The FAA is adopting a new airworthiness directive (AD) for certain Sikorsky Aircraft Corporation Model S-76C helicopters. This AD was prompted by reports of inaccurate main gear box (MGB) indications in flight. This AD requires updating the remote data acquisition unit (RDAU) software and re-identifying the RDAU and, for certain helicopters, updating the software of the display unit (DU) and re-identifying the DU. The FAA is issuing this AD to address the unsafe condition on these products.