On 3 December 2017, an Embraer E190-100LR (OH-LKE) being operated for Finnair by their subsidiary Nordic Regional Airlines (Norrra) as FIN4NR on a scheduled international passenger flight from Helsinki to Gothenburg was in the cruise at FL310 in unrecorded night flying conditions having already initiated a return to Helsinki due to an intensifying burning smell when a similar report and the presence of smoke was reported from the cabin and smoke and a PACK FAIL annunciation occurred in the flight deck. A MAYDAY was declared to ATC reporting “fire on board” and an ATC-suggested diversion to Turku was accepted. Both pilots went onto oxygen and the situation did not worsen in flight but a precautionary emergency evacuation was ordered after landing when the cabin crew reported that the smoke was increasing again. No evidence of fire was subsequently found and the 104 occupants were unaffected by the fumes and uninjured during the evacuation but there were delays in both ground transport and a count of those evacuated.
An Investigation was carried out by the Finnish Safety Investigation Authority (SIAF). Data from the FDR, CVR and QAR data were successfully downloaded and recordings of both ATC and Emergency Response Centre radio communications were also available. It was noted that the aircraft Captain had a total of 6,300 flying hours including 1,600 hours on type and the First Officer, who had been PF for the investigated flight, had a total of 730 flying hours including 530 hours on type.
It was established that during the climb out of Helsinki, the flight crew had noticed minor fluctuations in pressurisation and had decided to cruise at a lower level than planned - FL310 - as a precaution. Soon after reaching FL310, a burning smell of unknown origin became evident in the flight deck and when it intensified, it was decided to return to Helsinki with ATC advised of a “technical issue”.
Soon afterwards, smoke appeared in the flight deck, a ‘PACK 1 FAIL’ alert was annunciated and a report of a similar ‘electrical’ smell accompanied by smoke was then received from the cabin. Both pilots donned oxygen masks in response as the aircraft continued towards Helsinki and the Captain declared a MAYDAY stating that there “was a fire on board”. However, it was noted that he did not then action the Smoke/Fire/Fumes Checklist as prescribed for such circumstances and the corresponding 7700 squawk was not set either. As the Pack Failure Checklist was being actioned, ATC asked if the crew wished to divert to Turku which was much nearer than Helsinki and the suggestion was immediately accepted. In accordance with the Pack Failure Checklist, the failed pack was initially shut down but when re-activated after the prescribed one minute interval there was no reappearance of the failure annunciation and no further failure messages subsequently occurred. With the no 1 system air supply reopened, the overall air temperature began to rise again and the fumes and smoke eventually returned.
The cabin crew were advised of the new plan and that the remaining flight time was estimated as 12 minutes. In response to ATC queries about the location of the possible fire, the Captain replied that “there was smoke in the back of the aircraft but its source could not be determined” and added that there had been “pressurisation problems” prior to the appearance of the smoke. Meanwhile, one of the cabin crew attempted to don their Protective Breathing Equipment (PBE - smoke hood) but was unable to open the bag in which it was contained.
The diversion was without further event and there was no increase in the smoke/fumes. After touchdown, 33 minutes after takeoff from Helsinki, control was handed to the Captain and the First Officer completed the after landing checklist prior to the aircraft exiting the runway. Once stopped on the exit taxiway, the senior cabin crew reported that there was still smoke in the cabin and that it had increased after touchdown. The Captain therefore ordered an (all exits) emergency evacuation and the ground emergency checklist was actioned. This included making sure that the trailing edge flaps which facilitate descent from the inner wing to the ground were re-deployed. However, once selected, the flaps take almost a minute to reach the fully down position and passengers who initially used the over-wing emergency exits did not leave the wings in the prevailing darkness in the absence of any risk-free way of doing so. Instead, with smoke no longer visible inside the aircraft, they followed the advice of the attending RFFS personnel to go back into the aircraft and use the slides at the other four exits to evacuate.
In darkness, the evacuation of all occupants to an assembly area on the adjacent grass was assisted by the use of RFFS searchlights and was completed within 6 minutes of the landing although it was noted that some passengers took their cabin baggage with them. A detailed inspection of the aircraft by RFFS personnel was then commenced and it found no signs of any fire. Some passengers had evacuated in relatively light clothing and with drizzle falling and a temperature of +3° C, “they started to feel the cold and were issued with blankets” by rescue personnel and “children and their parents were taken into the rescue vehicles for protection from the cold”. Prior to the arrival of two requisitioned city transport buses at the aircraft location 14 minutes after the evacuation had been completed, those passengers sheltering in the rescue vehicles had already departed for the initially designated evacuation point in the aircraft terminal for their condition to be assessed by paramedics but this location was then changed to the airport maintenance unit. The bus eventually departed the aircraft direct to the airport maintenance unit with 77 passengers on board 21 minutes after the evacuation had been completed. No passenger count was made until all passengers had reached the re-designated evacuation point where “attempts were made to establish the exact number of POB in conjunction with the examination” with a final figure not obtained until 1¼ hours after the evacuation of the aircraft had been completed.
