I think all aircraft with autopilot need a big red button that gives back manual control. The autopilot was stuck in a stall correction loop. The automatic stall correction is for the situation of the pilots are not taking corrective action. However, there is never a case for a stall correction loop. Pilots need a fast way to disable an autopilot that is listening to malfunctioning sensors. We also need more redundancy in the sensors. Perhaps using a quorum algorithm.

As a Boeing 737 pilot for the past three years with more than 1000 flight hours in older versions, I can assure the readers that there certainly is a manual override for what is in the end—newfangled MCAS or not—uncommanded pitch trim movement. Until the cockpit voice recorder is recovered, we can't know the whole picture (and may never know anyways), but everything known so far from what has been made public points to the failure to apply basic piloting skills, including cutting power to the motorized pitch trim drive with that pair of conveniently located toggle switches and utilizing the conveniently located manual trim wheel (one for each pilot on a common shaft) stabilizing the airplane manually—in sunlit, visual weather conditions. The Boeing manual states that the motorized trim system can be overpowered by operating the manual trim wheel; simply grasping the wheel will stop it from moving under motor power. One need not know, strictly speaking, that there is such a thing as MCAS to recognize that one is fighting the trim and to take control of it. Indeed, there is a memorized procedure for misbehaving pitch trim published in the Abnormal Procedures section of the airplane's Quick Reference Handbook. The 737 is a well established, proven, operator-friendly design. Sure, the MCAS was likely receiving bad data due to faulty sensing. The bottom line, though, appears to have amounted to uncommanded trim, for which there is a Piloting-101 remedy. Please, find the CVR.

I live in a part of the world that can sometimes be frightening. But that for better or worse if often part of the scenery. Not a surprise. What I read in this short piece is absolutely terrifying. My air travel will never be the same.

“… confident in the safety of the aircraft model ...” Yes, the aircraft model has flown many flights without incident. But, as was shown in the Lion Air crash, its safety is vulnerable to the failure of a single sensor. Virtually all safety-critical aviation systems are designed to be resilient enough to withstand ‘single-point failures’. In my view, the apparent fact that this modified design gave up so easily, reduced this model’s safety. The modified design could have been accompanied by specific corresponding pilot training to offset the added risk that MCAS introduced. Fortunately, the widespread publicity of this failure mode and the pilot instructions makes it highly unlikely it’ll cause other crashes. With that awareness well established, we can say that safety has been restored.

As any commercial or military pilot will tell you, the cockpit is adorned with lights and switches with a discomforting story to tell. Aviation’s evolution with automation and computerization can be similar to your experience updating your laptop or smart phone. Poor upgrades often are the problem. For example, the warning lights for unheated pitot tubes were an early improvement after a sports team fatal jet crash. But new software problems are more hideous with little or no visible indication of the change. Even airline flight manuals, now automatically inserting new pages and warnings, are carried on computer tablets. Misunderstanding, if just unaware or never included in training, can be fatal, a factor as in the B-777 crash a few years ago in San Francisco or the Air France hull loss. Reduced training syllabi, accelerated pilot retirement rates, rapid upgrades, reduced numbers in pilot candidate pools, computerized ground training, and other factors are ongoing problems. But the pilots’ over-reliance on auto-flight is a problem that only magnifies the other factors. After completing a 45-year pilot career, I am hopeful that the pilots, not the engineers, are the prominent fixtures in the decision tree. The common axiom is never fly the first model of an aircraft. Without your smartphone, how many phone numbers do you remember any more? Me neither.

The pilots didn't need to know a thing about the MCAS system in order to know how to deal with this failure. This was clearly an electric trim issue, and the first step to deal with any trim issue is to disengage the electric trim. It's the same on a 737-300 as it is on a 737-MAXX. Non-pilots need to understand: this was about as basic an emergency situation as a professional pilot could ever face. In the U.S., airline pilots probably train these every 6 months. Any pilot of an aircraft with electric trim who doesn't know how to disengage it shouldn't be operating that aircraft. Period. And to think that two pilots on a transport category aircraft couldn't figure out between the two of them to turn off the electric trim after repeated malfunctions is just unimaginable. Not only that, but there are standard procedures for altimeter or airspeed disagreements. Neither of these things should have lead to a catastrophic outcome. This is two pilots who had no business being in that cockpit. End of story.

"It’s likely the pilots didn’t know about this automatic system, a new addition to Boeing’s 737 planes that many pilots were not made aware of. " It's unconscionable that Boeing could or would install any kind of new addition to a plane WITHOUT pilots being made aware. This action goes beyond a communication disconnect, it's blatant negligence. I cannot even begin to imagine the degree of fear the pilots, flight attendants and passengers endured during those horrid 12 minutes. I was in a cold swear merely after reading this painfully detailed article. Deepest condolences to the many families, loved ones and friends of the deceased.

Makes me want to rush out and buy a drive a self-driving car, for sure.

This explainer acts as if the pilots were without fault. In reality, accidents result from failure chains -- usually long ones. No doubt, Boeing's decision to implement MCAS and not train pilots on it was a major link in the chain. But these pilots also failed to execute the very simple steps in their quick reference handbook (QRH) -- which covers emergency procedures) for runaway trim. Had they done so after the first, or second, third, fourth, nth... time the computer ran the trim forward, this tragedy would have been averted. That the pilot(s) repeatedly tried to use the trim up button on the yoke rather than disabling the system and cranking the trim manually (as described in the QRH) is hard to understand. The CVR, if ever recovered, will be interesting to tell us whether the pilots even attempted the emergency procedures for this situation.

