Controller-pilot communications using a VDL Mode 2 datalink for the NASA runway incursion prevention system

NASA's Runway Incursion Prevention System (RIPS) was tested between September and October 2000 at the Dallas Fort-Worth International Airport (DFW). Controller-Pilot Datalink Communications (CPDLC) represented one component of the RIPS program. Air traffic controllers relayed surface operations instructions to NASA's 757 research aircraft via a Controller Communications and Situational Awareness Terminal (C-CAST). The Onyx mainframe computer aboard the 757 decoded these messages and sent automatic acknowledgements back to the C-CAST. The CPDLC messages were sent over a datalink utilizing the ICAO-defined VHF Digital Link (VDL) Mode 2 protocol. This paper presents implementation and performance details of the datalink. The paper describes the VDL Mode 2 protocol, the overall architecture of the CPDLC system, hardware-software interfacing details, CPDLC message formats, signal coverage data for the DFW airport, and design details of the Airborne Datalink Manager (ADLM) software used for this work.