AIRWORTHINESS DIRECTIVE
For the reasons set out in the background section, the CASA delegate whose signature appears below issues the following Airworthiness Directive (AD) under subregulation 39.1 (1) of CAR 1998. The AD requires that the action set out in the requirement section (being action that the delegate considers necessary to correct the unsafe condition) be taken in relation to the aircraft or aeronautical product mentioned in the applicability section: (a) in the circumstances mentioned in the requirement section; and (b) in accordance with the instructions set out in the requirement section; and (c) at the time mentioned in the compliance section.
Aircraft - General
AD/GENERAL/83 Rockwell Collins 621A-3 Transponders 5/2002
Applicability: Transport Category aeroplanes equipped with Rockwell Collins Mode C 621A-3 Air Traffic Control (ATC) transponders, part number (P/N) 522-2703-XXX (where XXX is any series number).
Requirement: 1. Perform a pulse width test to detect malfunctions of any Mode C 621A-3 ATC transponder(s) P/N 522-2703-XXX, where XXX is any part number, in accordance with Rockwell Collins Air Transport Systems Overhaul Manual with Illustrated Parts List, Temporary Revision No. 34-44-00-38, dated 20 April 2000.
Note 1: Pulse width tests done using TIC-49, ATC-601, ATC-601A, or ATC-1400A ramp or bench testers meet the applicable test requirements in Requirement 1 or 2.
Note 2: Previous checks used to perform the test specified in Requirement 1, per Rockwell Collins Air Transport Systems Overhaul Manual with Illustrated Parts List, Temporary Revision No. 34-44-00-38, dated 20 April 2000, are acceptable for compliance with Requirement 1.
2. If the Requirement 1 pulse width test detects malfunction of a transponder, carry out the following, as applicable, in accordance with Rockwell Collins Service Bulletin 621A-3-34-21, Revision 1, dated 14 November 1975:
- For transponders having serial numbers up to and including 7192 - Replace the transmitter tube and resistor with a new tube and resistor and repeat the Requirement 1 pulse width test.
b. For transponders having serial numbers 7193 and subsequent - Replace the transmitter tube with a new tube and repeat the Requirement 1 pulse width test.
Accomplishment, prior to the effective date of this Directive, of the replacement specified in Requirement 2.a. or 2.b, as applicable, in accordance with Rockwell Collins Service Information Letter (SIL) 00-1 dated 25 May 2000 is considered acceptable for compliance with Requirement 2.a. or 2.b.
Aircraft - General
AD/GENERAL/83 (Continued)
3. If the follow-up pulse width test required by Requirement 2 detects malfunction of a transponder, repair the transponder in accordance with the applicable Mode C transponder component maintenance manual and aeroplane maintenance manual.
Note 3: The aeroplane may be operated in accordance with the provisions and limitations specified in the approved Master Minimum Equipment List (MMEL), provided that only one Mode C transponder on the airplane is inoperative.
Note 4: FAA AD 2002-06-05 Amdt 39-12682 refers.
Compliance: For Requirement 1 - Within 6 months after the effective date of this Directive.
For Requirement 2 - Before further flight. For Requirement 3 - Before further flight.
This Airworthiness Directive becomes effective on 16 May 2002.
Background: This Directive requires testing each transponder; replacing certain parts in any transponder that fails the initial test with new parts and performing additional test(s); and making repairs, as necessary, so that the transponder passes the test. The issue of the Directive results from reports that indicate that the equipment used to conduct earlier tests of certain transponders did not detect certain malfunctions.
An aeroplane equipped with such malfunctioning transponders could transmit inaccurate data concerning its altitude to a nearby aeroplane equipped with the traffic alert and collision avoidance system (TCAS II), causing the TCAS II to issue an erroneous resolution advisory to the pilot. The actions required by this Directive are intended to prevent transmission of inaccurate data concerning altitude from one airplane to another, which could cause the pilot receiving the data to change course, either ascending or descending, and possibly lead to a mid-air collision or near mid- air collision.
Eugene Paul Holzapfel
Delegate of the Civil Aviation Safety Authority 4 April 2002
The above AD is notified in the Commonwealth of Australia Gazette on 24 April 2002.