AD/CF6/57 Amdt 1 - HPT S2 NGV Distress

Airworthiness Directive (AD). An AD is a legally enforceable notice issued by a national aviation regulator, in this case CASA under the Civil Aviation Act 1988 and the Civil Aviation Regulations 1988. It requires operators to inspect, modify, or replace components within a specified timeframe. Non‑compliance renders the aircraft unairworthy, exposes the operator to enforcement action, and may void insurance coverage. AD/CF6/57 Amdt 1 is an amendment to the original AD/CF6/57, which first became effective on 20 January 2005. The amendment corrects a drafting error in paragraph 2(a)(i) of the compliance section: it substitutes “5.0 or more hours per flight leg” for the erroneous “5.0 or more cycles per flight leg.” This change affects only the CF6-80C2D1F engine, and it alters the interval for the “next regular S2 Blade inspection” from a cycles‑based metric to a hours‑per‑flight‑leg metric, which is more appropriate for a long‑haul engine often flown on multiple sectors per day.

HPT S2 NGV distress. The term “distress” covers cracking, deformation, or other damage to the HPT stage 2 nozzle guide vanes. These vanes direct hot combustion gases onto the stage 2 turbine blades. If a vane separates, it can enter the turbine rotor and cause an uncontained failure: fragments may penetrate the engine casing, potentially damaging the airframe or causing a fire. The AD identifies the specific failure mechanism as “HPT S2 NGV distress” but does not define the types of distress. Instead, it relies on the GE Service Bulletin’s inspection criteria, which use a visual classification system (e.g., crack length and location). Operators must obtain Revision 6 of that service bulletin and follow the inspection and disposition instructions to the letter.

Flex-boroscope inspection. This is a non‑destructive inspection technique in which a flexible borescope (a fibre‑optic or video probe) is inserted through the engine’s borescope ports to examine the NGVs in situ. The AD requires the inspection to be performed in accordance with paragraphs 3.B.(3) through 3.B.(5) of the GE Service Bulletin. These paragraphs detail the probe insertion points, the viewing angles, and the acceptance criteria. Flex‑boroscopy is less invasive than a full engine strip, but it still requires engine downtime, specialised equipment, and a certified technician. The cost per inspection can be significant, especially if the engine must be removed from the aircraft or if the inspection reveals conditions requiring removal.

Cycles-since-overhaul (CSO) and cycles-since-last-inspection (CSLI). These are the primary compliance metrics. A “cycle” for a turbine engine is typically one start, take‑off, and landing. CSO counts cycles from the last time the module was overhauled. CSLI counts cycles from the last inspection of the specific part. The AD uses CSO for the initial inspection thresholds and CSLI for the reinspection intervals. For engines operated in multiple thrust‑level configurations (e.g., different derates), the AD requires operators to use the “lowest applicable initial inspection threshold” for initial inspection and the reinspection intervals associated with the “current engine model.” This rule prevents operators from circumventing a lower threshold by switching configurations.

Affected part numbers and conditions. The AD contains a table that lists NGV part numbers and a “Provided that” column that specifies repair or modification history. For example, P/N 1347M66G03 and 1347M66G04 are affected only if insert P/N 1957M40G01 or 1957M40G02 was installed during repair. P/Ns 9373M80G07 through 9373M80G22 and 9373M80G25 through 9373M80G32 are affected if that same insert was installed or if the NGV was repaired by GE between 1 April 1998 and 30 September 1999. P/Ns 9373M80G33 through 9373M80G36 are affected simply if the part was repaired. This conditional applicability imposes a heavy record‑keeping burden: operators must trace the repair and modification history of each NGV to determine whether it falls within the AD’s scope.

The primary class affected is operators of aircraft powered by any of the 17 listed CF6-80C2 engine models: -80C2A1, -80C2A2, -80C2A3, -80C2A5, -80C2A5F, -80C2A8, -80C2B1, -80C2B1F, -80C2B2, -80C2B2F, -80C2B4, -80C2B4F, -80C2B5F, -80C2B6, -80C2B6F, -80C2B6FA, -80C2B7F, -80C2B8F, and -80C2D1F. These engines are installed on Airbus A300, Airbus A310, Boeing 747, Boeing 767, and McDonnell Douglas MD-11 aeroplanes, though the AD notes that installation is not limited to those types. Any airline, cargo carrier, or leasing company that operates any of these engine‑airframe combinations must ensure compliance.

