Crash Flight QZ8501 Under Individual or Collective Maintenance Responsibility 
Autor: George Rocha | Publicado: 2015-12-29T23:20:00-02:00









 

  
On 28 December 2014, an Airbus
  A320-216 aircraft registered as PK-AXC was being operated by PT. Indonesia
  Air Asia on a scheduled flight from Juanda International Airport Surabaya,
  Indonesia to Changi International Airport, Singapore. The aircraft departed
  at 0535 LT (2235 UTC, 27 December 2014) and was cruising at 32,000 feet
  (FL320) via ATS (Air Traffic Services) route Mike 635 (M635) with total
  occupants of 162 persons. The Pilot in Command (PIC) acted as Pilot
  Monitoring (PM) and the Second in Command (SIC) acted as Pilot Flying (PF). 



  
Em
  28 de dezembro de 2014, uma aeronave Airbus A320-216 registrada como PK-AXC
  estava sendo operada pela empresa privada Indonesia Air Asia num voo regular a
  partir do Aeroporto Internacional de Juanda, Surubaya, Indonésia para o
  aeroporto Internacional de Changi, Singapore. A aeronave partiu às 05:35 Local
  Time (22:35 UTC, em 27 DEZ 2014) e estava cruzando a 32.000 pés (Flight Level
  320) na rota ATS (Serviços de Tráfego Aéreo) Mike 635 (M635) com o total de
  162 pessoas a bordo. O Piloto em Comando (PIC) atuava como Pilot Monitoring
  (PM) e o Segundo Piloto em Comando (SIC) atuava como Pilot Flying (PF).

 

  
The totals of 162 persons were on
  board this flight consisted of two pilots, four flight attendants and 156
  passengers including one company engineer.

  
O
  total de 162 pessoas que estavam a bordo deste voo consistia de dois pilotos e
  quatro comissários de bordo e 156 passageiros, incluindo um engenheiro de
  empresa.

 

  
The
  sequence of events was retrieved from both of Flight Data Recorder (FDR) and
  Cockpit Voice Recorder (CVR).

  
A
  sequência de eventos foi recuperada de ambos os gravadores, Flight Data
  Recorder (FDR) e&nbsp; Cockpit Voice &nbsp;Recorder (CVR).

 













 

  
The way pilots
  responded to a technical malfunction resulted in the crash of Air Asia Flight
  QZ8501, investigators said Tuesday [DEC 29, 2015]. The ill-fated plane was en
  route to Singapore from the Indonesian city of Surabaya on December 28 last
  year when it crashed into the Java Sea, killing all 162 people on board.



  
A maneira que os pilotos responderam a
  um mau funcionamento técnico resultou no acidente da Air Asia Voo QZ8501, os
  investigadores disseram na Terça-feira [29 DEZ 2015]. O malfadado avião estava
  em rota para Singapura a partir da cidade Indonésia de Surabaia, em 28 de Dezembro
  no ano passado quando ele caiu no Mar de Java, matando todas as 162 pessoas a
  bordo.

 

  
The plane’s flight
  control computer had a cracked solder joint that kept malfunctioning.
  Aircraft maintenance records found it had malfunctioned 23 times in the year
  before the crash, and the interval of those became shorter in the three
  months prior to the crash.

“Subsequent flight
  crew action resulted in inability to control the aircraft… causing the
  aircraft to depart from the normal flight envelope and enter a prolonged
  stall condition that was beyond the capability of the flight crew to
  recover,” Indonesia’s National Transport Safety Committee said in a report.



  
O computador de controle de voo do
  avião que o mantinha funcionando teve uma junta de solda rachada. Nos registros
  da manutenção da aeronave descobriu-se que ela [aeronave] tinha sofrido mau
  funcionamento 23 vezes no ano antes do acidente, e o intervalo desses maus funcionamentos
  tornou-se mais curto nos três meses antes do acidente. "A ação subsequente
  da &nbsp;tripulação de voo resultou na
  incapacidade de controlar a aeronave... causando&nbsp;à aeronave afastar-se do
  envelope de voo normal e entrar em uma condição prolongada de estol que foi
  além da capacidade da tripulação de voo para recuperar [o voo normal]," O
  Comitê Nacional de Segurança de Transporte da Indonésia disse em um
  relatório.

 

  


  


 

  
The investigation
  concluded that contributing factors to this accident were: 

·&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;

  
A investigação concluiu que os fatores
  contribuintes para este acidente foram:

 

  
·&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
  The cracking of a solder joint of both channel A and B
  resulted in loss of electrical continuity and led to RTLU failure.

