Date: 201908
Local time of day: 1201-1800
Location: ZZZ.Airport, US
Flight conditions: VMC
Weather elements / visibility: Turbulence; 10
Light: Daylight
Aircraft: Cessna 152
Operator: FBO
Operating under: Part 91
Flight plan: None
Mission: Training
Flight phase: Final Approach
Airspace: Class E ZZZ
ATC / advisory: CTAF ZZZ
Aircraft component: Engine Control
Component problem: Failed
Reporter organization: FBO
Reporter function: Pilot Not Flying
Reporter qualification: Flight Crew Student
Anomaly: Aircraft Equipment Problem Critical; Inflight Event / Encounter Fuel Issue
Detector: Person Flight Crew
When detected: In-flight
Result: Flight Crew Landed in Emergency Condition; Flight Crew Overcame Equipment Problem
Contributing factors: Aircraft
Primary problem: Aircraft

Narrative: Me and my instructor were returning from flight maneuvers and wanted to do a couple of laps in the traffic pattern prior to concluding the flight. The wind conditions were approximately at 13 kts.; gusting 17 kts. There was light turbulence and as a result; I had to use a substantial amount of power to maintain pattern altitude.After a single landing; we were back on downwind; the throttle was at about 70-80% to sustain pattern altitude. However; when I decided to pull power back; I noted that the throttle was stuck. It would go the rest of the way in but no further back; resulting in us being stuck at roughly 2350 rpm (redline is 2550 rpm). I immediately reported the issue to my CFI; who promptly took the flight controls and [made a call] on CTAF. Since we had no control of power; we were forced to cut off the mixture in order to land the plane. However; as we were on final; the engine refused to quit; despite the mixture being at idle cutoff; resulting in us going around.We tried another lap in the pattern again; this time additionally utilizing the fuel shutoff valve; no luck as it would take a couple of minutes for it to take effect. In the spite of the moment; my instructor deployed flaps to slow the plane down about 5kts above Vfe (Flap Extension Speed); there was no resulting damage. On the next lap; my instructor had me hold the mixture at cut-off to ensure complete fuel starvation; but no luck; the engine still kept coming back to life at a high enough rpm to foil the landing attempt.On the last lap; I suggested turning off the mags to kill the engine when abeam our touchdown point. Fortunately; we never had to default to that plan as the throttle valve became unstuck on the final lap and we were able to perform a landing in accordance with the precautionary landing with engine power checklist. I noted a drop of oil pressure on final and the engine began to run rough. After we landed and exited the runway; the engine quit altogether.We tried a restart in hopes that we could try to cautiously taxi the plane back to the ramp; but the engine refused to start. Shortly after; the throttle became stuck again; although this had no effect as the engine was dead. We decided to run the securing checklist on the taxiway and await a tow to the flight schools maintenance hangar. When we got out to assess the plane; my instructor noted a clanking noise when moving the prop.The cause of the incident was identified as a faulty part in the float-chamber that went by the pre-buy inspection of the aircraft unnoticed and over the months; the running of the engine shook the part loose altogether; resulting in an uncontrollable flow of fuel mixture to the carburetor; resulting in a stuck throttle valve and unreliable mixture control. Fortunately; there was enough air to sustain combustion.




Synopsis: C152 student pilot reported encountering a stuck throttle and difficulty shutting down the engine while in the traffic pattern.