{"id":"F2007L02481","name":"AD/ENST 28/39 - Main Rotor Blade Retention Pin","slug":"ad-enst-28-39-main-rotor-blade-retention-pin","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":68004,"registerId":"commonwealth-F2007L02481-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"Enstrom F-28 Series Helicopters","sectionType":"division","heading":"Enstrom F-28 Series Helicopters","content":"### Enstrom F-28 Series Helicopters\n\n| AD/ENST 28/39 | Main Rotor Blade Retention Pin | 10/2007 DM |\n| ------------- | ------------------------------ | ---------- |\n\n| Applicability: | Model F-28, F-28A, F-28C, F-28C-2, F-28C-2R, F-28F, F-28F-R, 280, 280C, 280F, 280FX, TH-28, 480, and 480B helicopters, with a main rotor blade retention pin having a serial number that is listed below:04098-01 through 04098-5605018-01 through 05018-3605143-01 through 05143-5605341-1 through 05341-805341-10 through 05341-1705341-1905341-21 through 05341-3305341-35 through 05341-4205341-44 through 05341-5905341-6105341-6205341-64 through 05341-7106214-3 through 06214-1406214-16 through 06214-2306214-25 through 06214-2906214-3106214-33 through 06214-3506214-37 through 06214-5706214-59 through 06214-68 |\n| -------------- | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |\n| Requirement:   | 1. Check the serial number that is marked on the head of each main rotor blade retention pin (retention pin) and check if the number is listed in the Applicability section of this Directive. See Figure 1 for the location of the serial number. If there is no serial number marked on the head of the retention pin (ie. The retention pin head is blank), the retention pin does not need to be replaced and this determination constitutes a terminating action for the requirements of this Directive for that retention pin.                                                                                          |\n\n|     | 2. Determine the number of hours time in service (TIS) for any affected retention pin and replace the retention pin with a serviceable retention pin as follows:a. For a retention pin with 545 or more hours TIS, remove the retention pin and replace it with a serviceable retention pin with a serial number that is not listed in the Applicability section of this Directive.b. For a retention pin with less than 545 hours TIS, remove the retention pin and replace it with a serviceable retention pin with a serial number that is not listed in the Applicability section of this Directive.Note 1: Enstrom Service Directive Bulletin No. T-029, original issue, and Enstrom Service Directive Bulletin No.0102, original issue, or later FAA approved revisions, refer.Note 2: FAA AD 2007-16-01 Amdt 39-15140 refers. |\n| --- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ |\n\n| Compliance: | 1. Before further flight.For Requirement 2.a: Within the next 5 hours TIS or within 30 days, whichever occurs first.For Requirement 2.b: Before reaching 550 hours TIS or within 30 days, whichever occurs first.This Directive shall be entered on the Maintenance Release as maintenance required. The Requirement 1 serial number check may be performed and certified by the Pilot in Command who has been trained by an appropriately qualified person. In this case, a copy of this Directive is to be carried in the aircraft. |\n| ----------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |\n|             | This Airworthiness Directive becomes effective on 15 August 2007.                                                                                                                                                                                                                                                                                                                                                                                                                                                                     |\n| Background: | The FAA received a report from the manufacturer that some retention pins were not manufactured in accordance with specifications cited on the engineering drawing. Failure of a retention pin would result in separation of a main rotor blade from the helicopter, and subsequent loss of control.                                                                                                                                                                                                                                   |\n\n![](image.002.png)  \nDavid Villiers  \nDelegate of the Civil Aviation Safety Authority\n\n8 August 2007","sortOrder":0},{"sectionNumber":"AD/ENST 28/39","sectionType":"part","heading":"AD/ENST 28/39","content":"## AD/ENST 28/39","sortOrder":1},{"sectionNumber":"Main Rotor Blade Retention Pin","sectionType":"part","heading":"Main Rotor Blade Retention Pin","content":"## Main Rotor Blade Retention Pin","sortOrder":2},{"sectionNumber":"10/2007 DM","sectionType":"part","heading":"10/2007 DM","content":"## 10/2007 DM","sortOrder":3}],"analysis":{"flash_summary":{"complexity_score":4,"scope_assessment":{"changed":false,"description":"This AD stays within its original, stated safety purpose: it targets specific retention pins believed to be out of specification and requires their inspection and replacement on a defined timetable. It does not broaden the subject matter beyond defective retention pins or add unrelated requirements. The instrument's mechanics (serial‑number check, hours‑based replacement windows, and administrative recording) align with the stated intent to prevent rotor blade separation."},"complexity_factors":["Long list of serial number ranges in the Applicability section (multiple non‑contiguous ranges)","Two conditional replacement rules based on hours‑in‑service (>=545 hrs and <545 hrs) with different compliance windows","Special exception for pins with blank (unstamped) heads that terminates AD requirements for that pin","Pilot‑in‑Command allowed to perform the serial check if trained (adds a procedural/qualification condition)","Cross‑references to Enstrom Service Directive Bulletins and FAA AD for technical detail","Requirement to enter the AD on the Maintenance Release (administrative compliance step)"],"plain_english_summary":"**What this instrument does (mechanically):**\n\n- Requires operators of specified Enstrom F‑28/280/480 series helicopters to check the serial number stamped on each main rotor blade retention pin (the metal pin that helps hold a main rotor blade in place) and to replace any pin whose serial number appears in the AD's list, subject to the helicopter's hours-in-service (TIS) on that pin. (See \"Applicability\", \"Requirement\" and \"Compliance\".)