Airworthiness Directives; Dassault Model Falcon 2000EX and 900EX Series Airplanes

The FAA is adopting a new airworthiness directive (AD) for certain Dassault Model Falcon 2000EX and 900EX series airplanes. This AD requires prohibiting dispatch with certain equipment inoperative; and revising the airplane flight manual to facilitate recovery of the cockpit display units in the event of an avionics standard communication bus (ASCB) failure and to inform the flightcrew what equipment is inoperative during an ASCB failure. This AD also requires doing an integrity check of the ASCB for any faults and corrective action if necessary, and installing an avionics software update to the Honeywell Primus Epic system. This AD is prompted by a report that an analysis and tests of the Honeywell Primus Epic systems installed on the Model Falcon 2000EX and 900EX series airplanes revealed that all information displayed on the cockpit display units could become invalid during flight. We are issuing this AD to prevent a loss of data from all four of the cockpit display units, and loss of all radio communications (with the exception of VHF emergency frequency and last frequency used), primary navigation instruments, autopilot, auto- throttle, central alerting system, aural alarms, and normal braking (on Model Falcon 2000EX series airplanes only). These losses could reduce the flightcrew's situational awareness, increase flightcrew workload, and consequently reduce the ability to maintain safe flight and landing of the airplane.