November 6, 2019 • 45 mins
What happened with Boeing's 737 MAX aircraft and why did the CEO of the company appear before the US Congress? We learn about the flight control system that led to tragedy and the controversy surrounding it.
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Episode Transcript
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Speaker 1 (00:04):
Welcome to tech Stuff, a production of I Heart Radios
How Stuff Works. Hey there, and welcome to tech Stuff.
I'm your host, Jonathan Strickland. I'm an executive producer with
I Heart Radio and I love all things tech. But again,
this is another one of those episodes where I have
to couch that so not that long ago, I did
(00:25):
a series of episodes about the company Bowing and its history,
which once again is in the news as I record
this episode. So the week I'm recording this, which is
the very end of October, actually technically today is November one.
The CEO of Boeing just appeared before Congress to answer
questions about the tragedies involving two seven thirty seven Max
(00:47):
aircraft crashes. Politicians asked some very pointed questions to find
out when people at Boeing became aware of problems with
the aircraft and how much they knew, as well as
other details. So in this episode, I want to explore
exactly what went wrong and why. And while you could
summarize the story by saying a sensor and some software malfunctioned,
(01:10):
that's not really a full understanding of exactly what went
wrong and why it went wrong. So let's start with
the seven thirty seven Max in general, and the seven
thirty seven Max is history really only dates back to
July two thousand eleven. That's when Boeing learned that it's competitor,
air Bus, had made a deal with American Airlines to
(01:31):
sell two hundred A three twenty neo aircraft and the
eight three twenty family of aircraft first debuted in nineteen
eight six. They're intended to serve as short to medium
range aircraft. They are narrow body aircraft, which means they
have a cabin that measures no more than thirteen ft
(01:51):
or four meters wide, and they have a single aisle
going down the length of the cabin with seats on
either side. In other words, these aircraft sir the same
function as something like the seven thirty seven does. So
it might be a good idea to do a quick
rundown on the different sizes of aircraft and what they're
intended functions are, and to understand why we even have
(02:13):
these different sizes of aircraft. It helps to understand the
history of the development of airports and airlines in general.
I find that it could be easy to forget that
the systems we have in place today evolved over time
out of necessity. But I also know that's not the
focus of our episodes, So we're gonna be super general.
I'm not going to spend an enormous amount of time
(02:34):
on this, So the Right Brothers, really, I'm not going
to spend a whole lot time on this. But they
developed the first real airplane in the United States in
the early twentieth century by n In the United States,
the government had passed the Air Mail Act that gave
the Postmaster General the authority to work with private airlines
flying between certain routes the ability to carry mail. This
(02:57):
was sort of laying the groundwork for the modern airline.
The government followed that up with the Air Commerce Act,
which gave powers to the Secretary of Commerce to create
the rules and regulations that would apply to commercial aircraft.
That included requirements to license pilots, to certify specific aircraft
as being safe for commercial operation, to establish air routes,
(03:19):
and to create rules for air traffic. Now, many airlines
in this time were regional. They were operating between a
handful of cities within a general area of the United States,
but they gradually were able to grow to provide service
to more airports further afield. This might require a certain
number of hops between cities, and it created an incentive
(03:41):
for aircraft and engine manufacturers to find ways to increase
the flying range of aircraft to allow for more direct
service options between distant cities. The US government wasn't done yet, though.
In ninety eight, Congress past the Civil Aeronautics Act, which
in turn created these Civil Aeronautics Board or c a B.
(04:03):
One of the board's responsibilities was to regulate airfare prices
for passengers. Another was that it could assign specific routes
to airlines, giving permission for them to operate flights between
specific cities. The price regulation meant that airlines couldn't really
compete against each other with battling with lower fares for
(04:24):
routes between the same cities. A ticket on one airline
for a trip between let's say New York and Chicago
would cost pretty much the same as a ticket on
another airline because of this regulation. So that meant that
these airlines had to differentiate themselves in service because price
was going to be the same no matter where you
(04:44):
were going. Right if you went on one air airline
versus another you're gonna be paying the same amount, So
why would you choose one over the other? Had to
be because of the service. Further, if the Board determined
then airline was providing sub standard service along a specific route,
then the board would allow other airlines to operate along
(05:04):
that same route in order to create the competition needed
to improve service. So if the Board were to look
at say t W A and say, your service between
this city and that city has been reported as being substandard,
We're now going to allow these three other airlines to
compete in that space, the idea was that things would improve.
(05:26):
In nineteen fifty eight, the US government established what we
now call the Federal Aviation Agency or f a A,
which oversees airline safety operations. Twenty years later, in nineteen
seventy eight, the economic climate had changed in the United States.
Foreign airlines offering service to the US were not bound
(05:46):
by the price regulations of the Civil Aeronautics Board. American
airline companies could not compete with the lower airfares posted
by these foreign companies, and there was a growing resistance
to regulations in general in the US, so Congress passed
a deregulation Act than the Civil Aeronautics Board disbanded, The
(06:07):
price regulations came to an end, and airlines in the
United States could charge whatever they felt the market could
bear for any of their airfares. This also allowed new
airlines to join the market, which had previously been dominated
by just a few major carriers. The influx of competition
was a boon to passengers as far as airfare price
(06:28):
is concerned, but less so when it came to in
flight experience. More on that in just a moment. But
it also meant that some of the larger airline carriers
were struggling to compete. They had grown very large, and
they depended on a certain amount of revenue that happened
to have been guaranteed by the regulated prices. So when
those regulations went away and smaller, more nimble companies began
(06:51):
operating routes previously commanded by these giant companies, while the
giants began to wobble a little bit. This was exacerbated
by an economic recession in the nineteen nineties that saw
a reduction in air travel, and some of the big
airlines outright collapsed into bankruptcy, like t w A and
Pan American. So another recession in two thousand one, and
(07:13):
then the terrorist attacks on nine eleven further hurt the
airline industry, which would remain unprofitable for five more years.
Now since then, you know, since two thousand six, airlines
have managed to turn things around for the most part. Now,
the reason all of that was important is that it
creates the foundation for us to understand why there are
(07:37):
so many different types of aircraft out there, and why
conditions and aircraft have changed over time, and this in
turn informs us as to why Boeing made specific decisions.
So you may have seen images of air travel in
the nineteen fifties or nineteen sixties when it looked like
everyone was dressed in their Sunday best and they're enjoying
(07:58):
a big, comfy seat with plan D of leg room,
and they might even be chowing down on an impressive
looking meal. It's a pretty dramatic contrast to what you
find on a typical commercial jet today. So let's talk
about the different types of aircraft classes and what there
for and why things have changed. So you've got wide
body aircraft. These are the ones that are meant for
(08:20):
long range routes, usually such as transatlantic or trans Pacific routes.
They typically have two aisles running the length of the cabin,
and the width of the cabin tends to range from
sixteen to twenty feet or five to six meters. You
can have up to ten or maybe even eleven seats
arranged in a single row. In the economy class. They
(08:44):
really pack them in like sardines and some aircraft. That
means that with the size of some of these aircraft,
you can have configurations that can carry more than eight
hundred passengers, which is mind blowing to me. Most of
them are more like two fifty four passengers, but there
are some configurations that have significantly more than that. The
(09:05):
original wide body aircraft were something like luxury vehicles. They
were intended to provide a superior experience with more room
per passenger than you would find on other types of aircraft,
so they weren't all about packing as many people in
as possible. But then once the industry underwent deregulation, folks
that airlines began to figure out that there was another
(09:27):
tactic they could use. They could cram way more seats
on those aircraft, actually reducing the space for the average
traveler and maximizing the number of passengers that could fit
on a single flight. After all, the airlines were no
longer restricted to a regulated airfare price. They didn't have
(09:47):
to compete on the basis of service. They could compete
by offering lower airfares, and they can make up the
difference by putting more people on a single plane, so
they could actually make more money per trip even by
offering lower airfares per customer. By doing the old stand by,
you make it up in volume, and after balancing out
(10:07):
the pros and cons of delivering a superior experience to
the alternative of just going for the cold hard cash,
most airlines went the cold hard cash route, and thus
we started down the pathway of encountering aircraft with decreasing
amounts of leg room, narrower seats, and other features that
fuel stand up comedian routines. These huge aircraft are really expensive.
(10:34):
They also can't fit on all runways, and not every
airport can accommodate them. They were used for routes where
it made the most economic sense to use them, typically
on those transcontinental or trans oceanic flights. These tend to
be long range aircraft because they are more expensive to purchase, maintain,
and operate. Airlines typically have fewer of them in their fleets,
(10:58):
so they dedicate them to these long range routes. Enter
the narrow body aircraft. These became popular starting in the
nineteen sixties, but they really took off pun intended after deregulation.
