{"id":"F2005L03587","name":"AD/DHC-8/104 - Elevator Trim and Gust Lock Chain Failure","slug":"ad-dhc-8-104-elevator-trim-and-gust-lock-chain-failure","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":39187,"registerId":"commonwealth-F2005L03587-current","compilationNumber":null,"startDate":"2026-04-01","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"Bombardier (Boeing Canada/De Havilland) ","sectionType":"division","heading":"Bombardier (Boeing Canada/De Havilland) DHC-8 Series Aeroplanes","content":"### Bombardier (Boeing Canada/De Havilland) DHC-8 Series Aeroplanes\n\n| AD/DHC-8/104 | Elevator Trim and Gust Lock Chain Failure | 13/2005 |\n| ------------ | ----------------------------------------- | ------- |\n\n```html\n

Applicability:

Bombardier Inc. DHC-8 aircraft, Models 102, 103, 106, 201, 202, 301, 311, 314 and 315, Serial Numbers 003 through 610.

Requirement:

1. Insert a copy of the appropriate Temporary Amendment listed below in the Dash 8 aircraft flight manual (AFM) and brief flight crew on the requirement to conduct elevator trim checks.

Model

PSM

Temporary Amendment

102,103,and 106

1-81-1A

No. 9

102NS, 103NS and 106NS

1-81-1A

No. 8

201

1-82-1A

No. 11

202

1-82-1A

No. 10

201S and 202S

1-82-1A

No. 9

202HT

1-82-1A

No. 8

301

1-83-1A

No. 8

311

1-83-1A

No. 15

314 and 315

1-83-1A

No. 9

2. In accordance with Bombardier SB 8-27-105, Revision A, dated 13 September 2005, or later Transport Canada approved revisions, carry out the following:

(a) Visually inspect the elevator gust lock/ trim chains for the identifier RC 25; and

(b) Replace any chains and/or chain cable assemblies that do not have the RC 25 identifier.

3. Chains and chain cable assemblies, which do not have the identifier RC 25, shall not be used as a replacement on any aircraft.

