Serbia A319 at Zurich on Oct 17th 2014, engine shut down in flight
Last Update: November 22, 2016 / 16:15:02 GMT/Zulu time
A replacement Boeing 737-300 registration YU-ANK reached Belgrade with a delay of 6 hours.
On Dec 3rd 2014 the French BEA reported there had been an oil leak at the right hand engine, the engine was shut down and the aircraft returned to Zurich. Switzerland's SUST have rated the occurrence a serious incident and have opened an investigation.
On Nov 22nd 2016 the SUST released their final report concluding the probable causes of the serious incident were:
The serious incident is attributable to the fact that, shortly after take-off, the flight crew, in an overhasty manner and without prior analysis of the situation, initiated a risky landing approach, after having switched off the right engine as a result of a leak in the air-cooled oil cooler.
The following factors contributed to the serious incident:
- Poor crew resource management within the flight crew;
- Non-compliance with systems and operational requirements;
- The flight crew’s limited experience on the aircraft type.
The investigation established that the following factors, which although they did not influence the development and course of the serious incident, nevertheless still represent factors to risk:
- Engine was not switched off immediately after the master warning message had appeared;
- The flight crew landed the aircraft without having received or requested landing clearance.
The SUST reported the captain (46, ATPL, 5,184 hours total, 233 hours on type) was pilot monitoring, the first officer (47, ATPL, 6,962 hours total, 163 hours on type) was pilot flying.
The SUST described the history of the flight (quoted in entirety):
The flight crew of the Airbus A319 aircraft, registered as YU-APA, with flight number ASL 371 and radio call sign “Air Serbia three seven one”, received clearance on 17 October 2014 at 08:38:45 UTC for take-off from runway 32. There were 2 pilots, 4 cabin crew members and 119 passengers on board.
At 08:38:57 UTC, the copilot moved the thrust lever to the take-off position; take-off power was reached 15 seconds later. During this phase, the recordings show an increase of oil pressure in the left engine (ENG 1) to 308 PSI and 289 PSI in the right engine (ENG 2); at the same time, the oil quantity for ENG 1 decreased to 16.5 quarts (QTS) and 15.75 QTS for ENG 2; the latter subsequently rapidly decreased further.
At 08:39:42 UTC, the aircraft took off. Three seconds later, the copilot requested retraction of the landing gear and the autopilot 2 system was activated another 12 seconds later. At take-off, the recordings show an ENG 2 oil quantity of 4.25 QTS and at 08:40:05 UTC, a quantity of 0 QTS. Shortly afterwards, at 08:40:21 UTC, the copilot moved the thrust lever to the position climb (CL), and 3 seconds later, the ENG 2 oil pressure began to decrease rapidly from 170 PSI to 65 PSI while ENG 1’s oil pressure remained steady at 230 PSI. In the intervening period, the crew had switched the frequency to Zurich Departure.
At 08:40:40 UTC, the ENG 2 OIL LO PR master warning message was generated in the cockpit and appeared on the engine and warning display (E/WD), combined with a continuous repetitive chime (CRC). At that time, the oil pressure showed a value of 59 PSI and decreasing further. The aircraft was then climbing at an altitude of 3900 ft QNH.
The commander commented on this ECAM warning message without delay. The copilot acknowledged this and at the same time said: “I have control.” Only a few seconds later at 08:40:56 UTC, without having previously consulted the copilot, the commander requested the following clearance from air traffic control: “Air Serbia uh three seven one, request immediately return to the airport please.” The ATCO immediately granted clearance for a right turn on a heading (HDG) of 50 degrees. The commander acknowledged this message at 08:41:10 UTC as follows: “Right heading zero five zero, Air Serbia three seven one, request radar vectoring, we have a problem with engine two and please priority landing.” Subsequently, the ATCO issued the flight crew with the following instruction at 08:41:26 UTC: “Air Serbia three seven one roger, then expect vectors ILS runway two eight, I say again runway two eight, about twenty-five track miles. Make it a right turn heading zero niner zero.” This was acknowledged by the pilot.
At 08:41:34 UTC, at a flying altitude of 5400 ft QNH, the flaps and the slats were retracted. The spoilers, which had been armed for the eventuality of an aborted take-off, remained armed.
