AD/B737/152 Amdt 1 - Centre Fuel Tank - Limitations

Centre fuel tank dry pump operation. The centre fuel tank on Boeing 737 series aeroplanes is located in the wing centre section and provides additional fuel capacity. The fuel pumps within that tank rely on fuel for cooling and lubrication. If the pumps are operated when the tank is empty or nearly empty, they run dry. Extended dry operation causes overheating of the pump bearings and potential contact between rotating and non-rotating parts, generating hot surfaces, sparks, or a flame front capable of igniting fuel vapour. The manufacturer’s procedures had already prohibited extended dry operation; the AD elevates this prohibition to a mandatory AFM limitation.

Aircraft Flight Manual (AFM). The AFM is the legally binding document that defines the operating limits, procedures, and performance data for a specific aircraft type. The Limitations Section contains conditions that must be observed during all flight operations; any deviation requires specific approval or is a regulatory breach. By placing the dry pump prohibition in the Limitations Section, the AD makes it a primary operational constraint.

Airworthiness Directive. Under CASR Part 39, an AD is a legally enforceable notice issued when an unsafe condition exists in a product and is likely to exist in other products of the same type. Compliance is mandatory for the aircraft to remain airworthy. ADs may require inspection, modification, or amendment of the AFM. This AD falls into the last category: it adds an operational limitation rather than a physical alteration.

Incorporation by reference. The original AD/B737/152 set out the AFM revision text directly. Amdt 1 deletes that text and instead states that the requirement is to incorporate FAA AD 2001-08-24. This means the operator must obtain the FAA document to know the precise wording of the limitation. This approach reduces duplication but places an information-gathering burden on operators. The amendment also notes that FAA AD 2011-18-03 represents a terminating action , once that FAA directive is complied with (likely involving a design change to the fuel pump system or a permanent operational solution), the original limitation may be removed or superseded.

Alternate Methods of Compliance (AMOC). An AMOC allows an operator to use a different means of achieving the same level of safety as the directive’s requirement. The directive explicitly accepts AMOCs approved by the FAA for FAA AD 2001-08-24 as valid for this AD. It also preserves any AMOCs that were in force before Amdt 1. This provides operational flexibility but requires careful tracking of approvals across two regulators.

Terminating action. FAA AD 2011-18-03, issued on 18 August 2011, is described as the terminating action. That AD likely mandates a modification or replacement of the centre fuel tank pump system or a permanent operational change that eliminates the risk of dry operation. Until that terminating action is accomplished, the AFM limitation remains in force.

Background accidents. The 2001 Bangkok incident involved a 737-400 that caught fire and burned after refueling while the centre tank pumps were operating dry. The 1990 accident on a 737-300 had similar circumstances. In neither case was the exact ignition source identified, but the common factor was dry pump operation. The AD thus adopts a precautionary approach: prohibit the condition that correlates with the accidents, even absent a confirmed causal link.

The directive applies to every operator of any Boeing 737 series aeroplane on the Australian civil aircraft register. This includes: major airlines operating 737NG and 737 MAX variants; charter and regional operators; freight carriers; corporate flight departments; and any other entity that owns, leases, or operates a 737 within Australia. Because the applicability covers all Model 737 series aeroplanes, no variant is excluded , older 737-200/300/400/500 models and newer 737-600/700/800/900/MAX variants all fall within scope. The directive also affects maintenance organisations, as they may be responsible for incorporating the AFM revision and for verifying that any AMOCs are correctly applied. Flight crew members must be trained on the new limitation and must operate the aircraft accordingly. Engineering departments, if the operator is large enough, must manage the compliance documentation and liaise with CASA or the FAA for any alternative approvals. Insurance underwriters and lessors also have an interest, because an aircraft that is not compliant with an AD may have reduced insurability or residual value. The regulator CASA is affected in its role of surveillance and enforcement. The FAA is indirectly relevant because its ADs are incorporated by reference, and its AMOC approvals are automatically accepted. Boeing, as the type certificate holder, may receive feedback on the effectiveness of the limitation and may develop the terminating action. The directive does not directly affect passengers, product suppliers, or manufacturers of aftermarket parts, unless they provided AMOC approval. The compliance burden falls entirely on operators: they must obtain the FAA documents, revise the AFM (which may require reissue or temporary revision), distribute the revision to flight crews, and ensure that daily operations respect the limitation. For operators with large mixed fleets, the task is straightforward but still requires administrative effort. For very small operators, the cost of obtaining and interpreting FAA ADs and updating the AFM may be nontrivial relative to their revenue. However, given that the original AD has been in force since 2001, most operators should already have the limitation in place; Amdt 1 is primarily a cross-referencing clean-up rather than a substantive new burden.

