A332, Karachi Pakistan, 2014
From SKYbrary Wiki
|On 4 October 2014, the fracture of a hydraulic hose during an A330-200 pushback at night at Karachi was followed by dense fumes in the form of hydraulic fluid mist filling the aircraft cabin and flight deck. After some delay, during which a delay in isolating the APU air bleed exacerbated the ingress of fumes, the aircraft was towed back onto stand and an emergency evacuation completed. During the return to stand, a PBE unit malfunctioned and caught fire when one of the cabin crew attempted to use it which prevented use of the exit adjacent to it for evacuation.|
|Actual or Potential
|Airworthiness, Fire Smoke and Fumes, Ground Operations, Human Factors|
|Flight Conditions||On Ground - Normal Visibility|
|Domicile||United Arab Emirates|
|Type of Flight||Public Transport (Passenger)|
|Origin||Karachi/Jinnah International Airport|
|Intended Destination||Dubai International Airport|
|Take off Commenced||No|
|Location - Airport|
|Airport||Karachi/Jinnah International Airport|
|Tag(s)||Inadequate Aircraft Operator Procedures,|
Inadequate Airport Procedures
|Tag(s)||Procedural non compliance|
|Tag(s)||Aircraft Push Back|
|Damage or injury||Yes|
On 4 October 2014, an Airbus A330-200 (A6-EAQ) being operated by Emirates Airline on a scheduled passenger flight from Karachi to Dubai as EK609 was pushing back from stand at Karachi in normal night visibility when a hydraulic system fault was annunciated and soon afterwards, dense hydraulic mist entered both the passenger cabin and the flight deck via the aircraft air conditioning system. After a short delay, during which the fumes in the passenger cabin worsened and a Protective Breathing Equipment (PBE) unit caught fire when one of the cabin crew attempted to use it, the aircraft was towed back onto stand where an emergency evacuation of all occupants was completed. Minor injuries were sustained by 7 of the 12 cabin crew and 1 of the 68 passengers. The only damage to the aircraft was in the area where the PBE unit had caught fire.
An Investigation was carried out by the UAE GCAA Accident Investigation Sector. Data from the CVR were successfully downloaded and were useful in assessing crew performance in response to the two separate technical malfunctions which occurred.
It was noted that the 40 year-old Captain had 9,512 hours total flying experience including 3,909 hours on type. He was accompanied by a 41 year-old First Officer with 8,754 total flying hours including 1,657 hours on type.
It was established that after starting the No. 1 engine on stand, the attached GPUs were removed and pushback was commenced. As the pushback neared completion, the No 2 engine start was commenced using APU bleed air and, once the aircraft had stopped moving, a taxi clearance was requested and received. During the No. 2 engine start, an indication of low yellow system hydraulic pressure was presented on the ECAM and just over a minute later "terrible smoke" became apparent in the flight deck just as the ground crew requested that the park brake was set, which was done.
The Captain asked the ground crew if any smoke was visible outside and was told it was not. He then asked the Senior Cabin Crew Member (SCCM) the same question and was told that the cabin was "smoky and smelly". The First Officer suggested going back onto stand for a second time and both pilots donned their oxygen masks and checked that intercom communications using them were still normal. One minute later, the SCCM advised that there was "very thick smoke" in the cabin and soon afterwards the Captain asked the ground crew to position the aircraft back onto the stand. This was acknowledged and the ground crew requested a tug for this purpose since the one used for pushback was no longer present. Three minutes after smoke had been first sensed in the flight deck, the Captain informed the SCCM that the aircraft would be returning to the stand for disembarkation and she advised that the occupants of the cabin "could not breathe". Another member of the cabin crew instructed passengers to remain seated. The Captain told the First Officer to "keep the APU running and that he would shut the engines down" but then a minute later "said that he was going to turn off the APU bleed in order to stop the air circulation". Information from the cabin continued to indicate that conditions in the cabin remained very bad with one estimate of visibility as "four rows". Concurrently, conditions in the flight deck had improved.
The Captain confirmed with the SCCM that an evacuation would be necessary and, five minutes after the first signs of "smoke" had appeared, he decided that this should take place at the final pushback position. The ground crew were advised of this and asked if passenger steps could be made available and asked if the doors could be opened from the inside.
At about this time, one of the cabin crew had donned a PBE unit which had ignited immediately they had pulled the two activation lanyards. The wearer immediately removed the unit and dropped it on the floor near the L3 door where it continued to burn despite the discharge of four halon fire extinguishers on it and caused localised fire damage. On being advised of this, the Captain called for the attendance of the fire service and, seven minutes after the first appearance of "smoke" in the flight deck and two minutes after deciding to disembark using external steps, ordered an emergency evacuation over the PA. All doors except L3 were used and all slides deployed normally. The fire service personnel gained access to the aircraft "by removing their shoes and climbing up the escape slide extending from R1 door".
