Boeing's Fatal Flaw (full documentary) | FRONTLINE PBS

What did Boeing know about the potential for disaster with its 737 Max airplane — and when did the company know it? FRONTLINE and The New York Times investigate the crashes that killed 346 people.


Thanks for sharing.
As a real life 737NG pilot looking at a possible introduction of the MAX in our company for a long time now, the docu reflects many of the discussions and findings I’ve seen being a topic in our company.

The fact that MCAS was designed to only take one data input is indeed a fatal flaw and something that’s mindblowing to have found its way into an end product at the time.
So many things in an aircraft have redundancy, even the less important stuff and then this system does not.

We’ve also re-trained the situation where an excessive nose-down trim requires a rapid and decisive input from the pilots, because the aerodynamic forces acting upon the stabilizer and the trim surface can become so high at certain (neg) AOA values and forward airspeed, that we need to act within a short timeframe or loose the ability to physically move the thing anymore, even with two people pulling at the wheel and/or yoke.

Actually, this was documented quite well in the earlier 737 models, but has since been vanished from the pilot’s manual.

This, however, is a seperate issue from MCAS, but doesn’t get separated often in the discussion about it and the two crashes.
Its great to see this docu does it well.


I should add that the excessive nose down trim situation is a deliberate setup without using adding thrust and letting speed build up in the descent.
A situation thats very unlikely to happen, because adding thrust will cause a nose up moment due to the amount of power the engine produce combined with their angle of mounting on the wing.
The NG doesn’t have an MCAS actively pushing down the nose, so there is an important difference to be made.
Still, for us as pilots, it was a very valuable training, even on the NG.


Can the question “what did XYZ know, and when did they know it?” get overused any more???

Hey…at least they didn’t call it Boeinggate… :man_shrugging:


Stupid “just add gate to anything if it’s a scandal” trope…

Like Watergate was about water. :roll_eyes:

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Another annoying trope is the Keep Calm one…


Keep Calm and Boeing On



I HATE that one.

Now, now…

pink band GIF

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Frontline has been around for over 30 years. They are the penultimate professionals.

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And most likely had the same narrator for all that time. You know that it’s going to be a bad ass investigation just by the tone of his voice.

From an outside view by a GA pilot, that rarely gets to fly an airplane with anything more sophisticated than a wing leveler, the sound of a runaway elevator servo seems pretty frightening. I guess that’s nothing new to commercial pilots, which I assume are taught to either hit the AP disconnect or pull breakers. Isn’t it somewhat fundamental that the human pilot should be able to override the machine? Or is that up for debate?

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That’s always possible in the case of the 737. In light of this specific situation (runaway stabilizer) we have the ‘stab trim cutout switches’ to disconnect the automatic system from driving the stabilizer and revert to manual clutch drive.

The docu also mentions this.
MCAS is also disconnected by these switches, but in case of the Ethiopian flight, the speed had already increased so much that physically moving the stabilizer (by means of the trimwheel) had become impossible due to the aerodynamic forces acting upon the stabilizer/trimtab combo.

In their reaction of desperately trying to get the nose under control they then switched the ‘stab trim cutout’ switches back to the normal position, thereby reactivating the (faulty data receiving) MCAS and driving the nose down actively again.
I don’t think these pilots could have done anything anymore to avert the crash once the airspeed became so high the stabilizer and trimtab went into ‘aerodynamic lock’, but this action probably caused Boeing to keep stating basically that the pilots were to blame and that foreign pilots are inferior to American pilots.
An convenient ‘truth’, but it didn’t save Boeings former CEO in the end. And rightly so.