B737 flight crew reported a Cabin Altitude warning light during cruise. Crew referenced QRC; started an emergency descent and landed uneventfully.
Synopsis
B737 flight crew reported a Cabin Altitude warning light during cruise. Crew referenced QRC; started an emergency descent and landed uneventfully.
Narrative
Shortly after starting a VNAV profile descent into ZZZ on the ZZZZZ Arrival out of 38;000 we received a Cabin Altitude warning light and warning horn. Quickly glanced up at the Cabin Altitude and Cabin Pressurization Panels to try and find the issue and noticed cabin altitude just above 10;000 feet. I kept flying the jet; we silenced the warning horn; and confirmed the emergency. I called for the Cabin Altitude Warning or Rapid Depressurization/Emergency Descent QRC and started an emergency descent to 10;000 feet. FO (First Officer) ran the checklist and communicated with the flight attendants. Cabin Altitude appeared controllable just above 10;000 feet; and I never felt or heard a pressure change associated with a rapid depressurization. Requested priority handling with ATC and descended off profile (VNAV) to 10;000 feet. At some point during the descent (not sure when everything seems quite time compressed) I was informed that 2 passengers were experiencing medical issues related to our emergency descent/pressurization issue. The remainder of the arrival; approach; and landing were uneventful. Medical response was requested through ATC (Tower) to meet us at the gate. Slight delay getting to the Gate XX (approximately 10 minutes waiting for 777 tow off); lengthy delay (approximately 30 minutes) getting the jet bridge to the jet once parked at XX. Eventually 3 tech's were called out and got the jet bridge to operate correctly. I was able to communicate with the firemen/paramedics through an open flightdeck window and relay the limited medical information we had. The purser was busy communicating with Medlink as we waited for the jet bridge to operate correctly. Passengers with medical issues were seated at XXX (irate; extremely difficult to communicate with as relayed by purser) and XXY. Logbook write up was entered; ZZZ Maintenance was called and Maintenance was thoroughly debriefed to assist in trouble shooting the pressurization issue.
Second reporter narrative
Summary: During descent the cabin altitude warning horn sounded and CABIN ALTITUDE lights illuminated. The cabin altitude was stable slightly above 10;000 feet. Initiated an emergency descent and completed the appropriate non-normal checklist. Manual control of the outflow valve worked; and the cabin altitude was recovered to below 10; 000 feet. The Captain requested priority handling with ATC. At least two passengers complained of ear blocks and other; non-descript symptoms. Landing was uneventful. Jetbridge mechanical issues prevented the responding paramedics from accessing the aircraft for up to 30 minutes. In Flight: An on-profile VNAV descent out of FL 380 and subsequently; the CABIN ALTITUDE warnings occurred somewhere around FL 320 (plus or minus 3;000'). After silencing the Warning and assessing that the cabin altitude was stable just above 10;000. we ran the CABIN ALTITUDE Warning or Rapid Depressurization/ Emergency Descent" checklist. Though challenging; the cabin altitude proved controllable using manual control of the outflow valve. The Captain continued to fly and handle ATC communications while the FO (First Officer) ran checklists and communicated with the flight attendants who were dealing with at least two passengers complaining of related medical (trapped gas/ear blocks) concerns. Time and workload were compressed--the problem presented itself in the vicinity of the ZZZZZ1 fix on the ZZZZZ arrival--which precluded communication with Dispatch or MEDLINK while in flight; so the crew requested medical response to our planned arrival gate through ZZZ Tower when cleared to land. Landing was uneventful. Taxi Delays: We communicated to both Ramp and Company Operations that a medical response was required. Despite making the sense of urgency clear; Ramp and Company Operations informed us that we were to hold on the ramp and wait for a 777 to be towed off Gate XX. We waited at spot XX until the 777 was clear for about 10 minutes. Jet Bridge Delays: Upon arriving at Gate XX; we made a PA to the passengers to remain seated to allow the paramedics get on the airplane and see to the passenger(s) with issues. Unfortunately; the jetbridge did not move and we observed multiple technicians working to get the jetbridge to the aircraft. There was a lengthy delay. The FAs (Flight Attendants) contacted MEDLINK during this time; and the Captain attempted to communicate with the paramedics by opening the flight deck window to relay the limited information we had about the distressed passengers. Company Operations initiated a tow to an alternate gate; but just as the tow team arrived the jetbridge issues was resolved and we were able to open the cabin door. Maintenance: After engine shutdown we advised hub maintenance over the radio and requested technicians respond to the aircraft for a debrief. An ELB (Electronic Logbook) report was made. Two technicians arrived and the pilots debriefed them while still sitting on the flight deck. Bottom Line: It remains unclear how or why the cabin depressurized in this manner; but the non-normal procedure prevented the situation from getting worse. The kind of gate and Jetbridge delays encountered here seem unacceptable for an aircraft recovering with passengers in need of medical attention. END"
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Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.