{"id":"F2007L00641","name":"AD/CESSNA 170/79 - Crew Seat Back Cylinder Lock Modification","slug":"ad-cessna-170-79-crew-seat-back-cylinder-lock-modification","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":64122,"registerId":"commonwealth-F2007L00641-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"Cessna 170, 172, F172, FR172 and 175 Ser","sectionType":"division","heading":"Cessna 170, 172, F172, FR172 and 175 Series Aeroplanes","content":"### Cessna 170, 172, F172, FR172 and 175 Series Aeroplanes\n\n| AD/CESSNA 170/79 | Crew Seat Back Cylinder Lock Modification | 5/2007 DM |\n| ---------------- | ----------------------------------------- | --------- |\n\n| Applicability: | Cessna 172R (Serial Numbers 17280001 through 17281262) and Cessna 172S (Serial Numbers 172S8001 through 172S9994).                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                   |\n| -------------- | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |\n| Requirement:   | 1) Aeroplanes that do not have Modification Kit MK172-25-10A or Modification Kit MK172-25-10B installed, for each crew seat (pilot and copilot), install Modification Kit MK172-25-10C or fabricate and install a steel lock rod/bar. Follow Cessna Single Engine Service Bulletin SB04-25-01, Revision 4, dated December 26, 2006, for installing Modification Kit MK172-25-l0C, or, follow Cessna Single Engine Service Bulletin SB04-25-02, Revision 1, dated October 17, 2005, or Revision 2, dated June 5, 2006, for fabricating and installing a steel lock rod/bar.2) Aeroplanes that have Modification Kit MK172-25-10A or Modification Kit MK172-25-10B installed:(i) For each crew seat (pilot and co-pilot), perform an installation inspection in accordance with Cessna Single Engine Service Bulletin SB04-25-01, Revision 4, dated 26 December 2006.(ii) If you do not find any discrepancies during the inspection required in paragraph (2)(i) of this AD, make a log book entry showing compliance with this AD and no further action is required.(iii) If you find discrepancies during the inspection required in paragraph (2)(i) of this AD, make all necessary corrective actions in accordance with Cessna Single Engine Service Bulletin SB04-25-01, Revision 4, dated 26 December 2006.Note: FAA AD 2007-05-10 Amdt 39-14971 and Cessna Service Bulletins SB04-25-01 and SB04-25-02 refer. |\n| Compliance:    | 1) For aeroplanes over 1,000 hours time-in-service (TIS) on the effective date of this AD, perform the action within the next 4 months after the effective date of this AD; orFor aeroplanes from 501 to 1,000 hours TIS on the effective date of this AD, perform the action within the next 8 months after the effective date of this AD; or                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                       |\n\n|             | For aeroplanes from 0 to 500 hours TIS on the effective date of this AD, perform the action within the next 12 months after the effective date of this AD.2) For aeroplanes meeting Requirement 2:(i) Within the next 30 days after the effective date of this AD.(ii) Before further flight after the inspection required in paragraph 2(i) of this AD.(iii) Before further flight after the inspection required in paragraph 2(i) of this AD.                                                                                                                                                                                                                                       |\n| ----------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |\n|             | This Airworthiness Directive becomes effective on 11 April 2007.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      |\n| Background: | This AD results from reports of the crew seat back cylinder lock assembly failing at the aft end area and other cylinder lock assemblies found cracked. The actions specified in this AD are intended to prevent the crew seat cylinder lock assembly from bending, cracking, or failing. This failure could cause uncontrolled movement of the seat back, resulting in possible backward collapse during flight. Backward collapse of either crew seat back could result in an abrupt pitch-up if the affected crew member continues to hold on to the control yoke during this failure and could cause difficulty in exiting the airplane from an aft passenger seat after landing. |\n\n![](image.001.png)  \nDavid Villiers  \nDelegate of the Civil Aviation Safety Authority\n\n9 March 2007","sortOrder":0},{"sectionNumber":"AD/CESSNA 170/79","sectionType":"part","heading":"AD/CESSNA 170/79","content":"## AD/CESSNA 170/79","sortOrder":1},{"sectionNumber":"Crew Seat Back Cylinder Lock Modificatio","sectionType":"part","heading":"Crew Seat Back Cylinder Lock Modification","content":"## Crew Seat Back Cylinder Lock Modification","sortOrder":2},{"sectionNumber":"5/2007 DM","sectionType":"part","heading":"5/2007 DM","content":"## 5/2007 DM","sortOrder":3}],"analysis":{"kimi_summary":{"content_quality":"ok","complexity_score":3,"scope_assessment":{"changed":false,"description":"This AD maintains its original narrow scope — addressing a specific mechanical defect in specific Cessna aircraft models. The tiered compliance schedule and dual-path requirements (new installation vs. inspection of existing modification) are standard aviation safety regulatory techniques for managing fleet-wide retrofits without expanding beyond the original safety purpose."