-
- [Petter] Aircraft accidents
-
are always caused
by a combination
-
of several factors and the thing
-
that gets the sequence rolling
-
is often something
simple and mundane.
-
But this is the
first time I've ever come
-
across a single letter kicking it off.
-
- [GPWS] Sink rate. Pull up.
-
- Stay tuned.
-
When you hear the word Tenerife
-
in aviation context,
people almost always think
-
of the world's worst aviation disaster,
-
the collision between two Boeing 747s
-
at Tenerife's Los Rodeos
Airport back in 1977.
-
But the island of Tenerife,
-
the largest of Spain's Canary Islands,
-
actually suffered a string of disasters
-
between the 1950s and 1980s,
-
who collectively claimed 950 lives
-
and that infamous runway collision
-
was just the worst one of those.
-
So today I will tell you the story of
-
the last major
incident to happen there,
-
a story that took place on
a rainy spring day back in 1980.
-
And this one, I think a lot
fewer of you have ever heard of.
-
In the morning of the 25th of April 1980,
-
the crew of Dan-Air Flight 1008
-
were preparing to depart
from Manchester in England
-
on a charter flight,
bringing tourists down
-
towards Tenerife North Airport,
-
then known as Los Rodeos.
-
During the 1970s and '80s,
-
Dan-Air was one
of Britain's largest operators
-
of inclusive tour flights,
chartered by tour operators
-
to transport fixed groups of people
-
down to popular holiday destinations
-
in Southern Europe and North Africa.
-
Among the aircraft types operated
-
by Dan-Air was the mighty Boeing 727,
-
and Dan-Air were
actually the first British airline
-
to import this model,
which had then had
-
to undergo several unique modifications
-
in order to
meet British safety standards.
-
Now it would later turn out
-
that the 727s were a
financial disaster for Dan-Air,
-
but by 1980, that was
not yet very obvious.
-
The aircraft that the
crew were going to operate
-
on this day was 14 years old
-
in generally good condition
-
and could seat a
maximum of 144 passengers.
-
So with a total
of 138 passengers booked,
-
it was almost completely full.
-
The crew consisted
of five flight attendants
-
and three pilots, meaning that in total,
-
there were going
to be 146 people on board
-
once the flight got on the way.
-
The pilot in command was a very
-
experienced 50-year-old captain
-
who had around
15,300 total flight hours,
-
which included almost 2,000
on the Boeing 727.
-
He had flown this route
down to Tenerife North
-
a full 58 times before this flight,
-
making him very familiar
with it in general.
-
But as we will soon see,
-
being familiar with the
destination doesn't mean
-
that it can't throw a few surprises.
-
His second-in-command
was a 34-year-old first officer
-
who, on this day, had
about 3,500 hours in total,
-
of which 618
were flown on the 727.
-
And the third flight crew member
-
was a 34-year-old flight engineer
-
whose experience was similar
to that of the first officer.
-
Now all of the pilots had been off
-
for more than
24 hours before this duty
-
and the scheduled departure time
-
was at a very civilized hour,
-
so there's no reason to believe
-
that fatigue played any role
-
in what was soon about to happen.
-
Now instead the crew were
likely in a quite good mood
-
as they completed their
normal pre-flight activities,
-
checking weather,
NOTAMs and flight plans,
-
which all looked okay.
-
It looked like it was going
to be a very pleasant flight
-
down towards the Canary Islands.
-
So after having boarded everyone
-
and completed the pre-flight set up,
-
the crew started up their engines
-
and taxied out for takeoff
from Manchester at time 9.22 am,
-
with the captain as pilot flying
-
and the first
officer as pilot monitoring.
-
Now the climbout and cruise phases
-
of this flight went off without a hitch,
-
but the pilots then
likely started preparing
-
and briefing for the approach
-
a bit earlier
than usual on this day.
-
And that was because
they had seen,
-
during their pre-flight briefing
-
that the approach
they had ahead of them
-
was possibly going
to be a little bit unusual.
-
You see, in the Canary Islands
-
the prevailing winds normally blew
-
from the Atlantic Ocean in the west,
-
causing most flights to approach
-
from the east using Runway 30
-
in order to land with a headwind.
-
But on this afternoon,
the wind was instead blowing
-
from the other direction, from the east,
-
forcing inbound aircraft to approach
-
the reciprocal Runway 12 instead.
