Date:	Tuesday 17 October 2023
Time:	06:15 UTC
Type:	Boeing 737-8K5 (WL)
Owner/operator:	TUI Airways
Registration:	G-TAWD
MSN:	37265/3939
Year of manufacture:	2012
Engine model:	CFMI CFM56-7B
Fatalities:	Fatalities: 0 / Occupants: 193
Other fatalities:	0
Aircraft damage:	None
Category:	Serious incident
Location:	North Sea, East coast of UK, off North Lincolnshire -   United Kingdom
Phase:	En route
Nature:	Passenger - Scheduled
Departure airport:	Manchester International Airport (MAN/EGCC)
Destination airport:	Kos Airport (KGS/LGKO)
Investigating agency:	AAIB
Confidence Rating:	Accident investigation report completed and information captured

Narrative:
TUI Airways flight BY2258, a Boeing 737-800, was climbing through FL130 after takeoff from Manchester Airport when the crew received a "CABIN ALTITUDE" warning and discovered that both bleed air systems had been inadvertently left off after departure. The crew turned both systems on and continued the climb, however, at FL200 the crew received "PACK" caution and stopped the climb again. The crew consulted with maintenance and decided to return to Manchester where the aircraft landed without further incident.

The taxi out and the departure from Manchester were uneventful. The commander was PF and recalled he manually flew the aircraft until the after-takeoff checks were completed. The after-takeoff checklist, carried out by the PM on a challenge and response basis, includes a check that the bleed air switches are selected on. Both pilots recall completing this checklist and were sure that the bleed switch positions were visually verified as being on.

The commander recalled that, with the aircraft passing approximately 15,000 ft amsl, the cabin altitude warning light illuminated accompanied by the associated warning horn. In his report the commander stated that ‘It was quickly noticed that both engine bleeds were off, these were placed straight back on and the problem was resolved.’ The commander then stated ‘The aircraft was levelled off and the QRH1
was actioned. Once this was completed, shortly afterwards the right pack failed.’ Neither pilot actioned the QRH Cabin Altitude Checklist which contains memory items, including the immediate use of oxygen masks.

The commander recalled noticing that both engine bleed switches were selected to off and that he directed the co-pilot to switch them on. Both pilots recalled that the bleed switches were selected on before they requested a level off at FL150 from ATC. Once the aircraft was level the commander recalled that memory items from the checklist for cabin altitude warning should have been completed. However, as the bleed systems were now on and believing the situation to be under control, he decided that the memory items, including the use of oxygen masks, were disproportionate to the situation.

Once level the commander checked the cabin altitude indication on the overhead panel and recalled it was approximately 2,000 ft and believed this was achieved “within a couple of minutes” of the engine bleed switches being selected on. He then decided that the crew should read through the checklist to ensure there were no actions he felt should be done or any other information they should be aware of. Satisfied that the situation was under control and that the cabin altitude was below 3,000 ft, the crew felt safe to continue the flight and a further climb was requested from ATC.

During the climb the master caution illuminated and drew the attention of the crew to a pack caution on the overhead panel indicating a fault in the right air conditioning pack. The crew requested a level off at FL200 from ATC and actioned the QRH checklist for a right pack caution. They were not able to recover the right air conditioning pack and, aware this would impose some limitations on the return flight, the commander decided to discuss the situation with the operator’s maintenance control (Maintrol). After consulting Maintrol it was agreed that the aircraft should return to Manchester. As the aircraft was above maximum landing weight the crew planned to enter a hold with the landing gear extended to burn fuel and reduce weight. The senior cabin crew member was brought to the flight deck for a briefing and the situation was explained to the passengers over the public address system. Once the aircraft weight had been satisfactorily reduced the aircraft made a normal approach to Runway 05 at Manchester.

Damage Sustained to airframe
Per the AAIB report "None". Note that the very same aircraft was involved in a highly publicised runway excursion at Leeds Bradford Airport (LBA/EGMN) just three days later on 20 October 2023 (see separate AAIB report and ASN entry). After being repaired and returned to service, the same aircraft was involved in a Landing gear retraction problem during climbout, Thessaloniki (Greece) 7 October 2024 (just under one year later (see link #8)).

1. AAIB Report 14 November 2024: https://assets.publishing.service.gov.uk/media/67335df9bac74dd6026bf2dd/Boeing_737-8K5_G-TAWD_11-24.pdf
2. https://www.flightglobal.com/safety/bleed-air-switch-lapse-preceded-tui-737-cabin-altitude-incident/160774.article

Built 2011. First flight 8 February 2012 in manufacturers test registration C-GFWD. Delivered to Thompson Airways as G-TAWD 23 February 2012. Between 23 February 2012 and 27 April 2024, this aircraft alternated 10 times between TUI Airways (as G-TAWD) and Sunwing Airlines (as C-GFWD later C-FYSD).

As noted above, as G-TAWD this aircraft has been involved in at least three serious incidents
1) Cabin Pressurisation incident North Lincolnshire 17 October 2023 (the above incident)
2) Runway Excursion Leeds Bradford Airport 20 October 2023
3) Landing gear retraction problem during climbout, Thessaloniki (Greece) 7 October 2024

Total amount of flying hours accumulated on the airframe: 34,653 as at 12 May 2023

Other occurrences involving this aircraft


20 October 2023	G-TAWD	TUI Airways	0	Leeds/Bradford Airport (LBA/EGNM)		min
Runway excursion

G-TAWD: Boeing 737-8K5 (WL) (c/n 37265, l/n 3939) Built 2012. Arriving on flight BY6596/TOM25C from Bournemouth to Tenerife South Airport, Granadilla de Abona, Tenerife, Canary Islands 18th January 2019

Date/time	Contributor	Updates
18-Nov-2024 11:30	Dr. John Smith	Added
18-Nov-2024 11:32	ASN	Updated [Source, Embed code, Narrative, Accident report, ]