AD/CESSNA 400/118 - Auxiliary Wing Spars

The AD’s principal technical concept is targeted structural inspection for fatigue cracking on an auxiliary wing spar in the landing gear trunnion area. The AD treats fatigue cracking as a degradation process that can be detected visually, measured, tracked and, if necessary, addressed by part replacement. The directive is premised on reported occurrences of fatigue cracking on Models 402A and 402B (Background), and on the safety consequences of a spar web failure , landing gear collapse during normal landing, leading to potential loss of control and passenger injury (Background).

Key operational concepts embedded in the text:

• Applicability by model and serial number: the AD names specific Model 401, 401A, 401B, 402, 402A and 402B aircraft and enumerates serial number ranges (Applicability). Compliance obligations attach only to aircraft within those serial number ranges. The source explicitly lists extensive serial number blocks and, notably, includes single or out‑of‑range identifiers such as "serial numbers 655 and 401‑0001 through 401‑0322" for Model 401 (Applicability). Users must read the serial‑number list precisely to determine applicability.

• Inspection protocol linked to an external document: the visual inspection must be "in accordance with Cessna Service Bulletin MEB08‑8 original issue, or later FAA approved revision" (Requirement). The AD therefore delegates the detailed inspection technique, access, and any illustration to that Service Bulletin or its FAA‑approved revisions, rather than reproducing those details in the AD text.

• Measurable action thresholds and timelines: the AD sets a clear measurable crack length threshold (0.5‑inch) requiring immediate replacement before further flight, and a monitoring regime for cracks below that length (repetitive inspections at intervals not exceeding 50 hours time in service, replacement if the crack reaches 0.50‑inch, and mandatory replacement within 200 hours time in service or 12 months after detection, whichever occurs first) (Requirement).

• Trigger events for inspection: the AD sets an initial time window (within 10 hours TIS after 2 March 2009, unless already done) and an event‑based trigger ("before further flight anytime the aircraft experiences a hard landing") (Compliance). Thus compliance is both time‑driven and condition‑driven.

• Reporting requirement to manufacturer: if cracks are detected during any inspection, results must be reported to Cessna within 10 days after the inspection, or within the next 10 days after 2 March 2009 (Requirement). The AD treats reporting as a separate mandatory step.

• Distinction between spar caps and webs: Note 1 explicitly states that "Supplemental Inspection Numbers 57‑10‑09 and 57‑10‑13 of the Cessna 401/402 Supplemental Inspection Document (SID) inspect the auxiliary spar caps, but not the webs. Hence, this Airworthiness Directive applies even to SID‑compliant aircraft." This clarifies that existing SID compliance does not satisfy the AD because the AD inspects the web area, not the caps.

• Reference to other authorities/ADs: Note 2 points to FAA AD 2009‑04‑04 Amdt 39‑15810, indicating the AD aligns with or follows an FAA counterpart.

Those concepts together create a prescriptive inspection, record, and repair regime tied to specific aircraft and parts, an external service bulletin, numeric thresholds, and reporting to the manufacturer.

Primary affected parties are defined precisely in the Applicability and Compliance paragraphs:

• Owners and operators of the listed aircraft models and serial numbers. The AD lists Model 401, 401A, 401B, 402, 402A and 402B aircraft, with detailed serial number ranges (Applicability). For example, for Model 402B the AD lists multiple non‑contiguous serial ranges including 402B0001 through 402B0122, 402B0201 through 402B0249, and further ranges up to 402B1384. Owners/operators must check each aircraft serial number against that list to determine whether the AD applies.

• Maintenance organisations and technicians responsible for inspections and repairs. The AD requires visual inspection "in accordance with Cessna Service Bulletin MEB08‑8 original issue, or later FAA approved revision" (Requirement). Execution therefore implicates the organisations that carry out scheduled maintenance and the technicians who must follow the Service Bulletin procedure.

• Parts suppliers and overhaul/repair facilities. Where cracks are detected, replacement is required either immediately (if 0.5‑inch or more) or within specified time‑in‑service or calendar time windows for smaller cracks. This creates demand for replacement parts and potential workload for repair facilities.

• Cessna Aircraft Company as recipient of mandatory reports. The AD requires reporting detected cracks "to the Cessna Aircraft Company" within specified times (Requirement). Cessna is therefore a direct addressee of field data and will receive concentrated informational benefit.

