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Considering that MCAS is an added ‘feature’ to avoid stall, you would think they could just remove it and be done. After all, it wasn’t part of the original 737.

Sadly, from my limited understanding, due to the engine location change on the airframe, the plane naturally pitches up... making it necessary.

One thing seems clear to the external observer, this is a 737 in name only.




due to the engine location change on the airframe, the plane naturally pitches up... making [MCAS] necessary.

Most jet airliners have a pitch up tendency. The problem with the MAX is two related issues...

First, FAA has a requirement that stick pressure must follow certain patterns - namely, the harder you pull/push the stick, the more the plane reacts. Due to engine placement, the MAX did not meet this requirement.

Second, Boeing needed to create the MAX with minimal (approaching zero) re-training of pilots.

MCAS was supposed to meet both needs - by having MCAS adjust the stabilizer, the stick behavior/feel came back within requirements. And because it was all automatic, the pilots didn't need retraining in the simulator. Correcting the stick feel without a system like MCAS would have required more substantial changes to the plane, which would have likely required simulator time, which was likely a deal-breaker for some airlines.


Well, it IS a 737, that is part of the problem.

The 737 has a feature almost no other new plane have: you can order it with a internal staircase so people can leave the plane without a specialized airport terminal.

This feature requires the plane to keep its current overall shape, otherwise the staircase thingy would not work.

So to keep this feature, while putting a bigger engine on the plane, they had to move the engine forward, and change its shape too, otherwise the engine wouldn't fit between the wing and the ground.

Then THAT caused the necessity of MCAS.

So long story short: wanting to keep backward compatiblity with the 737 staircase, led to the engine hack, that then to maintain backward compatiblity with the handling led to the MCAS hack...

So, it IS a 737, in the sense they kept the staircase and to do that ended needing the MCAS...

The other option would have been abandon the staircase entirely and make a taller plane, this would allow a bigger engine with no handling changes, but although this would remain a 737 from handling perspective, it would not be a 737 from the airports perspective: it would need to remodel the airports to install bridges or purchase of ladder trucks.


The other option would have been abandon the staircase entirely and make a taller plane, this would allow a bigger engine with no handling changes, but although this would remain a 737 from handling perspective, it would not be a 737 from the airports perspective: it would need to remodel the airports to install bridges or purchase of ladder trucks.

No that would not be the major problem. Specifically since practically any airport nowadays has the infrastructure to service such a plane. This was quite different 50 years ago.

The reason why they couldn't have heightened it was that a new type certification would have been required and Boeing wanted to avoid exactly that at all cost.

Even at the cost of 346 dead people.


Just skipping the staircase it not enough. To make the plane taller it needs a new landing gear. But that doesn't fit into the existing gear wells. So now you need to redesign the gear wells. But the gear nearly touch in the middle already. So you neet to make them taller, and attach them to the wing further out. Which the Wing can' take. So you need to redesign the wing. At this point you better just admit that the 737 design from 1964 is at the end of its life.


TIL: The airstairs are still an option of most (all?) 737 variants. RyanAir appears to have them on part of the fleet. And many BBJ have them, as not all general aviation terminals have jetways.

I assumed the stairs were not longer installed, and the height of the 737 was just an anachronism.

Video for those that haven't seen them: https://www.youtube.com/watch?v=unZeusTrDX4


The 737 MAX 10 has taller (extending) landing gear. Not sure if the airstairs will still be an option.

https://www.boeing.com/features/2018/08/737max10-landing-gea...


That landing gear only extends when the nose gear is off the ground. It's really just to prevent a tail strike. An alternate choice would be a little extra wheel up on the tail, as was done with the Concorde.


It was more than a staircase issue- they were trying to avoid time-consuming and costly pilot-retraining.


The Homer car comes to mind whenever these kinds of convoluted and unchecked engineering adventures have the light shone on them.


It is my understanding it is only necessary to make the Max 'compatible' with the 737 so nobody needed to be retrained and recertified.


My understanding is that, without MCAS or some other design change to fix its unacceptble handling characteristics near the stall, the 737 MAX would have been uncertifiable even as a new type. It is the way that Boeing went about implementing that fix, in an attempt to avoid an additional training requirement, that has caused all the trouble.


Let's be clear here, though: it's the airlines who refuse to buy an aircraft with additional training requirements. Pilots can only fly one aircraft type, and retraining to a different type is an expensive proposition. If Boeing could make an aircraft that fit under the 737 type, they really had no choice but to do it.

They also probably could have succeeded, too, if not for other systemic problems within the company.


It is not clear to me that they probably could have succeeded in satisfying all these conflicting goals, if not for other systemic problems in the company. Even now, with (one hopes) everything in the open and the systemic problems pushed aside, they are having trouble getting it done.

You say Boeing had no choice, but one choice was to acknowledge the problems, aim to keep the type certification with additional training, and negotiate with its potential customers on that basis. There is no law of mankind or nature that says Boeing is entitled to a certain number of sales at a particular profit.


Yes, that was the gamble. But as others have pointed out, instead of actually ‘updating’ the plane Boeing changed it materially. Calling it a 737 was a stretch at best.


Yeah they're gonna have to fix the MCAS - duck-taping the engines on a bit further back isn't an option.




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