Indonesia Air Asia flight 8501 carrying
156 passengers is cruising high above
the Java sea when the aircraft is
suddenly rolling sharply to the
left it’s not
aonic it’s not
corrected the aircraft has taken on a
life of its own climbing High higher and
higher while the pilots struggle to
regain
control then inexplicably they start to
drop altitude the aircraft is plummeting
from the sky speeding toward the Java
sea below it seems the pilots cannot do
anything to save their
aircraft this story is about human error
training deficiencies and
miscommunication this is the story of
Indonesia Air Asia flight 8501
[Music]

Three Days Earlier

on Christmas day December 25
2014 a passenger flight was set to
depart from suaya their destination was
quala lumo the capital of
Malaysia the aircraft for this flight
was an Airbus
A320 it was 6 years old and had
accumulated approximately 23,000 flight
hours during push back and after both
engines had started an unexpected
message was displayed on the
ecam the captain returned the aircraft
to the parking Bay and reported the
issue to maintenance
an engineer came to the cockpit to check
and help the pilots diagnose the problem
after Consulting the troubleshooting
manual the engineer reset the circuit
breakers for flight augmentation
computers 1 and two and conducted a
built-in test which resolved the
problem the flight augmentation computer
on an Airbus aircraft controls inputs to
the rudder rudder trim and Y damper
which are crucial for the aircraft
stability the captain and the engineer
engaged in a discussion the captain
asked whether he could perform the same
reset action whenever the problem
reappeared the engineer stated that the
pilot May reset whenever instructed on
the
ecam the aircraft was then ready for
departure during push back and after
starting Engine 2 the message reappeared
on the ecam the pilots performed the
ecam action
however the problem still existed the
engineer who had performed the initial
rectification saw that the aircraft did
not move he took over the interphone and
communicated with the pilots the captain
asked the engineer if he could reset the
system by pulling the fac circuit
breakers the engineer confirmed that
they could proceed with this action
however after the co-pilot reset the
circuit
breakers the problem still persisted
leading the engineer to advise the
pilots to return the aircraft to the
gate disembark the passengers and wait
in the terminal building since the
rectification might take a long
time the engineer consulted the
troubleshooting manual which recommended
replacing flight augmentation computer 2
upon realizing the no spare was
available at the suraya maintenance
store the engineer obtained a
replacement from another aircraft
undergoing maintenance after installing
the new fac2 the engineer requested the
pilots to start both engines to verify
functionality following the power
Interruption after both engines started
the problem did not reappear the captain
was satisfied with the rectification and
advised that they were ready to depart
the aircraft craft then flew from suraya
to quala Lumpur and returned without
further
problems the engineer didn’t realize
then that the problem wasn’t with the
flight augmentation computer 2 but with
the rudder travel limiter explicitly
involving the circuit boards these
boards showed soldering cracks that
could disrupt electrical continuity
leading leading to failures in the
rudder travel limiter unit or
rtlu these cracks likely resulted from
thermal cycling associated with changes
between powered and non-powered
conditions and transitions between
ground and flight States this loss of
electrical continuity was the actual
cause of the rtlu failure despite the
engineers efforts and the replacement of
flight augmentation computer 2 the
underlying issue with the rudder travel
limiter went unresolve olved setting the
stage for potential catastrophic
[Music]

Background Information

consequences on December 28th 156
passengers boarded Indonesia Air Asia
flight
8501 at Wanda International Airport in
suraya Indonesia
the same Airbus A320 on which the flight
augmentation computer 2 had been
replaced 3 days prior was piloted by the
same Captain though accompanied by a
different first officer this time the
captain was 53-year-old iryanto an
Indonesian National he began his
Aviation career in the Indonesian Air
Force at a young age and spent a decade
piloting F5 and F-16 fighter jets
following his military service and early
retirement he transitioned to commercial
Aviation he had over 20,000 flying
hours alongside him was 46-year-old
first officer Remy Emanuel plel he had
more than 2,000 flying hours in this
flight the first officer acted as the
pilot flying and the captain acted as
the pilot
monitoring before departure the pilots
reviewed the weather and their route
flight 8501 was scheduled to travel from
suraya Indonesia to Singapore Changi
Airport crossing the Java sea along the
Route this journey typically takes about
2 and 1 half
hours they noted thunderstorms and areas
of towering cumul nimbus clouds along
the Route with Cloud tops ranging from
24,000 ft to 44,000 ft prevailing
Westerly winds were blowing at 15 to 20
knots and temperatures at cruising
altitude ranged from – 56 de to –
[Music]

Pushback

62° flight 8501 was ready for
takeoff after receiving clearance the
aircraft was pushed back from the gate
and made its way to the

Take Off

[Music]
runway a few moments later at 535 a.m.
local time the aircraft took off
beginning its

