Is it safe to fly the Boeing 737 MAX?

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Today (March 15, 2019): Travel new: Is it safe to fly the Boeing 737 MAX?

Last Sunday, an Ethiopian Airlines flight headed from Addis Ababa to Nairobi went down shortly after takeoff, killing all 157 people on board. It’s the second disaster with a brand-new Boeing 737 MAX following a crash last October, when a Lion Air flight went down 13 minutes after takeoff, killing all 189 on board. This has led to intense scrutiny over the Boeing 737 MAX, with travelers, airlines and aviation authorities around the world being worried about its safety. The Boeing 737 MAX is the newest version of the Boeing 737, which is the most popular commercial plane in the sky, with over 10,000 of them having been delivered. While the investigation in both crashes is still unfolding, I hereby try to answer some of the most evident questions regarding the B737 MAX and its involvement in two major crashes.


What is the Boeing 737 MAX?

In 2010, Airbus announced the launch a more fuel-efficient version of its best-selling A320 aircraft, called the A320Neo. In response, its competitor Boeing urgently considered an upgrade of its workhorse Boeing 737 aircraft and within months, the Seattle-based company introduced plans for the Boeing 737 Max, which engines that would yield similar fuel savings as the A320Neo. The Boeing 737 MAX performed its first flight in January 2016, gained Federal Aviation Administration (FAA) certification in March 2017, and made its first commercial flight in May 2017.

Compared to the older generation B737s, the MAX features different engines, aerodynamic improvements (including distinctive split-tip winglets), and airframe modifications. There are four variants of the Boeing 737 MAX, the most common of which are the B737 MAX-8 and B737 MAX-9 (the 8 and 9 indicate the size of the plane). The B737 MAX plane sold quickly based on features that passengers crave — a quieter cabin, more legroom — and bottom-line benefits to airlines, like fuel efficiencies. In fact, the B737 MAX is the fastest-selling airplane in Boeing’s history with about 5,000 orders from more than 100 airlines worldwide.

In light of the recent tragic crashes, it’s important to have knowledge of two particular features of the Boeing 737 MAX:

  • To compensate for the larger fuel-efficient engines on the 737 Max, Boeing silently added a computerized system, called Maneuvering Characteristics Augmentation System (MCAS), which prevents the plane’s nose from getting too high and causing a stall. MCAS operates independently from pilot input and uses airspeed and other sensor data to detect a dangerous condition; it automatically activates and trims the aircraft nose down when the angle of attack is too high (suggesting an approaching stall), when the autopilot is off, when the flaps are up, or during a steep turn (cf graphic below).
  • Boeing persuaded its airline customers and the FAA that the new MAX model would fly safely and handle enough like the existing B737 models and that airlines’ B737 flight crew did not have to undergo costly pilot re-training. In addition, both Boeing and the FAA decided that pilots did not need to be informed about MCAS, that was specifically developed to counter the risk that the size and location of the engines could lead the B737 MAX to stall under certain conditions. As a result, the MCAS system is not mentioned in the flight crew operations manuals, which is the basis for an airline’s documentation and training of a particular aircraft.

Here’s how MCAS is supposed to work (graphic by Mark Newlin & The Seattle Times):

What happened to Lion Air flight JT601?

On 29 October 2018, a Boeing 737 MAX from Indonesian Airline Lion Air operating a domestic flight from Jakarta to Pangkal Pinang crashed into the Java Sea 12 minutes after takeoff, killing all 189 passengers and crew. While the investigation is still ongoing, preliminary data revealed serious flight control problems. It is believed that faulty data from an ‘angle of attack’ sensor may have activated MCAS in the flight’s takeoff phase, pushing the aircraft’s nose down; the pilots repeatedly counteracted it and pulled the nose back up again, only to be overridden by the system again, until they lost their battle with MCAS. The New York Times published an excellent graphic overview of the Lion Air Crash (you can access it here). It was also revealed that the pilots of the doomed aircraft’s previous flight also encountered serious flight control problems, but they were able to overcome the issues and pushed on to Jakarta.

As a result of the preliminary investigation into this crash, the FAA and Boeing issued warnings and training advisories to all operators of the 737 MAX series to avoid letting the MCAS system cause an abrupt dive similar to the Lion Air flight (cf Tweet below). However, these advisories were not fully implemented yet at the time of the Ethiopian Airlines B737 MAX crash.

