AD/B747/278 - Thrust Reversers

The AD is built around four structural concepts: fault detection and correction, terminating action, repetitive inspection and test, and fail‑safe integrity.

Fault detection and correction is the initial phase. Requirements 1‑2 and 5‑6 form a loop: inspect wiring, repair any fault, modify, then test, then repair any fault found in the test. The AD relies on specific service bulletins (Boeing ASB 747‑78A2149, Rohr SB TBC‑CNS 78‑32) as the source instructions. The operator has no discretion to adopt an alternative procedure unless the service bulletin itself provides options. The phrase “to detect any discrepancies” appears repeatedly, indicating that the inspection is a pass‑fail gate: any deviation from the service bulletin’s standard constitutes a discrepancy requiring immediate repair.

Terminating action is a central design of the AD. Requirements 9, 10, and 11 together form a terminating modification that, once accomplished, ends the need for the repetitive inspections and tests of Requirement 7 (the 1,000‑hour and 18‑month checks). The AD explicitly states: “Accomplishment of Requirements 9, 10 and 11 constitutes terminating action for the Requirement 7 repetitive inspections and tests.” This is a classic regulatory mechanism to shift from a temporary, higher‑burden inspection regime to a permanent (and presumably lower‑burden) design fix. However, Requirement 12 then introduces a new repetitive test of the locking system itself, so the terminating action does not eliminate all future compliance obligations; it merely replaces one set of repetitions with another. The operator must therefore budget for both the initial high‑effort modifications and the ongoing 4,000‑hour sync‑lock integrity test.

Repetitive inspection and test applies to two separate regimes. The first (Requirement 7) is dual: a 1,000‑hour inspection and an 18‑month system check. The second (Requirement 12) is a 4,000‑hour functional test of the sync‑lock mechanism using the detailed procedure in Appendix 1. The intervals are measured in flight hours or calendar time (months), not in flight cycles for the repetitive checks, except that the initial modification compliance (Requirement 3) uses the later of 5,000 flight hours or 500 flight cycles. This dual metric matters for operators with high‑cycle short‑haul usage: a 500‑cycle limit might be reached before 5,000 hours, so the “later” election gives a slight buffer, but only for the initial wiring modification, not for the ongoing tests.

Fail‑safe integrity is the stated purpose. The AD speaks of “the integrity of the fail‑safe features of the thrust reverser system” and “preventing possible failure modes, which could result in inadvertent deployment.” The sync‑lock integrity test (Appendix 1) is a manual procedure designed to verify that the left‑hand and right‑hand sync‑lock levers prevent sleeve movement when locked, using a torque‑limited manual deployment attempt (75 pound‑inches maximum). If the sleeves move at all, the sync‑lock must be replaced. This is a mechanical check of a passive safety device. The AD also includes a caution not to apply more than 25 pound‑inches when verifying latch engagement via feedback gear rotation, and a rotation limit of 0.1 turn. These numeric thresholds are prescriptive and non‑negotiable; deviation from the procedure is itself a discrepancy.

The AD directly imposes obligations on operators and maintainers of Boeing 747 series aeroplanes equipped with Pratt & Whitney JT9D‑70 series engines that are registered in Australia or operated under Australian regulatory authority (since the AD is issued under CAR 1998). This includes airlines, charter operators, cargo operators, any private or government operators of such aircraft, and any maintenance organisation performing work on those aircraft under an approved maintenance organisation (AMO) or equivalent arrangement. The AD also indirectly affects lessors, insurers, and buyers of such aircraft because compliance is a condition of continued airworthiness.

The specific model applicability is “Model 747 series aeroplanes equipped with Pratt & Whitney JT9D‑70 series engines.” The text does not limit to any subtype (e.g., 747‑100, 747‑200, 747‑300, 747‑400). The reference to Pratt & Whitney JT9D‑70 series engines suggests the AD targets the larger engine variant, not the earlier JT9D‑3 or JT9D‑7. Any operator who has a 747 with that engine must comply, regardless of whether the aircraft is used for passenger, cargo, or other operations.

