Date: 201901
Local time of day: 0001-0600
Location: ZZZ.Airport, US
Flight conditions: Mixed
Weather elements / visibility: 10
Light: Night
Aircraft: B737-700
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Initial Approach
Airspace: Class C ZZZ
ATC / advisory: TRACON ZZZ
Aircraft component: Trailing Edge Flap
Component problem: Malfunctioning
Reporter organization: Air Carrier
Reporter function: First Officer; Pilot Flying
Reporter qualification: Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument; Flight Crew Multiengine
Human factors: Communication Breakdown
Anomaly: Aircraft Equipment Problem Less Severe
Detector: Person Flight Crew
When detected: In-flight
Result: Flight Crew Overcame Equipment Problem; General Maintenance Action
Contributing factors: Aircraft; Human Factors
Primary problem: Aircraft

Narrative: On approach to Runway XX at ZZZ at 6;000 feet; it was our last flight of the night and we were working on about at a 10 hour duty day. We had been in the same aircraft all day with ACARS MELed. The [weight and balance system] worked through the WiFi for the most part; but it seemed to be spotty at times. The clearance was for us to descend to 4;000 feet and to slow to 190 knots. As we slowed; I called for flaps 2 in order to expedite the descent; as it appeared we were next for the approach and had just passed abeam the field. We received a clearance to turn base and at that moment we received a Master Caution and a Flight Control light. Looking up at the Flight Control panel we noticed the Yaw Damper light was illuminated and the Yaw Damper switch was off.The Captain noticed that the yoke was displaced a large degree to the left; and at that moment I looked at the flap gauge and noticed that we had a split flap condition which was likely the cause of all this. The right flap was almost at zero and the left flap was a little less than 1. The aircraft seemed to be struggling with the turn on the autopilot; so I took control manually; but left the autothrottle on. I knew this was against normal procedure but thought it was the best way to manage the situation and the Captain agreed. She got out the QRH while I talked to ATC to arrange for somewhere to hold while we worked the problem. There was some initial confusion as to which checklist to use as there are many that seem to cover issues with the flaps. We ended up running the Trailing Edge Flap Asymmetry Checklist which quickly led us to the Trailing Edge Flaps Up Landing Checklist.This checklist was mostly uneventful; however; the Captain was having some trouble getting the [weight and balance system] to work. She was ready to call Dispatch and have them run the numbers for Flaps Up when I suggested that we switch duties. I felt comfortable with the [weight and balance system] and it would allow me to rest after about 30 plus minutes of hand flying in the hold. I was able to get the [performance] data from the EFB and entered it; and I ran the deferred items and the remainder of the checklist. She flew the aircraft to a landing on Runway XX. After landing we ran the Brake Cooling Module; which again took some time even on the LTE network through cellular. The 30-minute wait time from the Brake Cooling Module was reduced to about 20 after we relayed the Fire Departments thermal imaging reported temperatures to Dispatch and Maintenance through Radio 2 and they agreed.You won't be able to prevent mechanical issues from occurring. The checklists worked as advertised as we were eventually able to get on the correct one. However; the [weight and balance system] through the WiFi needs to be looked at. For one; it seems ACARS is never there when you need it anymore. I don't remember this being such a problem my first [few] years here; however; since we have gone to [the new weight and balance calculating system] it seems that the occurrence of ACARS NO COMM has skyrocketed. I am not implying that the two are related; just that my observance of ACARS issues is now more attuned to that since it is now the primary way to get our TO and Landing Data. When you combo this with our very poor WiFi service it seems that this is asking for trouble. In this situation we had plenty of gas to hold and fix our problems but we were supposed to land with a bit more than the minimum so we had time. Other flights may not and will need quicker answers through ACARS or WiFi.




Synopsis: B737-700 First Officer reported a trailing edge flap asymmetry issue on approach.