B737-700
Flight Crew Last 90 Days 240; Flight Crew Type 769
Situational Awareness; Troubleshooting
Aircraft Equipment Problem Critical
Flight Crew Overcame Equipment Problem
Weather; Aircraft
Pushback occurred at (time). On the pushback I was instructed to start the number 2 engine. I started the number 2 engine and verified a normal start. All engine indications were operating within normal parameters. Next; I was instructed to start the number 1 engine. Again; a normal engine start was observed. After completion of the Before Taxi Checklist; I obtained clearance to taxi the aircraft to Runway XX. Just prior to turning onto Taxiway D the number 2 engine rolled back. I let ATC know that we had an issue and would like to stop our taxi and asses our situation. The parking brake was set and we both started to apply Risk and Resource Management to this situation. We communicated that it would be a good idea to get our Support People involved. The Captain handed control of the aircraft over to me while he contacted Maintenance and Dispatch. After several minutes of consultation with Maintenance and Dispatch and also consulting the QRH; we were instructed to restart the number 2 engine.The engine was started and operated within normal parameters. After the start; the Captain; in coordination with Maintenance and Dispatch; performed an operational check of the engine. The engine again appeared to be normal. After several throttle advances and several minutes running at idle; the Captain and I; as well as Dispatch and Maintenance; to my knowledge; agreed it was safe and acceptable to continue the flight. After the Captain was through speaking to Dispatch and Maintenance; the Captain conveyed that Maintenance showed no prior history on the number 2 engine. All of the information I was receiving at the time was third hand. At this point the Captain and I worked together on the 'shared mental model.' This would define our expectations and plans going forward. We both formed a solid contingency plan by communicating risk and intentions with thorough briefings as we do on every flight of every day. The plan was to return immediately to XXX should anything happen after takeoff. We were cleared for takeoff on Runway XX. It was my leg to [destination airport]. I applied takeoff thrust and scanned the engine instruments briefly and preformed a normal takeoff.The flight operated normally through most of the flight. It was during our descent that we both noticed an audible thump noise in 3 quick successions; coming from the number 2 engine. This was followed by another audible noise. Almost immediately; we both recognized what appeared to be a compressor stall. My Pilot Monitoring quickly referenced the QRH and performed the procedure. The determination was made through the QRH that the engine should remain operational and not shut down; (per the procedure). We decided to land in [destination airport] at this point in time; given that we were closest to that location. We discussed and communicated a thorough arrival plan. The Captain; after a discussion with me decided to become the Pilot Flying. I became the Pilot Monitoring for the rest of the flight. We continued to [destination airport] with a short visual approach in VMC conditions with no further abnormal indications. The approach was made successfully and a normal landing was performed.Had we not been involved with Company Personnel during this situation; the Captain and I would have returned to the gate without question. It is my belief that this scenario would have still played out the same regardless of a gate return. My personal litmus test for continuing on any flight I operate is this: Can I put my three children and wife into this aircraft and takeoff knowing it is safe to do so? I did not have any feeling; not one goose bump that what we were doing was egregious in any way. In my mind; we were assessing a potential risk with subject experts involved on multiple levels. Without a doubt; we as Pilots and Mechanics need more clear guidance on engine malfunctions while on the ground. I felt frustrated due to the lack of information on engine assessment for oursituation; i.e. cold-soaked; first flight; windy conditions; and possibly go-no-go guidance.
