PA-34 Seneca Undifferentiated
Flight Crew Instrument; Flight Crew Commercial
Flight Crew Last 90 Days 15; Flight Crew Total 660; Flight Crew Type 20
Situational Awareness; Troubleshooting; Time Pressure; Distraction
Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Maintenance; Inflight Event / Encounter Unstabilized Approach
Flight Crew Returned To Departure Airport; Flight Crew Landed As Precaution; General Maintenance Action
Aircraft
I am a single engine commercial pilot but was taking multi-engine lessons from a local flight school located at ZZZ. We departed ZZZ and landed at ZZZ1 airport to practice a short field landing. After making an uneventful landing I taxied back and took off again. Everything was normal until we reached roughly 400 ft AGL. The aircraft yawed and rolled left so we immediately assumed we lost or was losing the left engine. My flight instructor took over flying the aircraft at this point. He started turning back to the airport. At this point I told him that the left engine was showing about 1700 RPMs. He decided to leave the engine running but partially feather it because it may still be providing some thrust. We flew back to make the approach and he gave controls back to me to make the landing. We were high and fast on final approach so I lowered the gear and put in all of the flaps to get us down and slowed. We were not coming down or slowing as desired so I brought the engines to idle and heard the right engine come down to idle but could hear the left engine was way above idle. I noted that the left engine was still at 1700 RPM even though the throttles were at idle. At this point we were crossing the numbers fast. I landed the airplane but due to the excessive speed I nearly did not make the last turnoff of the runway. We taxied back to the parking area and shutdown. We called the flight school and a mechanic was flown to our location to inspect and/or repair the airplane. After pulling the cowling from the airplane he made a statement to the effect that 'Oh; I guess I forgot the safety wire on the clip when I changed the throttle cables last week'.
Piper Seneca pilot reported a throttle control problem resulted in a partial-throttle precautionary landing.