They tend to be much less expensive to purchase, maintain,
and operate than their larger cousins. They can fit in
(11:19):
more airports and more runways, and they played into an
economic strategy that airlines used to compete against each other
because there was one other thing you could do to
use to your advantage besides the level of service or
the price of the airfare, and that was the frequency
of flights for specific routes. Now this really got going
(11:42):
with deregulation and the emergence of new airlines. Now passengers
could have a lot more options. When they were booking
a trip earlier, you might have a route that only
had two or maybe three flights per day between two cities,
so the passenger had to fit their schedule with the
airline schedule. But with more routes approved and more narrow
(12:04):
body aircraft in fleets, airlines had the chance to increase
the frequency between certain cities that had demand that warranted it,
and as you would imagine, most of the time, this
would involve cities that had regular traffic between them. You
weren't suddenly going to see an enormous increase in flights
to some city that was far out of the way
(12:25):
of everything else. Because there's no demand between two cities,
it makes no sense to operate hourly flights between them.
But for some routes that's exactly what did make sense.
So airlines began to compete by telling customers, hey, we
operate enough flights to your destination that you don't have
to worry about conforming to our schedule. We've got a
flight that fits your schedule. So this was the era
(12:49):
in which we saw the narrow body mid range aircraft
come into prominence, and that included the Boeing seven thirty seven.
The original seven thirty seven was introduced by Bowing in
nineteen sixty six. It was nicknamed a square airplane because
the length of the aircraft was the same as the
width of its wingspan. Both were approximately ninety three feet
(13:13):
or a little more than twenty eight meters. It's a
twin jet engine aircraft and the original seven thirty seven
had an engine mounted under each wing. This becomes an
important element when we get to the design of the
seven thirty seven Max. Now there are different versions of
the seven thirty seven that have different dimensions. The original
(13:34):
seven thirty seven one hundred innered service for the airline
luft Hanza, among others. United Airlines expressed interest in purchasing
some seven thirty seven's, but that airline wanted a slightly
longer version of the aircraft, so Boeing adjusted it and
then created a version of the seven thirty seven called
the seven thirty seven two hundred, and There are several others,
(13:58):
including the recent seven thirties even Max Okay so aircraft,
like the seven thirty seven from Boeing and the A
three twenty from air Bus, served similar purposes to act
as a short or mid range aircraft capable of carrying
around two passengers, which varies depending upon the aircraft's configuration.
By two thousand six, Boeing had been relying upon the
(14:20):
seven thirty seven design for forty years, when the company
began to consider the possibility of an entirely new design
to fill essentially the same function as the old, reliable
seven thirty seven. That decision was a huge one and
would require a lot of steps, So Bowing kicked the
idea down the road a few times, and then we
(14:40):
get to two thousand eleven and American Airlines ordering the
two hundred Airbus aircraft. It sent a signal to Boeing
that delays we're going to cost the company big time.
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seven thirty seven Max Alright. I left off saying that
Boeing concluded that developing an all new type of aircraft
wasn't going to pun intended fly. As Airbus began to
(16:51):
gain popularity among airlines and American airlines had as part
of its plan and order for a re engined seven
thirty seven aircraft. Boeing would need to focus on that effort,
and it abandoned the design of an entirely new aircraft.
It finally said, Okay, it doesn't make sense for us
to create a new aircraft from the ground up. Let's
(17:13):
go back to the seven thirty seven and make some adjustments.
This also brought with it a few other potential benefits.
Developing a new aircraft is time consuming and incredibly expensive.
Not only is the development process itself expensive, then there's
the certification phase, in which the aircraft must pass requirements
set by the various aviation authorities around the world in
(17:36):
order to be allowed to operate as a commercial aircraft.
And then there's the training phase. Pilots have to train
on the new aircraft to learn its systems and how
it flies. Not all aircraft behave the same up in
the air, and that means it's a really big deal
to invest in an all new type of aircraft. It's
asking for a lot of resources, both from the manufacturing
(17:57):
company and the various airlines out there. Updating and existing
design is far less daunting. The basic bones for the
aircraft are already there, and if the changes are within
certain parameters, you can get through regulations pretty easily. After all,
the base aircraft has already been through that process and
had been approved. Likewise, if the changes aren't dramatic, pilots
(18:20):
might be able to fly those planes without any real
additional training or having to go into any flight simulators,
because the aircraft, at least in theory, is going to
perform within the basic parameters of its predecessors. So there
are a lot of strong business cases for sticking with
a previously engineered design. Boeing's decision to stick with the
(18:40):
seven thirty seven was both more economical and, due to
the agreement it had reached with American Airlines, pretty much necessary.
One of the big goals Boeing had was to improve
fuel efficiency so that the seven thirty seven Max could
fly the same distance as older seven thirty seven's while
burning less fuel. That would also mean the seven thirty
(19:01):
seven Max could potentially have an increased range of flight
compared to earlier seven thirty seven's, and you could argue
that ultimately it was this push that would lead to
the tragedies of the two seven thirty seven Max crashes
that would ground the global fleet of seven thirty seven
Max aircraft. It's a sort of cascade effect where one decision,
(19:24):
that being to re engine the seven seven would lead
to other decisions that ultimately set the stage for catastrophe.
And by the way, this is all very easy for
me to say in hindsight, I'm not trying to suggest
that I would have spotted the potential for disaster before
it happened. It's only because it happened that we're able
to go back and analyze this and see where the
(19:45):
mistakes were made. But at the time it was not
necessarily that clear, at least not outside of Boeing. Boeing
chose for this new version of the seven thirty seven
some engines from a company called CFL. CFM is actually
a joint venture between g E Aviation and Saffron Aircraft Engines.
So in two thousand eight, CFM introduced a class of
(20:08):
engines they called the Leading Edge Aviation Propulsion Class or
LEAP l E a P. Boeing opted for the Leap
one B model of engines, which has a thrust range
between twenty three thousand and twenty eight thousand pounds of
thrust or between one hundred and one killing Newton's of
(20:29):
thrust and Newton is the amount of force required to
accelerate an object with a mass of one kilogram and
an acceleration of one second per second. CFM chose several
engineering advancements that contributed to better fuel efficiency and its
leap engines compared to older aircraft engines. That includes carbon
fiber composite components that are stronger than earlier materials at
(20:53):
a fraction of the weight, so while the engines are
big larger than previous seventh D seven engines, they don't
necessarily weigh as much as those older engines do. CFM
also used additive manufacturing, more commonly called three D printing
to produce those components. The leap engines also pre mix
(21:15):
fuel and air together before the mixture hits the nozzles
that enter the fuel into the combustion chamber, So older
engines would inject essentially amissed a fuel into the combustion
chamber and the mixing of the fuel and the air
happened inside the chamber itself. But according to CFM, that
meant lower fuel efficiency and greater emissions, So they say
(21:37):
that this new method cuts down on emissions and you
burn more of the fuel. The engines would give Boeing
the boost and efficiency needed to meet American airlines requirements.
In August two thousand eleven, Bowing officially announced the development
of this new version of the seven thirty seven, and
the company began to market the aircraft to various airlines.
(21:59):
By December two thousand eleven, Boeing found a customer in
the form of Southwest Airlines, which put in an order
for one fifty of the aircraft. Aircraft that were in
the earliest stages of development, mind you. From two thousand
eleven to two thousand fifteen, Boeing worked on the design
and production of the seven thirty seven Max. And here's
(22:20):
where we see some other decisions that would ultimately contribute
to the problems we saw when it entered service. The
new engines were larger than the previous seven thirty seven engines,
as I mentioned earlier, and traditionally those earlier seven thirty
seven engines would be mounted under the seven thirty seven's wings,
but these new engines were too big to do that
(22:40):
and still allow for adequate ground clearance between the bottom
of the engine and the ground itself, So that meant
the engineers had to figure out where to put these
engines on the body of a seven thirty seven, and
ultimately they decided to move the engines forward along the body,
ahead of the wings, and their position in such a
way so that the exhaust of the engines is directed
(23:02):
underneath the wings, which makes sense. You wouldn't want it
to go right up against the wings you melt your
own wings off. And also the way that their position
now means that the bottom of the engine has sufficient
ground clearance. But moving the engines forward had another consequence.
