Bulletin 54-088 -

Alternatively, it could be a product bulletin from a manufacturer. The first part "54" might refer to a product line, and "088" as a specific model or revision. If that's the case, the solid feature might be a design improvement or a new feature introduced in version 088 of the product.

with Airworthiness Directive (AD) 88-21-03. In the aviation industry, Service Bulletins are issued by manufacturers to address specific maintenance or safety issues discovered during the service life of an aircraft. When an issue is severe enough to affect flight safety, the Federal Aviation Administration (FAA) may issue an Airworthiness Directive, making the bulletin’s recommended actions mandatory for all operators of that aircraft type. Regulations.gov Technical Implementation The primary technical focus of Bulletin 54-088 is the fuel crossfeed system bulletin 54-088