{"id":"F2005L00857","name":"AD/B747/326 - Flap Control Unit","slug":"ad-b747-326-flap-control-unit","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":34248,"registerId":"commonwealth-F2005L00857-current","compilationNumber":null,"startDate":"2026-04-01","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"Boeing 747 Series Aeroplanes","sectionType":"division","heading":"Boeing 747 Series Aeroplanes","content":"### Boeing 747 Series Aeroplanes\n\n| AD/B747/326 | Flap Control Unit | 5/2005 |\n| ----------- | ----------------- | ------ |\n\n| Applicability: | Model 747-400, -400D and -400F series aeroplanes, identified in Boeing Alert Service Bulletin (ASB) 747-27A2386, dated 13 March 2003.                                                                                                                                                     |\n| -------------- | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |\n| Requirement:   | 1. Replace at least one flap control unit (FCU) having part number (P/N) 285U0011-207 with a new or modified FCU having P/N 285U0011-208 in accordance with the Accomplishment Instructions of ASB 747-27A2386.                                                                           |\n|                | Note 1: ASB 747-27A2386 refers to Boeing Component Service Bulletin (CSB) 285U0011-27- 06, dated 13 March 2003, as an additional source of service information for modifying an FCU having P/N 285U0011-207 to P/N 285U0011-208.                                                          |\n|                | 2. For aeroplanes identified in Boeing Service Bulletin (SB) 747-27- 2319, dated 24 January 1991 - Replace the three FCUs having P/N 285U0011-205 or 285U0011-206 with new or modified FCUs having P/N 285U0011-207 in accordance with the Accomplishment Instructions of SB 747-27-2319. |\n|                | Note 2: SB 747-27-2319 refers to Boeing CSB 285U0011-27-04, dated 24 January 1991, as an additional source of service information for modifying the FCUs having P/N 285U0011-205 or 285U0011-206 to P/N 285U0011-207.                                                                     |\n|                | 3. FCUs P/N 285U0011-205 or -206 may not be installed on any aeroplane as a replacement part.                                                                                                                                                                                             |\n|                | Note 3: FAA AD 2005-04-03 Amdt 39-13975 refers.                                                                                                                                                                                                                                           |\n| Compliance:    | For Requirement 1 - At the earlier of the intervals specified below:                                                                                                                                                                                                                      |\n|                | a. Within 60 months after the effective date of this Directive,                                                                                                                                                                                                                           |\n|                | b. Within 25,000 hours time in service after the effective date of this Directive, or                                                                                                                                                                                                     |\n|                | c. Within 4,000 flight cycles after the effective date of this Directive.                                                                                                                                                                                                                 |\n|                | For Requirement 2 - Before or concurrent with the accomplishment of Requirement 1.                                                                                                                                                                                                        |\n|                | For Requirement 3 - As of the effective date of this Directive.                                                                                                                                                                                                                           |\n\n|             | This Airworthiness Directive becomes effective on 12 May 2005.                                                                                                                                                                                                                                                                                                                                                                                                                                                                      |\n| ----------- | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |\n| Background: | This Directive requires replacing at least one FCU in the main equipment centre with a new or modified FCU.This action is designed to prevent disconnection of autoland/autopilot functions and loss of primary flaps control and flaps indication display due to disengagement of all three FCUs at the same time. Disengagement of all three FCUs at the same time, could lead to a non-normal high speed landing with the flaps retracted, increased pilot workload and possible runway departure at high speeds during landing. |\n\n![](image.001.png)  \nJames Coyne  \nDelegate of the Civil Aviation Safety Authority\n\n31 March 2005","sortOrder":0},{"sectionNumber":"AD/B747/326","sectionType":"part","heading":"AD/B747/326","content":"## AD/B747/326","sortOrder":1},{"sectionNumber":"Flap Control Unit","sectionType":"part","heading":"Flap Control Unit","content":"## Flap Control Unit","sortOrder":2},{"sectionNumber":"5/2005","sectionType":"part","heading":"5/2005","content":"## 5/2005","sortOrder":3}],"analysis":{"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"},"flash_summary":{"complexity_score":4,"scope_assessment":{"changed":false,"description":"The AD stays within the original safety-focused purpose: mitigation of the hazard that all three FCUs could disengage simultaneously. It specifies targeted hardware upgrades (and a prohibition on older replacement parts) and cross-references manufacturer service instructions. It does not expand the subject matter beyond replacing or modifying the specific FCUs and preventing re-installation of older parts."},"complexity_factors":["Multiple specific part numbers to track (P/N 285U0011-205, -206, -207, -208)","Different requirements that apply depending on whether the aeroplane is identified in SB 747-27-2319","Cross-references to several Boeing service documents (ASB 747-27A2386, SB 747-27-2319, CSB 285U0011-27-06, CSB 285U0011-27-04)","Conditional compliance interval (earlier of 60 months, 25,000 flight hours, or 4,000 flight cycles) for Requirement 1","Sequencing requirement: Requirement 2 must be done before or concurrent with Requirement 1","Immediate prohibition on installation of certain parts (Requirement 3)","Technical operational context (autoland/autopilot, flaps control) requiring maintenance shop capability to perform modifications"],"plain_english_summary":"**What this directive does (in simple terms)**\n\n- This is an Airworthiness Directive (AD) for Boeing 747-400, -400D and -400F aeroplanes identified in Boeing Alert Service Bulletin (ASB) 747-27A2386 (13 March 2003).\n- It requires operators to replace specific Flap Control Units (FCUs) so that at least one FCU in the main equipment centre is changed to the newer/modified part number P/N 285U0011-208. (Requirement 1)\n- For aeroplanes listed in Boeing Service Bulletin (SB) 747-27-2319 (24 January 1991), the AD requires replacing the three FCUs with P/N 285U0011-205 or -206 by new/modified FCUs having P/N 285U0011-207. (Requirement 2)\n- After the AD’s effective date, FCUs with P/N 285U0011-205 or -206 may not be used as replacement parts. (Requirement 3)\n- Compliance timing: Replace at least one 207→208 by whichever comes first of: 60 months, 25,000 flight hours, or 4,000 flight cycles after the AD’s effective date (12 May 2005). The 205/206→207 replacement (where required) must be done before or at the same time as the 207→208 replacement. The ban on installing 205/206 is effective immediately on the AD date.\n\n**Why the directive was issued (stated purpose)**\n\n- The stated purpose is to prevent simultaneous disengagement of all three FCUs, which could disconnect autoland/autopilot functions and cause loss of primary flaps control and flap indication. The AD links that failure mode to a risk of a non-normal high‑speed landing with flaps retracted and higher pilot workload during landing.\n\n**How it works mechanically**\n\n- Operators inspect their fleet to identify which FCU part numbers are fitted (205, 206, 207 or 208).\n- Where 205/206 are fitted on aircraft listed in SB 747-27-2319, the operator must upgrade all three to P/N 285U0011-207 following SB 747-27-2319 (and the Boeing Component Service Bulletin cross-referenced there) before or at the time they do the next step.\n- Then, operators must install at least one P/N 285U0011-208 FCU in the main equipment centre per the Accomplishment Instructions of ASB 747-27A2386 (and Boeing CSB 285U0011-27-06 as an additional reference for modification).\n- From the AD effective date, 205/206 units are not permitted to be installed as replacement parts.\n\n**Who is affected and who pays**\n\n- Affected: operators/owners of Boeing 747-400, -400D and -400F aeroplanes specified in the ASB.\n- Costs are borne by the aircraft operator: parts (new or modified FCUs), labour to install/modify, aircraft downtime. Boeing or authorised component repair centres will receive orders for new/modified units or modification services.