This is a fairly good explainer of the technical side of the accident, but I do have to question why the writers almost completely ignore the human side. I am no Boeing apologist–I agree that there's no excuse for system changes that are not communicated to the pilots, and Boeing should (and probably will be) punished in one way or another for it. But this is not simply a technical error; the pilots did not follow the correct procedure for a trim runaway, which is what the MCAS caused to occur. However, MCAS is not the only thing that can cause a trim runaway; a stuck motor, a jammed jackscrew, a computer failure, a trim switch failure, an autopilot failure, etc. The procedure for runaway trim, no matter the cause, is always the same: disconnect the trim motors. Like almost all modern air crashes, this is not so simple as a technical failure. It's a cascading sequence of events, starting with something small, compounded over time. As with almost all modern air crashes, it appears that a major component–far more important than this article makes clear–is a human failure. On any modern airplane–even on a 737 MAX–the computers are almost certainly making you more safe, not less. The pilots are much more likely to get in trouble.

A lot more could be learned about the reactions of these pilots if the cockpit voice recorder (CVR) were recovered. Perhaps they were aware of Boeing's recommendations, and there was some other factor that contributed to the crash. In fact, it is somewhat mystifying that the CVR hasn't been found yet, as the wreckage lies at less than 100 ft. from the surface. This depth is so shallow that it can be reached by sports (SCUBA) divers. According to Silviana (11 DEC 2018): "The Lion Air jet crashed in relatively shallow water of 30-35 meters but only the data recorder has been found as the remaining device lies among oil pipelines requiring an expensive self-positioning vessel without an anchor." Apparently, Indonesia’s transport safety committee (KNKT) is refusing to foot the bill for the recovery. If they drag their feet much longer the 90-day 'pinger' battery on the CVR will soon fail. Cite: Silviana, Cindy. Exclusive: Red tape, funding problems hamper Lion Air black box search. Reuters, 11 DEC 2018

This is a major failure on Boeing's part because they ignored the human factors engineering 101 principles of Visibility of System State and Keep the User in the Loop. With safety critical systems it is extremely important to provide very clear signals about system state, including whether sensors are operating appropriately. On top of this, steps to correct or overcome the problem must be immediately obvious. Of course, Boeing will point fingers because maximizing their profits are more important than our safety. Instead, they need to ground these planes until they are redesigned.

Great explainer, NYT. Thanks! The origins of the problem aren't with the angle of attack sensor or even the software that worked too well. The problem is Boeing's, who installed the MCAS but didn't bother informing the people who fly the plane how to turn it off.

An automated system should always have multiple ways of detecting errors in sensor readings, alerting the crew and reverting to manual control. Not explained by this article, Which altitude sources (barometric, radar, GPS, other) were inconsistent and why would that be? Also what is MCAS and how is it different from and similar to previous terrain collision avoidance systems.

In the end, the automatic "safety" system pushed the nose of the aircraft down and killed all aboard. Yes technically, there was an override, and technically the pilots should have been trained on it, and technically, the aircraft should not have been cleared for use. Technically, Boeing is correct. And I thought Boeing was the aircraft designer that left room for the humans to override the systems. After the disaster with Air France over the Atlantic, wherein the pilots also fought the computer all the way down; perhaps it is time for Airbus in that case and Boeing in this case, to remember that humans are the ones that ultimately need to be tasked with flying the plane. I would like to hope that the pilot and the co-pilot cursed the automatic safety system engineers and their offspring to hell. It is the least they could have done.

Thank you for this. I saw a more detailed article either in the Times or the Washington Post that provided similar information, but in more detail. This type of article can be effective in reaching more pilots and providing the information needed for them to recognize this situation, and inform them of the tools available to them to correct it.

This is what corruption does to OUR lives - kills us. WE THE PEOPLE must take a stand. Boeing employees should walk out of every factory in the world along with pilots, stewardesses and stewards and airline reservation employees. Tourist companies, contractors who serve the airline industry and airports should shut down. Massive civil lawsuits for dereliction of duty and depraved indifference should be lodged against Boeing and their main contractors to literally bankrupt them so they can no longer put OUR lives in danger with their insatiable greed. If OUR regulatory agencies can be so easily corrupted and refuse to do their jobs of keeping 99.9% of us safe WE THE PEOPLE will do it ourselves.

This is the FUTURE. Automatic systems - planes, cars, manufacturing - everywhere are subject to tampering. Looks at what hackers can do TODAY. So, let's turn our lives over to the Internet Of Things and become just another "thing."

This was criminal negligence by Boeing and the aircraft operating company. Boeing omitted crucial safety instructions in its updated manual. The incorrect readings on a previous flight were ignored. Almost 200 people died needlessly.

Thanks to this enhanced format, I doubt if I’ll ever get on another airplane again, knowing more now about them than I wish to.

This is a manufacturer's failure. The 737 series isn't new; the 737-MAX is a narrow-body fourth-generation iteration that Boeing envisioned as a long-haul sardine can meant to haul human-herds in an even- tighter space. Boeing didn't even have a manual to address the catastrophic potential of Lion Air's fate; no manual override for a pilot to take control over a COMPUTER. What. The. Heck was Boeing thinking in turning out this death-trap?