"Hello, friends!" 12th November 1996. 3:55 PM. The city of Shymkent in Kazakhstan. A chartered Kazakhstan Airlines aircraft took off from this city. Flying towards New Delhi. Several small traders from neighbouring Kyrgyzstan were on board. "They were going to India to buy wool," so that they could bring it back and sell it in Central Asian markets. "Around the same time," "in Delhi's Indira Gandhi International Airport," A Saudi Airlines flight was getting ready to take off. "There were 312 passengers on the flight," of whom 231 were Indians. "They were blue-collar workers," construction workers or domestic workers. "On their way to Saudi Arabia to look for work," so that they could earn money for their families. The Saudi Airlines flight took off from the Delhi airport. "That evening, Air Traffic Controller VK Dutta was on duty."
"He was communicating with both Saudi and Kazakhstan
planes," and was guiding them. He was the one to give clearance to the Saudi
airplane to take off from the Delhi airport.
"A few minutes later, the pilots of the Saudi plane reported to
him," "that the plane had
reached the height of 10,000 ft." "They
request clearance to go up to 14,000 ft."
Dutta grants permission. "On
the other hand, the Kazakh aeroplane wants to land." Dutta tells the Kazakh aeroplane "to remain at the height of 15,000
ft." "And not to descend any
further," "because the Saudi
aeroplane was flying at 14,000 ft."
"There needs to be at least a vertical distance of 1,000 ft between
2 aircraft." "On his screen,
VK Dutta sees the two aircraft as blinking dots." "Over the next few minutes, he sees how
these two blinking dots" keep
getting close to each other. "And
just like that, the two dots fused into one." And then disappear altogether. This was the point when Dutta realised that something terrible had happened.
"Around 100 km from Delhi," lies the small city of Charkhi Dadri. "That evening, the residents of this
city saw" "a bright flash of
light in the sky, akin to lighting,"
and then they hear the thunder. "Before
they could even think about what was happening," iron debris started falling on them. The two planes crashed into each other. This was the first and only mid-air collision
in India. And the worst air disaster in
India's history. """As
the search for bodies among the wreckage continues," several Muslim victims of the disaster were
buried in the mass grave. "Nearby,
70 funeral pyres were being prepared"
for Hindu cremations. "Investigators
have started work on the flight recorder,"
these so-called black boxes of both aircraft. "To find out more about what happened
just before the crash."""
"""Even as a judicial enquiry ordered by the Prime
Minister Mr Deve Gowda," "begins
its probe into the disaster," experts
are looking at various theories that could have caused the tragedy. """The radar which we have
today, in Delhi," "is a
primary radar," "and is a
fairly old one.
"To understand the depths of this story," "about why it happened," "and how it impacted the aviation sector
in India," we first need to have
some basic knowledge. We'll have to
understand the rules of the sky. "Similar
to the vehicles driven on the roads,"
"and roads built on set paths," with the road divided into traffic lanes. "Similarly, there are set paths in the
sky for aeroplanes." All aircraft
need to follow these set paths. These
paths are known as Airways. "Similar
to the roads being divided into traffic lanes," airways are divided into air corridors. Imagine if there was only one traffic lane on
the road for all vehicles. What would
happen? There would be a high chance of
an accident occurring. "For the
same reason, there are multiple corridors in the airports" for the incoming aeroplanes and the leaving
aeroplanes. So that there is a
restricted scope of an accident taking place.
"Apart from this, the height at which the aeroplanes fly," is called the flight level. "According to the Internation Civil
Aviation Organisation's standards,"
"the flight level between 2 planes," "there should be at least 1,000 ft of
separation." "It means that
one aircraft should be, vertically, at least 1,000 away from another." "Apart from this, there needs to be a 14
km radius for safety."
These are the basic rules of the game. "And we come to the next question," who ensures that all aeroplanes follow the
rules at all times? This is ensured by
the Air Traffic Controllers. The ATCs. "The ATCs monitor the flying aeroplanes
from the ground," "their
position, speed, and their altitude (height)." "It is very important to check
these," so that the aeroplanes
could be kept safe. Air Traffic
Controllers can see it on their screens as blinking dots. The aeroplanes look like blinking dots on the
radar. "So the next question
is," how do the ATCs get this
information? The details of every single
plane. They get this information from
the RADAR. Radar is a device that uses
radio waves to detect objects that are
at a distance from it. "Radar can
detect aeroplanes, spacecraft, and even tornadoes." "But the radar used to detect
aeroplanes," can be classified into
2 parts. Primary radars and secondary
radars. Primary radar is a system for
which "antennas have been placed at
strategic locations all over the world,"
"those antennas emit radio waves," "and when the radio waves return after
being reflected by the aeroplanes,"
they calculate the distance of the plane based on the time taken by the
radio wave. "Primary radars can
tell you the horizontal distance of an aeroplane," but they can tell you the altitude of the
aeroplane.