},"complexity_factors":["Multiple conditional pathways based on existing modification status (Requirement 1 vs Requirement 2)","Nested sub-paragraphs (2)(i), (2)(ii), (2)(iii) with different compliance timelines","Cross-references to external Cessna Service Bulletins (SB04-25-01 Rev 4, SB04-25-02 Rev 1 and Rev 2)","Time-in-service (TIS) tiered compliance schedule (three brackets: 0-500, 501-1000, 1000+ hours)","Specific serial number applicability ranges requiring verification","Reference to FAA AD 2007-05-10 for additional context"],"plain_english_summary":"This is an **Airworthiness Directive (AD)** — a mandatory safety order issued by Australia's Civil Aviation Safety Authority (CASA). It requires owners and operators of specific Cessna aeroplanes to fix a dangerous defect in the pilot and co-pilot seats.\n\n**The problem:** The seat back cylinder lock assembly (the mechanism that holds your seat upright) can crack or fail. If this happens during flight, the seat could suddenly collapse backward. This is dangerous because:\n- If the pilot is holding the control yoke when the seat collapses, it could cause a sudden pitch-up (the nose of the plane goes up sharply)\n- It could also block the exit path for passengers trying to leave the plane after landing\n\n**Who must comply:** Owners of specific Cessna 172R and 172S model aeroplanes with particular serial numbers (roughly those manufactured between 1996 and 2006).\n\n**What must be done:**\n- **If your plane doesn't have a previous fix installed:** Install a new modification kit (MK172-25-10C) or fabricate and install a steel lock rod/bar following Cessna's official instructions\n- **If your plane already has an earlier fix (MK172-25-10A or B):** Inspect the installation within 30 days. If it's fine, log it and you're done. If there are problems, fix them before flying again\n\n**When it must be done:** The deadline depends on how many hours the plane has flown:\n- Over 1,000 hours: within 4 months\n- 501–1,000 hours: within 8 months  \n- 0–500 hours: within 12 months\n\n**Why it matters:** This is a life-safety issue. A pilot's seat collapsing during takeoff, landing, or turbulence could cause loss of control of the aircraft."},"flash_summary":{"complexity_score":4,"scope_assessment":{"changed":false,"description":"The AD is narrowly focused on a single mechanical failure mode (crew seat back cylinder lock assemblies) for specific Cessna 172R and 172S serial ranges. The requirements stick to inspection, corrective action or installation/fabrication remedies tied to the manufacturer’s service bulletins. There is no indication in the text that the AD expanded beyond that original safety purpose; it remains limited to preventing the identified cracking/failure and its operational consequences."},"complexity_factors":["Two distinct compliance pathways: install new kit MK172-25-10C or fabricate/install a steel lock rod/bar (Requirement 1)","Separate pathway for aeroplanes with older kits MK172-25-10A/B requiring inspection and conditional corrective action (Requirement 2)","Multiple referenced documents and revisions: Cessna SB04-25-01 Rev 4, SB04-25-02 Rev 1 and Rev 2, and FAA AD 2007-05-10","Three time-in-service (TIS) compliance windows (0–500, 501–1,000, >1,000 hours) plus an urgent 30-day inspection window for aircraft with older kits","Serial-number limited applicability (specific 172R and 172S serial ranges)","Conditional outcomes (no further action if inspection finds no discrepancy; mandatory corrective work if discrepancies are found)"],"plain_english_summary":"**What this rule does (mechanically)\n\n- Applies to: Cessna 172R (serials 17280001–17281262) and Cessna 172S (serials 172S8001–172S9994).\n\n- Required actions:\n  - If your aeroplane does NOT already have Modification Kit MK172-25-10A or MK172-25-10B installed: for both pilot and co‑pilot seats you must either install Modification Kit MK172-25-10C or fabricate and install a steel lock rod/bar. The work must follow the procedures in Cessna Single Engine Service Bulletin SB04-25-01 (for kit MK172-25-10C) or SB04-25-02 (for a fabricated steel rod/bar). (Requirement 1)\n  - If your aeroplane DOES already have MK172-25-10A or MK172-25-10B installed: you must inspect each crew seat installation following SB04-25-01 (Revision 4). If the inspection finds no discrepancies, log the compliance and do nothing more. If it does find discrepancies, you must carry out the corrective actions specified in SB04-25-01. (Requirement 2)\n\n- Timing (compliance windows):\n  - Aeroplanes with >1,000 hours total time-in-service (TIS) on the AD effective date: complete the required action within 4 months.\n  - Aeroplanes with 501–1,000 hours TIS: within 8 months.\n  - Aeroplanes with 0–500 hours TIS: within 12 months.\n  - For aeroplanes that already have the older kits (Requirement 2): the inspection must be done within 30 days of the AD taking effect, and any required corrective action must be done before further flight. (Compliance)\n\n- Why the rule exists (stated rationale):\n  - There were reports of the crew seat back cylinder lock assembly failing or cracking at the aft end. The directive aims to prevent bending, cracking or failure of the cylinder lock assembly. If a lock fails, a seat back could move uncontrolled and collapse rearwards, which could cause a sudden pitch‑up if the occupant holds the yoke, and could impede egress from an aft passenger seat after landing. (Background)\n\nPractical implications, costs and decision flow\n\n- Who pays: aircraft owners/operators pay for the kit, parts or labour to fabricate/install the steel rod, or for inspection and any corrective work.