AD/EC 135/18 - Cyclic-Stick Locking Device - Modification

The AD is built around a small number of technical and administrative concepts that determine obligations and effects. First, the operative technical concept is a change to the cyclic stick cantilever by removing two parts, the slide and the spring, from that cantilever. The AD instructs operators to perform that work "in accordance with ECD Alert Service Bulletin (ASB) EC135-67A-015 dated 14 April 2008, or later NAA approved revision." The ASB is thus the required method of compliance; the AD does not itself set out step-by-step modification instructions, it delegates those procedural details to the manufacturer's ASB or an approved revision.

Second, the AD distinguishes between mechanical modification and operating procedure. It mandates a specific flight crew procedural change by requiring the Rotorcraft Flight Manual (FLM) to include a precise note instructing crews to move the cyclic to neutral before engine start, and explaining the new centring method and the loss of the previous locking function. The AD permits direct insertion of the AD into the FLM or use of FLM pages supplied by ECD, so it defines acceptable forms of documentation amendment.

Third, the AD establishes a narrow scope of applicability by serial number. It covers "EC135 and EC635 series helicopters, all models, serial number (S/N) 0005 through 0699 inclusive," but explicitly exempts a list of serial numbers. Those applicability boundaries determine which operators must comply and which are outside the requirement.

Fourth, the AD links to wider regulatory and manufacturer material: it refers to EASA AD 2008-0113 and relies on ECD ASB EC135-67A-015 or a later NAA approved revision. The phrase "or later NAA approved revision" creates a dependency on National Aviation Authority approvals for any subsequent ASB revisions.

Finally, the safety claim driving the AD is concrete: reported incidents of take-off with a locked cyclic stick, together with the risk of loss of control. The AD frames the modification as removing the possibility of locking, thereby addressing the hazard by mechanical redesign rather than by procedural controls alone. The AD does not quantify the incidents, nor does it include alternative corrective actions within its text beyond the specified modification and FLM amendment.

The AD affects owners, operators, maintenance organisations, and aircrew of Eurocopter Deutschland EC135 and EC635 series helicopters that fall within the serial number range specified by the AD. The applicability clause states the covered population precisely: "EC135 and EC635 series helicopters, all models, serial number (S/N) 0005 through 0699 inclusive," with a list of specific excluded serial numbers. Those excluded serial numbers are: 0028, 0076, 0093, 0098, 0099, 0102, 0104, 0106, 0108, 0110, 0111, 0113, 0114, 0116, 0117 and 0119. Operators of helicopters with serial numbers in the inclusive range but not in the exclusion list must comply.

Who pays: The AD itself requires the modification and FLM amendment, but does not specify who pays for parts, labour, or downtime. Practically, operators and their maintenance providers will bear direct costs of carrying out the modification, obtaining the ASB, and performing the required FLM amendment. The AD does not provide financial assistance, subsidies, or cost-sharing mechanisms.

Who decides and approves: The AD is issued by the Civil Aviation Safety Authority delegate, and the means of compliance references a manufacturer ASB or a later NAA approved revision. That structure means the CASA delegate mandates action, the manufacturer supplies the specific procedure via the ASB, and a National Aviation Authority has a role where later ASB revisions are concerned. The AD also references EASA AD 2008-0113, indicating coordination with another aviation regulator.

Operational roles affected: flight crews must change a pre-engine-start action in accordance with the required FLM note; maintenance personnel must perform the physical modification; the operator's documentation control must insert the AD or approved FLM pages into or alongside the FLM; and continuing airworthiness personnel must track compliance within the 30 day window specified.

Indirectly affected parties: maintenance scheduling and aircraft availability are likely to be affected during the compliance period, given the 30 day compliance deadline. The AD does not state permitted downtime procedures or provide alternative compliance timelines, therefore operators must plan to perform the modification and FLM amendment within the stated period or otherwise address regulatory compliance with their NAA or CASA.

