THE
ANCIENT COMPUTERS IN THE BOEING 737 MAX ARE HOLDING UP A FIX
The perils of fixing a hardware problem with software
Abrand-new Boeing 737 Max gets built in just nine days. In that time, a team
of 12,000 people turns a loose assemblage of parts into a finished $120 million
airplane with some truly cutting-edge technology: winglets based on ones
designed by NASA, engines that feature the world's first one-piece carbon-fiber
fan blades, and computers with the same processing power as, uh, the Super Nintendo.
The Max has been grounded since March 2019, after some badly written software
caused two crashes that killed 346 people. And while Boeing has received plenty
of scrutiny for its bad code, it's the Max's computing power - or lack thereof
- that has kept it on the ground since then.
EVEN BY LATE-'90S CONSUMER TECH STANDARDS, THE FCC-730S WERE BEHIND THE CURVE
Every 737 Max has two flight control computers. These take some of the workload
off of pilots, whether that's through full automation (such as autopilot) or
through fine control adjustments during manual flight. These computers can
literally fly the airplane - they have authority over major control surfaces
and throttles - which means that any malfunction could turn catastrophic in a
hurry. So it's more important for manufacturers to choose hardware that's
proven to be safe, rather than run a fleet of airplanes on some cutting-edge
tech with bugs that have yet to be worked out.
Boeing took that ethos to heart for the Max, sticking with the Collins Aerospace
FCC-730 series, first built in 1996. Each computer features a pair of
single-core, 16-bit processors that run independently of each other, which
reduces computing power but also keeps a faulty processor from taking down the
entire system.
Even by late-'90s consumer tech standards, the FCC-730s were behind the curve.
By the time they went to market, Nintendo had already replaced its 16-bit SNES
console with the Nintendo 64 (the first game console to use - you guessed it -
a 64-bit CPU), and IBM had created the world's first dual-core processor.
Of course, old and slow isn't always worse: the 737 Next Generation series is
the safest narrow-body airplane ever made, in part due to these reliable, if
unspectacular, computers. To keep costs down, Boeing wanted to reuse them in
the next iteration of the 737 as well. The Max might still be flying today if
those computers simply had to perform the same tasks that they had for almost
30 years.
But Boeing needed them to do much more.
The important thing to know about the 737 Max is that it was a rush job. In
2010, Boeing's only rival, Airbus, unveiled the A320neo, a direct competitor to
the 737 Next Generation that could fly farther on less fuel and with lower
emissions than any other narrow-body airplane. Boeing was caught by surprise:
while Airbus had developed the neo in secret, Boeing's engineers had spent five
years debating whether to design a new 737 replacement or simply update the
airframe, without resolution. The neo changed that in a matter of months.
TO HIT THAT AMBITIOUS LAUNCH DATE, BOEING WOULD HAVE TO TAKE SHORTCUTS ON JUST
ABOUT EVERYTHING ELSE
But in order to offer its own new product when the new Airbus came out, Boeing
would have to rush the airplane out the door in just five years - less time
than it took to develop either the 777 or the 787. The main selling point of
the new 737 was clear: new engines that would increase the airplane's fuel
efficiency and range. But to hit that ambitious launch date, Boeing would have
to take shortcuts on just about everything else.
The new engines, which were larger and heavier than the ones on the Next
Generation, did indeed make the Max just as fuel-efficient as its rival. But
they also disrupted the flow of air around the wings and control surfaces of
the airplane in a very specific way. During high-angle climbs, this disruption
would cause the control columns in the airplane to suddenly go slack, which
might cause pilots to lose control of the aircraft during a dangerous maneuver.
Boeing could have fixed this aerodynamic anomaly with a hardware change:
"adaptive surfaces" on the engine housing, resculpted wings, or even
just adding a "stick pusher" to the controls that would push on the
control column mechanically at just the right time. But hardware changes added
time, cost, and regulatory scrutiny to the development process. Boeing's
management was clear: avoid changes, avoid regulators, stay on schedule -
period.
THE DEVELOPMENT TEAM ATTACKED THE HARDWARE PROBLEM WITH SOFTWARE
So the development team attacked the hardware problem with software. In
addition to the standard software suite on the 737 Max's two computers, Boeing
loaded another routine called the Maneuvering Characteristics Augmentation
System (MCAS). It would run in the background, waiting for the airplane to
enter a high-angle climb. Then it would act, rotating the airplane's horizontal
stabilizer to counteract the changing aerodynamic forces.