-
Now we don't know how
many times the captain
-
or the other crew members
-
had actually used
Runway 12 in the past,
-
but it was likely not something
that they did very often.
-
And to make things even worse,
Tenerife North Airport was,
-
and still is, notorious for its frequent,
-
fast-building fog that can appear
from nowhere within minutes.
-
The airport sits at
2,000 feet above sea level
-
on a shoulder between two mountains,
-
and the marine fog
that forms over the ocean
-
frequently collides with
the western slopes of Tenerife
-
and then gets funneled
-
through the gap
directly over the airfield.
-
But like I mentioned before,
-
on this day the reported
weather at the airport
-
was more or less okay, with
around six kilometers of visibility
-
and scattered clouds at 400 feet,
-
broken at 800 feet,
and further scattered clouds
-
at 1,100 feet with some light drizzle,
-
not great for sunbathing,
-
but good enough for normal landings.
-
But these cloud layers also meant
-
that higher up on the mountainsides,
-
the fog was extremely thick,
-
so thick in fact that a
weather station located
-
at a close to 8,000 feet elevation
-
on the mountainside
reported nil visibility.
-
This meant that the very
high terrain south of the airport
-
would be completely obscured,
-
including the nearly
12,200-foot Teide Volcano,
-
which is the defining
geographical feature on Tenerife.
-
Because of that,
the minimum safe altitude
-
in the airspace south
of Tenerife North Airport
-
was 14,500 feet,
which is worth remembering.
-
Anyway, as the flight
near the Canary Islands,
-
the first officer made contact
-
with the Las Palmas
Area Control Center,
-
who soon cleared them
to descend down to 11,000 feet.
-
The first officer read this back
-
and the crew initiated the descent,
-
and after they reached that altitude,
-
they contacted the Tenerife
North approach controller
-
and reported that they were
now 14 nautical miles
-
away from the Tango
Foxrot November VOR beacon,
-
and that they were ready
-
to receive their approach instructions.
-
Before we continue here,
-
it's probably worth explaining
a bit more about
-
the different approach aids
-
that the crew were now going to use
-
as well as their procedures.
-
A VOR beacon, where VOR stands for:
-
Very High Frequency
Omnidirectional Range,
-
is a type of radio navigation beacon
-
that was very widely used
in the days before GPS
-
and is actually still quite common,
-
especially here in Europe.
-
These VORs emit signals
hat are modulated differently
-
depending on the
direction of the emission,
-
which allow the VOR
receivers on board aircraft
-
to determine the
precise magnetic bearing
-
from the VOR to the aircraft.
-
This enables the pilots
to navigate using imaginary lines
-
or radios defined
by a particular bearing
-
from the beacon.
-
So, for example, the 270 degree radial
-
from the VOR points
due west and so on.
-
A lot of airports have VORs installed
-
to help pilots locate the airport
before starting to maneuver
-
for the approach, and
it can also be used
-
to align the aircraft with
the runway as an approach aid
-
if an instrument landing system,
ILS, is not available.
-
But in this case, the
Tango Foxrot November VOR
-
was not actually located at the airport.
-
Instead it was sitting on a hilltop,
-
a few miles northeast of the airport
-
in order to maximize
its detectable range.
-
Located at the northeast
end of Runway 12-30,
-
there was a less-sophisticated
beacon called an NDB locator
-
with the Morse
code identifier Foxrot Papa.
-
A non-directional beacon, or NDB,
-
is a radio aid that can be tracked
-
using an automatic
direction finder, an ADF,
-
and this is a very simple
instrument which just points
-
in the direction that
a signal is coming from,
-
but it doesn't
contain any radial information,
-
which makes the NDB navigation less
-
precise than navigating using a VOR.
-
In this case, because the
Foxrot Papa beacon was used
-
to mark the entry point
to the approach procedure
-
for Runway 12, it was
also known as a locator
-
rather than just an NDB.
-
And in order to approach Runway 12,
-
a flight inbound from the
northeast like this flight was
-
would normally need to fly first
-
via the Tango Foxrot November VOR
-
and then turn southwest onto Radial 255
-
directly towards
the Foxrot Papa NDB.
