Flight Instructor and student reported during arrival descent the throttle became stuck. The flight crew set mixture to idle cutoff and continued to a safe landing.
Synopsis
Flight Instructor and student reported during arrival descent the throttle became stuck. The flight crew set mixture to idle cutoff and continued to a safe landing.
Narrative
While returning to ZZZ from an instructional flight with a private pilot working on his instrument rating; in which we conducted multiple approaches at ZZZ; I requested my student initiate a descent based on an overtaking aircraft about 600 ft. above us. He attempted to initiate the descent; but advised that the throttle was stuck and wouldn't respond; however; we were already in a descent. We were about 1 mile from the VFR reporting point of Johnstown for ZZZ at the time at about 6;500 ft. I took controls and confirmed that the throttle was stuck and there was strong resistance to moving it forward or backward. I checked the friction lock and confirmed it was not the issue.I notified Tower of the situation and requested to proceed direct to Runway XX. The ZZZ Tower asked if I was [requesting priority handling] and I confirmed that was the case. I did not look at the RPM at that time; but even when pitched at best glide we were descending and it was clear we would not be able to make the field. I pushed aggressively on the throttle and was able to advance it slightly to an RPM setting that would allow us to maintain altitude; I would guess around 2;200 RPM; while at best glide speed.The private pilot and student on the flight was asked to run the emergency checklist; while Tower asked if we needed any other accommodations and confirmed fuel and souls on board. I briefed the student that we would stay high until landing was assured and then again attempt to reduce to power to idle; but if that failed we would pull the mixture to idle. Upon reaching the field and at a high position with landing assured; I attempted to pull the throttle to idle; but I wasn't able to move it below approximately 1;800 RPM. I then pulled the mixture and conducted a normal landing. The propeller stopped shortly after all three wheels touched down; but we were able to make it to a taxi-way; but were unable to clear the hold short lines.I attempted an engine restart and had normal control of the throttle upon engine restart.
Second reporter narrative
While returning to ZZZ from a instrument training flight we had a faster aircraft from behind beginning to overtake us about 400 ft. above our altitude. My instructor requested for me to descend down to 6;500 ft. As I went to start my descent I went to pull the the throttle back and it did not move. I pulled it with more force and still had no luck with reducing the throttle. I told my instructor and he confirmed that it was not moving as well. My instructor took control of the aircraft and reported to ZZZ Tower of the situation and [requested priority handling]. My instructor remained in control of the aircraft while I ran some emergency checklists. We were able to move the throttle slightly forward and remain in level flight at best glide speed but were unable to move the throttle to idle. My instructor briefed the landing and said we were going to shut the engine off once the runway was made. We remained high on the straight in approach until we were assured that the runway would be made. The mixture was pulled and the engine shut down right as we begun our flare. The landing was made successfully and were able to make Taxiway XX but unable to fully exit the runway. We restarted the engine and had more control of the throttle. We safely taxied back to the hangar.
Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.