AD/MU-2/65 Amdt 1 - Engine Torque Indication System

The central concept is the torque indication system, which comprises torque transmitters, torquemeters, and torque transducers that measure engine power output. The directive distinguishes two groups of aircraft: Model MU-2B, -10, -15, -20 and -30 aeroplanes (Requirement 1) and Model MU-2B-25, -26, -35 and -36 aeroplanes (Requirement 2). For the first group, the requirement is to inspect the torque indication system per MHI Service Bulletin (SB) No. 233A dated 14 January 1999 (or later JCAB-approved revision) and repair or replace the torque transmitter if errors exceed allowable limits. For the second group, separate inspections are required for the torquemeter and the torque transducer; if transducer output voltage exceeds limits, adjustment is required. A ground check of the engines (Requirement 3) is then required for all applicable aeroplanes, in accordance with paragraph 3 of SB 233A. The ground check likely involves running the engines on the ground and comparing indicated torque with a power assurance chart. The Power Assurance Chart is a document that must be included in the AFM; Note 1 reminds that the AFM must be amended to the current approved revision. The AFM is a legally required document for aircraft registration. The directive also introduces the concept of "time in service" (TIS) as the compliance trigger: within 100 hours TIS after the effective date. TIS is a common metric in aviation, measured from the last maintenance event or from new. The directive uses "before further flight" for corrective actions, meaning the aeroplane cannot fly until the discrepancy is rectified. The background identifies the safety risk: uncalibrated torque indication can mask an actual power mismatch between engines, leading to asymmetric thrust and degraded handling. The Japan Civil Aviation Bureau (JCAB) is referenced as the approving authority for revisions to the SB, reflecting the design jurisdiction of the aircraft (Mitsubishi is Japanese). The directive itself is a CASA instrument, exercising delegated powers under the Civil Aviation Act 1988. It is an amendment to AD/MU-2/65, meaning the original directive is still in force but modified. The concept of "airworthiness directive" is a mandatory continuing airworthiness requirement; failure to comply renders the aircraft unairworthy and its certificate of airworthiness may be invalid. The directive does not specify who must perform the work; typically it is a licensed aircraft maintenance engineer (LAME) or an approved maintenance organisation (AMO). The directive also implicitly uses the concept of "allowable limit" from the SB; these limits are not reproduced in the directive but are incorporated by reference. That imposes an obligation on operators to obtain and follow the SB.

The directive directly affects owners and operators of the specified Mitsubishi MU-2 series aeroplanes: Model MU-2B, -10, -15, -20, -25, -26, -30, -35 and -36, with serial numbers (S/N) 008 through 347 for some models and 501 through 696 for others, with specific exclusions (S/N 313, 321, 652, 661). This covers a limited fleet of approximately 535 aircraft, though many may no longer be in service. The directive affects both Australian-registered and foreign-registered aircraft operated in Australian territory, as CASA has jurisdiction. Maintenance organisations that service these aircraft will be affected: they need to have access to MHI SB No. 233A (or later revision), train staff on the specific inspection and adjustment procedures, and acquire any specialised tooling. Parts suppliers and engine overhaul shops may see demand for torque transmitters, torquemeters, and transducers. Insurance companies may require evidence of compliance as a condition of coverage. The Civil Aviation Safety Authority is affected as the enforcing body, and its delegates issue these directives. Mitsubishi Heavy Industries is indirectly affected as the design authority; the directive relies on its service bulletin. Japan Civil Aviation Bureau is involved as the approving authority for the SB. The directive also affects buyers and sellers of these aircraft: non-compliance must be disclosed, and the cost of compliance may reduce resale value or be negotiated as a condition of sale. Lessors and financiers of affected aircraft will require proof of compliance to protect their security interest. The general public is affected only insofar as safety risk is mitigated, but they bear the cost indirectly through higher airfares or charter rates if operators pass on compliance costs. There is no exemption for private owners; all affected aircraft must comply regardless of usage (commercial, private, aerial work). The directive does not distinguish between high-utilisation and low-utilisation aircraft; the 100-hour TIS compliance period may be reached quickly for charter operators but could take years for owner-flown aircraft. This creates a disproportionate burden on low-use owners for whom the directive may trigger costs before the next scheduled maintenance. The background states that the original directive became effective 10 March 1999, meaning some aircraft may have already been inspected under the original; they still must do the new ground check. So even owners who complied previously are affected by the amendment.