It changed how the aircraft moved in flight. Moving the
engines forward meant that in flight, the seven thirty seven
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Max has a slight tendency to tilt its pitch upward,
in other words, to tilt its nose up towards the
sky in a climb. That can be a problem for
lots of reasons, but a big one is on takeoff.
I mean, obviously you're climbing in takeoff, and in that phase,
pilot's guide a plane into a climb to reach cruising altitude.
(23:45):
So you don't want a plane to overcompensate and tilt
further back than the plan to climb for lots of reasons,
but a big one is that it can cause the
engines to stall out. So for a jet engine to work,
you have to have air flow going through that jet
engine in sufficient quantities, so it has to be moving
(24:05):
there in a sufficient speed. Essentially, I covered this in
recent episodes, so I'm just going to do a quick overview.
In a jet engine, incoming air hits fan blades that
compress that incoming air, which then either flows in or
around a combustion chamber where the engine ignites fuel. The
(24:26):
resulting hot gases in the combustion chamber expand and then
force their way out of the chamber through an exhaust
nozzle in the back of the chamber, and as they
escape they hit rotors on the rear side of the engine,
and the rotors connect through a shaft to the fan
blades that are in the front of the engine. So
(24:48):
as that exhaust is coming out the back of the engine,
it hits the rotors, and the rotors turn because of
that rapidly escaping gas, and because that's connected by a
shaft to the blades in the front, it turns. The
fan blades in the front of the engine, and the
whole thing perpetuates itself because of this continuous burn inside
the combustion chamber. But for this to work, you have
(25:11):
to have a sufficient amount of air flowing into the
engine in the first place. This is also why it's
necessary to jump start a jet engine on the ground.
They forced compressed air through the jet engine in order
to get it going, because you cannot get it started
any other way. Now, if the plane were to tilt
too far in an incline when it's climbing up into
(25:33):
the sky, the angle of the engine compared to the
airflow would be such that you wouldn't get enough air
to go through the engine for it to maintain operation,
and that's why it would stall out. You would have
a lack of air to keep that whole process going.
Installed engines would clearly be a disaster. Once Boeing engineers
(25:53):
recognize the tendency for the seven thirty seven Max designed
to go into this unprompted tilt, they had to how
to address that problem, and their solution was a combination
of hardware and software. On the hardware side, they relied
upon sensors that would automatically analyze the difference between the
airplane's attitude in the air and the angle of attack.
(26:17):
So the angle of attack describes the angle of a
plane's wing with respect to airflow. Angle of attack is
a big component of lift, that's the force that keeps
aircraft in the air. The other major hardware component is
the aircraft's horizontal tail, which can tilt to change the
plane's pitch. By altering the orientation of this horizontal tail,
(26:40):
it could act as kind of like a rudder, except
a rudder for the horizontal access, not the vertical, and
the effect is that it could force the nose of
the plane back downward in one of these climbs, so,
in other words, it could affect the pitch of the airplane.
The software overseeing the whole operation of this, which would
monitor the data coming in from the sensors and then
(27:01):
send appropriate commands to the tail, is called the Maneuvering
Characteristics Augmentation System or m CASTS. So if you've been
following the story of the seven thirty seven Max, you've
likely heard the term m CAST thrown around now. In theory,
m casts would operate in the background and make the
seven thirty seven Max perform as if it were any
(27:23):
other type of seven thirty seven aircraft, so it was
designed to override pilot controls. But this also meant that
if the system were to erroneously detect that the aircraft
were in too steep a climb, the tail flap or
the horizontal tail rather could force the plane into a
dive and the pilots would be struggling to pull out
of it, and they'd have to figure out how to
(27:45):
do that, and that would also mean knowing how to
disarm the system. Okay, so Boeing was pushing hard to
get the seven thirty seven Max ready to compete with
the Airbus A three twenty neo aircraft. The f a
A helped expedite things. In two thousand fifteen, according to
the Seattle Times, the f a A managers put pressure
(28:07):
on the agency's safety engineers, telling them to delegate the
assessment process to Boeing's own staff. This, by the way,
it doesn't seem like it's completely unusual, but it did
come as something of a surprise to me. I did
not know that's how things worked, because, in other words,
what that means is the agency and charge of overseeing
safety passed that job along to a company that produced
(28:31):
the very thing the FAA was meant to oversee. And
that might sound like it might not be the best idea.
I happen to think it was a pretty bad idea now, granted,
as we are now seeing, a failure on the part
of a company to be completely honest and rigorous with
its safety assessment process can result in terrible tragedies for
(28:51):
passengers as well as real hardships for the company itself.
So companies like Boeing have a very strong incentive to
police themselves care late. However, it sounds like that's maybe
not what happened with Boeing's self assessment. Again. According to
the Seattle Times, the safety analysis understated how far the
im cast software could force the horizontal tail to move
(29:15):
in an effort to stabilize the planes pitch. The Times
reported that in reality, the software was able to make
the tail move more than four times further than what
the report indicated, meaning a much more dramatic change in
pitch than what Boeing was claiming in the report. And
Boeing's response to this was that initially Imcast would be
(29:36):
able to move the horizontal tail at an angle of
point six degrees. It turned out it was more like
two point five degrees, and Boeing said, well, it was
only upon further study that we realized in order to
pull out of a disastrous climb, you would need a
greater movement than just point six degrees, which is why
(29:59):
we increased it. But at that point we had already
written the report. Seems to me like there might have
been an addendum that needed to be added there, but
what am I to say? So the report did not
address how mcasts would reset after a pilot's response and
would go into another dive despite repeated manual attempts to recover. So,
in other words, if a pilot were to respond to
(30:23):
this unplanned dive and pull back, you know, activate the
control and pull back on it, then it would stop
the system temporarily, but it would just reset and start
the cycle over again, and it might get more dramatic
each time. The the amount of of of tilt that
the horizontal tail would take, and thus the amount of
(30:45):
dive the plane would go into, would get greater each time.
The criticism is that the safety measure had no self
correcting process that would discontinue the diving efforts after manual intervention.
It would just keep going into a dive. So the
argument is that there should have been a system in
place where if a pilot intervenes, it deactivates this process
(31:10):
that was not in place. The Times criticized that the
assessment stated that if the system were to fail, it
would merit a hazardous danger rather than a catastrophic one.
These have real meanings in safety assessments. Hazardous means that
the outcome could result in injury or death to a
(31:31):
small number of passengers in a plane. Catastrophic is essentially
a designation stating that such a failure would result in
the complete loss of the plane and everyone on board.
So Boeing was saying that a failure of the system
would merit the hazardous level, not the catastrophic level. So,
(31:51):
in other words, the criticism is that the report was
downplaying the actual outcome of a system failure. One other
major problem is that Boeing neglected to include information about
m casts in its operation manuals for the seven thirty
seven Max. Pilots didn't know about it, airlines didn't know
about it. It wasn't until after the first tragedy that
(32:14):
this would be amended. When we come back, I'll talk
about that accident and the following events. But first, let's
take another quick break. Perhaps because the f a A
delegated the safety assessment duties to Boeing, Perhaps because the
(32:36):
seven thirty seven Max was a variant on a tried
and true aircraft design that had been an operation for
at that point fifty years. Perhaps because simulations failed to
create the sort of scenarios that we would unfortunately see
unfold in the actual operation of the aircraft. The seven
thirty seven Max past certification without much hullabaloo. Then, to
(33:00):
be fair, it seems in more investigations that some of
those simulations actually did show some problems, but Boeing didn't
really address that at the time. There was also no
need to train flight crews on how to operate the
seven thirty seven Max, because in theory it behaves so
much like other seven thirty seven's, particularly the seven thirty
(33:22):
seven in G, which was the immediate predecessor of the Max.
Pilots reported that they essentially had to complete a one
hour course on a tablet and not even spend any
time in a simulator before they would be certified to
fly a seven thirty seven Max. However, you want to
lay it out. The end of the matter is that
(33:43):
the seven thirty seven Max received its certification and Boeing
began to deliver the aircraft to customers. One of those
customers was Melindo Air, a carrier based out of Malaysia
and a subsidiary of a larger airline called Lion Air.
On October twenty ninth, two thousand eighteen, Lion Air flight
(34:03):
j T six ten, which was a seven thirty seven
Max eight, crashed just thirteen minutes after takeoff from Indonesia.
