Jet2.com B733 near Frankfurt on Jul 28th 2017, loss of cabin pressure

Last Update: December 21, 2017 / 18:37:20 GMT/Zulu time

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Photo of Jet2.com G-CELI, Boeing 737-300 — Jet2.com G-CELI, Boeing 737-300 (Photo credit: Ian A Gratton / Flickr / License: CC by)

Incident Facts

Date of incident
Jul 28, 2017

Classification
Incident

Cause
Loss of cabin pressure

Airline
Jet2.com

Flight number
LS-509

Departure
Newcastle, United Kingdom

Destination
Prague, Czech Republic

Aircraft Registration
G-CELI

Aircraft Type
Boeing 737-300

ICAO Type Designator
B733

A Jet2.com Boeing 737-300, registration G-CELI performing flight LS-509 from Newcastle,EN (UK) to Prague (Czech Republic) with 147 passengers and 5 crew, was enroute at FL310 about 90nm northnorthwest of Frankfurt/Main (Germany) when the crew initiated an emergency descent due to the loss of cabin pressure, the passenger oxygen masks were released. The aircraft diverted to Frankfurt for a safe landing on runway 25C about 25 minutes after leaving FL310.

The airline reported the crew performed a controlled descent following a technical fault indication. A replacement aircraft was dispatched to Frankfurt.

A replacement Boeing 737-800 registration G-GDFX positioned to Frankfurt and reached Prague as flight LS-509A with a delay of 5 hours.

Germany's BFU released their July Bulletin on Dec 21st 2017 reporting the crew received a wing body overheat indication for the right hand bleed air system while climbing to FL330. The crew requested to stop the climb at FL310, worked the related checklist shutting down the right hand air conditioning pack and bleed air. The left air conditioning system was working, the cabin altitude remained constant. About 8 minutes later the crew observed the cabin altitude was climbing, donned their oxygen masks, declared emergency and initiated an emergency descent. The cabin altitude warning was triggered and the passenger oxygen masks automatically deployed. After levelling off at FL100 the crew removed the oxygen masks and cancelled the Mayday.

The BFU reported a maintenance provider at Frankfurt assessed both air conditioning systems, which resulted in following maintenance activities:

Right hand air conditioning system:
- Overheat Accessory Unit replaced (malfunction of overheat detectors)
- Leaks were identified at the transitions from one duct to the next. The clamps were replaced.
Left hand air conditioning system:
- Overheat switch and a seal were replaced
- primary and secondary heat exchangers were replaced
- air-cycle machine was replaced
- a clamp at the flow controlling valve was replaced
- air mixing valve was replaced
In addition the cabin temperature controller, cabin pressure controller, aft outflow valve and equipment cooling overboard exhaust valve were replaced.