AD/CESSNA 337/31 - Alternate Static Air Source Selector Valve Placard

The core mechanical concept is obstruction of an alternate static air source selector valve port by the valve’s part‑number identification placard. That obstruction can impede the alternate static air source, which is used to provide static pressure for pitot/static instruments when the primary static source is compromised. The AD identifies the immediate operational hazard: obstructed static ports can lead to erroneous altimeter, airspeed and vertical speed indications (Background).

Operationally the AD differentiates between aeroplanes that are IFR‑equipped and those that are not. For non‑IFR aeroplanes, the AD simply requires inspection to confirm the port is unobstructed (Requirement 1). For IFR‑equipped aeroplanes, the AD offers a two‑path approach: either inspect immediately (Requirement 2a) or, before further flight, install an instrument‑panel placard that prohibits IFR operation and use of the alternate static source (Requirement 2b). If an operator takes the placard option, the AD then requires the valve inspection within the longer window (Requirement 3), and instructs removal of the temporary instrument‑panel placard after the inspection is done and before further flight (Requirement 3).

The AD also sets a forward‑looking installation rule: as of 10 days after the AD’s effective date, replacement installation of P/N 2013142‑18 valves is allowed only if the valve has been inspected and the port found free from obstruction (Requirement 5). The AD points users to the Cessna service bulletins that “detail the procedures required to accomplish this AD” (Service Bulletin references).

From a regulatory mechanism viewpoint, the AD uses short, enforceable deadlines: 10 days for immediate inspection for IFR aircraft selecting inspection; 100 hours TIS or 4 months for broader inspections; “before further flight” for actions where an obstruction is found. These deadlines create immediate work allocation decisions for operators, maintenance providers and spare parts managers.

Testing the official rationale against practical trade‑offs in the source: the stated purpose is to prevent instrument misreading caused by port obstruction. The AD’s remedies are straightforward, low‑technology (visual inspection; placard removal; temporary instrument‑panel placard), and leverage the manufacturer’s service bulletins for standardised procedures. The AD recognises uncertainty in the distribution of affected valves , the Background explicitly notes CASA “has no way of determining which aeroplanes have the remaining problem ... installed without having all of the affected aeroplanes and spares stock inspected.” That uncertainty is the reason for the broad applicability criteria and the requirement to inspect spares on installation (Requirement 5).

Costs and incentives signalled in the source: the immediate costs fall on operators and maintenance organisations who must inspect aircraft and spare parts stocks within the specified windows. Time pressure is greater for IFR‑equipped aeroplanes (10 days for Requirement 2a) and for removal of placards where obstruction is found (“before further flight”). The AD channels behaviour by (a) requiring a rapid inspection, (b) allowing a temporary operational limitation for IFR flights via a specific placard if immediate inspection is not feasible, and (c) forbidding installation of replacement valves unless they have been inspected. These measures create incentives to inspect existing stock promptly, and discourage uninspected installation of replacement parts. The AD also substitutes a low‑cost operational restriction (temporary placard) where immediate inspection would otherwise ground an aircraft, creating a practical compliance path for operators who need to manage flight schedules pending inspection.

Implementation risk and compliance complexity are visible in the source: the need to inspect both in‑airframe parts and spares stock, the replacement of multiple previous P/Ns by P/N 2013142‑18 (Note 2), and the series of applicable service bulletins across single‑engine, multi‑engine and Caravan lines. The AD centralises the technical procedures to those service bulletins but does not reproduce step‑by‑step maintenance actions within the AD text beyond the inspection and placard requirements.

The AD applies to owners, operators, maintenance organisations and parts stock holders associated with the Cessna 337 family listed in Table 1. The Applicability section specifies the scope: aeroplane models listed in Table 1 that either (1) “were initially delivered from the manufacturer between 1 January 1993, and 31 March 2008; or (2) have a P/N 2013142‑18 installed as a replacement part anytime after 1 January 1993.” Table 1 enumerates numerous model variants of the 337 family (for example 337, 337A, 337B, 337C, 337D, 337E, 337F, F337G, F337F, T337 series and others). Note 1 clarifies the affected parts were shipped from Cessna Parts Distribution between 1 January 1993 and 31 March 2008. Note 2 states that P/N 2013142‑18 replaced earlier P/Ns 2013142‑9, ‑13, and ‑17.

