Date: 201912
Local time of day: 0001-0600
Location: ZZZ.ARTCC, US
Light: Daylight
Aircraft: B737-800
Operator: Air Carrier
Operating under: Part 121
Mission: Passenger
Flight phase: Descent
Airspace: Class A ZZZ
ATC / advisory: Center ZZZ
Aircraft component: Compressor
Component problem: Malfunctioning
Reporter organization: Air Carrier
Reporter function: First Officer; Pilot Not Flying
Reporter qualification: Flight Crew Multiengine; Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument
Human factors: Distraction
Second reporter function: Captain; Pilot Flying
Anomaly: Aircraft Equipment Problem Critical
Detector: Person Flight Crew
When detected: In-flight
Result: Flight Crew Landed in Emergency Condition
Contributing factors: Aircraft; Procedure
Primary problem: Aircraft

Narrative: On descent into ZZZ near the ZZZZZ Intersection; we were about to start down from FL250 when we felt what seemed like a compressor stall as well as airframe vibrations. Checking the engine indications showed nothing abnormal nor out of limits. The Number 2 engine had slightly higher vibrations at 2.1. The Captain disconnected the autopilot and auto-throttles; and began reducing thrust. With the power back the vibrations did subside. During the descent the Captain added power on the #1 engine and we soon heard and felt what seemed similar to a compressor stall. The Captain returned the engine to idle and used #2 engine for power as necessary; however we still did not have any abnormal engine indications. At that time we notified ATC and requested direct to the field as well as Runway XXR. On the way into landing we reviewed the QRH for engine high vibration; engine severe damage; and engine limit or surge or stall. We also planned for a possible single engine flaps 15 landing just in case the Number 1 engine failed on final. All engine indications were still normal up until about a three to four mile final when the Number 1 engine vibrations began to increase with the throttle at or near idle. The highest vibration that I saw was about 3.4.Once we landed; Tower told us that they saw possible flames from the Number 1 engine and fire and rescue told us of smoke from the engine. We ran the Engine fire QRH to shut down and secure the engine; we did not fire the bottle however since we did not have any internal fire indications and the fire department was in the process of spraying the engine. We coordinated with the Fire Department and Maintenance on the field and when they agreed everything looked safe we were towed to the gate for deplaning.


Second narrative: During arrival on ZZZZZ X RNAV Arrival we had an unusual engine malfunction on the Number 1 engine requiring non-standard Crew Member coordination and communication between Pilots and Flight Attendants; significantly increasing the task loading. Since this was a rather unusual engine malfunction it is possible that incorrect checklist procedure(s) was (were) followed.In our attempts to identify the engine issue we transitioned from ENG Limit; Surge or Stall Checklist to ENG Vibration Checklist to ENG FIRE or Severe Damage or Separation Checklist. We notified ATC and we received clearance from ATC to proceed directly to ZZZ. During the descent several step-down altitudes clearances were received; however we are not 100% sure that all clearances were properly interpreted; read back and/or complied with. We were never informed by ATC about any violations.


Synopsis: B737-800 flight crew reported possible Number 1 engine compressor stall.