Advisory 

Circular

U.S. Department 

of Transportation 

Federal Aviation 

Administration

Subject: SAFETY AND INTEROPERABILITY Date: 8/31/05 AC No: 20-149 

REQUIREMENTS FOR INITIAL DOMESTIC Initiated by: AIR-130 Change: 

FLIGHT INFORMATION SERVICE-BROADCAST 

1. PURPOSE. 

 a. This advisory circular (AC) supports the introduction and use of Flight Information 

Service-Broadcast (FIS-B) weather and other aeronautical data link products for enhanced 

situational awareness. It identifies safety and interoperability requirements for continued 

airworthiness of aircraft FIS-B equipment, systems, and applications. Like all advisory material, 

this AC offers one way, but it is not the only way, to comply with regulations. 

 b. We have written this AC for manufacturers and installers of FIS-B equipment and 

software, FIS providers, applicants for FAA design approval of FIS-B systems, and FAA aircraft 

certification office (ACO) staff who assess FIS-B systems. We’ve included a comment form in 

appendix 3 that you can use to give us feedback. 

2. USING AC 20-140 WITH THIS AC. We expect you to use this AC with AC 20-140, 

Guidelines for Design Approval of Aircraft Data Link Communications Equipment. AC 20-140 

describes a standardized way to identify the data communications equipment operational 

environment, execute an operational hazard assessment, and allocate resulting safety and 

interoperability requirements for installing FIS-B equipment. Appendix 1 lists sections from

Title 14 of the Code of Federal Regulations (14 CFR) parts 23, 25, 27, and 29 that you should 

consider when determining the certification basis for approving aircraft data communications 

systems and applications. 

3. WHAT THIS AC WILL COVER. Portable display systems that do not require design 

approval are outside the scope of this AC (see AC 120-76, Guidelines for the Certification, 

Airworthiness, and Operational Approval of Electronic Flight Bag Computing Devices). We do, 

however, cover the following: 

 a. Weather and Aeronautical Information Sources. FIS weather and aeronautical information 

is gathered by several sources using direct observation and instrumented sensors. Approved 

aviation weather information-gathering sources include: 
AC 20-149 8/31/05 

The National Weather Service (NWS), 

• Sources approved by the NWS, 

• Sources authorized by FAA orders. 

• NEXRAD products from national NEXRAD Information Distribution System (NIDS) 

vendors. 

• NOTAMs and NAS status information. 

 b. FIS Providers. FIS providers are responsible for gathering weather and NAS status 

information from sources appropriate for the services they intend to provide. FIS providers then 

process this information into a format suitable for data link. This formatted information is then 

encoded for distribution to their communication subnetwork. The guidance in this AC applies to 

any of the following: 

• FIS services provided by the FAA. 

• FIS providers operating under contract with the FAA using aeronautical spectrum.

• Non-FAA FIS providers operating under customer contract using aeronautical 

spectrum.

• Non-FAA FIS providers operating under customer contract using other than 

aeronautical spectrum. 

 c. Communication Subnetworks. This AC allows the FIS-B system to use a variety of air-, 

ground-, and space-based communication subnetworks. 

 d. Aircraft Environment. The aircraft FIS-B system communicates with ground end-systems 

managed by a service provider. Depending on the FIS service in question, the aircraft’s FIS-B 

equipment will monitor the appropriate subnetwork for broadcast FIS services. The aircraft’s 

FIS-B systems are responsible for the control, display and alerting of FIS products in the cockpit. 

Aircraft systems with this capability are hereafter referred to as FIS-B systems. 

 e. Relationship to AC 20-140. This AC supplements AC 20-140 by describing FIS services, 

establishing safety assessment considerations for FIS-B equipment installation, and identifying 

the allocated safety and interoperability requirements (see paragraph 6). Implementation of 

request-reply FIS service and FIS services obtained from onboard Internet access systems are 

specifically not covered here. Applicants proposing request-reply FIS equipment installation 

will have to assess the safety and interoperability requirements as part of an airworthiness review 

under AC 20-140. 

 f. Safety Assessment Considerations. This AC describes the operational context as part of the 

safety assessment considerations. We will justify hardware and software design assurance 

2
8/31/05 AC 20-149 

minimums and specify safety requirements. For the FIS-B services and products specified in this 

AC, FIS-B information is limited to strategic operations only.

