Document ID: chunk:federal_register_of_legislation:F2007L02412:body:0:p3
Version: federal_register_of_legislation:F2007L02412
Segment Type: other
Provision Reference: 
Character Range: 11436–13245

this Directive.
             For Requirement 2.b. - Within nine months after the effective date of this Directive.
             For Requirement 2.c - Before further flight after the test specified in Requirement 2.b.
             For Requirement 2.d. - Before or concurrent with Requirement 2.a.
             For Requirement 3 - After accomplishing the replacements or modifications specified in Requirements 1.b., 1.c., 2.b. and 2.d.
             For Requirement 4 - As of the effective date of this Directive.
             This Airworthiness Directive becomes effective on 8 August 2007.
Background:  Both the United States Federal Aviation Administration (FAA) and the European Aviation Safety Agency (EASA) has advised of a design deficiency which causes the transponder to revert to standby mode if a change of the 4096 ATC code (also referred to as the Mode A code) is not completed within 5 seconds.

   As a consequence, the Secondary Surveillance Radar (SSR) symbol and label associated with the aircraft's position will no longer be shown on the Air Traffic Control (ATC) ground radar display.  Also, aircraft collision avoidance systems (ACAS) on board own and other aircraft will be compromised.  Current operational procedures, typically, do not require the crew to recheck the transponder status after changing the 4096 ATC Code.  This type of failure will increase ATC workload and will result in improper functioning of ACAS.
   AD/RAD/84, which was based on EASA AD 2005-0021, required the amendment of the AFM and modification of the COM unit.  This Directive supersedes AD/RAD/84 and, whilst continuing the requirements of that Directive, also requires the modification of associated Mode s transponders.

David Punshon
Delegate of the Civil Aviation Safety Authority

31 July 2007