Now we can continue doing a brief summary
of the history of safety.
So here we can see a representation
of the three ages of safety
as it was stated by Yale and Hovden.
We can say that the three ages of safety,
ages of safe safety started in 1769
when James Watt received his first patent
for the steam machine.
From then on,
humans started to build more and more complex machines.
So during that age, the main threats for safety
came from technology itself.
So the main concerns during this age
were to protect machinery from failure.
But there was an important event
or point for safety in 1893
when the "Railroad Safety Act" was published
which stated the need to blend both
technology safety and government regulations.
This age worked pretty well while the machines
were not complex.
But as the years passed,
all the machines started to be more and more complex.
During this age, we started to build nuclear power plants
or the aviation was
being used more and more commonly.
So as I have said, this worked pretty well
until the end of the 70s.
Because in 1979 Three Mile Island disaster happened.
Three Mile Island was a nuclear power facility
in Pennsylvania.
This accident or incident
demonstrated that there were not just technological risks.
Three Mile Island went under all the safety regulations,
including a probabilistic risk analysis.
But an accident took place.
Then they discovered that also humans can do things,
positive or negative under challenging situations.
This was the beginning of the human factors age.
And the idea was to include human factors
and the starting point was the PRA.
They used the PRA or Probabilistic Risk Assessment,
in order to develop the human reliability assessment or HRA.
So during this age, there was a philosophical separation between
reactive safety, that is the safety that investigates the accident,
and proactive safety, that is the risk assessment.
Because the later
was based on probabilities of an accident to happen in the future.
This worked until the Challenger accident happened in 1986.
That means,
that this age lasted roughly 6 years.
After the Challenger accident,
there was the Chernobyl incident in the same year.
This age known as the age of human factors lasted roughly a decade.
After those events or accidents,
we also had in the same year, the Los Rodeos Airport accident,
where two planes crashed,
while one was taking off and the other was landing on
due to a bad communication between the control tower
and the aircrafts.
So it was clear
that not only the technology and not only human actions
were necessary.
But it was necessary to include the management of the organization
in all the considerations for safety.
And that age lasted more or less until 2011
when the Fukushima accident took place in Japan.
After that, some people have started to say that we need to be in a new age,
the Inter-organizational Age.
That means, that not only the organizations that run airports,
aircrafts, nuclear power plants, ande etc...
have something to say about safety.
Everybody who is concerned about safety in an industry
has to work together.
Now we can continue with an example.
Let's see this example.
Here we are going to see how Safety I works normally.
Qantas flight 32 was a passenger flight
that suffered an uncontained engine failure
and made an emergency landing at Singapore Airport.
It was the first failure of this kind for the Airbus A380.
The world's largest passenger aircraft and the most Airbus advanced model.
During the flight, an engine suffered an explosion.
Parts of the engine were released and damaged the wings.
As you may know, the wings carry the fuel tanks.
So the fuel tanks were damaged or pierced,
provoking minor damage to the wing,
but causing a leakage in the full tank.
And the fuel fired.
The rest of the engines were working properly.
So, they made the landing.
That was the event.
After an event, according to Safety I,
there must be an investigation.
So the Australian Transport Bureau or Safety Bureau,
and Rolls-Royce, that was the engine manufacturer,
started an investigation.
And they found several causes which provoked the accident:
fatigue-cracking in stub-pipe due to a missile misalign counter,
oil liquid and fire
and release of intermediate pressure turbine disc.
And they said that is issue was specific to trent 900.
Here we have two things.
The plane was at Singapore for months
while it was being repaired, and took a lot of money to do it.
But also,
after that, they thought that they have found the causes and effects
which lead to the explosion and explained the whole event.
So as a result of the investigation,
it was stated that it was a specific issue to Trent 900 engine.
So after running...
they gave a lot of tips in order to keep
all the planes with that engine on the air.
But after several investigations,
they run additional tests.
And they discovered that on all those tests,
53 engines of that model had to be removed from service.
Eleven due to out of Tolerance oil feed stock pipes,
and 42 due to lack of measurement records
relating the oil feed stock pipes.
Finally, after going through all these,
we had a huge explosion in a plane with all the problems,
we have to repair the plane,
we have to take all the passengers to new planes,
we run a whole investigation,
and finally the solution, after several tries,
was to remove the engines.
That's not pretty good from an operational perspective.
So it can be seen that they followed the normal domino effect.
They based their safety in several barriers
as it was stated in the Cheese barrier model.
But there is always a trajectory for an accident to happen in that model.
Now we are going to try to approach this
using Safety II.
But first, we have to know how safety II works.
So let's continue.