Concrete groups who must act, as required by the AD text, include:

• Aeroplane owners and operators of the Table 1 models meeting the delivery date or replacement P/N criteria.
• Maintenance personnel who will perform the inspections of the alternate static air source selector valve and make any necessary removals or replacements.
• Organisations that hold spares stocks or replacement valves (Cessna Parts Distribution customers, maintenance shops, parts suppliers), because the Background notes the affected valves may exist in spares stock and CASA cannot easily determine where they remain without inspection.
• Pilots and operators of IFR‑equipped aeroplanes in the affected set, because Requirement 2 creates an immediate operational condition they must follow (inspect the valve or install the temporary instrument‑panel placard that prohibits IFR operation and use of the alternate static source).
• Any party installing replacement valves after the effective date, because Requirement 5 conditions that installation on prior inspection and a clear port.

The source emphasises uncertainty about precise distribution of affected components: “CASA has no way of determining which aeroplanes have the remaining problem alternate static air source selector valve assemblies installed without having all of the affected aeroplanes and spares stock inspected.” That statement explains why the AD’s applicability is broad and why spares holders are implicated: the risk is not limited to a fixed fleet but to parts in circulation.

The AD also affects operational choices. For IFR‑equipped aeroplanes, until the inspection is carried out, operators must either accept the short‑term safety restriction via the instrument‑panel placard or execute an immediate inspection within the 10‑day window for Requirement 2a. If the placard route is taken, the AD requires removal of the temporary placard after inspection and before further flight (Requirement 3). The AD therefore affects scheduling, maintenance planning, and potentially the availability of aeroplanes for IFR flights.

Finally, the AD interacts with manufacturer instructions: the procedures are to be completed “as detailed in” specified Cessna service bulletins. Holders of those aeroplanes must therefore engage with the service bulletin content to carry out the AD’s mandated corrective actions.

Duties under the AD are explicit and prescriptive. The AD sets out five main required actions:

1. Inspection of the alternate static air source selector valve for aeroplanes not equipped for IFR: “Inspect the alternate static air source selector valve to assure that the part number identification placard is not obstructing the port” (Requirement 1). The compliance window for Requirement 1 is “within the next 100 hours TIS after the effective date of this AD or within the next 4 months … whichever occurs first” (Compliance).

2. For aeroplanes equipped for IFR, a two‑option duty: a. Inspect the selector valve to assure the placard is not obstructing the port (Requirement 2a), with an accelerated compliance window: “Within the next 10 days after the effective date of this AD” (Compliance); or b. Fabricate and install, on the instrument panel within the pilot’s clear view, a placard in at least 1/8‑inch letters stating: “IFR OPERATION IS PROHIBITED” and “USE OF THE ALTERNATE STATIC AIR SOURCE IS PROHIBITED.” This placard must be installed “before further flight after the effective date of this AD” (Requirement 2b, Compliance).

3. If the temporary instrument‑panel placards were used (Requirement 2b), inspect the selector valve within the longer window (Requirement 3 , “within the next 100 hours TIS … or within the next 4 months … whichever occurs first”), and then “remove the placards installed in accordance with Requirement 2b of this AD before further flight” after the inspection (Requirement 3).

4. If the selector valve port is found obstructed by the part number identification placard during any inspection called for in Requirements 1, 2a or 3, remove and discard the placard and “assure that the port is open and unobstructed” before further flight (Requirement 4).

5. On installation of any replacement valve after the AD’s effective date: “When a replacement valve is needed, only install a P/N 2013142‑18 alternate static air source selector valve that has been inspected and the port is found free from obstruction” (Requirement 5). The Compliance column states this is effective “as of 10 days after the effective date of this AD.”

Procedural duty: the AD requires operators to follow the procedures detailed in the specified Cessna service bulletins (SB08‑34‑02 Rev 1; CAB08‑04 Rev 1; SEB08‑5; MEB08‑6) “as applicable” to accomplish the AD (Service Bulletin reference). These service bulletins are incorporated by reference as the procedural method for compliance.

Rights: the AD does not enumerate rights or appeal processes within the text provided. It establishes mandatory technical duties and specified compliance windows. The AD provides an explicit operational option for IFR‑equipped aeroplanes (the two‑path choice in Requirement 2), which functions as a limited procedural right: operators may elect an immediate placard mitigation to permit near‑term operations while scheduling the detailed inspection within the longer window. The AD also effectively affords the right to install replacement valves only after they have been inspected , a preventive duty placed on installers to ensure compliance.

