Date: 202011
Local time of day: 1201-1800
Location: ZZZ.ARTCC, US
Aircraft: Commercial Fixed Wing
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Cruise
Airspace: Class A ZZZ
ATC / advisory: Center ZZZ
Aircraft component: Electrical Distribution Relay
Component problem: Failed
Reporter organization: Air Carrier
Reporter function: Captain; Pilot Flying
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Time Pressure
Second reporter function: Pilot Not Flying; First Officer
Anomaly: Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy; Flight Deck / Cabin / Aircraft Event Smoke / Fire / Fumes / Odor
Detector: Person Flight Crew
When detected: In-flight
Result: Air Traffic Control Provided Assistance; Flight Crew Diverted; Flight Crew Landed in Emergency Condition; Flight Crew Requested ATC Assistance / Clarification; General Flight Cancelled / Delayed; General Maintenance Action
Contributing factors: Aircraft
Primary problem: Aircraft

Narrative: During cruise flight at 40;000 ft. in the vicinity of ZZZ we began to smell an electrical type smoke. Moments later the A Flight Attendant called the flight deck to report smoke in the cabin. Simultaneously the master caution came on for ELEC and the TRU (transformer rectifier unit) light illuminated on the overhead panel. I as Captain was Pilot Flying and initially transferred control to the First Officer for me to chase down the TRU checklist. I accomplished the checklist; noting that approach mode with the flight directors would be unavailable... At this point the smoke was getting thicker; and we decided to accomplish the smoke/fire/fumes memory items. After communications were established we notified ATC and asked for a left turn direct to ZZZ1. We considered ZZZ2 but figured in terms of time we were about the same distance away due to our altitude; and that with a straight line to ZZZ1 we would be able to keep both our heads in the game running through checklists and monitoring the aircraft vs a circling descent into mountainous terrain. It was at this point that the First Officer made me aware that all his flight and NAV displays had failed. He thus transferred control back to me as the Pilot Flying and he took over the smoke/fire/fumes checklist in the QRH.ATC told us to expect one of the north runways into ZZZ1; but we told them we wanted [Runway] XXL as we were just on the north side of the airport so that was closest. We requested direct ZZZZZ on the ILS to backup our visual approach; and used our emergency authority to proceed at about 320 knots in order to expedite landing. At this point the First Officer discontinued the smoke/fire/fumes checklist at step 20; having noted at step 16 that we should not delay landing in order to complete the checklist. We then briefed and ran a descent and approach checklist. I asked the First Officer to call ZZZ1 OPS to let them know we were coming and for them to relay the info to Dispatch but at that point the #2 radio and comm panel had failed and the ACARS was no comm. It was with the master caution recall on the descent checklist that we realized how many issues were piling up beyond the TRU and smoke. Looking up after being prompted by the recall we saw a solid portion of the overhead panel was lit.With the glare from the smoke and setting sun we were only able to pickup the airport just outside of ZZZZZ. I disconnected the autopilot and proceeded to fly a visual approach backed up by the LNAV track for the ILS XXL. I quickly realized that electric trim was inoperative and proceeded to trim manually. With the landing checklist we also discovered that the auto speed brake would not arm; so I asked the First Officer to back me up for the manual deployment. We landed in the touchdown zone and exited at gate without incident where CFR was waiting. We stopped in order for CFR (crash fire rescue) to do a quick external inspection. As it was pretty quickly obvious the smoke was inside the aircraft and they weren't seeing anything outside; we asked them to get out of the way so we could get to a gate and let our passengers stop breathing fumes.After shutting down the engines the APU appeared to be supplying only partial power and the ground call horn sounded constantly. Due to this issue the cabin was already dark; and knowing we were dealing with an electrical issue we opted to remove all power from the aircraft and performed the secure checklist. Then we took a breath and asked each other (at the same time) 'well; how'd that go'. Of course sitting on the ground I feel like I can armchair quarterback the situation and nitpick some of the decisions; but overall I feel like we handled the situation well. We had good crew coordination given the circumstances (on O2) and the First Officer did a great job of running the checklists as well as keeping an eye on my flying once we had to transfer controls back to me. It did feel weird turning away from ZZZ2 since it was practically right below us; but I still feel like it was the correct decision given the circumstances and the amount of time it would take to descend; and how much of a distraction an orbiting descent into mountainous terrain would be while trying to deal with smoke.One thing I would do differently has to do with after the situation was over on the ground. I ended up talking with the Chief Pilot; then the firefighters; then the mechanic outside the aircraft on the ramp. By the time I got back inside I couldn't find the flight attendants to debrief and see how they were doing. Upon opening the flight deck door the A had told me that they were all fine; but I would have liked to make sure and check in with them individually. I called scheduling to try and get them to transfer me in order to at least talk with them on the phone; who then transferred me to the scheduling desk where I waited on hold until it disconnected. I still hope to talk with them at some point to learn how things went in the back and find out what we could have done better for them.