Geographically, the AD was gazetted in the Commonwealth of Australia Gazette on 11 September 2002 and becomes effective on 3 October 2002. It applies to aircraft operating in Australian airspace or under an Australian Certificate of Airworthiness. It also applies to Australian‑registered aircraft operating abroad? The source text does not include an explicit extraterritorial clause, but CAR 1998 generally applies to Australian‑registered aircraft wherever located. The FAA AD (2000‑10‑17) is noted for reference, indicating that a corresponding FAA directive exists for US‑registered aircraft, so operators with US‑registry would need to comply with the FAA version. The CASA AD may also affect foreign operators who bring their aircraft into Australian airspace if CASA requires compliance with its own ADs for foreign‑registered aircraft (common under bilateral agreements), but the text does not specify that.

The compliance timeline creates differential burdens. Operators who have already accomplished any of the service bulletins before the effective date may be able to credit that work, but the AD does not explicitly grant credit. The phrase “in accordance with ASB 747‑78A2149, Revision 1 or Revision 2” suggests that work done to an earlier revision (e.g., the original issue) may not be acceptable. Operators with high‑utilisation aircraft (e.g., long‑haul freighters) will reach hour‑based compliance limits sooner; those with low utilisation may have calendar‑time limits (e.g., 18‑month check) that bite earlier. For an aircraft that is not in service on the effective date (e.g., stored or undergoing heavy maintenance), the requirement to inspect before issuance of a Certificate of Airworthiness (Requirement 1) imposes a gate that prevents re‑entry to service without the wiring inspection. For aircraft already in service, the first 1,000‑hour inspection (Requirement 7(a)) must be done within 90 days, which is a relatively short lead time and may require scheduling resources.

The AD imposes no obligations on the original equipment manufacturer or the type certificate holder; it is purely an end‑user directive. However, the service bulletins referenced are proprietary documents that must be purchased from Boeing or Rohr, adding a cost of access. The AD does not include any alternative equivalent procedures or a mechanism for requesting alternative means of compliance, although subregulation 39.1 of CAR 1998 generally permits that under limited conditions (not discussed in the AD). Operators must therefore ensure they have current copies of all referenced service bulletins and that they are using the correct revision.

The primary duty is to accomplish each requirement by the specified compliance time and in accordance with the referenced service bulletin instructions. The duty is strict: no defence of impracticality or economic hardship is provided within the AD text. The operator must also ensure that any discrepancy found during any inspection or test is corrected before further flight (Requirements 2, 6, 8, 13). This is a classic “airworthiness limitation” that grounds the aircraft if a discrepancy remains uncorrected. The duty extends to repeating any failed test after repair (Requirement 8: “any failed inspection or test must be repeated and successfully accomplished”).

Another duty is recordkeeping. The AD does not explicitly state recordkeeping obligations, but under CAR 1998, compliance with ADs must be recorded in the aircraft’s maintenance records. The AD is itself a mandatory directive, and failure to record compliance would be a separate regulatory breach.

Rights of the operator are minimal in the source text. The operator has the right to choose between Revision 1 and Revision 2 of Boeing ASB 747‑78A2149 for several requirements (1, 2, 3, 5, 6, 10). The operator may also choose to accomplish the terminating modification (Requirements 9‑11) earlier than the 36‑month deadline, which would end the Requirement 7 repetitive inspections earlier, potentially reducing ongoing compliance costs. However, doing so triggers the Requirement 12 repetitive sync‑lock test earlier. So the operator can trade off between two repetitive regimes. The operator also has the right to use the exact procedure in Appendix 1 for the sync‑lock test; any deviation from that procedure would not comply. The operator has no explicit right to extend compliance times or to use alternative methods.

The duty to perform a functional test of the additional locking system (Requirement 12) uses a torque limit of 75 pound‑inches for manual sleeve deployment and 25 pound‑inches for feedback gear rotation. Exceeding these limits would not comply with the AD, and likely damage the mechanism. The operator’s duty includes training and tooling: the flex drive adapter (part numbers 196K8004‑1 or 196K8004‑3) must be available. Without that tool, the test cannot be performed in compliance.

The operator also has a duty to coordinate concurrent activities. Requirement 4 ties to Requirement 3; Requirement 10 ties to Requirement 9; Requirement 11 ties to Requirement 9. These concurrent compliance deadlines mean that all work on a given engine must be grouped tactically. For example, Requirement 3 (wiring modification) and Requirement 4 (Rohr SB wiring modification) must be done concurrently. The operator cannot do the wiring modification and delay the Rohr modification to a separate maintenance visit; both must occur at the same time.