\n\n**Incentives and likely behavioural effects**\n\n- Operators must schedule maintenance to meet the AD intervals; they will prioritise aircraft near the compliance thresholds.\n- Parts suppliers that can supply P/N 285U0011-207 and -208 or provide the approved modification work have increased demand.\n- The ban on reinstalling 205/206 prevents backsliding; it forces owners to use the upgraded configurations for future maintenance.\n\n**Trade-offs, implementation risks and compliance burden**\n\n- Trade-offs: safety benefit (reduced risk of simultaneous FCU disengagement) versus operator costs for parts, labour and lost utilisation while the work is performed.\n- Implementation risks: availability of replacement/modification parts or qualified shops; scheduling the work within the stated intervals; ensuring conformity with the Boeing service instructions and any local maintenance approvals.\n- Compliance burden: locating affected aeroplanes, verifying part numbers, performing the specified modification/replacement per Boeing ASB/SB/CSB instructions, and record-keeping to show compliance.\n\n**Sources of required instructions and cross-references**\n\n- The AD requires work performed in accordance with Boeing ASB 747-27A2386 (13 March 2003) and references Boeing CSB 285U0011-27-06 for 207→208 modification.\n- For 205/206→207 replacement it refers to SB 747-27-2319 (24 January 1991) and Boeing CSB 285U0011-27-04.\n- The AD also notes the related FAA AD (2005-04-03).\n\n**Bottom line**\n\n- Operators of affected 747-400-series aeroplanes must upgrade FCUs on a defined schedule and may no longer fit older FCU part numbers as replacements. The measure changes operator maintenance choices and creates a recurring demand for upgraded FCUs or modification services; the stated objective is to reduce the risk of an event where all three FCUs disengage simultaneously, with attendant loss of autopilot/autoland and primary flap control/indication."},"kimi_summary":{"content_quality":"ok","complexity_score":3,"scope_assessment":{"changed":false,"description":"This is a standard airworthiness directive maintaining its original safety purpose. ADs are inherently narrow, technical instruments addressing specific equipment failures. The scope remains precisely targeted at the flap control unit failure mode described in the background section."},"complexity_factors":["Short, single-purpose directive with only 3 requirements","Clear applicability limited to specific Boeing 747-400 variants","Precise part number references (P/N 285U0011-207, -208, etc.) that are technical but not legally complex","Straightforward compliance timeline with three alternative thresholds (time, hours, cycles)","Cross-references to Boeing service bulletins (ASB 747-27A2386, SB 747-27-2319) but these are incorporated by reference rather than creating nested legal conditions","No defined terms section, no exceptions to exceptions, no conditional logic beyond the applicability criteria"],"plain_english_summary":"This is an **Airworthiness Directive (AD)** — a mandatory safety order issued by Australia's Civil Aviation Safety Authority (CASA). It applies to specific Boeing 747-400 series aircraft.\n\n**What it does:**\nThe directive requires airlines and aircraft operators to replace certain **flap control units (FCUs)** — electronic components that manage the wing flaps used during takeoff and landing. The old units can fail in a dangerous way: if all three FCUs disconnect at once, pilots lose automatic landing capability, flap control, and flap position displays. This could force a high-speed landing with flaps retracted (not fully extended), increasing the risk of running off the runway.\n\n**Who must act:**\n- Operators of Boeing 747-400, 747-400D (domestic), and 747-400F (freighter) models listed in Boeing's Alert Service Bulletin 747-27A2386.\n\n**What must be done:**\n1. **Replace at least one FCU** (part number 285U0011-207) with an improved version (part number 285U0011-208) within 60 months, 25,000 flight hours, or 4,000 flight cycles — whichever comes first.\n2. **For some older aircraft:** If they still have even older FCUs (part numbers ending in -205 or -206), all three must be upgraded to the -207 version before or during the main replacement.\n3. **Ban on old parts:** From the effective date, the oldest FCUs (-205 and -206) cannot be installed on any aircraft as replacement parts.\n\n**Why it matters:**\nThis prevents a rare but catastrophic failure mode where pilots lose critical landing assistance and flap control simultaneously, potentially causing a dangerous high-speed landing or runway excursion."}},"importantCases":[],"_links":{"self":"/api/acts/ad-b747-326-flap-control-unit","history":"/api/acts/ad-b747-326-flap-control-unit/history","analysis":"/api/acts/ad-b747-326-flap-control-unit/analysis","conflicts":"/api/acts/ad-b747-326-flap-control-unit/conflicts","importantCases":"/api/acts/ad-b747-326-flap-control-unit/important-cases","documents":"/api/acts/ad-b747-326-flap-control-unit/documents"}}