On paper, it seemed elegant enough. It had a side benefit, too: the Federal
Aviation Administration (FAA) doesn't scrutinize software as hard as it does
any physical change to the airframe. So MCAS was approved with minimal review,
outdated computers and all.
But Boeing's software shortcut had a serious problem. Under certain
circumstances, it activated erroneously, sending the airplane into an infinite
loop of nose-dives. Unless the pilots can, in under four seconds, correctly
diagnose the error, throw a specific emergency switch, and start recovery
maneuvers, they will lose control of the airplane and crash - which is exactly
what happened in the case of Lion Air Flight 610 and Ethiopian Airlines Flight
302.
The second crash grounded the 737 Max. Since then, Boeing has been working to
fix the software issue and get the airplane approved by regulators. But it's
been slow going.
BOEING TOOK A SHORTCUT BY CREATING A SOFTWARE FIX WITHOUT ENSURING THE HARDWARE
COULD HANDLE IT
In June 2019, Boeing submitted a software fix to the FAA for approval, but
subsequent stress-testing of the Max's computers revealed more flaws than just
bad code. They are vulnerable to single-bit errors that could disable entire
control systems or throw the airplane into an uncommanded dive. They fail to
boot up properly. They may even "freeze" in autopilot mode even when
the airplane is in a stall, which could hamper recovery efforts in the middle
of an in-flight emergency.
Despite all of this, Boeing insists that it can fix everything with software.
Boeing has elected not to go with a new, more powerful computer or to add more
of them to the two already there, in order to better distribute the workload.
For comparison, Airbus' A320neo has computers of similar vintage - but it has
seven of them.
Boeing is "dedicating all resources necessary to ensure that the
improvements to the 737 MAX are comprehensive and thoroughly tested," a
spokesperson told The Verge. "We do not anticipate changes to the
hardware."
So far, the FAA agrees: it completed its review of the software earlier this
year, and it seems to be on board with the proposed software fixes. But
returning the Max to service isn't as simple as getting the agency's approval
on the software. Because Boeing essentially bullied the FAA into certifying the
Max in the first place, the agency is eager to prove that it knows what it's
doing now. Its inspectors are scrutinizing the airplane with less pressure to
rush, and they have found several new issues with the airplane: faulty wiring,
debris in the fuel tanks, and wing components that don't meet FAA standards.
Even so, the FAA's reputation is already ruined. For decades, aviation
regulators have relied on reciprocal agreements to speed up the process of
certifying airplanes in other countries: if an airplane is approved by one
regulator, it's almost always approved by all of them. Now, however, Europe,
China, and India each want to certify the airplane independently, which will
add months to the timeline.
Once the Max gets the regulatory green light, it will still be several months
before it can carry passengers again. In January, Boeing announced that in
order to get certified to fly the Max, pilots will have to go through
full-motion simulator training (once, that is, the simulators are updated with
the final approved software package). This is a full retreat from one of the
airplane's original selling points: that pilots only needed a one-hour iPad
lesson to fly the new 737 model.
The problem is that there just aren't that many simulators to go around. There
are only 34 in the entire world, with only two companies approved to make more.
THE VERY SHORTCUTS THAT BOEING USED TO RUSH THE MAX INTO PRODUCTION ARE NOW
KEEPING IT ON THE GROUND
To put this in perspective, let's use Dallas-Fort Worth. It's home to two
airlines: Southwest and American. Between them, they have 13,000 737 pilots and
only one 737 Max simulator. Assuming four hours of simulator time per pilot and
running the simulators 24/7, it would take both airlines about six years to get
everyone approved to fly the Max. And there are 50 other airlines with Maxes in
their fleets and pilots to train.
So the very shortcuts that Boeing used to rush the Max into production are now
keeping it on the ground. It was once the fastest-selling airplane in history.
Now, nobody wants to touch Boeing airplanes: in January and February, the
company took only 18 new orders, an 80 percent decrease compared to 2019. Its
competitor, Airbus, recorded 296.
Despite the Max's declining popularity, Boeing remains optimistic about the
Max's future prospects.
"Our estimate for returning the 737 MAX fleet to service remains the
middle of 2020," said Boeing's spokesperson.
Nothing, it seems, will prompt the FAA to send this particular design back to
the drawing board. Instead, Boeing will once again attempt to compensate for a
hardware flaw on the 737 Max with slightly rewritten software. It's the same
design philosophy that created this catastrophe for Boeing in the first place -
and it's the same philosophy that has failed, so far, to produce a safe and
reliable airplane.
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