{"id":"F2008L00782","name":"AD/DHC-8/139 - Spoiler Cable Disconnect Caution Light","slug":"ad-dhc-8-139-spoiler-cable-disconnect-caution-light","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":72856,"registerId":"commonwealth-F2008L00782-current","compilationNumber":null,"startDate":"2026-04-02","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-8/139 | Spoiler Cable Disconnect Caution Light | 4/2008 |\n| ------------ | -------------------------------------- | ------ |\n\n| Applicability: | DHC-8-400, DHC-8-401 and DHC-8-402 model aeroplanes, Serial Numbers (S.N) 4003, 4004, 4006 and 4008 through 4129, inclusive. |\n| -------------- | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |\n| Requirement: | Unless already accomplished, modify the spoiler cable disconnect sensing circuit follows: |\n| | a. For aeroplanes S/N 4003, 4004, 4006 and 4008 through 4094, inclusive -Incorporate Modsum 4-110066. Bombardier Service Bulletin (SB)84-27-33, original issue dated 6 June 2007, or later revisions approved by the Chief, Continuing Airworthiness, Transport Canada, provide approved instructions for incorporating Modsum 4-110066. |\n| | b. For aeroplanes S/N 4095 through 4129, inclusive - Incorporate Modsum4-126356. Bombardier SB 84-27-28, Revision B, dated 25 September 2007, or later revisions approved by the Chief, Continuing Airworthiness, Transport Canada, provide approved instructions for incorporating Modsum 4-126356. |\n| | Note 1: Installation of Modsum 4-126356 in accordance with SB 84-27-28 original issue, dated 2 October 2006, or Revision A, dated 30 April 2007, before the effective date of this Directive is acceptable for compliance with this Directive. |\n| | Note 2: Transport Canada AD CF-2008-13 refers. |\n| Compliance: | Within 6000 hours time in service after the effective date of this Directive. |\n| | This Airworthiness Directive becomes effective on 10 April 2008. |\n| Background: | All DHC-8 Series 400 aeroplanes have had a spoiler fuselage cable disconnect sensing system installed during production. Subsequently it was discovered that, in the event of a spoiler fuselage cable disconnect, only the ROLL SPLR INBD HYD caution light will be illuminated until the aircraft speed decreases below 165 kts, at which time the ROLL SPLR OUTBD HYD caution light will also be illuminated. In the event of a spoiler fuselage cable disconnect in association with the existing indications described above, the reduction in roll authority could result in increased pilot workload during approach and landing. |\n\n| | Modsums 4-110066 and 4-126356 (each applicable to a different batch of aeroplane serial numbers) have been issued to rework the sensing circuit caution light indication to ensure that it is consistent for spoiler fuselage cable disconnects above and below 165 kts. Modsum 4-126356 has been installed in production on aircraft serial numbers 4130 and subsequent. |\n| --- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |\n\n![](image.001.png) \nDavid Punshon \nDelegate of the Civil Aviation Safety Authority\n\n18 February 2008","sortOrder":0},{"sectionNumber":"AD/DHC-8/139","sectionType":"part","heading":"AD/DHC-8/139","content":"## AD/DHC-8/139","sortOrder":1},{"sectionNumber":"Spoiler Cable Disconnect Caution Light","sectionType":"part","heading":"Spoiler Cable Disconnect Caution Light","content":"## Spoiler Cable Disconnect Caution Light","sortOrder":2},{"sectionNumber":"4/2008","sectionType":"part","heading":"4/2008","content":"## 4/2008","sortOrder":3}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":3,"scope_assessment":{"changed":false,"description":"This is a standard, narrow Airworthiness Directive addressing a specific technical defect in a specific aircraft type. It has not expanded beyond its original purpose of mandating a safety modification to the spoiler cable disconnect warning system."},"complexity_factors":["Short, single-purpose directive with one clear safety objective","Only 2 conditional branches based on aircraft serial number ranges (S/N 4003-4094 vs 4095-4129)","4 defined technical references (2 Modsums, 2 Service Bulletins)","Simple compliance deadline (6000 hours time in service)","No nested exceptions or complex cross-referencing to other legislation","Background explanation is straightforward and technical but not legally convoluted"],"plain_english_summary":"This AD requires operators of certain Bombardier DHC‑8‑400 (Q400) aircraft to install a wiring modification so both spoiler‑cable disconnect warning lights illuminate immediately, rather than the second light only appearing below 165 knots. It applies to specified serial‑numbered -400/-401/-402 aircraft and must be done within 6,000 flight hours of 10 April 2008.\n\nFixing the lights prevents pilots being unaware of reduced roll authority during critical landing phases, reducing loss‑of‑control risk."},"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"The AD stays within its original technical purpose: to correct inconsistent spoiler disconnect caution-light indications for specified DHC-8-400 series serial numbers. It does not broaden scope beyond that safety fix (no additional systems, no new operational limitations, and no expansion to other serial-number cohorts beyond those explicitly listed)."