4. OVERVIEW OF THE FIS-B SYSTEM. 

Figure 1: Overview of the FIS-B System. 

Weather and NAS status

Information

Source

Aircraft

Environment

FIS

Provider

Communication

Subnetwork

3a

2a

Satellite

Service Provider

Observation

Sensor

Other Sources

Satellite 

1a

General FIS Information Flow Description. Figure 1 represents a one-way, non-addressed, 

broadcast FIS service that uses either ground- or space-based data link systems. It represents the 

scope and applicability of this AC. Broadcast FIS data flows only from the service provider to 

the receiving aircraft. The aircraft doesn’t need to ask for the information, nor acknowledge it. 

Additionally, information from the service provider is not addressed to any specific aircraft. It’s 

intended for the benefit of all suitably equipped aircraft within the coverage volume. As this 

example shows, the FIS service provider assimilates weather and other information gathered 

from observations, weather sensors, instruments, and other data sources (1a). Once formatted 

and processed, the service provider encodes and distributes that information to the broadcast 

communication subnetwork of choice (2a), where the FIS-B service is sent to the aircraft and 

displayed in cockpits of properly equipped aircraft (3a). 

5. SAFETY ASSESSMENT CONSIDERATIONS. Appendix 2 is the functional hazard 

assessment used to establish FIS-B safety requirements. We expect that technical advances and 

future use of FIS-B may change the operational environment--for example, FIS-B products may 

be adopted as a real-time tactical tool for navigation through severe weather. Such changes will 

affect the safety assessment considerations and resultant hardware/software design assurance 

minimums in this AC. If you are applying for design approval, verify that the FIS-B operational 

3 
AC 20-149 8/31/05 

assumptions in appendix 2 are correct. If the assumptions reflect the operational environment 

(that is, FIS-B is used for flight planning purposes only), then conduct a system safety 

assessment to verify that the likelihood of encountering FIS-B equipment failure conditions is no

greater than ‘probable.’ If the FIS-B operational hazard assessment assumptions in appendix 2 

are not correct, then conduct an operational hazard assessment defined in AC 20-140 to 

determine the FIS-B airborne functional hazard classification. AC 20-140 offers guidelines for 

conducting FIS-B safety assessments for design approval. 

 a. Operational Context. FIS-B systems are not meant to replace voice radio services. Voice 

communication of weather and other information, under the operating rules, is required. Loss or 

non-receipt of FIS-B products is not essential for flight operations. Operators use FIS-B 

products to supplement or complement existing sources of weather and operational information 

only. These existing sources are, for example, Flight Service Station voice networks, Air Traffic 

Control (ATC) facilities, the corporate/airline dispatcher networks, or all three. The safety 

assessment is based on the following assumptions: 

 (1) Loss of FIS -B Function. Loss of FIS-B is a minor failure condition. FIS-B 

supplements existing requirements for voice communication capability and does not replace 

ATC, Flight Service Station (FSS), and, if applicable, Airline Operations Control Center 

(AOCC) voice communications for aeronautical weather, special use airspace, NOTAM, or other 

operational information sent to aircraft in-flight. 

 (2) Effects of Undetected Errors. The effects of undetected errors -- messages received out 

of sequence, errors in message address, weather severity, displayed errors in weather and 

NOTAM location (offset) errors, and errors in the data compression technique-- in FIS-B 

products are a minor failure condition. FIS-B is limited to the operational context of paragraph 

5(a), above. These failures are directly mitigated by operational and procedural constraints in the 

safety requirements (Airplane/Rotorcraft Flight Manual (A/RFM) Section 3 in paragraph 6(a)(3), 

below. 