Second narrative: During cruise flight at 40;000 ft. in the vicinity of ZZZ we began to smell an electrical type smoke. Moments later the A Flight Attendant called the flight deck to report smoke in the cabin. Simultaneously; the Master Caution came on for ELEC and the TR (transformer rectifier unit) light illuminated on the overhead panel. The Captain was Pilot Flying; and initially transferred control to me; in order to run the TR checklist. He accomplished the checklist; and it was around this same point the smoke was getting thicker; and we decided to accomplish the smoke/fire/fumes memory items. After communications were established the Captain told me to notify ATC and asked for a left turn direct to ZZZ1. We considered ZZZ2 but figured in terms of time we were about the same distance away due to our altitude; and that with a straight line to ZZZ1 we would be able to keep both our heads in the game running through checklists and monitoring the aircraft vs a circling descent into mountainous terrain. It was at this point that I noticed all my flight/nav displays and radios had failed as well as ACARS No Comm" being displayed on the FMS.  I immediately notified the Captain and said that it might be better if he flew.  He agreed and took control back as the Pilot Flying and I took over the smoke/fire/ fumes checklist in the QRH. ATC told us to expect one of the north runways into ZZZ1; but we told them we wanted [Runway] XXL as we were just on the north side of the airport.  We requested direct ZZZZZ on the ILS to backup our visual approach; and the Captain used his emergency authority to proceed at about 320 knots in the descent order to expedite landing. A short time later I advised the Captain that I'd like to discontinue the smoke/fire/fumes checklist at step 20 since I had reached a decision point in the QRH; and it appeared I would most likely be heads down for almost all of the rest of the flight into ZZZ1 with this exhaustive checklist; and not be able to properly; and safely perform my duties as a PM.  I came to this decision based on the fact that step 16 states we should not delay landing in order to complete the checklist. He agreed.  We then briefed and ran a descent and approach checklist. The Captain asked me to call ZZZ1 OPS to let them know we were coming and for them to relay the info to Dispatch; but I reminded him that the #2 radio and comm panel had failed and the ACARS was no comm. It was with the Master Caution recall on the descent checklist that we realized how many issues were piling up beyond the TR and smoke. Looking up after being prompted by the recall we saw a solid portion of the overhead panel was lit. With the glare from the smoke and setting sun we were only able to pickup the airport just outside of ZZZZZ. The Captain disconnected the autopilot and proceeded to fly a visual approach backed up by the LNAV track for the ILS 17L. I noticed during the approach that the Captain had to trim manually; which led me to believe that we had obviously lost electrical control.  With the landing checklist we also discovered that the auto speed brake would not arm; so the Captain asked me to back him up for the manual deployment. We landed in the touchdown zone and exited at gate without incident; where CFR (crash fire rescue) was waiting. We stopped in order for CFR to do a quick external inspection. As it was pretty quickly obvious the smoke was inside the aircraft and they weren't seeing anything outside; we asked them to get out of the way so we could get to a gate and let our pax stop breathing fumes. After shutting down the engines the APU appeared to be supplying only partial power and the ground call horn sounded constantly. Due to this issue the cabin was already dark; and knowing we were dealing with an electrical issue we opted to remove all power from the aircraft and performed the secure checklist. A short time later; CFR  and a maintenance person were able to find the cause of the TR failure and pulled one of the TR boxes out of the E&E bay (electronics & engineering); which showed significant electrical fire damage. Lesson learned: maintain awareness of the type of emergency and aircraft state; compared to how long QRH steps could take you out of the critical Pilot Monitoring role. This checklist taught me to bring my head back up and get a grasp on the fact that we were in a rapid descent; over mountains; with half of our displays and comms out and I was only half aware of some of the radio calls and aircraft state. This was more concerning to me."


Synopsis: Air Carrier flight crew reported an uneventful divert due to a fume event during cruise.