{"id":"F2006B09645","name":"AD/F100/43 - Anti Skid Control Box","slug":"ad-f100-43-anti-skid-control-box","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":54463,"registerId":"commonwealth-F2006B09645-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/F100/43 - Anti Skid Control Box","content":"COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 \\- 105 CIVIL AVIATION SAFETY AUTHORITY\n\nSCHEDULE OF AIRWORTHINESS DIRECTIVES\n\n![](image.001.png)  \n![](image.002.png)  \nFokker F100 (F28 Mk 100) Series Aeroplanes\n\nAIRWORTHINESS DIRECTIVE\n\n![](image.002.png)\n\n![](image.002.png)  \nFor the reasons set out in the background section, the CASA delegate whose signature appears below issues the following Airworthiness Directive (AD) under subregulation 39.1 (1) of CAR 1998. The AD requires that the action set out in the requirement section (being action that the delegate considers necessary to correct the unsafe condition) be taken in relation to the aircraft or aeronautical product mentioned in the applicability section: (a) in the circumstances mentioned in the requirement section; and (b) in accordance with the instructions set out in the requirement section; and (c) at the time mentioned in the compliance section.\n\n| AD/F100/43     | Anti Skid Control Box                                                | 4/2001     |\n| -------------- | -------------------------------------------------------------------- | ---------- |\n| Applicability: | F.28 Mk.0100 series aeroplanes.                                      |            |\n| Requirement:   | Either:                                                              |            |\n|                | a. Modify all Skid control boxes having Part Number (P/N) 6004272-3, | 6004272-4, |\n\n6004272-5 and 6004272-6 in accordance with ABS Corporation Service Bulletin (SB) Fo100-32-83 dated 30 October 2000; or\n\nb. Replace all Skid control boxes having P/N 6004272-3, 6004272-4, 6004272-5 and 6004272-6 with improved units having P/N 6004272-7 in accordance with Fokker Services SB F100-32-123 dated 15 November 2000.\n\nNote: RLD AD 2000-149 (A) refers.\n\nCompliance: Within the next 24 calendar months after the effective date of this Directive.\n\nThis Airworthiness Directive becomes effective on 19 April 2001.\n\nBackground: During 1999 the Dutch Rijksluchtvaartdienst (RLD) received a report concerning an incident with a Fokker 100, where during an approach, the liftdumpers inadvertently deployed. Preliminary investigation revealed that the outboard wheelspeed signal was induced to ‘high’ by electromagnetic interference (EMI), but the liftdumper arming test did not detect the signal because it was not transmitted until the skid control box was ‘powered up’ on landing gear DOWN selection.\n\nRLD considered that two separate design safety features were not effective. Analysis of the liftdumper system protection against EMI led RLD to mandate certain modifications on the affected aircraft to achieve a configuration, which is significantly less susceptible to EMI on the wheelspeed signals. The RLD issued BLA 1998-100/2 (AD/F100/33) to require modification of the grounding to the shielding of the Wheelspeed Sensor wiring and in addition, the installation of new electrical grounds for the Wheelspeed Sensor Channel of the Anti-Skid Control Box. A modified Skid Control Box was then developed to improve the resistance of the skid control system against unknown sources of EMI, the installation of which was subsequently mandated by BLA 1999-127 (AD/F100/39).\n\nCOMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 \\- 105 CIVIL AVIATION SAFETY AUTHORITY\n\nSCHEDULE OF AIRWORTHINESS DIRECTIVES\n\nABS Corporation, which supplies the Skid Control Box, has developed another modification, which renders the Skid Control Box even less susceptible to EMI signals during power-up and power-down transients. Since a potentially unsafe condition has been identified that may still exist or develop on other aircraft of the same type design, this Directive requires the modification or replacement of currently installed Skid Control Boxes with improved units.\n\nPrior compliance with AD/F100/39 is not considered compliance with this Directive.\n\n![Signature of Eugene Paul Holzapfel, Delegate of the Civil Aviation Safety Authority.](image.003.png)  \n\nEugene Paul Holzapfel\n\nDelegate of the Civil Aviation Safety Authority 8 March 2001\n\n![](image.002.png)  \n\nThe above AD is notified in the Commonwealth of Australia Gazette on 21 March 2001.","sortOrder":0}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":3,"scope_assessment":{"changed":false,"description":"This Airworthiness Directive maintains its original scope as a targeted safety intervention for a specific aircraft type and component. It does not expand beyond the Fokker F100 series or the anti-skid control box issue identified in the background incident."},"complexity_factors":["Single, discrete technical requirement with two alternative compliance paths","Specific part numbers and service bulletin references (4 part numbers, 2 service bulletins)","Clear compliance deadline (24 calendar months)","Explicit statement that prior compliance with related AD/F100/39 does not satisfy this directive","No nested conditional logic or extensive cross-referencing to other legislation","Background section provides narrative context but does not create additional legal obligations"],"plain_english_summary":"This CASA safety order mandates corrective work on Fokker F100 anti-skid control boxes to stop electromagnetic interference from causing false wheel-speed signals and unintended liftdumper/deployer events. It affects operators of F100s using control boxes p/n 6004272-3–6004272-6.\n\nIt matters because the defect can trigger dangerous braking or lift-dump deployment during approach; previous fixes are not sufficient, so affected units must be upgraded or replaced."},"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":false,"description":"The directive stays within the original safety purpose: it addresses an identified EMI vulnerability that can cause unintended liftdumper arming/deployment. It builds on earlier mandates (grounding/shielding and prior skid control box modifications) by requiring a further hardware hardening or replacement. The scope remains focused on correcting that specific unsafe condition for the same aircraft type and does not broaden regulatory reach beyond that original technical safety objective."