The plane crashed into the sea off Jakarta. All one
eighty nine people on board died as a result of
that crash. Among them were twenty Indonesian government officials. The
(34:24):
plane had been in use for about two months. A
pilot had reported a problem with the aircraft right away,
requesting a return to the airport before they lost control
of the aircraft. The CEO of Lion Air at the
time reported that a different pilot had reported the same
plane for a quote technical issue end quote earlier on
(34:46):
that week, but that the aircraft had been cleared to
fly the following day. An investigation following the crash indicated
that one of the angle of attack sensors had malfunctioned
on the Lion Air flight, and it had mistakenly indicated
a dangerous change in pitch and an oncoming engine stall,
(35:07):
and none of those conditions were actually existing at the time.
But the im CAST software and system went into action,
forcing the horizontal tail to move the the the nose
of the plane downward and put it into a dive.
The pilot was unable to counteract that, and the plane
crashed as a result. Making matters worse was the fact
(35:27):
that Boeing had not indicated the im cast was even
a thing. The pilots had no way of knowing what
it was that was causing the plane's nose to dive
or how they were supposed to stop it. On November six,
two thousand eighteen, Boeing issued a report revealing im CAST
to pilots and airlines for the first time. The report
(35:48):
also gave instructions to pilots on how to override in
cast in the event of a failure. Not At this point,
it wasn't yet certain that im casts was at fault,
but the signs were starting to point that way. In
the meantime, Boeing continued to receive orders for the seven
thirties seven Max from various airlines and was still in
full manufacturing mode. One thing Bowing did that later drew
(36:12):
an enormous amount of criticism was to place some responsibility
on the pilots themselves, stating that they should have known
to cut off the switches to the planes stabilizers. But
analysts who looked at the recovered flight data for the
Lion Air disaster said that what the pilots had experienced
didn't look like a stabilizer runaway scenario in which an
(36:34):
element like the seven thirty seven Max's horizontal tail would
make a continuous, uncommanded movement. The Lion Air flight data
showed that the tail movement was not a continuous motion,
and then the pilots were able to use the controls
to pull up several times before the plane became uncontrollable.
The analysts contradicted Boeing, saying that it wouldn't have seemed
(36:57):
obvious to cut off the stabilizer controls based on what
was happening then. On March tenth, two thousand, nineteen, and
Ethiopian Airlines flight from Addis Ababa to Nairobi crashed not
long after takeoff. Air traffic control lost contact with the
plane just six minutes after it left the runway. All
one fifty seven people aboard that plane died from the crash.
(37:20):
Early analysis suggested that once again, this was a failure
of m CAST. Further investigation showed that the crew attempted
to follow Boeing's instructions to correct for the failure, to
no effect. One day after the crash in Ethiopia, China,
and Indonesia, authorities issued orders that all seven thirty seven
Max aircraft operating in those countries were to be grounded. Now,
(37:44):
at that point, it was not yet known that m
CAST was definitely at fault for that second crash. The
day after that, on March twelve, two thousand nineteen, Canada,
the EU, and India also ordered all seven thirty seven
Max aircraft grounded. The f a A in the United
States would follow suit one day later, on March thirteenth,
(38:04):
two thousand nineteen. At that point, investigators were seeing signs
that IMCAST did play a part in the second crash.
The U s Department of Justice began a sweeping investigation
into the matter, and particularly into the process of the
jets certification. How could it pass certification if it had
this incredible flaw. That investigation has uncovered other concerning details
(38:28):
about the issue, including the revelation that a Boeing pilot
had brought concerns about the flight system of the seven
thirty seven Max to the attention of Boeing officials back
in two six. Previously, Boeing management had maintained that they
had no idea that the flight control system could cause
a catastrophe, but pilot Mark Fortner said that while flying
(38:49):
simulations that incorporated m CAST, he had encountered cases where
the flight management system was, in his words, quote running
rampant end quote. The revelation of this pilot's warnings came
a little more than a week before Boeing CEO Dennis
Muhlenberg and John Hamilton's Boeing's lead engineer, were to appear
(39:10):
before the United States Senate and the United States House
of Representatives and back to back hearings. During those hearings,
officials accused Boeing of purposefully downplaying safety issues and concealing
potential problems in an effort to achieve certification as quickly
as possible and thus start selling planes as quickly as possible.
(39:32):
Those officials are also concerned about the f a a's
practice to deputize the very companies it is supposed to
certify in the safety assessment process. Now that's not to
say that the US government is now advocating for sweeping
changes in certification or or even going to come down
hard on Boeing, because it's not as simple as that.
(39:53):
At issue isn't just the fate of Boeing, which is
an enormous employer in the United States. That also means
that there's a whole lot of folks who are potentially
voters who could be affected by any massive problems that
Boeing faces, and politicians are a little squeamish about doing
things that could potentially upset voters. There are airlines that
(40:16):
have aircraft they can't use. They're dealing with this problem
to they're looking at lost revenue. And there are all
these companies that supply bowing with components like GE, you know,
one of the companies responsible for the seven thirty seven
max engines. GE has had its own share of problems recently.
You can listen to my episodes about General Electric that
published not too long ago to learn more about those.
(40:39):
Because the seven thirty seven max is effectively on hold.
It could potentially cost companies like Ge and others billions
of dollars. Boeing, for its part, has made major changes
to m CAST. A big one was that moving forward
in CAST will take into account both angle of attacks
sensor before changing the horizontal tails orientation. It would no
(41:03):
longer accept just one stream of data as being enough
to change the plane's pitch. One of the other major
criticisms directed at Boeing from a design level is that
the MCAST sensor was a single point of failure with
no redundancy, and when coupled with Boeing's self assessment that
a failure just represented a hazardous outcome but not a
catastrophic one, create a false sense of security. Another big
(41:28):
change is limiting how much the tail will move like
I said. The original safety assessment said the tail would
only move point six degrees, but in practice it was
more like two point five degrees at maximum. Boeing has
also stated that it is going to limit the system
to activating for a single cycle, as opposed to the
reset repeat process that was seen in both Lion Air
(41:49):
and the Ethiopian Airline crashes. Then there's the long tail
stuff that Boeing is going to have to deal with,
stuff like trust and perception. While Bowing has made efforts
to address the problems in its seven thirty seven Max
flight systems, the company's credibility has taken a hit, as
has the perception of the f a A. There's still
(42:11):
lawsuits against Boeing that are making their way through the
legal system that are a direct result of the seven
thirty seven Max disasters, and Boeing still has hopes that
the aviation agencies around the world will lift the grounding
of the seven thirty seven Max aircraft before the end
of twenty nineteen or in early twenty twenty. Meanwhile, the
(42:32):
company has another headache to deal with. In October two
thousand nineteen, reports came out that aircraft operators had discovered
cracks on the seven thirty seven in G aircraft, or
at least some of them now. As I mentioned earlier,
the seven thirty seven in G is a predecessor to
the seven thirty seven Max. It's been in service for
several years. It doesn't have the m CAST software or
(42:55):
the engine placement of the Max, and it remained in
operation with any problems. But in early October two thousand, nineteen,
U S officials ordered an inspection of seven thirty seven
in G planes that had completed more than thirty thousand cycles,
that is, more than thirty thousand takeoffs and landings. And
the whole point was to look at the section of
(43:16):
the plane where the wing attaches to the body of
the plane. It's a part of the plane that is
called and I swear I'm not making this up the
pickle fork. Several airlines outside of the United States also
began to inspect their seven thirty seven in G s,
even those that had not yet completed thirty thousand cycles,
and reportedly some of those aircraft have had cracks appearing
(43:39):
in the pickle fork as well. Boeing stated that out
of the one thousand, seven thirty seven in G s
that had been inspected so far, inspectors that only indicated
that five percent of them have had cracks. Still, it's
another indicator that things are not going so great for
Boeing right now. We'll have to wait and see how
(44:00):
this all plays out, whether or not the seven thirty
seven Max will return to service, whether or not people
will trust it. You've had a lot of us politicians
already saying that they would not get on a seven
thirty seven max to take a trip based on what
they've seen. So there may be an inherent trust that
ends up being an enormous barrier to the seven thirty
(44:22):
seven max, even if the technology is proven to be safe.
So that's a huge issue. Once you've eroded trust, it's
very hard to rebuild. So we'll have to wait see
how that turns out. I am very curious to see
it myself. I've definitely been interested in this subject. I
fly fairly frequently, and knowing about this is something that
(44:44):
I think is important. Um, it's also something that fills
me with anxiety if I'm being perfectly honest, but I'd
rather know than not know. Anyway, that wraps up this
episode of tech Stuff. If you guys have suggestions for
future episodes, send me an email. The edge says tech
stuff at how stuff works dot com, or you can
tell me on Facebook or Twitter. The handle for both
(45:06):
of those is text stuff h s W or pop
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We also have a link to our online store where
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(45:32):
Stuff is a production of I Heart Radio's How Stuff Works.