• The regulator (Civil Aviation Safety Authority) and its delegate who issued the AD. The AD is signed by "David Villiers, Delegate of the Civil Aviation Safety Authority" and becomes effective on 2 March 2009. The regulator is the issuing authority and will be involved in oversight and potentially in any enforcement processes arising from non‑compliance, though the AD text does not itself specify enforcement penalties.

Indirectly affected parties include passengers and insurers. Structural failures cited in the Background (failure of the auxiliary spar web causing landing gear collapse, potentially leading to loss of control and passenger injury) indicate safety‑critical implications. Insurers and commercial operators may factor the AD into operational risk assessments, insurance valuations, and maintenance budgets.

Finally, aircraft that have complied with the Cessna 401/402 Supplemental Inspection Document (SID) may nonetheless be subject to this AD because the SID inspects spar caps but not spar webs (Note 1). Maintenance managers must therefore not assume SID compliance obviates the AD.

The AD sets out explicit duties and procedural rights tied to detection thresholds, timing, inspection standards, replacements and reporting. The text supplies the duties; there are no express statutory "rights" enumerated in the AD text beyond the option to follow later FAA‑approved revisions of the referenced service bulletin.

Primary duties:

• Duty to inspect: Operators of applicable aircraft must "visually inspect the auxiliary wing spar near the location where the main landing gear trunnion is mounted, for cracks; in accordance with Cessna Service Bulletin MEB08‑8 original issue, or later FAA approved revision." This is a procedural duty to follow an external document for inspection details (Requirement).

• Duty to comply with initial timing: The initial inspection must be completed "within 10 hours time in service after 2 March 2009, unless already accomplished" (Compliance). Additionally, the aircraft must be inspected "before further flight anytime the aircraft experiences a hard landing" (Compliance). These duties establish a short time‑in‑service window for first inspection and an event‑driven duty after hard landings.

• Duty to replace immediately if crack ≥ 0.5‑inch: The AD mandates that "before further flight, replace the cracked part(s)" where any crack detected during inspection is 0.5‑inch or more (Requirement). This creates an operational grounding for the affected aircraft until replacement is performed.

• Duty to monitor and replace for cracks < 0.5‑inch: If cracks under 0.5‑inch are detected, operators must "repetitively inspect the crack(s) for length at intervals not to exceed 50 hours time in service and, before further flight, replace any part that has a crack with a length of 0.50‑inch or more; and, replace the cracked part within 200 hours time in service after the original crack was detected, or within 12 months after the original crack was detected, whichever occurs first." This sequence imposes an on‑going inspection duty and a replace‑by ceiling.

• Duty to report: "If cracks are detected during any inspection, report the results to the Cessna Aircraft Company at whichever of the following occurs later: Within 10 days after the inspection is accomplished; or, Within the next 10 days after 2 March 2009." This creates a time‑bounded information transfer duty to the manufacturer.

• Duty to use the Service Bulletin or later FAA‑approved revision: The AD requires following Cessna Service Bulletin MEB08‑8 original issue or later FAA‑approved revision. That gives operators a single authorised inspection method and implicitly a process for accepting later changes if approved by the FAA.

Rights and procedural options evident from the text:

• Option to follow later FAA‑approved revisions of the Service Bulletin: The AD allows compliance with "later FAA approved revision" of MEB08‑8, which provides an operator pathway to comply using updated, FAA‑approved guidance issued after the original Service Bulletin. This is a procedural right to use updated methodology where FAA approval exists.

• No derogation of SID compliance: The AD makes explicit that compliance with certain SID inspections (Supplemental Inspection Numbers 57‑10‑09 and 57‑10‑13) does not negate the AD requirement because the SID inspects caps not webs. This reduces potential ambiguity for operators who might otherwise claim SID compliance sufficed.

What the AD does not state as rights or duties:

• The AD text does not specify enforcement penalties, record‑keeping durations, or certifier responsibilities beyond following the Service Bulletin and reporting detected cracks to Cessna. The regulator who issued the AD is identified, but no enforcement mechanisms are set out in the document itself.

• The AD does not set out who pays for parts or for the labour to carry out inspections and replacements; those costs flow from the duties to replace and inspect but are not expressly allocated in the AD text.

