{"id":"F2005L02062","name":"AD/ELECT/75 Amdt 1 - TCM Magneto Impulse Coupling","slug":"ad-elect-75-amdt-1-tcm-magneto-impulse-coupling","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":36246,"registerId":"commonwealth-F2005L02062-current","compilationNumber":null,"startDate":"2026-04-01","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"Electrical Equipment","sectionType":"division","heading":"Electrical Equipment","content":"### Electrical Equipment\n\n| AD/ELECT/75 Amdt 1 | TCM Magneto Impulse Coupling | 9/2005 |\n| ------------------ | ---------------------------- | ------ |\n\n```html\n

Applicability:

Teledyne Continental Motors (TCM) (formerly Bendix) magnetos that have a magneto part number (P/N) listed in Table 1, installed on Lycoming AEIO-540,
HIO-540, IO-540, O-540 and TIO-540 series engines:

Table 1

P/N

Model

P/N

Model

10-51365-32
10-51365-34
10-51365-35
10-51365-39
10-51365-40
10-51365-43
10-51365-47
10-51365-48
10-51365-54
10-51365-57
10-52350-19
10-52350-20
10-79020-6
10-79020-10
10-79020-11
10-79020-16
10-79020-17

S6LN-21
S6RN-21
S6RN-21
S6LN-21
S6LN-21
S6LN-21
S6RN-21
S6RN-21
S6LN-21
S6LN-21
S6RN-23
S6LN-23
S6LN-25
S6RN-25
S6LN-25
S6LN-25
S6LN-25

10-79020-18
10-79020-19
10-79020-118
10-79020-119
10-500556-101
10-500556-901
10-349350-4
10-349350-5
10-349350-6
10-349350-7
10-349370-4
10-382560-11
10-382560-13
10-682560-11
10-682560-13
10-682560-131

S6LN-25
S6RN-25
S6LN-25P
S6RN-25P
S6RSC-25P
S6RSC-25P S6RN-1225
S6RN-1225
S6LN-1225
S6LN-1225
S6LN-1227
D6LN-2031
D6LN-2031
D6LN-3000
D6LN-3000
D6LN-3000

Note 1: Table 1 is a partial reproduction of Table 1 from TCM Mandatory Service Bulletin (MSB) MSB645, dated 4 April 1994.

Note 2: Lycoming AEIO- 540, HIO-540, IO-540, 0-540 and TIO-540 series engines are known to be installed on, but not limited to, aircraft manufactured by the Cessna Aircraft Company, Maule Aerospace Technology Corporation, Mooney Aircraft Corporation, The New Piper Aircraft Inc. and Raytheon Aircraft Company (Formerly Beech Aircraft Company).

Requirement:

1. Inspect the impulse coupling assembly for wear using paragraphs 1.2 through 1.4.5 of the Detailed Instructions of TCM MSB645.

\n```\n\n```html\n

Installing a \"Shower-of-Sparks\" ignition system in place of a magneto system that has a riveted-impulse coupling assembly or a snap-ring impulse coupling assembly is optional terminating action for the repetitive inspection requirements. More information on installing a \"Shower-of-Sparks\" ignition system may be found in TCM Service Information Letter SIL648, dated 18 October 1994.

2. Replace any impulse coupling assembly that fails the inspection with a serviceable riveted or snap-ring impulse coupling assembly. Paragraphs 2 through 2.6 of the Detailed Instructions of TCM MSB645 and TCM Service Bulletin 639 dated March 1993 contain information on replacing the impulse coupling assembly.

3. If a snap-ring impulse coupling assembly is replaced with a riveted impulse coupling assembly, strike out the \"A\" on the magneto data plate.

Note 3: FAA AD 2005-12-06 Amdt 39-14122 refers.

Compliance:

For Requirement 1 -

a. Magnetos that have not previously been inspected - Initially as specified in Table 2 and thereafter as specified in Table 3.