Timing duties are precise: the AD uses both calendar (within 10 days; within 4 months) and operational (within 100 hours TIS; before further flight) deadlines. Those deadlines allocate inspection work and parts checks between operators and maintenance organisations within narrow windows. The AD places an affirmative obligation to remove obstructing placards when found, and to discard them, making the cure physically definitive.

Procedural source reference duties: operators must use the manufacturer’s service bulletins to execute the inspections and removals; the AD does not delegate alternative approved methods within the text.

In short, the AD imposes short‑term inspection, temporary operational limitation or immediate inspection for IFR aircraft, removal of obstructing placards, and a restriction on installation of replacement valves unless inspected.

The AD text itself does not set out monetary penalties, enforcement procedures, or specific sanctions for non‑compliance. What the AD does provide are mandatory actions with explicit compliance timelines (for example: “Within the next 10 days …”; “before further flight …”; “as of 10 days after the effective date …”), and the AD is issued by the Civil Aviation Safety Authority and signed by its delegate (James Coyne). The document therefore functions as a binding regulatory instrument within CASA’s airworthiness regime, but the AD does not within its text describe the enforcement tools CASA will use or the sanctions available for non‑compliance.

The AD uses operational‑status language that directly affects flight permissibility, e.g. requirements that certain corrective steps be completed “before further flight” or that a temporary instrument‑panel placard prohibiting IFR operation be fitted where the immediate inspection path is not taken (Requirements 2b and 3). Those phrases create immediate operational conditions: aircraft cannot be returned to IFR flight until the AD’s inspection and removal requirements have been satisfied in the prescribed sequence. The AD therefore functions as an operational constraint; parties reading the AD should expect that non‑adherence to those operational constraints will at minimum make an aircraft non‑conforming with the AD.

Because the AD is a CASA instrument, enforcement and penalties (if invoked) would be administered by CASA under the aviation statute and regulations governing civil aviation safety and airworthiness. Those statutory enforcement tools and penalties are not described in the AD text provided here. The AD does cross‑reference FAA action (FAA AD 2008‑10‑02 and FAA AD 2008‑26‑10 Amdt 39‑15776), signalling coordination with another regulator; the FAA ADs themselves would be enforced under FAA rules in the United States.

Practical enforcement consequences flowing from the AD’s language, as stated in the source, include:

• Immediate work allocation: if the port is found obstructed, the remedial action must be completed “before further flight,” which operationally prevents typical flight activity until maintenance has removed the obstruction and verified the port is clear (Requirement 4).
• Immediate inspection obligations for IFR‑equipped aeroplanes choosing the inspection route: “within the next 10 days” creates a short enforcement window (Requirement 2a).
• Installation restrictions: as of 10 days after the effective date, installation of replacement valves is conditioned on prior inspection and a clear port (Requirement 5), which effectively places a compliance gate on installing spare valves.

Lawyers and compliance officers using this AD should therefore treat the AD’s deadlines as mandatory technical obligations to be scheduled into maintenance planning, and recognise that the AD’s “before further flight” and “as of” language operates as an immediate operational constraint. The AD, however, does not itself describe the penalties that CASA will apply for failure to comply; that information resides outside the AD text in CASA’s enforcement framework and the applicable aviation statute and regulations.

The AD explicitly situates itself in international regulatory coordination. The Background states the AD was issued “in response to the United States Federal Aviation Administration (FAA) issuing AD 2008‑10‑02.” The AD also notes that FAA AD 2008‑26‑10 Amdt 39‑15776 dated 15 December 2008 is referred to in Note 3. The AD therefore functions as CASA’s corresponding directive aligned with FAA action, and directs compliance with procedures identified in Cessna service bulletins that have been issued to address the same hardware issue.

Operationally it also interfaces with rules governing instrument flight. The AD’s remedial option for IFR‑equipped aeroplanes is to install an instrument‑panel placard stating “IFR OPERATION IS PROHIBITED” and “USE OF THE ALTERNATE STATIC AIR SOURCE IS PROHIBITED.” That placard, when installed, explicitly suspends IFR operation and use of the alternate static source until such time as the inspection occurs and the temporary placard is removed in accordance with Requirement 3. The AD therefore imposes a direct interaction between its safety remedy and the aircraft’s operational privileges under IFR: it requires either immediate inspection to restore the IFR capability or a temporary restriction in the form of a visible placard. The AD itself does not amend IFR flight rules or licences; it creates a mandatory maintenance/airworthiness condition that affects whether the aeroplane may be safely operated under IFR.

