Date: 201902
Local time of day: 0601-1200
Location: ZZZ.Airport, US
Flight conditions: VMC
Light: Daylight
Aircraft: Skyhawk 172/Cutlass 172
Operator: Personal
Operating under: Part 91
Flight plan: None
Mission: Personal
Flight phase: Final Approach
Airspace: Class E ZZZ
ATC / advisory: TRACON ZZZ
Aircraft component: Elevator Trim System
Component problem: Malfunctioning
Reporter organization: Personal
Reporter function: Pilot Flying; Single Pilot
Reporter qualification: Flight Crew Private
Human factors: Distraction; Troubleshooting
Second reporter function: Pilot Not Flying; Single Pilot
Anomaly: Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Flight Crew
When detected: In-flight
Result: Flight Crew Overcame Equipment Problem
Contributing factors: Aircraft
Primary problem: Aircraft

Narrative: I first noticed a trim stickiness when beginning descent into ZZZ1. To play it safe; I did not manipulate the trim until we had landed (as it was in an okay position on approach). Once on the ground and shutdown; the trim was taken through two cycles and appeared to be properly functional again. We departed to return to ZZZ. In the climb; approximately 10NM NW ZZZ1; the trim appeared to get stuck again. Slight back-pressure was required to maintain the desired rate of climb. Once at cruise; the trim was adjusted slightly down to maintain level flight. The decision to continue to the aircraft's base was made due to the lack of issue in cruise; availability of maintenance at the base; and need to land eventually regardless.On approach to ZZZ; it became apparent the trim was still sticky. I opted to use a longer downwind in order to allow for more time to prepare for the approach. Once on final approach; moderate back-pressure was required to maintain a desired airspeed/pitch. The landing was relatively uneventful; however significantly more back-pressure than usual was required throughout the approach and rollout.Once on the ground; we attempted to cycle the trim and heard an audible sound when it got stuck. We had a CFI from the flight school come check the trim issue and confirm that the trim was getting stuck. The plane was subsequently grounded for maintenance. No damage or injury occurred during this incident.


Second narrative: I was a safety pilot for another PPL in a C172. We departed ZZZ on a flight to ZZZ1. On approach to ZZZ1; the pilot flying reported an issue with the elevator trim. He decided to continue flying with the trim in a full nose-down position. On final to ZZZ1 he reported needing heavy control pressures and asked me to hover the controls in case extra force was needed. We landed uneventfully. On the ground; we shut down and did two full cycles of the elevator trim and it appeared to be fully functional.We took off; on the climb the pilot reported needing extra control back pressure as he was unable to trim nose-up. He was able to trim correctly for the cruise and we opted to continue to ZZZ. This decision was made due to the aircraft being perfectly controllable in cruise and the availability of maintenance on the field.On approach to ZZZ; the trim would still not got back from a heavily nose-down position. On approach; I was needed to hover the controls. I did not have to apply extra-back pressure; but the PF (Pilot Flying) reported needing a heavily increased amount of back pressure. After landing two CFIs from the FBO tested the trim; confirmed an issue; and grounded the plane for maintenance. The elevator trim; when trimmed backwards; would audibly catch on something. The wheel could be moved further aft; but the actual tab would not move any further and the trim wheel would spring forward once pressure was released. It felt like the cable was catching on something and all turning the wheel further aft would do was stretch the elevator control cable.


Synopsis: C172 pilot and safety pilot reported the trim system was sticky inflight. After landing the system made an audible sound and became stuck.