Table 2

Type of Impulse Coupling Assembly

Impulse Coupling Time in Service (TIS) as of the Effective Date of this Directive

Inspect

Riveted

100 or more hours time since new or overhaul (TSN) or TSN is unknown.

Fewer than 100 hours TSN.

Within 10 hours TIS after the effective date of the original issue of this Directive.

Before accumulating 100 hours TSN.

Snap-ring

450 or more hours TSN.


Fewer than 450 hours TSN.

Within 50 hours TIS after the effective date of the original issue of this Directive.
Before accumulating 500 hours TSN.

Note 4: Previous inspections may have been accomplished in accordance with AD/ELECT/68 (FAA AD 96-12-07).

b. Magnetos that have previously been inspected - Repeat the inspections as specified in Table 3.

\n```\n\n```html\n

Table 3

Type of Impulse Coupling Assembly

Inspect

Riveted

Within 100 hours time since the last inspection.

Snap-ring

Within 500 hours time since the last inspection.

For Requirement 2 - Before further flight after the Requirement 1 inspection.

For Requirement 3 - Before further flight after the snap-ring impulse coupling assembly is replaced.

This Amendment becomes effective on 1 September 2005.

Background:

This Directive supersedes AD/ELECT/68 which will be cancelled. AD/ELECT/68 required repetitive inspections of riveted and snap-ring impulse coupling assemblies and, if necessary, their replacement when they were worn beyond limits.

This Directive requires a reduced inspection interval for magnetos with riveted impulse coupling assemblies installed on certain Lycoming engine models. The Directive does not lower the inspection interval for magnetos with snap-ring impulse coupling assemblies. The Directive also limits the applicability to certain Lycoming engine models. These actions result from data provided by the manufacturer to the United States Federal Aviation Administration that showed a need to reduce the inspection intervals for riveted-impulse coupling assemblies used on certain Lycoming engine models.

Note 5: Teledyne Continental Ignitions Systems Service Bulletin SB643B dated 6 April 2005 provides the manufacturer recommended periods for inspection/overhaul for TCM magnetos installed on engine types that are not specifically referenced in this Amendment. Inspection periods specified in this Amendment supersede those in SB643B.

The original issue of this Directive was issued to aid in the prevention of failure of the magneto impulse coupling assembly and possible engine failure.

This Amendment continues the requirements of the original issue but corrects Table 1 by limiting the listing to magnetos installed on the specified Lycoming engines and adds a note in the background indicating where the manufacturer’s recommended maintenance intervals may be found.