The AD mandates compliance with manufacturer service bulletins (SB08‑34‑02 Rev 1, CAB08‑04 Rev 1, SEB08‑5, MEB08‑6), which are the prescribed technical procedures “to accomplish this AD.” Those service bulletins are part of the compliance chain: the AD requires they be followed as applicable. This places the AD squarely within the usual interaction between regulator ADs and manufacturer service instructions, where the AD prescribes both the corrective outcome and the procedural references for accomplishing it.

Because the AD references FAA ADs and Cessna service bulletins, operators who operate internationally or under multiple jurisdictions will need to reconcile the CASA AD with those other instruments. The AD’s explicit references suggest it is intended to harmonise CASA obligations with the FAA action and the manufacturer’s remedies.

The AD also interacts with parts management and maintenance practice: Note 1 and Note 2 highlight that the affected P/Ns were shipped across a specific period and that P/N 2013142‑18 replaced older P/Ns. The AD therefore intersects with obligations to inspect and manage spares stocks and to prevent uninspected spares from being installed. Hence it has downstream effects on procurement and parts‑installation decisions. The AD’s Requirement 5 conditions future installations on inspection, which creates a procedural interaction between parts suppliers, maintenance organisations and the AD.

The AD text does not quote or rely on other domestic statutory provisions; it is an instrument of CASA. The AD does not include the enforcement statutes that CASA would use to pursue non‑compliance , those remain external to the document. Any legal action for non‑compliance or aviation enforcement would be conducted under the applicable civil aviation statute and CASA’s enforcement framework, which are not reproduced in the AD text.

The AD document itself records a specific issuance and effective date: “This Airworthiness Directive becomes effective on 16 January 2009” and bears the signature of James Coyne, Delegate of the Civil Aviation Safety Authority, dated 8 January 2009. The AD references FAA ADs and Cessna service bulletin versions, which supply the contemporaneous technical update history relevant to the remedy.

Service‑bulletin history quoted in the AD:

• Cessna Single Engine Service Bulletin SB08‑34‑02, Revision 1, dated 6 October 2008;
• Cessna Caravan Service Bulletin CAB08‑04, Revision 1, dated 6 October 2008;
• Cessna Single Engine Service Bulletin SEB08‑5, dated 13 October 2008;
• Cessna Multi‑engine Service Bulletin MEB08‑6, dated 13 October 2008.

FAA AD references mentioned:

• The Background states the CASA AD was issued “in response to the United States Federal Aviation Administration (FAA) issuing AD 2008‑10‑02.”
• Note 3: “FAA AD 2008‑26‑10 Amdt 39‑15776 dated 15 December 2008 refers.”

The AD also includes contextual manufacturing/shipping dates for the affected part: Note 1 indicates the affected part “was shipped from Cessna Parts Distribution (CPD) between 1 January 1993 and 31 March 2008,” and Note 2 states “P/N 2013142‑18 replaced P/Ns 2013142‑9, ‑13, and ‑17.” Those manufacturing and P/N replacement details are part of the factual history that grounds the AD’s applicability.

The text provided contains no later amendments, revocations, or supersessions of the AD. The AD does not record any in‑text amendments subsequent to issue. If later CASA amendments exist, they are not included in the provided material. For the purpose of compliance and due diligence, operators should confirm whether CASA has issued any subsequent ADs, revisions or alternative methods of compliance since the effective date, but that verification is outside the AD text supplied here.

The AD text supplied does not record any litigation history. There are no cases, challenges, judicial reviews, or administrative appeals mentioned in the AD document. The AD is an administrative safety directive signed by a CASA delegate; any litigation arising from its operation would be external to the AD text and would need to be researched in court and tribunal records, which are not included in the provided material.

Because the AD does not include or reference any litigation, and names no case law, practitioners should treat the AD as a regulatory instrument whose legal footing and enforcement consequences are governed by CASA’s enabling legislation and enforcement regime. Any dispute about the AD’s scope, its technical prescriptions, or its application to a particular aircraft would be litigated or administratively reviewed outside the AD text and is not recounted here.

1. Applicability breadth and spare parts: Note 1 states the affected valves “were shipped … between 1 January 1993 and 31 March 2008.” Although the AD applies to aeroplanes delivered in that period, the Background emphasises that spares shipped during that time may still be in circulation and installed later. Requirement 5 therefore prohibits installing P/N 2013142‑18 replacement valves unless they have been inspected and the port was found clear. The practical implication and common trap is to assume only certain airframes are affected; in reality, spares pools, maintenance shops and parts inventories may conceal uninspected valves that can be installed later, contrary to Requirement 5.

