EMB-145 crew reported a cabin pressurization malfunction resulting in an emergency descent. The crew diverted to an alternate airport and landed safely.
Synopsis
EMB-145 crew reported a cabin pressurization malfunction resulting in an emergency descent. The crew diverted to an alternate airport and landed safely.
Narrative
We were operating a flight from ZZZ to ZZZ1 [airport]; about an hour into the flight we were cruising at FL360; I heard the First Officer mention 'look' and observed a 3000+ FPM climb on the cabin rate indication. The cabin altitude was at 8000 at FL360; and it started increasing in 500 feet increments; the First Officer pulled out his oxygen mask and I soon followed; we both donned it; and by the time we established communications we had the aural warning also cabin altitude in red 12000 and increasing. My best estimate was that the cabin was climbing at 8000 FPM considering the change in cabin altitude within the time it took. We both agreed it is rapid decompression; I took the controls and advised the First Officer to advise ATC to request 10000 feet or the lowest they can get us. The center controller didn't immediately acknowledge; so after observing TCAS I selected a lower altitude and started a rather shallow descent; she got back to us a few seconds later and asked if we were [requesting priority handling]. We said yes; and was granted 15000; and then roughly 15 seconds later she granted 11000; we accomplished the descent procedures; established communications with the FA (flight attendant). Average descent rate down to 11000 was around 5500-6000; and the cabin never dropped below 12000; and rather started climbing still; just shy of 13000. At 11000 feet we cleaned up configuration and started looking at diversion options since we were already tight on fuel going to ZZZ1. The cabin alt stayed around 10000 for awhile; and then eventually down to 8000; and then gradually started pressurizing down to 1600. At that point we had already formed a plan to divert to ZZZ2 after consulting control. We proceeded to land at ZZZ1 uneventfullyCause: Faulty equipment.Suggestions: better maintained equipment; and also I would just [request priority handling] before deviating from our assigned altitude.
Second reporter narrative
Cruising at FL360; we received rapid cabin depressurization with a 3000 FPM cabin altitude increase and I felt the pressurization change in my ears. After verifying that cabin altitude was rapidly increasing; we asked ATC for a descent to 10;000 feet; donned oxygen masks; and [requested priority handling]. We initiated a descent; and then ATC approved 15;000 feet shortly after. We then executed descent procedure with gear and speed brakes extended; descending at approximately 7000 feet per minute. ATC then approved 11;000 feet. Cabin altitude reached approx. 13000 feet at the highest point; and descended with our altitude as we passed through around 14000 feet. Cabin altitude stabilized at 11000 feet when we reached 11000 feet MSL. Once stabilized; we raised landing gear and advised ATC we wanted to divert to ZZZ2 [airport]. We got radar vectors first; then a route to ZZZ2 at 11000 feet. Cabin altitude slowly re-pressurized to approximately 2000 feet. We then were cleared to and landed at ZZZ2 without further abnormality.Cause: The rapid cabin depressurization was the reason for the [request for priority handling] and initial altitude deviation from our ATC clearance.Suggestions: Unsure of reason for cabin depressurization; but possibly maintenance related actions could help prevent future depressurization events. I don't think anything could have prevented or predicted this event from occurring. Looking back; I don't think either of us should have done anything differently as all procedures were followed and memory items completed.
Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.