Helicopter CFI reports a fixed wing aircraft landing under him as he transitions from autorotation to normal flight at an uncontrolled airport.

Narrative

The helicopter involved with CFI and student aboard conducted multiple traffic patterns to the active runway in order to familiarize the new student with the operation of the aircraft. Throughout the operations the CFI made routine and timely radio calls on the CTAF announcing all legs of the helicopters pattern; along with visually scanning for other traffic. On the second lap in the pattern the Instructor assumed the controls of the aircraft to demonstrate an autorotation to the student. Still; making timely radio calls in the pattern and visually scanning for other traffic the Instructor set the aircraft up at a safe altitude and speed to demonstrate the autorotation technique to the student. After announcing the turn to final; and visually checking for other traffic multiple times; the Instructor lined up with the runway and entered a controlled autorotation to a power recovery. At the end of the maneuver the Instructor re-applied power to the aircraft to enter a hover; while doing so noticed an aircraft rolling out on the runway directly underneath the helicopter after landing. Maximum power was immediately applied to the helicopter to initiate a climb-out. Neither the Instructor; or the commercial airplane rated student heard any radio calls from the other aircraft involved; nor did the FBO on the ground. Upon climb out the Instructor attempted to raise the other aircraft in question on CTAF; and was told the other aircraft 'did not see' the helicopter on final as it continued its approach. As the helicopter executed its go-around and subsequent approach the other aircraft in question transmitted that the helicopter's radio was 'unreadable.' Upon landing the Instructor aboard the helicopter requested a radio check from the airport's UNICOM services and was told the helicopter's radio was transmitting strong and clear. The sole cause of this incident was the airplane's lack of radio communications upon entering and progressing through its traffic patten at a non-controlled airport. Self-announcing one's pattern should be stressed when operating in a non ATC controlled traffic pattern. This potentially fatal incident would not have occurred if proper radio communications had been followed by both parties; not just one.