For more podcasts from I heart Radio, visit the I
heart Radio app, Apple Podcasts, or wherever you listen to
your favorite shows.
Welcome to tech Stuff, a production of I Heart Radios
How Stuff Works. Hey there, and welcome to tech Stuff.
I'm your host, Jonathan Strickland. I'm an executive producer with
I Heart Radio and I love all things tech. But again,
this is another one of those episodes where I have
to couch that so not that long ago, I did
(00:25):
a series of episodes about the company Bowing and its history,
which once again is in the news as I record
this episode. So the week I'm recording this, which is
the very end of October, actually technically today is November one.
The CEO of Boeing just appeared before Congress to answer
questions about the tragedies involving two seven thirty seven Max
(00:47):
aircraft crashes. Politicians asked some very pointed questions to find
out when people at Boeing became aware of problems with
the aircraft and how much they knew, as well as
other details. So in this episode, I want to explore
exactly what went wrong and why. And while you could
summarize the story by saying a sensor and some software malfunctioned,
(01:10):
that's not really a full understanding of exactly what went
wrong and why it went wrong. So let's start with
the seven thirty seven Max in general, and the seven
thirty seven Max is history really only dates back to
July two thousand eleven. That's when Boeing learned that it's competitor,
air Bus, had made a deal with American Airlines to
(01:31):
sell two hundred A three twenty neo aircraft and the
eight three twenty family of aircraft first debuted in nineteen
eight six. They're intended to serve as short to medium
range aircraft. They are narrow body aircraft, which means they
have a cabin that measures no more than thirteen ft
(01:51):
or four meters wide, and they have a single aisle
going down the length of the cabin with seats on
either side. In other words, these aircraft sir the same
function as something like the seven thirty seven does. So
it might be a good idea to do a quick
rundown on the different sizes of aircraft and what they're
intended functions are, and to understand why we even have
(02:13):
these different sizes of aircraft. It helps to understand the
history of the development of airports and airlines in general.
I find that it could be easy to forget that
the systems we have in place today evolved over time
out of necessity. But I also know that's not the
focus of our episodes, So we're gonna be super general.
I'm not going to spend an enormous amount of time
(02:34):
on this, So the Right Brothers, really, I'm not going
to spend a whole lot time on this. But they
developed the first real airplane in the United States in
the early twentieth century by n In the United States,
the government had passed the Air Mail Act that gave
the Postmaster General the authority to work with private airlines
flying between certain routes the ability to carry mail. This
(02:57):
was sort of laying the groundwork for the modern airline.
The government followed that up with the Air Commerce Act,
which gave powers to the Secretary of Commerce to create
the rules and regulations that would apply to commercial aircraft.
That included requirements to license pilots, to certify specific aircraft
as being safe for commercial operation, to establish air routes,
(03:19):
and to create rules for air traffic. Now, many airlines
in this time were regional. They were operating between a
handful of cities within a general area of the United States,
but they gradually were able to grow to provide service
to more airports further afield. This might require a certain
number of hops between cities, and it created an incentive
(03:41):
for aircraft and engine manufacturers to find ways to increase
the flying range of aircraft to allow for more direct
service options between distant cities. The US government wasn't done yet, though.
In ninety eight, Congress past the Civil Aeronautics Act, which
in turn created these Civil Aeronautics Board or c a B.
(04:03):
One of the board's responsibilities was to regulate airfare prices
for passengers. Another was that it could assign specific routes
to airlines, giving permission for them to operate flights between
specific cities. The price regulation meant that airlines couldn't really
compete against each other with battling with lower fares for
(04:24):
routes between the same cities. A ticket on one airline
for a trip between let's say New York and Chicago
would cost pretty much the same as a ticket on
another airline because of this regulation. So that meant that
these airlines had to differentiate themselves in service because price
was going to be the same no matter where you
(04:44):
were going. Right if you went on one air airline
versus another you're gonna be paying the same amount, So
why would you choose one over the other? Had to
be because of the service. Further, if the Board determined
then airline was providing sub standard service along a specific route,
then the board would allow other airlines to operate along
(05:04):
that same route in order to create the competition needed
to improve service. So if the Board were to look
at say t W A and say, your service between
this city and that city has been reported as being substandard,
We're now going to allow these three other airlines to
compete in that space, the idea was that things would improve.
(05:26):
In nineteen fifty eight, the US government established what we
now call the Federal Aviation Agency or f a A,
which oversees airline safety operations. Twenty years later, in nineteen
seventy eight, the economic climate had changed in the United States.
Foreign airlines offering service to the US were not bound
(05:46):
by the price regulations of the Civil Aeronautics Board. American
airline companies could not compete with the lower airfares posted
by these foreign companies, and there was a growing resistance
to regulations in general in the US, so Congress passed
a deregulation Act than the Civil Aeronautics Board disbanded, The
(06:07):
price regulations came to an end, and airlines in the
United States could charge whatever they felt the market could
bear for any of their airfares. This also allowed new
airlines to join the market, which had previously been dominated
by just a few major carriers. The influx of competition
was a boon to passengers as far as airfare price
(06:28):
is concerned, but less so when it came to in
flight experience. More on that in just a moment. But
it also meant that some of the larger airline carriers
were struggling to compete. They had grown very large, and
they depended on a certain amount of revenue that happened
to have been guaranteed by the regulated prices. So when
those regulations went away and smaller, more nimble companies began
(06:51):
operating routes previously commanded by these giant companies, while the
giants began to wobble a little bit. This was exacerbated
by an economic recession in the nineteen nineties that saw
a reduction in air travel, and some of the big
airlines outright collapsed into bankruptcy, like t w A and
Pan American. So another recession in two thousand one, and
(07:13):
then the terrorist attacks on nine eleven further hurt the
airline industry, which would remain unprofitable for five more years.
Now since then, you know, since two thousand six, airlines
have managed to turn things around for the most part. Now,
the reason all of that was important is that it
creates the foundation for us to understand why there are
(07:37):
so many different types of aircraft out there, and why
conditions and aircraft have changed over time, and this in
turn informs us as to why Boeing made specific decisions.
So you may have seen images of air travel in
the nineteen fifties or nineteen sixties when it looked like
everyone was dressed in their Sunday best and they're enjoying
(07:58):
a big, comfy seat with plan D of leg room,
and they might even be chowing down on an impressive
looking meal. It's a pretty dramatic contrast to what you
find on a typical commercial jet today. So let's talk
about the different types of aircraft classes and what there
for and why things have changed. So you've got wide
body aircraft. These are the ones that are meant for
(08:20):
long range routes, usually such as transatlantic or trans Pacific routes.
They typically have two aisles running the length of the cabin,
and the width of the cabin tends to range from
sixteen to twenty feet or five to six meters. You
can have up to ten or maybe even eleven seats
arranged in a single row. In the economy class. They
(08:44):
really pack them in like sardines and some aircraft. That
means that with the size of some of these aircraft,
you can have configurations that can carry more than eight
hundred passengers, which is mind blowing to me. Most of
them are more like two fifty four passengers, but there
are some configurations that have significantly more than that. The
(09:05):
original wide body aircraft were something like luxury vehicles. They
were intended to provide a superior experience with more room
per passenger than you would find on other types of aircraft,
so they weren't all about packing as many people in
as possible. But then once the industry underwent deregulation, folks
that airlines began to figure out that there was another
(09:27):
tactic they could use. They could cram way more seats
on those aircraft, actually reducing the space for the average
traveler and maximizing the number of passengers that could fit
on a single flight. After all, the airlines were no
longer restricted to a regulated airfare price. They didn't have
(09:47):
to compete on the basis of service. They could compete
by offering lower airfares, and they can make up the
difference by putting more people on a single plane, so
they could actually make more money per trip even by
offering lower airfares per customer. By doing the old stand by,
you make it up in volume, and after balancing out
(10:07):
the pros and cons of delivering a superior experience to
the alternative of just going for the cold hard cash,
most airlines went the cold hard cash route, and thus
we started down the pathway of encountering aircraft with decreasing
amounts of leg room, narrower seats, and other features that
fuel stand up comedian routines. These huge aircraft are really expensive.
(10:34):
They also can't fit on all runways, and not every
airport can accommodate them. They were used for routes where
it made the most economic sense to use them, typically
on those transcontinental or trans oceanic flights. These tend to
be long range aircraft because they are more expensive to purchase, maintain,
and operate. Airlines typically have fewer of them in their fleets,
(10:58):
so they dedicate them to these long range routes. Enter
the narrow body aircraft. These became popular starting in the
nineteen sixties, but they really took off pun intended after deregulation.