Cruising Altitude

climb just 14 minutes after takeoff the
aircraft had climbed to its cruising
altitude of 32,000 ft known as flight
level
320 ready for the journey across the
Java
sea due to the Towering clouds in the
area and the outside temperature of –
62° c the first officer activated the
aircraft’s anti- I system to prevent the
formation of ice on the aircraft’s wings
and engines which can affect performance
and

Anti Ice

safety concurrently the flight attendant
announced to the passengers to return to
their seats and fasten their seat belts
due to the weather conditions and the
possibility of encountering turbulance
during the
flight barely 30 minutes into the flight
and cruising at an altitude of 32,000 ft
the master caution light was triggered

First Signs of Trouble?

accompanied by an advisory message on
the
ecam the captain recognized this alert
because he had encountered it multiple
times 3 days prior however this time it
didn’t occur during taxiing instead it
occurred during the flight flying high
above the Java sea the first officer
read and performed the ecam action to
set both flight augmentation computers
Push by buttons to off and then to
on both Rudder travel limiter units
return to function

Rudder Travel Limiter Animation

normally a Rudder travel limiter is a
critical safety device in an aircraft
that restricts the maximum movement of
the rudder the rudder is a primary
control surface located at the tail of
an aircraft and it helps to control the
yore
at lower speeds the rudder travel
limiter allows for greater Rudder
movement to facilitate sharp
turns at higher speeds it restricts
Rudder deflection that could compromise
the aircraft’s structural integrity and
stability with the fault resolved the

Bad Weather Ahead

crews attention shifted from the ecam to
the onboard weather radar they noticed a
large storm looming in the distance the
captain requested a deviation of 15 Mi
to the left of the track to avoid the
weather which was approved the aircraft
then altered its course to a heading of
310° thunderstorms pose the most
significant risk to aircraft among all
weather conditions they often contain
hail heavy rainfall lightning ice strong
winds and super cooled water droplets
potentially damaging an aircraft under
extreme circumstances
pilots make every effort to steer clear
of thunderstorms whenever feasible to
ensure the safety of the flight shortly
after a second failure occurred on both
Rudder travel limiter units signaling
with a chime and the illumination of the
master caution light once again the same
message appeared on the ecam the pilots
promptly repeated the ecam action and
both Rudder travel limiter units resumed
normal function
the pilots contacted Air Traffic Control
in Jakarta informing them that the

Contacting Jakarta Air Traffic Control

flight had turned left off its planned
route to avoid the bad weather
conditions this update was acknowledged
and tracked on the radar screen by the
controller the controller then
instructed the pilots to report once
they had cleared the weather shortly
afterward the pilots requested to climb
to 38,000 ft if possible to which they
were advised to stand by regrettably
this marked the final radi
communication once again a single chime
sounded accompanied by an ecam message
this marked the third failure of both
Rudder travel limiter units during this
flight following the ecam procedures the
pilots took action and the system
returned to normal
[Music]
function but 2 minutes later the master
caution light illuminated again and the
same message appeared on the
ecam this was now the fourth occurrence
and the captain pondered what else he
could do instead of repeating the same
action for the fourth time which seemed
to yield no results then something
struck his
memory the captain had seen the engineer
reset the fac circuit breakers on the

Captain Flashback

ground to eliminate this problem he even
asked the engineer whether he could
perform the same reset action whenever
the problem
reappeared but this time they weren’t on
the ground where a maintenance
technician could help them this time
they were flying high above the Java sea
in the Airbus A320 quick reference
handbook the chapter titled computer
reset states that in Flight as a general
rule the crew must restrict computer
resets to those listed in the table
before taking action on other computers
the flight crew must consider and fully
understand the
consequences having experienced
witnessing and Performing flight
augmentation computer circuit breaker
resets the captain might assume he fully
understands the
consequences notably the fac circuit
breakers were not included in the table
of the quick reference handbook and the
consequences of resetting them in flight
are not described in Airbus
documents the crew should have
deliberated the consequences of
resetting the circuit breakers to assess

RESET FAC 1 + 2

the risks and devise an action plan as
outlined in crew coordination during
emergencies or abnormalities
procedures however the captain deviates
from this protocol and merely 54 seconds
after the fourth Master caution warning
appears he resets the circuit breakers
it’s a decision he will soon
regret immediately after resetting the
circuit breakers the fifth Master
caution warning is sounded in the
cockpit accompanied by multiple
notifications on the
ecam resetting the circuit breakers
caused an electrical Interruption
leading to the disengagement of the
autopilot and auto thrust systems
and the control logic transitioned from
normal law to alternate law this means
the aircraft had lost several
computerized protections designed to
maintain it within safe operational
limits in addition the rudder deflected
2° to the left causing the aircraft to
roll up to a 54° angle of bank
[Music]
this roll rate was twice as fast as the
standard roll rate operation due to the
multiple ecam messages appearing after
the autopilot disconnect the pilots did
not notice this roll movement as they
were distracted it wasn’t until 9
seconds later that the first officer
took control of the right side
[Music]
stick the initial response of the first
officer was to pull the stick backward
and then to the right reaching maximum
deflection this action reduced the
aircraft’s roll angle to 9°
left the rapid rolling movement to the
right might have induced an excessive
sensation of rolling to the
right subsequently possibly disoriented
from the rapid right turn the first
officer let the aircraft Bank to the
left
again it’s not
responding it’s it’s not
[Music]
correcting the input on the right side
stick was mostly pitch up and the
aircraft climbed up with a climb rate of
up to 11,000 ft per minute the aircraft
continued banking left and as it climbed
it started to lose
speed a few minutes ago everything
seemed fine but flight 8501 had now
turned into a true nightmare the captain
observed the situ sitation and urgently
instructed the first officer to pull
down
repeatedly pull down pull
down his choice of words was confusing
the Sid stick can be either pushed down
or pulled up the command pull down is
contradictory and could be interpreted
differently in response to this unclear
command the first officer continued to
pull up triggering the stall warning as
the aircraft continued it rapid
[Music]
climb a stall occurs when the aircraft’s