What happened to Ethiopian Airlines flight ET302?

Ethiopian Airlines Flight 302 was a scheduled international passenger flight from Addis Ababa in Ethiopia to Nairobi In Kenya. On 10 March 2019, the Boeing 737 MAX 8 aircraft crashed six minutes after takeoff near the town of Bishoftu, killing all 157 passengers and crew aboard. The pilot of the plane was 29-year-old Yared Getachew, who had been flying with Ethiopian Airlines for ten years and had logged a total of 8,231 flight hours. He had been a Boeing 737 captain since November 2017. At the time of the accident, he was the youngest captain at the airline. The first officer, Ahmed Nur Mohammod Nur, was a recent graduate from the airline’s academy with 200 flight hours logged. The investigation of the Ethiopian Airlines crash is still in its early stages; so far, all that is known is that the flight crew transmitted a distress call shortly after takeoff, reporting flight control problems.

Two brand-new Boeing 737 Max 8 models crashed just months apart. So far, no evidence has yet linked the crashes and the investigation is still ongoing and will likely take months (if not years). Yet, there are similarities between the two crashes that worry aviation authorities across the globe:

  • Both planes crashed shortly after takeoff
  • Flight control problems were reported by the crew of both flights
  • The vertical variations in both flights are similar, with aircraft oscillations indicating a repetitive pattern of nose dives, leveling out, and gaining altitude again in the moments before the crashes.

That there might be a link is also suggested by a statement of the FAA, widely recognized as the world’s most respected aviation safety authority: “On March 13, 2019, the investigation of the Ethiopian Airlines crash developed new information from the wreckage concerning the aircraft’s configuration just after takeoff that, taken together with newly refined data from satellite-based tracking of the aircraft’s flight path, indicates some similarities between the ET302 and JT610 accidents that warrant further investigation of the possibility of a shared cause for the two incidents that needs to be better understood and addressed. Accordingly, the Acting Administrator is ordering all Boeing 737 MAX airplanes to be grounded pending further investigation.”

What are the global consequences of both disasters?

In response to (public) fears expressed about the plane after the Ethiopian Airlines crash, airlines across the globe started grounding their B737 MAX fleet and more and more countries prohibited the aircraft from flying in their airspace. Once it became clear that there are similarities between the Lion Air and Ethiopian Airlines disasters, the USA – as the last country in the world – also decided to ground their Boeing B737 MAX planes, following an order by the FAA. Currently, all Boeing 737 MAX are (temporarily) grounded across the globe.

Which airlines fly the B737 MAX

Due to its popular features (e.g. fuel efficiency, quieter cabin, more legroom), the B737 MAX aircraft is the fastest-selling airplane in Boeing history with about 5,000 orders from more than 100 customers worldwide. So far, 387 Boeing 737 MAX have been delivered to 59 airlines:

  • Aerolineas Argentinas
  • Aeromexico
  • Air Canada
  • Air China
  • Air Italy
  • American
  • Cayman
  • China Eastern
  • China Southern
  • Comair
  • Copa
  • Corendon
  • Eastar Jet
  • Enter Air
  • Ethiopian Airlines
  • Fiji Airways
  • FlyDubai
  • Fuzhou
  • Garuda Indonesia
  • Gol
  • Hainan
  • Icelandair
  • Jet Airways
  • Kunming
  • Lion Air
  • LOT Polish
  • Lucky Air
  • Mauritania Airlines
  • MIAT Mongolian
  • Norwegian
  • Okay Airways
  • Oman Air
  • Royal Air Maroc
  • Shandong
  • Shanghai Airlines
  • Shenzhen
  • SilkAir
  • Southwest
  • SpiceJet
  • Sunwing
  • S7
  • Thai Lion
  • TUI
  • Turkish
  • United
  • WestJet
  • Xiamen

What will happen in the future?

With the entire B737 MAX fleet grounded across the globe, airlines loosing money, and the traveling public being worried, Boeing needs to come up fast with answers to the two main questions that everyone is asking are:

  • Does the Boeing 737 MAX have a design flaw ?
  • Is there something fundamentally wrong with the Boeing 737 MAX pilot training?