-
After reaching the Foxrot Papa,
-
the aircraft should then turn
right onto an outbound heading
-
of 302 degrees, which
would take it out over the ocean,
-
before making
a teardrop course reversal
-
to the left back towards the airport.
-
And from that point, the
aircraft would be in a position
-
to pick up the instrument landing system,
-
which would then guide
-
the aircraft the rest of
the way down to the runway.
-
Now this was quite
a bit more complicated
-
than the more commonly
used Runway 30 approach,
-
which just involved flying to
an NDB called Tango X-ray,
-
from where the instrument landing system
-
could then be
picked up immediately.
-
Now the reason that these procedures
-
had to be flown this way
-
was that there was no radar
available at Los Rodeos Airport,
-
so all approaches
had to be intercepted
-
using procedural arrivals.
-
But then again,
flying procedural approaches
-
would not have been
very uncommon back then,
-
and there was nothing in this procedure
-
that was particularly out of the ordinary,
-
except maybe that high
terrain to the southwest,
-
which I mentioned before.
-
And when we're on the
subject of things
-
that are out of the ordinary,
-
have you noticed that some countries
-
have now blocked the ability
-
to make video calls
from within their borders?
-
Well, I have, and that was
a bit of an issue recently
-
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-
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-
But luckily, I had today's sponsor,
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Thank you Nord,
and now where were we?
-
Yes.
-
After establishing
contact at time 13:16,
-
the Tenerife North
Controller cleared the flight
-
to descend down to 6,000 feet
-
in preparation to cross
Tango Foxtrot November
-
and then to enter
the approach procedure.
-
The captain dialed in
the new cleared altitude,
-
the flight engineer reduced
thrust in order to descend,
-
and the first officer then reported
-
when the aircraft was
seven nautical miles away
-
from the Tango Fox November beacon
-
in order to get further instructions.
-
At that same time, he
also requested the local air pressure,
-
QNH, in order to
get the correct reference
-
to the altitude above the sea,
-
and also the QFE,
which would give him
-
the altitude reference
over the airfield.
-
Once those values
had been received and set,
-
they were then cross-checked
-
in accordance with
their standard operating procedures,
-
and the captain now also suggested
-
that the first officer should tune
-
the ILS frequency on
his navigational radio box,
-
and he also confirmed
that the outbound heading
-
after Foxtrot Papa
would be 302 degrees.
-
So at this stage,
everything was completely normal
-
and the crew seemed
to have a good grasp
-
of the procedure they
had in front of them.
-
But just a few miles ahead,
-
an island-hopping
turboprop belonging
-
to Spain's flag carrier,
Iberia, was also an approach
-
to Runway 12, and the crew
on board that aircraft
-
were communicating with
the controller in Spanish.
-
Now the pilots of Flight 1008
didn't understand Spanish,
-
and from their conversations,
-
it doesn't seem like
they paid much attention
-
to that aircraft at all.
-
Instead, they continued to
monitor their position,
-
relative to the Tango
Fox November VOR,
-
and at time 13:18:15,
-
the captain called out,
"Just about to go overhead."
-
The first officer then reminded
-
the captain that the procedure called
-
for them to leave Tango
Fox November on Radial 255.
-
But as it turns out,
-
the aircraft actually passed a
little less than a mile east
-
of the VOR, and after passing abeam it,
-
they were also slow
to make the right turn,
-
which meant that they never
-
actually intercepted that 255 radial.
-
Now, we can never know
for sure why this happened,
-
but it was most likely done on purpose.
-
You see, the distance
-
between Tango Fox November
and Foxtrot Papa was very short,
-
and Flight 1008 was traveling
-
at an airspeed of around 250 knots
-
when they passed abeam to the VOR.
-
Today, we wouldn't fly that fast
-
when starting a tight
procedure like this,
-
since our aircrafts are now very slippery
-
and take time to decelerate.
-
But older aircraft like the 727
-
had much less effective wings,
-
which meant that they could
easily keep the speeds up high
-
for longer, since the speed
would just rapidly bleed off
-
when the thrust levers were closed.
-
This also meant that most jets
-
approaching Tenerife back then,
including this one,
-
would normally overshoot
this first turn slightly
-
before correcting course
in order to be able
-
to intercept the 302 outbound course
-
from the NDB at a slightly
more comfortable angle.
