Flight Crew Commercial; Flight Crew Instrument
Flight Crew Last 90 Days 1.5; Flight Crew Total 1060; Flight Crew Type 750
Time Pressure; Training / Qualification
Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural Clearance
Flight Crew Landed in Emergency Condition
Aircraft
I was flying with a CFII doing a bi-annual on a RR (Round-Robin) between ZZZ and ZZZ1. We departed ZZZ1 flying direct to ZZZ at 1700 foot. Note that we departed ZZZ with 3.5 hours of fuel. Shortly before the midpoint of the return leg the engine suddenly/instantaneously was running rough. The CFII immediately asked for the controls and I granted them. We tried carb heat; switched the mags. The engine continued to run with a max RPM estimated at 1200. Applying throttle would cause the engine to immediately lose RPM and begin windmilling. We were in a rural area with no close airports and the CFII made the correct decision to set the plane down instead of trying to nurse an engine with 1/4 power. We had a few field options; chose one and set down with no issues for the passengers or aircraft.
C172 pilot reported engine operating at low power resulted in an off airport landing.