\n```\n\n| | Terminating action for Requirement 1.The temporary amendment inserted in the AFM in accordance with requirement 1 of this AD, may be removed after completing the inspection and replacing the chains that do not have the RC 25 identifier.Note: Transport Canada AD CF-2005-38 refers. |\n| ----------- | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |\n| Compliance: | 1. Within 30 days of the effective date of this AD.2. Before accumulating 6 000 hours flight time, from the effective date of this AD; or within 36 months of the effective date of this AD, whichever occurs earlier.3. From the effective date of this AD. |\n| | This Airworthiness Directive becomes effective on 22 December 2005. |\n| Background: | Several elevator trim chain failures have been reported. The trim chain failures have resulted from hydrogen embrittlement cracking of the link plates. Failures of a trim chain are not annunciated to the flight crew. If a trim chain were to fail when the trim was set in an extreme NOSE DOWN, or extreme NOSE UP position, an undetected failure could result in control difficulties during aircraft rotation for takeoff. |\n\n![](image.001.png) \nJames Coyne \nDelegate of the Civil Aviation Safety Authority\n\n10 November 2005","sortOrder":0},{"sectionNumber":"AD/DHC-8/104","sectionType":"part","heading":"AD/DHC-8/104","content":"## AD/DHC-8/104","sortOrder":1},{"sectionNumber":"Elevator Trim and Gust Lock Chain Failur","sectionType":"part","heading":"Elevator Trim and Gust Lock Chain Failure","content":"## Elevator Trim and Gust Lock Chain Failure","sortOrder":2},{"sectionNumber":"13/2005","sectionType":"part","heading":"13/2005","content":"## 13/2005","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 mechanical defect in elevator trim and gust lock chains on DHC-8 aircraft. The model-specific variations and compliance timeframes are typical of airworthiness directives and do not represent scope creep."},"complexity_factors":["Single-issue directive with three clear requirements","Model-specific lookup table with 9 aircraft variants requiring different temporary amendment numbers","Cross-reference to external technical document (Bombardier Service Bulletin 8-27-105 Revision A)","Dual compliance timeframe (flight hours OR calendar months, whichever is earlier)","Terminating action clause allowing removal of temporary flight manual amendment after compliance","No nested exceptions or conditional logic — straightforward pass/fail inspection criteria"],"plain_english_summary":"CASA has issued a mandatory AD for Bombardier DHC‑8 (Dash 8) aircraft, serial numbers 003–610 of specified models, requiring an immediate flight‑manual amendment and urgent inspection of elevator trim and gust‑lock chains for hydrogen‑embrittlement risk.\n\nChains must bear the RC 25 identifier; non‑compliant parts must be replaced and are banned from installation. The AD addresses silent chain failure that can cause loss of control during takeoff, protecting flight safety."},"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"This AD remains narrowly focused on the original safety problem: failures of elevator trim chains due to hydrogen embrittlement. The measures — AFM temporary amendment, visual inspection for the RC 25 identifier, replacement of non‑RC25 chains, and prohibition of non‑RC25 parts — implement corrective actions consistent with that purpose. The AD does not add unrelated obligations or broaden the affected fleet beyond the originally identified DHC‑8 serial range, so it has not grown significantly beyond its original intent."},"complexity_factors":["Single‑issue Airworthiness Directive focused on elevator trim/gust-lock chains (limited subject matter)","3 specific mandatory actions (insert AFM temporary amendment and brief crew; visual inspection per SB; prohibition on using non‑RC25 parts)","Table mapping multiple DHC‑8 models/PSMs/temporary amendment numbers (adds administrative detail)","Cross‑reference to Bombardier SB 8‑27‑105 Rev A and later Transport Canada–approved revisions (external document dependency)","Multiple compliance timelines (30 days; before 6,000 flight hours or within 36 months; immediate prohibition)","Terminating action conditional on completion of inspection and replacements","Reliance on a single physical marker (RC 25 identifier) as the compliance criterion","Reference to a related foreign AD (Transport Canada AD CF‑2005‑38)"],"plain_english_summary":"**What this instrument does (mechanically)**\n\n- Applies to Bombardier (De Havilland) DHC-8 aeroplanes, Models 102, 103, 106, 201, 202, 301, 311, 314 and 315, serial numbers 003–610. (Applicability)\n- Requires the operator to insert a specified Temporary Amendment into the Aircraft Flight Manual (AFM) and brief flight crew on performing elevator trim checks. (Requirement 1)\n- Requires a visual inspection, in accordance with Bombardier Service Bulletin (SB) 8-27-105 Revision A or later Transport Canada–approved revisions, to check elevator gust-lock/trim chains for the identifier “RC 25”; any chains or chain-cable assemblies without the RC 25 mark must be replaced. (Requirement 2(a)–(b))\n- Prohibits using chains or chain-cable assemblies