FAA AC 20-140 PDF

This AC provides guidelines for design approval of aircraft systems that provide the data communications function and applications on the aircraft. The data communications function and applications on the aircraft communicate digital data with the ground computer systems managed by air traffic, a service provider, or an aircraft operator. Digital data are exchanged between the aircraft and the ground systems and are used to display or print information to the flightcrew or controller or directly interface with other computer applications, such as flight planning and navigation, on the aircraft and surveillance on the ground. The aircraft systems that provide this capability will be referred to throughout this AC as aircraft data communications systems and applications. This AC considers the following:

Evolutionary development.

The guidelines contained in this AC are applicable to all aircraft data communications systems and applications, even those that may not be compatible with the ICAO aeronautical telecommunication network (ATN). Therefore, this AC provides for the data communications technology to evolve within the national airspace system (NAS) and international airspace during operational service without compromising safety, while at the same time it provides the flexibility to migrate to ATN-compatible data communications systems.

Data communications applications.

Guidelines provide for the addition and modification of data communications applications and minimize the evaluation of the data communications system. Data communications systems and applications that use protected navigation frequencies, such as for delivery of differential global positioning system (DGPS) information, are beyond the scope of this AC and will be addressed in documents providing guidance for design approval of navigation functions. Examples of data communications applications are controller-pilot data link communications (CPDLC) for pilot-controller communication, automatic dependent surveillance (ADS), pre-departure clearance (PDC), oceanic clearance, automatic terminal information service (ATIS), weather services, ATS facilities notification (AFN) for the ACARS, and context management for ATN.

Data communications system subnetworks.

Guidelines provide for the data communications system to use a variety of air/ground subnetworks, including satellite, very high frequency (VHF) radio, high frequency (HF) radio, Mode S, and gatelink.

Institutional considerations.

Different parts of the data communications system and applications are controlled by different organizations. For example, within the FAA, the Aircraft Certification Service is responsible for design approval, whereas the Flight Standards Service is responsible for operational authorization. In some cases, a foreign civil air authority (FCAA) will be responsible for operational authorization. Other organizations, some non-Federal, are responsible for commissioning the air/ground subnetwork, ground data communications system, and ground applications.

International implications.

The Aircraft Certification Service is coordinating these guidelines for design approval of aircraft data communications systems and applications with FCAA. We intend to harmonize the airworthiness criteria contained within this AC.

NOTE: This AC discusses the operational concepts of data communications applications and the NAS only to describe the relationship of the design approval of aircraft data communications systems and applications with the commissioning of ATS facilities and operational authorizations. This information should not be misinterpreted as guidance for obtaining an operational authorization to use ATS data communications applications or for commissioning ground and space segments of the data communications system and applications. This AC only provides guidance for obtaining design approval of the aircraft data communications system and applications.