-
There was so little time
between Tango Fox November
-
and Foxtrot Papa that
they probably wouldn't be able
-
to intercept the radial anyway.
-
And on top of that, if they
flew directly over Foxtrot Papa,
-
they would potentially overshoot
the pattern significantly,
-
which could take the aircraft
-
into the area south of the airport
-
where the minimum
safe altitude was 14,500 feet.
-
Now, this is obviously not how
this was supposed to be done.
-
A lower speed would have
solved all of those issues,
-
but sometimes, procedural
shortcuts like this can start
-
to creep in due to
pure convenience and time saving.
-
And if I was to guess, this was likely
-
the reason that the captain
of this flight flew a bit wide
-
around the Tango Fox November.
-
Now, due to some radio chatter
-
with the Hapag-Lloyd flight
-
that was taking off from Los Rodeos
-
plus some other distractions,
-
the flight crew didn't actually report
-
crossing Tango Fox November
-
until 33 seconds after they
had passed abeam hit.
-
And like I mentioned,
-
Tenerife North Airport
didn't have radar at the time,
-
so position reports like this
-
were the only way for the controller
-
to determine where
the traffic was located.
-
As a result, when the crew reported
-
that they had just
passed Tango Fox November,
-
the controller realized that
the 727 was traveling so fast
-
that it would risk getting too close
-
to the slower Iberia
turboprop in front of them
-
if he didn't do something.
-
So he hastily decided
to put Flight 1008
-
into a holding pattern
-
in order to ensure
sufficient traffic separation.
-
At time 13:18:54,
-
the approach controller
transmitted the following message,
-
"Roger, the standard
holding overhead Foxtrot Papa
-
is inbound heading 150,
-
turn to the left,
call you back shortly."
-
And this would end
up being the critical moment
-
that put the accident
sequence into motion.
-
So let's take a moment to analyze why.
-
Despite the controller's statement
-
that this was a standard holding,
-
there was actually no officially
published holding pattern
-
around the Foxtrot Papa beacon.
-
There was a published holding
-
around Tango Fox November,
-
as well as around Tango X-ray,
-
forming part of the go-around
procedure for Runway 12,
-
but Flight 1008 was not in
a position to enter any of those.
-
Instead, the controller essentially
-
invented a holding pattern
based on Foxtrot Papa,
-
and he did so so quickly
-
that this was likely not the first time
-
that he had used
this particular pattern.
-
Now, it's not wrong or illegal
to make up holding patterns.
-
In fact, that happens all the time,
and it's perfectly okay
-
as long as it doesn't cause any issues
-
with terrain or traffic separation.
-
But the issue here
was that the controller said
-
that this was a standard holding,
-
which would imply that
the holding could be found
-
in the published approach chart,
-
and therefore needed to
be verified by the pilots.
-
On top of that, the entry
-
into this suddenly-proposed
holding pattern
-
would not be very simple
-
from the position that the
aircraft was now coming from.
-
What the controller
wanted the aircraft to do
-
was to join a left-hand holding
pattern over Foxtrot Papa
-
with an inbound course of 150 degrees
-
and an outbound
course of 330 degrees.
-
If it was flown that way,
-
it would keep the airplane
over relatively low terrain.
-
But to do this, Flight 1008
-
would have to first fly
over the beacon,
-
then turn right onto heading of 330,
-
fly outbound for one minute,
perform a course reversal,
-
and then proceed inbound
-
to Foxtrot Papa again
on the requested inbound course.
-
Quite a complex maneuver to fly
-
when you're
almost over the beacon.
-
Now, the pilots might
have eventually figured this out
-
if not for a tiny slip of
the tongue by the controller,
-
which changed this
entire course of events.
-
Remember that the
controller wanted Flight 1008
-
to fly counter-clockwise
-
around the holding pattern,
making left turns?
-
Well, this meant that what
he wanted to say
-
was turns to the left,
-
but what he actually
ended up saying
-
was, "Turn to the left," which
has a very different meaning.
-
Turn to the left
is normally interpreted
-
as a command to turn left, right away,
-
which was not at
all what the controller
-
wanted them to do here.
-
What he attempted to say
-
was only a description
of the holding pattern,
-
which is technically just informational,
-
not an order, and that also made sense,
-
given that he didn't
have any radar available.
