June Boeing 737 MAX Simulator Incident Led To Software Redesign

After a near-crash during simulation, Boeing has undertaken rigorous testing on its Boeing 737 MAX aircraft. It has now created an improved software redesign, which is thought to be the reason delaying a return to service.

A software redesign is the cause of the delayed 737 MAX return to service. Photo: pjs2005 via Wikimedia Commons

The incident that retold history

A publication by Bloomberg has explained how a near-crash during a Boeing 737 MAX flight simulation forced the company to redesign the aircraft’s software.

In June, Boeing had completed the majority of fixes on the 737 MAX software ahead of the return to service. At the time, Boeing was set to work delivering a less aggressive MCAS (Maneuvering Characteristics Augmentation System) which caused its other aircraft to crash.

However, during the simulation, the aircraft nose-dived in the same aggressive way characteristic of the Lion Air and Ethiopian Airlines crashes. Needless to say, the aircraft was not “operationally suitable” as Boeing had once believed. Nor was the fix a completed masterpiece.

The simulation issue meant Boeing had to rethink its design. Photo: Boeing

The simulation incident forced Boeing to return to the drawing board leaving the world waiting for what has been nearly a year after the initial grounding.

Creating more sophisticated safety precautions

Boeing’s design for its grounded MAX aircraft is now a lot more sophisticated. Rather than attempting to bring the MAX back into service as soon as possible, as seemed its previous approach, it’s gone one better. Most importantly, Boeing is bringing the aircraft in line with modern safety standards.

One of the caveats of the June simulation helped Boeing to progress in its design. As well as creating an MCAS which responded less aggressively, Boeing was also hoping to rely on swift reactions. It was hoping that pilots would be able to respond quickly to prevent crashes. However, that proved a weak solution since one of the pilots in the simulation failed to respond fast enough.

So now Boeing is creating a system with more modern flight computers. The new computers will be responsible for monitoring one another. The company said:

“We updated the Maneuvering Characteristics Augmentation System (MCAS) on the MAX by adding three additional layers of protection…The company is making steady progress on the second software update announced in June for additional flight control computer redundancy.”

Boeing said that it had redesigned the way its Angle of Attack (AoA) sensors interacts with the MCAS. The MCAS is programmed to evaluate information from both of these Angle of Attack sensors before it activates.

Boeing has redesigned the communication between AoA sensors and MCAS. Photo: Boeing

Boeing has created a system where computers interact with one another more frequently. It’s what some of its newer aircraft are already using. And it’s a more reliable system. It’s perhaps, the kind of change that Boeing should have originally designed. Boeing said:

“These software changes will prevent the flight control conditions that occurred in this accident from ever happening again.”

So, when will the MAX return to service?

But the aircraft isn’t in the clear just yet. Boeing expects to carry out even more rigorous testing to prove that the new system really is as safe as possible.

Many airlines are keen to return the MAX to service, but testing still needs to be completed. Photo: Southwest Airlines

The FAA (Federal Aviation Administration) has requested that Boeing send revised documentation on the new system. This, as well as scrupulous testing, will ensure confidence in the aircraft’s ability to safely operate. Boeing states on its MAX update website that it has already undertaken over 800 test and production flights as well as more than 1,500 hours of testing with the new software.

How long do you think it will take for the MAX to return to service? Let us know in the comments below!

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High Mile Club

I’d say February 2020 in the US. April of that year in Europe, and probably May for China.


You can be totally! sure about that “No one will want to fly with a Boeing 737 MAX after that”.


I get a tingle of apprehension when I see the phrase “as safe as possible”.


So do I.


Also “… prevent …… from ever happening again.” This phrase is used often now and is supposed to instill confidence. It sounds more like used-car salesman talk.


Interesting that they apparently chucked the original MCAS design in favor of the approach described above….which sounds rather “Airbus-like” with its multiple layers. At the same time, it’s telling that it took a simulator event to point out to them how crappy the original concept was…they should have been able to see that from the outset.
It’s just a pity that they wouldn’t chuck the whole plane and start developing a new NSA instead. The MAX will always be a flying compromise.


It will be a huge operation to update all the MAX aircraft already produced. I wonder if the MAX will fly again in March 2020.


I don’t know when it will fly again, and I don’t care that much because I will never put my two feet in that plane anyway.