The directive imposes duties on the operator or owner of each affected aircraft. The primary duty is to ensure that the torque indication system is inspected, repaired, replaced, adjusted, and the ground check performed within the prescribed compliance times. Specifically, for Requirement 1.a. and 2.a. and 2.c., the duty is to inspect within 100 hours TIS after 9 March 2007. For Requirement 1.b., 2.b., and 2.d., if errors are found, the duty is to repair or replace before further flight. For Requirement 3, the duty is to accomplish a ground check within 100 hours TIS. For Requirement 4, the duty is to repair any discrepancies noted during the Requirement 1 check before further flight. Note 1 imposes a duty under Civil Aviation Regulation 55 to ensure the AFM is amended to the current approved revision. This duty exists independently of the Directive, but the Directive reinforces it by requiring the Power Assurance Chart to be in the AFM. Implicit duties include: obtaining a copy of MHI SB No. 233A (or later revision), ensuring the person performing the work is appropriately authorised, and maintaining records of compliance. The right of the operator is to continue flying the aircraft only if compliant. If the aircraft is found non-compliant, CASA may issue a grounding order, suspend the certificate of airworthiness, or take enforcement action. The operator has the right to seek an alternative means of compliance (AMOC) from CASA if they can demonstrate equivalent safety, though the directive does not explicitly mention AMOC. The operator also has the right to request an extension of the compliance time if they can show good cause, but the directive does not grant that right; it would need a separate approval from CASA. The directive does not grant any right to compensation for costs incurred. Maintenance organisations performing the work have a duty to follow the SB accurately and certify the work. They have a right to be paid for their services. The CASA delegate (in this case David Punshon) has the authority to issue the directive as a delegate of CASA. The directive itself does not create any private right of action for passengers or third parties. However, non-compliance could be used as evidence of negligence in a civil suit. The directive also interacts with the operator's duty under the Civil Aviation Safety Regulations to maintain the aircraft in an airworthy condition. The directive is a legal instrument with binding force; ignorance of it is no defence.

The directive itself does not prescribe specific penalties, but it is issued under the Civil Aviation Act 1988 and the Civil Aviation Regulations (CARs). Failure to comply with an airworthiness directive is a breach of the regulations. Under CAR 42 (as in force in 2007), an operator who operates an aircraft that does not comply with an applicable AD is guilty of an offence. The maximum penalty for an individual is 50 penalty units (then $5,500) and for a body corporate 250 penalty units ($27,500). Additionally, CASA can suspend or cancel the certificate of airworthiness or registration. The aircraft may be grounded until compliance is achieved. There may also be civil penalties under Part 4 of the Civil Aviation Act for operating an unairworthy aircraft. Enforcement actions include administrative action (warning letters, directions to ground), infringement notices (on-the-spot fines), and prosecution. The directive is mandatory; there is no voluntary compliance option. The CASA delegate issued this directive as a legal instrument; it is not advisory. Note that the directive references JCAB AD TCD-4889-1-2006, a Japanese airworthiness directive. If the aircraft is Australian-registered, CASA's directive takes precedence. However, if the aircraft is on the Australian register but operated overseas, compliance with this directive is still required. The enforcement consequences extend to maintenance organisations who certify work not compliant with the SB; they could face disciplinary action from CASA, including suspension of their approval. For individual licensed aircraft maintenance engineers, failure to properly perform the required inspections could result in action under the CARs or the Act, including loss of licence. There is also potential for criminal liability if a non-compliant aircraft crashes and the cause is traceable to non-compliance, though the directive does not create strict liability for accidents. The background identifies the risk as degraded performance or handling qualities; an accident resulting from non-compliance could lead to charges under the Criminal Code or OHS legislation, but that is beyond the scope of this directive. The directive itself does not provide for any grace period beyond the stated compliance times; once the 100-hour TIS is reached, compliance is due. If the aircraft has already exceeded 100 hours TIS since the effective date, compliance must be immediate. Enforcement is at CASA's discretion; they may take a proportionate approach, but the authority to ground an aircraft is absolute. The directive does not mention record-keeping requirements explicitly, but under CAR 47, maintenance records must be kept. Non-compliance with record-keeping is a separate offence. In summary, while the directive does not list a specific fine, the existing regulatory framework provides substantial penalties and enforcement tools.

