Date: 201602
Local time of day: 0601-1200
Location: ZZZ.Airport, US
Flight conditions: VMC
Light: Daylight
Aircraft: B737 Undifferentiated or Other Model
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Descent
Airspace: Class A ZZZ
ATC / advisory: Center ZZZ
Aircraft component: Electrical Distribution
Component problem: Failed
Reporter organization: Air Carrier
Reporter function: Captain; Pilot Flying
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Situational Awareness
Second reporter function: Pilot Not Flying; First Officer
Anomaly: Aircraft Equipment Problem Critical
Detector: Automation Aircraft Other Automation; Person Flight Crew
When detected: In-flight
Result: Flight Crew Became Reoriented; Flight Crew Landed in Emergency Condition
Contributing factors: Aircraft
Primary problem: Aircraft

Narrative: On descent/arrival we got a #2 Source OFF light. I called for the QRH. FO ran the checklist. After completing the checklist the Source OFF light went out but the #2 Bus OFF light came on. I called for the QRH. After running the checklist the #2 Bus OFF light stayed on. A short time later the autopilot disconnected. I tried to reengage it. It was inop. When I tried the electric trim I found it to be inop. So now I was hand flying and using the manual trim wheel to trim the aircraft. One by one we had additional failures on the arrival and approach. These additional failures were Battery Discharge Light; both Engine EEC (Electronic Engine Control) lights; FO FMC inop; FO inboard Display Unit inop; FO outboard Display Unit inop; Two out of four wing electric fuel pumps inop; Left Electric Hydraulic pump inop; PSEU (Proximity Switch Electronic Unit)  Light on; Speed Brake Do Not Arm Light on; and lastly the Trailing Edge Flap Gauge. Upon selecting flaps for the approach we noticed that the flap gauge was not working. We believed the gauge to be inop because the right side of the forward instrument panel (where it resides) was basically dead AND it felt like the flaps extended normally. The Leading Edge Devices were verified to be extended via the overhead panel. Upon selecting flaps 10 on approach; the aircraft went into an unusual and unfamiliar shudder. Believing this to be a stall buffet I lowered the nose and increased power. I told the First Officer that we must assume that we have no trailing edge flaps (meaning the flap gauge could indeed be correct). I asked him to bug me to 200 knots and select Max auto brakes. We left the flap handle at 10; increased to 200 knots and landed. The landing was completely normal despite our non-normal configuration. We did not use excessive runway and made a normal turn off at high speed turn off.


Second narrative: Descending on the arrival we experienced a Gen 2 Source off. The captain called for the QRH for source off light illuminated QRH; which I did and went to put the APU generator on the effected side. After doing so; we had the Transfer Bus Off illuminated on the same side. After completing the Transfer Bus Off QRH; we started to experience other electrical failures. The auto-pilot failed followed by the electric trim. At this point the captain was hand flying the aircraft and using manual trim. Next; the FO's display units failed as well as the FO's FMC failed; the PSEU light was on; the system A Hydraulic Electric pumped failed; both EEC lights where on; the Battery Discharge Light on; two fuel pump lights on; speed brake do not arm on. At this point we were turning into the approach. As we configured the flaps for landing we noticed the flap gauge pointer did not move properly; however the Leading Edge Devices where verified to be functionally normal. At this point we discussed that the flap gauge could possibly be failed as well. I asked the captain how the aircraft was handling while we configuring the flaps to 10 degrees. The captain stated that he felt a possible buffet and then proceeded to lower the nose and increase power to achieve a higher airspeed. We then decided to treat this condition as a flap up landing. The captain told me to set 200 knots as an approach speed and select MAX auto brakes. Captain landed the aircraft successfully and turned off.


Synopsis: B737 flight crew experienced a Gen 2 Source Off light during descent. After switching to the APU generator; the Transfer Bus Off light illuminated. After completing the Transfer Bus Off QRH; they started to experience numerous other electrical failures; among them the flap gauge. When flaps 10 was selected and the aircraft slowed; a rumble is felt and a flaps up landing procedure was followed.