\n```\n\n| | The original issue of this Directive became effective on 19 July 2005. |\n| --- | ---------------------------------------------------------------------- |\n\n![](image.001.png) \nDavid Villiers \nDelegate of the Civil Aviation Safety Authority\n\n22 July 2005","sortOrder":0},{"sectionNumber":"AD/ELECT/75 Amdt 1","sectionType":"part","heading":"AD/ELECT/75 Amdt 1","content":"## AD/ELECT/75 Amdt 1","sortOrder":1},{"sectionNumber":"TCM Magneto Impulse Coupling","sectionType":"part","heading":"TCM Magneto Impulse Coupling","content":"## TCM Magneto Impulse Coupling","sortOrder":2},{"sectionNumber":"9/2005","sectionType":"part","heading":"9/2005","content":"## 9/2005","sortOrder":3}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":4,"scope_assessment":{"changed":true,"description":"This Amendment narrows the scope compared to the original AD/ELECT/75. The original issue applied more broadly, but Amendment 1 specifically limits applicability to certain Lycoming engine models (AEIO-540, HIO-540, IO-540, O-540 and TIO-540 series) and corrects Table 1 to remove magnetos not installed on these engines. The inspection intervals for riveted couplings were also reduced (tightened) based on new manufacturer data."},"complexity_factors":["Multiple compliance tables (Tables 2 and 3) with different deadlines based on prior inspection history and component type","Cross-references to external manufacturer documents (TCM MSB645, TCM SB639, TCM SIL648) that contain the actual detailed inspection procedures","Conditional logic: different inspection intervals for riveted vs snap-ring assemblies (100 hours vs 500 hours)","Nested applicability criteria: specific part numbers → specific magneto models → specific engine series → specific aircraft manufacturers","Amendment structure requires understanding what changed from the original AD/ELECT/68 and the original issue of AD/ELECT/75","Optional terminating action (Shower-of-Sparks installation) creates an alternative compliance path"],"plain_english_summary":"This AD requires owners/operators of certain Lycoming AEIO‑/HIO-/IO-/O-/TIO‑540‑series engines equipped with specific Teledyne Continental magnetos to perform repetitive inspections of the magneto impulse coupling and replace worn units to prevent in‑flight engine failure. Amendment 1 shortens inspection intervals for riveted couplings, narrows affected engines, and allows installing an alternative Shower‑of‑Sparks ignition to remove the inspection burden. Compliance is mandatory for affected aircraft, operators and maintenance organisations."},"flash_summary":{"complexity_score":5,"scope_assessment":{"changed":true,"description":"This amendment changes scope relative to the original Directive in two concrete ways: (1) it narrows the applicability by correcting Table 1 so the listed magneto part numbers are limited to those installed on specified Lycoming AEIO‑540, HIO‑540, IO‑540, O‑540 and TIO‑540 engines; and (2) it reduces the inspection interval for riveted impulse‑coupling assemblies on those engines (repeat interval set to 100 hours), while leaving snap‑ring intervals unchanged (500 hours). The amendment also adds a reference to the manufacturer’s recommended intervals for other engine types and supersedes the previous AD (AD/ELECT/68)."},"complexity_factors":["33 magneto part numbers listed in Table 1 (detailed applicability)","Two impulse‑coupling types with different TSN thresholds and inspection windows (riveted vs snap‑ring)","Separate initial inspection timing rules (Table 2) and repeat intervals (Table 3) — nested conditional logic","Cross‑references to multiple external manufacturer documents (TCM MSB645, SB639, SIL648) and to FAA AD material","Requirement to replace failed parts before further flight (immediate operational consequence)","Optional terminating action (conversion to Shower‑of‑Sparks) creates an alternative compliance pathway","Administrative instruction to amend magneto data plate if coupling type changes","Supersedes a prior Directive (AD/ELECT/68) and corrects Table 1 — historical cross‑linking and changing scope"],"plain_english_summary":"**What this directive does (mechanics)**\n\n- Requires inspections of the magneto impulse-coupling assembly (the small mechanical starter that momentarily spins the magneto to produce a hot spark on engine start) on a specific list of Teledyne Continental Motors (TCM) magnetos when they are installed on certain Lycoming AEIO‑540, HIO‑540, IO‑540, O‑540 and TIO‑540 engine models (see Table 1 for the specific magneto part numbers). (Applicability)\n\n- Tells you how and when to inspect: follow the Detailed Instructions in TCM Mandatory Service Bulletin MSB645 (paragraphs 1.2–1.4.5) for the wear inspection (Requirement 1). (Requirement 1)\n\n- Sets the initial inspection timing based on the type of impulse coupling assembly (riveted or snap‑ring) and the time since new/overhaul (TSN). The windows are given in Table 2:\n - Riveted: if 100+ hours TSN (or TSN unknown) — inspect within 10 hours time in service (TIS) after the original effective date; if <100 hours TSN — inspect before reaching 100 hours TSN.