The operator’s right to repair using the Boeing 747 Aeroplane Maintenance Manual (Requirement 13) is limited to correcting discrepancies found during the sync‑lock test. For other repairs, the AD specifies the service bulletins (e.g., Requirements 2, 6, 8). So the operator cannot use the maintenance manual as an alternative for the wiring or test procedures; only for the sync‑lock functional test repairs.

The AD itself does not prescribe specific penalties, but it is issued under subregulation 39.1(1) of CAR 1998. Non‑compliance with an AD is a breach of the Civil Aviation Regulations. Under the relevant provisions (not reproduced in the source but part of the framework), a person who contravenes an AD may face penalties including fines, suspension or cancellation of the aircraft’s Certificate of Airworthiness, suspension of the operator’s Air Operator Certificate, and potential criminal liability in cases of reckless endangerment. The source does not provide specific dollar amounts, but historically, CASA has the power to issue infringement notices with penalties up to several thousand dollars per breach, and civil penalty provisions can be much higher for corporations.

Enforcement mechanisms include grounding of the aircraft. The AD itself implies grounding through phrases such as “prior to further flight” (Requirements 2, 5, 6, 8, 13). If an operator fails to perform a required inspection or test at the mandated interval and does not ground the aircraft, CASA can issue a further enforcement direction. Additionally, the AD is gazetted, making it a public legal instrument. CASA delegates (like James Coyne) are authorised to issue the AD, and CASA inspectors have the power to audit compliance records.

The AD does not include any graduated compliance scheme or grace period beyond the stated compliance times. The effective date is 3 October 2002. For Requirement 7(a) (first 1,000‑hour inspection within 90 days), the last possible day is 1 January 2003. For Requirement 7(b) (first 18‑month check within 1,500 hours TIS or four months after the effective date, whichever occurs later), that could be as late as 3 February 2003 if the hour limit is not reached earlier. But for the wiring modification (Requirement 3), the operator has up to 5,000 flight hours or 500 cycles after the effective date, potentially a long period for low‑utilisation aircraft. The AD does not have a phase‑in; it is a single effective date.

The note “FAA AD 2000-10-17 Amdt 39-11741 refers” suggests that the FAA had already issued a similar directive in 2000. Australian operators who had already complied with the FAA AD and had the aircraft registered in the US could potentially be in compliance if the CASA AD matches. However, the CASA AD is not identical: it references specific Boeing and Rohr service bulletins with specific revision dates. Any difference in revision levels could create a gap. For instance, if the FAA AD referenced Revision 1 only, and the CASA AD allows Revision 1 or 2, an operator who complied with Revision 2 under the FAA AD would also comply with CASA, but an operator who complied with an earlier revision (not listed) would not.

The AD does not provide a “no hazard” exemption or allow the operator to defer if the aircraft is in storage or being retired. If the aircraft is not in service on the effective date, Requirement 1 (inspection before Certificate of Airworthiness) still applies before it can return to service. An operator who intends to part out the aircraft may still need to comply before any ferry flight under a special flight permit.

This AD is issued under the Civil Aviation Regulations 1998 (CAR 1998), specifically subregulation 39.1(1). It is part of the Australian airworthiness regulatory framework that includes the Civil Aviation Act 1988, CAR 1998, and the Civil Aviation Safety Regulations 1998 (CASR 1998 for newer aircraft). For the Boeing 747 series (certified before CASR adoption), CAR 1998 applies. The AD sits alongside other CASA‑issued ADs, which may cover different systems on the same aircraft. Compliance with this AD does not relieve the operator of complying with any other AD affecting the same engine or aircraft type (e.g., ADs for engine control systems, pylon structure, etc.).

The AD explicitly refers to FAA AD 2000‑10‑17, indicating that the unsafe condition was originally identified by the FAA. Under the Bilateral Aviation Safety Agreement (BASA) between Australia and the United States, CASA may adopt or issue its own AD based on FAA findings. Operators should be aware that the FAA AD may have different compliance times or options. For aircraft with dual Australian and US registration or that operate between the two countries, the more restrictive AD (i.e., earlier compliance date) would apply. The CASA AD does not state that compliance with the FAA AD satisfies the CASA AD; the operator must ensure each requirement in the CASA AD is met by the Australian compliance times.