They tend to be much less expensive to purchase, maintain,
and operate than their larger cousins. They can fit in
(11:19):
more airports and more runways, and they played into an
economic strategy that airlines used to compete against each other
because there was one other thing you could do to
use to your advantage besides the level of service or
the price of the airfare, and that was the frequency
of flights for specific routes. Now this really got going
(11:42):
with deregulation and the emergence of new airlines. Now passengers
could have a lot more options. When they were booking
a trip earlier, you might have a route that only
had two or maybe three flights per day between two cities,
so the passenger had to fit their schedule with the
airline schedule. But with more routes approved and more narrow
(12:04):
body aircraft in fleets, airlines had the chance to increase
the frequency between certain cities that had demand that warranted it,
and as you would imagine, most of the time, this
would involve cities that had regular traffic between them. You
weren't suddenly going to see an enormous increase in flights
to some city that was far out of the way
(12:25):
of everything else. Because there's no demand between two cities,
it makes no sense to operate hourly flights between them.
But for some routes that's exactly what did make sense.
So airlines began to compete by telling customers, hey, we
operate enough flights to your destination that you don't have
to worry about conforming to our schedule. We've got a
flight that fits your schedule. So this was the era
(12:49):
in which we saw the narrow body mid range aircraft
come into prominence, and that included the Boeing seven thirty seven.
The original seven thirty seven was introduced by Bowing in
nineteen sixty six. It was nicknamed a square airplane because
the length of the aircraft was the same as the
width of its wingspan. Both were approximately ninety three feet
(13:13):
or a little more than twenty eight meters. It's a
twin jet engine aircraft and the original seven thirty seven
had an engine mounted under each wing. This becomes an
important element when we get to the design of the
seven thirty seven Max. Now there are different versions of
the seven thirty seven that have different dimensions. The original
(13:34):
seven thirty seven one hundred innered service for the airline
luft Hanza, among others. United Airlines expressed interest in purchasing
some seven thirty seven's, but that airline wanted a slightly
longer version of the aircraft, so Boeing adjusted it and
then created a version of the seven thirty seven called
the seven thirty seven two hundred, and There are several others,
(13:58):
including the recent seven thirties even Max Okay so aircraft,
like the seven thirty seven from Boeing and the A
three twenty from air Bus, served similar purposes to act
as a short or mid range aircraft capable of carrying
around two passengers, which varies depending upon the aircraft's configuration.
By two thousand six, Boeing had been relying upon the
(14:20):
seven thirty seven design for forty years, when the company
began to consider the possibility of an entirely new design
to fill essentially the same function as the old, reliable
seven thirty seven. That decision was a huge one and
would require a lot of steps, So Bowing kicked the
idea down the road a few times, and then we
(14:40):
get to two thousand eleven and American Airlines ordering the
two hundred Airbus aircraft. It sent a signal to Boeing
that delays we're going to cost the company big time.
Now explain more in just a moment, But first, you know, guys,
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(15:03):
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seven thirty seven Max Alright. I left off saying that
Boeing concluded that developing an all new type of aircraft
wasn't going to pun intended fly. As Airbus began to
(16:51):
gain popularity among airlines and American airlines had as part
of its plan and order for a re engined seven
thirty seven aircraft. Boeing would need to focus on that effort,
and it abandoned the design of an entirely new aircraft.
It finally said, Okay, it doesn't make sense for us
to create a new aircraft from the ground up. Let's
(17:13):
go back to the seven thirty seven and make some adjustments.
This also brought with it a few other potential benefits.
Developing a new aircraft is time consuming and incredibly expensive.
Not only is the development process itself expensive, then there's
the certification phase, in which the aircraft must pass requirements
set by the various aviation authorities around the world in
(17:36):
order to be allowed to operate as a commercial aircraft.
And then there's the training phase. Pilots have to train
on the new aircraft to learn its systems and how
it flies. Not all aircraft behave the same up in
the air, and that means it's a really big deal
to invest in an all new type of aircraft. It's
asking for a lot of resources, both from the manufacturing
(17:57):
company and the various airlines out there. Updating and existing
design is far less daunting. The basic bones for the
aircraft are already there, and if the changes are within
certain parameters, you can get through regulations pretty easily. After all,
the base aircraft has already been through that process and
had been approved. Likewise, if the changes aren't dramatic, pilots
(18:20):
might be able to fly those planes without any real
additional training or having to go into any flight simulators,
because the aircraft, at least in theory, is going to
perform within the basic parameters of its predecessors. So there
are a lot of strong business cases for sticking with
a previously engineered design. Boeing's decision to stick with the
(18:40):
seven thirty seven was both more economical and, due to
the agreement it had reached with American Airlines, pretty much necessary.
One of the big goals Boeing had was to improve
fuel efficiency so that the seven thirty seven Max could
fly the same distance as older seven thirty seven's while
burning less fuel. That would also mean the seven thirty
(19:01):
seven Max could potentially have an increased range of flight
compared to earlier seven thirty seven's, and you could argue
that ultimately it was this push that would lead to
the tragedies of the two seven thirty seven Max crashes
that would ground the global fleet of seven thirty seven
Max aircraft. It's a sort of cascade effect where one decision,
(19:24):
that being to re engine the seven seven would lead
to other decisions that ultimately set the stage for catastrophe.
And by the way, this is all very easy for
me to say in hindsight, I'm not trying to suggest
that I would have spotted the potential for disaster before
it happened. It's only because it happened that we're able
to go back and analyze this and see where the
(19:45):
mistakes were made. But at the time it was not
necessarily that clear, at least not outside of Boeing. Boeing
chose for this new version of the seven thirty seven
some engines from a company called CFL. CFM is actually
a joint venture between g E Aviation and Saffron Aircraft Engines.
So in two thousand eight, CFM introduced a class of
(20:08):
engines they called the Leading Edge Aviation Propulsion Class or
LEAP l E a P. Boeing opted for the Leap
one B model of engines, which has a thrust range
between twenty three thousand and twenty eight thousand pounds of
thrust or between one hundred and one killing Newton's of
(20:29):
thrust and Newton is the amount of force required to
accelerate an object with a mass of one kilogram and
an acceleration of one second per second. CFM chose several
engineering advancements that contributed to better fuel efficiency and its
leap engines compared to older aircraft engines. That includes carbon
fiber composite components that are stronger than earlier materials at
(20:53):
a fraction of the weight, so while the engines are
big larger than previous seventh D seven engines, they don't
necessarily weigh as much as those older engines do. CFM
also used additive manufacturing, more commonly called three D printing
to produce those components. The leap engines also pre mix
(21:15):
fuel and air together before the mixture hits the nozzles
that enter the fuel into the combustion chamber, So older
engines would inject essentially amissed a fuel into the combustion
chamber and the mixing of the fuel and the air
happened inside the chamber itself. But according to CFM, that
meant lower fuel efficiency and greater emissions, So they say
(21:37):
that this new method cuts down on emissions and you
burn more of the fuel. The engines would give Boeing
the boost and efficiency needed to meet American airlines requirements.
In August two thousand eleven, Bowing officially announced the development
of this new version of the seven thirty seven, and
the company began to market the aircraft to various airlines.
(21:59):
By December two thousand eleven, Boeing found a customer in
the form of Southwest Airlines, which put in an order
for one fifty of the aircraft. Aircraft that were in
the earliest stages of development, mind you. From two thousand
eleven to two thousand fifteen, Boeing worked on the design
and production of the seven thirty seven Max. And here's
(22:20):
where we see some other decisions that would ultimately contribute
to the problems we saw when it entered service. The
new engines were larger than the previous seven thirty seven engines,
as I mentioned earlier, and traditionally those earlier seven thirty
seven engines would be mounted under the seven thirty seven's wings,
but these new engines were too big to do that
(22:40):
and still allow for adequate ground clearance between the bottom
of the engine and the ground itself, So that meant
the engineers had to figure out where to put these
engines on the body of a seven thirty seven, and
ultimately they decided to move the engines forward along the body,
ahead of the wings, and their position in such a
way so that the exhaust of the engines is directed
(23:02):
underneath the wings, which makes sense. You wouldn't want it
to go right up against the wings you melt your
own wings off. And also the way that their position
now means that the bottom of the engine has sufficient
ground clearance. But moving the engines forward had another consequence.