In summary, the AD imposes time and event‑driven inspection duties, clear replacement triggers, a finite replacement deadline for smaller cracks, and a reporting duty to Cessna, and it allows compliance by following the listed Service Bulletin or an FAA‑approved update.

The AD text itself does not specify criminal, civil or administrative penalties, nor does it describe enforcement processes or sanctions for non‑compliance. The document states the effective date ("This Airworthiness Directive becomes effective on 2 March 2009") and is signed by a Delegate of the Civil Aviation Safety Authority, but contains no express penalty provisions, infringement fines, or enforcement mechanisms within the body of the AD as provided.

What the AD does set out that has enforcement implications in practice:

• Mandatory nature and effective date: The AD "becomes effective on 2 March 2009" and prescribes duties with precise time limits (for example, initial inspection "within 10 hours time in service after 2 March 2009," replacement deadlines for cracks). The existence of an effective date and mandatory actions signals that compliance is expected from that date forward.

• Operational grounding implied by "before further flight" language: Several requirements use the phrase "before further flight" (for example, "If any crack ... is 0.5‑inch or more, before further flight, replace the cracked part(s)"). Such phrasing commonly functions to require remediation before the aircraft may be flown again; the AD text itself uses that term as a condition to be satisfied prior to flight.

• Reporting to the manufacturer: The AD requires the reporting of detected cracks to Cessna within 10 days after inspection or within the next 10 days after 2 March 2009. Timely reporting creates an auditable line of compliance that regulators or the manufacturer could use to assess whether operators are meeting their obligations.

Absent explicit penalties in the text, readers must rely on the issuing authority and the broader regulatory framework outside the AD to determine consequence mechanisms. The AD identifies the Civil Aviation Safety Authority's delegate as the issuer but provides no further enforcement detail in the provided document. The AD references an FAA AD (Note 2) but does not import any FAA penalty language into the text.

Practical enforcement points to note based strictly on the text:

• Non‑compliance can be detected via failure to produce inspection records, absence of required replacement following a crack measurement, or failure to report to Cessna within the prescribed window. The AD prescribes measurable actions and reporting which create discrete compliance markers.

• The AD’s "before further flight" replacement requirement functions as an operational stop‑gap; physically, non‑compliant aircraft carrying a crack at or above the threshold would contravene the explicit "before further flight" condition. The text does not, however, state who or how "before further flight" is to be audited or authorised.

• There is no schedule of fines, licence suspensions, or civil liabilities in the AD text. Any sanctioning or enforcement pathway would therefore rely on CASA’s broader enforcement instruments or other aviation safety regulatory provisions outside this document, none of which are reproduced in the text provided.

In short, the AD lays down mandatory actions and reporting but does not itself specify penalties or an enforcement regime; the consequences of non‑compliance are therefore not described in the supplied text.

The AD explicitly cross‑references external technical and regulatory instruments and clarifies its relationship to at least one manufacturer document and one other airworthiness directive. Those cross‑references determine how compliance obligations interact with pre‑existing inspection regimes.

Document interactions expressly stated in the text:

• Cessna Service Bulletin MEB08‑8: The required inspection is to be carried out "in accordance with Cessna Service Bulletin MEB08‑8 original issue, or later FAA approved revision." This means the AD does not reproduce the detailed inspection technique; it delegates the procedural specifics to the service bulletin and effectively makes that bulletin part of the compliance pathway. Operators must therefore consider both the AD and the Service Bulletin together: the AD sets what must be done, and the Service Bulletin sets how to do it, unless a later FAA‑approved revision modifies the process.

• Cessna 401/402 Supplemental Inspection Document (SID): Note 1 states that "Supplemental Inspection Numbers 57‑10‑09 and 57‑10‑13 of the Cessna 401/402 Supplemental Inspection Document (SID) inspect the auxiliary spar caps, but not the webs. Hence, this Airworthiness Directive applies even to SID‑compliant aircraft." That language identifies a point of potential overlap or confusion with the SID and clarifies that SID compliance does not discharge the AD because the AD inspects the spar web rather than the cap.

• FAA AD 2009‑04‑04 Amdt 39‑15810: Note 2 references that FAA AD. The text does not elaborate on the legal effect of this cross‑reference, but the inclusion indicates that the CASA AD is aligned with or mirrors an FAA directive addressing the same condition. The AD also allows compliance with "later FAA approved revision" of the referenced Service Bulletin, indicating deference to FAA approval for certain procedural updates.