\n - Snap‑ring: if 450+ hours TSN — inspect within 50 hours TIS after the original effective date; if <450 hours TSN — inspect before accumulating 500 hours TSN. (Table 2)\n\n- Requires repeating the inspections at regular intervals (Table 3):\n - Riveted impulse couplings: inspect every 100 hours since the last inspection.\n - Snap‑ring impulse couplings: inspect every 500 hours since the last inspection. (Table 3)\n\n- Requires immediate replacement (with a serviceable riveted or snap‑ring impulse coupling assembly) of any coupling that fails the inspection, and that the replacement be completed before further flight. (Requirement 2)\n\n- If a snap‑ring impulse coupling is replaced by a riveted coupling, instructs the operator to strike out the “A” on the magneto data plate to reflect the change. (Requirement 3)\n\n- Offers an optional, alternate terminating action: operators may install a “Shower‑of‑Sparks” ignition system in place of the magneto system; guidance on that conversion is in TCM Service Information Letter SIL648 (this removes the repetitive inspection obligation if chosen). (Optional terminating action)\n\n- Cross‑references and source documents: the directive depends on TCM MSB645 (detailed inspection steps), TCM Service Bulletin 639 (replacement details), and TCM SIL648 (conversion option). It also notes related FAA AD material. (Notes)\n\n**Who this affects**\n\n- Aircraft owners/operators and maintenance organisations that operate aircraft with the listed TCM magneto part numbers installed on the specified Lycoming engine models (common on aircraft from Cessna, Piper, Mooney, Maule and Beech/Raytheon as noted). They must carry out the inspections, record the work, and replace couplings that fail inspection before flight.\n\n- Maintenance providers and parts suppliers, because the directive may increase demand for inspections, replacement impulse coupling assemblies, or for conversion kits if operators choose the Shower‑of‑Sparks option.\n\n**Why it matters (stated purpose and practical implications)**\n\n- The stated purpose (from the directive) is to reduce the risk of impulse‑coupling failure and the possible resulting engine failure by shortening inspection intervals for riveted couplings on the specified engine models and by repeating inspections at fixed intervals. The directive cites manufacturer data provided to the FAA as the basis for this change. (Background)\n\n- Costs and incentives: operators pay for more frequent inspections, potential replacements, and aircraft downtime. That creates an incentive to either accept the inspection/replacement costs or to pursue the optional terminating action (retrofit to a different ignition system) if that is cheaper over time.\n\n- Trade‑offs and practical risks: shorter inspection intervals improve the chance of spotting wear early, but they increase maintenance burden and operating costs (labour, parts, aircraft out of service). If replacement parts are limited, operators could face supply delays. There is also a small administrative step (striking out the data‑plate mark) when changing coupling types.\n\n- Implementation and compliance: the work must follow the manufacturer’s detailed instructions (MSB645 and SB639); compliance therefore requires access to those documents and competent maintainers who follow them. The directive sets firm timing windows and ‘‘before further flight’’ replacement requirements, so missed inspections or delayed replacements affect an aircraft’s legality to fly.\n\n**Concrete behaviour changes the directive forces**\n\n- Owners/operators must inspect impulse couplings on the listed magnetos at the specified initial times and then at 100‑hour (riveted) or 500‑hour (snap‑ring) repeat intervals.\n- Faulty couplings must be replaced before the aircraft returns to service.\n- Operators may choose to convert to a Shower‑of‑Sparks system to avoid recurrent inspections, which shifts costs from recurring inspections to a one‑off modification and associated certification/installation work.\n\n**Where the directive narrows or extends prior practice**\n\n- This amendment supersedes a previous Directive (AD/ELECT/68) and reduces the inspection interval for riveted impulse couplings on the named Lycoming engines (while leaving snap‑ring intervals unchanged). It also narrows the magneto part‑number listing to those installed on the specified Lycoming engine types and points operators to the manufacturer’s service information for other engine types. (Background; Note 5)"},"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-elect-75-amdt-1-tcm-magneto-impulse-coupling","history":"/api/acts/ad-elect-75-amdt-1-tcm-magneto-impulse-coupling/history","analysis":"/api/acts/ad-elect-75-amdt-1-tcm-magneto-impulse-coupling/analysis","conflicts":"/api/acts/ad-elect-75-amdt-1-tcm-magneto-impulse-coupling/conflicts","importantCases":"/api/acts/ad-elect-75-amdt-1-tcm-magneto-impulse-coupling/important-cases","documents":"/api/acts/ad-elect-75-amdt-1-tcm-magneto-impulse-coupling/documents"}}