The MCAS software is the focus of attention. Although many experts caution that any conclusions are far from certain and other possibilities cannot be ruled out (e.g. pilot error, another technical defect), it is feared that the newly installed software system MCAS may have contributed to both Boeing 737 MAX distasters, which would be a devastating blow to Boeing. It is excpected that Boeing will change some things about the MCAS system. Following public pressure, the FAA admitted last week that Boeing is in the process of developing flight control system changes that will “provide reduced reliance on procedures associated with required pilot memory items,” a reference to the checklist for stabilizing the plane. Memory items are things of such importance that pilots should be able to easily remember to do them in a given situation without requiring written guidance. There will abe changes to how MCAS activated, how it responds to sensor input, and a “maximum command limit” on the number of times it can engage, said the FAA, adding that it expects to issue an airworthiness directive mandating the software enhancement no later than April.

In the past, Boeing has always declined to comment on reports that it’s working on a software update involving its MCAS system incorporated in the Boeing 737 Max 8 and 9 models. Last Monday though, after the FAA notification, it detailed its work on the software update.

For the past several months and in the aftermath of Lion Air Flight 610, Boeing has been developing a flight control software enhancement for the 737 MAX, designed to make an already safe aircraft even safer. This includes updates to the Maneuvering Characteristics Augmentation System (MCAS) flight control law, pilot displays, operation manuals and crew training. The enhanced flight control law incorporates angle of attack (AOA) inputs, limits stabilizer trim commands in response to an erroneous angle of attack reading, and provides a limit to the stabilizer command in order to retain elevator authority.

Meanwhile, Boeing’s 737 Max planes could remain grounded for weeks, or even months. The FAA has said the planes definitely won’t be allowed to fly again until the software fix is installed and verified to address concerns. The 737 Max is vital to Boeing, accounting for 47% of its commercial aircraft delivery in 2018, and over 90% of its unfilled orders, as of today.

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  1. I started following you because I really enjoyed the content you share on YouTube — that lead to following you on Instagram and then signing up for your newsletter and I’m so glad you did! Your whole brand (for lack of a better word) is so informative and this post was no different. It was like… a written-word Air Crash Investigation episode. Thank-you for posting it and sharing it. I don’t think I would’ve even been aware of the controversy (again, lack of a better word) around the 737 Max otherwise (to be honest, I wasn’t even aware that it was a specific craft that had crashed, let alone twice).

  2. The real question is to know if the B737 is aerodynamically safe ! Indeed the MCAS is not a simple envelope protection function to prevent a stall. Normally, an aircraft will stall at a certain angle of attack and warning systems as on previous B737 are sufficient (stick shakers, aural warnings, …). Those functions still exists on the 737 max indeed.

    The reality is that the B737Max as a vicious behavior in case of high AoA. It will naturally auto-increase its Aoa because the motors is to high on the wing thus will be above and before the wing in this case, greatly modifying the air movement above the wing. Thus a plane far from the stall angle will suddenly increase its Aoa and reach the stall value without warning time for the pilots. This is as if the stall,value was several ° less on the B737 than on previous versions and that the stall was brutal. This is a very bad behavior for a modern plane in fact. Thus the need for the MCAS to cover this very big difference with previous version of the B737.

    The best example is that after seeing that there was an issue with the MCAS, Boeing could have simply asked to descativate it by a patch on the angle activating it or on its effects on the rudder, gaining time to correct it peacefully. But they did not because without this function the plane can be dangerous at high Aoa. This function is in fact vital for the safety of the plane …

    Nota : I have seen some articles affirming thant without MCAS, the B737MAx is not airwothy as it does not respect US Federal Aviation Regulations (FAR) Part 25, in particular Part 25.173

  3. I think they should try to test those airplanes in a desert and see if they might crash again,because testing them with passengers is a really horrible thing a company could do.I personally booked Transavia Boeing 737 this December by accident,i might cancel it due to the stress it is giving me.And also,i have never flown with a Boeing 737 before,i only fly with airbus but my other company that i usually take is way too expensive this time.Hopefully Boeing will make it right to all the lives lost and future anxious passengers in the future.

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