{"id":"F2008L02658","name":"AD/F50/99 - Electrical Power - AC Contactors","slug":"ad-f50-99-electrical-power-ac-contactors","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":74695,"registerId":"commonwealth-F2008L02658-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"Fokker F50 (F27 Mk 50) Series Aeroplanes","sectionType":"division","heading":"Fokker F50 (F27 Mk 50) Series Aeroplanes","content":"### Fokker F50 (F27 Mk 50) Series Aeroplanes\n\n| AD/F50/99 | Electrical Power - AC Contactors | 8/2008 |\n| --------- | -------------------------------- | ------ |\n\n| Applicability: | F27 Mark 050 and Mark 0502 aircraft, all serial numbers, unless modified during production to incorporate Fokker ECR 51780 or whilst in service in accordance with Fokker Service Bulletin SBF50-24-030 dated 6 November 2003 or later revision approved by the European Aviation Safety Agency (EASA).                                                                                                                                                                                                               |\n| -------------- | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |\n| Requirement:   | 1. Remove the standard nuts and lock washers from electrical power contactors part number (P/N) SG02206, install new self-locking nuts and perform the applicable tests on the AC Bus Transfer System in accordance with the Accomplishment Instructions of Fokker Services SBF50-24-031 dated 29 January 2008 or later revision approved by the EASA.                                                                                                                                                                |\n|                | Note 1: The replacement of contactors P/N SG02206 with improved versions in accordance with SBF50-24-030 or later revision approved by the EASA is acceptable as an alternate method of compliance for Requirement 1 provided that the replacement is accomplished within 36 months after the effective date of this Directive.                                                                                                                                                                                       |\n|                | 2. Contactors P/N SG02206 may not be installed on any aircraft as a replacement part, unless it has been modified in accordance with Goodrich Power Systems SB SG02206-24-01 dated 4 March 2008 or later revision approved by the EASA.                                                                                                                                                                                                                                                                               |\n|                | Note 2: EASA AD 2008-0091 refers.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                     |\n| Compliance:    | For Requirement 1 - Within 36 calendar months after the effective date of this Directive.                                                                                                                                                                                                                                                                                                                                                                                                                             |\n|                | For Requirement 2 - After 31 May 2011.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                |\n|                | This Airworthiness Directive becomes effective on 31 July 2008.                                                                                                                                                                                                                                                                                                                                                                                                                                                       |\n| Background:    | Several incidents have been reported where an electrical burning smell was noted in the cockpit, originating from the Electrical Power Centre.Troubleshooting revealed a partly molten terminal, which normally attaches a wire or bus bar to a stud of an Electrical Power Contactor, P/N SG02206. Furthermore, heat damage to the contactor stud itself was found. Material investigation revealed that the terminal, which was attached to the stud, was not properly torque tightened when the incident occurred. |\n\n|     | Loss of torque is considered to have occurred during operation, for reasons not fully understood. Further loosening may have taken place in-service under influence of vibration. As a result, poor contact caused electrical arcing during which extremely high temperatures were developed, leading to partial melting of the terminal.Investigation of some other burned contactors revealed evidence (flat spring lock washer) of a fully torqued terminal/stud connection when the overheating occurred. The exact cause for the increase in temperature in the contactor and the terminal/stud could not be determined. However, it could not be excluded that an increase of the temperature inside the contactor could lead to reduction of the reliability of the contactor stud/terminal connection due to loss of lock washer tension. The affected Electrical Power Contactor is used on several locations in the electrical power system, i.e. Generator Line Contactor (GLC), Bus Tie Contactor (BTC), Auxiliary Power Contactor (APC) and External Power Contactor (EPC).This condition, if not corrected, could lead to further cases of overheating of terminals and studs of Electrical Power Contactors P/N SG02206, possibly resulting in the loss of electrical power systems, electrical arcing and fire/smoke in the cockpit. |\n| --- | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |\n\n![](image.001.png)  \nJames Coyne  \nDelegate of the Civil Aviation Safety Authority\n\n13 June 2008","sortOrder":0},{"sectionNumber":"AD/F50/99","sectionType":"part","heading":"AD/F50/99","content":"## AD/F50/99","sortOrder":1},{"sectionNumber":"Electrical Power - AC Contactors","sectionType":"part","heading":"Electrical Power - AC Contactors","content":"## Electrical Power - AC Contactors","sortOrder":2},{"sectionNumber":"8/2008","sectionType":"part","heading":"8/2008","content":"## 8/2008","sortOrder":3}],"analysis":{"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"},"flash_summary":{"complexity_score":4,"scope_assessment":{"changed":false,"description":"The Directive’s scope is focused and consistent with its stated safety purpose: it applies to F27 Mark 050 and 0502 aircraft except those already modified in production or per SBF50-24-030 (Applicability), and mandates modification or replacement of contactors P/N SG02206 and a ban on installing unmodified units unless modified per Goodrich SB (Requirement 1–2). No provisions expand the affected fleet or parts beyond those identified; compliance timing and alternative compliance routes are specified (Compliance; Notes)."},"complexity_factors":["Technical electrical fault with uncertain root cause (investigation could not fully determine why temperature rose) increases diagnostic and compliance uncertainty (Background).","Specific part-level action: targets a single part number (P/N SG02206) but used in multiple system locations (GLC, BTC, APC, EPC), raising safety-critical stakes (Background).","Two compliance paths: mandatory retrofit (self-locking nuts + tests) and an alternate method allowing full contactor replacement per SBF50-24-030, with a 36‑month deadline for compliance (Requirement; Note 1; Compliance).","Installation prohibition: ban on installing unmodified SG02206 after a later date unless modified per Goodrich SB SG02206-24-01, affecting parts inventory and supply (Requirement 2; Note 2; Compliance).","Dependence on external documents and approvals (Fokker Service Bulletins, Goodrich SB, and EASA-approved revisions) creates procedural complexity and administrative dependency (Applicability; Requirement; Notes).","Multiple time thresholds (36 calendar months for retrofit; prohibition effective after 31 May 2011; directive effective 31 July 2008) require fleet scheduling and record-keeping (Compliance).","Operational compliance requires both hardware change and functional testing of the AC Bus Transfer System, increasing maintenance scope and potential aircraft downtime (Requirement 1)."],"plain_english_summary":"This Airworthiness Directive orders maintenance changes to AC contactors P/N SG02206 on Fokker F50 (F27 Mk 050/0502) aeroplanes: replace standard nuts and lock washers with self‑locking nuts and test the AC Bus Transfer System, and prohibits fitting unmodified SG02206 contactors after a set date unless modified. It aims to prevent overheating, arcing and loss of electrical power after reported incidents involving partly molten terminals, and so affects operators, maintenance providers and parts suppliers through new work, parts and compliance deadlines."},"kimi_summary":{"content_quality":"ok","complexity_score":4,"scope_assessment":{"changed":false,"description":"This AD maintains its original narrow scope — addressing a specific safety defect in a specific aircraft type's electrical contactors. The alternate compliance method and installation restrictions are natural extensions of the core safety purpose rather than scope creep."},"complexity_factors":["Multiple compliance pathways with conditional logic (primary requirement vs. alternate method of compliance)","Cross-references to three external technical documents (Fokker SBF50-24-031, SBF50-24-030, and Goodrich SB SG02206-24-01)","Specific part number tracking (P/N SG02206) with installation restrictions","Dual compliance deadlines (36-month window for Requirement 1, fixed date for Requirement 2)","Applicability exclusions based on prior modifications (ECR 51780 or SBF50-24-030)","Reference to foreign regulator approval (EASA — European Aviation Safety Agency)"],"plain_english_summary":"Operators of Fokker F50 Mark 050/0502 aircraft must fix a hazardous electrical fault: AC contactors (P/N SG02206) have been overheating and melting from loose connections, risking arcing, smoke, fire, or loss of electrical power in flight.\n\nThe AD requires modification or replacement of the contactors within 36 months (or use the factory upgrade/approved service fix) and bans installation of unmodified SG02206 contactors after 31 May 2011."}},"importantCases":[],"_links":{"self":"/api/acts/ad-f50-99-electrical-power-ac-contactors","history":"/api/acts/ad-f50-99-electrical-power-ac-contactors/history","analysis":"/api/acts/ad-f50-99-electrical-power-ac-contactors/analysis","conflicts":"/api/acts/ad-f50-99-electrical-power-ac-contactors/conflicts","importantCases":"/api/acts/ad-f50-99-electrical-power-ac-contactors/important-cases","documents":"/api/acts/ad-f50-99-electrical-power-ac-contactors/documents"}}