Aeronca Chief aircraft flight instructor with student reported the aircraft ground looped upon landing with the student at the controls. The instructor attempted to take control of the aircraft but was too late. The aircraft incurred damage as it hit a runway sign.

Narrative

Was providing instruction to new student in an Aeronca Chief. I as the instructor was sitting in the left seat which is the only seat with brakes and the student was in the right seat. We were practicing taxing on the runway as it was a slow day and practicing the skills to control the tail dragger while on the ground. We were practicing brining the tail up and down; one of the most critical phases in controlling a tailwheel plane. The student brought the tail down and the plane instantly turned to the left. I attempted to use right brake/rudder and pulled the power to idle in order to straighten the plane but it was too late and the momentum of the aft CG in the Chief took it left and the plane came in contact with a Runway Feet Remaining sign. The impact with the sign caused damage to the landing gear; wing strut and wooden propeller. The plane has a continental 65hp engine and continental does not have an AD requiring an engine inspection if damage is done to a wooden prop; so the engine remains in good condition. Taildraggers are fundamentally known to be difficult to control on the ground. We were practicing this and the plane became uncontrollable within a matter of a second. By the time I could recognize the plane was headed left my efforts to correct the plane were too late. The biggest contributing factor was the student being new to tailwheel type airplanes and the quickness in which a taildragger can lose controllability.