-
Spanish investigators later used this
-
to argue that the controller
didn't bear any responsibility
-
for issuing a non-standard clearance,
-
but given how his call actually sounded
-
to the pilots,
that's not completely fair.
-
Anyway, when the flight
crew received this message
-
from the controller,
they simply replied,
-
"Roger," with no further readback
-
or request for confirmation.
-
They might have thought at first
-
that they understood what he said,
-
but within 10 seconds,
the captain realized
-
that he wasn't able to picture
-
what the controller was asking from him,
-
so he said, that's an odd
sort of one, the runway.
-
He then interrupted himself
-
with a confirmation that
they had 1,000 feet
-
to go to their
cleared altitude of 6,000 feet,
-
and after that, the first officer said,
-
"No, I'm not, er...
Supposedit's all right?"
-
The captain continued with,
"I'll just turn straight round
-
to the left on the 150
when I go overhead then,"
-
to which the first
officer seemed to agree.
-
Now this shows that
the captain clearly believed
-
that he had been told
to turn left on to heading 150
-
after crossing Foxtrot Papa,
-
which again was not at
all what the controller had intended.
-
A command to turn to the left
-
was completely incompatible
with an instruction
-
to fly a holding
pattern inbound on 150 degrees
-
to Foxtrot Papa since,
like what I said earlier,
-
that would require a right turn
followed by a course reversal.
-
So in the captain's mind,
-
the instructions didn't make sense,
-
but he had been able
to pick out two elements
-
in the message which seemed clear to him,
-
150 and turn to the left.
-
So with Foxtrot Papa now coming up
-
in less than one minute,
-
he didn't have a lot
of time to figure it out.
-
In a stressful situation,
-
without fully comprehending
what the controller had said,
-
he accepted that the best thing to do
-
was just to execute
the part of the clearance
-
that he understood,
-
and then try to
figure out the rest later.
-
In hindsight, it's easy to say
-
that he shouldn't have acted
-
on an incomplete understanding
of those instructions,
-
but in that moment,
with the sudden time pressure
-
and the added workload
of the sudden holding clearance,
-
it would have been a lot harder
-
to think with that kind of clarity.
-
And it is also worth remembering
-
that this all happened
in a 727 cockpit,
-
with no fancy navigation
displays, only dials.
-
Besides, this CVR transcript suggests
-
that both the first officer
and the flight engineer
-
were looking at the charts
when this all happened,
-
likely searching for
that standard holding
-
in order to be able to verify it.
-
And the first officer had said,
"I suppose it's all right,"
-
which might have reinforced
the captain's belief
-
that he had understood
the clearance correctly.
-
Anyway, seconds later,
having made his decision
-
on how to fly, the captain focused
-
his attention on the rapid approach
-
of the Foxtrot Papa NDB.
-
He said, "The only thing is,
we're just about to miss it.
-
(chuckles) It's too close."
-
At this point, the captain
and the first officer also agreed
-
to tune both automatic
direction finders
-
to the frequency of the Foxtrot Papa,
-
so that they could track it more easily
-
during the holding pattern.
-
And finally, at time 13:19:46,
-
they passed abeam Foxtrot Papa,
-
slightly to the southeast,
and the captain called it out.
-
This prompted the
first officer to report
-
the waypoint passage to the controller,
-
and he also confirmed that they
were now taking up the hold.
-
But in reality, they actually
kept flying straight ahead
-
for another about 20 seconds,
-
covering around two nautical miles
-
before beginning the left turn.
-
Now, the reason for
this delay isn't really known,
-
but it might have been
because the pilots
-
were still trying to wrap their heads
-
around the maneuver that they
now had ahead of them.
-
In fact, a few seconds
before they began that left turn,
-
the first officer said,
"Bloody strange hold, isn't it?"
-
Which indicates that he
was still mentally focused
-
on the confusing instructions.
-
In response to that, the captain said,
-
"Yeah, it doesn't...
-
Isn't parallel with
the runway or anything."
-
Now, I just want to
stop here and drive home
-
what is probably one of
-
the most important points
of this whole video.
-
If something seems strange
with a clearance and you get
-
that pit in the stomach feeling
-
that something just isn't right,
-
always speak up and
ask for further clarification.
-
This goes for all walks
of life and all industries,
-
but especially if
you're flying an aircraft.
