COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY
SCHEDULE OF AIRWORTHINESS DIRECTIVES
Bell Helicopter Textron 412 Series Helicopters
AD/BELL 412/19 Emergency DC Bus Number One Feeder Circuit 3/88
Applicability: All model Bell 412 and 412NB helicopters S/No 33108 to 33139 inclusive, and 33150 to 33154 inclusive.
Requirement: Action in accordance with Bell ASB 412-87-33 dated 1 December 1987.
Compliance: Within 100 hours time in service after 24 March 1988, or at the next scheduled inspection for Maintenance Release issue after 24 March 1988 whichever is the latter.
Background: Bell have advised that Model 412 emergency and essential buses are configured such that a short circuit on essential bus number 2 will cause both emergency bus 50 amp feeder circuit breakers to open thus removing all power from the emergency bus.