{"id":"F2006B07599","name":"AD/WHE/4 Amdt 4 - Inflation of Tyres with an Inert Gas","slug":"ad-whe-4-amdt-4-inflation-of-tyres-with-an-inert-gas","collection":"legislative_instrument","jurisdiction":"commonwealth","status":"in_force","isInForce":true,"actNumber":null,"makingDate":null,"administeringDepartment":null,"currentVersion":{"id":50272,"registerId":"commonwealth-F2006B07599-current","compilationNumber":null,"startDate":"2026-04-02","status":"InForce","reasons":null,"registeredAt":null},"sections":[{"sectionNumber":"1","sectionType":"section","heading":"AD/WHE/4 Amdt 4 - Inflation of Tyres with an Inert Gas","content":"COMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 \\- 107 CIVIL AVIATION SAFETY AUTHORITY\n\nSCHEDULE OF AIRWORTHINESS DIRECTIVES\n\n![](image.001.png)  \nWheels and Tyres\n\nAD/WHE/4\n\nAmdt 4\n\n  \nInflation of Tyres with an Inert Gas 9/98\n\nApplicability: All aircraft over 5700 kg MTOW and all those below 5700 kg MTOW fitted with tyres with a rating in excess of 266 km per hour (160 mph), except those tyres installed on aircraft with fixed non-retracting undercarriages.\n\nRequirement: To ensure that all tyres fitted to braked wheels do not contain more than 5% of oxygen by volume, accomplish paragraph 1 or 2 below. Either of these procedures is acceptable, or they may be used together:\n\n    Install a placard, either in each wheel well or on or near each landing gear strut incorporating braked wheels, and in a location so as to be easily seen by a person performing routine tyre servicing. The placard shall state\n\n“ INFLATE TYRES WITH NITROGEN ONLY”; or,\n\n    2. Incorporate into the aircraft maintenance program, procedures that include the following items:\n\n    On braked wheels, install only tyres that have been inflated with dry nitrogen or other gases shown to be inert such that the gas mixture does not exceed 5% oxygen by volume.\n\n    b. Tyres on braked wheels may be serviced with air at remote locations where dry nitrogen is not available, provided that:\n\n    the oxygen content does not exceed 5% by volume; or,\n\n    ii. within the next 15 hours time in service, the tyre must be purged of air and inflated with dry nitrogen so that the oxygen does not exceed 5% by volume.\n\nNote: FAA AD 87-08-09 Amdt 39-5613 refers.\n\nCompliance: This amendment becomes effective on 13 August 1998.\n\nCOMMONWEALTH OF AUSTRALIA (Civil Aviation Regulations 1998), PART 39 \\- 107 CIVIL AVIATION SAFETY AUTHORITY\n\nSCHEDULE OF AIRWORTHINESS DIRECTIVES\n\nBackground: This Directive was issued in response to the catastrophic loss of an airliner and reports of severe damage to others as a result of wheel well tyre explosions. The explosion of the tyres has been attributed to the spontaneous combustion of gases generated within the tyres at elevated tyre temperatures. Inflation of tyres with an inert gas reduces the oxygen content to a level below that at which ignition is sustainable.\n\nAmendment 2 reflected the fact that 120+ mph tyres, though “high speed” may be fitted to some aircraft not intended to be affected by this directive.\n\nAmendment 3 excluded those fixed undercarriage aircraft that have over time been re- certificated at higher weights and now exceed the 5700 kg crossover point.\n\nAmendment 4 is issued to align this directive more closely with the FAA AD that prompted the initial issue of this directive.\n\nAmendment 3 of this airworthiness directive became effective on 6 November 1997. Amendment 2 of this airworthiness directive became effective on 25 February 1988. The original issue of this airworthiness directive became effective on 31 August 1987.","sortOrder":0}],"analysis":{"flash_summary":{"complexity_score":3,"scope_assessment":{"changed":true,"description":"The directive's scope was adjusted across amendments: Amendment 2 clarified that high-speed (120+ mph / >266 km/h) tyres can appear on aircraft not otherwise intended to be covered; Amendment 3 excluded tyres on fixed non‑retracting undercarriage that later exceeded the 5,700 kg crossover due to re‑certification; Amendment 4 aligned the directive more closely with the FAA AD that prompted the original issue. These changes refined which aircraft and tyres are captured."