CS ACNS.D.AC.010 Transponder characteristics

ED Decision 2013/031/R

(See AMC1 ACNS.D.AC.010)

(a) The transponder is approved and has Mode A and Mode C capability.

(b) The transponder replies with Mode A and Mode C replies to Mode A/C interrogations, to Mode A/C-only all-call interrogations, and to Mode A/C/S all-call interrogations.

(c) The peak pulse power available at the antenna end of the transmission line of the transponder is more than 125 W (21 dBW) and not more than 500 W (27 dBW) for aircraft that operate at altitudes exceeding 4 570m (15 000 ft) or with a maximum cruising speed exceeding 90 m/s (175 knots).

(d) The peak pulse power available at the antenna end of the transmission line of the transponder is more than 70 W (18.5 dBW) and not more than 500 W (27 dBW) for aircraft operating at or below 4 570m (15 000 ft) with a maximum cruising airspeed of 90 m/s (175 knots) or less.

AMC1 ACNS.D.AC.010 Transponder characteristics 

ED Decision 2013/031/R

(a) Transponder capabilities.

(1) To be approved, the Mode A/C only transponder should hold an EASA equipment authorisation in accordance with European Technical Standard Order ETSO-C74d, or an equivalent standard that is consistent with ICAO Annex 10 Volume IV, and which is acceptable to EASA.

(2) The Mode A/C only transponder should be a class 2A / class 2B as defined in ETSO-C74d.

Note 1: ETSO-C74d Class 2 equipment meets EUROCAE Document 1/WG9 /71 June 1972 with amendment 1 and 2. Amendment 2 contains the requirements and tests to show that the transponder correctly replies to Mode A/C-only all call interrogations and to Mode A/C/S all-call interrogations used by Mode S radars.

Note 2: RTCA DO-144 does not include requirement to reply to Mode A/C/S All-Call and Mode A/C-Only All-Call interrogations and is, therefore, not sufficient to prove the compliance. RTCA DO-144A contains the requirements for the equipment to reply to Mode A/C/S All-Call and Mode A/C-Only All-Call interrogations.

(b) Minimum reply rate

(1) Mode A/C only transponders should be capable of continuously generating at least 500 replies per second for a 15-pulse coded reply.

(2) Transponder installations used solely below 4 500 m (15 000 ft), or below a lesser altitude established by the appropriate authority or by regional air navigation agreement, and in aircraft with a maximum cruising true airspeed not exceeding 90 m/s (175 knots) should be capable of generating at least 1 000 15-pulse coded replies per second for a duration of 0,1 s.

 Note: The rate of 1 000 replies per second for a limited duration of 100ms is an acceptable deviation to ETSO-C74d.

(3) Transponder installations operated above 4 500 m (15 000 ft) or in aircraft with a maximum cruising true airspeed in excess of 90 m/s (175 knots) should be capable of generating at least 1 200 15-pulse coded replies per second for a duration of 0,1 s.

 Note 1: A 15-pulse reply includes 2 framing pulses, 12 information pulses, and the SPI pulse.

 Note 2: The transponder should be capable of replying to this short-term burst rate, even though the transponder may not be capable of sustaining this rate.

 Note 3: The rate of 1 200 replies per second for a limited duration of 0,1 s is an acceptable deviation to ETSO-C74d.

(c) Minimum output power level

The transponder power output capability should be verified as follows depending on the aircraft capability:

(1) For aircraft that operate at altitudes exceeding 4 570 m (15 000 ft) or with maximum cruising speed exceeding 90 m/s (175 knots), the class of the transponder declared in the transponder DDP should be Class A.

(2) For aircraft operating at or below 4 570m (15 000 ft) with a maximum cruising airspeed of 90 m/s (175 knots) or less, the class of the transponder declared in the transponder DDP should be Class A or Class B.

CS ACNS.D.AC.015 Data transmission

ED Decision 2013/031/R

(See AMC1 ACNS.D.AC.015)

The surveillance system provides the following data in the replies:

(a) The Mode A identity code in the range 0000 to 7777 (Octal).

