On 6 June 2023, a Boeing 717-200 was on base leg about 10 nm from Hobart when chlorine fumes became evident on the flight deck. As the aircraft became fully established on final approach, the Captain recognised signs of cognitive impairment and handed control to the initially unaffected First Officer. Just before touchdown, he was similarly affected but was able to safely complete the landing and taxi in. The same aircraft had experienced a similar event two days earlier with no fault found. The Investigation determined that the operator’s procedures for responding to crew incapacitation in flight had been inadequate.

On 8 June 2016, a Boeing 737-800 en-route to Seville had already reverted to alternate automatic pressurisation control when this also failed. Manual system control was attempted but was unsuccessful so an emergency descent followed by diversion to Toulouse was then completed without further event. A similar pressurisation control fault had occurred earlier that day but had not been properly dealt with by an appropriately qualified engineer. Both system controllers were showing faults and were replaced as were a ruptured flexible hose and a series of malfunctioning drain valves. More reliable controllers and routine checking of system performance were recommended.

On 8 February 2022, a Boeing 767-300ER inbound to Madrid at FL340 experienced a failure of automatic pressurisation control followed almost three hours later by a failure of manual control and rapidly rising cabin altitude. An emergency was declared and descent made to FL120 where manual control was regained. The flight was completed without recurrence. The failure cause was found to have been water leaking from a tube with a broken clamp which, when it froze, had blocked the air conditioning outflow valve doors. Elements of the system design, scheduled maintenance requirements and fault detection were identified as contributing factors.

On 17 November 2021, after a Boeing 737-800 commenced initial descent into Patna from FL350, a cautionary alert indicating automatic pressurisation system failure was annunciated. When the initial actions of the prescribed non-normal procedure did not resolve the problem, the system outflow valve was fully opened, and a rapid depressurisation followed. After this incorrect action, the relevant crew emergency procedures were then not properly followed. It was further concluded that the captain had temporarily lost consciousness after a delay in donning his oxygen mask. The context for the mismanaged response was identified as outflow valve in-service failure.

On 23 February 2016, a Boeing 737-800 departing New Chitose encountered sudden-onset and unforecast heavy snowfall whilst taxiing out. When the right engine ran down and cabin crew reports of unusual smells in the cabin and flames coming from the right engine were received, it was decided that an emergency evacuation was required. During this evacuation three passengers were injured, one seriously. The engine fire was found to have been in the tailpipe and caused by an oil leak due to engine fan blade and compressor icing which had also led to vapourised engine oil contaminating the air conditioning system.

On 13 July 2018, a Boeing 737-800 cruising at FL370 at night experienced a sudden rapid depressurisation. An emergency descent to FL 090 followed but the cabin altitude was not manually controlled and after the cabin pressure had risen to that equivalent to 7000 feet below sea level, immediate equalisation of cabin and actual altitudes resulted in a second sudden depressurisation. Diversion to Frankfurt Hahn was completed without further event. The first depressurisation had resulted from a transient and rare pressure controller malfunction but passenger injuries were considered attributable to a complete absence of pressurisation control during the emergency descent.

On 1 June 2019, a Boeing 787-8 lost all cabin air conditioning after both packs failed less than an hour from its destination, Narita. When the Cabin Altitude reached 10,000 feet, the descent already commenced was completed as an emergency descent and the flight thereafter was without further event. The Investigation found that although an amended non normal procedure restricting pack resets to a maximum altitude of 35000 feet had been issued almost two months earlier, it was still “under review” at the operator which has since amended their procedures for assessing manufacturer communications which have operational safety implications.

On 3 August 2018, smoke appeared and began to intensify in the passenger cabin but not the flight deck of an Airbus A319 taxiing for departure at Helsinki. Cabin crew notified the Captain who stopped the aircraft and sanctioned an emergency evacuation. This then commenced whilst the engines were still running and inadequate instructions to passengers resulted in a completely disorderly evacuation. The Investigation attributed this to inadequate crew procedures which only envisaged an evacuation ordered by the Captain for reasons they were directly aware of and not a situation where the evacuation need was only obvious in the cabin.

On 19 October 2012, a Jet2-operated Boeing 737-800 departing Glasgow made a high speed rejected take off when a strange smell became apparent in the flight deck and the senior cabin crew reported what appeared to be smoke in the cabin. The subsequent emergency evacuation resulted in one serious passenger injury. The Investigation was unable to conclusively identify a cause of the smoke and the also- detected burning smells but excess moisture in the air conditioning system was considered likely to have been a factor and the Operator subsequently made changes to its maintenance procedures.

On 5 March 2011, a Finnair Airbus A320 was westbound in the cruise in southern Swedish airspace after despatch with Engine 1 bleed air system inoperative when the Engine 2 bleed air system failed and an emergency descent was necessary. The Investigation found that the Engine 2 system had shut down due to overheating and that access to proactive and reactive procedures related to operations with only a single bleed air system available were deficient. The crew failure to make use of APU air to help sustain cabin pressurisation during flight completion was noted.

On 5 March 2018, the crew of an Airbus A320 in descent towards Karachi observed a slow but continuous drop in cabin pressure which eventually triggered an excessive cabin altitude warning which led them to don oxygen masks, commence an emergency descent and declare a PAN to ATC until the situation had been normalised. The Investigation found that the cause was the processing of internally corrupted data in the active cabin pressure controller which had used a landing field elevation of over 10,000 feet. It noted that Airbus is developing a modified controller that will prevent erroneous data calculations occurring.

On 21 February 2017, an Airbus A320 despatched with the APU inoperative experienced successive failures of both air conditioning and pressurisation systems, the second of which occurred at FL300 and prompted the declaration of a MAYDAY and an emergency descent followed by an uneventful diversion to Alicante. The Investigation found that the cause of the dual failure was likely to have been the undetectable and undetected degradation of the aircraft bleed air regulation system and whilst noting a possibly contributory maintenance error recommended that a new scheduled maintenance task to check components in the aircraft type bleed system be established.

On 12 July 2018, a Boeing 737-800 was climbing through FL135 soon after takeoff from Sydney with First Officer line training in progress when the cabin altitude warning horn sounded because both air conditioning packs had not been switched on. The Captain took control and descended the aircraft to FL100 until the situation had been normalised and the intended flight was completed. The Investigation noted that although both pilots were experienced in command on other aircraft types, both had limited time on the 737 and concluded that incorrect system configuration was consequent on procedures and checklists not being managed appropriately.

On 3 December 2017, an Embraer E190 en-route at FL310 was already turning back to Helsinki because of a burning smell in the flight deck when smoke in the cabin was followed by smoke in the flight deck. A MAYDAY was declared to ATC reporting “fire on board” and their suggested diversion to Turku was accepted. The situation initially improved but worsened after landing prompting a precautionary emergency evacuation. The Investigation subsequently attributed the smoke to a malfunctioning air cycle machine. Issues with inaccessible cabin crew smoke hoods and with the conduct and aftermath of the evacuation were also identified.

On 23 August 2017, a Boeing 767-400ER which had departed Zurich for a transatlantic crossing experienced a problem with cabin pressurisation as the aircraft approached FL 100 and levelled off to run the applicable checklist. However, despite being unable to confirm that the pressurisation system was functioning normally, the climb was then re-commenced resulting in a recurrence of the same problem and a MAYDAY emergency descent from FL 200. The Investigation found that an engineer had mixed up which pressurisation system valve was to be de-activated before departure and that the flight crew decision to continue the climb had been risky.