At 08:41:37 UTC, the commander asked the copilot whether he should initiate the ECAM procedure (see chapter 18.104.22.168). The copilot answered in the affirmative with the comment that he would finish the climb.
At 08:41:44 UTC, the commander initiated the ECAM procedure. At 08:41:53 UTC, 1 minute and 13 seconds after the ENG 2 OIL LO PR ECAM warning message had appeared, and in consultation with the copilot, the right thrust lever was re-turned to idle and at the same time, the ATCO informed the flight crew as follows: “[incomprehensible] Air Serbia three seven one you can stop climb now at six thou-sand feet, whatever it’s fine for you.” The ATCO gave the following instruction ten seconds later: “Air Serbia three seven one stop climb at seven thousand feet,” which he repeated five seconds later. The flight crew did not acknowledge this instruction. The recordings show that the commander commented on the ‘ENG MASTER OFF’ ECAM instruction at 08:42:03 UTC. He repeated this instruction and after having consulted the copilot, the ENG 2 master switch was moved to the OFF position at 08:42:15 UTC, 1 minute and 35 seconds after the master warning message had appeared on the E/WD. At that time, the aircraft was climbing at a flying altitude of 6440 ft QNH with an IAS of 214 kt and a ground speed of 260 kt. During this phase, the single chime sounded and the master caution message was activated five times and the warning message AUTO FLT A/THR LIMITED re-mained displayed on the E/WD. The voice recordings show that the commander was busy with the ‘engine shut down’ procedure (see chapter 22.214.171.124, ENG 2 SHUT DOWN). At 08:42:26 UTC, the thrust lever of ENG 1 was moved to the max-imum continuous thrust (MCT) position.
At 08:42:38 UTC, the ATCO contacted the flight crew as follows: “Air Serbia three seven one expect a line-up end at twelve miles, twenty-five miles from touchdown, are you ready for approach ILS two eight?” The flight crew responded at 08:42:51 UTC as follows: “Uh yes we are ready and uh...please radar vectoring for runway two eight, uh maybe we will prefer from this position visual approach for two eight.” The ATCO complied with this request and gave the flight crew the instruction, in this case, to turn right on a heading of 130 degrees. This was immediately acknowl-edged by the flight crew.
At 08:43:29 UTC, the ATCO granted the flight crew clearance to descend to 5000 ft QNH, which was immediately acknowledged. According to the flight data record-ings, the flight crew did not enter this altitude into the flight control unit (FCU). At that time, the aircraft was at an altitude of 7000 ft QNH with an IAS of 238 kt and a GS of 286 kt, and about 7 NM north-northeast of the runway 28 threshold (see annex 2).
At 08:44:09 UTC, the copilot requested execution of the ‘after take-off/climb’ check-list (see chapter 126.96.36.199), which was immediately initiated by the flight crew. The commander subsequently mentioned an approach briefing and commented to the copilot that from their position, it would be best to perform a visual approach to runway 28. The copilot did not intervene. However, he later made a statement that, whenever possible, he personally favoured an instrument approach because this could be flown in a more precise and calmer way. The commander later stated that he purposely wanted to remain in visual meteorological conditions (VMC), in order to be able to land in gliding flight at any time, should the second engine also fail. He also said that he had not wanted to fly a holding pattern to keep the windmilling time of the switched-off engine to a minimum because of the risk of fire.
In response to the ATCO’s question as to whether the flight crew had visual contact with runway 28, they answered as follows at 08:44:25 UTC: “Yes, we are ready for visually two eight, because we have one engine out and I think it’s the best thing to do visual approach from this position.” After that, the ATCO issued the instruc-tion to turn to the right on a HDG of 250 for a visual approach, which the flight crew acknowledged. The recordings show that the master switch of the auxiliary power unit (APU) was moved to the ON3 position at 08:44:40 UTC.
At 08:44:48 UTC, the ATCO granted the following clearance: “Air Serbia three seven one, you are cleared for visual approach runway two eight, you are number one, there is one aircraft at three miles but that is doing a go-around.” A few seconds later, the ATCO informed the flight crew that the fire service would be on standby. The ATCOs involved later stated that even in the absence of an urgency (PAN PAN) or distress (MAYDAY) message, they were aware that the situation had to be an emergency because of the report of engine failure and request for an immediate return to the airport. They had therefore organised all other air traffic in such a way that runway 28 was kept clear for flight ASL 371. This resulted in sev-eral go-arounds, frequency changes and instructions to change flight paths.