that do not carry the RC 25 identifier as replacements on any aircraft. (Requirement 3)\n- The temporary AFM amendment may be removed after the inspection and any required replacements are completed (terminating action for Requirement 1). (Terminating action)\n- Compliance timing: insert AFM amendment within 30 days of the AD; complete inspection/replacements before accumulating 6,000 flight hours from the AD’s effective date or within 36 months, whichever is earlier; the prohibition on non-RC25 parts is effective immediately. (Compliance)\n\n**Why the AD was issued (stated purpose)**\n\n- Transport Canada reported several failures of elevator trim chains caused by hydrogen embrittlement cracking of link plates. Failures are not annunciated to the flight crew and, if they occur with trim set at extreme nose-up or nose-down, could produce control difficulties during takeoff rotation. The AD is intended to ensure chains with the RC 25 identifier (which indicates the prescribed remedial part) are fitted and unmarked/older parts are removed. (Background; Requirement 2)\n\n**Practical effects: who pays, who decides, and what changes**\n\n- Who pays: aircraft operators (airlines, lessors, private owners) bear the direct costs — labour for AFM amendment and crew briefings, visual inspections, spare parts procurement, and fitting of replacement chains where required. (Requirement 1–3; Compliance)\n- Who decides: the AD prescribes the action; technical detail is delegated to Bombardier SB 8-27-105 Rev A and to Transport Canada if it approves later revisions. Operators follow the SB/approved revision when performing inspections and replacements. (Requirement 2)\n- Behaviour changes: operators must add a temporary AFM note and brief crews, perform a one-time visual inspection per the SB, replace non‑RC25 chains, and refuse non‑RC25 parts for future replacements. After completing the inspection/replacement the AFM temporary amendment can be removed. (Requirement 1–3; Terminating action)\n\n**Costs, incentives and trade‑offs**\n\n- Direct compliance cost: time and labour for AFM amendment and briefings; inspection hours; cost of replacement chains and installation; potential aircraft downtime while waiting for parts. (Requirement 1–3; Compliance)\n- Incentives: operators have a clear incentive to replace non‑RC25 parts promptly to remove the AFM restriction and avoid repeated operational limitations or extra checks. That concentrates costs on operators with non‑compliant inventory and creates demand for RC25‑marked parts.\n- Supply and sourcing risk: the AD restricts replacement parts to those carrying the RC 25 identifier. If supply of compliant parts is limited, operators may face longer downtime or higher prices. (Requirement 3)\n- Implementation risk: the mandated check is a visual inspection for the RC 25 identifier. If hydrogen embrittlement can occur in parts that are visually indistinguishable or falsely marked, a visual-only method may not detect all at‑risk items; the AD relies on the SB’s methodology and the RC 25 marking as a corrective measure. (Requirement 2; Background)\n- Opportunity cost: maintenance resources diverted to this inspection and replacements are not available for other tasks until complete. (Compliance)\n- Administrative burden: operators must manage AFM temporary amendments and crew briefings and track compliance within the prescribed timelines. (Requirement 1; Compliance)\n\n**Regulatory and implementation features to note**\n\n- The AD cross‑references a manufacturer service bulletin (Bombardier SB 8-27-105 Rev A) and allows later Transport Canada–approved revisions to that SB to be used. That delegates technical detail and any future technical updates to the manufacturer and the foreign regulator. (Requirement 2)\n- The AD includes a terminating action (removal of the AFM temporary amendment) once inspections and replacements have been completed, so the measure is framed as a corrective (not permanent) operational restriction. (Terminating action)\n\n**Net effect (plain)**\n\nOperators of the listed DHC‑8 aircraft must quickly (within 30 days) add a flight‑manual note and brief crews, carry out a prescribed visual inspection for the RC 25 identifier on elevator trim/gust‑lock chains within the stated flight‑hour or time limit, replace any non‑RC25 items, and thereafter may remove the AFM temporary amendment. The objective is to reduce the risk of undetected trim‑chain failure due to hydrogen embrittlement that could affect control during takeoff. (Requirement 1–3; Terminating action; Background)"},"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"}},"importantCases":[],"_links":{"self":"/api/acts/ad-dhc-8-104-elevator-trim-and-gust-lock-chain-failure","history":"/api/acts/ad-dhc-8-104-elevator-trim-and-gust-lock-chain-failure/history","analysis":"/api/acts/ad-dhc-8-104-elevator-trim-and-gust-lock-chain-failure/analysis","conflicts":"/api/acts/ad-dhc-8-104-elevator-trim-and-gust-lock-chain-failure/conflicts","importantCases":"/api/acts/ad-dhc-8-104-elevator-trim-and-gust-lock-chain-failure/important-cases","documents":"/api/acts/ad-dhc-8-104-elevator-trim-and-gust-lock-chain-failure/documents"}}