Stall Animation

wings can no longer generate enough lift
to sustain its flight lift is the force
generated by the air flow over the wings
when the air flow over the wings becomes
disrupted typically due to an
excessively high angle of attack the
wings lose their ability to generate
lift effectively this loss of lift
results in a sudden decrease in the
aircraft’s ability to stay
airborne the captain continued yelling
to pull down followed by pitch-up
commands from the first officer the

DUAL Input

captain felt the need to take action and
reached for his side stick while the
first officer also controlled his when
One Pilot operates the Sid stick it
sends control signals to the computers
based on the priority
logic however when both Pilots move both
side sticks simultaneously in the same
or opposite direction and neither takes
priority the system combines the signals
algebraically the two green Sid stick
priority lights are illuminated during
this time followed by a dual input voice
message activation dual input however
this was not audible because the stall
warning had already been
[Music]
activated the sum of both Sid stick
inputs command landed nose up Pitch as
the first officer pulled almost fully
back while the captain pushed the nose
down slightly the pitch up input
resulted in the angle of attack reaching
a maximum of 48° which was beyond the
flight director’s envelope and the
flight directors disappeared the
aircraft reached the highest altitude of

Highest Altitude

38,000 ft and the largest roll angle of
104 de to the left then inexplicably it
started to drop
altitude flight 8501 was plummeting from

Plummeting From the Sky

the sky up to 20,000 ft per minute
speeding toward the Java sea
below the stall warning sounded in the
cockpit but the pilots did not
understand what was happening the
captain commanded the first officer to
select air data to cap 3 this action
would transfer the air data source from
Air data inertial reference unit 1 to
three the captain might have assumed
that an air data error had triggered the
rapidly fluctuating air speed indication
but nothing could be further from the
truth the incredibly low speed he was
seeing was indeed the actual
speed they had only a minute left to
prevent a disaster it seemed the pilots
couldn’t do anything to save their
aircraft the pilots tried to do what
they could but the first officer kept
pulling his side stink backward
this action prevented the aircraft from
recovering from the stall and the
aircraft continued to fall the bad
weather only compounded the situation
the pilots lacked a visible Horizon as a
reference point making it difficult to
discern their position in the
sky P down P down both Pilots persisted
in their efforts to save the aircraft
until it was too late at 20 minutes P 6
that morning the aircraft crashed into
the Java sea disintegrating upon impact
and sinking to the seabed all 162 people
on board perished
[Music]
instantly shortly after the aircraft was

Aftermath

confirmed missing a search operation was
launched the wreckage was quickly
discovered among the recovered debris
were sections of the impen including
parts of the rear fuselage the vertical
stabilizer and the rudder another
retrieved section was the fuselage
containing the center fuselage wings and
both main landing gears additionally
several smaller parts such as passenger
seats Escape slides and interior panels
were found floating and were recovered
approximately 30 nautical miles
Southeast of the main wreckage site the
official SE for bodies ended in March
2015 after 116 bodies had been recovered
46 bodies remained unaccounted
for the investigation concluded that

Investigation

several factors contributed to this
accident the cracking of a solder joint
in both channels A and B of the
electronic modules of the rudder travel
limiter units resulted in a loss of
electrical continuity this this resulted
in unresolved repetitive ecam messages
occurring at shorter intervals following
the fourth fault the captain reset the
fac circuit breakers causing an
electrical Interruption to the flight
augmentation computers the interruption
led to the autopilot disengaging and the
flight control logic transitioning from
normal law to alternate law consequently
the rudder deflected 2° to the left
causing the aircraft to roll up to a 54
de ree angle of bank subsequent actions
by the flight crew combined with the
aircraft being an alternate law resulted
in the inability to control the aircraft
within the standard flight envelope
ultimately this led to the aircraft
entering a prolonged stall condition
that exceeded the capability of the
flight crew to
recover an angle of attack of 40° was
beyond the competency of any airline
pilot training as they had never been
trained for or experienced such a
scenario