},"complexity_factors":["Dual applicability thresholds: MTOW (>5,700 kg) and tyre speed rating (>266 km/h) create a mixed population of affected aircraft","Specific exception for tyres on fixed non‑retracting undercarriage narrows scope and requires fleet-by-fleet assessment","Two alternative compliance routes (placard OR maintenance-program procedures) allow flexibility but require policy choice","Technical compliance metric (oxygen ≤5% by volume) requires measurement, monitoring and record-keeping","Temporary allowance to service with air at remote locations subject to a 15 flight‑hour purge creates a tracking burden","Alignment with a corresponding FAA AD introduces cross-jurisdictional consistency and possible external reference reliance","Multiple historical amendments indicate evolving scope and potential interpretive uncertainty for legacy certifications"],"plain_english_summary":"This directive requires tyres on braked wheels of affected aircraft to contain no more than 5% oxygen by volume. Operators may comply by fitting \"INFLATE TYRES WITH NITROGEN ONLY\" placards or by adopting maintenance procedures to use dry nitrogen (or an inert equivalent) and to purge air within 15 flight hours if tyres are temporarily serviced with air.\n\nIt applies to aircraft over 5,700 kg MTOW and to lighter aircraft with tyres rated above 266 km/h, excluding fixed non‑retracting undercarriage. Operators pay servicing and monitoring costs; the regulator enforces compliance."},"kimi_summary":{"content_quality":"ok","complexity_score":3,"scope_assessment":{"changed":true,"description":"The original directive applied broadly to aircraft over 5700 kg. Amendment 2 added the speed rating criterion (266 km/h) to catch smaller fast aircraft. Amendment 3 carved out an exception for fixed undercarriage aircraft that had been re-certificated at higher weights. Amendment 4 aligns the rule with the US FAA directive. The scope has been refined through multiple amendments to be more precise about which aircraft are truly at risk, rather than expanding beyond the original safety purpose."},"complexity_factors":["Simple conditional applicability (weight threshold of 5700 kg and speed rating of 266 km/h with two exceptions)","Only two compliance options (placard or maintenance program) with minimal sub-conditions","Single quantitative threshold (5% oxygen by volume) repeated throughout","Limited cross-referencing (one FAA AD mentioned in background only)","Short document (approximately 400 words)","Clear structure: Applicability → Requirement → Compliance → Background"],"plain_english_summary":"This is a safety rule for aircraft tyres. It requires that tyres on braked wheels of larger aircraft (over 5,700 kg) and faster smaller aircraft (tyres rated above 160 mph) must be inflated with nitrogen or another inert gas, keeping oxygen content below 5%. This prevents tyre explosions caused by heat igniting oxygen inside the tyre.\n\n**Who it affects:** Airlines, aircraft maintenance crews, and operators of affected aircraft.\n\n**What they must do:** Either put up warning signs saying \"INFLATE TYRES WITH NITROGEN ONLY\" near the wheels, or update maintenance procedures to ensure only nitrogen-inflated tyres are used. If stuck at a remote airport without nitrogen, crews can use regular air temporarily, but must purge and refill with nitrogen within 15 flight hours.\n\n**Why it matters:** This rule prevents catastrophic wheel well fires and explosions that have destroyed aircraft in the past."},"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"}},"importantCases":[],"_links":{"self":"/api/acts/ad-whe-4-amdt-4-inflation-of-tyres-with-an-inert-gas","history":"/api/acts/ad-whe-4-amdt-4-inflation-of-tyres-with-an-inert-gas/history","analysis":"/api/acts/ad-whe-4-amdt-4-inflation-of-tyres-with-an-inert-gas/analysis","conflicts":"/api/acts/ad-whe-4-amdt-4-inflation-of-tyres-with-an-inert-gas/conflicts","importantCases":"/api/acts/ad-whe-4-amdt-4-inflation-of-tyres-with-an-inert-gas/important-cases","documents":"/api/acts/ad-whe-4-amdt-4-inflation-of-tyres-with-an-inert-gas/documents"}}