 (3) Human/Machine Interface. The loss, corruption (or both) of FIS-B information 

intended for display to the pilot or flight crew during normal flight operations introduces a 

marginal increase in pilot workload. At a minimum, we determined that this increase in pilot 

workload contributes to a minor failure condition classification.

 b. Aircraft Integration Aspects. Consult AC 20-140, paragraph 7(e), to determine the impact 

to the safety assessment on integrating the FIS-B system into the aircraft’s existing avionics 

suite. Integration of FIS-B functionality should not compromise shared aircraft resource 

performance. 

 c. Post Certification Design Changes to Airborne FIS-B Equipment. We expect that FIS 

provider textual and graphical product additions, enhancements, or both may promote aircraft 

FIS-B equipment changes. Such changes will most likely affect FIS-B equipment software. We

strongly encourage airborne equipment manufacturers to review AC 20-140, paragraph 6(e)(5)(f) 

to ensure that changes cause no deleterious effects to system safety. Further, we encourage 

applicants to consult their local geographic ACO for guidance on approval of airborne systems 

and equipment with user-modifiable software. Applicants intending to install aircraft FIS 

4
8/31/05 AC 20-149 

systems based upon field approval substantiated by an STC on another make / model aircraft, 

should consult the local flight service district office for current policy guidance before 

installation.

6. ALLOCATED SAFETY AND INTEROPERABILITY REQUIREMENTS. Applicants 

should identify the allocated safety and interoperability requirements in AC 20-140, paragraph 

6(e)(3). If you are an applicant and decide to use this AC to satisfy the objectives of AC 20-140, 

then the following safety and interoperability requirements apply: 

a. Aircraft Requirements. 

(1) At a minimum, develop FIS-B systems and equipment to a hardware and software 

design assurance level commensurate with a minor failure condition. 

(2) The following A/RFM or A/RFM supplement wording applies to FIS-B installations 

covered by this AC. 

(a) Operating Limitations. No wording proposed. 

(b) Operating Procedures. The A/RFM, Section 3, Normal Operating Procedures, 

should state the following: 

Use FIS-B information as a strategic planning tool for pilot decisions on 

avoiding inclement weather areas beyond visual range or where poor 

visibility precludes visual acquisition of inclement weather. Use FIS-B 

weather and NAS status information as follows: 

 a. To aid pilot situational awareness of hazardous meteorological 

conditions and awareness of the regulatory status of the airspace. 

 b. To cue the pilot to communicate with the ATC controller, AFSS 

specialist, operator dispatch, or AOCC for more information about the 

current meteorological conditions or regulatory airspace status.

In no case should the pilot take any evasive action based solely on the 

information on a FIS-B display. FIS-B information is meant to aid strategic 

flight planning only. It lacks sufficient resolution and updating necessary for 

tactical maneuvering. 

The FAA has approved the FIS-B system and applications to the criteria in 

AC 20-140, dated August 16, 1999. This approval was based on the safety 

and interoperability requirements in AC 20-149, dated September 30, 2004. 

This design approval is not an operational authorization. 

 (3) Aircraft FIS-B equipment should meet the interoperability requirements in 

RTCA/DO-267A, Minimum Aviation System Performance Standards for Flight Information 

Services-Broadcast (FIS-B) Data Link, Sections 2.0 and 3.0, dated April 4, 2004. Compliance 

5 
AC 20-149 8/31/05 

with RTCA/DO-267A, Section 2.2.11.2.1, Weather Product Discard, does not apply to airborne 

FIS-B equipment requirements. 

 b. FIS Provider Requirements. FIS providers should meet the interoperability requirements 

in RTCA/DO-267A, Sections 3.0 and 4.0. 

7. GROUND AND FLIGHT TEST EVALUATION. 

 a. FIS-B products available for display to the cockpit will likely undergo product 

improvement changes while the aircraft operator subscribes to various FIS providers for products 

best suiting their individual operational needs. This AC takes into account the means of 

mitigating hazards associated with post-design approval changes to FIS-B product content. Such 

post-design approval changes would be a direct result of the aircraft operator changing FIS 

providers, or the FIS provider offering FIS-B product enhancements. 

 b. Flight test guidelines for FIS-B equipment are in AC 20-140, Section 10. We expect 

applicants to demonstrate the guidelines of AC 20-140, Section 10, during the initial type 

certification effort for installation of FIS-B systems and equipment. If there are FIS-B system

constraints per paragraph 5(c) above, we won’t require a re-demonstration of AC 20-140, 

Section 10 for post certification minor changes to the aircraft user-modifiable FIS-B message 

content (that is, FIS provider unique uplinks). 