  
·&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
  A quebra de uma junta de solda de ambos os
  canais, A e B, resultado da perda de continuidade elétrica e que conduziu à
  falha da RTLU. [Rudder Travel Limiter Unit = Unidade Limitadora do Percurso do Leme].

 

  
·&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
  The existing maintenance data analysis led to unresolved
  repetitive faults occurring with shorter intervals. The same fault occurred 4
  times during the flight. 



  
·&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
  A análise de dados de manutenção
  existentes conduziu para as falhas repetitivas não solucionadas ocorrendo em
  intervalos mais curtos. A mesma falha ocorreu 4 vezes durante o voo.

 

  
·&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
  The flight crew action to the first 3 faults in accordance with
  the ECAM messages. Following the fourth fault, the FDR recorded different
  signatures that were similar to the FAC CB‟s being reset resulting in
  electrical interruption to the FAC‟s. 

  
·&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
  A ação da tripulação de voo para as 3
  primeiras falhas em conformidade com as mensagens do ECAM [Electronic
  Centralized Aircraft Monitoring]. Após a quarta falha, o FDR [Flight Data
  Recorder] gravou sinais diferentes que eram semelhantes&nbsp;aos [sinais]&nbsp;do &nbsp;FAC CB‟s [Flight Augmentation Computer circuit
  brakes = fusíveis elétricos] reposicionados resultando em interrupção
  elétrica para os FAC‟s.

 

  
·&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
  The electrical interruption to the FAC caused the autopilot to
  disengage and the flight control logic to change from Normal Law to Alternate
  Law, the rudder deflecting 2° to the left resulting the aircraft rolling up
  to 54° angle of bank.

  
·&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
  A interrupção elétrica do FAC causou ao
  piloto automático desengajar e&nbsp;à lógica de controle de voo para mudar de
  Normal Law para Alternate Law,&nbsp;[e&nbsp; ainda causou] a deflexão do leme 2° para a esquerda,
  resultando a aeronave rolar até&nbsp;o ângulo de 54° de inclinação lateral.

 

  
·&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
  Subsequent flight crew action leading to inability to control the
  aircraft in the Alternate Law resulted in the aircraft departing from the
  normal flight envelope and entering prolonged stall condition that was beyond
  the capability of the flight crew to recover.



  
·&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
  A ação subsequente da tripulação de voo
  conduziu à incapacidade para controlar a aeronave [no modo] Alternate Law o
  que resultou na aeronave saindo do envelope de voo Normal e entrando na
  condição &nbsp;prolongada de stall que foi além da capacidade da
  tripulação de voo para recuperar.

 









RUDDER and YAW DAMPER



RUDDER and LOADS





CONSIDERATIONS





• The rudder deflection is the sum of:


– the order from the pedal input


– the order from the “Yaw Damper” function.


• This deflection is limited by the RTLU (Rudder Travel
Limit Unit) for structural considerations.


• The Rudder trim merely moves the pedals.





Role of
the “Yaw Damper” on FBW aircraft: A320





• The “Yaw Damper functions are achieved by the ELAC when
handflying the Aircraft:


– Dutch Roll Damping and Turn Coordination


– Lateral Control Law objectives (eg: ß = f(rudder
pedal), engine out …)





• The FAC transmits the ELAC rudder deflection orders to
the Y/D actuator and achieves the Rudder Travel Limit function.





Operational
Consequences


• On most commercial A/C, the rudder


MUST NOT BE USED:


– to induce Roll,


– to counter Roll induced by any type of turbulence,


– for turn coordination (exceptionally in Direct Law,
with a double hydraulic failure where YD is lost).









• On most commercial A/C, the rudder


IS ACTUALLY USED ONLY:


– during T/O and LANDING Roll,


– in case of Engine Out, as a yaw corrective action,


– during the last phase of a flare with crosswind for
decrab purpose.


&nbsp;&nbsp; 


• On most commercial A/C:


– there is no need to act on the rudder abruptly,


– in case of failure leading to a loss of TLU, the rudder
is to be used with &nbsp;&nbsp;care, as per ECAM,


– there is no roll control restriction with an engine failed.