-
It's always better
to ask one time too many
-
than one time too few,
-
and I want every one of
you out there to remember that.
-
This, by the way, is also exactly
the kind of discussions
-
that I'm having regularly
on my Zoom hangouts
-
with my Patreon crew,
-
and I hope to see
you there as well next time.
-
Just go to patreon.com/join/mentourpilot
-
if you think that sounds interesting.
-
Anyway, at this point, what
the flight crew didn't yet know
-
was that by overshooting Foxtrot Papa
-
and then turning left
onto a heading a 150 degrees,
-
they were now on a track to
overfly the northern shoulder
-
of La Esperanza, a sub-peak
-
along the island's central volcanic ridge
-
that stretched
north from El Teide.
-
The terrain directly beneath
their projected flight path
-
actually didn't exceed 5,000 feet,
-
but it did lie within the sector,
-
where the minimum safe
altitude was 14,500 feet.
-
So strictly speaking,
-
since they weren't
flying a published procedure,
-
maneuvering at only 6,000 feet
-
would have been
prohibited in this area.
-
The final report would
later place some blame
-
on the flight crew
for flying into this area
-
without being aware
of the applicable MSA,
-
but it seems likely
that at this point,
-
they were still thinking that they
-
were flying an official procedure,
-
even though they couldn't
find it on their charts.
-
At the same time
as Flight 1008 completed
-
their left turn onto a heading of 150
-
and started flying
towards the southeast,
-
the approach controller called up
-
the Iberia Airlines flight ahead of them
-
and asked them to verify
when they had left 5,000 feet.
-
Only seconds later, the
pilot of that aircraft replied
-
that 5,000 feet was now free
-
and that they were in the middle
-
of a procedure turn
to intercept the ILS.
-
As these calls in
Spanish were happening,
-
the first officer on Flight Engineer
-
on board Flight 1008 continued
to compare ATC's instructions
-
with what was printed on their chart,
-
saying things like,
"It's that way, isn't it?"
-
"That's a tree, isn't it?"
-
And, "Yes, well, the hold is
going to be here, isn't it?"
-
It's likely that they
were now very skeptical
-
about the maneuver
that they were flying,
-
but we can never be 100% sure
-
since that wasn't formally verbalized.
-
Anyway, as these
discussions were taking place,
-
the controller now called them up
-
and cleared them to
descend down to 5,000 feet
-
since the Iberia flight
had now left that altitude.
-
And in response, the
flight engineer again reduced
-
the thrust and the
captain initiated the descent.
-
But as they were doing this,
the captain suddenly said,
-
"Hey, did he say it was 1-5-0 inbound?"
-
likely realizing that
his mental picture
-
of where the controller was sending
-
them didn't actually make any sense.
-
The first officer
had probably suspected
-
that from the very start
because he now replied,
-
"Inbound, yeah."
-
And in response to that,
the captain said,
-
"That's... I don't like that."
-
The first officer continued by saying,
-
"They want to keep
going more around, don't they?"
-
It's not completely clear
what he meant by that,
-
but it is possible that
the first officer believed
-
that they were supposed
to keep turning left,
-
making a three quarters turn onto
-
the outbound leg
of the holding pattern,
-
after which they would come back
-
to Foxtrot Papa on
the inbound heading of 150.
-
If that was the case,
it would mean that
-
even the first
officer had indeed interpreted
-
the call from the controller
as an instruction to turn left.
-
And that would also explain why he
-
hadn't spoken up when the turn started.
-
When I read this part of the report,
-
I could really feel that
cold feeling in my stomach.
-
You know, that feeling that you get
-
when you realize
that something is really wrong,
-
but you still can't
figure out what or how.
-
But we don't know if the pilots
-
had yet realized just how dangerous
-
their current flight path was.
-
But the captain's statement of,
-
"I don't like that," definitely
showed some real concern.
-
Again, make sure you
always know what clearance
-
you have been given,
and if in doubt, ask.
-
Anyway, before the pilots could
spend much more time trying
-
to work out what was wrong,
-
the ground proximity warning system
-
suddenly activated at time 13:20:50.
-
The Boeing 727 was equipped
-
with a first generation GPWS,
-
which was state of the art at the time,
-
but also much less capable
-
than the enhanced ground
proximity warning systems
-
that we have on board today's aircraft.