Key duties imposed by the AD are specific and limited to two actions, and are accompanied by precise temporal and documentary instructions. The AD's Requirement section contains the operative duties.

Duty 1, mechanical modification: Operators must "modify the cyclic stick locking/centering device by removing the slide and spring from the cyclic stick cantilever in accordance with ECD Alert Service Bulletin (ASB) EC135-67A-015 dated 14 April 2008, or later NAA approved revision." The duty therefore combines an obligation to perform a physical alteration with a mandated method of performance, the manufacturer's ASB or a National Aviation Authority approved later revision.

Duty 2, flight manual amendment: Operators must "amend the Rotorcraft Flight Manual (FLM) by inserting the following note" and the AD reproduces the exact wording that must be included. The AD also specifies that this may be accomplished "by inserting a copy of this AD into the FLM, or by FLM page(s) supplied by ECD." That phrasing indicates acceptable forms of documentation compliance and limits the form of the required change to either a literal copy of the AD or manufacturer-supplied FLM pages.

Temporal duty: The AD sets a single timeframe for compliance, requiring completion "within 30 days after the effective date of this AD." The AD's effective date is specified separately: "This Airworthiness Directive becomes effective on 31 July 2008." Therefore the duties must be carried out within a defined, relatively short window measured from 31 July 2008.

Rights and discretion contained in the AD: The AD delegates procedural detail to the ECD ASB and to National Aviation Authority approvals. That creates two limited areas of operator discretion. First, operators must follow the ASB, but if a later NAA approved revision exists then that revision may be used. Second, for the FLM amendment the AD allows either insertion of the AD text or use of ECD-supplied FLM pages. The AD does not, within its text, provide an express mechanism for an alternative means of compliance, an extension of time, or an exemption, nor does it set out appeal or variance processes. The absence of those procedural rights in the text means operators seeking an alternative route would need to engage the issuing authority or their NAA, but the AD itself does not spell that out.

Documentation duty: The AD implicitly requires records to show that the modification and FLM amendment have been accomplished within the 30 day window, by virtue of mandating the physical insertion of the AD or FLM pages. The AD does not detail record-keeping standards or retention periods.

Instructional duty for crews: By mandating a specific FLM note, the AD imposes a duty on operators to ensure crew procedures align with the new centring method, so that flight crews "move the cyclic stick to its neutral position" before engine start and follow the described centring technique.

The AD text itself does not contain an explicit penalties clause, monetary fines, or criminal provisions. The document sets out mandatory technical and procedural requirements, an effective date, and a 30 day compliance period, and it is signed by a CASA delegate. The AD does not specify within its text the enforcement mechanism, administrative penalties, or the consequences of non-compliance.

Because the AD imposes mandatory duties, the document functions as a regulatory instrument that requires operators to act, but the AD on its face confines itself to prescribing actions and timeframes: it requires the modification "in accordance with ECD Alert Service Bulletin ... or later NAA approved revision," and it requires FLM amendment "within 30 days after the effective date." It does not, within its text, describe inspection rights, civil penalties, certificate suspensions, or any process for notice of non-compliance or administrative review. The AD likewise does not specify whether compliance will be monitored, by whom, or how evidence of compliance should be submitted to CASA or another authority.

The AD makes an administrative cross-reference to EASA AD 2008-0113 "dated 10 June 2008," and it delegates the method of modification to the manufacturer's ASB or "later NAA approved revision," implying that National Aviation Authorities and manufacturer documentation will be central to compliance verification. The AD is signed by a CASA delegate, dated 20 June 2008, and effective 31 July 2008, thereby establishing the regulatory provenance and effective timeframe for the duties.

