Skyhawk 172/Cutlass 172
Flight Crew Student
Flight Crew Last 90 Days 38.9; Flight Crew Total 65.5; Flight Crew Type 65.5
Situational Awareness
Aircraft Equipment Problem Critical
Flight Crew Landed in Emergency Condition; Flight Crew Requested ATC Assistance / Clarification; General Maintenance Action
Aircraft
I was on a left closed pattern and after completing the GUMPS check on my downwind was cleared for a touch-and-go. After passing the landing point; I pulled on the carb heat; and pulled the throttle back for 1;500 RPM; at the same time as setting the flaps at 10 degrees as I had done for the touch-and-go before this event; and started pitching for 80-85 before I noticed that the RPM's had descended to 900. Immediately I pushed the throttle back in; to no effect. Checking the ignition switch; the primer; the fuel selection (which was at both); and the mixture (which was at full-rich); I started pitching for 65 knots and contacted the Tower that I was experiencing engine problems. In the heat of the moment; I'm still unsure if I used the word emergency; but I remember saying that I did have engine problems. After being told that I was [cleared to land]; and asked if I needed any assistance; I replied that I might need assistance and set my flaps back to neutral. I was able to land and taxi back to the FBO. However; during the taxi; the RPM jumped back up to 1900 RPM's and wouldn't go down regardless of leaning the mixture or pulling on the throttle. And at the entrance to the FBO; I took out the keys and turned off all the equipment; and got out of the plane; where I explained to the mechanics at the FBO what happened.
C172 student pilot experiences loss of throttle control when power is reduced abeam the numbers in the traffic pattern with the engine at 900 RPM. A successful idling approach and landing is accomplished. During taxi back to the FBO engine RPM increases uncontrollably and the aircraft is shut down short of the ramp and Maintenance is called.