Date: 202012
Local time of day: 1201-1800
Location: ZZZ.Tower, US
Flight conditions: VMC
Weather elements / visibility: 10
Light: Daylight
Aircraft: Skyhawk 172/Cutlass 172
Operator: Other Flight School
Operating under: Part 91
Flight plan: None
Mission: Training
Flight phase: Cruise
Airspace: Class D ZZZ
ATC / advisory: Tower ZZZ
Aircraft component: Throttle/Power Lever
Component problem: Malfunctioning
Reporter organization: Personal
Reporter function: Instructor; Pilot Flying
Reporter qualification: Flight Crew Instrument; Flight Crew Flight Instructor; Flight Crew Commercial; Flight Crew Multiengine
Human factors: Workload; Training / Qualification; Human-Machine Interface; Distraction; Situational Awareness
Anomaly: Aircraft Equipment Problem Critical
Detector: Person Flight Crew
When detected: In-flight
Result: Flight Crew Returned To Departure Airport; Flight Crew Landed in Emergency Condition
Contributing factors: Aircraft
Primary problem: Aircraft

Narrative: Myself and my student departed ZZZ VFR to the east on [Date] at approximately XA:30 local time for a routine instrument training flight. We took Aircraft X which had been flown twice that day already with no issues. The preflight was normal; and run-up was normal. We found no indication of a potential malfunction. We had been maneuvering for approximately 15 minutes in the east practice area when [Student] began to make an altitude correction from 3;700 ft. MSL to 3;500 ft. MSL. He attempted to take out some power; but when he reduced the throttle towards the idle position there was no RPM change indicated. He stopped reducing the throttle when he noticed it was pulling out farther than he had ever seen it go before. With concern that the throttle may not be secured properly now; I moved the throttle to the full open position; then moved slightly toward the aft position (approx. 1/2 inch reduction). This reduction was successful and the power reduced to 2400 RPM. With power still being available; I took the flight controls via a positive three-way exchange; turned direct ZZZ visually immediately; called the tower; for partial engine failure. We were 10 miles due east of ZZZ at this time. I selected a field for a forced landing in case that became necessary; and as we got closer to ZZZ I verbally selected another field; and then finally a grass strip just [southeast] of ZZZ before I had ZZZ ensured.I requested to stay at 3;500 ft. MSL (or at least high enough to ensure gliding distance to XXL-the runway I wanted and later requested) and enter the pattern possibly that high. I reported two miles east of the field; got cleared to land; and once I had the runway ensured; I began to reduce the throttle. I remember only trying to reduce about 300-400 RPM; but the power went from 2400 RPM to 1300 RPM. I then put the throttle to the fully open position. At full open; the RPM indication was still 1300. I told the tower I was now in a full engine-out situation. I was approximately 1 to 1.5 nm [northeast] of the approach end of [Runway] XXL when the full failure happened. After getting lined up on final; I reduced the throttle to idle (I did not want a resurgence of power at an unexpected time) and did not attempt a restart. I had [Runway] XXL ensured; and I knew the best option was to commit to the forced landing on a large; paved runway rather than risk restarting an engine that may just die again. On final; [Student] opened his door to ensure at least one safe exit. I glided into [Runway] XXL and maintained positive aircraft control with a smooth touchdown. I did have to perform a forward slip with full flaps to ensure touchdown in the first 3rd of the runway- I recommend the flaps be inspected. I had enough energy to roll off on Taxiway Bravo; clear of [Runway] XXL. We then exited the aircraft and waited for a tow. [Student] told me once we were on the ground that he noticed the fuel flow was indicating 0 while I was on short final just after I had declared the full engine out. He said nothing else caught his eye during those seconds. He was trying to study the MVP50 [Electronic Engine Monitor] for any possible explanation as to the cause of the failure while I was flying.




Synopsis: Flight Instructor flying C-172 aircraft reported engine failure inflight.