\n\n**Who this affects:**\n\n- Owners, operators and maintenance organisations responsible for the listed Enstrom helicopter models (Model F‑28, F‑28A, F‑28C, F‑28C‑2, F‑28C‑2R, F‑28F, F‑28F‑R, 280, 280C, 280F, 280FX, TH‑28, 480 and 480B) when those helicopters have main rotor blade retention pins whose serial numbers fall inside the ranges printed in the Applicability section.\n\n**Why it matters (stated purpose):**\n\n- The manufacturer reported some retention pins were not manufactured to drawing specification. The AD states failure of a retention pin could cause a main rotor blade to separate from the helicopter, leading to loss of control. The AD implements inspections and (where required) replacement to remove pins thought to be defective.\n\n**How the rule works (step‑by‑step):**\n\n1. Check the serial number stamped on the head of each main rotor blade retention pin (Requirement 1). Figure 1 in the AD shows the number location. If the head is blank (no serial number), the AD says that pin does not need replacement and that finding is a \"terminating action\" for that pin (i.e. no further AD action for that pin is required).\n\n2. If a pin's serial number is listed in the AD's Applicability table, determine the pin's hours time in service (TIS) and then replace the pin with a serviceable pin whose serial number is NOT listed in the Applicability list as follows (Requirement 2):\n   - If the pin has 545 or more hours TIS: remove and replace the pin immediately (before further flight) and, if not that immediate case, within the next 5 hours TIS or within 30 days, whichever comes first (Requirement 2.a and Compliance).\n   - If the pin has less than 545 hours TIS: replace the pin before it reaches 550 hours TIS or within 30 days, whichever comes first (Requirement 2.b and Compliance).\n\n3. The AD must be recorded on the aircraft's Maintenance Release as maintenance required. The serial number check (Requirement 1) may be performed and certified by the Pilot‑in‑Command only if the pilot has been trained by an appropriately qualified person; if a pilot does the check, a copy of the AD must be carried in the aircraft (Compliance).\n\n4. The AD cross‑references Enstrom Service Directive Bulletins and the related FAA Airworthiness Directive for further technical guidance (Notes).\n\n**Who pays and who decides:**\n\n- Owners/operators pay for inspection time, replacement parts (serviceable retention pins with acceptable serial numbers), and any associated downtime. Maintenance organisations or qualified maintenance personnel decide and carry out the replacement work and record it on the Maintenance Release. The Pilot‑in‑Command may perform and certify the serial number check only if trained.\n\n**Costs, incentives and trade‑offs:**\n\n- Direct costs: inspection labour, replacement part purchase, and aircraft downtime. These are concentrated on affected owners/operators.\n- Incentives: owners have a strong safety and regulatory incentive to replace affected pins promptly to avoid grounding or enforcement action and to eliminate the catastrophic risk identified by the AD.\n- Supply risk / opportunity cost: if a supply of allowable replacement pins is limited, operators may face delays or higher acquisition costs; they may also need to source acceptable serial‑numbered parts or rely on maintenance shops that have stock.\n- Compliance burden: record keeping (Maintenance Release), possible requirement to carry the AD on board if the pilot performs the check, and ensuring accurate TIS records for each retention pin.\n\n**Implementation risks and practical issues:**\n\n- Correctly reading small stamped serial numbers under field conditions can be error prone. The AD allows the pilot to perform the serial check but requires training, which mitigates risk but imposes an additional requirement.\n- The AD relies on accurate TIS records for each pin to determine the correct replacement deadline.\n- Cross‑references to Enstrom and FAA service documents mean operators may need to consult multiple technical documents for full implementation details.\n\n**Source claim vs practical effect:**\n\n- The AD's stated aim is to remove pins potentially out of specification to prevent blade separation. Practically, it forces replacement of specific serial‑numbered pins within short time frames, shifting costs to operators and creating an operational requirement (inspections, parts procurement, and maintenance release entries). The AD does not expand duties beyond inspection and replacement of listed parts and the administrative requirements noted above (Requirements and Compliance sections)."},"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"},"kimi_summary":{"content_quality":"ok","complexity_score":3,"scope_assessment":{"changed":false,"description":"This is a targeted safety directive addressing a specific manufacturing defect in a critical helicopter component. The scope remains precisely focused on the identified defect and affected serial numbers, with no evidence of scope creep beyond the original safety purpose."},"complexity_factors":["Multiple serial number ranges to check (approximately 15 separate ranges with gaps)","Two-tier compliance timeline based on hours-in-service thresholds (545+ hours vs under 545 hours)","Cross-references to external documents (FAA AD 2007-16-01 and Enstrom Service Directives)","Conditional logic: blank serial numbers constitute terminating action (exemption from further requirements)","Dual compliance triggers (hours-based AND calendar-based: 'whichever occurs first')","Specific delegation of authority allowing pilots to perform initial inspection under training conditions"],"plain_english_summary":"This CASA Airworthiness Directive mandates owners/operators of specified Enstrom F‑28 series helicopters inspect main rotor blade retention pins for listed serial numbers and replace any affected pins within the prescribed flight‑hour/time limits. Trained pilots may perform the serial check (carrying the AD aboard), and replacements must be recorded on the Maintenance Release.\n\nIt responds to discovered manufacturing nonconformances: a failed pin could allow a blade to detach, causing loss of control and likely fatal accidents."}},"importantCases":[],"_links":{"self":"/api/acts/ad-enst-28-39-main-rotor-blade-retention-pin","history":"/api/acts/ad-enst-28-39-main-rotor-blade-retention-pin/history","analysis":"/api/acts/ad-enst-28-39-main-rotor-blade-retention-pin/analysis","conflicts":"/api/acts/ad-enst-28-39-main-rotor-blade-retention-pin/conflicts","importantCases":"/api/acts/ad-enst-28-39-main-rotor-blade-retention-pin/important-cases","documents":"/api/acts/ad-enst-28-39-main-rotor-blade-retention-pin/documents"}}