Created Wednesday, Jun 14th 2023 19:20Z, last updated Tuesday, Jul 25th 2023 18:56Z
A Smartwings Boeing 737-800, registration OK-TSO performing flight
QS-1111 from Chania (Greece) to Prague (Czech Republic), was climbing through FL250 out of Chania when the crew initiated an emergency descent due to the loss of cabin pressure, the passenger oxygen masks were deployed. The aircraft turned around and diverted to Heraklion (Greece) where the aircraft landed on runway 27 without further incident about 50 minutes after departure.
A replacement Boeing 737-800 registration OK-TVY reached Prague with a delay of about 8:20 hours.
The occurrence aircraft remained on the ground for about 7 hours, then departed for a positioning flight to Prague and is currently maintaining a maximum FL240 enroute.
Czechia's UZPLN reported in their quarterly bulletin, that the aircraft had been subjected to an engine cowl valve open indication prior to departure, the Greek maintenance engineer released the aircraft on minimum equipment list requirements. During engine start the crew noticed there was low bleed air pressure in the right hand engine and consulted with maintenance, the decision was made to continue the flight. Climbing through FL230 the cabin altitude warning horn sounded, the crew donned their oxygen masks, performed the memory items and checklist and initiated an emergency descent to FL100. The crew was unable to contact ATC, hence set the transponder to emergency code and performed the descent without clearance. A short time later contact with ATC was re-established and the aircraft was cleared to FL100, the cabin altitude was still climbing. After levelling off at FL080 the crew removed their oxygen masks, briefed the cabin, and decided to divert to Heraklion. The crew gradually opened the outflow valve, however, cabin altitude experienced large oscillations of +/- 1000 feet. It was established that Chania's Maintenance had not carried out the MEL procedures correctly resulting in incorrect handling of the valves controlling the cabin pressure.
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