This directive interacts with several layers of Australian aviation law. Primarily, it is issued under the Civil Aviation Act 1988 (Cth) and the Civil Aviation Regulations 1988 (CAR) , specifically regulation 42A or similar empowering provisions for CASA to issue airworthiness directives. It requires compliance with MHI SB No. 233A, which is a design organisation's service bulletin. The directive incorporates that bulletin by reference, giving it legal force. It also references JCAB AD TCD-4889-1-2006, the Japanese equivalent, indicating harmonisation between CASA and JCAB but not requiring compliance with the Japanese AD; CASA's directive stands alone. Civil Aviation Regulation 55 is explicitly referenced in Note 1, requiring the AFM to be amended to the current approved revision. The AFM is a regulatory document approved by CASA; unauthorised changes are a breach. The directive's requirement to include a Power Assurance Chart in the AFM triggers the need for a formal amendment under CAR 55. This may require CASA approval of the AFM revision if the chart is not already included. The directive interacts with Civil Aviation Safety Regulations (CASR) Part 42 (Continuing Airworthiness) and Part 145 (Maintenance Organisations) which were being phased in at the time. Operators must ensure maintenance is carried out by an approved organisation or LAME under those rules. The directive does not override the CASA Manual of Standards (MOS) but works alongside it. For aircraft imported from Japan, the directive may interact with bilateral agreements between Australia and Japan; however, no such agreement is referenced. The directive also interacts with the Civil Aviation (Carriers' Liability) Act in a tort context; non-compliance could be evidence of negligence. The Work Health and Safety Act may apply if maintenance workers are exposed to hazards during these procedures; the directive does not address that. Privacy laws do not apply. Competition and Consumer Act 2010 may apply if parts or labour prices are affected, but that is not within the directive's scope. The directive does not conflict with any state laws because aviation is a Commonwealth matter. For operators with multiple registrations (e.g., aircraft on both Australian and US registers), they must comply with both CASA's AD and FAA's AD for this model (if any). The directive’s 100-hour TIS requirement may conflict with other scheduled maintenance intervals; operators may need to coordinate to avoid unnecessary downtime. There is no explicit provision for such coordination. Also, note that the directive amends a previous AD; it does not revoke it. So the original requirements still apply unless superseded. The original AD is still in effect; this amendment adds the ground check. Therefore, any operator who had not complied with the original AD must still comply with it as well. This cumulative effect increases compliance burden. The directive does not mention Environmental Protection Act or noise restrictions, as it concerns engine power measurement. In essence, this directive operates within a web of regulations that collectively govern the safety and airworthiness of Australian aircraft.

The original AD/MU-2/65 became effective on 10 March 1999. This is explicitly stated in the source: "The original issue of this Directive became effective on 10 March 1999." That original directive required the inspection and, if necessary, repair, replacement or calibration of the torque indication system, as summarised in the background. The original directive was issued by CASA (or its predecessor) under the same civil aviation framework. This current document is Amdt 1, meaning it is the first amendment to the original. The amendment was signed by David Punshon, Delegate of CASA, on 28 February 2007, and becomes effective on 9 March 2007. The amendment introduces: (a) a ground check of the engines following the inclusion of a Power Assurance Chart in the AFM (Requirement 3); (b) a new Requirement 4 to repair discrepancies noted during the Requirement 1 check (though this may have been implicit before, it is now explicit); (c) the new compliance times for Requirements 3 and 4; and (d) updated Note 2 referencing the JCAB AD. The amendment does not change the applicability or the substantive requirements for inspection and repair; those remain the same as the original. The background explicitly states: "This amendment introduces a ground check of the engines following the inclusion of a Power Assurance Chart in the AFM." It also notes that the original issue of this Directive required the inspection and, if necessary, the repair, replacement or calibration. So the amendment is additive. There is no mention of any interim amendments or subsequent amendments to this AD after 2007. The source does not indicate whether this AD has been further amended, superseded, or withdrawn. In practice, many older ADs remain in force until the aircraft type is no longer supported. The amendment history is thin: only one amendment. The directive is dated 2007, and we are writing in 2025, so it is likely still in effect unless superseded by a newer AD or the aircraft type has been retired from the Australian register. The source provides no information about any cancellation. The amendment was likely prompted by MHI or JCAB issuing a revision to the SB or by incidents that indicated the need for a power assurance ground check. The background does not detail triggering events, only that MHI reported calibration issues. The amendment process under CASA involves consultation with industry, but the source does not reveal that. The original AD number is AD/MU-2/65; the amendment is Amdt 1. The CASA documentation number is 4/2007 DM, likely a filing code. There is no amendment history table; we only have the two effective dates (1999 and 2007). The amendment is a relatively minor addition, but it imposes a new compliance action on operators who had already complied with the original. This is a typical pattern: as more information becomes available, regulators tighten requirements. Operators who had already done the inspection under the original may have thought their obligation ended; this amendment revives compliance obligations. This is an example of regulatory creep without new risk being necessarily quantified. The cost to operators of re-entering the hangar for a ground check when they had already done the torque system inspection may be hard to justify if the original inspection already ensured torque indication accuracy. The amendment overlooks the possibility that the original inspection was already adequate; the ground check adds a verification step using a power assurance chart that may not have been previously available. This history shows a learning process or a response to reported issues that were not initially foreseen.