c. RTCA/DO-267A, Section 3.8 and Table 3-2, outlines appropriate color use for FIS-B 

equipment. The colors red, amber/yellow, and green have special significance, due to their 

stereotypical use to convey status, urgency, or criticality of conditions. The following 

conventions are acceptable in all aircraft installations. First, a progression from green to amber 

to red representing increasing degrees of threat, potential hazard, safety criticality, or need for 

flight crew awareness or response. Red and amber/yellow are typically reserved for conditions 

with safety consequences, such as system failures, severe weather, envelope limits, etc. Red is 

used to identify significant safety threats, either immediate (a fire warning) or potential (severe 

weather, even if not on the projected flight path). Amber/yellow is used to identify less 

significant threats. Green is used to indicate normal conditions or other conditions that do not 

represent significant threats. 

 d. To ensure compatibility with existing displays and to ensure that they maintain 

effectiveness across a wide variety of functions and applications, apply the following principles 

when determining what, if any, features of FIS-B displays should be coded red, amber and green. 

Use the following Part 25 guidance instead of the color guidance in RTCA/DO-267A, section 3.8 

and Table 3-2: 

 (1) Color assignments should follow the “strategic display philosophy of increasing 

potential safety hazard” so that the progression from green to amber (yellow) to red corresponds 

to increasing degrees of threat, hazard, safety criticality, or need for flight crew awareness or 

response. 

(2) The uses of red, yellow/amber, and green must be compatible, although not 

necessarily identical, across the various displays and indications, to ensure that they maintain 

their effectiveness and intended functions. 

6
8/31/05 AC 20-149 

(3) If used, red should be associated with a need for immediate flight crew awareness 

and/or conditions that represent serious near-term or serious potential threats to safety.

(4) If used, amber should be associated with a need for flight crew awareness and/or 

conditions that represent moderate near-term or moderate potential threats to safety. 

(5) If used, green should be associated with normal, safe operation. 

(6) At no time should a display surface simultaneously present color-coded information 

that requires immediate awareness and possible action in combination with like color-coded 

information that is advisory in nature. 

 e. The flight crew should be able to quickly, accurately and consistently differentiate between 

time-critical information and dated, non-time-critical information. 

8. BACKGROUND. 

 a. The FAA’s goal for FIS in the cockpit is to use digital data link to deliver information to 

the pilot, and in doing so, improve safety, reduce costs to users and the FAA, and increase the 

utility, efficiency, and capacity of the national airspace system (NAS). Timely delivery of high 

quality, accurate, and consistent information is essential for sound operational decisions by 

pilots, controllers, and dispatchers. 

 b. For many years, the Aircraft Communication Addressing and Reporting System (ACARS) 

have given aircraft operators a means of digitally up-linking weather and NAS status information 

for display in text format. More recently, short-term weather uplink programs sponsored by the 

FAA were made available to ACARS equipped aircraft, at selected airports. Text messages and 

basic alphanumeric character graphics could be generated based on data from either Terminal 

Doppler Weather Radar (TDWR) or the Integrated Terminal Weather System (ITWS) test bed. 

These weather products include terminal weather conditions with descriptions/depictions of the 

present and expected convective activity, including gust fronts and microbursts within 15 

nautical miles of the terminal area. This gave pilots strategic information to help with their inflight planning before arriving or departing the terminal area. 

 c. On May 1, 1998, the FAA published the Airborne Flight Information Services (FIS) Policy 

Statement, high-level guidance for the implementation of FIS services. To speed early 

implementation of FIS services, the FAA in July 1999 signed a five year Government-Industry 

Project Performance Agreement (G-IPPA) with a third party, non-federal FIS Data Link (FISDL) 

provider to disseminate basic weather and NAS status information as a VHF data communication 

service. Format and coding of these information products is described in AC-00-45E, Aviation 

Weather Services, dated December 1999, and the Aeronautical Information Manual (AIM), 

Paragraph 7-1-27. 

 d. This third-party VHF FISDL provider sends a basic set of free weather products to 

appropriately equipped aircraft, and uplinks value added services on a paid subscription basis. 

The basic set of products includes: 

7 
AC 20-149 8/31/05 

Aviation Routine Weather Reports (METARs). 

