EMB-170 flight crew reported an engine vibration indication resulted in a decision to shut down suspect engine and return to departure airport.
Synopsis
EMB-170 flight crew reported an engine vibration indication resulted in a decision to shut down suspect engine and return to departure airport.
Narrative
Aircraft X departed Runway XXR at ZZZ on the ZZZZZ departure. We did an auto throttle-off takeoff and all system indications were normal with no detectable vibration; just as it had been on the previous flight. At some point in the climb; both Captain and FO (First Officer) felt an abnormal vibration through the aircraft frame (feet; hands; seat; etc.). We discussed it and after leveling off at 17000 the flight attendants were contacted. The #1 could also feel the vibration and was asked to visually inspect the wings and engine cowlings for any abnormal condition (i.e. something hanging off or flapping in the wind). The #1 called back and confirmed that everything appeared normal. The #1 Engine LP vibe indicator was approximately .9 when first inspected but rose to approximately 2.2 when the throttle was reduced to level at 17000 and 250 knots. #2 engine LP and HP vibe remained normal. CA (Captain) began the Abnormal Engine Vibe checklist and as the #1 thrust lever was reduced; the vibration got worse: the indication rose to 3.6; the physical vibration increased greatly; and we could hear the vibration resonating through the airframe. Thrust lever was increased and vibe got better; but never went away. The procedure was repeated several times and each time the vibration became worse with reduction in power. Thrust was then set at approximately 50% because that is where the engine vibration seemed to be the least. The crew quickly discussed options and the Captain made the decision to return to ZZZ and shutdown the #1 engine. Dispatch was notified; ATC was noticed; the FA's (Flight Attendants) were notified and the Passengers were notified. All associated checklists were utilized and a safe landing was made on XXC at ZZZ. Looking back; the decision to shutdown #1 may or may not have been the best decision in others eyes. I agree that keeping the engine running would have provided a backup source for electric and hydraulic power. However; had we kept the engine running and it experienced a catastrophic failure during a critical phase of flight the outcome could have been drastically different. I stand by decision to shutdown the #1 engine and remove it from the equation of getting back on the ground safely. Furthermore; there was an adequate amount of stress flowing on the flight deck. Both of us performed well however I cannot say for certain that EVERYTHING was done 100% correctly. While completing the abnormal vibe checklist; I cannot recall stating CHECKLIST COMPLETE. The abnormal vibe checklist also states 'IF UNABLE TO KEEP VIBRATIONS WITHIN LIMITS; AND ENGINE PARAMETERS BECOME ABNORMAL OR EXCEED OPERATING LIMITS' to consider precautionary engine shutdown. All vibration indicators were green. The vibrations got much worse as the thrust lever was reduced towards idle and indications jumped to approximately 3.6; but realizing the reduction of thrust caused this; the thrust lever was pushed back to a higher setting. Several attempts were made to reduce thrust and reduce vibration; but each time it acted in reverse of what should have happened. Even though the ENGINE indications seemed normal; the physical indicators -along with my past experiences- pointed towards a sick engine.
Second reporter narrative
Shortly after departing XXL at ZZZ; I was the FO (First Officer) and pilot flying the ZZZZZ6 departure. After we leveled at about 5;000 ft.; I asked the Captain if he felt that vibration in which he replied yes. I called for autopilot on. We continued our climb to 17;000 at 250 kts. in which we remained until deciding to come back to ZZZ. During the climb; the Captain asked the Flight Attendant to look out the window and see if anything appeared abnormal on the wings/engine. She advised us that everything appeared normal. We then told ATC while we would like to remain at 17;000 ft. for now while we run some checks. We then ran the high engine vibration checklist. I was still the pilot flying at the time; and as the Captain reduced #1 thrust lever; the vibration became much worse. We attempted multiple times; but it was too much of a vibration to keep trying. The highest we saw was 3.6. At this point; the Captain and I decided that we would plan to return to ZZZ and [request priority handling] as well as do a precautionary shut down on engine 1. The Captain notified dispatch; atc; the flight attendants; and the passengers. We decided that the Captain would fly us back and I would run the QRH. We then proceeded to run the precautionary engine shut down checklist; engine out descent checklist; emergency landing checklist; and engine out landing checklist. We made a safe landing back at ZZZ.
Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.