Robinson R44
Flight Crew Flight Instructor; Flight Crew Commercial; Flight Crew Instrument; Flight Crew Rotorcraft
Flight Crew Last 90 Days 90; Flight Crew Total 1450; Flight Crew Type 415
Aircraft Equipment Problem Critical
Flight Crew Landed As Precaution; Flight Crew Took Evasive Action
Aircraft
While transitioning back to [departure airport]; the engine started making a loud banging noise. I scanned the instrument cluster and saw the RPM's surging and manifold pressure spiking. I decided that we could not make it back to [departure airport] and lowered collective and picked a field to land in to check it out. I make an expeditious descent and land with power at the bottom with no other damage to the helicopter. Upon landing I saw white smoke coming from behind us; so I told my student to get out and see if we are on fire as I rapidly shut down the helicopter and pull fuel. There was no fire; just smoke from oil burning on the muffler.
R44 Instructor reported a precautionary landing in a field due to power fluctuations.