2. Two‑path compliance for IFR‑equipped aeroplanes: For IFR‑equipped aircraft, there is an either/or in Requirement 2: inspect within 10 days (2a) OR install the temporary instrument‑panel placard (2b) before further flight. Some operators may misunderstand that the placard is a permanent fix. It is a temporary mitigation: Requirement 3 requires inspection within the longer 100‑hour/4‑month window and requires removal of the temporary instrument‑panel placard “before further flight” after the inspection. Installing the temporary placard therefore does not avoid the need for the substantive inspection; it only delays it while allowing limited operations subject to the placard’s restriction.

3. Letter size and exact placard wording: If operators choose the temporary placard under Requirement 2b, the AD prescribes text and minimum letter size: the placard must state the exact two phrases and use at least 1/8‑inch letters. Small deviations in wording or type size may cause non‑compliance because the AD specifies the text and letter size as the required temporary mitigation.

4. “Before further flight” sequencing: Several obligations are framed as required “before further flight” (Requirements 2b, 3, 4). Practically, that means if an obstruction is found, the aircraft must not depart until the obstruction has been removed and the port verified clear. Misinterpreting “before further flight” as a remedial deadline rather than an operational prohibition could lead to non‑compliant flights.

5. P/N replacement history: Note 2 explains that P/N 2013142‑18 replaced P/Ns 2013142‑9, ‑13, and ‑17. Technicians may mistakenly think only the older P/Ns are at issue; however the AD explicitly targets P/N 2013142‑18 and the shipping window. If maintenance logs only record the older P/Ns or the replacement, tracing the actual installed valve may require verification of historical maintenance records and parts invoices. Parts renumbering and cross‑references can be a source of identification error.

6. Timing mismatches across requirements: Requirement 2a calls for inspection “within the next 10 days,” whereas Requirements 1 and 3 permit “within the next 100 hours TIS or within the next 4 months … whichever occurs first.” Operators who delay must be careful which window applies to their aircraft and which requirement they are complying with; mixing up the windows will create non‑compliance.

7. Service bulletin applicability: The AD directs use of multiple service bulletins “as applicable” but does not reproduce the step‑by‑step method. A practical trap is to assume the AD’s inspection text is exhaustive; maintenance personnel must consult the referenced Cessna service bulletins to ensure the inspection and any verification testing are accomplished in the method the manufacturer prescribes.

8. Inspection vs. testing: The AD requires inspection “to assure that the part number identification placard is not obstructing the port.” Operators may need to interpret what constitutes a compliant inspection , visual confirmation, removal and reinstallation, or additional functionality testing. The AD points to service bulletins for the detailed procedures; following the service bulletin closely is essential to avoid divergence between the AD requirement and the maintenance execution.

9. Documentation: The AD does not specify logbook entries or paperwork in the text provided. Standard practice would be to document the inspection and any removals or replacements, but absence of explicit paperwork instructions in the AD can lead to inconsistent record‑keeping; regulators may expect records consistent with normal maintenance standards even if the AD text is silent.

10. Cross‑jurisdictional operators: Because the AD references and responds to FAA ADs, operators who fly internationally or operate under multiple national certifications should ensure their compliance satisfies both CASA and any other regulator’s ADs and service‑bulletin requirements. The AD’s references to FAA action suggest harmonisation, but differences in wording and timing could create confusion if not cross‑checked.

Follow a short, operational checklist anchored to the AD’s specific requirements and the cited Cessna service bulletins. The AD requires service‑bulletin procedures be used “as applicable,” so the procedural standard is the manufacturer’s SBs.

Step 1 , Identify affected assets:

• Determine whether the aeroplane model appears in Table 1 of the AD and whether it meets applicability criteria: initially delivered 1 January 1993-31 March 2008, or had a P/N 2013142‑18 installed as replacement after 1 January 1993 (Applicability; Note 1). Also note that P/N 2013142‑18 replaced earlier P/Ns (Note 2), so verify parts history for any renumbered or replaced valves.