Duty to revise the AFM. The primary duty under the directive is to amend the Limitations Section of the AFM to include the prohibition on extended dry operation of centre fuel tank pumps, as specified in FAA AD 2001-08-24. The directive states that the AFM revision must be accomplished in accordance with the FAA AD. The operator must ensure that the current version of the AFM, or the temporary revision, contains the mandatory language. This duty applies to the registered operator, who is legally responsible for continued airworthiness.

Duty to operate within the limitation. Once the AFM is revised, flight crews must not operate the centre tank fuel pumps when no fuel is present. This is an operational limitation that overrides any customary practice or convenience. Pilots must adjust fuel management procedures to avoid dry running, even if that increases flight planning complexity or reduces flexibility.

Right to use prior AMOCs. The directive expressly states that any exclusion or alternate method of compliance that was in force before the coming into effect of Amdt 1 continues to be in force. This preserves rights that operators may have negotiated under the original AD. However, those pre-existing AMOCs must still be valid for the substantive requirement (FAA AD 2001-08-24) and have not expired. Operators should review their AMOC records.

Right to apply for new AMOCs. An operator may seek CASA approval of an alternate method of compliance. Additionally, the directive accepts FAA-approved AMOCs for FAA AD 2001-08-24 as equivalent. This means an operator can apply to the FAA for an AMOC and, if granted, it will be automatically valid under this AD. This is a significant right because it gives access to a broader pool of technical expertise and approval pathways. However, obtaining an AMOC from two regulators may create confusion over which approval takes precedence; in practice, CASA would likely accept the FAA approval without separate evaluation.

Right to rely on terminating action. Once the terminating action in FAA AD 2011-18-03 is accomplished, the requirement to include the limitation in the AFM may be ended. The directive provides a clear pathway to exit the limitation. Operators have a right to adopt the terminating action when it becomes available, and they may choose to do so early or wait until the compliance date set by FAA AD 2011-18-03.

Duty to maintain records. Operators must keep records of compliance with the AD, including: a copy of the revised AFM or temporary revision; evidence of when the revision was inserted; records of crew training on the new limitation; and any correspondence regarding AMOCs. These records are subject to CASA inspection. Failure to maintain records could itself be a breach.

The directive does not itself list penalties; they are found in the enabling legislation. Under section 23 of the Civil Aviation Act 1988, and regulations made under it , particularly CASR 11.055 and Part 39 , failure to comply with an airworthiness directive is an offence. The maximum penalty for an individual can be up to $13,750 for a strict liability offence, and higher for fault-based offences. For a body corporate, penalties can be multiplied by five (under the Crimes Act 1914, section 4B). More significantly, CASA can suspend or cancel the airworthiness certificate of any aircraft found to be non-compliant. Since an airworthiness certificate is a precondition for legal flight, grounding can impose massive economic costs on operators, far exceeding any fine. CASA may issue a direction under CASR 11.055 requiring immediate compliance. Criminal prosecution is theoretically possible if non-compliance contributed to an accident, but rare in practice. Enforcement is typically done through surveillance: during annual airworthiness reviews, spot inspections, or investigations following an incident, CASA will verify that all applicable ADs are complied with. If a breach is discovered, CASA may issue a warning letter, impose a civil penalty, or prosecute depending on severity and history. The directive’s incorporation by reference to the FAA AD means that operators must also ensure they comply with any later revisions of FAA AD 2001-08-24, as CASA’s directive refers to that FAA AD as the source requirement. However, the directive only requires revision of the AFM; it does not mandate the terminating action until a separate directive is issued. Therefore, non-compliance could arise either from failing to insert the AFM limitation or from failing to update to a newer FAA AD version if CASA later amends this directive. The fact that the compliance date remains unchanged from 2001 is important: an operator that only recently acquired a 737 might mistakenly believe the AD is new and that they have a grace period. They do not. The original AD became effective 10 May 2001, so any aircraft operating in Australia since then should already have the limitation. Amdt 1 does not reset the compliance clock.

