Flight Crew Rotorcraft; Flight Crew Instrument; Flight Crew Air Transport Pilot (ATP); Flight Crew Flight Instructor
Flight Crew Last 90 Days 123; Flight Crew Total 3059; Flight Crew Type 2940
Training / Qualification
Aircraft Equipment Problem Critical
Aircraft Aircraft Damaged; Flight Crew Landed As Precaution
Aircraft
The purpose of the flight described here was an IFR flight lesson. Only my student pilot (PPL helicopter) and myself were on-board the Robinson R44 Raven 2 helicopter. We were planning to fly for about 90 min and had about 40 gal of fuel on board. Our combined weight is about 350 pounds and our weight and balance indicated that we were well within the approved limits at all times from takeoff until landing. Weather was VFR.A few minutes after a normal take-off from ZZZ; we experienced a 'low RPM' warning signal. Proper corrective action was immediately taken to remedy this (lower collective and roll on throttle) and since nothing else indicated any type of malfunction; I thought that we had a possible slow response of the governor to a light turbulence we had just flown through. About a minute after this first event; we experienced another similar 'low RPM'. At this point we decided to turn around and go back to ZZZ (we were about 6 miles away from the airport). From that point on; it turned out that the only way to keep 100% RPM was by keeping our collective low; which resulted in a slow loss of altitude. All engine gauges indicated normal operation (i.e.; in the green range) and the manifold pressure indicated about 20 inch of Hg. However; any attempt to regain altitude by raising collective resulted in low RPM (engine was unable to deliver more power). As a precautionary maneuver; we landed on the first open field and shut down the engine immediately after touch down (we noticed smoke emanating from the engine as we landed). We landed smoothly on a grass field and neither the student-pilot nor I were injured; and no damage was caused to the aircraft (except for the engine reduced capability to deliver power). I did not declare emergency as our precautionary landing turned out to be the right decision before an emergency maneuver would have been required if we had continued to fly. Our mechanic is checking the engine and; if required; we can report on the exact problem that has occurred.
R44 Helicopter Instructor reported a precautionary landing in a field due to a loss of RPM.