Both the 737 Classic and Next Gen series lasted approximately 20 years each. Based on the current fiasco, the 737 MAX won’t last half as long when SW and Ryan Air start looking for “clean sheet” replacements a hell of a lot sooner than expected.

Both Boeing and Airbus know this, but neither wants to cast a shadow over their current cash cow programs (ie: MAX and NEO) by announcing brand new replacements. A classic Catch 22 situation.

This all sounds like something out of an Arthur Hailey disaster novel but there’s no hero to the rescue!!


I don’t think Airbus have the same urgency as Boeing: the A320 neo family is popular, economical and reliable (apart from the Pratt & Whitney engine problem)…and it’s flying rather than sitting on the ground. I would imagine that Airbus are carefully examining the design of the A220 family to see how the airframe could be enlarged as a future A320 replacement. They have time on their side.


Imagine how different Boeing’s situation could have been now if instead of Airbus, Boeing was the one who had bought the C series from Bombardier. It wouldn’t have solved all Boeing’s woes, but Boeing would have had at least one very bright ray to light up some dark clouds.


I’ll be much happier if the airframe is modified rather than relying on software. It’s called “inherently safe design” in the process industry. The horizontal stabiliser needs to be physically (mechanically) limited so that the pilots can still manually retrim the aircraft if there is a runaway of the stabiliser trim, even outside the design envelope.


Rog. At last!! I’ve been posting about this exact big problem for months. The set limits on the VIT horizontal stabilizer. Even some pilots don’t seem to understand that the elevators cannot possibly return an aircraft back to the straight and level, if the stabilizer has slowly cranked it’s way up the worm drive..We also realize that these limits must have been set for maximum nose or tail heavy. But now the fun begins………Or can and will in the event of problem.


ROG We’re on the same page. I’ve posted for months about this obvious error, I say again, maybe in a different way. Doubling up on the AOA vanes is of course good, but the REAL PROBLEM still exists and that is the computers when sensing a rapid nose up pitch instruct the VIT (movable tail horizontal stabilizer) to trim. But this is wrong because this slow moving beauty is not the elevator. A fix, starting at the computers, re-route MCAS output feed away from this connection.. Oh! and limit the MCAS enhanced pitch angles on the stabilizer, if a breakage… Read more »


Hold on a sec:

‘So now Boeing is creating a system with more modern flight computers. The new computers will be responsible for monitoring one another.’

So they’ve changed hardware, as well as software?


Frank, it seems the whole wreck is a flying disaster…they’ll change anything necessary to get the piece of junk flying again a.s.a.p. so that they can stop the financial hemorrhaging.
Have you ever been to Egypt? You see old French-made taxis and trucks there, from the 70s, held together by pieces of rope, metal plate, cable ties and leather strips…anything that will keep them (barely) together and on the road. In essence, that’s the MAX!


From what I understand, this Boeing always had 2 computers, but they hardly ever communicated with each other. The computers alternated in being used as the primary computer with each new flight. Now both will be used all the time and they’ll frequently be ‘comparing notes’ as it were.


I am curious if the old Boeing 737 NG is suffering from pickle fork crack forming prematurely in some planes, 27,000 cycles vs. the designed 90,000 designed cycles, I hope the design for the 737 Max pickle forks has been redesigned for the new powerful engines and the added stress just saying.

John Page

“Most importantly, Boeing is bringing the aircraft in line with modern safety standards.”
You mean it wasn’t ????? This model was introduces only a year ago!


Yeah, that’s exactly what I said to myself when I read this article 😉


And just look how the process of “bringing the aircraft in line with modern safety standards” has evolved: – First it was going to be just a re-writing of a bit of MCAS software, to make it less aggressive. – Then we were told that the processing power on the flight computer was inadequate to deal with certain situations. – Next we heard about the trim wheel, and the fact that some pilots may not have enough force to turn it during a nosedive. I still haven’t heard a solution to that issue, by the way. – Subsequently, we heard… Read more »

SY gunson

GIVEN THE PETTY TRADE WAR waged against Huawei & China, plus FAA’S refusal to certify the COMAC 919 , Boeing will never sell into that market again.. As for flying on that beast, I’m an experienced pilot but I’m not nuts. Sure there is a technique to unload elevators to cope with elevator blow-back but a whole new generation of pilots have never been taught these coping techniques in their training syllabus. NO THANKS: if it’s a Boeing, I ain’t going! informal surveys on TWITTER say 100% of respondents refuse to ever fly on the Max. Southwest &American Airlines are… Read more »