{"id":"F2006B11371","name":"AD/MU-2/40 - Placard - Use of Reverse Thrust","slug":"ad-mu-2-40-placard-use-of-reverse-thrust","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":57271,"registerId":"commonwealth-F2006B11371-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/MU-2/40 - Placard - Use of Reverse Thrust","content":"COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 \\- 105 CIVIL AVIATION SAFETY AUTHORITY\n\nSCHEDULE OF AIRWORTHINESS DIRECTIVES\n\n![](image.001.png)  \nMitsubishi MU-2 Series Aeroplanes\n\nAD/MU-2/40 Placard \\- Use of Reverse Thrust 10/87 DM\n\nApplicability: All model MU-2-( ) fitted with Garrett TPE-331 turboprop engines to which Hartzell model HC-B4(T,M)N-5( ) propellers are fitted.\n\nRequirement: Install a temporary placard in a suitable position in the cockpit worded as follows: “Until propellers are modified to Hartzell SB 153, avoid the use of full reverse pitch.”\n\nCompliance: By 30 October 1987.\n\nBackground: During the past several months the four bladed steel hub propeller fitted to MU-2-( ) series a/c has experienced failure of the pitch change rod P/N B-3018S-2. Failure has occurred during ground operation with application of full reverse pitch. Rod failure in this position will cause the propeller to travel deeper into reverse which could cause severe asymmetric thrust conditions or unacceptable engine overtemperature conditions.","sortOrder":0}],"analysis":{"flash_summary":{"complexity_score":2,"scope_assessment":{"changed":false,"description":"The directive's scope aligns with its stated safety intent in the Background: to mitigate pitch change rod failures that occurred during ground operation with full reverse pitch. It imposes a targeted, temporary operational restriction for the same subset of aircraft described in Applicability and ties restoration of the prior capability to a specific propeller modification (Hartzell SB 153). There is no indication in the text that the scope was expanded or narrowed from that stated purpose."},"complexity_factors":["Narrow and specific applicability (models, engine type, propeller model) (Applicability)","Single, simple required action (install a temporary placard with exact wording) (Requirement)","Clear compliance deadline (30 October 1987) (Compliance)","Technical background ties operational restriction to a specific hardware failure and a specified modification as the remedy (Background; Requirement)","Some operational discretion remains (\"suitable position\" for placard) which slightly increases minor interpretive complexity (Requirement)"],"plain_english_summary":"Requires operators of MU-2 models fitted with Garrett TPE‑331 engines and Hartzell HC‑B4(T,M)N‑5( ) propellers to install a temporary cockpit placard stating “Until propellers are modified to Hartzell SB 153, avoid the use of full reverse pitch.” Owners/operators or their maintenance agents must fit the placard by 30 October 1987. The action responds to pitch‑change rod failures during ground full‑reverse that can cause severe asymmetric thrust or engine overtemperature; the placard is a short‑term mitigation until the SB 153 modification."},"kimi_summary":{"content_quality":"ok","complexity_score":2,"scope_assessment":{"changed":false,"description":"This is a discrete, time-bound safety directive addressing a specific mechanical failure mode. It has not expanded beyond its original purpose of mitigating propeller pitch change rod failures through interim cockpit warnings."},"complexity_factors":["Single, specific applicability clause targeting one aircraft series with defined engine/propeller combinations","One straightforward requirement: install a placard with exact wording provided","Single compliance date with no conditional extensions or exceptions","No defined terms section, no cross-references to other legislation beyond the enabling regulations (CAR 1998 Part 39)","Background provided in plain narrative form rather than technical legalese","Document length: approximately 200 words"],"plain_english_summary":"This is an **Airworthiness Directive** — essentially a mandatory safety order issued by Australia's aviation safety regulator (CASA) for a specific type of aircraft.\n\n**What it does:**\n- Requires owners and operators of **Mitsubishi MU-2 aeroplanes** (fitted with specific Garrett engines and Hartzell propellers) to **install a warning placard** in the cockpit.\n- The placard must warn pilots: *\"Until propellers are modified to Hartzell SB 153, avoid the use of full reverse pitch.\"*\n\n**Why it matters:**\n- The propeller's **pitch change rod** (a component that adjusts blade angle) has been failing when pilots use **full reverse thrust** on the ground.\n- If this rod breaks, the propeller can swing into deeper reverse, creating two serious dangers:\n  - **Asymmetric thrust** — one engine producing much more reverse power than the other, making the aircraft hard to control\n  - **Engine overtemperature** — the engine overheating dangerously\n\n**Who it affects:**\n- Operators of Mitsubishi MU-2 aircraft with the specific engine/propeller combination listed\n- Compliance was required by **30 October 1987**\n\n**The fix:**\n- **Temporary:** Install the warning placard immediately\n- **Permanent:** Eventually modify the propellers per Hartzell Service Bulletin 153 (though this directive only mandates the placard)"}},"importantCases":[],"_links":{"self":"/api/acts/ad-mu-2-40-placard-use-of-reverse-thrust","history":"/api/acts/ad-mu-2-40-placard-use-of-reverse-thrust/history","analysis":"/api/acts/ad-mu-2-40-placard-use-of-reverse-thrust/analysis","conflicts":"/api/acts/ad-mu-2-40-placard-use-of-reverse-thrust/conflicts","importantCases":"/api/acts/ad-mu-2-40-placard-use-of-reverse-thrust/important-cases","documents":"/api/acts/ad-mu-2-40-placard-use-of-reverse-thrust/documents"}}