Safety Issue

Following this occurrence, the aircraft operator:

• increased the frequency of maintenance to clean and flush the forward galley drain lines to every A-check
• increased the frequency of maintenance to clean behind the ice drawers every A-check • added procedures to remove and clean the forward galley ‘Y’ connector during scheduled maintenance
• changed the maintenance procedures to require the replacement of soft galley drain lines on every D-check
• promulgated cabin crew standing orders to provide guidance on the appropriate methods of disposal for different types of liquids
• initiated a review of toilet design, maintenance, and signage to reduce the frequency and impact of blockages - some changes had already been implemented when this report was drafted
• initiated a project to implement high-pressure waste line cleaning
• is investigating a number of proposals to improve galley operation, including the replacement of coffee grounds with coffee bags and the provision of liquid absorption and disposal products
• initiated a review of its fleet’s aircraft drain systems to improve reliability, eliminate the risk of blockages, review maintenance practices, eliminate safety risks to engineers, and consider future product selection
• issued service bulletins to modify the drain behind the coffee machine and water boiler to ensure that the drain line is now directed into the galley drain port to prevent water spilling over the top of the galley
• promulgated a cabin standing order and a flight standing order to all 747-400 cabin and flight crews, requiring them to identify, treat and report abnormal water accumulation in galley areas, and modified the cabin crew operating manual accordingly
• promulgated a flight standing order to all flight crew, requiring them to treat and report abnormal water accumulation in galley areas and requiring crews to treat substantial water leaks as airworthiness items (which the operator defined as items that have the potential to affect the aircraft’s ability to operate safely if unserviceable).

In response to this occurrence, the aircraft manufacturer changed the drain overflow troubleshooting procedures to improve the identification of blocked drains.