\n\n- Who decides what to do: an appropriately approved maintenance organisation or certificated mechanic must perform the installation, fabrication or inspection in accordance with the referenced Cessna service bulletins. The operator chooses between installing the MK172‑25‑10C kit or fabricating the steel rod/bar, subject to the service bulletin instructions. (Requirement 1)\n\n- Behaviour change required: affected operators must either upgrade/install the new kit or install a fabricated steel lock, or inspect and fix existing older kits. Operators must also record compliance in the aircraft logbook when inspections show no discrepancy. (Requirement 2)\n\n- Options and substitution effects: the AD permits two technical routes — install the manufacturer’s MK172‑25‑10C kit or fabricate and install a steel lock rod/bar following Cessna SB instructions. That gives operators a choice between buying a kit or performing approved fabrication; that can shift costs between parts and labour and may affect time out of service.\n\nCosts, incentives and trade‑offs\n\n- Concentrated benefits: Owners/operators who install the fix reduce the risk of seat collapse and its safety consequences. The benefit is concentrated to those aircraft and their occupants.\n\n- Diffuse costs: The financial and time cost of inspection/fabrication/installation is borne by individual owners/operators. There is no new direct government funding in the AD text.\n\n- Opportunity cost and downtime: aircraft will be out of service for the time taken to perform inspections, fabrication or kit installation. Operators must weigh this downtime and cost against the safety benefit and regulatory requirement.\n\nImplementation risk and compliance burden\n\n- Implementation risk: work must be performed exactly to the referenced service bulletins. Incorrect fabrication or improper installation risks non‑compliance or continued safety exposure.\n\n- Compliance burden: the AD sets different deadlines by TIS bands and an urgent 30‑day inspection window for aeroplanes with the earlier kits. Operators must track serial numbers, TIS and maintenance status and ensure logbook entries for compliance.\n\nEffects on private enterprise and competition\n\n- Independent maintenance providers and Cessna‑authorised shops will receive demand for parts, kits and labour. The AD references Cessna service bulletins for procedural guidance; that steers technical work toward the manufacturer’s instructions but does not mandate a single supplier for labour.\n\nConcrete mechanisms of safety improvement and limits\n\n- Mechanism: replacing or reinforcing the aft end of the seat back cylinder lock assembly (either via MK172‑25‑10C or a steel rod/bar) is intended to eliminate the identified crack/bend failure mode that can cause rearwards collapse. The AD reduces the known mechanical failure pathway; it does not address unrelated seat or restraint issues.\n\nNotes on sources and claims\n\n- The directive cites FAA AD 2007‑05‑10 and the relevant Cessna service bulletins as the technical references for inspection, fabrication and installation procedures. The safety rationale (preventing seat back collapse and possible pitch‑up or egress difficulty) is the stated reason in the AD.\n\nSummary sentence: This AD requires owners/operators of the listed Cessna 172R/S serials to either install a specified modification kit or fabricate and fit a steel lock rod/bar — or, where older kits exist, to inspect and correct them — within set timeframes, to address reports of cracked/failed seat back cylinder locks that could permit rearward seat collapse. (Requirements and Compliance sections.)"},"flash_summary_failed":{"failed":true,"reason":"A positive credit balance is required for all requests, including BYOK, so fallback providers remain available. Add credits at https://vercel.com/d?to=%2F%5Bteam%5D%2F%7E%2Fai%3Fmodal%3Dtop-up to continue.","source":"analysis-cron"},"summary":{"content_quality":"ok","complexity_score":3,"scope_assessment":{"changed":false,"description":"This airworthiness directive introduces a new mandatory safety requirement for specific Cessna 172 aircraft. It does not amend or repeal another instrument."},"complexity_factors":["References multiple service bulletins and modification kits","Conditional inspection and modification requirements based on installed equipment","Time-in-service-based compliance schedule"],"plain_english_summary":"Owners and operators of certain Cessna 172R/S aircraft (specific serial-numbered series) must address a risk that the crew seat back lock can bend or fail, allowing seats to collapse and potentially cause a sudden pitch-up or impede rear-seat exit. CASA requires either installing an approved modification or inspecting/correcting existing kits, with compliance paths and timeframes varying by prior modification status and aircraft hours-in-service. Non‑compliance renders the aircraft unairworthy."}},"importantCases":[],"_links":{"self":"/api/acts/ad-cessna-170-79-crew-seat-back-cylinder-lock-modification","history":"/api/acts/ad-cessna-170-79-crew-seat-back-cylinder-lock-modification/history","analysis":"/api/acts/ad-cessna-170-79-crew-seat-back-cylinder-lock-modification/analysis","conflicts":"/api/acts/ad-cessna-170-79-crew-seat-back-cylinder-lock-modification/conflicts","importantCases":"/api/acts/ad-cessna-170-79-crew-seat-back-cylinder-lock-modification/important-cases","documents":"/api/acts/ad-cessna-170-79-crew-seat-back-cylinder-lock-modification/documents"}}