EMB-175 flight crew reported that during the climb the aircraft would not pressurize resulting in the flight crew returning to the departure airport. Flight had been dispatched with one pack deferred inoperative.
Synopsis
EMB-175 flight crew reported that during the climb the aircraft would not pressurize resulting in the flight crew returning to the departure airport. Flight had been dispatched with one pack deferred inoperative.
Narrative
On Day 0 we arrived at the gate at XA:10 am to board the aircraft. Upon receiving the flight release we noticed a MEL for Air Cond Pack 2 (21-XX-XX-XX) and Engine BLD Valve; bleed 1; (36-XX-XX-XY). The first Officer and I reviewed the MEL's in detail to prepare for the flight. We pushed back on time to the deice pad for Type 1 deicing with engine 1 running and APU off. After deicing was complete we checked the ECS (Environmental Control System) page to make sure everything was operating normally; blleed 2 valve open pressurizing air cond pack 1. After takeoff we had a bleed1 overpressure message at about 2000 ft; we began to conduct the QRH procedure for bleed 1 overpressure but the message went away. At about 9000ft we had an additional bleed1 overpressure message and it went away again. At this point we were concerned and brought up the ECS page and noticed the bleed2 valve was closed and pack 1 was white; meaning not pressurized. At this point we were still climbing and we checked the cabin altitude rate of climb; it seemed unusually high at a rate between 600-800 ft per min; which unusually high. Concerned that the issue was not resolving as the climb continued we asked ATC to immediately to level off of FL230 to troubleshoot the issue. The cabin was still climbing at a high rate; despite being level so we advised ATC and asked for a descent to 10000 ft. We then prepared for a cabin altitude high scenario due the cabin altitude being at 8000 ft and climbing. During the descent to 10000 we got the cabin altitude high Eicas message and conducted the EPC/ QRH procedure. Cabin altitude never went above 10500 ft so masks in passenger cabin did not deploy. The flight attendants were informed as well as the passengers. We sent an acars message to dispatch informing them as well. We then proceeded to return to ZZZ airport. We landed at 73542 lbs not overweight(74957 lbs); with a normal landing and no reported injuries. Suggestions: We are not sure what caused the pressurization issue as everything was working on the ground and in theory bleed 2 should have provided air to pack 1 through the cross bleed valve. That being said; it may be prudent in the future to avoid dispatching an aircraft that has two ECS MELs (bleed and opposite pack) as this provides no redundancy and introduces another point of failure (cross bleed).Another procedure that may be useful to add is amending the after takeoff checklist to include checking cabin pressurization. While this is part of the climb flow; it is not on the checklist and would be a useful reminder. Specifically; referencing the cabin altitude tables to know the exact values that are normal for the altitude you are at. While we felt the cabin altitude and rate of climb seemed high; as the indications were green and seemed roughly acceptable we did not feel an urgency to immediately level off and descend. If we had referenced the table we would have known earlier that despite the indications being green the values were abnormal and halted the climb earlier. It may also be beneficial to or include a more gradual pressurization issue scenario in the simulator training.
Second reporter narrative
On Day 0 we arrived at the gate at XA:10 am to board the aircraft. Upon receiving the flight release we noticed MELs for Air Cond Pack 2 (21-XX-XX-XX) and Engine BLD Valve; bleed 1; (36-XX-XX-XY). The Captain and I reviewed the MEL's in detail to prepare for the flight. We pushed back on time to the deice pad for Type 1 deicing with engine 1 running and APU off. After deicing was complete we checked the ECS page to make sure everything was operating normally; bleed 2 valve open pressurizing air cons pack 1. After takeoff we had an bleed 1 overpressure message at about 2000 ft; we began to conduct the QRH procedure for bleed 1 overpressure and the message went away. At about 9000ft we had an additional bleed 1 overpressure message and it went away again. At this point we were concerned and brought up the ECS page and noticed the bleed 2 valve was closed and pack 1 was white; meaning not pressurized. At this point we were still climbing and we checked the cabin altitude rate of climb; it seemed unusually high at a rate between 600-800 ft per min. Cabin altitude also seemed higher than normal; though not high enough to immediately think something was wrong. Concerned that the issue was not resolving as the climb continued; we asked ATC to immediately level off of at FL230 to troubleshoot. The cabin was still climbing at a high rate despite being level so we advised ATC and asked for a descent to 10000 ft. We then prepared for a cabin altitude high scenario due the cabin altitude being at 8000 ft and climbing. During the descent to 10000 we got the cabin altitude high EICAS message and conducted the EPC/QRH procedure. Cabin altitude never went above 10;500ft so masks did not deploy. The flight attendants were informed as well as the passengers. We sent an ACARs message to dispatch informing them as well. We then proceeded to return to ZZZ airport. We landed at 73;542 lbs not overweight (74;957 lbs) with a normal landing and no reported injuries.Suggestions: We are not sure what caused this pressurization issue as everything was working on the ground and in theory bleed 2 should have provided air to pack 1 through the cross bleed valve. That being said; it may be prudent in the future to avoid dispatching an aircraft that has two ECS MELs (bleed and opposite pack) as this provides no redundancy and introduces another point of failure (cross bleed).Another procedure that may be useful to add is amending the after takeoff checklist to include checking cabin pressurization. While this is part of the climb flow; it is not on the checklist and would be a useful reminder. Specifically; referencing the cabin altitude tables to know the exact values that are normal for the altitude you are at. While we felt the cabin altitude and rate of climb seemed high; as the indications were green and seemed roughly acceptable we did not feel an urgency to immediately level off and descend. If we had referenced the table we would have known earlier that despite the indications being green the values were abnormal and halted the climb earlier.It may also be beneficial to include a more gradual pressurization issue scenario in the simulator training. The scenario currently used is more rapid where it is clear there is a pressurization issue. Seeing the more difficult slow depressurization in training will likely make it easier to spot on the line..
Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.