Overview

The Airworthiness Directive AD/B737/234 issued in 2005 by the Civil Aviation Safety Authority (CASA) is a legislative instrument designed to address a safety concern identified in Boeing 737 Series aeroplanes, specifically models 737-600, -700, -700C, -800, and -900. The directive was introduced to rectify an unsafe condition where flammable fluid could leak past unsealed areas and ignite, potentially leading to an uncontrolled fire in the engine struts. The objective of this AD is to ensure the airworthiness of the specified aircraft by mandating a visual inspection of the sealant at the interface of the diagonal brace fitting and the aft bulkhead, as well as the four bolts at this interface. Depending on the inspection results, the directive requires either the application of fillet or cap seal to prevent such leaks. The directive applies to all affected aircraft within a specified timeframe, ensuring compliance with safety standards set forth by CASA.

Scope and Application

The Airworthiness Directive issued under subregulation 39.1 (1) of the Civil Aviation Safety Regulations 1998 applies specifically to the Boeing 737 Series Aeroplanes, namely the 737-600, -700, -700C, -800, and -900 models, within line numbers 1 through 946 inclusive. The directive mandates a general visual inspection for sealant at the interface of the diagonal brace fitting and the aft bulkhead and at the four bolts common to this interface. Depending on the findings of this inspection, further action such as applying fillet seal or cap seal may be required in accordance with the instructions detailed in Boeing Special Attention Service Bulletin 737-54-1039, Revision 1. The directive is applicable nationwide and its purpose is to correct an unsafe condition that could potentially lead to an uncontrollable fire. The compliance timeframes for these requirements are set out in the directive, with the general visual inspection and necessary actions to be completed within 18 months or 3,500 flight cycles from the effective date of the directive, whichever comes first, and specific actions to be taken before further flight if certain conditions are met. This Airworthiness Directive extends its reach across the Commonwealth of Australia, ensuring that all relevant aircraft within the specified models and line numbers adhere to these safety measures.

Key Provisions

This Airworthiness Directive (AD) applies to Boeing 737 series aeroplanes, specifically models 737-600, -700, -700C, -800, and -900, with line numbers ranging from 1 to 946 inclusive (section 1). The directive mandates a general visual inspection of the sealant at the interface of the diagonal brace fitting and the aft bulkhead, as well as at the four bolts common to this interface (section 1(a)). This inspection must be carried out in accordance with the Accomplishment Instructions of Boeing Special Attention Service Bulletin 737-54-1039, Revision 1, dated 10 October 2002 (section 1(a)). Depending on the findings, either no further action is required, or specific measures such as the application of fillet or cap seal must be taken (section 1(b) and 1(c)). The AD imposes several obligations on the parties or entities it governs. Firstly, it requires the performance of a general visual inspection to ascertain the condition of the sealant at the specified interfaces (section 1(a)). If the sealant is continuous or there is evidence of sealant squeeze out, no further action is required (section 1(a)(i) and 1(a)(ii)). If the seal is not continuous and there is no evidence of sealant squeeze out, fillet seal must be applied as per the instructions (section 1(b)). If the bolts do not have evidence of sealant squeeze out and no cap seal exists, the bolts must be capped as per the instructions (section 1(c)). Compliance with these requirements is crucial to ensure the aircraft's airworthiness and safety. Failure to comply with the AD can result in serious consequences. While the AD does not explicitly outline specific offences or penalties, non-compliance with airworthiness directives in general can lead to enforcement actions by the Civil Aviation Safety Authority (CASA). Such actions may include fines, suspension or revocation of aircraft certificates, and potential criminal charges if the non-compliance results in a significant safety risk. The maximum penalties for offences related to airworthiness directives can be substantial, reflecting the importance of adhering to these safety measures.