Summary
We propose to adopt a new airworthiness directive (AD) for Eurocopter Model SA-365N1, AS-365N2, and AS365N3 helicopters. This proposed AD would revise the Limitations section of the Rotorcraft Flight Manual (RFM) to prohibit flight in instrument meteorological conditions (IMC) or night visual flight rules (VFR) for each helicopter with a vertical gyro unit GV76-1 installed upon a non-reinforced shelf in the rear cargo compartment. Also, this proposed AD would require modifying the GV76-1 vertical gyro unit shelf and testing for correct function of the navigation systems. This proposed AD is prompted by flight crew reports of deviations between the displayed attitude on the attitude display screen and the independent electromechanical standby attitude indicator. The proposed actions are intended to prevent an undetected flight display error of a slow drift in the roll axis, disorientation of the pilot, and subsequent loss of control of the helicopter.