{"id":"F2005L00135","name":"AD/A320/166 - Elevator and Aileron Computer","slug":"ad-a320-166-elevator-and-aileron-computer","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":33550,"registerId":"commonwealth-F2005L00135-current","compilationNumber":null,"startDate":"2026-04-01","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"Airbus Industrie A319, A320 and A321 Ser","sectionType":"division","heading":"Airbus Industrie A319, A320 and A321 Series Aeroplanes","content":"### Airbus Industrie A319, A320 and A321 Series Aeroplanes\n\n| AD/A320/166 | Elevator and Aileron Computer | 3/2005 TX |\n| ----------- | ----------------------------- | --------- |\n\n| Applicability: | A320 all certified models, all manufactured serial numbers, except aircraft that have incorporated Airbus modification 33317 during production or Airbus Service Bulletin A320-27-1149 whilst in service.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 |\n| -------------- | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |\n| Requirement:   | Amend the Minimum Equipment List (MEL) by inserting Temporary Revision (TR) TR No 01-27/01H issue 01 of the Master Minimum Equipment List (MMEL) A318/A319/A320/A321 that introduces the operational limitation “Above FL 200, the use of speed brakes lever is limited to its half position” when the aircraft is under MMEL ELAC 1.Later revisions of the above document approved by the DGAC are acceptable for compliance with this Directive.                                                                                                                                                                                                                                                                                                                                                        |\n|                | Note: DGAC AD F-2005-013 (EASA Approval 2005-496) refers.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 |\n| Compliance:    | Before 31 January 2005.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |\n|                | This Airworthiness Directive becomes effective on 28 January 2005.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |\n| Background:    | The Direction Générale de l’Aviation Civile of France has advised that during investigations on an A320 aeroplane the following critical flight phase was evident:When the aircraft is under MMEL with ELAC 1 (Elevator and Aileron Computer) inoperative or ELAC 1 PITCH FAULT cautions displayed, the loss of SEC 1 (Spoiler and Elevator Computer) in descent when speed brakes are deflected will lead to:- the automatic retraction of speed brakes 3 and 4,- the loss of the double hydraulic pressurisation on elevators.In manual mode and at high speed, the retraction of speed brakes 3 and 4 from their full extended position will induce a pitch down effect that cannot be counteracted by the elevator controlled by a single actuator causing the aircraft to pitch down and accelerate. |\n\n|     | This Directive requires the amendment of the MEL to ensure the aeroplane remains under control. |\n| --- | ----------------------------------------------------------------------------------------------- |\n\n![](image.001.png)  \nJames Coyne  \nDelegate of the Civil Aviation Safety Authority\n\n25 January 2005","sortOrder":0},{"sectionNumber":"AD/A320/166","sectionType":"part","heading":"AD/A320/166","content":"## AD/A320/166","sortOrder":1},{"sectionNumber":"Elevator and Aileron Computer","sectionType":"part","heading":"Elevator and Aileron Computer","content":"## Elevator and Aileron Computer","sortOrder":2},{"sectionNumber":"3/2005 TX","sectionType":"part","heading":"3/2005 TX","content":"## 3/2005 TX","sortOrder":3}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":3,"scope_assessment":{"changed":false,"description":"This AD maintains its original narrow scope — addressing a specific flight control computer fault condition in specific Airbus models. It has not expanded beyond its original safety purpose of preventing pitch-down incidents during dual computer failures."},"complexity_factors":["Single, specific technical requirement with clear applicability criteria","Only one defined technical term requiring explanation (MMEL/MEL)","No nested conditional logic — straightforward 'if ELAC 1 faulty, then limit speed brakes' rule","Short document (approximately 300 words of substantive content)","Single cross-reference to French DGAC directive for background context","Clear compliance deadline with no exceptions or alternative methods of compliance described"],"plain_english_summary":"This is an **Airworthiness Directive (AD)** — essentially a mandatory safety order issued by Australia's aviation regulator (CASA) for specific Airbus aircraft.