Practitioners should note that the instrument as provided does not spell out enforcement steps, nor does it record discretionary powers to vary the compliance period, grant exemptions, or accept alternative means of compliance. It also does not state the administrative route for an operator who believes the AD is inapplicable to a particular airframe, or who seeks an extension. Those governance gaps in the text mean that any operator seeking a different outcome must engage directly with the issuing authority, their National Aviation Authority, or the manufacturer to seek an authorised alternative or an official clarification. The AD's silence on penalties and enforcement procedures should be treated as an absence of text, not as an absence of enforcement capability; the AD does not itself create or limit such capability within its printed provisions.

The AD explicitly cross-references other regulatory instruments and sets up interactions with manufacturer material and National Aviation Authority processes. It states that "EASA AD 2008-0113 dated 10 June 2008 refers," which creates an express linkage with a European aviation regulator's directive addressing the same or related subject matter. The AD also conditions the acceptable method of modification on "ECD Alert Service Bulletin (ASB) EC135-67A-015 dated 14 April 2008, or later NAA approved revision." That wording produces two concrete interactions.

First, the AD requires operators to follow manufacturer service material, but only the ASB version dated 14 April 2008 or a later revision that has NAA approval. That means the ASB is incorporated by reference as the technical method of compliance, but the operator can rely on a later ASB revision only if it has NAA approval. This condition creates an operational interface between CASA's AD, the manufacturer's technical documentation, and the approvals process of whichever National Aviation Authority is responsible for authorising later revisions. The AD does not itself specify which NAA approvals suffice, or the process to obtain or rely on such approvals, beyond the phrase "NAA approved revision."

Second, by referring to EASA AD 2008-0113, the AD indicates regulatory alignment across jurisdictions. The AD does not reproduce the text of the EASA AD, it merely records that it "refers" to it. That creates an information trail for operators and regulators to consult the EASA instrument for additional context or parallel obligations. The AD does not state how conflicts between the EASA AD and the CASA AD would be resolved, but the cross-reference signals that operators may need to consult both documents if they operate across regulatory boundaries.

The AD is silent on interactions with generic aviation law, such as airworthiness certificate conditions, continuing airworthiness responsibilities or civil penalty regimes. It does not set out how compliance with the AD should be recorded in maintenance logs, nor does it provide an explicit route for seeking an Alternative Means of Compliance or a Time Extension inside the AD text. The requirement to amend the Rotorcraft Flight Manual by inserting the AD text or manufacturer-supplied pages creates a direct interaction with operator documentation obligations, but the AD does not prescribe record-keeping details or how the amendment should be reflected in other regulatory filings.

In sum, the AD interacts with other laws and instruments by incorporating manufacturer ASB procedures conditional on NAA approval, and by referencing EASA's corresponding AD. The AD leaves procedural interactions,such as approvals of later revisions, alternative compliance pathways, and enforcement mechanisms,to be managed through the usual regulatory and manufacturer channels, but those arrangements are not specified within the text of the AD itself.

The AD text provided contains a date and a narrow amendment trail limited to cross-references. The document is entitled AD/EC 135/18 and dated 8/2008. It is signed by James Coyne, Delegate of the Civil Aviation Safety Authority, and dated 20 June 2008. The AD records that it "becomes effective on 31 July 2008." The Requirement references a specific manufacturer document, ECD Alert Service Bulletin EC135-67A-015 dated 14 April 2008, and allows use of "later NAA approved revision." The AD also notes that "EASA AD 2008-0113 dated 10 June 2008 refers."

Beyond these dated references, the AD itself does not contain an internal amendment history, nor does it record any prior versions of the AD, corrections, or subsequent amendments. The phrase "or later NAA approved revision" in the Requirement section is the only text that directly contemplates future revisions of the ASB. That language creates a mechanism whereby future ASB revisions, if approved by the relevant NAA, may be used to comply with the AD. The AD does not specify whether later ASB revisions automatically become acceptable or whether CASA will issue a separate AD to accept them; it simply authorises use of a later ASB that has NAA approval.

