Canada B773 near Calgary on Dec 30th 2015, turbulence injures 21
Last Update: February 21, 2017 / 17:03:33 GMT/Zulu time
Passengers reported everything not fastened went flying in the cabin, a number of passengers not wearing their seat belts impacted and damaged the cabin ceiling with their heads, a number of passenger oxygen masks came down.
The Canadian TSB have dispatched investigators to Calgary.
On Jan 5th 2016 the TSB reported the aircraft encountered severe turbulence about 85 eastnortheast of Anchorage,AK (USA) causing various injuries to 21 passengers. At the same time the crew received a "R BLEED" EICAS message causing the shut down of the right hand #2 air conditioning system. The aircraft diverted to Calgary and landed about 2.75 hours later. The aircraft sustained damage to its interior furnishing and a failed clamp holding a duct of the #2 air conditioning system.
On Jan 19th 2016, while reporting another occurrence see Accident: Canada B773 near Anchorage on Dec 30th 2015, turbulence injures flight attendant, the Canadian TSB mentioned that due to a SIGMET the crew of AC-16, flying about 90 minutes ahead of AC-88, anticipated moderate to severe turbulence and illuminated the fasten seat belt sign about 15 minutes prior to the first turbulence.
On Feb 21st 2017 the Canadian TSB released their final report concluding the probable causes of the accident were:
Findings as to causes and contributing factors
- Air Canada flight 088 entered an area of moderate to severe turbulence that was caused by the jet stream traversing the southern coastal mountains of Alaska.
- The acceleration forces encountered resulted in passengers who were not wearing seat belts contacting various furnishings and surfaces in the cabin causing a variety of injuries, including 1 serious injury.
Findings as to risk
- If training material does not contain complete information pertaining to all of the factors that contribute to turbulence, then there is a risk that the best course of action will not be taken.
- If flight crews and dispatchers do not receive all pertinent information relating to flight conditions, optimal decisions on a course of action may not be made, increasing the risk of exposure to adverse conditions.
- If systems such as an aircraft communications addressing and report system are not utilized to their full capacity, then there is a risk that more detailed information about flight conditions will not be available.
- If cabin lighting is not sufficiently bright, then there is a risk that cabin crew members will miss unfastened seat belts due to the lack of contrast of the seat belt material and concealment by blankets.
- If there is no visual or audible indicator associated with not wearing a seat belt, then there is an increased risk of non-conformity with respect to seat belt use.
- If seat belt announcements do not contain sufficient detailed information on anticipated turbulence, then there is a risk that passengers will not immediately comply and maintain compliance with an instruction to fasten seat belts.
- If safety announcements made by cabin crew do not use language that conveys the expectation of compliance, there is a risk that passengers will perceive these announcements to be less authoritative, which may result in non-compliance.
- If passenger safety briefings lack information on the effects turbulence can have on individual passengers, their possessions, and on others, then there is a risk that it will reduce the probability of seat belt use.
- If passengers do not expect consequences and enforcement for non-seat belt use, passengers may not perceive the use of seat belts as mandatory, when so directed.
- If the approach to improve seat belt use does not include an understanding of the cultural and social norms of passengers, education to increase awareness, improved attitudes and an associated enforcement program to ensure corresponding changes in behaviour, then there is a risk that passengers will not wear their seat belts.
- If V-clamps are not installed using the proper procedure and torque, then there is a risk of V-clamp failure and subsequent partial loss of an air conditioning system and cabin pressurization.
- The Air Canada flight 088 flight crew’s decision to secure the cabin and reduce to turbulence penetration speed contributed to preventing significant numbers of injuries in the cabin and potential damage to the aircraft.
The Canadian TSB reported that Air Canada Flight AC-16 enroute at FL350 was about 90 minutes ahead of AC-88. Both aircraft received a SIGMET (Significant Weather Information) in flight at 16:35Z indicating moderate to severe turbulence near Anchorage between FL240 and FL400. About 80 minutes later AC-16 entered the zone identified by the SIGMET and encountered moderate to severe turbulence. The crew issued a Pilot Report (PIREP) and descended the aircraft to FL330 where it appeared to be calmer. However, the crew decided to climb to FL350 again to get above cloud. The aircraft experienced another turbulence encounter resulting in an injury to a flight attendant, see also Accident: Canada B773 near Anchorage on Dec 30th 2015, turbulence injures flight attendant. The aircraft again descended to FL330.
Based on the PIREP Anchorage Center as well as Air Canada Dispatch informed the crew of AC-88. Both relief crew was at the controls when the aircraft was nearing Anchorage. About 35 minutes prior to entry into the zone identified by the SIGMET and PIREP the augment first officer informed the cabin crew, that they were nearing the jet stream, there had been a report of severe turbulence by an aircraft at higher altitude, and instructed cabin crew to stop service and secure the cabin. Cabin crew, while keeping the cabin lights at sleep mode, walked the cabin to stow all loose items and check the seat belts were fastened, announcements were made in English, French and Mandarin.
At 19:22Z Anchorage Center informed the crew that there had been more severe turbulence reports between FL280 and F350 and a moderate turbulence report at FL390. Based on the company dispatch information the crew decided to maintain FL330 which was indicated as level with the least severe turbulence by dispatch as well as visual cues.
Just before the aircraft penetrated the zone of turbulence, a passenger in the business class got up to visit the washroom, at this time all flight attendants were already seated with their lap and shoulder harnesses fastened. A flight attendant instructed the passenger to immediately return to the seat and fasten the seat belt, the passneger however insisted on using the washroom. While the passenger was returning from the washroom, but had not yet arrived at the seat, the aircraft encountered the first jolt at about 19:23Z, which threw the passenger against the ceiling and back onto the floor.