Within an operator’s organisation, the duty falls on the continuing airworthiness management organisation (CAMO) or equivalent maintenance control department. They must identify which engines in the fleet carry NGV part numbers listed in Table 1, trace the repair history of each NGV, schedule the initial flex‑boroscope inspection at or before the applicable CSO threshold, and then manage the reinspection or removal intervals. The AD does not exempt operators with fewer than a certain number of engines; it applies equally to a single‑engine owner and to a large fleet.

Maintenance, repair, and overhaul (MRO) organisations are indirectly affected. The AD prescribes that the inspection must be performed in accordance with the GE Service Bulletin. MROs that perform the flex‑boroscopy must have the bulletin, the correct borescope equipment, and appropriately trained technician: typically a certified aircraft maintenance engineer (AME) with engine‑type rating. If the inspection reveals cracks that require removal, the MRO must also be able to replace the NGV and, if the replacement part is a new or different P/N, must ensure that the new part does not bring a new AD condition with it.

Part manufacturers and repair stations are also affected. The AD specifically references NGVs repaired by GE between 1 April 1998 and 30 September 1999. This means that any operator who sent an NGV to GE for repair during that period must now consider that part to be affected. This retroactive effect catches parts that were previously considered airworthy under the original design approval. It also imposes a tracing burden: the operator may need to consult GE’s records if its own records are incomplete.

Finally, lessors and financiers have an economic interest. If an operator fails to comply, the aircraft may be grounded, which reduces the lessor’s rental income and may trigger defaults under the lease. The AD creates an additional due‑diligence item: before acquiring an aircraft or engine, a prospective owner should verify that the NGVs are not affected or that any required inspections have been completed and recorded.

Duty to inspect. The operator must flex‑boroscope each affected NGV at or before the applicable initial inspection threshold. For most models the threshold is 800 CSO; for the A2, B2 and B2F models it is 1,600 CSO; for engines already past those thresholds as of 20 January 2005, the operator must inspect within 200 additional CSO after that date. The inspection must follow paragraphs 3.B.(3) through (5) of GE Service Bulletin CF6-80C2 S/B 72-0952 Revision 6.

Duty to reinspect or remove. Based on the findings of the initial inspection, the operator must follow the “Inspection Table for Cracking in the Airfoil Outer Fillet”, Figure 5 Sheets 1 and 2, of the same GE Service Bulletin. The AD does not set its own crack‑length thresholds; it incorporates the manufacturer’s criteria by reference. The AD adds one important clarification: if the bulletin says “reinspect at next regular S2 Blade inspection,” then for the affected engines the “next regular S2 Blade inspection” is defined as 250 CSLI (for CF6-80C2D1F with 5.0 or more hours per flight leg) or 400 CSLI (for all other engines). The operator must therefore not rely solely on the bulletin’s generic language; it must apply the AD‑specific intervals.

Duty to use lowest applicable threshold for multi‑configuration engines. If an engine is operated in more than one thrust‑level configuration over its life, the operator must use the lowest initial inspection threshold among those configurations. For reinspection, the operator must use the intervals associated with the current engine model. This prevents an operator from switching to a less restrictive model after a high‑stress operation to reset the inspection clock.

Right to record compliance. The AD does not explicitly grant a right to alternative means of compliance, but under standard CASA practice an operator may apply for an alternative means of compliance (AMOC) if it can demonstrate an equivalent level of safety. The AD does not mention AMOCs, so an operator would need to petition CASA under regulation 39(5) or equivalent. The directive itself is prescriptive: it requires the specific bulletin and the specific intervals. Any deviation requires approval.

Right to remove the part. If the operator does not want to inspect or if the inspection reveals distress beyond allowable limits, the operator may remove the NGV from service. Removal ends the obligation under this AD for that part, but the replacement part must be either a new part that is not affected or an affected part that has been inspected and found acceptable.

Right to rely on authorised repair station. The AD does not require the operator to perform the inspection itself. It may contract an appropriately rated MRO to perform the flex‑boroscopy. The operator remains responsible for ensuring compliance, but it can delegate the technical work to a certified maintenance provider.