The directive is issued under CASR Part 39, which itself derives from the Civil Aviation Act 1988. CASR Part 39 establishes the regime for airworthiness directives, including the power to issue, amend, and revoke ADs; the requirements for public consultation (if any); and the obligations on operators to comply. The directive also interacts with the Airworthiness Management Framework under CASR Part 42 for aeroplanes above a certain size, which requires operators to maintain a continuing airworthiness management organisation (CAMO) that tracks AD compliance. For smaller operators not subject to Part 42, compliance is still required but the administrative structure is less formal. The directive incorporates by reference FAA AD 2001-08-24 and recognises FAA AD 2011-18-03 as terminating action. This creates a direct interaction with US federal regulations: while the FAA ADs are not Australian law per se, they become mandatory in Australia through the directive’s reference. Therefore, if the FAA later amends or supersedes AD 2001-08-24, that change does not automatically flow into Australian law unless CASA amends AD/B737/152. However, the directive does accept FAA-approved AMOCs, so operators can use FAA approvals without separate CASA action. The directive does not interact with state workplace health and safety laws directly, but an operator’s general duty of care under state OHS legislation could also require adherence to known safety standards, which would likely reinforce the AD. The directive may also be relevant in private law: an operator that fails to comply could face civil liability for negligence if an accident occurs, and non-compliance could be strong evidence of breach of duty. Insurance policies for aircraft typically require compliance with all applicable ADs; failure could void coverage. The directive does not interact with the Competition and Consumer Act 2010, except perhaps if an operator misrepresents compliance status when selling or leasing the aircraft. Internationally, the directive gives effect to Australia’s obligations under the Chicago Convention (ICAO Annex 8), which requires states to maintain continuing airworthiness of aircraft on their register. Finally, the directive may be read alongside other CASA ADs for the 737 fleet, such as those relating to the fuel system, wiring, or structural inspections. Operators must ensure that all ADs are complied with cumulatively.

AD/B737/152 was originally issued in 2001 with an effective date of 10 May 2001. That original directive required revision of the AFM Limitations Section to prohibit extended dry operation of centre fuel tank pumps. The text of the requirement was set out in full in the directive. Amdt 1, signed by Mike Higgins as Delegate of CASA on 5 September 2011 with an effective date of 30 September 2011, deletes the original text and instead requires incorporation of FAA AD 2001-08-24 Amdt 39-12201. The Background explains that this change was made to facilitate easier cross-referencing to FAA AD 2011-18-03 Amdt 39-16785, which details the terminating action. The amendment also states that any exclusion or AMOC in force before Amdt 1 continues in force. The original compliance date remains unchanged. The amendment thus serves two purposes: administrative streamlining and alignment with the FAA’s terminating action. No further amendments are referenced. The directive as amended is the current version. Because the directive incorporates the FAA AD by reference, any future changes to that FAA AD would not automatically amend the Australian directive; CASA would need to issue a further amendment. Operators should monitor future CASA ADs that might adopt the terminating action as a separate requirement. The amendment history is short, reflecting the directive’s narrow scope.

No litigation is referenced in the directive itself. Airworthiness directives are rarely challenged directly, because they are technical safety determinations with a high degree of deference to the regulator. If an operator wished to challenge AD/B737/152 Amdt 1, they would have two possible avenues. First, a judicial review application under the Administrative Decisions (Judicial Review) Act 1977 in the Federal Court, arguing that the decision to issue the directive was ultra vires, procedurally flawed, or considered irrelevant matters. Grounds might include: the directive incorporates by reference a document that is not publicly available, potentially breaching procedural fairness; or the connection between dry pump operation and the accidents is inferential rather than proven. However, the courts give CASA wide discretion on safety matters. Second, an appeal to the Administrative Appeals Tribunal for merits review of a specific decision, such as a denial of an AMOC. The directive itself is a legislative instrument rather than a reviewable decision, so a challenge would likely target enforcement action or an AMOC refusal. As of the date of the directive, no known court cases involve AD/B737/152. The underlying FAA ADs may have been subject to US litigation, but that is outside Australian jurisprudence. The absence of litigation suggests that the directive has been implemented without legal controversy, likely because the limitation is consistent with manufacturer procedures and does not impose extreme economic hardship. However, if a later terminating action (FAA AD 2011-18-03) imposes a costly modification, litigation might arise. The issuing of Amdt 1 to incorporate the FAA AD by reference may have been intended to avoid future disputes over wording interpretation by simply pointing to the FAA standard.

Compliance date unchanged. The directive states that the compliance date remains unchanged from that detailed in the original issue. An operator acquiring a 737 after 2001 might assume the directive is new and that a grace period applies. This is incorrect. The requirement to have the AFM limitation has been in effect since 10 May 2001. Amdt 1 only changes the form of the requirement; it does not reset the clock. Any aircraft operated without the limitation since 2001 has been non-compliant, though enforcement may be unlikely if the operator can show they have recently become aware. But the legal obligation is retrospective.