The crew turned the aircraft 30 degrees to the right, the turbulence ranging from moderate to severe, subsided after about 2 minutes, the vertical accelerations were between +0.14 and +1.7G. A second period lasting 8 minutes of light to moderate turbulence followed, a third period of 7.5 minutes of moderate to severe turbulence followed with vertical accelerations between -1.32G and +2.21G. Most of the injuries occurred during the third encounter.
Between 19:26Z and 19:35Z the crew received indication "BLEED LEAK R" on their EICAS screen indicating the air conditioning system #2 had failed. As the #1 air conditioning system had overheated on the previous flight (maintenance had not found any fault and released the aircraft to service) and earlier on the occurrence flight, the crew was concerned, that both systems might fail and they would need to descend, minimum safe altitude was 18,600 feet at their point of route however.
Once the turbulence had settled, captain and first officer returned to the flight deck and took control of the aircraft, the relief crew took the observer seats to assist. The crew contacted dispatch to discuss options for diversion, Vancouver as nearest diversion airport would require higher minimum altitudes and was ruled out. Calgary was chosen to divert to due to terrain clearance, maintenance available and passenger convenience to continue the journey from. In addition the longer runway at Calgary would permit for lower brakes temperature for the overweight landing.
Most of the passengers received minor injuries including sprains, strains, bruises and scrapes. One passenger located near door L4 received serious injuries and remained in hospital care for an extended period of time. Most of the injured did not have their seat belts fastened, two had slept and not heard the announcements.
Two infants on board were held in their caregivers' arms and were not injured. A child restraining system was not used, nor was it required to be used.
The TSB analysed: "For Air Canada flight 088 (ACA088), the flight crew’s weather package indicated an area of moderate turbulence, which was usual for this route of flight at that time of year. There was no information in the pre-departure weather package that would have prompted the captain to consider a different route."
The TSB analysed regarding the turbulence:
ACA088 entered an area of moderate to severe turbulence that was caused by the jet stream traversing the southern coastal mountains of Alaska. The 2 encounters of severe turbulence were consistent with the jet stream flowing over 2 prominent mountainous areas located 85 nautical miles (nm) and 191 nm east-northeast of Anchorage.
The significant meteorological information (SIGMET) I2 forecast severe turbulence through a large altitude range (flight level [FL] 260 to FL400) in an area where mountain wave activity could be created by the jet stream. The flight crew of Air Canada flight 016 (ACA016), which was 90 minutes ahead of ACA088, concluded that FL330 was likely the best altitude for flight through this area. This conclusion was made when ACA016 happened to be at this altitude and in the area between the prominent mountain ranges, where there was less mountain wave activity created by the jet stream.
Air Canada flight 006 (ACA006), the Boeing 787 at FL390 that was 30 minutes ahead of ACA088 on the same route of flight did not encounter severe turbulence because its operational capabilities allowed it to fly significantly higher than the tropopause.
With respect to the Pilot Reporting and flight following the TSB analysed:
This information was relayed to ACA088 in time for the flight crew to determine how best to avoid the turbulence. The information the flight crew had received from Air Canada dispatch and Anchorage Air Route Traffic Control Centre (ARTCC), as well as the visual cues, suggested that FL330 was the best ride. As a result, and because they had not received any course deviation information, the flight crew decided that FL330 and the current course was the best option. With a view to preventing injury, the augment first officer ordered the cabin and flight deck to be secured ahead of the turbulence.
The information from ACA016 about a more southerly route being a possible mitigation for the severe turbulence was never relayed to ACA088’s flight crew. Whether this southerly deviation would have been smoother is unknown; however, if flight crews and dispatchers do not receive all pertinent information relating to flight conditions, optimal decisions on a course of action may not be made, increasing the risk of exposure to adverse conditions.
In this occurrence, none of the flight crews used the turbulence-reporting feature on the position report page of the aircraft communications addressing and report system (ACARS). The reporting system has several scales that allow a detailed report to be made, which is then captured by the flight planning system for future use. Neither the flight crew of ACA088 nor the Air Canada dispatcher fully appreciated the level and intensity of the turbulence. A detailed turbulence report, such as the one provided by the ACARS, could have helped them understand the severity and duration of the turbulence. If systems such as ACARS are not utilized to their full capacity, then there is a risk that more detailed information about flight conditions will not be available.
With respect to cabin preparation the TSB analysed:
With approximately 35 minutes’ notice, the cabin crew of ACA088 began to secure the cabin in preparation for turbulence. Due to the cabin crew’s efforts, approximately 94% of the passengers were not injured and no flight attendants were injured. However, 21 (6%) of the passengers were not wearing their seat belts and were consequently injured.
Seat belts were visually checked by cabin crew. However, on ACA088, this was done in low-light cabin conditions, which may have impaired detection of unfastened seat belts. Seat belts are generally dark-coloured and difficult to see in low light. Furthermore, several passengers were using blankets, which may have hidden the seat belts entirely.
If cabin lighting is not sufficiently bright, then there is a risk that cabin crew members will miss unfastened seat belts due to the lack of contrast of the seat belt material and concealment by blankets.
Aircraft Registration Data
Aircraft registration data reproduced and distributed with the permission of the Government of Canada.
This article is published under license from Avherald.com. © of text by Avherald.com.
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