The recordings show that at 08:44:57 UTC, a HDG of 250 degrees and at the same time, an altitude of 3000 ft QNH were selected in the FCU. The aircraft was at an altitude of 7000 ft QNH with an IAS of 252 kt and its autopilot was still engaged.
The voice recordings show that at 08:45:11 UTC, the conversation was akin to an approach briefing. The language switched between English and Serbian and it was confirmed that the seat belt sign was switched on. Up until this point, no information had been provided to either the cabin crew or the passengers.
At 08:45:27 UTC and in the right turn towards the final approach, the autopilot was disengaged at an altitude of 6500 ft QNH and an IAS of 250 kt. The flight crew subsequently discussed the use of the speed brakes. They pointed out the high speed and established that they were a little high for the approach. During this right turn, the bank angle of 30° was exceeded at 08:45:35 UTC; the PM did not make a respective callout. At 08:45:42 UTC, the aircraft crossed the approach axis of runway 28 with an IAS of 250 kt at an altitude of 6150 ft QNH and therefore about 1750 ft above the nominal ILS/PAPI4 glideslope of 3.3°. The distance to the runway threshold was 8.8 NM. A further three seconds later, the aircraft’s bank angle reached the maximum value of 37.27°.
With a bank angle of 34.5°, the speed brakes were also deployed at 08:45:59 UTC, which simultaneously led to the disarming of the ground spoilers, which had still been armed. At that time, the aircraft was about half a nautical mile south of the runway axis at a flying altitude of 5820 ft QNH with an IAS of 241 kt. The maximum sink rate increased to up to 2880 ft/min. The bank angle of over 30 degrees was maintained until 08:46:05 UTC.
Only four seconds later at 08:46:09 UTC, the landing gear5 was lowered at a flying altitude of 5424 ft QNH and an IAS of 242 kt. The glideslope display of the instru-ment landing system to runway 28 was in full scale deflection (see annexe 4). The aircraft was still about 1700 ft above the nominal glideslope of 3.3°. The com-mander later stated that they had been aware that they were above the glideslope. However, he had considered that to be good because the engine was producing little yaw moment in idle position and in addition, it would have been easy to land had the remaining engine also failed.
At 08:46:26 UTC, the ATCO asked the flight crew: “Air Serbia three seven one, you are six miles from touchdown, can you make it a straight in? You’re a bit high.” The flight crew answered with: “Roger, we are ready,” and 5 seconds later, the flaps were deployed to position 16. The flying altitude was 4568 ft QNH and was therefore about 1100 ft above the nominal glideslope. The IAS was 224 kt. The ATCO instructed the flight crew at 08:46:37 UTC to switch to the aerodrome fre-quency. The flight crew acknowledged this. They did, however, not report to the Aerodrome Controller (ADC) until after landing.
In response to the commander’s question as to whether the speed could be ad-hered to, the copilot answered in the affirmative and mentioned that the speed brakes were still deployed. In response to the commander’s further question as to whether he intended to land with the flaps in position 3 or full, the copilot answered with 3. At 08:46:40 UTC, the LO7 position was selected – using the corresponding pushbutton – for the autobraking effect after landing. The aircraft was aligned to the runway axis when the flaps were deployed to posi-tion 28 at 08:47:18 UTC. At this time, the aircraft was at a flying altitude of 2676 ft QNH, the IAS was 195 kt and the sink rate was 1320 ft/min. The radio altimeter (RA) displayed a radio height (RH) of 1116 ft. Passing 1000 ft RH was not pointed out by the flight crew.
Only a few seconds later at 08:47:32 UTC, the flaps were deployed to position 39. The RH was 878 ft, the IAS was 176 kt and the sink rate was 1022 ft/min. Six seconds later, at an RH of about 720 ft, a single chime rang out and the notification ‘SPD BRK NOT RETRACTED’ appeared. The copilot responded immediately with: “Flight controls, speed brakes still out.” The speed brakes were retracted at 08:47:44 UTC. The ground spoilers were subsequently not armed for the landing. A short discussion about the upcoming landing took place and at 08:47:47 UTC, the copilot requested the execution of the landing checklist, which the commander initiated immediately (see chapter 188.8.131.52).