• Aviation Selected Special Weather Reports (SPECIs). 

• Terminal Area Forecasts (TAFs), and their amendments. 

• Significant Meteorological Information (SIGMETs). 

• Convective SIGMETs. 

• Airman’s Meteorological Information (AIRMETs). 

• Pilot Reports (both urgent and routine) (PIREPs).

• Alert Severe Weather Watch bulletins (AWWs), as issued by the NWS. 

 e. VHF FISDL value added services are provider-unique products for subscribers who pay 

for them. Value added services offer more data content and format than the basic requirements 

listed above. They include: 

• Precipitation maps based on NEXRAD mosaics, 

• Graphical presentations of in-flight icing conditions, turbulence depictions, 

• NOTAMs, and

• Special Use Airspace (SUA) depictions. 

9. RELATED INFORMATION. We consider the following documents essential for 

determining the means for showing that the FIS-B data communications system complies with 

the certification basis. 

• RTCA/DO-267A, Minimum Aviation System Performance Standard (MASPS) for 

Flight Information Services-Broadcast (FIS-B) Data Link, dated April 4, 2004. 

• AC 20-140, Guidelines for Design Approval of Aircraft Data Link Communications 

Equipment, dated August 16, 1999. 

• AC 23.1311-1, Installation of Electronic Display Instrument Systems in Part 23 

Airplanes, dated June 11, 1993. 

• AC 25-11, Transport Category Airplane Electronic Display Systems, dated 

July 16, 1987. 

• AC 120-76A, Guidelines for the Certification, Airworthiness, and Operational 

Approval of Electronic Flight Bag Computing Devices, dated March 17, 2003.

8
• AC 00-62, Internet Communications Of Aviation Weather And NOTAMS, dated 

November 1, 2002. 

• Doc 4444, ATM/501, International Civil Aviation Organization (ICAO), Procedures 

for Air Navigation Services / Air Traffic Management, 14th Edition, dated 

November 1, 2001. 

David W. Hempe 

Manager, Aircraft Engineering Division 

Aircraft Certification Service 

9 (and 10) 

8/31/05 AC 20-149 

APPENDIX 1. DEFINITIONS AND ACRONYMS 

1. Definitions. 

Airline Operations Control Center (AOCC). An air carrier dispatch service, or other 

operator’s aeronautical weather and operational information service. 

Basic Product: A product offered by the FAA FISDL provider at no cost to the contract holder. 

Broadcast Data Link: Data link transmission with no requirement for an initiating request from

the receiving station. Further, the broadcast data link transmission, as defined in RTCA/DO267A, does not contain message recipient address information. 

Broadcast message: Message using a broadcast protocol that does not depend on a request from

the receiver. This AC refers specifically to the broadcast protocol in RTCA/DO-267A. 

Flight Information Services (FIS). The ICAO defines FIS in the 14th Edition of Doc 4444, 

ATM/501, Procedures for Air Navigation Services / Air Traffic Management, November 1, 

2001, as a service provided for the purpose of giving advice and information useful for the safe 

and efficient conduct of flight. Further, ICAO has defined specific request-reply data link 

services in the Aeronautical Telecommunications Network (ATN) Standards and Recommended 

Practices (SARPs) document 9705. The term “FIS” in this AC, however, includes a much 

broader scope of services, applications, and formats: FIS includes near real-time advisories and 

warnings that may affect flight safety and flight information planning services used in strategic 

flight planning. Additionally, FIS is limited to broadcast data link services not requiring requestreply. 

Flight Information Services-Broadcast (FIS-B). Means of disseminating FIS by broadcast (a 

non-directed transmission intended to be received by all stations).

Flight Information Services Data Link (FISDL). The provision of FIS data over various 

broadcast data links, including weather and operational information for display in the cockpits of 

appropriately equipped aircraft. 

(FAA) FISDL Service Provider: Organization providing FAA FISDL on Aeronautical 

Spectrum under an agreement with the FAA. 

(Non-FAA) FISDL Service Provider: Organization that operates a commercial data link 

system providing aviation weather and operational information without an agreement with the 

FAA. 