The AD also cross-references EASA AD 2008-0113, dated 10 June 2008, but does not indicate any temporal dependency beyond that reference. The effective date of this AD is specified as 31 July 2008, and the ASB cited is dated 14 April 2008. The AD text does not include subsequent amendments to the AD itself, nor does it show any rescissions or supersessions. The AD also permits the FLM amendment to be accomplished by inserting a copy of this AD into the FLM, which creates a documentary record for operators, but the AD does not set retention or update rules for that inserted copy.

Practitioners should therefore treat the AD as a single-issue instrument with a narrow documented provenance, and as one that anticipates but does not itself manage future technical revisions via the "later NAA approved revision" clause. Any later changes to the AD, or any formal amendment or rescission, are not reflected in the supplied text.

The supplied AD text contains no litigation history. It does not reference judicial decisions, appeals, or legal challenges to its issuance or to the manufacturer's ASB. The document is administrative in nature, signed by a CASA delegate, and dated 20 June 2008 with an effective date of 31 July 2008. There are no references in the text to court proceedings, tribunal determinations, or litigation outcomes.

Given the absence of any litigation material in the AD, practitioners should not infer from this document that litigation has or has not occurred. The AD itself records reported safety incidents as background fact: "There have been several cases reported where take-off was executed with a locked cyclic stick," and it links those reports to a hazard assessment that motivated the modification. However, those reported safety occurrences are not presented as legal disputes or the subject of litigation in this AD text.

For those requiring a record of any contested enforcement actions, appeals, or legal interpretations related to AD/EC 135/18, this document does not supply that information. Any such litigation would need to be sourced from administrative records, court files, or regulatory correspondence outside the AD text, because the AD contains no litigation references, case names, or adjudicative outcomes.

Several practical and legal "gotchas" arise from the AD's specific wording, timing and documentary requirements. These points are grounded in the text of the AD and affect compliance planning.

1. Narrow applicability with enumerated exclusions. The AD covers EC135 and EC635 helicopters "S/N 0005 through 0699 inclusive" but excludes an explicit list of serial numbers. Operators must check the exact airframe serial against the AD text. Failure to check could lead to unnecessary work where a particular airframe is already excluded, or conversely to non-compliance where an airframe within the range is overlooked.

2. Short compliance window. The AD requires compliance "within 30 days after the effective date of this AD." The AD's effective date is specified as 31 July 2008, which produces a brief mobilisation period. Operators must schedule maintenance, source the ASB and any parts, and effect the FLM amendment within that window unless they secure an alternative arrangement through the regulator. The AD contains no extension mechanism in its text.

3. Method of compliance is the manufacturer's ASB or a later NAA approved revision. The AD mandates compliance "in accordance with ECD Alert Service Bulletin (ASB) EC135-67A-015 dated 14 April 2008, or later NAA approved revision." That creates two potential pitfalls. First, operators must ensure they follow the precise ASB edition cited, or obtain and verify that any later ASB revision has the necessary NAA approval. Second, if the operator attempts to use a different method of effecting the same mechanical change, the AD does not provide an explicit route within its text for accepting alternative compliance methods.

4. Flight Manual amendment form options. The AD permits the FLM amendment "by inserting a copy of this AD into the FLM, or by FLM page(s) supplied by ECD." Operators must ensure whichever method they choose complies with their own documentation control rules and with any oversight expectations, because the AD limits acceptable formats to those two choices and reproduces the required wording.

5. Change in operational practice. The AD states that, after modification, "a locking of the cyclic stick is no longer possible" and that the cyclic "can only be centered in its neutral position." The FLM note mandates moving the cyclic to neutral "Before starting the engines." This alters pre-start procedures that crews may previously have relied on. Operators must ensure training, briefings and standard operating procedures are updated to reflect the new centring method, and that any ground handling practices that previously depended on a lock are revised.

6. Coordination with other regulator instruments. The AD explicitly refers to "EASA AD 2008-0113," and permits later ASB revisions only if they are "NAA approved." Operators that operate across jurisdictions must ensure the methods and approvals they rely upon match both CASA's AD and any EASA or other NAA requirements applicable to their operations.

