{"id":"F2007L02412","name":"AD/RAD/88 - Honeywell Communications and Mode S Transponder Units","slug":"ad-rad-88-honeywell-communications-and-mode-s-transponder-units","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":67829,"registerId":"commonwealth-F2007L02412-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"Radio Communication and Navigation Equip","sectionType":"division","heading":"Radio Communication and Navigation Equipment","content":"### Radio Communication and Navigation Equipment\n\n| AD/RAD/88 | Honeywell Communications andMode S Transponder Units | 10/2007 DM |\n| --------- | ---------------------------------------------------- | ---------- |\n\n```html\n

Applicability:

Honeywell RCZ-833J, RCZ-833K, RCZ-851J, RCZ-851K and RCZ-854J communications (COM) units and Honeywell XS-856A, XS-856B and XS-857A Mode S transponder units with the following part numbers (P/N):

Communications Unit

P/N

Mode S Transponder

P/N

RCZ-833J

RCZ-833K

RCZ-851J
RCZ-851K
RCZ-854J

7510700-763
7510700-863
7510700-765
7510700-875
7510700-813
7510700-815
7510700-725
7510700-825

XS-856A

XS-856B

XS-857A

7517400-865
7517400-885
7517400-866
7517400-886
7517400-876
7517400-896

Note 1: These units are known to be fitted to, but not limited to, the following aeroplane models:

Manufacturer

Model

British Aerospace
Bombardier
Cessna
Dassault
Embraer
Learjet
Lockheed
Raytheon

Jetstream 4100 series
BD-700-1A10 and BD-700-1A11
525, 550, 560 and 650 series
Falcon 900EX and 2000EX series
EMB-135 and EMB-145 series
45
282-44A-05 (C130B) and 382G series
Hawker 800 (including U-125A), 800XP and 1000 series

Requirement:

1. For aircraft equipped with Honeywell RCZ-833J, RCZ-833K, RCZ-851J,
RCZ-851K or RCZ-854J COM units, with P/Ns listed in the applicability section of this Directive:

a. If not previously accomplished in accordance with AD/RAD/84 - Amend the applicable Aircraft Flight Manual (AFM) by inserting the following statement into the Normal Procedures Section:

“After completion of any 4096 ATC Code change (also referred to as Mode A Code), check the status of the transponder. If the transponder indicates that it is in standby mode, re-select the desired mode (i.e. the transponder should be in the active mode).”

Amendment of the AFM Normal Procedures Section may be accomplished by inserting a copy of this Directive into the AFM.

b. If not previously accomplished in accordance with AD/RAD/84 - Modify the COM unit by incorporating Honeywell Service Bulletin (SB) Publication No A21-3851-005 dated 29 July 2005 or Honeywell SB Publication No
A24-3851-002 dated 28 July 2005 as applicable.

Note 2: Accomplishment of the modification or replacement with a modified unit in accordance with the instructions contained in Honeywell Alert Service Bulletin (ASB) 7510700-23-A0048 dated 27 January 2006 and, as necessary, ASB
7517400-23-A6015 Revision 001 dated 29 July 2005 is an acceptable alternative to the Requirement1.b.modification.

c. Replace the XS-852E/F Mode S transponder of the COM unit with a new or modified XS-852E/F Mode S transponder that has MOD V installed, in accordance with Honeywell Alert Service Bulletin 7510700-23-A0047 Revision 001, dated July 29, 2005.

2. For aircraft equipped with Honeywell XS-856A, XS-856B or XS-857A Mode S Transponder Units, with P/Ns listed in the applicability section of this Directive:

a. Unless already accomplished in accordance with Requirement 1.a. - Amend the applicable Aircraft Flight Manual (AFM) by inserting the following statement into the Normal Procedures Section:

“After completion of any 4096 ATC Code change (also referred to as Mode A Code), check the status of the transponder. If the transponder indicates that it is in standby mode, re-select the desired mode (i.e. the transponder should be in the active mode).”

Amendment of the AFM Normal Procedures Section may be accomplished by inserting a copy of this Directive into the AFM.

b. Unless already accomplished, replace the modification plate of the transponder with a new plate and test the transponder, in accordance with the Accomplishment Instructions of Honeywell ASB 7517400-23-A0017, dated 23 January 2006.

c. If the transponder fails the test specified in Requirement 2.b., install MOD Y into the transponder as specified in Requirement 2.d.