Aircraft
Airbus 320-216 Flight Controls Laws



 

  
AIRBUS FLIGHT CONTROL LAWS

 

  
High
  AOA Protection

  
Load
  Factor Limitation

  
Pitch
  Attitude Protection

 

  
NORMAL
  LAW

 

  
High
  Speed Protection

  
Flight
  Augmentation (Yaw)

  
Bank
  Angle Protection

 







 

  
Low
  Speed Stability

  
Load
  Factor Limitation

  


 

  
ALTERNATE
  LAW

 

  
High
  Speed Stability

  
Yaw
  Damping Only

  


 







 

  


  
Load
  Factor Limitation

  


 

  
ABNORMAL
  ALTERNATE LAW w/o Speed Stability

 

  


  
Yaw
  Damping Only

  


 







 

  


  


  


 

  
DIRECT
  LAW

 

  


  


  


 











 

  
  
  

FLIGHT CONTROL LAWS SUMMARY

 

  
NORMAL
  LAW

 

  
Normal operating configuration of the
  system. Failure of any single computer does not affect normal law.
  Covers 3-axis control, flight envelope protection, and load alleviation. Has 3
  modes according to phase of flight.

 

  
Ground
  Mode

  
Active
       when aircraft is on the ground.
Direct
       proportional relationship between the sidestick deflection and
       deflection of the flight controls.
Is active
       until shortly after liftoff.
After
       touchdown, ground mode is reactivated and resets the stabilizer trim to
       zero.


 

  
Flight
  Mode

  
Becomes
       active shortly after takeoff and remains active until shortly before
       touchdown.
Sidestick
       deflection and load factor imposed on the aircraft are directly
       proportional, regardless of airspeed.
With
       sidestick neutral and wings level, system maintains a 1 g load in pitch.
No
       requirement to change pitch trim for changes in airspeed, configuration,
       or bank up to 33 degrees.
At full
       aft/fwd sidestick deflection system maintains maximum load factor for
       flap position.
Sidestick
       roll input commands a roll rate request.
Roll rate is
       independent of airspeed.
A given
       sidestick deflection always results in the same roll rate response.
Turn
       coordination and yaw damping are computed by the ELACs and transmitted
       to the FACs.
No
       rudder pedal feedback for the yaw damping and turn coordination
       functions.


 

  
Flare
  Mode

  
Transition
       to flare mode occurs at 50' RA during landing.
System memorizes
       pitch attitude at 50' and begins to progressively reduce pitch, forcing
       pilot to flare the aircraft
In
       the event of a go-around, transition to flight mode occurs again at 50'
       RA.


 

  
Protections

  
Load factor Limitation 

Prevents
       pilot from overstressing the aircraft even if full sidestick deflections
       are applied.

Attitude
  Protection

Pitch limited
       to 30 deg up, 15 deg down, and 67 deg of bank.
These limits
       are indicated by green = signs on the PFD.
Bank angles in
       excess of 33 deg require constant sidestick input.
If input is
       released the aircraft returns to and maintains 33 deg of bank.

High
  Angle of Attack Protection (alpha):

When alpha
       exceeds alpha prot, elevator control switches to alpha protection mode
       in which angle of attack is proportional to sidestick deflection.
Alpha max
       will not be exceeded even if the pilot applies full aft deflection

High
  Speed Protection:

Prevents
       exceeding VMO or MMO by introducing a pitch up
       load factor demand.
The pilot can
       NOT override the pitch up command.

Low
  Energy Warning:

Available in
       CONF 2,3, or FULL between 100' and 2,000' RA when TOGA not selected.
Produces
       aural "SPEED SPEED SPEED" when change in flight path alone is
       insufficient to regain a positive flight path (Thrust must be
       increased).


 












UTC (Universal Time Coordinate)
is the primary time standard by which the world regulates clocks and time. It
is, within about 1 second, mean solar time at 0° longitude; it does not observe
daylight saving time. It is one of several closely related successors to
Greenwich Mean Time (GMT). Local time of the point of departure and the
accident site was UTC + 7. &nbsp;







The sequence of events
retrieved from both of Flight Data Recorder (FDR) and Cockpit Voice Recorder
(CVR) were as follows: 




2231 UTC, the aircraft started
to taxi. 




2235 UTC, the aircraft took
off. 




2249 UTC, the flight reached
cruising altitude of 32000 feet (Flight Level 320). 




At 2257 UTC, the PF asked for
anti-ice ON and the flight attendant announced to the passengers to return to
their seat and fasten the seat belt due to weather condition and possibility of
turbulence. 



At 2300 UTC,
the Electronic Centralized Aircraft Monitoring (ECAM) amber advisory AUTO FLT
RUD TRV LIM 1 appeared. The PF asked “ECAM action”. 