-
Modern EGPWSs compares the position
-
and projected path of the airplane
-
to a digital terrain database.
-
But the original GPSs could only look
-
at the terrain directly
beneath the aircraft
-
using its radio altimeter.
-
If the closure rate with
the terrain was too high,
-
it would an issue sink rate
or pull up warnings.
-
But if the terrain ahead
of the aircraft was rising steeply,
-
the system wouldn't know that,
-
so these warnings could
still come too late.
-
In this case, the airplane
-
was now passing over
the northern shoulder
-
of the central volcanic
ridge while in descent,
-
and that resulted in a
rate of terrain closure
-
greater than 6,000 feet per minute,
-
triggering the warning envelope.
-
But the maximum height
of the ridge ahead of them
-
was actually less than
their current altitude.
-
So in their present trajectory,
-
they were not in any
danger of striking the terrain.
-
But, of course, the
pilots who had now lost
-
their position situational awareness
-
and were still flying
inside of the clouds
-
had no way of knowing this.
-
So in response to the GPWS warning,
-
the captain immediately announced,
-
"Okay, overshoot," which is an
old British term for go around.
-
As the flight engineer advanced
-
the thrust levers to
the takeoff go around thrust,
-
the captain also halted their left turn
-
and added, "He's taking us
around to the high ground,"
-
and after stating that,
he continued rolling right
-
onto a steeper and
steeper right-hand turn.
-
But what he didn't do was
-
to raise the nose in
order to initiate the climb.
-
And why was that then?
-
Well, during GPWS response training,
-
we pilots today are required
-
to practice a terrain escape
maneuver in the simulator,
-
which includes disconnecting
the automatic setting,
-
full thrust pitching up to 20 degrees,
-
making sure the speed
brake lever is down,
-
making proper
call outs and so on.
-
This maneuver is drilled
into everyone flying today
-
in order to make sure that the response
-
to a hard GPWS warning
-
is immediately executed from
memory and without questions.
-
As it turns out, the captain
and the flight engineer
-
had also undergone some type
-
of GPWS training back in 1978,
-
and Dan-Air did have a
procedure for GPWS response,
-
but back in those days
GPWS was a very new technology
-
and there is a possibility
-
that training had
been only theoretical.
-
So we don't know exactly what was going
-
through the captain's head,
but based on his statement
-
that, "He's taking us
around to the high ground,"
-
he probably believed
that the controller's instruction
-
to turn left was faulty
-
and that the controller had told him
-
to turn towards an unsafe direction.
-
Believing that the
GPWS warning occurred
-
because they were turning
left towards high terrain,
-
the captain may have reasoned
-
that the best way
to escape the situation
-
was to turn to the right instead.
-
So without having
practiced the maneuver
-
in the simulator, the
captain's immediate reaction
-
was to turn rather than to climb,
-
which sadly would seal their fate.
-
Because as the right turn now continued,
-
the aircraft passed over
-
the top of the ridge
and then over a valley,
-
causing the radio altitude to increase,
-
which silenced the GPWS warning,
-
10 seconds after it had started.
-
The captain commented,
"Watch my eepers,"
-
referring to the engine
pressure ratio or EPR,
-
essentially ensuring
that the flight engineer
-
maintained TO/GA thrust and
didn't over-boost the engines.
-
But it also now seems like
-
the first officer wasn't convinced
-
that they were now taking
the right course of action.
-
So he called out,
-
"I suggest a heading of 1-2-2 actually
-
and take us through the overshoot."
-
A heading of 1-2-2 degrees
was the heading prescribed
-
by the official Runway 12
missed approach procedure,
-
which would take them
east over the ocean,
-
so this was a pretty sensible suggestion.
-
But 1-2-2 degrees was also
-
to the left of their current heading,
-
which contradicted
the captain's assumption
-
that their left turn was
what had caused the GPWS warning.
-
As a result, he just continued
turning right past due south
-
and then all the way
around to the southwest,
-
directly towards the 5,700 foot
high summit of La Esperanza.
-
Tragically, they might
still have cleared the summit
-
if they had just maintained altitude
-
or climbed following
the terrain escape maneuver.
-
But due to the high bank angle
they were now using,
-
the plane actually lost
lift during the maneuver,
-
causing a slight descent instead.