Non‑compliance with AD/CF6/57 Amdt 1 is a breach of the Civil Aviation Act 1988 and the Civil Aviation Regulations 1988. The specific provision is likely regulation 39, which makes it an offence to operate an aircraft that does not comply with an applicable AD. The maximum penalty for an individual is typically 50 penalty units (currently AUD $11,000 per unit, so AUD $550,000) or imprisonment, and for a body corporate the penalty can be five times that amount. CASA can also suspend or cancel the aircraft’s certificate of airworthiness, which grounds the aircraft until compliance is achieved.

Enforcement is risk‑based. CASA conducts surveillance through its regional offices, audits of continuing airworthiness records, and ramp inspections. If a CASA inspector discovers that an engine has exceeded its inspection threshold without the inspection being performed, the inspector may issue a direction to ground the aircraft, a show‑cause notice, or a remedial order. In serious cases CASA can refer the matter to the Director of Public Prosecutions.

The AD itself does not specify a penalty; it is a technical document that assumes compliance is mandatory. However, the background note warns that the original AD resulted from an uncontained engine failure. That language is a clear signal that the regulator treats this as a high‑risk condition. An operator that chooses to defer the inspection for commercial reasons - for example, to avoid grounding an aircraft during a peak flying season - exposes itself to both regulatory action and potential civil liability if a failure occurs.

Civil liability may also arise if non‑compliance contributes to an accident. In Australia, the Civil Aviation Act provides a statutory cause of action for breach of a duty of care, and compliance with an AD is strong evidence of exercising reasonable care. Conversely, failure to comply would be persuasive evidence of negligence in a tort claim by passengers, cargo owners, or third parties.

There is no private right of action under the AD itself, but the AD’s mandatory language creates a duty that can be used in a negligence claim. An airline that knowingly operated an engine beyond the inspection threshold would find it very difficult to defend itself against an allegation of breach of duty.

FAA AD 2004-22-07 (Amdt 39-13835). Note 2 of the AD states: “FAA AD 2004-22-07 Amdt 39-13835 refers.” This means the CASA AD is substantively identical to, or derived from, a US Federal Aviation Administration airworthiness directive. Operators that hold US‑registered aircraft (e.g., under a US‑based leasing company) must also comply with the FAA AD. The CASA AD may be approved as an alternative means of compliance for the FAA AD, and vice versa, but the operator should confirm with CASA and FAA. In practice, the GE Service Bulletin is the same for both authorities, and the inspection intervals are identical, so an operator that complies with one normally complies with the other. However, the effective dates and the amendment history may differ: the CASA original issue became effective on 20 January 2005; Amendment 1 becomes effective 7 July 2005. The FAA AD may have a different timeline.

Civil Aviation Regulations 1988 (CAR) and Civil Aviation Safety Regulations 1998 (CASR). This AD operates within the broader regulatory framework for continuing airworthiness. CAR 39 requires that no person operate an aircraft to which an AD applies unless the requirements of the AD have been complied with. The AD’s inclusion by reference of the GE Service Bulletin means that maintaining the current revision of that bulletin becomes a regulatory requirement. Operators that use older revisions of the bulletin, or that use a different GE advisory document, may be non‑compliant.

Maintenance control manual and continuing airworthiness management. The operator’s approved maintenance program must incorporate the AD’s inspection tasks. The AD becomes part of the operator’s schedule of required inspections and overrides any less stringent intervals in the manufacturer’s recommended maintenance plan. The operator must also ensure that the engine logs reflect the CSO and CSLI counts accurately, because compliance is measured in cycles, not calendar time.

International obligations. Australia is a signatory to the Convention on International Civil Aviation (Chicago Convention). CASA is required to notify the International Civil Aviation Organization (ICAO) of differences from international standards when issuing ADs that are more or less restrictive than the ICAO standard. Operators that fly internationally must ensure that their compliance records are recognised by other civil aviation authorities, particularly when entering airspace of states that adopt FAA or EASA ADs by reference.

Contractual obligations. Leases and aircraft mortgage agreements often require the lessee to comply with all ADs. Non‑compliance with an AD can be an event of default under an aircraft lease, giving the lessor the right to repossess the aircraft. Similarly, insurance policies may exclude cover for loss caused by operation of an aircraft that is not in an airworthy condition, including failure to comply with an AD. Operators should confirm that their maintenance reserve structures adequately fund the inspection cost and any NGV replacement.