After pushback; we had a normal start on both engines. To make the left-hand turn after the Before Taxi Checklist; I pushed up the no. 2 engine to approximately 35% N1 and we headed up the hill to Runway XX. After about 20 seconds of taxiing up the hill; and with the no. 2 engine still at approximately 35% N1; the First Officer and I saw the no. 2 engine roll back; with the EGT gauge flashing a white; 'FAIL.' We noted nothing appeared wrong with the engine; such as vibration or EGT; which was then 360 degrees and decreasing; and I told the First Officer we would get turned onto Taxiway D and I would tell the Passengers we had a controlled takeoff time 10 minutes from then; to help explain the engine shutdown.At the time; the First Officer and I used all of the resources available to us to get more information and help us assess the situation to form a shared mental model. Because the engine had only been running for about two minutes; less than the recommended warmup time of five minutes; and it was cold and gusty; we decided to call Maintenance before returning to the gate. I gave control of the aircraft to the First Officer; who then got out the QRH; and I called Dispatch to request a patch to Maintenance. Maintenance Control said to restart the engine and run it up while he looked to 'See if the engine has any history.' We did that; running the engine to first 40% N1; and then 65% and back to idle several times. The engine responded normally to the throttle inputs and I told this to Maintenance. This took around five minutes; after which Maintenance confidently said; 'The engine does not have any history; you're okay to go.' I conveyed this to the First Officer and we considered that it was somewhat cold outside (-5C) and windy (15G30) and the engine hadn't reached the five minute warmup time before it shut down. I told him I felt we were safe to continue if all parameters were normal in the five to seven minutes we had before takeoff. He agreed. To preclude a mindset of only the right engine possibly failing on takeoff; I re-briefed the engine failure profile and emphasized that either engine could fail; not just the no. 2. The First Officer and I agreed [departure airport] was our best airport if we had an engine failure on takeoff or climb out and Runway XX would be best suited for the winds; which were 300/15G30.Of note; just after hanging up with Dispatch and Maintenance Control; there was [another aircraft] that ATC wanted to know if we would want to get ahead of. We declined to give the engine a few more minutes to warm up. It was during this time that I should have made a logbook entry regarding the right engine; but I forgot to do so.Though a little slower to spool to 40% compared to the no. 1 engine; but not outside of what I would consider normal; all parameters for the no. 2 engine were normal as takeoff thrust was set. All engine indications during the takeoff; climb out and cruise stayed normal; with N1; N2; EGT; Fuel Flow; Vibration (both perceived and on the gauge) were normal and nearly identical to each other.As the engines reduced power during an intermediate step down on the arrival; we heard and felt a series of three to four small compressor stalls with a slight vibration. I asked the First Officer to disconnect the auto throttles and to move the no. 2 engine; 'very slowly;' while I got out the QRH. Guidance from the QRH led us to decide the engine did not need shut down; and we would run the engine normally or at a reduced thrust setting that is surge and stall free. We again got a series of compressor stalls; similar to the first ones; at another intermediate step-down; and at that point I told the First Officer that I should do the landing. I briefed the approach; to include verbalizing that we would not be using more than idle reverse after touchdown. I requested for the First Officer to select autobrakes 2 and I set the no. 2 engine to approximately 2;300 lbs/hr fuel flow and leftit there until going to idle just before touchdown. Roll out and the taxi to the gate were normal.In hindsight; it would have been more conservative to go back to the gate and call Contract Maintenance before calling Company Maintenance Control. That will be my course of action going forward if presented with anything of this nature again. As I reflect on that morning; there were three separate issues that led me to stopping on the taxiway to call Maintenance Control versus returning to the gate; and one that directly led us to conclude taking off was a safe course of action. The three issues that led me to call Maintenance Control versus returning to the gate were 1. Only two of the recommended five minutes of engine warmup time had been achieved 2. The temperature was -5C and the winds were gusting to 30 knots from the side after we made our turn; possibly disrupting airflow into the right engine 3. It was the first flight of the day. If either of those three issues were not present for our flight (if it was warm; or the winds were steady; or the aircraft wasn't cold-soaked); then returning to the gate would have been my first course of action.Easily the biggest contributor to the First Officer and I deciding that taking off was a safe course of action was Maintenance Control and their assessment of the engine; which they are the subject matter experts on. Again; not only did Maintenance Control say we could go; but it was said in a confident tone and; with the time they had to reference their resources; sounded as if they were looking at a Go/No-Go matrix. At the time; I had no reason to doubt what guidance; information; manual or other resource they had access to reference and we assumed they had not made this decision carelessly or in haste. I could have encompassed the Chief Pilot on Call and gotten his or her opinion and also asked the Maintenance Personnel if they had a reference for their decision. As a suggestion; could there possibly be; or could we create; guidance on whether takeoff is authorized if there is any indication of abnormal engine operation before takeoff; a Go/No-Go matrix similar to deicing?
B737 flight crew and dispatch reported that during taxi the number 2 engine failed; but after restart all indications were normal until descent when the engine surged/stalled several times.