At 08:47:50 UTC, the automatic callout “one hundred above” rang out and was followed 7 seconds later by the callout “minimum”. At this time, the recordings show an RH of 600 ft. A few seconds later, the commander called out the last action line of the landing checklist, “ECAM memo”, whereupon the copilot answered with “landing imbalance monitor checked” and not with “landing no blue”, as is specified in the procedures. Immediately afterwards, at 08:48:02 UTC, the automatic callout “five hundred” can be heard in the recording. However, the flight crew’s corresponding callouts cannot be heard (see Figure 12). The aircraft was then at an RH of 500 ft, had a sink rate of 1115 ft/min and an IAS of 149 kt. This was therefore 9 kt above the correct approach speed (VAPP10). According to the glideslope display, the aircraft was 1.7 dot above the glideslope.
Only two seconds later at 08:48:04 UTC, a single chime rang out11 and the copilot immediately responded with “APU start”. The commander complied with this re-quest by activating the START pushbutton shortly before the aircraft touched down. The cabin crew were not notified (see chapter 184.108.40.206).
According to the flight data recordings, the aircraft was at an RH of 198 ft with an IAS of 144 kt at 08:48:20 UTC. The decreasing sink rate was at 1147 ft/min when the copilot mentioned that they were now on the glideslope. At 08:48:26 UTC, the automatic callout “one hundred” rang out and 8 seconds later, the radio height callouts “fifty, forty, thirty, twenty” followed by “retard, retard”. During the entire final approach to touchdown, the power output of the remaining engine remained in approach idle.
At 08:48:38 UTC, the aircraft touched down 320 m beyond the runway threshold with an IAS of 136 kt, first with its left-hand side, and two seconds later with its right-hand side main landing gear. The brake pedals were then immediately ap-plied, and when the reverse thrust was activated 7 seconds later at 08:48:47 UTC, at an IAS of 114 kt, the ground spoilers deployed (see chapter 220.127.116.11). There are no recordings of callouts from the flight crew during roll-out after touchdown. The aircraft came to a standstill about 60 m beyond the point where runway 28 crosses with runway 16. The wheel page, which automatically appears at touchdown and also shows whether the ground spoilers are deployed, was not able to display because –con-tingent on the APU start, which was initiated shortly beforehand – the APU page remained on display (see footnote 3 on page 10).
At 08:49:10 UTC, the flight crew contacted the Aerodrome controller (ADC) for the first time and notified him with regards to leaving runway 28. The ADC issued the following instruction at 08:49:22 UTC: “Air Serbia three seven one, vacate via run-way one six,” and expanded upon this instruction at 08:49:50 UTC with: “(...) vacate left via Echo seven.” The copilot subsequently pointed out to the commander that the passengers had not been informed. The commander answered that this did not matter.
At 08:50:40 UTC, the ADC instructed the flight crew to switch to the Zurich Apron frequency, which the flight crew immediately acknowledged and actioned. The question, subsequently asked and repeated, as to whether the flight crew required support, was answered in the negative by them.
At 08:54:08 UTC, upon reaching parking position, the commander requested exe-cution of the ‘after landing checklist’. The copilot confirmed this request, a further response is not discernible.
At 08:56:06 UTC, the parking brakes were applied on the allocated parking position and the left engine was subsequently switched off. The passengers and the crew were able to exit the aircraft normally.
With respect to the mechanical failure the SUST analysed:
According to in-depth investigations, material fatigue of the cooling tubes was most likely the cause of the leak in the air-cooled oil cooler (ACOC) (see chapter 1.16); this defect was the trigger for the serious incident investigated here.
It is unsatisfactory that it was no longer possible to establish with certainty what sort of component the defective ACOC was. According to the manufacturer it is only certain that it was not an OEM part. According to the aviation company’s technical bookkeeping and the information provided by the former aircraft owner, the component should have had s/n 3427. This has also been confirmed by the documents available to the investigation (see chapter 18.104.22.168.2). The adhesive traces on the defective component could allow the conclusion to be drawn that the defective component had a different s/n other than 0008; however, the correspond-ing inscription label, for whatever reason, had come loose and got lost.
