Gavin is correct, and of course, there's a little more to the story.  In this case, engines.

The 737 was originally designed as a short stubby two engine airliner that was low to the ground for various reasons.  In fact, you will have noticed that the 737 does not have main landing gear doors or panels.  The wheels are not covered once retracted.  The original engines for the 737 were skinny turbojets.  When the -300 series came out, it sported the CFM-56 engines which were turbofans.  Turbofans by design have much wider apertures up front (the fan) and in the case of the 737 they had to design a nacelle that was not round; it looks more like a squished pear.  They also had to relocate some of the engine accessories on the CFM-56 to accommodate the fact the engine was so low and close to the ground.

As time progressed, along with turbofan technology, the engines got wider and much more efficient, and this created a problem for the 737s.  The newer engines are absolute marvels of engineering.  They have become very powerful, extremely efficient, and utterly dependable to the point where ETOPS was expanded to allow twin engine airliners on overseas routes.  These marvels created the problem for the 737 because they were available for 737 competitors and could not be easily fitted to the 737 because it was so low to the ground.  Boeing came up with a solution to mount these engines on the 737 by mounting them forward and upwards on the wing.  This was done, exactly as Gavin said, so there would be complete certification continuity for the pilots.  They added a software feature (MCAS) to account for the repositioning of the engines under certain situations and this is where things got tricky.  The positioning of the new engines created a problem at high AoA (Angle of Atack) attitudes, so the MCAS would command the plane to push the nose down if the AoA indicator was telling it that the angle was too high.  The problem was that the MCAS only got information from one AoA indicator, the one on the port side.  If that indicator was not working properly, the MCAS would start doing things that would be bad and that's exactly what happened for the first crash, the LION Air one.  The AoA indicator was found to be bad during the prior flight and had been replaced with one that was not properly calibrated.  The MCAS was doing things to the plane that the pilots did not understand, and they did not turn off MCAS.  The plane crashed.

The second 737 MAX crash occurred 5 months later when an Ethiopian Airlines flight crashed 6 minutes after takeoff.  The problem was similar, with the MCAS commanding a strong nose down attitude due to a bad AoA indicator.  The crew did turn off the MCAS when they turned off the electric trim assit but since they had left takeoff power on, they were unable to manually trim the plane properly due to high pressure.  They turned back on the electrical assist just before crashing, but that also turned MCAS back on and it commanded the final dive.  The plane was going 700MPH when it crashed.

The 737 MAX was grounded for over a year after that second crash.

The 737 MAX returned to service at the end of 2020 and SWA flies a lot of them.   They still don’t have main landing gear doors.

Denys

-----Original Message-----
From: HP-3000 Systems Discussion <[log in to unmask]> On Behalf Of Gavin Scott
Sent: Wednesday, January 11, 2023 11:25 PM
To: [log in to unmask]
Subject: Re: [HP3000-L] First Southwest, Now FAA?

It's my understanding that Southwest has exactly one (1) type of equipment, the Boeing 737, for which a single type rating applies to every single model of that plane, including the 737 Max which was actually the reason all those people died because Boeing was under pressure to certify the Max under the same type rating as all previous 737 models so that they could sell them to Southwest without suddenly requiring them to maintain two different pools of aircrew which they probably would not do. Hence the automated augmentation system that was designed to force the Max to behave like other 737s but which ended up causing fatal problems.

G.

-----Original Message-----
From: HP-3000 Systems Discussion <[log in to unmask]> On Behalf Of Jack Rubin
Sent: Wednesday, January 11, 2023 7:24 PM
To: [log in to unmask]
Subject: Re: [HP3000-L] First Southwest, Now FAA?

Also, SWA has a greater variety of equipment, making it harder to match appropriately trained crews with equipment. Lots of unintended consequences once things start to unravel.
Jack

> On Jan 11, 2023, at 8:19 PM, Mark Landin <[log in to unmask]> wrote:
> 
> I read a lot more about the Southwest Airlines issue. SWA, unlike most 
> carriers, still runs their flights as a point-to-point network rather 
> than a hub and spike network. This makes it more efficient in many 
> ways but also makes it much more fragile and harder to start back up after a disruption.
> Given those constraints it’s unlikely any computer system would have 
> made much of a positive difference.
> 
> The informative discussion I read can be found here:
> https://arstechnica.com/civis/threads/how-difficult-is-it-to-program-a
> -restart-of-southwest-airlines-point-to-point-system-after-a-major-ser
> vice-disruption.1488902/
> 
> On Wed, Jan 11, 2023 at 19:11 Tracy Johnson < 
> [log in to unmask]> wrote:
> 
>> Two things that went down yesterday, I'm implying HP3000 guilt by 
>> coincidence.
>> 
>> On 1/11/23 20:09, Mark Ranft wrote:
>>> Does the Royal Mail use HP3000s?
>>> 
>>> Mark Ranft
>>> 
>>>> On Jan 11, 2023, at 12:42 PM, Tracy Johnson<
>> [log in to unmask]>  wrote:
>>>> 
>>>> May I be the first to raise there the same question about the FAA 
>>>> as
>> there was about Southwest during Christmas?
>>>> 
>>>> Does anybody know if the FAA (was: Southwest) is still using the HP
>> 3000 platform at all?  I read in the news (was: heard some employees) 
>> blaming their technology for some of their current problems.
>>>> 
>>>> Oh and we can add the Royal Mail.
>>>> 
>>>> --
>>>> Tracy Johnson
>>>> BT
>>>> 
>>>> 
>>>> 
>>>> 
>>>> 
>>>> 
>>>> 
>>>> NNNN
>>>> 
>>>> 
>>>> * To join/leave the list, search archives, change list settings, *
>>>> * etc., please visithttp://raven.utc.edu/archives/hp3000-l.html  *
>> 
>> --
>> Tracy Johnson
>> BT
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> NNNN
>> 
>> 
>> * To join/leave the list, search archives, change list settings, *
>> * etc., please visit http://raven.utc.edu/archives/hp3000-l.html *
>> 
> --
> "He's old enough to know what's right and young enough not to choose it.
> He's strong enough to win the world and weak enough to lose it." - 
> Neal Peart
> 
> * To join/leave the list, search archives, change list settings, *
> * etc., please visit http://raven.utc.edu/archives/hp3000-l.html *


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