At 2301 UTC, FDR recorded
failure on both Rudder Travel Limiter Units and triggered a chime and master
caution light. The ECAM message showed “AUTO FLT RUD TRV LIM SYS” (Auto Flight
Rudder Travel Limiter System). The PIC read and performed the ECAM action of
AUTO FLT RUD TRV LIM SYS to set Flight Augmentation Computer (FAC) 1 and 2
push-buttons on the overhead panel to OFF then to ON one by one. Both Rudder
Travel Limiter Units returned to function normally. 


At 2304 UTC, the PM requested
to the Ujung Pandang Upper West2 controller to deviate 15 miles left of track for
weather avoidance and was approved by the controller. The aircraft then flew on
a heading of 310°. 


At 2306UTC, the SIC conducted
cruise crew briefing including in the case of one engine inoperative or
emergency descent and that Semarang Airport would be the alternate airport. 


At 2309 UTC, the FDR recorded
the second failure on both Rudder Travel Limiter Units and triggered a chime
and master caution light. The pilots repeated the ECAM action and both Rudder
Travel Limiter Units returned to function normally. 


At 2311 UTC, the pilot
contacted the Jakarta Upper Control3 controller and informed that the flight turned to the
left off the M635 to avoid weather. The information was acknowledged and
identified on the radar screen by the Jakarta Radar controller. The Jakarta
Radar controller instructed the pilot to report when clear of the weather. 


At 2312 UTC, the pilot
requested for a higher level to FL 380 when possible and the Jakarta Radar
controller asked the pilot to standby. 


At 2313:41 UTC, the single
chime sounded and the amber ECAM message “AUTO FLT RUD TRV LIM SYS” was
displayed. This was the third failure on both Rudder Travel Limiter Units on
this flight. The pilots performed the ECAM actions and the system returned to
function normally. 


At 2315:36 UTC, the fourth
failure on both Rudder Travel Limiter Units and triggered ECAM message “AUTO
FLT RUD TRV LIM SYS”, chime and master caution light. 


At 2316 UTC, the Jakarta Radar
controller issued a clearance to the pilot to climb to FL 340 but was not
replied by the pilot. The Jakarta Radar controller then called the pilot for
several times but was not replied. 


At 2316:27 UTC, the fifth
Master Caution which was triggered by FAC 1 FAULT followed by FDR signature of
alteration 4of parameters of components controlled by FAC 1 such as RTLU 1,
Windshear Detection 1 and Rudder Travel Limiter Actuator 1. 


At 2316:44 UTC, the sixth
Master Caution triggered by AUTO FLT FAC 1 + 2 FAULT and followed by FDR
signature of alteration of parameters of components controlled by FAC 2 such as
RTLU 2, Windshear Detection 2 and Rudder Travel Limiter Actuator 2. The Auto
Pilot (A/P) and the Auto-thrust (A/THR) disengaged. Flight control law reverted
from Normal Law to Alternate Law. The aircraft started to roll to the left up
to 54° angle of bank. 


Nine seconds after the
autopilot disengaged, the right side-stick activated. The aircraft roll angle
reduced to 9° left and then rolled back to 53° left. The input on the right
side-stick was mostly pitch up and the aircraft climbed up to approximately
38,000 feet with a climb rate of up to 11,000 feet per minute. 


At 2317:18 UTC, the stall
warning activated and at 2317:22 UTC stopped for 1 second then continued until
the end of recording. 


The first left side stick input
was at 2317:03 UTC for 2 seconds and at 2317:15 UTC another input for 2
seconds, then since 2317:29 UTC the input continued until the end of the
recording. 


The right side stick input was
mostly at maximum pitch up until the end of recording. 


The lowest ISIS speed recorded
was 55 knots. The ISIS speed recorded fluctuated at an average of 140 knots
until the end of the recording. 


At 2317:41 UTC the aircraft reached the highest ISIS altitude
of 38,500 feet and the largest roll angle of 104° to the left. The aircraft
then lost altitude with a descent rate of up to 20,000 feet per minute. 








At approximately 29,000 feet the aircraft attitude was wings
level with pitch and roll angles of approximately zero with the airspeed varied
between 100 and 160 knots. The Angle of Attack (AOA)5 was almost constant at approximately 40° up and the stall
warning continued until the end of recording. The aircraft then lost altitude
with an average rate of 12,000 feet per minute until the end of the recording. 


At 2318 UTC, the aircraft
disappeared from the Jakarta Radar controller screen. The aircraft last
position according to the Automatic Dependent Surveillance- Broadcasting
(ADS-B) radar was on coordinate 3°36‟48.36”S - 109°41‟50.47”E and the aircraft
altitude was approximately 24,000 feet. 