The AD interacts with Part 39 of CAR 1998 generally. Subregulation 39.1(1) allows the delegate to issue an AD when he or she considers that an action is necessary to correct an unsafe condition. The AD is a legislative instrument, and failure to comply is an offence under regulation 39.5 (not quoted but part of the enabling legislation). The AD also interacts with Division 2 of Part 4A of the Act concerning ongoing airworthiness obligations. An operator’s Air Operator Certificate usually requires compliance with all ADs.

The AD also interacts with maintenance regulations. The inspections and modifications must be carried out by appropriately authorised persons (e.g., licensed aircraft maintenance engineers under CAR Part 66, or by an approved maintenance organisation under CAR Part 145). The AD does not specify who is qualified, but the service bulletins may include personnel requirements. The sync‑lock test (Appendix 1) involves manual deployment of thrust reverser sleeves; this is a maintenance task, not a flight crew procedure. The operator must ensure that the maintenance provider has the special tool (flex drive adapter) and is familiar with the torque limits.

There is a potential interaction with occupational health and safety laws in states or territories where the maintenance is performed. The sync‑lock test requires opening fan cowl doors, engaging and disengaging latches, and applying torque to actuators. These are tasks that involve pinch points, awkward positions, and possible exposure to high‑pressure fluids. The AD does not provide safety warnings beyond the torque cautions; the operator must comply with workplace safety laws separately.

The AD also interacts with insurance and leasing agreements. Lessors often require the operator to comply with all ADs. A failure to comply could be a breach of the lease and void insurance coverage. The AD’s reference to FAA AD indicates that the issue is well‑known in the industry; underwriters may require proof of compliance before covering a 747 with JT9D‑70 engines.

The source document is the original AD/B747/278 issued on 20 August 2002, signed by James Coyne as delegate, and gazetted on 11 September 2002, effective 3 October 2002. The source does not contain any amendments or revisions to the AD itself. However, the AD references multiple service bulletins, some of which exist in multiple revisions: Boeing ASB 747‑78A2149 Revision 1 (9 May 1996) and Revision 2 (29 August 1996); Rohr SB TBC‑CNS 78‑32 Revision 1 (20 August 1996); Boeing SB 747‑78‑2153 Revision 1 (27 November 1996); Rohr SB TBC‑CNS 78‑33 Revision 1 (20 August 1996). The AD itself does not include any Revision number (it is AD/B747/278, no suffix). There is no indication that this AD has been superseded by a later directive (e.g., AD/B747/278A or a later number). However, in practice, CASA may have issued later amendments or replacements. Since the source is only this single page, we cannot assume any subsequent history.

The AD’s “Background” section does not refer to any earlier CASA AD; it states the directive is prompted by a FAA safety review. The FAA AD (2000‑10‑17) predates this CASA AD by about two years. The CASA AD effectively adopts the FAA findings and tailors compliance times. The AD does not discuss any consultation or prior notice. The compliance dates are set from the effective date, not from any earlier publication.

The AD does not include an expiration date or a re‑examination requirement. Unless superseded or cancelled, it remains in effect indefinitely. Operators should check the current CASA AD list to see if it has been superseded, as the source document is from 2002 and is now over 22 years old. For a 747 still in service, later ADs may have modified or replaced these requirements.

The source text contains no references to any litigation, court cases, or enforcement actions. The AD itself is not a court judgment. There is no mention of any appeal by an operator, any legal challenge to the validity of the AD, or any case law interpreting the requirements. Given that ADs are legislative instruments issued by a delegate, they can be challenged on administrative law grounds (e.g., jurisdictional error, unreasonableness) under the Administrative Decisions (Judicial Review) Act 1977. However, no such challenge appears in the source.

The absence of litigation history in the source does not mean no litigation exists. It means the AD text does not cite any. The FAA AD referenced (2000‑10‑17) may have faced litigation in the United States, but the CASA AD does not mention that. The operator should be aware that any non‑compliance could lead to enforcement action by CASA, and such actions may result in court proceedings for penalties or for grounding orders. The source text does not provide any such examples.

The AD does not discuss any civil liability for damages arising from failure to comply. Under the Civil Aviation Act, a breach of an AD could be used as evidence of negligence in a tort claim for an accident involving the thrust reverser system. The AD itself notes that “in‑flight deployment of a thrust reverser could result in significant reduction in aeroplane controllability.” That is a clear warning of potential catastrophic consequences. In any subsequent litigation, a plaintiff could argue that compliance with the AD would have prevented the accident. However, no cases are cited.