Secondary radars are used to calculate the vertical
distance. This is a complex bit of
technology. "A transponder is
placed on top of an aeroplane," "And
the radio wave signals from the primary antennas, " "are caught by the transponder," and responds with its own signal. "With this, it provides more
information" about the position of
a flight much more reliable information. The technology of the secondary radar is
quite new. "During the 1990s, when
the incident took place," the
secondary radar wasn't used then. The
ATCs relied solely on the data from the primary radar. But the data from the primary radar wasn't as
reliable. It could tell you only the
approximate distance between 2 planes. "To
find out the exact altitude then," "the
ATCs constantly communicated with the pilots," and the pilots would inform them about the
altitudes. "And then, the ATCS
would jot down the height and speed parameters, " they would use it to manually calculate and
chart the flight path. Can you imagine
this? "In a busy airport like
Delhi," "where 20-30 flights
land and take off every hour," how
tedious this work would have been for the ATCs.
It was a stressful job. "It
is still a stressful job," but it
used to be even more stressful back then.
And it wasn't that the ATCs weren't trained.
They were very educated and extensively trained. "but after a point, the workload and
stress become too much for any person."
Delhi Airport's Deputy Director JS Ahuja had said that "This is why at one point in the
1990s," ATCs were considered to be
the most stressful work in the world. More
stressful than the doctors. Even more
than racecar drivers. It was the same in
India. The job of the ATCs was extremely
stressful. "Today, the dependence
on humans has reduced by a lot." "Data
analytics is used, machines are used for all these." "In fact, data analytics is used in
nearly all fields." "In fact,
I am taking classes on Google Business Analytics, on Skillshare." So that I can better understand YouTube. And use it to grow more efficiently"on
the ill-fated evening of 12th November,"
What were the mistakes? And who made them? Mistakes that led to this deadly disaster. 2 planes crashed into one another.
"The thing is that friends," there is a popular theory regarding
accidents. The Swiss Cheese Model. "As you know, this is how Swiss Cheese
looks." It has many holes in it. "If you stack the cheese slices on top
of each other," the holes don't
exactly match with each other. "You
can look across the slices," "because,
the possibility that all the holes would align, " is very negligible. "Even if one hole doesn't align," you won't be able to look through it. It will be opaque. It's said that it is the same with accidents. The accidents that take place aren't because of a singular reason. "Rather, multiple reasons align at the
right time." "Well, it'll be
the wrong time, I suppose." "Series
of small mistakes that happened at the same time," which led to this major disaster. "Even if one of these mistakes didn't
happen," this disaster might have
been prevented. "On the historic
evening of 12th November," it
happened. A series of small mistakes
added up to this disaster. "First
of all, the Indian officials thought"
"the Saudi aeroplane hadn't followed the instructions
properly," "that even though
they were instructed to stay at 14,000 ft," "the plane might have gone up to 15,000
ft," and crashed with the Kazakh
aeroplane. "But when the black
boxes of the planes were found," "flight
data recorder revealed," "the
exact recording of the conversations between the pilots," "and they found that the Saudi
aeroplane," "was at 14,000
ft," "and the crash between
the two aeroplanes," "was at
14,000 ft." "It meant that the
Kazakh aeroplane," "had
descended from 15,000 ft to 14,000 ft."
Why? "VK Dutta had told the
pilots of the Kazakh aeroplane," "to
not descend below 15,000 ft." The
audio recording from the black box showed
"that the pilots in the Kazakh aeroplane," weren't even listening properly to what the
ATC was saying. "They were
complaining to each other about the traffic in Delhi," and the traffic hangups in Delhi airport. "The second thing they found," was that these Kazakh pilots didn't even
understand English properly. "In
fact, there was a radio operator on the plane," "who was translating the messages from
the ATC," "from English to
Russian, so that the pilots could understand."
