As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
WHEN AIRCRAFT PICKED UP TO A HOVER, N2 NR 1 ENGINE DROPPED TO ZERO. FOUND GROUNDING STAR WASHER FELL OUT DURING INSTALLATION CAUSING GROUND TERMINAL TO HAVE AN INTERMITTENT GROUND. INSTRUCTED TECHNICIAN ON AN IMPROVED METHOD FOR INSTALLATION OF THIS STAR WASHER TO ASSURE IT REMAINS IN PLACE DURING INSTALLATION. REPAIRED TACH GENERATOR AND RETURNED TO SERVICE.