What the AD does not state about interaction with other laws:

• The AD does not set out its relation to specific national aviation safety statutes, maintenance regulations, or certificate holder obligations beyond the AD text. It makes no express statement about superseding, supplementing, or being subordinate to other statutory provisions. The document’s structure , an AD issued by the regulator , implies it sits inside the aviation regulatory framework, but the AD itself does not restate or define that framework.

• The AD does not mention civil liabilities, insurance, or contractual obligations that might arise from carrying out or failing to carry out the mandated inspections and replacements. Those interactions will therefore need to be assessed against other applicable laws and contracts outside this document.

Consequences of the cross‑references:

• Reliance on a Service Bulletin and FAA approvals creates a technical dependency for compliance. If the Service Bulletin methodology changes under a later FAA‑approved revision, operators may adopt that revision as authorised by the AD text. Thus the AD’s practical requirements can evolve via FAA action without an immediate CASA reissue.

• The explicit distinction from the SID prevents operators from treating SID compliance as a substitute for the AD; it clarifies a gap in the existing inspection regime and mandates action to fill it.

• The cross‑reference to the FAA AD signals regulatory harmonisation: the CASA AD aligns with FAA actions taken for the same condition (as the text shows via Note 2). That may affect operators who operate internationally or who rely on FAA documentation for maintenance practices.

Overall, the AD interacts with the Service Bulletin (procedural delegation), the SID (non‑overlap and clarification), and an FAA AD (parallel action and approval pathway). The AD does not itself describe interactions with other statutory enforcement mechanisms or commercial obligations; those interactions fall to other legal texts outside this instrument.

The supplied text contains minimal explicit amendment history. What the document does contain relevant to amendment and revision:

• The AD authorises compliance using "Cessna Service Bulletin MEB08‑8 original issue, or later FAA approved revision." That language creates an amendment pathway for the technical inspection method: revisions to the Service Bulletin that receive FAA approval are explicitly allowed as compliant methods under the AD. The AD therefore anticipates procedural amendments through FAA‑approved Service Bulletin revisions.

• The AD references FAA AD 2009‑04‑04 Amdt 39‑15810 (Note 2). While the supplied text does not reproduce FAA AD 2009‑04‑04, the cross‑reference suggests the CASA AD is closely related to or derived from that FAA action. Any amendments to that FAA AD would likely be consequential to operators who follow FAA updates, and the AD’s allowance for later FAA‑approved Service Bulletin revisions creates an operational incentive to track FAA activity.

• Effective date and issuance: The AD is dated 23 February 2009 (signed by the CASA delegate) and "becomes effective on 2 March 2009." There is no subsequent amendment recorded in the supplied text.

• No explicit reissue, supersession, or revocation language is included in the text provided. The AD does not state that it amends any prior CASA instrument nor that it will be superseded by any future instrument.

• No provision is included for formal petitions to amend or to request an alternative method of compliance (AMOC). The AD instead permits adoption of "later FAA approved revision" of the Service Bulletin, but does not lay out a CASA process for AMOCs, exceptions, or extensions.

In short, within the supplied document there is no recorded amendment history beyond the single issuance and effective date. The only durable mechanism for modification indicated in the AD is the permission to use later FAA‑approved revisions of the referenced Service Bulletin. Any further amendments or reissues would be reflected in subsequent ADs or regulatory notices outside this text; none are included here.

The supplied AD contains no litigation history. It does not mention any court proceedings, appeals, regulatory reviews, or legal challenges, nor does it refer to prior litigation that gave rise to the AD. The Background section records operational reports ("The FAA received several reports of fatigue cracking on Models 402A and 402B aircraft") that motivated the AD but those are described as incident reports, not legal actions.

Because the document is an AD and not a judgment or statute with a litigation appendix, the absence of litigation history in the text is consistent with the instrument’s form. The AD does not record any disputes over its terms, any contested enforcement actions, or any legal interpretations. If litigation relating to this AD exists, it is not recorded in the provided text.

Practitioner implication from the provided content: there is no internal record of challenges or judicial interpretation to consult within this document. Any legal questions about enforceability of the AD, the scope of "before further flight" or related matters would need to be resolved by reference to the broader aviation regulatory framework, administrative law authorities or case law outside this document; the AD itself contains no litigation or appeal pathways.