The source document provides no reference to any litigation involving this specific airworthiness directive. There is no mention of court cases, appeals, or judicial review. This is not unusual for a technical, low-profile AD affecting a small fleet of aircraft. However, we can infer that if an owner or operator had challenged the original 1999 AD or this 2007 amendment, they could have sought review in the Administrative Appeals Tribunal (AAT) or the Federal Court under the Administrative Decisions (Judicial Review) Act 1977. Grounds could include that the directive was unreasonable, disproportionate, or beyond power. But no such challenge appears in the public record (the source is silent). Also, there could be litigation arising from accidents where non-compliance with this AD was alleged. For example, if a MU-2 crashed due to a power mismatch and the torque indication system had not been inspected per this AD, the operator could face negligence claims. However, the source does not mention any accident. In Australian aviation law, the Civil Aviation Act generally excludes civil liability for CASA in issuing directives (section 30), but that does not protect operators. We cannot name any case because the source does not name any. To satisfy the requirement that we do not invent, we will state that the source contains no reference to litigation history. It is likely that this AD has not been the subject of reported decisions. The background itself is silent on any incidents; it only says MHI reported calibration issues. So we must conclude that there is no litigation history directly associated with this AD. However, we can note that Mitsubishi MU-2 aircraft have been subject to other litigation in other jurisdictions (e.g., FAA actions in the US), but that is beyond the source. To stay grounded, we will avoid that. For this deep dive, readers should know that no litigation is recorded. The lack of litigation may indicate that operators accepted the directive, or that compliance costs were low enough not to justify legal action, or that the fleet is too small to generate high-profile disputes. It could also mean that any disputes were settled quietly. The directive itself is clear and technical, leaving little room for interpretive disputes. The only potential dispute is over the meaning of "errors in the torque indication system" or "allowable limit" but those are defined in the SB. The directive does not specify what constitutes a discrepancy in Requirement 4; that is left to the SB as well. Without litigation, there is no case law interpreting this directive. Therefore, the legal risk lies in the interpretation of the SB, which is a manufacturer document. If MHI revises the SB later, the directive allows "later revision approved by JCAB", so that could cause compliance uncertainty. But no litigation has clarified whether an operator could use an earlier revision if later one is more onerous. In sum, litigation history is nil as per the source.

Several aspects of this directive may catch operators off guard. First, the compliance clock starts from "the effective date of this Amendment" (9 March 2007) but is measured in "time in service" (TIS) hours. Operators must track the aircraft's TIS since that date. If the aircraft was not flown, the 100 hours may never be reached, but the obligation remains indefinite until TIS accrues. However, if the aircraft flies beyond 100 hours TIS without performing the required actions, it is immediately non-compliant. Second, the directive requires that any discrepancies found during the Requirement 1 check be repaired before further flight. The term "discrepancies" is not limited to torque indication errors; it could include any anomaly found during the inspection, even unrelated ones, if the inspection procedure uncovers them. The SB may define the scope, but the directive is silent. Third, Requirement 4 is a catch-all: "Repair any discrepancies noted during the Requirement 1 check." Note that Requirement 1 is the torque indication system inspection. But Requirement 2 inspections are separate; discrepancies from Requirement 2 are not explicitly covered by Requirement 4. However, Requirement 2.b and 2.d require repair before further flight, so they are covered individually. Gotcha: if a discrepancy is found during inspection of the torquemeter (Requirement 2.a) that is not related to torque errors, must it be repaired? The directive says to repair or replace if errors exceed limit, but other discrepancies (e.g., cracks, corrosion) are not addressed. The operator should still follow general airworthiness rules, but the directive itself only mandates repair of specific torque errors. This may lead to confusion. Fourth, the ground check (Requirement 3) must be accomplished within 100 hours TIS after effective date, but it does not say "if not previously accomplished" as the other requirements do. So every affected aircraft must do this ground check, even if they already did it as part of the original directive or voluntarily. This could be an unnecessary duplication. Fifth, the directive does not provide an easy way to verify if an earlier revision of the SB was used. If an operator complied with the original 1999 AD using an earlier revision of SB 233A, that may not satisfy the new amendment if JCAB approved a later revision. The directive says "later revision approved by JCAB", so using an earlier revision might not be acceptable for the new inspections. But if the system was already inspected and found compliant under the older revision, does that satisfy the new requirements? The directive does not grandfather previous compliance. Sixth, the AFM amendment (Note 1) is a separate regulatory requirement under CAR 55. The holder of the Certificate of Registration is responsible, not the maintenance organisation. Many operators overlook the need to update the AFM. The directive itself does not specify which revision of the Power Assurance Chart must be included; it just says "the current approved revision". That creates ambiguity if the AFM is out of date. Seventh, the directive applies to specific serial numbers but excludes a few. If an operator has an excluded serial number, they are unaffected, but they must verify that the serial number is indeed excluded. There is a risk of misidentification. Eighth, the directive is referenced as "4/2007 DM" which is a CASA internal number; operators might not search under that when checking for compliance. Ninth, the original directive effective 10 March 1999 had its own compliance times; some operators may have already complied but lost records. The amendment does not mention records, but proof of compliance is essential. Tenth, the directive references JCAB AD TCD-4889-1-2006 in Note 2. While not requiring compliance with that AD, it may create confusion. Operators might think it is an alternative standard. It is not; it is just a cross-reference. Finally, the directive does not state any alternative means of compliance (AMOC) process. Operators may assume CASA will accept equivalent procedures but there is no formal process outlined. If MHI issues a later revision of the SB that changes the tests, operators must use that later revision. That could increase costs unpredictably.

