In aviation, a "stall" happens when the wings of a plane stop generating enough lift to keep it flying...
It has nothing to do with the engines. A stall can happen even when they're running at full power.
It occurs when the "angle of attack" gets too steep. That's the angle between the wing and the oncoming air.
When that happens, air flowing over the top of the wing breaks apart and becomes turbulent instead of smooth. Lift drops off sharply.
At that point, the plane can no longer fly straight and level.
On October 29, 2018, a Boeing 737 MAX operated by Lion Air crashed – killing all 189 people on board.
Then on March 10, 2019, another 737 MAX operated by Ethiopian Airlines crashed. All 157 people on board died.
At the heart of both disasters was software called the Maneuvering Characteristics Augmentation System ("MCAS").
And this system in the 737 MAX was a shortcut...
In 2010, Boeing's main competitor, Airbus, introduced the A320neo. It was a more fuel-efficient version of the company's popular A320. And it competed directly with Boeing's 737.
Boeing had to move fast...
Rather than designing a brand-new aircraft, Boeing modified the latest 737s with bigger, more fuel-efficient engines.
But that created a problem...
The 737 MAX's fuselage sat closer to the ground than that of the A320neo. So the new engines had to be mounted higher and farther forward on the wings than on earlier 737 models.
That changed how the plane flew and made it more likely to pitch up and stall in certain situations. MCAS was Boeing's work-around.
But MCAS had a fatal flaw. The entire system depended on one small sensor.
That sensor monitored the plane's angle of attack. If it detected a dangerous nose-up angle, MCAS would automatically push the nose down.
On the Lion Air flight, the sensor malfunctioned. And MCAS pushed the nose down 26 times in 10 minutes. The pilots lost control.
Boeing likely left MCAS out of the pilot manual to avoid the cost of additional pilot training. The pilots had no idea the system existed.
On the Ethiopian Airlines flight, the crew knew about MCAS. When it triggered, they cut power to it entirely.
That meant flying the plane manually, which was too difficult at such high speed. In desperation, they turned the power back on. That meant MCAS triggered again.
It immediately pushed the plane into a fatal dive.
As a result of the two horrific crashes, Boeing had to ground its 737 MAX planes.
The grounding directly cost the company about $20 billion. That made it one of the most expensive corporate disasters in history – behind only automaker Volkswagen's $38 billion emissions scandal and the $68 billion Deepwater Horizon oil spill.
On one level, the 737 MAX disaster is a story about a single point of failure. Boeing put two angle-of-attack sensors on the plane. But it connected only one to MCAS.
If both had been connected, the system could have cross-checked the readings and caught the malfunction in time. That could have saved 346 lives... and prevented billions of dollars in losses for the company.
But the disaster is also a reminder of how much small things matter in technology...
The Power Gauge Likes This 'Unglamorous' Group of Stocks
A component you've never heard of – and doing a job you would never notice – can bring down an entire system.
That's the physical layer. It's the "unglamorous" side of technology.
Sensors, components, and connectors rarely make headlines.
They don't get the attention of a hot new app or a blockbuster drug. But they're the foundation that modern technology is built on.
Most of the companies producing the physical layer are in the Electronic Equipment, Instruments, and Components industry.
And right now, the Power Gauge loves this industry...
It's currently "strong" in our system. And 48 of its 118 rated stocks get a "bullish" or better grade today. That compares with just eight in "bearish" territory.
Looking ahead over the long term, tailwinds from the AI megatrend, electric-vehicle adoption, and industrial automation will be a big boost for this group of stocks.
It might not be glamorous – but keep an eye on this space.
Good investing,
Joe Austin
