COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 - 105 CIVIL AVIATION SAFETY AUTHORITY SCHEDULE OF AIRWORTHINESS DIRECTIVES Bell Helicopter Textron Canada (BHTC) 407 Series Helicopters AD/BELL 407/2 Warning Horns 5/99 Applicability: Model 407 helicopters with Serial Numbers 53000 through 53194 inclusive. Requirement: If not previously accomplished, replace the existing 'FADEC FAIL', 'ENGINE OUT' and 'LOW ROTOR RPM' warning horns with new horns having Part Numbers VSB628CP, SC628NP and SC628N respectively. Replacement of the horns is to be accomplished in accordance with Bell Helicopter Textron Canada Alert Service Bulletin No 407-97-12 dated 7 October 1997. Note: Transport Canada AD CF-98-13 refers. Compliance: Prior to 20 July 1999. This Airworthiness Directive becomes effective on 20 May 1999. Background: Transport Canada Aviation has advised that analysis of engine failures with this helicopter have shown a need for the sound of the 'FADEC FAIL' horn to be distinct and for the 'ENGINE OUT' and 'LOW ROTOR RPM' warning horns to be louder. This Directive facilitates appropriate flight crew reactions to in-flight emergencies by providing more distinct and conspicuous warnings.