Date: 202109
Local time of day: 1801-2400
Location: ZZZ.ARTCC, US
Flight conditions: VMC
Light: Night
Aircraft: B737-800
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Descent
Airspace: Class C ZZZ
ATC / advisory: Tower ZZZ
Aircraft component: AC Generator/Alternator
Component problem: Malfunctioning
Reporter organization: Air Carrier
Reporter function: First Officer; Pilot Flying
Reporter qualification: Flight Crew Multiengine; Flight Crew Instrument; Flight Crew Air Transport Pilot (ATP)
Human factors: Workload; Troubleshooting; Time Pressure
Anomaly: Aircraft Equipment Problem Critical; Deviation - Altitude Excursion From Assigned Altitude; Deviation / Discrepancy - Procedural Published Material / Policy; Deviation / Discrepancy - Procedural Clearance
Detector: Automation Air Traffic Control; Person Flight Crew
When detected: In-flight
Result: Air Traffic Control Provided Assistance; Flight Crew Requested ATC Assistance / Clarification; Flight Crew Landed in Emergency Condition; Flight Crew Overcame Equipment Problem; General Flight Cancelled / Delayed; General Maintenance Action
Contributing factors: Aircraft
Primary problem: Aircraft

Narrative: Leveling at FL240 during descent into ZZZ; ATC asked us to report our altitude because she was not receiving anything from us. When we looked down; the Captain noticed that IFF 2 had a fault and switched it to his side. At about that time we both noticed a power surge which made my clock blank momentarily and the Captain noticed lights on his panel flash. Next we had a series of lights come on spaced apart by a few minutes at first and then began to come on more quickly as time passed. First we had a cooling fan supply light. Then when cleared to descend via the arrival; I pushed recall and noticed the left pack light remained illuminated. Suspecting something wrong with the power distribution system; I cycled through electrical panel wafer switch positions and found no amps coming from TR 2 or 3 and negative 3 amps on the battery. I hacked my clock. About 5 minutes had already passed. I took the radios while the Captain ran the checklist for the pack light next and shortly after; we lost the left aft fuel boost pump. I told the Captain I thought we had a power distribution problem and we were draining our battery. I thought we might be slowly shedding components due to their power sources being associated with the battery. As we passed 10;000 ft. I told the Captain and he put away the book and ran the landing checklist. While on the descent; I recommended [requesting priority handling] so we could land ASAP. I configured early in prep for a slam dunk and the Captain and I agreed to starting the APU just in case. By this time we were on base and more lights had come on. We lost the B Electrical Hydraulic Pump; had a right side window over heat light; battery discharge light; TR fail light; and a few pitot lights had come on. Then while turning to final; I noticed the short vectors would overshoot me so I clicked off autopilot and turned. That's when I noticed I had no electric trim. The Captain manually ran the trim for me as we slowed and configured and we had an uneventful landing. After the fire trucks greeted us and found no hot spots around the E & E bay; we discussed whether we had enough power on the battery and I noted the time had been 17 minutes from when I noticed the negative amps on the battery and started the clock. We continued to taxi to the gate and after the fire crew came up I went with them down to the E & E bays to do my own inspection. I didn't see or smell anything. Aircraft X is an old airplane. The older planes get the more they will have gremlins like this. Maintenance discovered a faulty number 2 generator or regulator with some certainty that an Aircraft phase was not getting to the busses. How many more lights would have come on eventually? Just thank goodness we were so close to landing when it failed.




Synopsis: First Officer reported that system annunciator lights began to illuminate so Flight Crew requested priority handling and made a landing at the destination airport. Maintenance determined an integrated drive generator had failed and on phase was not working.