It was concluded that overall, the evacuation of the aircraft had been well-managed but on exit, "the passengers wandered close to the aircraft as they were not given directions as to what to do or where to go" and on being advised of the evacuation, "ATC did not issue any instruction to stop airside operations and several aircraft and vehicles continued moving". One other aspect of the evacuation which drew attention from the Investigation was the reluctance of cabin crew to remove their shoes before using the evacuation slides. They reported being "worried that their feet may be injured due to the impact with the ground when reaching the end of the slide" and those female crew wearing the skirt rather than the trouser uniform option "added that they felt uneasy using the slides as they were wearing skirts". These factors were considered to have compromised the assertiveness of some cabin crew and it was considered that there may be a need to evaluate and enhance cabin crew training in the management of an emergency situation.
In respect of the flight crew response to the situation, it was noted that:
- initiation of the eventual evacuation by the Captain had been delayed for three minutes after he had become aware from the explicit statements of the cabin crew of the severity of the situation in the passenger cabin.
- Although the abnormal checklist included in the QRH required the flight crew to shut down the APU immediately in case of smoke generation, the crew did not implement that step and the APU remained running which allowed more mist to enter the cabin.
- CRM during the occurrence had been generally effective.
In respect of crew Standard Operating Procedures (SOPs), it was noted that:
- There was no dedicated on-ground emergency smoke or mist Checklist. The Checklists contained in the Operator's FCOM and CCOM were relevant to in-flight smoke and included items that were not applicable to an on-ground smoke or mist emergency.
- The Abnormal Checklist deals with 'mist' under the generic term ‘smoke’.
In respect of the annunciated yellow hydraulic system malfunction, inspection of the exterior of the aircraft in situ disclosed evidence of hydraulic fluid leakage coming from the tail fin with fluid having flowed down around the aft fuselage and into the APU air inlet. The Operator’s maintenance crew found that the hose which supplied hydraulic fluid under pressure to the rudder yellow actuator in the vertical fin was the source of the leaking fluid. A laboratory report on the failed hose, which had been installed at build in 2003, concluded that the origin of the failure was most probably, fatigue degeneration of the metal braiding which had then led to failure of the core pipe it contained. It was noted that the APU air intake is fitted with a diverter and fluid gutters which help to drain or divert fluids flowing along the fuselage towards the inlet on the ground or in flight which minimises but cannot entirely prevent fluid ingestion from a large hydraulic leak which occurs on the ground. This meant that there had been sufficient ingestion of fluid to generate a significant quantity of atomised hydraulic fluid which had formed the mist that filled the cabin after entry through the air conditioning system.
In respect of the ignition of one of the PBEs, a considerable number of the Operators B/E Aerospace PBE Units of the same type as the one which caught fire were examined and several were found to have similar faults. No single cause was identified but the Investigation determined that "it is highly probable that the PBE caught fire because of manufacturing defects". Once it became clear that the malfunction which had occurred was not unique, two Prompt Safety Recommendations (PSRs) were issued as follows:
- that the FAA should consider removing from service all suspect (B/E Aerospace) PBE units, P/N 119003-11, as identified by the manufacturer between S/N 003-34983M and S/N 003-35563M. [PSR41/2014]
- that the FAA should consider undertaking a review of the reliability of the in-service (B/E Aerospace) PBE P/N 119003-11. [PSR42/2014]
The initial response of the FAA was an undertaking to work with the NTSB and the Original Equipment Manufacturer (OEM) to investigate the issue raised and determine the best course of action. Subsequently, the FAA has issued an ADD 2016-11-20, which requires inspection and replacement if the pouch is damaged, as well as the removal of the PBE-11 units before 15th Jan 2018, whatever the condition of the pouch.
Some specific observations relevant to the effectiveness of the Operator's SMS were also made, including the following:
- when introducing uniform skirts as an alternative to uniform trousers for female cabin crew, no safety risk study was carried out because it was "considered that the skirts would provide the same safety performance". It was noted that "the Operators Safety Unit was not consulted on the change, nor was it requested to prepare a risk analysis exercise on the change".
- There was no specific requirement that trainee cabin crew use a packed PBE unit in the simulator class. The already-opened dummy PBE units used in simulator training were not equivalent or close to real life use and there was no specific requirement in the Operator's training procedure to require female crew members to wear uniform clothing.