\n\n**What it does:**\nIt requires airlines operating A319, A320, and A321 aircraft to update their operating manuals with a new safety restriction. When one specific flight computer (called **ELAC 1** — the Elevator and Aileron Computer) is broken or showing a fault warning, pilots must limit how far they extend the speed brakes (the panels on the wings that help slow the plane down). Specifically, above 20,000 feet, pilots can only use the speed brake lever halfway — not fully extended.\n\n**Why this matters:**\nFrench aviation investigators discovered a dangerous scenario: if ELAC 1 is already faulty and then a second computer (SEC 1) fails while the speed brakes are fully deployed during descent, the brakes automatically retract partially. At high speeds, this sudden retraction causes the plane's nose to pitch down sharply. With only one working elevator actuator (the mechanism that controls the plane's up/down movement), pilots might not be able to pull the nose back up, leading to a dangerous dive and acceleration.\n\n**Who it affects:**\n- All Airbus A320 family aircraft (A319, A320, A321)\n- All serial numbers, unless already modified with specific Airbus fixes\n- Airlines must comply by updating their Minimum Equipment List (MEL) — a document that specifies what equipment can be inoperative and under what conditions\n\n**The bottom line:**\nThis is a quick-fix safety patch to prevent a potential loss of control situation. Airlines had to implement this change by 31 January 2005."},"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"The directive remains narrowly focused on a specific safety mitigation: limiting speed‑brake deployment above FL200 when ELAC 1 is inoperative (or shows a PITCH FAULT) under MMEL relief. It does not expand to other systems, aircraft types, or broader operational regulation. The only scope variation allowed is that operators who have incorporated the stated modification or service bulletin are excluded, and later DGAC‑approved MMEL revisions may be used; these do not broaden the directive's original safety purpose."},"complexity_factors":["Single concrete mandatory action: insert a specific Temporary Revision (TR No 01-27/01H issue 01) into the MEL","One main exception: aircraft with Airbus modification 33317 incorporated in production or Airbus Service Bulletin A320-27-1149 embodied in service are excluded","Cross-reference to foreign regulator documents (DGAC AD F-2005-013 and EASA approval 2005-496) and allowance for later DGAC‑approved MMEL revisions","Two dates to track: effective date (28 January 2005) and compliance deadline (before 31 January 2005)","Technical dependency on interaction among ELAC 1, SEC 1, speed‑brake deployment and elevator hydraulic pressurisation (requires operational/technical understanding by operators and crews)"],"plain_english_summary":"**What this directive does**\n\n- Requires operators of Airbus A320 family aeroplanes to amend their Minimum Equipment List (MEL) by inserting a specific Temporary Revision (TR No 01-27/01H issue 01 to the Master MEL for A318/A319/A320/A321).\n- The inserted operational limitation says: when ELAC 1 (Elevator and Aileron Computer 1) is inoperative or indicating a PITCH FAULT and the aeroplane is being operated under the Master MEL (MMEL) allowance for that condition, then above flight level 200 (FL200) the speed‑brake lever must be limited to its half position.\n- Later revisions of the same MMEL document, if approved by the French regulator (DGAC), may be used instead of the specific TR named in the directive.\n\n**Who it affects**\n\n- Affected aircraft: Airbus A320 series (A319, A320, A321) — all certified models and all serial numbers, except those that already have Airbus modification 33317 incorporated in production or that have had Airbus Service Bulletin A320-27-1149 embodied while in service.\n- Affected parties: aircraft operators and their flight crews, maintenance departments that manage MELs, and regulators who approve MEL changes.