The flight instructor was demonstrating a landing using the manual Full-Authority Digital Engine Control (FADEC) mode. While on short final, approximately 3 to 5 feet above ground level, the helicopter quickly descended right and forward. Suspecting wind shear, the flight instructor applied corrective controls, but was unable to reverse the downward motion prior to ground contact. The helicopter's left rear skid contacted the ground followed by the right rear skid before the flight instructor could bring the helicopter back to a hover. A post-flight examination of the helicopter revealed damage to the vertical stabilizer and tail boom.