Narrative:

I heard that there was a similar situation the day before mine where one of our aircraft had to divert in the mountains because they lost the only good pack they had left. Maybe it was the same aircraft and it nor any other aircraft should have been sent out in that situation again. I feel that myself and my crew and my passengers were placed in a dangerous situation in an aircraft that only had one operating pack in possible icing conditions. Our aircraft had a pack 1 deferral and only pack 2 was operating. Before leaving I had dispatch review our alternates. I figured that since the temp was 2 degrees and the dew point was 1 degrees with rain at our destination that it would fog in and that since the temp was 4 degrees and the dew point was 3 degrees with rain at our first alternate that it would fog in too. [Our destination] actually did fog in with 1/4 mile visibility. Our second alternate was forecasted to get gusts up to 40 knots at the time of our possible arrival. [Our second alternate] is an airport that I was not familiar with because I have never been there and it was broken at 2300 ft. So I didn't feel that it was safe for an alternate. Before we even left ZZZ the dispatcher agreed that ZZZ was a better alternate and would take less fuel to get back to than the original alternates. Plus the dispatcher notified me of the weather between ZZZ1 and ZZZ2 which was more than likely full of ice.upon reaching ZZZ1 the weather had changed drastically. It eventually went from 10 miles visibility to 1/4 mile in fog just as I had expected. We started with runway xx and then ATC informed us that traffic was using runway yy and that we should as well since the winds were calm. The winds picked up to a 12 knot tailwind for runway yy so we switched back to runway xx. As we were climbing back up to 13000 ft to set up for runway xx; the first officer (first officer) noticed that our cabin altitude was 9700 ft. We discovered that pack 2 had shut down and that the aircraft gave us no warning of this. Per the QRH we recycled pack 2 and it did not come back on. I immediately told the first officer to [advise ATC]. I used my emergency authority and turned the deferred pack 1 on and the aircraft started to pressurize back down to 6300 ft cabin altitude. So we told ATC that we wanted to go back to ZZZ. Also since pack 1 was deferred for a 'pack 1 overload' message we continuously got the 'pack 1 overload' message the entire flight before the emergency before we ever had to turn pack 1 on so because of my years of experience as an air force aircraft mechanic and my 14 years of experience on this aircraft I felt confident that it was a bogus message since the pack wasn't even on all that time. I tried and it worked and saved our dire situation.ATC climbed up back up to 15;000 ft which seemed like a safe altitude in case we had to do an immediate descent if pack 1 failed. Plus when the anti-ice system came on the cabin altitude went up to 6700 ft so I felt a lower altitude was safer. We chose to have ATC to assist us to fly up the valleys to the north east so we weren't crossing any peaks in case pack 1 failed at which time we had 4800 pounds of fuel which was 1300 pounds above our bugout fuel. By the time we got past the mountains to the north west of ZZZ we were still above our bugout fuel of 3500 pounds. Pack 1 maintained pressurization the entire time. I had ATC descend us as soon as possible after we were clear of the mountains and then continued for a normal landing. The mechanic looked at pack 2 and said it failed because there was a line missing. After the fact I feel that the route we took and the diversion airport of ZZZ was still the safest and best decision considering the weather over the other alternate airports. We could have diverted to ZZZ2 that had similar conditions to ZZZ1 and it could have fogged in too or we could have diverted to ZZZ3 with high gusty winds and would have had to gone missed and diverted back to ZZZ and then wewouldn't have enough fuel to fly up the valleys and get back to ZZZ safely. Also the weather mass that was moving between ZZZ1 and ZZZ2 probably had a lot of ice in it and we didn't want to fly through that with our one operating deferred pack 1. And we flew up those valleys at 15000 ft above mountain top elevation.I've been told by several pilots that on the xr's that pack 2 kicks off all the time with no warning. I have seen pack 2 on other xr's kick off with a warning before and reset it per the QRH and it took a few minutes to come back online. Maybe all these xr's are missing this line that the mechanic told us about. Plus I think that flying over the mountains on one operating pack in possible icing conditions is as dangerous as taking off on one engine. This should not be allowed anymore.

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Original NASA ASRS Text

Title: XRJ Captain reported diverting over mountainous terrain after an air-conditioning pack failed and the other was inop.