The origin of the smoke and fumes
It was determined that the smoke and fumes had been consequential on rotor seizure in the Air Cycle Machine (ACM) in the no.1 air conditioning pack during the climb out of Helsinki. This had been caused by bearing failure and had led to the rotors rubbing against the fan shroud creating “bitter small and whitish smoke” which entered the cabin air conditioning system. QAR data showed that the flow from the no. 1 air conditioning pack had fluctuated significantly (and abnormally) during takeoff and its outflow valve had shutdown automatically thirteen minutes after takeoff triggering the observed flight deck alert. It was noted that a message indicating the ACM failure was only annunciated after smoke had appeared. It was also noted that the reselection of the failed pack by the crew as a result of following the prescribed checklist did not result in a display of its continuing failure.
The failed ACM was an on-condition component and was found to have a running time in excess of time after which these components are typically removed for repairs. A strip down examination showed that both turbines has suffered bearing failure and it was this which had led to contact between the fan shroud and the rotors of both turbines causing considerable fan blade damage. Moist coffee grounds were also found during examination of the fan shroud and it was concluded that these had probably originated from the forward galley sink.
According to Embraer, there had been 15 similar ACM failures during the five years prior to the event under investigation but none of the others had led to an emergency evacuation. Prior to this five year period, in 2008, it was noted that an identical ACM failure and smoke/fumes event involving an Embraer E195 had occurred after the aircraft had been despatched under MEL dispensations with its other Pack ACM already inoperative for the same reason. In this case, an emergency evacuation had also taken place.
Other Safety Issues
Because the Captain did not action the QRH Smoke Fire and Fumes Checklist in association with his declaration of an emergency, the corresponding transponder squawk 7700 was not selected at this time. One directly relevant consequence of this was that under their procedures, ATC classified and notified the situation as a “full emergency” rather than an (actual or potential) “aircraft accident” which the Captain’s transmission of “fire on board” would have warranted. The effect of this was that the Turku Emergency Response Centre (ERC) who were notified of the emergency by ATC did not (and were not required to) direct the region’s hospitals to increase their readiness.
The inability to open the bag containing the PBE unit using “reasonable force” was confirmed by a series of tests on similar bags from which it was concluded that the action required would have been “extremely difficult”. It was found that previous similar findings had resulted in the issue by OEM B/E Aerospace five years earlier of a SB which modified the design of the bag opening so that its contents could be accessed. This SB had not been mandated by the Regulatory Authorities and had not been incorporated on the bags containing the PBE units carried on the aircraft. It was noted that un-modified PBE units are provided for use in emergencies where such use could be vital to the maintenance of cabin crew functional capability in the presence of smoke and fire.
- Over wing exit evacuation
The trailing edge flaps were retracted prematurely during the landing roll and were not re-selected down - a movement which takes almost a minute - prior to the all-exits emergency evacuation being ordered. This increased the drop height from the wing trailing edge to the ground for passengers evacuating this way by approximately 0.5 metres to 2.2 metres. Reluctance to jump this far resulted in some passengers moving towards the wing tips where the drop height was even greater. Fortunately, the absence of hazardous conditions inside the aircraft on this occasion allowed passengers who had exited onto the wings to be directed back into the cabin in order to leave via the main exit slides.
- Airport emergency planning
Most of evacuated passengers were kept near the aircraft awaiting buses to transport them to the designated reception centre. These buses had to be requisitioned on the initiative of one of the attending airport fire officers. It was noted that, as was the case at many other Finnish Airports, Turku had made no emergency planning arrangements to ensure that post-evacuation bus transport would be available without undue delay, a matter of concern given the possibility that aircraft emergency evacuations may occur during severe weather conditions. It was also noted that despite illumination of the evacuation site using the lights of attending vehicles, the passengers had evacuated into an area which was “essentially enveloped in darkness” and their oversight and safety was thus hampered.
Safety Action known to have been taken by both Nordic Regional Airlines and Finnair prior to the completion of the Investigation included the incorporation of the available but non-mandatory modification to all PBE containers of the type which proved impossible to open during the investigated event.
Four Safety Recommendations were made as a result of the Investigation as follows:
- that the US Federal Aviation Administration issues an Airworthiness Directive requiring a modification to be incorporated in the PBE protective bag, P/N 119003, manufactured by B/E Aerospace Inc. to facilitate its opening. [2018-S51]
- that the Finnish Transport Safety Agency ensures that airport operators include in their emergency plans contingency procedures for the transportation of evacuated passengers at the aerodrome. [2018-S52]
- that the Ministry of the Interior cooperates with the Ministry of Social Affairs and Health, Air Navigation Services Finland and the Emergency Rescue Centre Agency to align their procedures governing actions in aircraft accidents and full emergency situations. In conjunction with this, (whether there is) a need to amend the contents of the procedures in matters related to, in particular, the contents of alert calls, response arrangements and inter-organisation communications should be investigated. [2018-S53]
- that Air Navigation Services Finland amends the alerting instructions issued to air navigation service units to clearly indicate that an emergency situation communicated on the radio or by setting the emergency code on the transponder are given an identical classification. [2018-S54]
The Final Report was published on 28 November 2018.