The last data recorded by FDR was at 2320:35 UTC with ISIS
airspeed of 132 kts, pitch 20° up, AOA 50° up, roll 8° to left, the rate of
descent 8400 ft/minute and the radio altitude was 118 feet. No emergency
message was transmitted by the crew. 




Characteristic of pitch and
lateral 


Pitch Control 


When the PF performs sidestick
inputs, a constant G-load maneuver is ordered, and the aircraft responds with a
G-Load/Pitch rate. Therefore, the PF‟s order is consistent with the response
that is "naturally" expected from the aircraft: Pitch rate at low
speed; Flight Path Rate or G, at high speed. 


So, if there is no input on the
stick: 


• The aircraft maintains the
flight path, even in case of speed changes 


• In case of configuration
changes or thrust variations, the aircraft compensates for the pitching moment
effects 


• In
turbulence, small deviations occur on the flight path. However, the aircraft
tends to regain a steady condition.


Airbus Pitch
Characteristic









Sidestick Pitch (P) input
Positive (+) value means nose down input 



Sidestick Roll (R) input
Positive (+) value means aircraft rolls to the left 



Rudder Position Positive (+)
means left rudder input (left yaw) 



Elevator Position Positive (+)
means TE down (nose-down) 



Trimmable Stabilizer (THS)
Position Range: -13.5° to +4° Positive: trailing edge (TE) up (nose-down) 



Aileron
Position Positive (+) means trailing edge (TE) down (nose up).









Operational Recommendation: 


From the
moment the aircraft is stable and auto-trimmed, the PF needs to perform minor
corrections on the sidestick, if the aircraft deviates from its intended flight
path. The PF should not force the sidestick, or over control it. If the PF
suspects an over control, they should release the sidestick.


Lateral Control 


When the PF performs a lateral
input on the sidestick, a roll rate is ordered and naturally obtained. 


Therefore, at a bank angle of
less than 33°, with no input on the sidestick, a zero roll rate is ordered, and
the current bank angle is maintained. Consequently, the aircraft is laterally
stable, and no aileron trim is required. 


However, lateral law is also a
mixture of roll and yaw demand with: 


‐ Automatic
turn coordination 


‐ Automatic
yaw damping 


‐ Initial
yaw damper response to a major aircraft asymmetry. 


In addition, if the bank angle
is less than 33°, pitch compensation is provided. If the bank angle is greater
than 33°, spiral stability is reintroduced and pitch compensation is no longer
available. This is because, in normal situations, there is no operational
reason to fly with such high bank angles for a long period of time. 





Airbus
Lateral Characteristic







Operational Recommendation: 


During a normal turn (bank
angle less than 33°), in level flight: 


• The PF moves the sidestick
laterally (the more the sidestick is moved laterally, the greater the resulting
roll rate - e.g. 15°/s at max deflection) 


• It is not necessary to make a
pitch correction 


• It is not necessary to use
the rudder. 


In the case of steep turns
(bank angle greater than 33°), the PF must apply: 


• Lateral pressure on the
sidestick to maintain bank 


• Aft
pressure on the sidestick to maintain level flight.



Rudder Travel Limitation 


This function limits rudder deflection based on speed in order to avoid high structural loads. It is governed by the following law:











If both FACs lose the rudder
travel limitation function, the value of the rudder deflection limit is locked
at the time of the second failure. 


When the
slats are extended, the FACs automatically set the rudder deflection limit at
the low-speed setting (maximum authorized deflection).




The CVR
contained 2 hours and 4 minutes of good quality recording data. The significant
excerpts from the CVR are as follow:




















Airplane Upset: An airplane in
flight unintentionally exceeding the parameters normally experienced in line
operations or training: 


• Pitch attitude greater than
25 degree, nose up. 


• Pitch attitude greater than
10 degree, nose down. 


• Bank angle greater than 45
degree. 


• Within the
above parameters, but flying at airspeeds inappropriate for the conditions. &nbsp;








The summary of the examination
found the electronic cards shows the evidence of cracking of soldering of both
channel A and channel B. Those cracks could generate loss of electrical
continuity and lead to a TLU failure. 


Thermal cycles associated to
powered/not-powered conditions and ground/flight conditions, generate fatigue
phenomenon of the soldering, and may result in soldering cracking. Soldering
cracking could induce a disconnection of components from the circuit. The
disconnections could create a loss of the affected RTLU channel. 


The
electronic module pictures are shown above.