Compliance requires a step-by-step approach. First, identify whether the aircraft is on the applicable model and serial number list. For Model MU-2B, -10, -15, -20, and -30, serial numbers 008 through 347 except 313 and 321. For Model MU-2B-25, -26, -35, and -36, serial numbers 501 through 696 except 652 and 661. If the aircraft is included, compliance is mandatory. Second, obtain a copy of MHI Service Bulletin No. 233A dated 14 January 1999 or the latest revision approved by JCAB. This bulletin details the inspection procedures, allowable limits, and adjustment/repair methods. Third, schedule the aircraft for maintenance within 100 hours time in service after 9 March 2007. That means before the aircraft accumulates 100 flight hours from that date. If the aircraft has already flown more than 100 hours since that date, compliance must be immediate. Fourth, for aircraft in the first group, perform the inspection of the torque indication system per the SB. For the second group, perform separate inspections of the torquemeter and torque transducer per the SB. If errors exceed allowable limits, repair or replace the torque transmitter (first group) or torquemeter and adjust transducer output voltage (second group) before further flight. Fifth, perform a ground check of both engines in accordance with paragraph 3 of SB 233A. This likely involves running the engines to rated power and verifying torque readings against the Power Assurance Chart. Sixth, ensure the Aircraft Flight Manual has been amended to include the current approved Power Assurance Chart. This may require contacting the manufacturer or CASA for the correct revision. Seventh, document all actions in the aircraft maintenance logbook and keep copies of the SB used, the inspection results, and any parts replaced. Eighth, if any discrepancies are found during the Requirement 1 inspection, repair them before further flight, even if they are not torque-related; but at minimum, repair those specifically required by the SB. Ninth, verify that the work was carried out by an appropriately licensed aircraft maintenance engineer or approved maintenance organisation. Tenth, keep a record of the compliance date and TIS reading for future reference. There is no requirement for recurrent compliance under this AD, but the aircraft remains subject to ongoing airworthiness requirements. If the aircraft is sold, the new owner should be notified of compliance. The directive does not require reporting to CASA; compliance is self-verified. However, CASA can audit. Operators should be aware that the original 1999 AD may have required similar actions; ensure that any previous compliance is documented and that the new ground check is added. Maintenance organisations should have the SB on hand and train staff. The cost will vary: inspection alone may be a few hundred dollars, but replacement of torque transmitters could be thousands. The ground check involves engine run time and fuel consumption. The best strategy is to combine this directive with scheduled maintenance to minimise downtime. Operators should not defer beyond the 100-hour TIS limit. Given that the effective date is long past, any aircraft still operating and not yet complied with is already non-compliant; immediate action is needed. The compliance dates are all in the past (as of 2025), so readers should treat this directive as a historical compliance requirement. However, if the directive remains in force, new operators of these aircraft must comply. There is no sunset. Therefore, due diligence for purchasing such an aircraft includes confirming compliance with AD/MU-2/65 Amdt 1.