AMC1 ACNS.A.GEN.010 Instructions for Continued Airworthiness

ED Decision 2013/031/R

(a)     Transponder testing

The Instructions for Continued Airworthiness should include the following measures and precautions in order to minimise the possibility of causing nuisance warnings to ACAS equipped aircraft.

(1)     When not required, ensure all transponders are selected to ‘OFF‘ or ‘Standby‘.

(2)     Before starting any test, contact the local Air Traffic Control Unit and advise them of your intention to conduct transponder testing. Advise the Air Traffic Unit of your start time and test duration. Also inform them of the altitude(s) at which you will be testing, your intended Aircraft Identification (Flight Id) and your intended Mode A code. 

         Note: Certain altitudes may not be possible due to over flying aircraft.

(3)     Set the Mode A code to 7776 (or other Mode A code agreed with Air Traffic Control Unit).

         Note: The Mode A code 7776 is reserved for SSR ground transponder monitoring. This code may be used for transponder testing after having received agreement from the Air Traffic Control Unit.

(4)     Set the Aircraft Identification (Flight Id) with the first 8 characters of the company name. This is the name of the company conducting the tests.

(5)     Set the on-the-ground status for all Mode S replies, except when an airborne reply is required (e.g. for altitude testing).

(6)     Where possible, perform the testing inside a hangar to take advantage of any shielding properties it may provide.

(7)     As a precaution, use antenna transmission covers whether or not testing is performed inside or outside.

(8)     When testing the altitude (Mode C or S) parameter, radiate directly into the ramp test set via the prescribed attenuator.

(9)     In between testing, i.e., to transition from one altitude to another, select the transponder to ‘standby’ mode.

(10)    If testing transponder parameters other than ‘altitude‘, set altitude to minus 300 m (minus 1 000 feet) or over 18 250 m (60 000 feet). This will minimise the possibility of ACAS warning to airfield and overflying aircraft.

(11)    When testing is complete, select the transponder(s) to ‘OFF‘ or ‘Standby’.

(b)     Reduced Vertical Separation Minima

When developing the instructions for continued airworthiness, attention should be given to the following items:

(1)     All RVSM equipment should be maintained in accordance with the component manufacturers' maintenance instructions and the performance criteria of the RVSM approval data package.

(2)     Any repairs, not covered by approved maintenance documents, that may affect the integrity and accuracy of the altimeter system , e.g. those affecting the alignment of pitot/static probes, repairs to dents or deformation around static plates should be subject to a design review which is acceptable to the competent authority.

(3)     Airframe geometry or skin waviness checks should be performed following repairs or alterations which have an effect on airframe surface and airflow.

(4)     The maintenance and inspection programme for the autopilot should ensure continued accuracy and integrity of the automatic altitude control system.