\n```\n\n| | d. Install MOD Y into the applicable Mode S transponder, in accordance with the Accomplishment Instructions of Honeywell ASB 7517400-23-A6016, dated 30 August 2005. |\n| ----------- | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |\n| | 3. Remove the AFM amendment inserted in compliance with either Requirement 1.a. or 2.a. |\n| | 4. COM units and Mode S Transponder units with P/Ns listed in the applicability section of this Directive may not be may not be installed on any aircraft, as a replacement spare, unless the applicable software modification has been installed in the transponder in accordance with Requirements 1.c. or 2.d. |\n| | Note 3: FAA AD 2006-19-04 Amdt 39-14761 and EASA AD 2007-0156, corrected 14 June 2007, refer. |\n| Compliance: | For Requirement 1.a. - Within 10 days after the effective date of this Directive. |\n| | For Requirement 1.b. - Within 30 days after the effective date of this Directive. |\n| | For Requirement 1.c. - Concurrent with the modification or replacement in accordance with Requirement 1.b., but no later than nine months after the effective date of this Directive. |\n| | For Requirement 2.a. - Within 10 days after the effective date of this Directive. |\n| | For Requirement 2.b. - Within nine months after the effective date of this Directive. |\n| | For Requirement 2.c - Before further flight after the test specified in Requirement 2.b. |\n| | For Requirement 2.d. - Before or concurrent with Requirement 2.a. |\n| | For Requirement 3 - After accomplishing the replacements or modifications specified in Requirements 1.b., 1.c., 2.b. and 2.d. |\n| | For Requirement 4 - As of the effective date of this Directive. |\n| | This Airworthiness Directive becomes effective on 8 August 2007. |\n| 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. |\n\n| | 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. |\n| --- | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |\n| | 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. |\n\n![](image.001.png) \nDavid Punshon \nDelegate of the Civil Aviation Safety Authority\n\n31 July 2007","sortOrder":0},{"sectionNumber":"AD/RAD/88","sectionType":"part","heading":"AD/RAD/88","content":"## AD/RAD/88","sortOrder":1},{"sectionNumber":"Honeywell Communications andMode S Trans","sectionType":"part","heading":"Honeywell Communications andMode S Transponder Units","content":"## Honeywell Communications and \nMode S Transponder Units","sortOrder":2},{"sectionNumber":"10/2007 DM","sectionType":"part","heading":"10/2007 DM","content":"## 10/2007 DM","sortOrder":3}],"analysis":{"flash_summary_failed":{"failed":true,"reason":"A positive credit balance is required for all requests, including BYOK, so fallback providers remain available. Add credits at https://vercel.com/d?to=%2F%5Bteam%5D%2F%7E%2Fai%3Fmodal%3Dtop-up to continue.","source":"analysis-cron"},"flash_summary":{"complexity_score":6,"scope_assessment":{"changed":true,"description":"This Directive supersedes AD/RAD/84 and expands its scope: it retains AFM amendments and COM unit modifications from the earlier Directive but adds mandatory modification or replacement requirements specifically for associated Mode S transponders and prohibits fitting listed P/Ns as unmodified replacement spares (see Background and Requirements 1–4)."},"complexity_factors":["Multiple affected part numbers and equipment types across COM units and separate Mode S transponders (see Applicability table and Requirements 1 and 2).","Different corrective paths depending on equipment: AFM amendment, COM unit software/modification, transponder MOD V or MOD Y, or unit replacement (Requirements 1.a–1.c; 2.a–2.d).","Cross‑references to earlier AD/RAD/84 and multiple Honeywell Service Bulletins and Alert Service Bulletins as normative compliance methods (Notes and Requirement text).","Staged and varied compliance windows (10 days, 30 days, 9 months, before further flight, and concurrent timing obligations).","Operational constraint banning installation of listed P/Ns as spare parts unless modified (Requirement 4), affecting supply chains and spares inventory management.","Technical testing requirement for transponders and conditional requirement to install MOD Y if tests fail (Requirement 2.b–2.c), creating workload for maintenance organisations.","Regulatory coordination with FAA and EASA directives cited (Note 3), adding layers for international operators and imported parts compliance."],"plain_english_summary":"This Airworthiness Directive requires operators of aircraft fitted with certain Honeywell communications (COM) units and Mode S transponders to amend their Aircraft Flight Manual and to carry out software/hardware modifications or replace transponders so they do not revert to standby after a 4096 ATC code change. It affects listed aircraft models, owners, and maintenance providers, imposing short compliance windows and a ban on installing unmodified spare units because the defect can remove the aircraft from ATC radar and impair collision‑avoidance systems."},"kimi_summary":{"content_quality":"ok","complexity_score":4,"scope_assessment":{"changed":false,"description":"This directive maintains its original scope as a targeted safety fix for specific Honeywell avionics. It supersedes AD/RAD/84 but explicitly continues that directive's requirements while adding transponder modifications. The scope has not expanded beyond addressing the specific 5-second timeout design deficiency in the identified equipment."},"complexity_factors":["Multiple interdependent requirements with cross-references (Requirements 1.a through 2.d reference each other with 'unless already accomplished' and 'concurrent with' conditions)","Nested conditional logic: Requirement 2.c only triggers if 2.b test fails; Requirement 3 only applies after completing multiple prior requirements","Dual equipment tracks with slightly different modification paths for COM units versus standalone transponders","Extensive part number specificity: 8 communication unit part numbers and 6 transponder part numbers listed in applicability table","Multiple acceptable compliance methods referencing external Honeywell Service Bulletins (4 different SB/ASB documents cited)","Staggered compliance deadlines ranging from 10 days to 9 months depending on specific requirement","Supersedes prior directive AD/RAD/84 while maintaining some of its requirements, creating historical dependency"],"plain_english_summary":"This CASA Airworthiness Directive mandates fixes for a Honeywell comms/transponder software bug that can silently drop the transponder to standby if a pilot doesn’t complete a 4‑digit squawk change within 5 seconds, risking loss of radar/identification and collision‑avoidance functionality. It applies to many business and regional aircraft fitted with affected Honeywell units.\n\nOperators must issue a temporary AFM warning, update or replace affected units with corrected software, and stop installing unmodified spares until compliance — then remove the temporary warning."}},"importantCases":[],"_links":{"self":"/api/acts/ad-rad-88-honeywell-communications-and-mode-s-transponder-units","history":"/api/acts/ad-rad-88-honeywell-communications-and-mode-s-transponder-units/history","analysis":"/api/acts/ad-rad-88-honeywell-communications-and-mode-s-transponder-units/analysis","conflicts":"/api/acts/ad-rad-88-honeywell-communications-and-mode-s-transponder-units/conflicts","importantCases":"/api/acts/ad-rad-88-honeywell-communications-and-mode-s-transponder-units/important-cases","documents":"/api/acts/ad-rad-88-honeywell-communications-and-mode-s-transponder-units/documents"}}