7. No penalties text or alternative compliance pathway in the AD itself. The absence of explicit enforcement, penalty, or alternative compliance language in the AD requires operators to approach the regulator for clarifications or formal concessions. That absence is a procedural risk if an operator cannot meet the 30 day deadline.

8. Record evidence implicit, not explicit. The AD requires insertion of the AD or ECD-supplied FLM pages, but does not specify maintenance log entries or certificate notations. Operators should not assume that insertion alone constitutes the full record of compliance for oversight purposes.

Those items are directly traceable to the AD's language and should be checked against an operator's own compliance management system before performing the work.

The AD prescribes two specific compliance steps and a timeframe, and it allows limited options for documentary compliance. To comply with the AD as written, an operator should take the following concrete actions, informed by the AD text.

1. Confirm applicability. Verify the helicopter model and serial number. The AD applies to "Eurocopter Deutschland (ECD) GmbH EC135 and EC635 series helicopters, all models, serial number (S/N) 0005 through 0699 inclusive," excluding the listed S/Ns. Confirm the airframe is not one of the excluded serial numbers before proceeding.

2. Obtain the required ASB. Acquire ECD Alert Service Bulletin EC135-67A-015 dated 14 April 2008. The AD mandates modification "in accordance with" that ASB or "later NAA approved revision." If a later ASB revision exists, confirm it is NAA approved before relying on it.

3. Schedule and perform the mechanical modification. Arrange for maintenance personnel to "remove the slide and spring from the cyclic stick cantilever" following the ASB procedures. The AD does not provide step-by-step instructions itself; it requires use of the ASB as the procedural standard. Ensure the modification is performed within the compliance window, which is "within 30 days after the effective date of this AD," the effective date being 31 July 2008.

4. Amend the Rotorcraft Flight Manual. Insert the exact FLM note required by the AD. The AD provides the text to be inserted: "NOTE: Before starting the engines, the cyclic stick must be moved to its neutral position. By folding up the cantilever to the pin, it is possible to move the cyclic stick into its neutral position and to centre it. A locking of the cyclic stick is no longer possible." The AD permits accomplishment "by inserting a copy of this AD into the FLM, or by FLM page(s) supplied by ECD." Choose the form that aligns with the operator's documentation control procedures and ensure the FLM amendment is authorised and recorded.

5. Document and retain evidence of compliance. Although the AD does not detail required record-keeping, best practice flowing from the AD text is to retain copies of: the ASB used, maintenance work orders showing removal of the slide and spring, the updated FLM with the AD or ECD pages inserted, and any sign-offs by certificated maintenance personnel. Because the AD specifies permitted FLM amendment methods, retain the inserted AD copy or the ECD-supplied pages as documentary proof.

6. Ensure crew awareness and procedure updates. The FLM note mandates a pre-engine-start action. Ensure flight crews are briefed and SOPs are updated so that the new centring technique is practised and understood, consistent with the FLM amendment required by the AD.

7. Check for applicable NAA or EASA cross-requirements. The AD refers to EASA AD 2008-0113 and conditions later ASB revisions on NAA approval. If the operator is subject to multiple jurisdictions, confirm whether additional or concurrent obligations apply under those other instruments.

8. If compliance within 30 days is not practicable, seek clarification from the regulatory authority. The AD does not provide an in-text mechanism for time extensions or alternative compliance approaches, therefore any requested variation should be obtained from the issuing authority or the appropriate NAA. Any such agreement should be in writing and documented alongside the AD compliance records.

The AD leaves certain administrative aspects to outside processes, for example the ASB revision approval process and any regulatory acceptance of alternative methods. Operators should not assume flexibility beyond what the AD explicitly permits, and should secure any necessary approvals from regulators or manufacturers before departing from the AD's stated requirements.