GIV NOISE AND VIBRATION IN THE CABIN CHAFE INSPECTION revised 6/9/97 by Al Lane Not to he provided to operators. Inspection info is in ANINI Chapter 54 (Pylon Inspection) and Chapter 71 (Powerplant Inspection). This is a quick reference for GAC personnel to locate repair info. Noise and/or vibration in the cabin has been reported on several GIV aircraft. Several areas can provide paths for normal engine vibration/harmonics to bypass the engine isolators and go directly into the cabin. In the cabin, the vibration can be felt, or heard as "noise". In most cases, identifying and eliminating "noise paths" eliminates the annoying cabin noise. A thorough inspection and correction of "noise paths" will correct the majority of cabin noise problems. The majority of the identified noise paths are associated with the engine mounting and fixed cowl. The GIV has a new mounting design that incorporates a fixed cowl which is fixed to the thrust reverser and nose cowl versus the engine crane beams. This design allows the "Floating" fixed cowl to move with the engine. Due to the new GIV engine mounting design. contact between the fixed cowl and the shear web/crane beams must be prevented. The most common isolation factor used to determine if cabin noise is being generated by the engine or a foul between the engine and mounting is the EVM indication system. If EVM indication is present (above approximately 0.16 ips), then a fan balance would be the first item to be performed. If EVM indication is less than approximately 0.16 ips. then a chafe inspection would be the first item to be performed. In all cases, exact details on when and where the noise is occurring, engine parameters, engine EVM indications, flight profile and flight time, would supply the required information to start the resolution process. The following information has been assembled to help maintenance personnel locate and eliminate the most common noise paths. Additional information regarding