When Airbus introduced the newest member of its best-selling A320 line, the A320neo, it was aimed squarely at unseating Boeing’s 737 series dominance. Both planes are the workhorse for many airlines around the world, flying the short to medium distance routes.

These routes are also the ones where the competition is the harshest, and where any savings can mean the difference between bankruptcy and survival for an airline. Airbus’ A320neo promised to reduce fuel consumption by up to 15% thanks to re-engineered aerodynamics, and using newer, more efficient engines. Considering that around 40% of a flight’s cost go toward fuel (compared to e.g. around 15% for the crew), any airline would welcome these savings with open arms, making this new model a very attractive option for airlines looking to update their fleets.

And Boeing didn’t have an answer to Airbus’ challenge. The 787 Dreamliner was still in development after billions of investment and years of delays. Now Airbus threatened to kill future sales of Boeing’s cash cow airplane. So they scrambled to come up with a refresh, in order to keep their existing customers with them.

But doing so presented Boeing’s engineers with a problem. The 737 is already a very low-slung airplane, and newer, more efficient engines are significantly bigger than previous ones, so they could not just be mounted below the wing. Engineers had to move the engines forward and up, to maintain ground clearance.

This, in turn, meant that the plane’s center of gravity had shifted, making it more unstable. In terms of stability, there are two points that are important: The center of gravity, and the center of lift. Think of it like balancing a pencil on your finger: You have to put your finger right under the pencil’s center of gravity, otherwise it will fall off. The center of lift is essentially the point where the wings (and engines!) “pull up” the airplane. The further apart those two points are, the more unstable a plane is, making it harder to fly¹. The new engine position also meant Boeing had to raise the nose higher, adding further instability.

Boeing’s solution was the MCAS, or Maneuvering Characteristics Augmentation System. Modern planes are basically flown by computers, with pilots directing the computers, but no longer providing direct input to the plane’s control surfaces (this is called fly-by-wire). The MCAS was an addition to these fly-by-wire systems, designed to address these problems by automatically pushing the plane’s nose down when it detected that a dangerous stall was about to happen, relying on angle-of-attack sensors² to detect this situation.

When Lion Air Flight 610 crashed into the Indonesian sea in October of last year, suspicions quickly centered on the MCAS as the culprit. But almost as quickly, Lion Air’s maintenance practices came into question, pointing to a problem with the angle-of-attack sensors. They appeared to disagree by as much as 20º even during takeoff, effectively making the MCAS unable to tell how the airplane was actually positioned into the airstream.

But unlike Lion Air, Ethiopian Airlines is known for its fairly modern fleet, and fairly good reputation, making a maintenance problem with the plane less likely. And both crashes look suspiciously similar, putting the MCAS into the spotlight again — especially why Boeing initially didn’t even include the system’s existence into the airplane’s manual.

The reason is that Boeing came up with another cost-saving measure for airlines: It promised that pilots would not need additional training in order to be able to fly this new generation of 737. Any time a pilot spends in training, means he’s not making the airline money. Getting new, fuel-efficient planes, that pilots with previous 737 experience could basically fly from day one meant an even sweeter deal for airlines, and making it a new best-seller for Boeing once they announced it.

Except Boeing can’t just claim that pilots wouldn’t need additional training to fly the 737 MAX. It’s regulatory agencies like the US’ FAA³ or Europe’s EASA⁴ that would eventually decide what kind of training was required from pilots when they certified the 737 MAX. And Boeing worked hard to ensure that every regulator would allow the plane to fly without extensive additional training for pilots⁵. But what was supposed to be a boon for airlines turned out to be a problem instead: Multiple pilots complained to the FAA that they didn’t feel safe flying the new 737 MAX, pointing to weird problems during flights.

Only after the Lion Air crash did Boeing even tell pilots that the system existed, and what it did, including one very notable difference to other similar, pre-existing system on the 737. These systems could also change the airplane’s attitude automatically, but would also automatically shut off and allow manual control if the pilot pulled on the control column. The new MCAS system does not do this, instead requiring manual disabling of the stabilizer trim system (of which MCAS is a part of) to deactivate.

Here’s the thing: If a problem like this occurs during flight, pilots are trained to work the relevant checklists to ensure the plane can fly safely. These checklists did include disabling the stabilizer trim system, but working the checklist takes some time. If the plane is flying at cruising altitude, the crew has enough time to do so, likely allowing them to regain control of the airplane.

But if the plane has just taken off, and has not yet gained enough altitude, then there probably won’t be enough time to run the checklist. And the first thing pilots would probably try was to pull back on the control column, which on previous 737 generations would have also deactivated any automatic trim control. But on the 737 MAX, doing so would not deactivate the MCAS, which would keep pressing the airplane’s nose down. Pilots were only informed about this behavior by Boeing after the Lion Air crash. It was not part of the 737 MAX’s manual.

It is a stark reminder that modern airplanes are enormously complex machines, and that pilots have to deal with increasingly complex inputs as well as deal with increased automation happening at the same time. Fly-by-wire and other mechanisms have made flying safer and more economical, but in exceptional situations, the same systems can become your worst enemy. And it’s an irony that the solution to these problems might even be more automation, not less.

But it’s also a reminder that regulatory agencies have to ensure that new planes require the training they need, regardless of what the manufacturer would like. And it’s also a sign of the times that the FAA’s previously sterling record on safety matters is slowly eroding. Further complicating matters is that the FAA has been without a commissioner for over a year, after Trump tried to nominate his private jet pilot for the job, and was promptly rejected by the Senate.

Naming is still hard

Remember the USB naming conventions from last time? Turns out, the USB standard has come up with yet another naming scheme for the next generation: USB4. That’s right, no space, unlike every other previous generation of USB. I guess no consistency at all is also some sort of consistency.

Space Access

Last week, SpaceX successfully returned their unmanned Crew Dragon capsule to earth, paving the way for a crewed test flight in July. This means trouble is brewing for Roscosmos, the Russian space agency. They were able to charge NASA an arm and a leg to fly astronauts to the ISS, but only because they were the only game in town. No one else was able to fly humans into space. But now SpaceX promises to do the same far cheaper, and without reliance on Russian technology, now that Roscosmos can no longer control access to the ISS.

In the meantime, an Israeli company has launched a probe towards the moon⁶, and they provide live tracking as well as simulations of the mission on their website.

Flat Space

If you were to go to space, it would immediately be apparent that the Earth is round. However, for some reason this fact has still not yet been universally accepted. Flat-Earthers are claiming that the Earth is, in fact, completely flat. But whenever they come up with experiments to prove that they’re right, they have to work very, very hard to ignore all the evidence that the Earth is, in fact, round.

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