{"id":"F2006B06364","name":"AD/PT6A/27 - Compressor Bleed Off Valve","slug":"ad-pt6a-27-compressor-bleed-off-valve","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"repealed","isInForce":false,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":47608,"registerId":"commonwealth-F2006B06364-current","compilationNumber":null,"startDate":"2026-04-02","status":"Repealed","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/PT6A/27 - Compressor Bleed Off Valve","content":"COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 \\- 106 CIVIL AVIATION SAFETY AUTHORITY\n\nSCHEDULE OF AIRWORTHINESS DIRECTIVES\n\n![](image.001.png)  \nPratt and Whitney Canada Turbine Engines \\- PT6A Series\n\nAD/PT6A/27 Compressor Bleed Off Valve 4/97\n\nApplicability: All Pratt and Whitney Canada (PWC) PT6A engines as detailed by serial number in the following PWC Service Bulletins (SB): SB 1538 Rev.3; SB 3344 Rev.1; SB 4204; SB 12134 Rev.1; SB13287 Rev.1; SB 14251 Rev.1.\n\nRequirement: To prevent the possible malfunction of the compressor bleed off valve resulting in a reduction of required engine power or an engine surge event:\n\n    Inspect the bleed off valve to determine the supplier code. If the supplier code is “8070”, inspect the bleed off valve in accordance with PWC SB 1538 Rev. 3; SB 3344 Rev.1; SB 4204; SB 12134 Rev.1; SB 13287 Rev.1 or SB 14251 Rev.1 as applicable by engine model.\n\n    2. If the supplier code is not “8070” or the bleed off valve has been re-identified to “RE71”, no further action is required.\n\nNote: Transport Canada Airworthiness Directive CF-96-24 refers.\n\nCompliance: Effective 27 March 1997: Unless previously accomplished; within 100 hours time in service or prior to 30 May 1997, whichever occurs first.\n\nBackground: This directive has been issued to require certain compressor bleed off valves to be inspected. The requirement follows advice of movement in the valve guide shaft pin can result in fracture of the cotter pin and possible jamming of the valve. Failure of the valve may result in the loss of required engine power or an engine surge.","sortOrder":0}],"analysis":{"kimi_summary":{"_metrics":{"model":"kimi-k2.5","source":"moonshot-batch","completionTokens":1630},"content_quality":"ok","complexity_score":3,"scope_assessment":{"changed":false,"description":"The directive maintains a narrow, targeted scope focused solely on inspecting specific compressor bleed off valves for a known manufacturing defect. It has not expanded beyond its original purpose of preventing valve jamming and potential engine power loss."},"complexity_factors":["References to six different service bulletins for determining applicability and inspection procedures","Conditional logic requiring identification of specific supplier codes ('8070' vs 'RE71') to determine required action","Serial-number-specific applicability requiring operators to cross-reference their engine against manufacturer documentation"],"plain_english_summary":"This AD requires owners/operators of Pratt & Whitney Canada PT6A engines identified by serial number in six service bulletins to inspect the compressor bleed-off valve supplier code and, if stamped \"8070\", perform the bulletin inspection procedure; valves stamped other codes or changed to \"RE71\" need no further action. It addresses a manufacturing defect that can jam the valve and cause engine power loss or surge. Compliance by 30 May 1997 (or within 100 flight hours after 27 Mar 1997)."}},"importantCases":[],"_links":{"self":"/api/acts/ad-pt6a-27-compressor-bleed-off-valve","history":"/api/acts/ad-pt6a-27-compressor-bleed-off-valve/history","analysis":"/api/acts/ad-pt6a-27-compressor-bleed-off-valve/analysis","conflicts":"/api/acts/ad-pt6a-27-compressor-bleed-off-valve/conflicts","importantCases":"/api/acts/ad-pt6a-27-compressor-bleed-off-valve/important-cases","documents":"/api/acts/ad-pt6a-27-compressor-bleed-off-valve/documents"}}