The report of the
accident concluded that "the
instruction from the ATC," was
subjected to an error of understanding. "The ATC told them to maintain the
flight level at a certain altitude,"
but they misunderstood it. Or
they thought that the instruction was for some other flight. "They misunderstood the
instruction," and so they
descended. "Friends, it was the
time when the Soviet Union had recently broken up," "and Kazakhstan was a new country," "and the Russian National
Airlines," was demerged into the
airlines of several countries when the
Soviet Union broke up. The reputation of
these airlines wasn't good at all. "It's
said that once," a pilot gave the
controls of the plane to his child. There
were stories of pilots doing vodka shots before landing. "Overall, the reputation of Russian
pilots wasn't good." "But the
bigger question here, is that," "one
misunderstanding could lead to a disaster of this scale, " were the designers of the system relying on proper communication between the
pilots and ATCs? The other problem was
the air corridors that I talked about in this Blog. "One
air corridor for the departing aeroplanes," and one for the incoming planes. But it wasn't so in the 1990s. There was only one air corridor. "Third: as I told you, secondary radars
weren't used at the time," so the
ATCs had to rely on the communication with the pilots.
"After this horrific air disaster happened," "our government, the Indian
officials," "and aviation
experts all around the world," learnt
from this. "They made many
significant changes to the system,"
so that such an accident wouldn't be repeated. "And thankfully, till now, such a mishap
hasn't occurred in India again." "After
this, aeroplanes haven't collided mid-air." The reasons?
First: there are now separated air corridors for the incoming and departing planes. "Second, the secondary radar," "the Directorate General of Civil
Aviation," is a statutory body of
the Central Government. For years it had
been recommending "that secondary
radars should be installed on aeroplanes,"
but the government didn't pay any heed.
"But as one official said,"
The government was willing to take some action. "The government made it mandatory for
every flying aircraft," to be
installed with the TCAS.
Traffic Collision Avoidance System. TCAS. "5
months after the Charkhi Dadri accident,"
"the Civil Aviation Minister CM Ibrahim announced in the Lok
Sabha," "that after 31st
December 1998," "all 30+
seater aircraft in India," have to
be compulsorily fitted with the TCAS. "It
is basically a system that," "rings
an alarm in the aeroplane," "if
any aircraft gets closer than 1,000 ft of vertical distance." Even more important than that is that "once the alarm is deployed," this system informs the pilot "of the direction to fly in, so that the
1,000 ft distance can be maintained."
"So if another aircraft approached you from below," "this alarm will ring, and it will tell
the pilot to fly upwards." This was
a major step for India. "Because at
the time, the TCAS technology was very expensive." Many countries complained that "they couldn't fit their aeroplanes with
TCAS,"
because it was very expensive for them. But India stood its ground. "And eventually, other countries had to
implement this system in their aeroplanes too." "The third issue raised by this
accident," was the language and its
nuances. "When someone
speaks," how well can the person
listening to it understand it? Might it
be misinterpreted? "The potential
misunderstanding between the ATC and pilots," how can it be avoided? "More than half the countries have their
airlines," "their pilots and
ATCs," "who communicate in
their local language," "people
from so many backgrounds and cultures,"
"how can they communicate with each other," so that there is no misunderstanding? What can be the solution? "In 1998, India raised this issue in
front of the International community,"
in front of the ICAO. It was
proposed that every pilot would "have
a minimum level of English proficiency,"
to help them communicate. It was
debated extensively. "Because in
many countries, English isn't the first language." What could those countries do? "But some language had to be
chosen," or else there would always
be miscommunications. And so English was
eventually chosen as the international
language. "Today, if any pilot has
to fly an aircraft internationally,"
it is mandatory that they are well versed in English. An interesting question is that why was English chosen?
"Why is English the most popular, the number one
language in the world?" "I
have actually made a detailed blog on this," "you can watch it after this blog," the link to it is in the description. "The rule is that to fly
internationally, English is a must,"
"but if it's a domestic flight, within the country," the rule will not apply. "Pilots can use their national languages," to communicate with each other. "Basically, if we go back to the Swiss
Cheese model," the Indian
government tried "along with the
aviation organisations across the world,"
to fill up every possible hole in the Swiss Cheese model. So that there is no such accident in future. "And fortunately, till now," there has been no other mid-air collision. This is the basic reason. "Today, when you wonder," "why do two aeroplanes flying in the sky
collide with each other," "why
there aren't such accidents," this
is the reason. It's not that all
aeroplane crashes have been prevented. We
still witness some aeroplane crashes. "Like
this plane crash in China," "I
made this blog on it," or the
Malaysian Airlines crash. The reasons
for those crashes are different. Those
may not be solved this easily. "To
understand those reasons, you can watch these blogpost." Thank you very much!