It changed how the aircraft moved in flight. Moving the
engines forward meant that in flight, the seven thirty seven
(23:24):
Max has a slight tendency to tilt its pitch upward,
in other words, to tilt its nose up towards the
sky in a climb. That can be a problem for
lots of reasons, but a big one is on takeoff.
I mean, obviously you're climbing in takeoff, and in that phase,
pilot's guide a plane into a climb to reach cruising altitude.
(23:45):
So you don't want a plane to overcompensate and tilt
further back than the plan to climb for lots of reasons,
but a big one is that it can cause the
engines to stall out. So for a jet engine to work,
you have to have air flow going through that jet
engine in sufficient quantities, so it has to be moving
(24:05):
there in a sufficient speed. Essentially, I covered this in
recent episodes, so I'm just going to do a quick overview.
In a jet engine, incoming air hits fan blades that
compress that incoming air, which then either flows in or
around a combustion chamber where the engine ignites fuel. The
(24:26):
resulting hot gases in the combustion chamber expand and then
force their way out of the chamber through an exhaust
nozzle in the back of the chamber, and as they
escape they hit rotors on the rear side of the engine,
and the rotors connect through a shaft to the fan
blades that are in the front of the engine. So
(24:48):
as that exhaust is coming out the back of the engine,
it hits the rotors, and the rotors turn because of
that rapidly escaping gas, and because that's connected by a
shaft to the blades in the front, it turns. The
fan blades in the front of the engine, and the
whole thing perpetuates itself because of this continuous burn inside
the combustion chamber. But for this to work, you have
(25:11):
to have a sufficient amount of air flowing into the
engine in the first place. This is also why it's
necessary to jump start a jet engine on the ground.
They forced compressed air through the jet engine in order
to get it going, because you cannot get it started
any other way. Now, if the plane were to tilt
too far in an incline when it's climbing up into
(25:33):
the sky, the angle of the engine compared to the
airflow would be such that you wouldn't get enough air
to go through the engine for it to maintain operation,
and that's why it would stall out. You would have
a lack of air to keep that whole process going.
Installed engines would clearly be a disaster. Once Boeing engineers
(25:53):
recognize the tendency for the seven thirty seven Max designed
to go into this unprompted tilt, they had to how
to address that problem, and their solution was a combination
of hardware and software. On the hardware side, they relied
upon sensors that would automatically analyze the difference between the
airplane's attitude in the air and the angle of attack.
(26:17):
So the angle of attack describes the angle of a
plane's wing with respect to airflow. Angle of attack is
a big component of lift, that's the force that keeps
aircraft in the air. The other major hardware component is
the aircraft's horizontal tail, which can tilt to change the
plane's pitch. By altering the orientation of this horizontal tail,
(26:40):
it could act as kind of like a rudder, except
a rudder for the horizontal access, not the vertical, and
the effect is that it could force the nose of
the plane back downward in one of these climbs, so,
in other words, it could affect the pitch of the airplane.
The software overseeing the whole operation of this, which would
monitor the data coming in from the sensors and then
(27:01):
send appropriate commands to the tail, is called the Maneuvering
Characteristics Augmentation System or m CASTS. So if you've been
following the story of the seven thirty seven Max, you've
likely heard the term m CAST thrown around now. In theory,
m casts would operate in the background and make the
seven thirty seven Max perform as if it were any
(27:23):
other type of seven thirty seven aircraft, so it was
designed to override pilot controls. But this also meant that
if the system were to erroneously detect that the aircraft
were in too steep a climb, the tail flap or
the horizontal tail rather could force the plane into a
dive and the pilots would be struggling to pull out
of it, and they'd have to figure out how to
(27:45):
do that, and that would also mean knowing how to
disarm the system. Okay, so Boeing was pushing hard to
get the seven thirty seven Max ready to compete with
the Airbus A three twenty neo aircraft. The f a
A helped expedite things. In two thousand fifteen, according to
the Seattle Times, the f a A managers put pressure
(28:07):
on the agency's safety engineers, telling them to delegate the
assessment process to Boeing's own staff. This, by the way,
it doesn't seem like it's completely unusual, but it did
come as something of a surprise to me. I did
not know that's how things worked, because, in other words,
what that means is the agency and charge of overseeing
safety passed that job along to a company that produced
(28:31):
the very thing the FAA was meant to oversee. And
that might sound like it might not be the best idea.
I happen to think it was a pretty bad idea now, granted,
as we are now seeing, a failure on the part
of a company to be completely honest and rigorous with
its safety assessment process can result in terrible tragedies for
(28:51):
passengers as well as real hardships for the company itself.
So companies like Boeing have a very strong incentive to
police themselves care late. However, it sounds like that's maybe
not what happened with Boeing's self assessment. Again. According to
the Seattle Times, the safety analysis understated how far the
im cast software could force the horizontal tail to move
(29:15):
in an effort to stabilize the planes pitch. The Times
reported that in reality, the software was able to make
the tail move more than four times further than what
the report indicated, meaning a much more dramatic change in
pitch than what Boeing was claiming in the report. And
Boeing's response to this was that initially Imcast would be
(29:36):
able to move the horizontal tail at an angle of
point six degrees. It turned out it was more like
two point five degrees, and Boeing said, well, it was
only upon further study that we realized in order to
pull out of a disastrous climb, you would need a
greater movement than just point six degrees, which is why
(29:59):
we increased it. But at that point we had already
written the report. Seems to me like there might have
been an addendum that needed to be added there, but
what am I to say? So the report did not
address how mcasts would reset after a pilot's response and
would go into another dive despite repeated manual attempts to recover. So,
in other words, if a pilot were to respond to
(30:23):
this unplanned dive and pull back, you know, activate the
control and pull back on it, then it would stop
the system temporarily, but it would just reset and start
the cycle over again, and it might get more dramatic
each time. The the amount of of of tilt that
the horizontal tail would take, and thus the amount of
(30:45):
dive the plane would go into, would get greater each time.
The criticism is that the safety measure had no self
correcting process that would discontinue the diving efforts after manual intervention.
It would just keep going into a dive. So the
argument is that there should have been a system in
place where if a pilot intervenes, it deactivates this process
(31:10):
that was not in place. The Times criticized that the
assessment stated that if the system were to fail, it
would merit a hazardous danger rather than a catastrophic one.
These have real meanings in safety assessments. Hazardous means that
the outcome could result in injury or death to a
(31:31):
small number of passengers in a plane. Catastrophic is essentially
a designation stating that such a failure would result in
the complete loss of the plane and everyone on board.
So Boeing was saying that a failure of the system
would merit the hazardous level, not the catastrophic level. So,
(31:51):
in other words, the criticism is that the report was
downplaying the actual outcome of a system failure. One other
major problem is that Boeing neglected to include information about
m casts in its operation manuals for the seven thirty
seven Max. Pilots didn't know about it, airlines didn't know
about it. It wasn't until after the first tragedy that
(32:14):
this would be amended. When we come back, I'll talk
about that accident and the following events. But first, let's
take another quick break. Perhaps because the f a A
delegated the safety assessment duties to Boeing, Perhaps because the
(32:36):
seven thirty seven Max was a variant on a tried
and true aircraft design that had been an operation for
at that point fifty years. Perhaps because simulations failed to
create the sort of scenarios that we would unfortunately see
unfold in the actual operation of the aircraft. The seven
thirty seven Max past certification without much hullabaloo. Then, to
(33:00):
be fair, it seems in more investigations that some of
those simulations actually did show some problems, but Boeing didn't
really address that at the time. There was also no
need to train flight crews on how to operate the
seven thirty seven Max, because in theory it behaves so
much like other seven thirty seven's, particularly the seven thirty
(33:22):
seven in G, which was the immediate predecessor of the Max.
Pilots reported that they essentially had to complete a one
hour course on a tablet and not even spend any
time in a simulator before they would be certified to
fly a seven thirty seven Max. However, you want to
lay it out. The end of the matter is that
(33:43):
the seven thirty seven Max received its certification and Boeing
began to deliver the aircraft to customers. One of those
customers was Melindo Air, a carrier based out of Malaysia
and a subsidiary of a larger airline called Lion Air.
On October twenty ninth, two thousand eighteen, Lion Air flight
(34:03):
j T six ten, which was a seven thirty seven
Max eight, crashed just thirteen minutes after takeoff from Indonesia.