The AD contains several features that may cause operational confusion or unanticipated obligations if read only cursorily. The following items are literal sourced "gotchas" to watch for:

• Applicability is by precise serial number ranges and includes an isolated serial number. The Applicability paragraph lists multiple models and serial numbers and, notably, includes "serial numbers 655 and 401‑0001 through 401‑0322" for Model 401. The isolated "655" inclusion is atypical and must be checked carefully; a mistaken exclusion or inclusion could lead to non‑compliance.

• SID compliance does not satisfy the AD. Note 1 explicitly says the SID supplemental inspections "inspect the auxiliary spar caps, but not the webs. Hence, this Airworthiness Directive applies even to SID‑compliant aircraft." Operators who assume SID completion discharges all spar inspection obligations will be wrong in relation to this AD.

• The inspection is required "in accordance with Cessna Service Bulletin MEB08‑8 original issue, or later FAA approved revision." The AD does not reproduce the Service Bulletin instructions. Practically, that means operators must obtain and consult MEB08‑8 (and track FAA‑approved revisions) to know exactly how to perform the inspection and measure cracks. Failure to follow the Service Bulletin's detailed procedure may create disputes over whether an inspection satisfied the AD.

• Tight initial inspection timing. The AD requires the initial inspection "within 10 hours time in service after 2 March 2009, unless already accomplished." For aircraft that were flying near the effective date, this provides a very short window to schedule inspections. Practitioners should note the combination of short initial window and the "before further flight after a hard landing" trigger.

• Event‑driven inspection after hard landing. The AD requires inspection "before further flight anytime the aircraft experiences a hard landing." The AD does not define "hard landing" in the text; operators will need to adopt an operational definition or follow the Service Bulletin's guidance to determine when that event‑driven inspection must occur. Absent a definition in the AD, this creates scope for disagreement about when the duty is triggered.

• Exact crack length threshold and measurement reproducibility. The AD sets a 0.5‑inch threshold for immediate replacement and a 0.50‑inch breakpoint for monitoring/replacement. Measurement of cracks to a 0.01‑inch tolerance can be subject to inspection technique variance. The AD requires visual inspection "in accordance with" the Service Bulletin; the Service Bulletin will determine the measurement technique. Operators must ensure measurement consistency and traceability to avoid disputes about whether a crack meets the replacement threshold.

• Repetitive inspection interval for sub‑threshold cracks is specified in hours time in service. The AD requires repetitive inspections "at intervals not to exceed 50 hours time in service." That creates a maintenance scheduling obligation tied to flight hours rather than calendar time, which may complicate scheduling for aircraft with irregular utilisation.

• Replacement deadline for sub‑threshold crack is a choice of 200 hours TIS or 12 months, "whichever occurs first." For low‑utilisation aircraft that fly few hours per year, the 12‑month calendar ceiling will be binding. For high‑utilisation aircraft, the 200‑hour TIS ceiling could be binding quickly. Operators must track both clocks.

• Reporting window confusion. The requirement to report detected cracks to Cessna is phrased as "report the results to the Cessna Aircraft Company at whichever of the following occurs later: Within 10 days after the inspection is accomplished; or, Within the next 10 days after 2 March 2009." The phrase "whichever occurs later" combined with the two alternatives creates a reporting deadline structure that is unusual and can be misread. Practically, for inspections after the effective date the trigger will usually be "within 10 days after the inspection." For inspections performed before the effective date, the second clause (within the next 10 days after 2 March 2009) may apply.

• No penalty language or AMOC process in the text. The AD prescribes actions but does not set out penalties for non‑compliance, nor does it include an alternative method of compliance (AMOC) procedure in this text. Operators seeking relief or alternative means of compliance will have to consult the broader regulator processes not contained in this AD.

• The AD applies even to SID‑compliant aircraft and references an FAA AD. Operators with cross‑jurisdictional fleets should note the AD’s linkage to FAA approval pathways and to FAA AD 2009‑04‑04. Coordination and conformity of maintenance records across jurisdictions may be necessary.

These points are derived directly from the AD wording and the notes. Each creates an implementation or interpretation risk that maintenance managers should address explicitly when planning compliance.

