Introduction: This document is intended to provide design guidance for the development and installation of an Expandable Flight Data Acquisition and Recording System primarily intended for airline use. As such, this guidance will include specific requirements necessary to provide functional capability to accommodate expanded flight data recording plus those requirements needed to insure interchangeability of equipment in "standard" aircraft installations. See Attachments 3-1 and 3-2 for a simplified schematic of standard interwiring and system block diagram.