- "The probability of an evacuation on the ramp was not taken into account by the Operator, nor had there been a situation that might have required addressing the need for such a procedure. The Operator's evacuation procedure, checklists, as well as training, were all attuned to an in-flight fire, therefore, the cockpit and cabin crew were not experienced with, or trained for, an evacuation on the ramp."
Airport/ATC Emergency Management issues were identified as follows:
- When made aware that passenger disembarkation airside and then an emergency evacuation airside was intended, ATC did not treat the situation with an appropriate level of urgency by ATC. Other aircraft and vehicles were permitted to manoeuvre in close proximity to the aircraft. Although there were no unsafe consequences, the Investigation believed that a hazardous situation was created.
- The airport authorities did not take sufficient action to facilitate the evacuation by protecting the area of the Aircraft and making personnel, equipment, and facilities available to safeguard and guide the evacuated passengers and appeared to lack efficient procedures to manage an aircraft evacuation on the ramp.
The formal statement of Cause of the dense mist entering the aircraft cabin was "the failure of a yellow hydraulic system rudder servo hose that allowed leaking hydraulic fluid to enter the APU where the fluid was heated and atomized and was then fed into the cabin air conditioning system" and that "the cause of the hydraulic hose failure was not determined".
The formal statement of Probable Cause of the subsequent PBE fire was "manufacturing defects in the PBE candle (which) caused a vigorous chemical reaction in the candle which resulted in abnormal ignition when the cabin crew member who had donned the equipment pulled the activation lanyard".
A Contributing Factor in respect of the hydraulic fluid mist in the cabin was determined to have been that “the flight crew decided to leave the APU running in case it became necessary to shutdown both engines, but they did not close the APU bleed as required by the SMOKE/FUMES/AVNCS SMOKE checklist which meant that that mist continued to enter the cabin. This decision was taken without having positively identified the sources of the smoke/mist".
Nine new Safety Recommendations were issued at the conclusion of the Investigation as follows:
- that Emirates Airline, in conjunction with Airbus, assess the risk of amending the existing SMOKE/FUMES/AVNCS, SMOKE and SMOKE/FUMES REMOVAL Checklists to distinguish between in flight and on-ground smoke or mist scenarios, and insert appropriate text in Checklists. [SR45/2016]
- that Emirates Airline conduct a safety risk analysis of cabin crewmembers’ uniforms for appropriateness in dealing with onboard emergency situations. [SR46/2016]
- that Emirates Airline consider a policy of initiating comprehensive safety risk assessments in cases of any addition to, or change of, existing processes or equipment that may have a significant effect on air safety. [SR47/2016]
- that Emirates Airline address cabin crew simulator training to ensure that it accurately reflects actual operational conditions in terms of clothing worn and PBE use. [SR48/2016]
- that Airbus assess the risk of amending the existing SMOKE/FUMES/AVNCS, SMOKE and SMOKE/FUMES REMOVAL Checklists to distinguish between in flight and on-ground smoke scenarios, and insert text in the checklists to differentiate between the aircraft be it on the ground or in flight. [SR49/2016]
- that the Karachi Airport Authority review this incident with a view to improving procedures regarding care for passengers evacuated on the ramp. [SR50/2016]
- that the GCAA ensure that all UAE aerodromes regularly exercise their procedures for controlling and guiding passengers, evacuated from an aircraft, terminal building or other building airside to a secure location away from the scene of the occurrence. [SR51/2016]
- that the International Civil Aviation Organisation (ICAO) establish a working group composed of regulatory authorities, aircraft manufacturers, and operators, assisted by research centres, to define the health effects of exposure of aircraft occupants to smoke/fumes/mist and to assist in determining the most appropriate treatment for any potential adverse impacts on occupant health. [SR52/2016]
- that the International Civil Aviation Organisation (ICAO) form a taskforce to study the possibility of improving the international Aviation Data Reporting Program (ADREP) system utilizing the European Co-Ordination Centre for Aviation Incident Reporting Systems (ECCAIRS), to contain a comprehensive checklist for incidents related to the aircraft interior environment, and the potential symptoms that occupants could suffer after exposure to contaminated cabin air. [SR53/2016]
The Final Report of the Investigation was issued on 12 July 2016.
- Fire Smoke and Fumes
- Cabin Fumes from Non-Fire Sources
- Emergency Evacuation on Land
- Hydraulic Problems: Guidance for Flight Crews
- Aircraft Bleed Air Systems
- Emergency and Abnormal Checklist
- Checklists - Purpose and Use
- Electronic Centralized Aircraft Monitor (ECAM)
- Halon Fire Extinguishers
- Risk Assessment
- Crew Resource Management
- Contamination of aircraft cabin air by bleed air – a review of the evidence, CASA Australia, 2009.