},"complexity_factors":["Two discrete serial-number ranges with different required Modsums (4-110066 and 4-126356)","Cross-reference to two Bombardier Service Bulletins (SB 84-27-33 and SB 84-27-28) and allowance for later revisions approved by Transport Canada","One conditional acceptance clause (prior installation of Modsum 4-126356 under earlier SB revisions is acceptable)","Single compliance deadline expressed in flight hours (6000 hours TIS) rather than calendar time","Simple technical objective with limited operational exceptions (no continuing flight prohibitions or operational limitations included)"],"plain_english_summary":"**What this instrument does**\n\n- This is an Airworthiness Directive (AD) that requires a modification to the spoiler cable disconnect caution-light sensing circuit on a subset of Bombardier/De Havilland DHC-8-400 series aeroplanes.\n\n**Which aeroplanes are affected**\n\n- Affects DHC-8-400, -401 and -402 aeroplanes with the following serial numbers (S.N.): 4003, 4004, 4006, and 4008 through 4129 inclusive. (Aircraft S.N. 4130 and later already had the later modification fitted in production.)\n\n**What operators must do**\n\n- Unless already done, operators must incorporate one of two specified modification kits (called “Modsums”) into the spoiler cable disconnect sensing circuit: \n - For S.N. 4003, 4004, 4006 and 4008–4094: incorporate Modsum 4-110066 using Bombardier Service Bulletin (SB) 84-27-33 (original issue 6 June 2007) or a later Transport Canada–approved revision.\n - For S.N. 4095–4129: incorporate Modsum 4-126356 using Bombardier SB 84-27-28 (Revision B, 25 Sept 2007) or a later Transport Canada–approved revision. \n- If Modsum 4-126356 was installed earlier under SB 84-27-28 original issue (2 Oct 2006) or Revision A (30 Apr 2007), that counts as compliance.\n\n**When the work must be done**\n\n- Within 6,000 flight hours time in service after the AD’s effective date.\n\n**Why this is required (stated reason and technical effect)**\n\n- The installed sensing circuit could produce inconsistent cockpit caution-light indications when a spoiler fuselage cable disconnects. Above about 165 knots indicated airspeed, only the ROLL SPLR INBD HYD (inboard hydraulic) caution light would illuminate; below 165 kt the ROLL SPLR OUTBD HYD (outboard hydraulic) light would also illuminate. That inconsistent indication can hide the full nature of the failure at higher speeds and could reduce roll authority and increase pilot workload during approach and landing. \n- The required Modsums rework the sensing circuit so the caution-light indications are consistent both above and below 165 kt.\n\n**Who pays, who decides, and what changes behaviour**\n\n- Aircraft operators pay for parts, labour and aircraft downtime to install the Modsum appropriate to their serial number. \n- The regulator (the AD issuer and Transport Canada via approval of service bulletin revisions) decides the exact approved instructions and accepts prior installations for compliance. \n- Operators must schedule and perform the modification within the 6,000‑hour window; maintenance planners must track serial numbers and compliance records; flight crews experience a changed (more consistent) caution-light behaviour after modification.\n\n**Implementation, costs and risks**\n\n- Direct costs: parts and labour, and aircraft out-of-service time. The AD does not set a fixed price; actual cost will vary by maintenance facility and whether the work is combined with other scheduled maintenance. \n- Operational impact: the 6,000-hour compliance window gives operators flexibility to defer the work until a maintenance opportunity, lowering immediate downtime costs but delaying the safety improvement. \n- Technical/implementation risk: work must follow the approved Service Bulletins; improper installation or incorrect documentation could leave an aircraft non‑compliant. \n- Administrative burden: operators must verify serial numbers, use the correct SB revision approved by Transport Canada, and maintain compliance records.\n\n**Distribution of benefits and costs**\n\n- Benefits (safer, clearer cockpit indication) are concentrated on operators and flight crew of the affected serial-numbered aeroplanes and their passengers. \n- Costs (modification expense and downtime) are borne by those operators; there is no new fee or tax imposed by the regulator.\n\n**Cross-references and acceptance**\n\n- The AD cross-references specific Bombardier Service Bulletins and a Transport Canada AD (CF-2008-13). It accepts earlier installations done under earlier SB revisions for compliance where specifically noted.\n\nIn short: affected DHC-8-400 series aeroplanes must have their spoiler cable disconnect caution-light sensing circuit modified using a specified Modsum (kit) within 6,000 flight hours to make caution-light indications consistent at all speeds; operators pay and must follow the Transport Canada–approved service instructions."},"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-dhc-8-139-spoiler-cable-disconnect-caution-light","history":"/api/acts/ad-dhc-8-139-spoiler-cable-disconnect-caution-light/history","analysis":"/api/acts/ad-dhc-8-139-spoiler-cable-disconnect-caution-light/analysis","conflicts":"/api/acts/ad-dhc-8-139-spoiler-cable-disconnect-caution-light/conflicts","importantCases":"/api/acts/ad-dhc-8-139-spoiler-cable-disconnect-caution-light/important-cases","documents":"/api/acts/ad-dhc-8-139-spoiler-cable-disconnect-caution-light/documents"}}