Step 2 , Plan inspections against the AD’s deadlines:

• If the aeroplane is not IFR‑equipped, schedule inspection of the alternate static air source selector valve “within the next 100 hours TIS after the effective date of this AD or within the next 4 months … whichever occurs first” (Requirement 1; Compliance).
• If the aeroplane is IFR‑equipped, choose one of two paths: a. Inspect the selector valve port within 10 days of the AD effective date (Requirement 2a; Compliance); or b. If immediate inspection within 10 days is not practicable, fabricate and install an instrument‑panel placard (within the pilot’s clear view) stating the exact phrases “IFR OPERATION IS PROHIBITED” and “USE OF THE ALTERNATE STATIC AIR SOURCE IS PROHIBITED” in at least 1/8‑inch letters, and install it before further flight (Requirement 2b; Compliance). If 2b is used, the inspection is still required later within the longer window (Requirement 3).

Step 3 , Conduct the inspection per Cessna service bulletin:

• Use the procedures in the applicable Cessna service bulletin: SB08‑34‑02 Rev 1 (single engine), CAB08‑04 Rev 1 (Caravan), SEB08‑5 (single engine dated 13 Oct 2008), or MEB08‑6 (multi‑engine dated 13 Oct 2008). The AD specifies those SBs “detail the procedures required to accomplish this AD.” Do not rely solely on the AD’s short description; follow the SB step sequence and verification checks.

Step 4 , If obstruction found:

• Remove the part‑number identification placard from the valve body, discard it, verify the port is open and unobstructed, and complete any verification procedures in the service bulletin before further flight (Requirement 4). Record the removal and verification in the aircraft’s maintenance records according to standard maintenance practice and to the service bulletin instructions if they prescribe documentation steps.

Step 5 , If temporary instrument‑panel placard was installed (IFR path 2b):

• After performing the inspection required by Requirement 3 (within 100 hours TIS or 4 months), remove the temporary instrument‑panel placard before further flight (Requirement 3). Ensure the removal is accompanied by verification that the valve port is clear per the service bulletin.

Step 6 , Replacement valve installations:

• Effective as of 10 days after the AD effective date, do not install any P/N 2013142‑18 alternate static air source selector valve unless that valve has been inspected and the port is found free from obstruction (Requirement 5). For installers: inspect any replacement valve prior to installation and retain evidence of inspection in parts and maintenance records. This prevents reintroducing the hazard via spares.

Step 7 , Inspect spares inventory and supplier flows:

• Given Note 1’s shipping window for the affected part and the AD’s statement that CASA cannot identify which aeroplanes or spares are affected without inspection, operators and maintenance organisations should inspect spare valves in stock prior to installation and implement a parts‑control hold on any P/N 2013142‑18 items until they are inspected.

Step 8 , Document compliance and follow service‑bulletin reporting:

• The AD requires the procedures in the Cessna service bulletins; those SBs often include instructions for maintenance log entries and possible manufacturer reporting. Ensure maintenance records reflect the inspection date, findings (no obstruction/found and removed), any placards fabricated or removed, and any parts installed or discarded. Maintain records to demonstrate compliance with the AD’s deadlines (10 days, 100 hours, 4 months, before further flight, as of 10 days).

Step 9 , Operational coordination:

• For IFR‑equipped aeroplanes choosing the placard path, communicate to flight crews the temporary IFR prohibition and the prohibition on use of the alternate static source. Update checklists and operational briefings so pilots are aware the aeroplane must not be operated under IFR until the inspection has been completed and the placard removed in accordance with Requirement 3.

Step 10 , Cross‑check with FAA and manufacturer communications:

• Because the AD was issued in response to FAA AD 2008‑10‑02 and refers to FAA AD 2008‑26‑10 Amdt 39‑15776, consult those FAA AD texts and the Cessna service bulletins cited, to ensure the maintenance actions follow the full procedural method and any FAA‑prescribed measures are reconciled where operations are multinational.

Practical compliance notes drawn from the AD text:

• The AD gives clear deadlines; treat “within the next 10 days” and “before further flight” as mandatory scheduling constraints.
• Use the precise placard wording and minimum letter size when relying on the temporary mitigation for IFR‑equipped aircraft.
• Discard any obstructing part‑number placard removed from the valve body (Requirement 4).
• Restrict installation of replacement P/N 2013142‑18 valves unless inspected and clear (Requirement 5) , inspection of spares prior to installation is required by implication of that requirement.

This AD places primary compliance responsibility on the aircraft owner/operator and the maintenance organisation to schedule and execute inspections and remedial actions in the specified windows, and to follow the Cessna service bulletins for the detailed maintenance method.