With respect to human factors the SUST analysed:
According to the voice recordings in the cockpit, the commander commented on the ENG 2 OIL LO PR master warning message without delay. This conduct was appropriate: he made the copilot aware of the situation, relevant as the autopilot had not yet been engaged at that time, and the copilot as PF was predominately focused on controlling the aircraft. Immediately after that, the commander re-quested an “immediate return to the airport”. He made this decision without having consulted the copilot and under no time pressure. This contradicts the principles of crew resource management (CRM) in a two-person cockpit and contradicts the good CRM rating that the commander had been attested on several occasions during training (see chapter 22.214.171.124.2).
The flight crew’s further action was influenced by this rapid decision from the com-mander. The rush caused by the decision is a common theme that continued throughout the rest of the flight. Furthermore, the commander unnecessarily bur-dened himself with radio communications from the outset after his decision, which received optimum support from air traffic control. As a result, all other relevant fac-tors for carrying out the upcoming approach safely were given too little attention. The following points support this conclusion.
The ENG 2 OIL LO PR master warning message is a red warning message that, as a highest-priority warning, demands an immediate response from the flight crew. Performing the first two action points of the ECAM procedure, i.e. positioning the thrust lever of the respective engine to idle and moving the corresponding mas-ter switch to the OFF position, would therefore have had the highest priority (see chapter 126.96.36.199, figure 14).
As a result of communicating with the ATC, more than one minute passed after the master warning message had been triggered, until the thrust lever was moved to the idle position. The master switch had to be mentioned twice and was not moved to the OFF position until 1 minute and 35 seconds after the master warning mes-sage had appeared.
The first two ECAM procedures were also not followed as set out in OM B (see chapter 188.8.131.52 ‘crew coordination’), because a clear separation of the requested and completed actions of the PF and PM is not discernible on the voice recordings (see chapter 184.108.40.206, ‘task-sharing’). This also applies to the other procedures.
The decision to immediately return to the airport was made without a situation anal-ysis, as is stated by the aviation company in OM B chapter ‘3.10.1 evaluate situa-tion (TARD)’ (see chapter 220.127.116.11). This should have been carried out after the checklist had been actioned. In the serious incident under investigation, no such situation analysis was carried out prior to the decision to return immediately.
The option of an instrument approach to one of the runways 34/16 or 14, which are 1 km longer, with a standard glideslope angle of 3°, was not considered. The com-mander's appraisal not to fly a holding pattern because of windmilling time and to stay in VMC and above the glideslope, in the event of failure of the remaining en-gine, is not convincing. In such case, it is crucial to cut off the fuel supply as quickly as possible. The windmilling time is not important; it might indeed be of interest for maintenance, but carrying out a safe flight is the pilot’s primary concern. The fact that planning considerations for the approach included the eventuality of failure of the remaining engine appears to be insufficiently practice-orientated in view of the exceptionally low probability of occurrence applicable for the present case. Against the backdrop of the resulting unstabilised approach, this aspect was given too high a priority.
A further indication of the flight crew’s capacity overload is the fact that they most probably switched to the aerodrome frequency but did not report on this frequency, and the landing took place without clearance.
Insufficient collaboration within the cockpit continued through to the end. The com-mander did not request execution of the ‘after landing checklist’ until arriving at the parking position, and the copilot did not provide confirmation whether this checklist had been actioned or not.
Even if the two pilots were, according to the company's requirements, no longer classified as 'inexperienced' (cf. chapter 18.104.22.168) and therefore released for crew pairing, the STSB is convinced that in the whole interaction of flight procedures, flight path selection and technical problems, the two pilot's limited experience on Airbus aircraft type played a role.
The SUST praised ATC in their analysis:
Air traffic control supported the flight crew in an optimal way from the beginning. They acted in a safety-conscious way by immediately recognising an emergency situation, even in the absence of an urgency (PAN PAN) or distress (MAYDAY) message, and keeping runway 28 clear for flight ASL 371 and rearranging all other air traffic. They monitored the flight path and, 6 NM before the runway threshold, made the flight crew aware that they were too high for a direct approach. This message was appropriate for the situation and forward-thinking.
This article is published under license from Avherald.com. © of text by Avherald.com.
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