhs"]It was a shot in the dark, another checklist. “Runaway trim” occurs when some kind of failure causes an airplane’s horizontal stabilizer to move — or “trim” — when it shouldn’t be moving at all. Usually, this creates a constant up or downforce that the flight crew has to try to counteract for the remainder of the flight. It’s kind of like trying to drive when your wheels are out of alignment.[p id="nrLN58"]PK-LQP’s problem was a little different. It was intermittent, temporarily reversible, and it wasn’t even clear if the horizontal stabilizer was causing the problem. But they were running out of options. They followed the checklist and flipped the STAB TRIM switches to CUT OUT on the center console.[p id="IMFwS3"]The airplane stopped pitching down. Five seconds passed. Then five minutes. Once again, PK-LQP was under their control and out of danger.[p id="rkdzDx"]An hour later, Lion Air flight 043 landed in Jakarta, Indonesia, only a few minutes delayed. Following standard procedure, the captain reported the episode to the airline, and the airline’s maintenance team checked for serious equipment failures, finding none.[p id="k3b6Na"]The following morning, PK-LQP, operating as Lion Air flight 610, took off at 6:20AM local time on its way to Pangkal Pinang, Indonesia. Its stick shaker activated just after takeoff. It threw multiple errors on the flight display. It dove just after the flight crew retracted the flaps. And it relentlessly activated its automatic pitch trim in the nose-down direction 28 times over the course of eight minutes.[p id="5UAkDS"]This time, there was no third pilot to help the flight crew.[p id="1us9FP"]PK-LQP may have reached 600 mph, faster than a Tomahawk missile, as it plunged into the water. It was the first 737 Max accident in its 18 months of service.[p id="1us9FP"][br][p id="1us9FP"]Source:- Theverge |
|
发表于 2019-05-07 19:45:07
收藏
Like
Stick Card
Jack