Narrative: I heard that there was a similar situation the day before mine where one of our aircraft had to divert in the mountains because they lost the only good pack they had left. Maybe it was the same aircraft and it nor any other aircraft should have been sent out in that situation again. I feel that myself and my crew and my passengers were placed in a dangerous situation in an aircraft that only had one operating pack in possible icing conditions. Our aircraft had a pack 1 deferral and only pack 2 was operating. Before leaving I had dispatch review our alternates. I figured that since the temp was 2 degrees and the dew point was 1 degrees with rain at our destination that it would fog in and that since the temp was 4 degrees and the dew point was 3 degrees with rain at our first alternate that it would fog in too. [Our destination] actually did fog in with 1/4 mile visibility. Our second alternate was forecasted to get gusts up to 40 knots at the time of our possible arrival. [Our second alternate] is an airport that I was not familiar with because I have never been there and it was broken at 2300 ft. So I didn't feel that it was safe for an alternate. Before we even left ZZZ the dispatcher agreed that ZZZ was a better alternate and would take less fuel to get back to than the original alternates. Plus the dispatcher notified me of the weather between ZZZ1 and ZZZ2 which was more than likely full of ice.Upon reaching ZZZ1 the weather had changed drastically. It eventually went from 10 miles visibility to 1/4 mile in fog just as I had expected. We started with runway XX and then ATC informed us that traffic was using runway YY and that we should as well since the winds were calm. The winds picked up to a 12 knot tailwind for runway YY so we switched back to runway XX. As we were climbing back up to 13000 ft to set up for runway XX; the FO (First Officer) noticed that our cabin altitude was 9700 ft. We discovered that pack 2 had shut down and that the aircraft gave us no warning of this. Per the QRH we recycled pack 2 and it did not come back on. I immediately told the FO to [advise ATC]. I used my emergency authority and turned the deferred pack 1 on and the aircraft started to pressurize back down to 6300 ft cabin altitude. So we told ATC that we wanted to go back to ZZZ. Also since pack 1 was deferred for a 'pack 1 overload' message we continuously got the 'pack 1 overload' message the entire flight before the emergency before we ever had to turn pack 1 on so because of my years of experience as an Air Force aircraft mechanic and my 14 years of experience on this aircraft I felt confident that it was a bogus message since the pack wasn't even on all that time. I tried and it worked and saved our dire situation.ATC climbed up back up to 15;000 ft which seemed like a safe altitude in case we had to do an immediate descent if pack 1 failed. Plus when the anti-ice system came on the cabin altitude went up to 6700 ft so I felt a lower altitude was safer. We chose to have ATC to assist us to fly up the valleys to the North East so we weren't crossing any peaks in case pack 1 failed at which time we had 4800 pounds of fuel which was 1300 pounds above our bugout fuel. By the time we got past the mountains to the North West of ZZZ we were still above our bugout fuel of 3500 pounds. Pack 1 maintained pressurization the entire time. I had ATC descend us as soon as possible after we were clear of the mountains and then continued for a normal landing. The mechanic looked at pack 2 and said it failed because there was a line missing. After the fact I feel that the route we took and the diversion airport of ZZZ was still the safest and best decision considering the weather over the other alternate airports. We could have diverted to ZZZ2 that had similar conditions to ZZZ1 and it could have fogged in too or we could have diverted to ZZZ3 with high gusty winds and would have had to gone missed and diverted back to ZZZ and then wewouldn't have enough fuel to fly up the valleys and get back to ZZZ safely. Also the weather mass that was moving between ZZZ1 and ZZZ2 probably had a lot of ice in it and we didn't want to fly through that with our one operating deferred pack 1. And we flew up those valleys at 15000 ft above mountain top elevation.I've been told by several pilots that on the XR's that pack 2 kicks off all the time with no warning. I have seen pack 2 on other XR's kick off with a warning before and reset it per the QRH and it took a few minutes to come back online. Maybe all these XR's are missing this line that the mechanic told us about. Plus I think that flying over the mountains on one operating pack in possible icing conditions is as dangerous as taking off on one engine. This should not be allowed anymore.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.