B737 flight crew reported engine failure during cruise descent. Flight crew shut down engine and performed a diversion and safe landing.
Synopsis
B737 flight crew reported engine failure during cruise descent. Flight crew shut down engine and performed a diversion and safe landing.
Narrative
The event started at FL300; heading west towards ZZZ. ATC instructed us to descend and maintain FL280. At that time I input FL280 into the MCP (Mode Control Panel); the Captain verbally verified the altitude input; and selected ALT Intervene to begin the descent. The thrust levers; with A/T (auto throttles) engaged; began to retard to Idle. Moments after; the Captain and I noticed a vibration that lasted a brief moment. The vibration stopped after maybe 3 seconds and we asked each other if the other felt it- which we both confirmed. We both looked at the gauges and instruments; showing nothing un-ordinary. Moments after; I called out 'master caution' as it illuminated. The Captain noted and pointed out ENG FAIL on the engine indication DU. The EGT started to rise while the thrust was still idle and we were still descending to FL280. To confirm the engine had failed; the Captain increased the right thrust lever ever so slightly and noticed no response of engine indications. With the EGT redlining; the Captain suggested he needed to shut down the engine; I concurred.The Captain performed immediate action items and then called for the engine failure checklist from the QRH. Looking through the options on my EFB; I selected 'engine fire or severe damage' checklist because of the vibrations we felt; I presented the Captain with the checklist for his confirmation; and began reading.After the 4th step of the checklist; the Captain told me to continue with the checklist as he began other tasks; such as communication with ATC and beginning a mild drift down with data from the FMC. I continued with the checklist; reading and communicating every action out loud. I advised the Captain the last step was to land at the nearest suitable airport and the next checklist was the One engine inoperative landing".In the meantime; the Captain had already [requested priority handling] with ATC and had been exploring divert airport options. He advised me that he was thinking ZZZ1 was a good option. We looked at the current weather at ZZZ1; discussed the lack of terrain and elevation; the distance from our current position; and runway/approach applicable. We agreed it was an excellent option. The Captain instructed me to resume the radios; I advised ATC of our request to land ZZZ1 to which they cleared us direct. The Captain communicated with Dispatch who agreed with the plan. The Captain then called for the. "One Engine Inop Landing" checklist. I ran the checklist out loud again; confirming with the Captain.The Captain then communicated with the Flight Attendants and requested that I build the approach. Once the approach was built; I briefed the Captain on the ILS X into ZZZ1; followed by the deferred descent checklist. We received vectors for the approach; the Captain made a very smooth landing; taxied to the gate; and we ran the shutdown checklist."
Second reporter narrative
We were cruising towards ZZZ at FL300 over northwest Location A. We received a descent to FL280 slightly ahead of the flight plan for reported turbulence ahead. We were using VNAV so I used altitude-intervene to start a cruise descent. The FMC switched ahead into VNAV descent mode. The relevant factor here is that the FMC commanded idle thrust to descend. I set to work on recruising the box.Just as the throttle was about halfway back we experienced a mild airframe vibration ZZZ3ting for a few seconds. I paused and asked the FO if he felt it. He said he did. It was slight; like a cooling fan making noise; a loose panel; or gear door vibrating in the wind. I looked at the engine indications but they were normal. Engines frequently shake slightly as they spin down so that was another possible explanation for the vibration. A few seconds later the FO alerted me to a master caution. I looked around and saw ENG FAIL overlayed on the EGT display. The EGT was rising. N1 on both engines had come back to idle as commanded by the FMC; fuel flows were low and matched; no engine or airframe vibrations existed anymore; and we had good oil pressure and temperature. The EGT was now stabilized above redline. I was hesitant to treat it simply as an Engine Limit Surge or Stall since I was perplexed to see ENG FAIL in combination with high EGT and low fuel flow. I considered possibilities like a faulty EGT sensor. Since I didn't even really know if the engine had failed; I cracked the thrust just off the idle stop watching fuel flow and EGT closely. There was absolutely no response. Something was definitely wrong. I considered the failure and overtemp indications to be reliable.I decided it had to be shut down and conferred with the FO. I called for the Engine failure Shutdown Checklist based on the ENG FAIL condition. Step 1 refers to vibration and; having previously disregarded that as normal and unrelated; we reconsidered. The abnormal indications appeared very soon after the unexplained vibration so severe damage seemed likely. I called for and performed the engine fire severe damage immediate action items. At that point I divided duties. I flew and talked to ATC. The FO ran the Engine Fire Severe Damage Checklist. It seemed like a natural division of work since I was already flying. I wanted something specific from ATC so I took the radios too. I looked up driftdown speed and altitude; declared an emergency; and obtained a descent clearance to FL230. There were clouds below FL260. Not wanting to descend into ice I opted to drift down slowly; set max continuous thrust; and let ATC know what we were doing. I chose to defer calling for the Driftdown Checklist to prioritize handling severe engine damage.Then I took a look at nearby airports on the MFD (Multi-Function Flight Display) and my EFB. By this time we were into Location B and ZZZ1 was barely further away than ZZZ2. ZZZ1 weather was good and ZZZ1 was also preferable to ZZZ2 for field elevation and terrain. ZZZ3 was further away than ZZZ1. Behind me were regular airports ZZZ4 and ZZZ5; but these have elevation and terrain. ZZZ6 was a close airport but it doesn't have long runways and we hadn't computed landing distance per the checklist yet. It also has high elevation and nearby terrain. I considered the time it would take to complete all checklists as well as terrain; field elevation; my familiarity; and weather. ZZZ1 was the best option. The FO liked the plan so I got a turn towards ZZZ1 and asked ATC to pass along to Dispatch what we were doing. Dispatch sent me a voice frequency (ZZZ Radio) via ACARS. I briefed Dispatch and told him our plan for ZZZ1. He had no objections so we continued. I gave the purser a brief and instructed her not to prepare for evacuation. We set up for the approach and I directed the FO to brief it. I made a PA to the passengers apologizing for the delay to ZZZ due to engine shutdown and emphasizing a normal landing in ZZZ1. We finished the Engine Inoperative Landing Checklist and landed flaps 15 from vectors to ZZZ1 ILS Runway X. I never saw a need to run the Driftdown Checklist so I never initiated it; rather opting to manage flight path via normal means.We received a gate assignment about 10 minutes before landing and passed it along to ATC at crash-fire-rescue's request. Landing was normal so I released crash-fire-rescue and taxied to the gate. Maintenance found broken metal debris in the tailpipe of the #2 engine. There were no injuries.
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Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.