What was found
ELEVATOR FLUTTER CAUSED MULTIPLE FRACTURES AND DELAMINATIONS IN ELEVATOR SKINS INCLUDING SEPARATION OF INBOARD HINGES ON HORIZONTAL STABILIZER. PILOT REPORTED A VIBRATION AT 120 KTS AND 10,000 FEET IN SMOOTH AIR. REDLINE AT 10,000 FEET IS 128 KTS. POST-INSPECTION OF ELEVATOR BALANCE SUGGESTS THAT SPECIFICATIONS IN MM TO BE INACCURATE AND/OR INADEQUATE. ELEVATOR BY DESIGN HAS NO COUNTERWEIGHTS INSTALLED. OTHER CASES OF FLUTTER ON THIS MODEL GROB HAVE BEEN REPORTED.