The AD contains several traps for the unwary operator or maintainer.

Concurrent compliance is mandatory and not flexible. Requirement 4 (Rohr SB wiring modification) must be concurrent with Requirement 3 (Boeing ASB wiring modification). Requirement 10 (provisional wiring for locking system per Boeing SB and ASB) must be prior to or concurrent with Requirement 9 (lock installation). Requirement 11 (Rohr provisional wiring) concurrent with Requirement 9. If an operator does Requirement 3 but not Requirement 4, that is a breach. The AD does not allow staggering these tasks across different maintenance visits. This forces a significant maintenance event because all three or four tasks must be done at the same time per engine.

The terminating modification does not eliminate all repetitive checks. Many operators might assume that after accomplishing Requirements 9‑11, they are done with all repetitive inspections. Wrong. Requirement 7 (1,000‑hour and 18‑month checks) stops, but Requirement 12 introduces a new repetitive test at 4,000‑hour intervals. So the total compliance burden may not decrease; it shifts to a different test.

The sync‑lock test tool must be the specific Rohr adapter. Appendix 1 lists part numbers 196K8004‑1 or 196K8004‑3 from Rohr Industries, California. If an operator does not have that adapter, they cannot perform the test in accordance with the AD. They cannot substitute a generic wrench or another tool, as that would not follow the procedure. The test requires a manual torque of no more than 75 pound‑inches and no more than 25 pound‑inches for the feedback gear. These are very low torque values; a torque wrench with a suitable head is needed.

The test sequence has a critical order. Appendix 1 steps are specific: open circuit breaker, open fan cowl doors, check latches, depress drive unit latch arm, disengage stow latch hooks, remove coverplate or locking plug on a specific actuator (either lower slave actuator, forward drive pad, or lower drive pad). Then move left sync‑lock lever to unlocked position, attempt to manually deploy sleeves using adapter. If sleeves move, replace right sync‑lock. Then move left back to locked, move right to unlocked, repeat. The citation “if sleeves move, replace the right‑hand sync‑lock” could be confusing because the text expects the operator to test each sync‑lock separately by moving the opposite lever. A mistake in this sequence could result in an incorrect diagnosis, leading to unnecessary part replacement or a missed fault.

The torque limits are prescriptive and carry a caution about mechanism damage. Exceeding 75 pound‑inches can cause damage, and exceeding 25 pound‑inches on feedback gear can cause damage. The operator must ensure the tool used is calibrated and the technician applies the correct force. If damage occurs during testing, that becomes a new discrepancy requiring repair per Requirement 13 (which directs use of the maintenance manual). That could then ground the aircraft if the repair is not immediate.

The compliance intervals for Requirement 7 are not reset by terminating action. The AD says that accomplishment of Requirements 9‑11 terminates Requirement 7. It does not say that the operator may stop performing Requirement 7 early if they accomplish the terminating modification before the next interval. The wording uses “constitutes terminating action for the Requirement 7 repetitive inspections and tests.” That means once the terminating modification is done, the repetition obligation ends. But until that modification is done, the operator must keep performing Requirement 7 at the specified intervals. An operator who accomplishes the terminating modification at month 24 (out of 36 allowed) can stop the Requirement 7 checks at that point, even if the 18‑month check would have been due at month 30. That is an advantage. But if the operator delays the terminating modification until month 35, they must still perform the 18‑month check at month 30 (if they have reached the hour or calendar limit earlier), and the 1,000‑hour checks as they accrue.

The note “FAA AD 2000‑10‑17 Amdt 39‑11741 refers” does not mean that FAA compliance automatically satisfies CASA. The operator must check each requirement against the CASA AD. The FAA AD may have different revision levels. Also, the FAA AD may have been superseded or amended. Relying solely on a prior FAA compliance record may overlook CASA‑specific obligations.

Compliance with AD/B747/278 requires a structured approach involving planning, tooling, training, and recordkeeping. The following steps are grounded in the source.

Step 1: Obtain all referenced service bulletins and the AD appendix. The operator must have Boeing ASB 747‑78A2149 (Revision 1 or 2), Rohr SB TBC‑CNS 78‑32 (Rev 1), Boeing ASB 747‑78A2159 (original issue, 18 May 1995), Boeing SB 747‑78‑2153 (Rev 1, 27 Nov 1996), Boeing SB 747‑78‑2135 (31 Aug 1995), Rohr SB TBC‑CNS 78‑33 (Rev 1, 20 Aug 1996), and the Boeing 747 Aeroplane Maintenance Manual (for sync‑lock test repairs). Without these, the instructions cannot be followed.