The original AD/CF6/57 became effective on 20 January 2005. That original directive required the same initial inspection thresholds, the same reference to GE Service Bulletin Revision 6, and the same reinspection intervals. The one substantive difference was in paragraph 2(a)(i) of the compliance section, which originally read: “For CF6-80C2D1F engines with 5.0 or more cycles per flight leg, the next regular S2 Blade inspection means within 250 cycles‑since‑last‑inspection (CSLI).” Amendment 1, signed on 19 May 2005 and effective 7 July 2005, corrects that phrase to “5.0 or more hours per flight leg.” The change reflects a better understanding of the duty cycle of the D1F engine, which is a long‑haul variant that often flies sectors of 5 hours or more. Using cycles as a metric would have produced an unreasonably short inspection interval for operators that fly very few cycles per flight hour.

No other changes were made. The background to Amendment 1 specifically states: “This amendment makes correction to paragraph 2(a)(i) of the compliance section … There are no other changes to the Directive.” This means the applicability table, the initial inspection thresholds, the reference to GE SB revision, and the reinspection intervals for all other engine models remain exactly as in the original directive.

The amendment is the only revision to this AD. There is no subsequent amendment noted in the source. Operators must ensure they have the amendment 1 version, not the original, because the original contained an error that could lead to excessively frequent inspections or, conversely, to a mistaken belief that the D1F engine is subject to a cycles‑based interval. The effective date of the amendment (7 July 2005) is the date from which the corrected interval applies. Inspections performed between 20 January 2005 and 6 July 2005 should have been done under the original wording, but the error could have caused confusion.

The source document does not cite any litigation related to this AD. There is no record in the text of any legal challenge to the AD’s validity, any appeal by an operator against the inspection requirements, or any compensation claim arising from the uncontained engine failure that prompted the original AD. The background states that the AD “results from an uncontained engine failure due to HPT S2 NGV distress,” but it does not name the aircraft operator, the date, or the outcome of any civil action. It is highly likely that the failure led to litigation between the operator, GE, and possibly the NGV repairer, but those proceedings are not mentioned in the AD and cannot be inferred.

Under Australian administrative law, an AD is a legislative instrument made by a CASA delegate under the Civil Aviation Act. It would be subject to judicial review if an operator could show that the AD was made without authority, was procedurally unfair, or was disproportionate to the risk. No such challenge is reported in this case. The high level of deference typically accorded to aviation safety regulators in safety‑critical areas means that a judicial review application would face a very high threshold.

The absence of litigation history is itself notable. It suggests that the industry accepted the AD as necessary and that the compliance burden, while real, was not seen as so unreasonable as to warrant a challenge. The amendment correcting the D1F interval indicates that the regulator was willing to adjust after further analysis, which may have preempted any operator complaint.

In future, an operator that suffers economic loss because it was forced to ground an engine for inspection and found no distress might consider applying for an AMOC or seeking compensation from GE if the design is found to be defective, but that would be a product liability claim, not litigation over the AD itself.

The cycles vs. hours correction for the D1F engine. The most easily overlooked detail is the change from “cycles” to “hours” in the D1F reinspection interval. Operators that still hold the original 20 January 2005 version of the AD and have not incorporated Amendment 1 may believe the interval is 250 cycles‑since‑last‑inspection for all engines, when in fact it is 250 CSLI only for D1F engines with 5.0 or more hours per flight leg, and 400 CSLI for all others. If an operator mistakenly applies the 250‑cycle interval to a non‑D1F engine, it is complying with a stricter requirement than necessary, which increases downtime. If it applies the 400‑cycle interval to a D1F engine that flies 5+ hours per leg, it may be non‑compliant. The correct interval depends on both engine model and average flight leg duration.

Multi‑configuration engine operation. The AD requires operators to “use the lowest applicable initial inspection threshold” for engines operated in more than one thrust level. This means an engine that has been operated at a lower thrust level for most of its life but was once run at a higher thrust level must use the lower threshold (i.e., more frequent inspection) of the higher‑thrust model. This could catch operators who acquire a used engine with an unknown history. The AD also requires using the “reinspection intervals associated with the current engine model.” If the thrust level changes after the initial inspection, the reinspection interval may change, potentially giving more or less time than expected.