The plane crashed into the sea off Jakarta. All one
eighty nine people on board died as a result of
that crash. Among them were twenty Indonesian government officials. The
(34:24):
plane had been in use for about two months. A
pilot had reported a problem with the aircraft right away,
requesting a return to the airport before they lost control
of the aircraft. The CEO of Lion Air at the
time reported that a different pilot had reported the same
plane for a quote technical issue end quote earlier on
(34:46):
that week, but that the aircraft had been cleared to
fly the following day. An investigation following the crash indicated
that one of the angle of attack sensors had malfunctioned
on the Lion Air flight, and it had mistakenly indicated
a dangerous change in pitch and an oncoming engine stall,
(35:07):
and none of those conditions were actually existing at the time.
But the im CAST software and system went into action,
forcing the horizontal tail to move the the the nose
of the plane downward and put it into a dive.
The pilot was unable to counteract that, and the plane
crashed as a result. Making matters worse was the fact
(35:27):
that Boeing had not indicated the im cast was even
a thing. The pilots had no way of knowing what
it was that was causing the plane's nose to dive
or how they were supposed to stop it. On November six,
two thousand eighteen, Boeing issued a report revealing im CAST
to pilots and airlines for the first time. The report
(35:48):
also gave instructions to pilots on how to override in
cast in the event of a failure. Not At this point,
it wasn't yet certain that im casts was at fault,
but the signs were starting to point that way. In
the meantime, Boeing continued to receive orders for the seven
thirties seven Max from various airlines and was still in
full manufacturing mode. One thing Bowing did that later drew
(36:12):
an enormous amount of criticism was to place some responsibility
on the pilots themselves, stating that they should have known
to cut off the switches to the planes stabilizers. But
analysts who looked at the recovered flight data for the
Lion Air disaster said that what the pilots had experienced
didn't look like a stabilizer runaway scenario in which an
(36:34):
element like the seven thirty seven Max's horizontal tail would
make a continuous, uncommanded movement. The Lion Air flight data
showed that the tail movement was not a continuous motion,
and then the pilots were able to use the controls
to pull up several times before the plane became uncontrollable.
The analysts contradicted Boeing, saying that it wouldn't have seemed
(36:57):
obvious to cut off the stabilizer controls based on what
was happening then. On March tenth, two thousand, nineteen, and
Ethiopian Airlines flight from Addis Ababa to Nairobi crashed not
long after takeoff. Air traffic control lost contact with the
plane just six minutes after it left the runway. All
one fifty seven people aboard that plane died from the crash.
(37:20):
Early analysis suggested that once again, this was a failure
of m CAST. Further investigation showed that the crew attempted
to follow Boeing's instructions to correct for the failure, to
no effect. One day after the crash in Ethiopia, China,
and Indonesia, authorities issued orders that all seven thirty seven
Max aircraft operating in those countries were to be grounded. Now,
(37:44):
at that point, it was not yet known that m
CAST was definitely at fault for that second crash. The
day after that, on March twelve, two thousand nineteen, Canada,
the EU, and India also ordered all seven thirty seven
Max aircraft grounded. The f a A in the United
States would follow suit one day later, on March thirteenth,
(38:04):
two thousand nineteen. At that point, investigators were seeing signs
that IMCAST did play a part in the second crash.
The U s Department of Justice began a sweeping investigation
into the matter, and particularly into the process of the
jets certification. How could it pass certification if it had
this incredible flaw. That investigation has uncovered other concerning details
(38:28):
about the issue, including the revelation that a Boeing pilot
had brought concerns about the flight system of the seven
thirty seven Max to the attention of Boeing officials back
in two six. Previously, Boeing management had maintained that they
had no idea that the flight control system could cause
a catastrophe, but pilot Mark Fortner said that while flying
(38:49):
simulations that incorporated m CAST, he had encountered cases where
the flight management system was, in his words, quote running
rampant end quote. The revelation of this pilot's warnings came
a little more than a week before Boeing CEO Dennis
Muhlenberg and John Hamilton's Boeing's lead engineer, were to appear
(39:10):
before the United States Senate and the United States House
of Representatives and back to back hearings. During those hearings,
officials accused Boeing of purposefully downplaying safety issues and concealing
potential problems in an effort to achieve certification as quickly
as possible and thus start selling planes as quickly as possible.
(39:32):
Those officials are also concerned about the f a a's
practice to deputize the very companies it is supposed to
certify in the safety assessment process. Now that's not to
say that the US government is now advocating for sweeping
changes in certification or or even going to come down
hard on Boeing, because it's not as simple as that.
(39:53):
At issue isn't just the fate of Boeing, which is
an enormous employer in the United States. That also means
that there's a whole lot of folks who are potentially
voters who could be affected by any massive problems that
Boeing faces, and politicians are a little squeamish about doing
things that could potentially upset voters. There are airlines that
(40:16):
have aircraft they can't use. They're dealing with this problem
to they're looking at lost revenue. And there are all
these companies that supply bowing with components like GE, you know,
one of the companies responsible for the seven thirty seven
max engines. GE has had its own share of problems recently.
You can listen to my episodes about General Electric that
published not too long ago to learn more about those.
(40:39):
Because the seven thirty seven max is effectively on hold.
It could potentially cost companies like Ge and others billions
of dollars. Boeing, for its part, has made major changes
to m CAST. A big one was that moving forward
in CAST will take into account both angle of attacks
sensor before changing the horizontal tails orientation. It would no
(41:03):
longer accept just one stream of data as being enough
to change the plane's pitch. One of the other major
criticisms directed at Boeing from a design level is that
the MCAST sensor was a single point of failure with
no redundancy, and when coupled with Boeing's self assessment that
a failure just represented a hazardous outcome but not a
catastrophic one, create a false sense of security. Another big
(41:28):
change is limiting how much the tail will move like
I said. The original safety assessment said the tail would
only move point six degrees, but in practice it was
more like two point five degrees at maximum. Boeing has
also stated that it is going to limit the system
to activating for a single cycle, as opposed to the
reset repeat process that was seen in both Lion Air
(41:49):
and the Ethiopian Airline crashes. Then there's the long tail
stuff that Boeing is going to have to deal with,
stuff like trust and perception. While Bowing has made efforts
to address the problems in its seven thirty seven Max
flight systems, the company's credibility has taken a hit, as
has the perception of the f a A. There's still
(42:11):
lawsuits against Boeing that are making their way through the
legal system that are a direct result of the seven
thirty seven Max disasters, and Boeing still has hopes that
the aviation agencies around the world will lift the grounding
of the seven thirty seven Max aircraft before the end
of twenty nineteen or in early twenty twenty. Meanwhile, the
(42:32):
company has another headache to deal with. In October two
thousand nineteen, reports came out that aircraft operators had discovered
cracks on the seven thirty seven in G aircraft, or
at least some of them now. As I mentioned earlier,
the seven thirty seven in G is a predecessor to
the seven thirty seven Max. It's been in service for
several years. It doesn't have the m CAST software or
(42:55):
the engine placement of the Max, and it remained in
operation with any problems. But in early October two thousand, nineteen,
U S officials ordered an inspection of seven thirty seven
in G planes that had completed more than thirty thousand cycles,
that is, more than thirty thousand takeoffs and landings. And
the whole point was to look at the section of
(43:16):
the plane where the wing attaches to the body of
the plane. It's a part of the plane that is
called and I swear I'm not making this up the
pickle fork. Several airlines outside of the United States also
began to inspect their seven thirty seven in G s,
even those that had not yet completed thirty thousand cycles,
and reportedly some of those aircraft have had cracks appearing
(43:39):
in the pickle fork as well. Boeing stated that out
of the one thousand, seven thirty seven in G s
that had been inspected so far, inspectors that only indicated
that five percent of them have had cracks. Still, it's
another indicator that things are not going so great for
Boeing right now. We'll have to wait and see how
(44:00):
this all plays out, whether or not the seven thirty
seven Max will return to service, whether or not people
will trust it. You've had a lot of us politicians
already saying that they would not get on a seven
thirty seven max to take a trip based on what
they've seen. So there may be an inherent trust that
ends up being an enormous barrier to the seven thirty
(44:22):
seven max, even if the technology is proven to be safe.
So that's a huge issue. Once you've eroded trust, it's
very hard to rebuild. So we'll have to wait see
how that turns out. I am very curious to see
it myself. I've definitely been interested in this subject. I
fly fairly frequently, and knowing about this is something that
(44:44):
I think is important. Um, it's also something that fills
me with anxiety if I'm being perfectly honest, but I'd
rather know than not know. Anyway, that wraps up this
episode of tech Stuff. If you guys have suggestions for
future episodes, send me an email. The edge says tech
stuff at how stuff works dot com, or you can
tell me on Facebook or Twitter. The handle for both
(45:06):
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We also have a link to our online store where
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and I will talk to you again really soon. Tex
(45:32):
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