(b) The pressure altitude corresponding to within plus or minus 38.1 m (125 ft), on a 95 % probability basis, with the pressure-altitude information (referenced to the standard pressure setting of 1.01325 105 Pa),used on board the aircraft to adhere to the assigned flight profile. The pressure altitude ranges from minus 304 m (1 000 ft) to the maximum certificated altitude of aircraft plus 1520 m (5 000 ft).

(c) Special Position Indication (SPI) for 15 to 30 seconds after an IDENT (SPI) command has been initiated by the pilot.

AMC1 ACNS.D.AC.015 Data transmission

ED Decision 2013/031/R

(a) Mode A Code verifications.

(1) Set the Mode A code to 7776 (or other Mode A code agreed with the local Air Traffic Control Unit) through the dedicated flight crew interface. Confirm receipt of correct code by using ground test equipment.

(2) For dual transponder installation with a common control panel, set the Mode A code to 7776 (or other Mode A code agreed with the local Air Traffic Control Unit) and verify that the correct code is received by the ground test equipment. Switch to transponder 2 and verify that the correct Mode A code is received by the ground test equipment.

 Note: Agreement of Mode A code values is to be agreed with the local ATC if the transponder is in the visibility of an ATC cooperative surveillance system.

(b) Pressure Altitude verifications

(1) Verify that all Mode A/C transponders report the pressure-altitude encoded in the information pulses in Mode C replies.

 Note: more details on the encoding of the altitude can be found in ICAO Annex 10, Vol IV, para 3.1.2.6.5.4.

(2) Select the altitude switch to the ON position and verify that the transponder provides the current aircraft altitude in response to Mode C interrogations.

(3) A sufficient number of test points should be checked to ensure that the altitude reporting equipment and transponder perform their intended function through their entire range while ascending or descending. Where a Gillham altitude encoder is used, tests of each altitude code segment of the encoder (2300, 2500, 3800, 4300, 4800, 6800, 14800 30800, 70800, 90800, 110800 and 126700 if available) should be sufficient to ensure proper operation of each altitude code segment of the encoder.

CS ACNS.D.AC.020 Altitude source

ED Decision 2013/031/R

(See AMC1 ACNS.D.AC.020)

(a) The reported pressure altitude is obtained from an approved source.

(b) The altitude resolution is equal to or less than 30.48 m (100 ft.).

(c) The altitude source connected to the active transponder is the source being used to fly the aircraft.

AMC1 ACNS.D.AC.020 Altitude source

ED Decision 2013/031/R

(a) Altimeters compliant with JAA TGL No 6 are an approved and acceptable means of compliance for the altitude source.

(b) Altimeters with a pressure altitude resolution lower than or equal to 7,62 m (25 ft) is an approved and acceptable means of compliance.

Note: Altitude source resolution of 7,62 m (25 ft) or better is required for aeroplanes intended to be used for international air transport as defined in ICAO Annex 6 Part 1 — 6.19.

(c) An altimeter with a pressure altitude resolution lower than or equal to 30 m (100 ft) and greater than 7.62 m (25 ft) is an approved and acceptable means of compliance for aircraft provided that the flight deck interface provides a means to inhibit the transmission of pressure altitude information for aircraft equipped with Gillham encoded altitude

Note: It is not recommended to install altimeters with a Gillham altitude encoder interface.

(d) Manual or automatic selection of the altitude source are acceptable means of compliance

CS ACNS.D.AC.025 Flight deck interface

ED Decision 2013/031/R

(See AMC1 ACNS.D.AC.025)

A means is provided to:

(a) select Mode A Code including emergency indicators;

(b) initiate the IDENT (SPI) feature;

(c) notify the flight crew when the transmission of pressure altitude information has been inhibited if a means to inhibit the transmission of pressure altitude is provided;

(d) select the transponder to the ‘standby’ or ‘OFF’ condition;

(e) indicate the non-operational status or failure of the transponder system without undue delay and without the need for flight crew action;

(f) display the selected Mode A code to the flight crew; and

(g) select the pressure altitude source to be connected to the active transponder.

AMC1 ACNS.D.AC.025 Flight deck interface

ED Decision 2013/031/R

Modes of operation should be identified. Attention should be closely paid to line select keys, touch screens or cursor controlled trackballs as these can be susceptible to unintended mode selection resulting from their location in the flight deck.

Note: Systems not utilising Gillham interfaces may or may not provide a means to inhibit the transmission of pressure altitude.