\n\n**Why the change was required (technical trigger)**\n\n- Investigations identified a hazardous sequence: with ELAC 1 inoperative (or a displayed ELAC 1 PITCH FAULT) and then a loss of SEC 1 (Spoiler and Elevator Computer 1) during descent while speed brakes are extended, the aircraft can lose hydraulic pressurisation to the elevators and automatic retraction of speed brakes 3 and 4 can occur.\n- At high speed and in manual control with only a single elevator actuator functioning, the sudden retraction of those speed brakes from full extension can produce a pitch‑down that the remaining elevator authority cannot counteract — creating a risk of the aircraft pitching down and accelerating.\n- The MEL amendment limits the extent of speed‑brake deployment above FL200 in that MMEL condition to reduce the chance of that hazardous sequence.\n\n**How compliance works, practically**\n\n- Operators must insert the named TR into their MEL before the compliance date specified in the directive. That creates an operational limitation crews must follow when the aircraft is being dispatched under the MMEL with ELAC 1 unavailable.\n- If an operator has incorporated the stated modification or service bulletin, that operator is excluded from this requirement (because the modification/SB presumably mitigates the failure mode).\n- The directive accepts subsequent approved revisions of the MMEL TR (so operators can comply by adopting an updated DGAC‑approved MMEL revision rather than the specific issue named).\n\n**Who pays, who decides, and what changes in behaviour**\n\n- Who pays: aircraft operators bear the cost of amending their MEL documentation, training crews on the new limitation, and any operational impacts (e.g. altered descent/airspeed procedures or dispatch constraints). If operators elect to incorporate the Airbus modification or service bulletin to avoid the limitation, they bear the modification cost.\n- Who decides: the regulator (Civil Aviation Safety Authority in Australia implementing the directive, based on the DGAC/EASA safety finding) prescribes the MEL amendment; operators decide how to implement it operationally and whether to incorporate the optional modification/SB to remove the limitation.\n- Behaviour changes: flight crews must limit the speed‑brake lever to its half position above FL200 whenever operating under MMEL ELAC 1. Maintenance/operational control teams will restrict dispatch options where that MMEL relief is in use and must manage MEL entries accordingly.\n\n**Trade‑offs, implementation risks and practical effects**\n\n- Trade‑off: the limitation reduces exposure to a specific pitch‑down failure sequence, but it constrains a speed‑brake tool used during descent. That can change how crews manage descent speed and energy, potentially increasing pilot workload or affecting fuel/flight efficiency in some situations.\n- Compliance burden: primarily administrative (MEL revision insertion), crew training/briefing, and possible operational constraints when ELAC 1 is inoperative. If an operator opts to install the referenced modification or service bulletin, there is a capital/maintenance cost but that may remove the operational restriction.\n- Implementation risk: the safety benefit depends on proper crew adherence to the MEL limitation and correct identification of the MMEL condition (ELAC 1 inoperative or PITCH FAULT). Misunderstanding or incorrect MEL management could leave aircraft operating with the hazardous combination unmitigated.\n\n**References and cross‑links within the directive**\n\n- The directive cross‑references the DGAC AD F-2005-013 (EASA approval 2005-496) as the originating safety finding and accepts DGAC‑approved later MMEL revisions for compliance.\n\nOverall, the directive is a narrowly focused operational limitation inserted into the MEL to mitigate a specific aerodynamic/hydraulic failure sequence on A320 family aeroplanes when ELAC 1 is inoperative; operators either accept the MEL restriction or incorporate the referenced modification/service bulletin to avoid the restriction."},"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"}},"importantCases":[],"_links":{"self":"/api/acts/ad-a320-166-elevator-and-aileron-computer","history":"/api/acts/ad-a320-166-elevator-and-aileron-computer/history","analysis":"/api/acts/ad-a320-166-elevator-and-aileron-computer/analysis","conflicts":"/api/acts/ad-a320-166-elevator-and-aileron-computer/conflicts","importantCases":"/api/acts/ad-a320-166-elevator-and-aileron-computer/important-cases","documents":"/api/acts/ad-a320-166-elevator-and-aileron-computer/documents"}}