Step 2: Initial compliance - Requirement 1. Before issuing a Certificate of Airworthiness (or as soon as possible for aircraft already in service), inspect the thrust reverser wiring per the Boeing ASB. This is a one‑time inspection. Log any discrepancies found.

Step 3: Correct discrepancies (Requirement 2) before further flight.

Step 4: Schedule the modifications (Requirements 3, 4, 9, 10, 11) into maintenance planning. Requirement 3 has a compliance time of 5,000 flight hours or 500 flight cycles after 3 Oct 2002 (whichever later). Requirement 9 has 36 months from 3 Oct 2002. These are long lead times, but must be coordinated because concurrent requirements. The operator should aim to accomplish all modifications at one major maintenance visit to avoid multiple downtime events. The modifications include: wiring modification per Boeing ASB, wiring modification per Rohr SB TBC‑CNS 78‑32, installation of additional locking system per Boeing SB 747‑78‑2153, and installation of provisional wiring per Boeing SB 747‑78‑2135 and Rohr SB TBC‑CNS 78‑33. All work per each SB.

Step 5: Perform operational test of thrust reverser wiring (Requirement 5) after completing Requirements 3 and 4, before further flight. This test is per the Boeing ASB. If any discrepancies found, correct per Requirement 6 before further flight.

Step 6: Establish a repetitive inspection program for Requirement 7 until the terminating modification is accomplished. Requirement 7(a) must be done within 90 days of 3 Oct 2002 (i.e., by 1 Jan 2003) and then at intervals not exceeding 1,000 hours TIS. Requirement 7(b) must be done within 1,500 hours TIS or 4 months after 3 Oct (whichever later) and then at intervals not exceeding 18 months. These are calendar and hour triggers; the operator must track both. If the terminating modification is accomplished early, the program can be stopped. But until that point, the operator must perform these checks.

Step 7: After completing the terminating modifications (Requirements 9‑11), the operator must perform the sync‑lock integrity test (Requirement 12) within 4,000 hours TIS after completion, and then at intervals not exceeding 4,000 hours TIS. This test is described in Appendix 1. The operator must have the flex drive adapter (196K8004‑1 or 196K8004‑3). The test must be conducted exactly as per the 23‑step procedure, including the torque limits and the correct sequence of sync‑lock level movements. If any discrepancy is found, the operator must correct it per the Boeing 747 Maintenance Manual (Requirement 13) before further flight.

Step 8: Recordkeeping. Entry should be made in the aircraft maintenance logbook or equivalent for each requirement accomplished, referencing the AD number, the service bulletin used, the date, and any discrepancies found and corrected. For the repetitive tests, the next due date or hours should be calculated and recorded.

Step 9: Ongoing monitoring. For aircraft that remain in service, the operator must ensure the 4,000‑hour sync‑lock test is performed on time. If the aircraft is removed from service for an extended period, the hour‑based interval may not be an issue, but the operator cannot rely on calendar time for this particular test; the interval is purely hours TIS. For aircraft that accumulate hours slowly, the first test may be due many years after the modification.

Step 10: Check for superseding ADs. Because the source AD is from 2002, the operator should verify with CASA whether this AD has been superseded, rescinded, or amended. If a later AD incorporates these requirements, the later AD becomes the compliance baseline. The operator should also check if any alternative means of compliance have been approved by CASA since the AD was issued.

Common pitfalls to avoid: Do not delay the Rohr SB wiring modification (Requirement 4) after doing the Boeing wiring modification; they must be concurrent. Do not perform the sync‑lock test without the correct adapter and a torque wrench that can measure low torque. Do not assume that compliance with FAA AD 2000‑10‑17 suffices; cross‑check each CASA requirement. Do not stop the Requirement 7 inspections if the terminating modification is overdue; continue them until it is done. Do not exceed 75 pound‑inches on the sync‑lock test; this will damage the mechanism and require costly repair. Do not rotate the feedback gear more than 0.1 turn during latch engagement verification. Ensure that “prior to further flight” actions are actually done before the next flight; this may mean delaying a flight if a discrepancy is found at the gate.