Greed + Kludge = Dead
Scott Pedigo wrote: "From what I've read in various news articles, they needed to add bigger, heavier engines to get more power or better fuel efficiency, and this changed the center of gravity to the rear, making the aircraft less stable. To compensate, the MCAS was added.
"I suppose the proper thing to do would have been to change the engine mounts or move the wings farther forward, but doing that would have counted as a significant design change and necessitated a costly re-certification. Which is what they were trying to avoid."
Not quite. the problem was that Boeing saw rival Airbus's A320neo fuel economy as a serious threat. They wanted to offer similar economy in a similarly sized aircraft but didn't want to suffer the cost and time to market in developing a completely new aircraft. (Mistake#1: Greed).
To get the required economy from the by-now ancient 737 basic airframe design, engines with bigger fans were needed: as it turns out, much bigger fans. But the 737 is almost uniquely ill-suited to having larger diameter engines because of its already low ground clearance. (It's why previous 737s had those 'bulgy' looking engines, because they had to relocate the gearbox when re-engining the planes, in order to keep this clearance; it's only 17 inches.) To accommodate these much fatter engines, the only option was to move them forward and upward on the wing, changing the mounts. (Mistake #2: a nasty kludge.)
Having done this, they realised that this mucked up the plane's CG and, even worse, greatly increased the pitch-up-on-power experienced by all planes which have podded under-wing-mounted engines (the position of the engines creates an upward pitching moment when they power up.) The plane's handling characteristics were now different enough from its predecessor that fresh pilot training and certification would be required. This would cost the airlines a ton of money. Boeing decided to find a way to pretend that such training wouldn't be needed. (Mistake#3: Greed, again.)
(Even so, they needed to lengthen the undercarriage to keep the clearance at 17 inches.)
MCAS was created to counteract the pitch-up—which might have led to a very dangerous stall, if the angle of attack became excessive—by noting the AoA and, if too high, forcing the plane's nose down. In this way, the aircraft's new, potentially nasty habit, would be concealed. (Mistake#4: a nasty kludge, needed because of the previous nasty kludge.)
Anyone who's designed hard- or software will recognise this vicious cycle, whereby a seemingly sensible kludge later means you have to make another kludge, which then means you have to ... sigh, we've all been there. We've all reached the point where we've looked in the mirror, said "Shit, what am I doing?" and started again from the beginning. With a new design.
Boeing still made things infinitely worse. By making MCAS dependent upon the AoA, it created a very dangerous situation: a rogue AoA readout could force the plane's nose down very suddenly, even when close to the ground. It was easy and straightforward to minimise this risk by using two AoA sensors (or even three) and making sure that if they disagreed, the pilots would be told. It would be called an 'AoA Disagree Warning'. Instead of making this available by default, Boeing decided it would be a paid-for optional extra ... without explaining the new, potentially grave consequences of relying upon a single AoA sensor. (Mistake #5: Greed ... and yes, again.)
Al of this, and the invertebrate nature of the so-called regulator, FAA, meant that Boeing could pretend that pilots didn't need expensive sim time in order to fly the new 737 ... based on a half-century old airframe design. (Mistake #5, by the FAA: being spineless, captured, and beholden to the corporate interests it was supposed to regulate.)
Consequence: a single AoA sensor—a cheap part known for its fallibility—goes wrong. MCAS kicks in. Pilots who weren't even told that MCA existed are taken entirely by surprise. Their iPad-based "training" does mention how to disable it, but to do so required specific and unusual action, and in particular, recovery of the plane meant that pilots would need to reduce power and airspeed during climb-out (to reduce forces on the control surfaces, especially the elevators). This is a bit like expecting a show-jumper to loosen the girth before competing a course: it's completely counter-intuitive. No pilot—especially one who's suspicious of stall warnings produced by an AoA reading—wants to pull the throttles back, and thereby lose airspeed, when still near the ground. It is in pilot DNA to keep airspeed up, with lots of nice lift, when flying low. Else you can die very quickly.
Greed drove kludges, which then multiplied as they are wont to do; greed drove deception and spin, which led to fatal reliance on single points of failure; greed drove the misleading of airlines and, even worse, pilots who, when confronted by something they weren't warned about and didn't understand, could have saved themselves only by performing counter-intuitive actions that they were not drilled or trained in.
Yes, it's true that pilots properly drilled could almost certainly have saved both aircraft. (It's also true that Sully could have landed back at the airport instead of in the Hudson ... but only if he had perfect knowledge of what was happening and acted instantly.) The pilots of the two doomed planes would in fact save their planes and passengers' lives, given a second chance. But they didn't know then what we know now.
As Boeing's previous actions these emails reveal: they were driven by greed to cut corners and build kludges upon kludges, compounding their disgraceful behaviour with lies and deceit. If the flying public refuses ever to set foot in a 737 MAX, Boeing deserve everything they get.