},"complexity_factors":["Single aircraft type applicability (Fokker F100 / F28 Mk.100).","Two alternative compliance paths (modify existing units OR replace with improved unit).","Four affected original Skid Control Box part numbers (6004272‑3, 6004272‑4, 6004272‑5, 6004272‑6) plus one replacement P/N (6004272‑7).","Direct cross‑references to two external service bulletins (ABS Fo100‑32‑83 and Fokker F100‑32‑123) that contain the detailed technical work instructions.","Cross‑references to prior ADs/BLA (AD/F100/39, RLD BLA 1998‑100/2 and BLA 1999‑127) and an explicit note that prior compliance with AD/F100/39 is not acceptance for this AD.","Single, fixed compliance window (24 calendar months) — simple timing but mandatory.","Limited conditionality: no complex staged inspections or rolling thresholds; the condition is hardware change only."],"plain_english_summary":"**What this directive does (mechanically)**\n\n- **Who it applies to:** All Fokker F100 (F28 Mk.100) aeroplanes (see Applicability).\n- **What must be done:** Within 24 calendar months of the directive taking effect, each affected aircraft must either:\n  - Modify every installed Anti‑Skid (Skid) Control Box that has Part Number (P/N) 6004272‑3, 6004272‑4, 6004272‑5 or 6004272‑6 in accordance with ABS Corporation Service Bulletin Fo100‑32‑83 (dated 30 October 2000); or\n  - Replace those Skid Control Boxes with improved units having P/N 6004272‑7 in accordance with Fokker Services Service Bulletin F100‑32‑123 (dated 15 November 2000). (See Requirement and Compliance.)\n- **Timing:** Compliance is required within 24 calendar months after the AD’s effective date (Compliance). The AD became effective on 19 April 2001.\n- **Other notes:** A previous related directive (AD/F100/39) does not satisfy this requirement (Requirement / Background).\n\n**Why the change was ordered (official rationale and mechanical effect)**\n\n- The directive responds to an identified unsafe condition: electromagnetic interference (EMI) can induce a high outboard wheel‑speed signal during power‑up/power‑down transients. That signal can reach the skid/anti‑skid system after landing gear selection and cause liftdumpers to arm or deploy when not intended (Background).\n- The actions required (modify or replace skid control boxes) change the skid control box hardware and/or grounding/shielding arrangements so the wheel‑speed signals and skid control electronics are less susceptible to EMI during power transients (Requirement / Background).\n\n**Who pays, who decides, and what behaviour changes**\n\n- **Who pays:** Aircraft owners/operators pay for the parts, labour and aircraft downtime needed to carry out the modification or replacement (Requirement / Compliance). Maintenance organisations will typically perform the work under existing maintenance contracts.\n- **Who decides:** The Civil Aviation Safety Authority (CASA) delegate issued the AD; compliance choices (modify vs replace) are left to the operator so long as the work follows the named service bulletins (Requirement).\n- **Behaviour changes:** Operators must locate affected Skid Control Boxes (by P/N), schedule and perform either the modification or replacement within 24 months, keep maintenance records showing compliance, and ensure continued airworthiness per regulations.\n\n**Practical implementation considerations, trade‑offs and risks**\n\n- **Direct costs and downtime:** Parts, certified maintenance labour and any consequent aircraft time out of service are direct costs to operators. Replacement with P/N 6004272‑7 will generally cost more in parts than a modification, but may reduce future maintenance or failure risk — operators must weigh up immediate cost vs expected future benefits (Requirement / Background).\n- **Supplier and supply‑chain effects:** The directive cites ABS Corporation and Fokker Services service bulletins as the required instructions. This channels work and parts to those suppliers or approved maintenance organisations, concentrating demand for specific parts and technical instructions (Requirement). If parts are in limited supply, operators face scheduling risk and potential aircraft unavailability.\n- **Compliance risk and enforcement:** Non‑compliance risks regulatory action or withdrawal of aircraft type‑approval for operations. CASA enforces compliance under the Civil Aviation Regulations (Applicability / Compliance).\n- **Technical and certification burden:** The required work must be done in accordance with the named service bulletins; that typically requires certificated maintenance organisations and records to demonstrate compliance. If an operator seeks an alternative method of compliance, that would usually require approval from the regulator and supporting data (Requirement).\n- **Options and substitution effects:** Operators have a choice between modifying existing units or replacing them with the improved P/N 6004272‑7 units. That flexibility allows operators to choose lower upfront cost (modification) or longer‑term robustness (replacement), depending on fleet economics (Requirement).\n- **Interaction with earlier directives:** The AD explicitly states that prior compliance with AD/F100/39 does not satisfy this requirement, meaning operators must still undertake the new action even if they complied with the earlier AD (Requirement / Background).\n\n**Net effect (mechanical, not normative)**\n\n- The AD imposes a mandatory hardware change (modification or replacement) on operators of Fokker F100 aircraft with specified Skid Control Box part numbers, to reduce susceptibility to EMI during power transients and thereby reduce the risk of unintended liftdumper arming/deployment (Requirement / Background).\n\n(Section references in parentheses: Applicability, Requirement, Compliance, Background.)"},"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-f100-43-anti-skid-control-box","history":"/api/acts/ad-f100-43-anti-skid-control-box/history","analysis":"/api/acts/ad-f100-43-anti-skid-control-box/analysis","conflicts":"/api/acts/ad-f100-43-anti-skid-control-box/conflicts","importantCases":"/api/acts/ad-f100-43-anti-skid-control-box/important-cases","documents":"/api/acts/ad-f100-43-anti-skid-control-box/documents"}}