Flight Information Service Provider (Non-FAA): Commercial data link service providing 

aviation weather and operational information to customers. 

A 1-1
AC 20-149 8/31/05 

APPENDIX 1. DEFINITIONS AND ACRONYMS (CONTINUED) 

Graphical product: FIS product composed of graphics with associated supporting text. 

NEXRAD: NEXRAD (Next Generation Weather RADAR) is a Doppler weather radar system

developed and deployed as a tri-agency program by the Department of Transportation (FAA), the 

Department of Commerce (NWS), and the Department of Defense. NEXRAD provides surface 

weather radar coverage and is an essential input to various aviation weather products. NEXRAD 

radar systems are designated WSR-88D (Weather Surveillance RADAR-88 Doppler). 

Text product: FIS product composed of text only. 

Value-Added Product: Product offered by an FAA FISDL provider for a fee. 

A 1-2 
8/31/05 AC 20-149 

APPENDIX 1. DEFINITIONS AND ACRONYMS (CONTINUED) 

Acronym Description

AC Advisory Circular 

ACARS Aircraft Communication, Addressing and Reporting System

ACO Aircraft Certification Office 

AIM Aeronautical Information Manual 

AIRMET Airman's Meteorological Information 

AOCC Airlines Operation Control Center 

AFSS Aircraft Flight Service Station 

A/RFM Airplane/Rotorcraft Flight Manual 

ATC Air Traffic Control 

ATN Aeronautical Telecommunication Network 

AWW Alert Severe Weather Watch 

FAA Federal Aviation Administration 

FIS Flight Information Service 

FIS-B Flight Information Services – Broadcast 

FISDL Flight Information Service Data Link 

FSS Flight Service Station 

G-IPPA Government – Industry Project Performance Agreement 

ICAO International Civil Aviation Organization 

ITWS Integrated Terminal Weather System 

METARs Aviation Routine Weather Reports 

MOPS Minimum Operational Performance Standard 

NAS National Airspace System 

NEXRAD Next Generation Radar 

NIDS NEXRAD Information Distribution System

NOTAM Notice to Airmen 

NWS National Weather Service 

PIREPs Pilot Reports

SARPS Standards and Recommended Practices 

SIGMET Significant Meteorological Information

SPECIs Special Aviation Reports 

A 1-3
AC 20-149 8/31/05 

APPENDIX 1. DEFINITIONS AND ACRONYMS (CONTINUED) 

Acronym Description

TAFs Terminal Area Forecasts

TDWR Terminal Doppler Weather Radar 

TSO Technical Standard Order 

VHF Very High Frequency 

A 1-4 
8/31/05 AC 20-149 

APPENDIX 2. OPERATIONAL HAZARD ASSESSMENT 

OF FIS-B PRODUCTS

Failure Description Failure 

Condition 

Hazard 

Classification

Remarks and Assumptions 

Function Loss of 

FIS-B data, all flight

phases 

No information 

displayed to 

flight crew 

Minor FIS-B data not required for 

normal operations. 

Loss readily apparent to flight 

crew. 

Marginal increase in pilot 

workload. 

Flight crew uses VHF voice as 

backup. 

Malfunction of FIS-B 

equipment, all flight

phases 

Misleading 

information 

displayed to 

flight crew 

Minor FIS data not required for 

normal operations. 

Flight crew should not initiate 

evasive maneuvers based 

solely on FIS-B data 

communications equipment. 

Marginal increase in pilot 

workload. 

Flight crew uses VHF voice as 

backup. 

A 2-1 (and 2-2) 

8/31/05 AC 20-149 

APPENDIX 3. FORM TO SUBMIT SUGGESTIONS FOR IMPROVEMENT

Use this form, or create your own to submit comments for improving future releases of advisory 

material on design approval of data communications systems and applications. 

Suggestion for Improvement 

Send To: FAA, Aircraft Certification Service 

Aircraft Engineering Division (AIR-130) 

800 Independence Avenue

Washington, D.C. 

Date: 

Name: 

Voice: Address

Fax:

Internet:

Reference sections: 

Rationale (Describe the reason for the change) 

Proposed change (Attach marked-up text or proposed rewrite) 

Please provide general comments to improve this AC

A 3-1 (and A 3-2)