What was found
COMPLETE VACUUM SYSTEM FAILURE, BOTH NORMAL SYSTEM AND STANDBY SYSTEM. THE FAILURE WAS CAUSED BY DETERIORATION OF VACUUM HOSES. HOSES TO THE ATTITUDE INDICATOR AND DIRECTIONAL GYRO WERE SO BRITTLE THAT BENDING THE NOSE WOULD RESULT IN COMPLETE BREAK-UP, AND FLAKING OF THE HOSE. INSPECTION OF THREE OTHER 172'S OF THIS MODEL REVEALED THE IDENTICAL CONDITION OF VACUUM HOSES. REVIEW OF MAINTENANCE RECORDS REVEALED THAT THESE HOSES HAD NEVER BEEN REPLACED AND WERE APPARENTLY INSTALLED AT THE DATE OF MANUFACTURE - 1978.