Affected parts with conditional applicability. The most complex “gotcha” is the “Provided that” column in Table 1. Some P/N ranges are affected only if a specific insert (P/N 1957M40G01 or 1957M40G02) was installed during repair or modification. Others are affected only if the part was repaired by GE during a particular 18‑month window (1 April 1998 to 30 September 1999). This requires the operator to trace the part’s entire repair history. A part that nominally has a “clean” P/N may become affected if the insert was installed at any point, even if the insert was subsequently removed. The AD does not specify how to treat parts with multiple repairs; the safest approach is to treat any part that ever had the insert installed as affected, unless the part has been returned to a configuration without the insert by an approved repair.

Reliance on GE Service Bulletin revision. The AD references Revision 6 of GE SB CF6-80C2 S/B 72-0952 dated 5 May 2003. If GE releases a later revision, the AD does not automatically adopt it. The operator must use Revision 6 unless CASA issues a new AD. This means an operator that uses a later revision must still ensure that the inspection performed meets the AD’s explicit requirement to follow paragraphs 3.B.(3) through (5) of Revision 6. A later revision may change the inspection technique or the acceptance criteria, and if those changes are not reflected in the AD, the operator could be non‑compliant if it relies on the later revision’s different method.

No AMOC language. As noted, the AD does not mention alternative means of compliance. An operator that believes a different inspection method (e.g., a different type of borescope or a different inspection interval) would provide equivalent safety must apply to CASA for a specific exemption or variation. There is no automatic right to deviate.

Step 1: Identify affected engines. Obtain a list of all CF6-80C2 engines in the fleet that have the model designations listed in the AD. For each engine, determine the current NGV P/Ns and their repair history. This requires accessing the engine log books, the module histories, and any repair tags from authorised repair stations. If records are incomplete, the operator must assume the part is affected, because the AD does not provide a grace period for missing data.

Step 2: Determine applicability for each NGV. Cross‑reference each NGV P/N with Table 1. Check the “Provided that” condition. For example, if the NGV is P/N 9373M80G07 through 9373M80G22, it is affected only if insert P/N 1957M40G01 or 1957M40G02 was installed during repair, or if it was repaired by GE between 1 April 1998 and 30 September 1999. If the insert was never installed and the part was not repaired by GE in that window, the part may be outside the AD. But because the AD gives no self‑determination method, the operator should document the basis for exclusion.

Step 3: Establish initial inspection schedule. For each affected NGV, note the engine model in which it is installed and the HPT CSO at the effective date of the original AD (20 January 2005). Apply the following thresholds: for models A2, B2, B2F: inspect at or before 1,600 CSO; for all other listed models: inspect at or before 800 CSO. For engines that already exceeded the threshold as of 20 January 2005, inspect within 200 additional CSO after that date. If the engine has been operated in multiple configurations, use the lowest threshold (i.e., if it has ever been operated as a non‑A2 model, use 800 CSO).

Step 4: Perform flex‑boroscope inspection. Obtain a copy of GE Service Bulletin CF6-80C2 S/B 72-0952 Revision 6. The inspection must be performed following paragraphs 3.B.(3) through (5). Use a qualified inspector with current borescope training. The inspection is to be performed without removing the NGV from the engine, though it may require removal of other components for access.

Step 5: Determine reinspection or removal. After inspection, consult Figure 5, Sheets 1 and 2, of the Service Bulletin. For cracking that falls within reinspection criteria, record the finding and schedule the next inspection. For D1F engines with average flight leg of 5.0 hours or more, the reinspection interval is 250 CSLI; for all other engines, 400 CSLI. For cracking that exceeds the removal criteria, replace the NGV before further flight.

Step 6: Maintain records. The operator must retain evidence of compliance for each affected engine: the engine model, NGV P/N, repair history, inspection report, and date of next required inspection. This record should be kept in the continuing airworthiness record system and be available for CASA audit. The record should also note whether the engine has ever been operated in a multi‑configuration and what threshold was applied.

Step 7: Review fleet after Amendment 1. If the operator had already performed inspections under the original AD for D1F engines using a cycles‑based interval, it should verify that those inspections were done at the correct 250 CSLI interval. If the original erroneous “cycles per flight leg” language was used, the operator may have performed inspections too frequently (if 5.0 cycles per flight leg was interpreted as 5.0 cycles per flight, which would be the same as 5.0 hours for a typical sector, but mathematically could be different). The safer approach is to treat the amendment as clarifying, not changing, the intended interval and to check that no D1F engine flew more than 250 cycles without an inspection. If any did, the operator should ground and inspect as soon as possible and notify CASA.