-
Still flying over the valley,
the flight engineer expressed
-
his nervousness by commenting,
"Let's get out of here."
-
But the captain simply repeated,
-
"He's taking us around
to the high ground."
-
Moments later, without any
new GPWS warnings,
-
and believing that he
had corrected the situation,
-
the captain
called up air traffic control
-
and reported, "Dan-Air 1008,
-
we've had a ground proximity warning."
-
This was then followed
-
by the flight engineer calling
out twice that their bank angle
-
was now above the recommended
maximum of 30 degrees.
-
And his words were
the last ones captured
-
on the cockpit voice recorder.
-
With the mountains shrouded in
clouds, the pilots never saw
-
the danger coming towards them,
-
and the GPWS never had time
-
to react to the closure
rate of the steep mountain ahead.
-
So at time 13:21:18 Dan-Air
Flight 1008 crashed
-
into the forested
mountainside of La Esperanza
-
at a speed of 260 knots,
-
just 38 meters below
the top of the ridge.
-
Most of the aircraft
disintegrated immediately,
-
killing everyone on board,
-
and a large portion
of the aft cabin
-
was then thrown another
250 meters forward
-
over the top of the ridge and
then down to the other side.
-
Down at the airport,
the controller now tried repeatedly
-
to contact the aircraft
in order to follow up
-
on their reported GPWS warning,
-
but when he didn't get any reply,
-
he soon activated the accident alarm.
-
The problem was though that
-
with no radar available
at Tenerife North,
-
rescuers had no idea
where the aircraft was located,
-
especially since it had taken a turn
-
that the controller had
not intended them to take.
-
This meant that the
wreckage wasn't discovered
-
until seven hours after the crash,
-
when a couple of
motorists on the road
-
to El Teide National Park
saw some debris on the road
-
and correlated that to the radio report
-
of a missing aircraft.
-
This crash was, and actually
still is, the worst loss of life
-
on board a British airliner ever,
-
so the investigation received
considerable public attention
-
especially when the Spanish
-
and British investigators didn't agree
-
on how to weigh
the causes of the accident.
-
The Spanish investigators wrote
-
that the pilots
were ultimately responsible
-
for being aware of their position
in a non-radar environment,
-
and that it was their obligation
-
to climb to a safe altitude
-
as soon as they became unsure
of where they actually were.
-
They also cited the pilot's
failure to request clarification
-
when they didn't understand
-
the controller's initial transmission
-
as a major cause of the accident,
-
as well as their incorrect
response to the GPWS warning.
-
They pointed out that if
the pilots had done nothing at all
-
when the GPWS activated,
-
they would have passed
safely over the ridge
-
and continued out over the sea.
-
So the Spanish investigators argued
-
that it was the captain's
decision to turn right
-
that took them back
around to the high terrain
-
and ultimately led to the crash.
-
But the British
investigation team believed
-
that the controller's use
of an unpublished holding pattern,
-
one that didn't appear
on the pilot's chart,
-
as well as its verbal slip-up
saying turn instead of turns,
-
played a very important role
-
in the pilots' loss
of situational awareness.
-
They also noted that
if the holding pattern
-
had been designed according
to international standards,
-
the minimum altitude in the hold
would have been 6,000 feet,
-
which would have
incidentally prevented the crash.
-
But regardless of who made
the most serious errors here,
-
the disaster was made possible
-
by the poor infrastructure
at Tenerife North Airport,
-
including the lack of radar
-
and the poorly-designed
approach procedures.
-
It's also important to remember
-
that the technology available in 1980
-
was far less capable than
what we now have available,
-
and it's exactly because
of accidents like this
-
that we today have
these vastly improved systems
-
and that we pilots are
so well trained in using them.
-
This accident led to recommendations
-
to always question any clearances
that weren't 100% clear
-
as well as some
other recommendations as well.
-
But in the long run,
this accident also led
-
to better training
around GPWS maneuvers
-
and therefore, a
significant increase in safety.
-
Our current fantastic
safety record proves
-
that accidents like these
today are largely preventable,
-
but they are only preventable
-
because of stories like this
-
and that's why I keep telling them.
-
Now, please consider
subscribing to the channel
-
if you found this video interesting
-
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you thought in the comments below.
-
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-
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-
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-
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-
Bye bye.