B757-200 flight crew reported a stuck throttle lever for the number one engine.
Synopsis
B757-200 flight crew reported a stuck throttle lever for the number one engine.
Narrative
Cruising at FL380 we were issued an enroute descent from ZZZ Center. I was the Pilot Flying and commanded the descent using the FCP in VNAV. The aircraft started a shallow descent and leveled off approximately 700 ft. lower. I attempted to continue the descent by engaging a different vertical mode when I noticed that the left throttle was still at cruise power. I disengaged the auto throttles and attempted to move the left throttle. It was stuck and would not move at all. The aircraft was controllable and would descend via FLC and/or VS with the left throttle at cruise thrust; the right throttle at idle and the use of full speed brakes. At this point we divided duties and I tasked the First Officer (Pilot Monitoring) to look at the QRH to see if there was guidance. After a search through the tabs and index he informed me he could not find a checklist that pertained to our situation. I then switched off the auto throttle arm switch and attempted to move the left throttle again. Still; the left throttle remained at cruise setting. I continued the descent into ZZZ trying to comply with the arrival thinking our only option was going to be shutting down an engine. We discussed getting closer to ZZZ; requesting a hold; and completing the checklist to secure the engine at a more favorable altitude and distance from the destination. I tasked the FO (First Officer) with communicating with [Dispatch] to see if Maintenance had any additional guidance hoping to avoid shutting down an engine going into ZZZ. While waiting for a response from the Company; the FO took the radios back. At this point we were well on the arrival and we were having difficulties complying with the STAR. The FO requested and received relief from the STAR and requested to descend to an altitude directly and relief from the speeds on the arrival. ATC informed us that they were [making us a priority aircraft]. We provided them with the amount of fuel on board and the number of occupants. There was communication using ACARS between us and [Dispatch]/Maintenance. There was a lot going on and I cannot exactly remember what the specifics of these messages were. I am unaware if the PM (Pilot Monitoring) advised Dispatch via ACARS that [priority had been requested]. I could have directed this task but we were in a high workload environment. I asked the FO to review the Engine Failure/Shutdown QRH in anticipation of securing the engine. Passing FL190 we received an ACARS from Maintenance requesting we try to move the throttle again. This time; I was able to retard the left throttle to idle. We then informed ATC that we had the situation under control and would be continuing and expected a normal approach and landing.I requested the in range checklist passing FL180. I did not consider terminating the [request for priority] at this point as I was uncertain if the throttle would stick again. Approach cleared us for the ILS which has many step down altitudes. At this point I made the decision to leave the auto throttles off and I complied with the altitude restraints on the arrival while using vertical speed and FLC. I was very task saturated at this point. We did not communicate again with Dispatch via ACARS because we were focused on the arrival. We completed the approach checklist. I continued the arrival approach and landing using manual throttles and I was able to add and remove thrust as needed. The arrival and approach was conducted under VMC. We made a normal landing on XXL taxing clear onto taxiway. ATC had requested CFR; which was standing by adjacent to Taxiway; and because the situation was under control we dismissed them and terminated the [request for priority]. At this point we continued to taxi to the ramp parking at Gate X. While waiting for Maintenance to tow us into the gate I communicated with Dispatch that we were safely on the ground. I made the required write up but I forgot to check the box indicating [priority had been requested]. Prior to this event Iwas unaware that this option existed. Additionally; I was given notice that I needed to report for a drug test upon arrival. After debriefing the ZZZ Maintenance crew I completed that task. I then called the [Supervisor] per the FOM to discuss the [request for priority]. We spoke several times. I also spoke with Maintenance and discussed the issue with them as well. The reason why the left throttle was stuck at cruise thrust is unknown at this time.
Second reporter narrative
Upon initial descent from FL380 with autothrottles ON the left throttle failed to retard. The CA (Captain) was the PF (Pilot Flying) and he manually tried to retard the throttles without success. We turned OFF the autothrottle system and was still unable to retard the throttle. The CA continued the descent with the right engine power as required and speed brakes. I reviewed the QRH and was unable to find any applicable procedures while also engaging our Dispatch to research possible options. The CA periodically checked the left throttle and it was remained frozen. At approximately FL240 we advised Approach of our problem and they set the [request for priority] in work. We continued to descent and began discussing possible solutions and preparing for likely engine shutdown including starting the APU. At FL190 the CA again checked the throttle and this time it effortlessly retarded to IDLE. We elected to keep the authothrottles OFF for the remainder of the flight and made an uneventful landing on our originally planned runway. CFR vehicles were available for us on landing and we cleared them off after clearing the runway.Unknown mechanical interference with the left throttle.
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Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.