{"id":"F2006L02986","name":"AD/B737/293 - Master Dim and Test System Wiring","slug":"ad-b737-293-master-dim-and-test-system-wiring","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":60265,"registerId":"commonwealth-F2006L02986-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"Boeing 737 Series Aeroplanes","sectionType":"division","heading":"Boeing 737 Series Aeroplanes","content":"### Boeing 737 Series Aeroplanes\n\n| AD/B737/293 | Master Dim and Test System Wiring | 10/2006 |\n| ----------- | --------------------------------- | ------- |\n\n```html\n

Applicability:

Model 737-300, -400 and -500 series aeroplanes identified in Boeing Special Attention Service Bulletin (SB) 737-33-1132, Revision 2, dated 8 September 2005; and Model 737-600, -700, -700C, -800 and -900 series aeroplanes identified in Boeing SB 737-33-1133, Revision 3, dated 8 September 2005.

Requirement:

1. Modify the wiring for the master dim test system in accordance with the Accomplishment Instructions of Special Attention SB 737-33-1132, Revision 2 (for Model 737-300, -400 and -500 series aeroplanes) and SB 737-33-1133, Revision 3 (for Model 737-600, -700, -700C, -800 and -900 series aeroplanes), as applicable.

2. Accomplish the prior or concurrent actions specified in Table 1, as applicable.

Table 1 - Prior and/or Concurrent Actions

For:

Accomplish all actions associated with:

According to the Accomplishment Instructions of:

Group 57 aeroplanes identified in Special Attention SB 737-33-1132, Revision 2

Installing an engine instrument system (EIS), and

Boeing SB 737-77-1022, Revision 1, dated 26 October 1989

Modifying the advisory system for the EIS

Boeing SB 737-77-1023, Revision 1, dated 9 November 1989

Group 37 and 46 aeroplanes identified in SB 737-33-1133, Revision 3

Installing wiring for the test system for the audio control panel lamp

Boeing SB 737-33-1121, Revision 1, dated 19 December 2002

Group 2 aeroplanes identified in Boeing SB 737-33-1121, Revision 1

Installing splice SP896

Boeing Service Bulletin 737-26A1083, Revision 1, dated 15 November 2001

\n```\n\n```html\n

Group 39 aeroplanes identified in SB
737-33-1133, Revision 3

Installing a smoke detection and fire extinguishing system in the cargo compartment

Boeing SB 737-26A1083, Revision 1

Group 59 aeroplanes identified in Special Attention SB 737-33-1132, Revision 2

Replacing the very high frequency (VHF) and high frequency (HF) communications panels with radio control panels

Boeing SB 737-23-1102, dated 3 June 1999

Actions accomplished before the effective date of this Directive in accordance with the service bulletins identified in Table 2 are considered acceptable for compliance with the corresponding actions specified in this Directive.

Table 2 - Previous Issues of Service Bulletins

Service Bulletin

Revision

Date

Special Attention SB 737-33-1133
SB 737-33-1133
SB 737-33-1133
Special Attention SB 737-33-1132
Special Attention SB 737-33-1132

Original
Revision 1
Revision 2
Original
Revision 1

19 December 2002
17 April 2003
4 December 2003
20 March 2003
4 March 2004

Later revisions of the above SB(s), approved by the United States Federal Aviation Administration (FAA) as an Alternate Method of Compliance (AMOC) to FAA AD 2006-15-18, are considered acceptable for compliance with the equivalent Requirements of this Directive.

Note: FAA AD 2006-15-18 Amdt 39-14699 refers.

Compliance:

For Requirement 1 - Within 48 months after the effective date of this Directive.

For Requirement 2 - Prior to or concurrently with accomplishment of Requirement 1.

This Airworthiness Directive becomes effective on 28 September 2006.

Background:

The FAA has received a report that the master dim and test system circuit does not have wiring separation of the test ground signal for redundant equipment in the flight compartment. This lack of separation could allow a single fault failure in flight to simulate a test condition and show test patterns instead of the selected radio frequencies on the communications panels, which could inhibit communication between the flight crew and air traffic control, affecting the continued safe flight of the aeroplane.