The AD prescribes a short, specific compliance sequence. Follow these steps, reading the AD text and the referenced Service Bulletin carefully:

1. Determine applicability.

   • Check the aircraft model and exact serial number against the Applicability list. The AD enumerates Model 401, 401A, 401B, 402, 402A and 402B with defined ranges and isolated serial numbers; ensure the aircraft’s serial number is within those ranges before proceeding.

2. Obtain the procedural guidance.

   • Acquire Cessna Service Bulletin MEB08‑8 original issue, and identify any later FAA‑approved revisions. The AD requires inspection "in accordance with Cessna Service Bulletin MEB08‑8 original issue, or later FAA approved revision." Use the detail in that Service Bulletin as the authorised inspection technique and measurement procedure.

3. Schedule the initial inspection.

   • If not already inspected, perform the initial visual inspection "within 10 hours time in service after 2 March 2009." For any aircraft experiencing a hard landing, inspect "before further flight" after that event. Log the inspection time and method in maintenance records consistent with the Service Bulletin.

4. Conduct the visual inspection.

   • Inspect the auxiliary wing spar near the main landing gear trunnion for cracks, paying particular attention to the spar web area (Note 1 clarifies SID inspections cover caps but not webs). Use the Service Bulletin’s specified inspection points, access methods and measurement approach.

5. Take actions based on measured crack length.

   • If any crack measured is 0.5‑inch or more, replace the cracked part(s) "before further flight." Do not return the aircraft to service until replacement is completed.
   • If detected cracks are less than 0.5‑inch, implement the repetitive inspection schedule: inspect the crack length at intervals not to exceed 50 hours time in service. Replace the part "before further flight" if the crack grows to 0.50‑inch or more.
   • In all cases where a crack <0.5‑inch was initially found, replace the cracked part within 200 hours time in service after the original detection or within 12 months after the original detection, whichever occurs first. Track both the time‑in‑service usage and calendar days to ensure replacement occurs within the shorter applicable limit.

6. Report detected cracks to Cessna.

   • If cracks are detected during any inspection, report the results to the Cessna Aircraft Company "at whichever of the following occurs later: Within 10 days after the inspection is accomplished; or, Within the next 10 days after 2 March 2009." In practice, for inspections after the effective date this will be within 10 days after the inspection; for inspections before 2 March 2009 treat the second clause as potentially applicable. Retain copies of the report and any confirmation from Cessna.

7. Maintain records.

   • While the AD text does not specify record retention periods, good practice for compliance is to keep inspection records, measurement results, replacement invoices, and the Cessna report(s) in the aircraft maintenance record for audit or regulatory review. Record the exact measurement methodology used consistent with MEB08‑8 and the identity of the person or organisation performing the inspection and replacement.

8. Apply the "before further flight" constraint.

   • Where the AD requires replacement "before further flight" (for cracks ≥0.5‑inch, and for replacement when a monitored crack reaches 0.50‑inch), do not return the aircraft to service until the replacement is completed and the maintenance release issued by the authorised certifying engineer under applicable maintenance standards. Determine the local maintenance release process required for such grounding actions.

9. Plan for parts and labour.

   • Anticipate that immediate replacement or replacement within the 200‑hour/12‑month window will create demand for replacement parts and shop time. Arrange parts procurement and labour scheduling accordingly. The AD does not allocate cost but the obligation to replace is mandatory where thresholds are met.

10. Monitor for Service Bulletin and FAA updates.

• The AD allows compliance with "later FAA approved revision" of MEB08‑8. Monitor FAA and Cessna communications for revisions to the Service Bulletin that receive FAA approval, and adopt those updated procedures as a compliant inspection method consistent with the AD.

11. Treat SID compliance as insufficient.

• Do not assume compliance with Cessna 401/402 SID supplemental inspections 57‑10‑09 and 57‑10‑13 discharges this AD. The SID inspects spar caps but not spar webs; this AD targets the spar web and therefore applies even where SID inspections have been performed.

12. Coordinate with regulatory authority where uncertainty exists.

• If an operator seeks an alternative method of compliance or faces exceptional circumstances, consult the regulator or follow the regulator’s established AMOC process (note the AD text does not lay out such a process). Any alternative method should be documented, authorised by the regulator, and consistent with ensuring the unsafe condition is addressed.

Adhering to these steps will implement the AD’s prescriptive obligations as stated in the provided text. Keep all records contemporaneous and ensure that measurement techniques follow the Service Bulletin to create traceable and auditable compliance evidence.