B737 flight crew reported a cabin pressurization issue related to a pneumatic bleed valve failure.
Synopsis
B737 flight crew reported a cabin pressurization issue related to a pneumatic bleed valve failure.
Narrative
Began delayed due to maintenance on inbound aircraft. Captain spoke with the inbound crew when they arrived and was informed of further issues with the left air conditioning pack. The Captain and I reviewed the release and discussed the restrictions and procedures regarding the air conditioning pack. Since it was a short taxi; we ran through the MEL and followed and configured the aircraft for the bleed off take off then taxied out. After take off we referenced the MEL and followed the after take off procedure. During climb out I monitored the cabin pressure gauge and the aircraft appeared to be pressurizing. We were told to climb to FL250 at a good rate and continued to climb. During the climb a bleed trip off light came on. We investigated to see if that was associated with the previous condition and continued to monitor the cabin pressure. Approaching FL250 we noted that the cabin [altitude] had reached approximately 9;000. Shortly after level off the cabin [altitude] rapidly increased and we received a cabin altitude warning. We requested priority handling and immediately asked for a descent and ran the immediate action items for the Cabin Altitude Warning. The flight attendants called and let us know the oxygen masks in the cabin had also come down. We informed them we had a pressurization issue and to have everyone put their masks on. We continued and ran through the Cabin Altitude Warning checklist as well as the bleed trip off checklist. We descended below 10;000 and updated the flight attendants. We coordinated with ATC for our arrival into ZZZ and landed without further incident.
Second reporter narrative
The aircraft had been having several recent problems with the air conditioning system and the left pack was currently on MEL. We configured for a bleeds off takeoff and reconfigured the system as per MEL after takeoff. Sometime thereafter; the right bleed trip off light illuminated. Thinking it was associated with the other problems reported we did not take immediate action and began to lose pressurization. We donned oxygen masks; requested priority handling; and descended to a lower altitude (10;000 ft) and ran checklists for the bleed trip off and pressurization problems. The rest of the flight and landing was uneventful. The flight attendants were briefed during the emergency and debriefed afterwards. They told us that the passengers weren't alarmed during the incident. I also made an announcement to the passengers after the oxygen masks dropped in the cabin to reassure them that things were okay. The compacted time and busyness of this short flight added a threat to dealing with the problem.
More incidents for this aircraft family →
Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.