\n```\n\n| | This Directive requires the modification of the wiring for the master dim and test system and for certain aeroplanes, related concurrent actions as necessary. |\n| --- | -------------------------------------------------------------------------------------------------------------------------------------------------------------- |\n\n![](image.001.png) \nJames Coyne \nDelegate of the Civil Aviation Safety Authority\n\n14 August 2006","sortOrder":0},{"sectionNumber":"AD/B737/293","sectionType":"part","heading":"AD/B737/293","content":"## AD/B737/293","sortOrder":1},{"sectionNumber":"Master Dim and Test System Wiring","sectionType":"part","heading":"Master Dim and Test System Wiring","content":"## Master Dim and Test System Wiring","sortOrder":2},{"sectionNumber":"10/2006","sectionType":"part","heading":"10/2006","content":"## 10/2006","sortOrder":3}],"analysis":{"flash_summary":{"complexity_score":6,"scope_assessment":{"changed":false,"description":"The Directive implements corrective wiring modifications described in the FAA reference and specified Boeing service bulletins to address lack of test-ground separation that can affect communications panels (Background; Applicability). It accepts prior SB actions and later FAA‑approved SB revisions as compliant (Table 2), and does not expand beyond the identified corrective and concurrent actions."},"complexity_factors":["Applicability spans multiple 737 series and specific 'groups' identified inside Boeing Special Attention SBs (Applicability).","Primary technical requirement is a wiring modification carried out 'in accordance with the Accomplishment Instructions' of two different Boeing SBs, requiring detailed technical work by qualified maintenance personnel (Requirement 1).","Prior or concurrent actions are mandated for certain groups and reference additional SBs (Table 1), increasing coordination and verification tasks for operators.","Acceptance of earlier SB issues and later FAA‑approved revisions as Alternate Methods of Compliance introduces cross-referencing and approval-tracking (Table 2; note: FAA AD 2006-15-18 refers).","Fixed compliance timeframe of 48 months creates scheduling and cost-timing pressure on operators (Compliance: 'Within 48 months').","Safety rationale is specific (separation of test ground signal to prevent communications panel failure), so the technical fix must directly address that wiring separation, limiting alternative fixes (Background).","Compliance requires records of accomplished SB actions and possible concurrent installations (e.g. engine instrument system, smoke-detection, radios) listed in Table 1, increasing administrative burden."],"plain_english_summary":"This Directive requires operators of listed Boeing 737 models to modify the master dim and test-system wiring per specified Boeing service bulletins to remove a single-fault condition that can make communications panels show test patterns instead of selected radio frequencies. Operators must also perform specified prior or concurrent service-bulletin actions and complete the work within 48 months. Operators bear the cost and scheduling burden; the regulator recognises certain earlier or FAA‑approved service bulletin revisions as acceptable for compliance."},"flash_summary_failed":{"failed":true,"reason":"Unauthenticated. Configure AI_GATEWAY_API_KEY or use a provider module. Learn more: https://ai-sdk.dev/unauthenticated-ai-gateway","source":"analysis-cron"},"kimi_summary":{"content_quality":"ok","complexity_score":4,"scope_assessment":{"changed":false,"description":"This AD maintains its original scope as a targeted safety directive addressing a specific wiring separation issue in Boeing 737 aircraft. The inclusion of prior/concurrent actions for specific aircraft groups is necessary to ensure the main modification can be properly accomplished, rather than representing scope creep."},"complexity_factors":["Multiple aircraft model groups with different requirements (737-300/-400/-500 vs 737-600/-700/-700C/-800/-900)","Cross-references to 5 different Boeing Service Bulletins with specific revision numbers and dates","Conditional logic requiring prior/concurrent actions for specific aircraft groups (Groups 2, 37, 39, 46, 57, 59)","Table-based structure with nested dependencies (Table 1 and Table 2)","Grandfathering clause allowing compliance via earlier service bulletin revisions","Reference to US FAA AD 2006-15-18 and AMOC (Alternate Method of Compliance) provisions"],"plain_english_summary":"This AD mandates rewiring the cockpit master dim-and-test system on certain Boeing 737s because inadequate circuit separation can falsely trigger test patterns on comm panels, potentially hiding tuned radio frequencies and cutting pilot–ATC communications. \n\nIt affects Classic and Next‑Generation 737 models; operators must complete the wiring modification (earlier compliant service‑bulletin work already performed counts)."}},"importantCases":[],"_links":{"self":"/api/acts/ad-b737-293-master-dim-and-test-system-wiring","history":"/api/acts/ad-b737-293-master-dim-and-test-system-wiring/history","analysis":"/api/acts/ad-b737-293-master-dim-and-test-system-wiring/analysis","conflicts":"/api/acts/ad-b737-293-master-dim-and-test-system-wiring/conflicts","importantCases":"/api/acts/ad-b737-293-master-dim-and-test-system-wiring/important-cases","documents":"/api/acts/ad-b737-293-master-dim-and-test-system-wiring/documents"}}