Incorporation by reference creates an information burden. The original AD set out the required AFM language in full. Amdt 1 simply says to revise the AFM "to include the information detailed in FAA AD 2001-08-24 Amdt 39-12201." Operators must now obtain a copy of that FAA AD to know precisely what text to insert. The FAA AD is publicly available but may require locating it on the FAA’s website, and it may reference further documents. An operator that does not obtain the FAA AD will not know the exact wording. For an operator that already complied with the original AD, the change is likely harmless, but if the FAA AD language differs from the original CASA text, there could be a discrepancy. The directive does not state that the original CASA text remains acceptable.

AMOC continuity trap. The directive says that AMOCs in force before Amdt 1 continue. However, if an operator had an AMOC approved only by CASA under the original AD, that AMOC may still be valid. But if the AMOC was specific to the original text and not to the FAA AD, it might not align with the new reference. The operator should verify that the pre-existing AMOC explicitly addresses the requirement as now defined by FAA AD 2001-08-24, or seek a new AMOC.

Terminating action not mandatory yet. The directive mentions FAA AD 2011-18-03 as the terminating action, but the directive does not require operators to comply with that FAA AD. The terminating action will likely become mandatory through a future CASA AD or when the FAA AD’s own compliance date passes and the operator chooses to adopt it. An operator might mistakenly believe that because the terminating action exists, the AFM limitation no longer applies. That is false. The AFM limitation remains in force until the terminating action is actually accomplished.

Dry operation definition vagueness. The directive prohibits "extended dry operation". The FAA AD may define "extended" precisely (e.g., more than 30 seconds). If the precise definition is not provided in the AFM, crews might inadvertently violate the limitation. The operator must ensure the AFM revision includes a clear operational definition.

All model series applicability. The directive applies to all Model 737 series aeroplanes. An operator with a 737-200, which may have different fuel pump configurations, is still bound. Older aircraft may have different pump designs that are more or less susceptible to dry operation hazards. The directive does not differentiate.

1. Obtain the referenced FAA documents. Download FAA AD 2001-08-24 Amdt 39-12201 (found in the U.S. Federal Register or FAA website). Also obtain FAA AD 2011-18-03 Amdt 39-16785 for awareness of the terminating action. If you cannot access these, contact CASA or the FAA for copies. Keep them in the fleet technical records.

2. Review any existing AMOCs. Check your records for any exclusions or alternate methods of compliance granted under the original AD/B737/152. Confirm that they remain valid and apply to the requirement as now defined by FAA AD 2001-08-24. If an AMOC references the original CASA text, consider reapplication.

3. Revise the Aircraft Flight Manual. Amend the Limitations Section to include the prohibition on extended dry centre tank fuel pump operation, using the exact language from FAA AD 2001-08-24. If your AFM is electronic or has a temporary revision system, issue a revision or temporary change. Ensure the revision is recorded in the FAA Approved AFM (or CASA equivalent). For Australian registered aircraft, the AFM must be approved; a temporary revision issued by the operator may need to be logged.

4. Distribute and train. Provide the revised AFM or a summary to all flight crew. Conduct briefing or training to ensure pilots understand the limitation: when the centre tank pumps may not be operated, how to recognise dry operation, and the consequences of non-compliance. Document the training.

5. Update operational procedures. Review fuel management checklists and standard operating procedures to include steps that prevent dry operation. For example, ensure that centre tank pumps are turned off when the tank is empty, or that the fuel system configuration avoids running the pumps dry during transfers. Consider if any automation (e.g., fuel panel logic) needs manual override.

6. Implement AMOC if desired. If your operation requires a different means of compliance (e.g., due to unique operational needs), apply to CASA or the FAA for an AMOC. For FAA AMOCs, they are automatically accepted under this directive. Include justification showing equivalence. If applying to CASA, reference the directive and the FAA AMOC option.

7. Monitor for terminating action. Track compliance with FAA AD 2011-18-03. If it requires a modification, plan and implement it. Once accomplished, the AFM limitation may be removed per the FAA AD instructions. Keep evidence that the terminating action is complete.

8. Maintain records. Create a compliance file containing: a copy of this directive (AD/B737/152 Amdt 1), the FAA ADs, the revised AFM pages or temporary revision, any AMOC approvals, crew training records, and a log of compliance dates. Keep these for the life of the aircraft. CASA may request them during audits or airworthiness reviews.

9. Verify for incoming aircraft. If you acquire a 737 from another operator, confirm that the AFM already includes the limitation and that any prior AMOCs transfer. If not, complete compliance before operation.

10. Seek professional advice if uncertain. Given the technical nature and the incorporation by reference, consult with a CAMO, a CASA delegate, or a legal specialist in aviation regulation to ensure no hidden obligations are missed.