Acronym

23.1 Introduction

Aeronautical data are “data used for aeronautical applications such as navigation, flight planning, flight simulators, terrain awareness and other purposes, which comprises navigation data and terrain and obstacle data” [1]. An aeronautical database is “a collection of data that is organized and arranged for ease of electronic storage and retrieval in a system that supports airborne or ground-based aeronautical applications” [1].

Aeronautical data are treated differently than the configuration data that were discussed in Chapter 22. The configuration data discussed in Chapter 22 are approved as part of the aircraft’s type design data. However, aeronautical data are often not part of the type design data. Instead, loading such data is frequently treated as a maintenance action that is identified in the aircraft’s Instructions for Continued Airworthiness. Title 14 of the U.S. Code of Federal Regulations Part 43.3 allows this approach and treats such updates as preventative maintenance. There are at least a couple of reasons that aeronautical data are treated differently than configuration data.

First, aeronautical data typically require frequent updates that are not practical to implement under the type certification process. For example, navigation databases are updated every 28 days. To go through the DO-178C software approval process and supplemental type certification or amended type certification every 28 days is virtually impossible. Terrain databases are updated less frequently (perhaps three or four times per year), which is still too frequent for the DO-178C process to be viable.

Second, the source of the data for such databases is often a government organization rather than an avionics or aircraft manufacturer. The International Civil Aviation Organization (ICAO) Annex 15 places requirements on the ICAO contracting states around the world that are responsible for compiling and transmitting the aeronautical data through Aeronautical Information Publications [2]. “Each Contracting State must take all necessary measures to ensure that the aeronautical information/data it provides is adequate, of required quality (accuracy, resolution and integrity) and provided in a timely manner for the entire territory that the State is responsible for” [1]. In the past, ICAO requirements were primarily applicable to navigational data. Recently, terrain data requirements have also been included in the ICAO requirements. As noted in Chapter 22, DO-178C does not generally apply to aeronautical data. However, RTCA DO-200A, entitled Standards for Processing Aeronautical Data, does apply to this kind of data. The Federal Aviation Administration (FAA) recognizes DO-200A in Advisory Circular (AC) 20-153A, Acceptance of Aeronautical Data Processes and Associated Databases, and in various other documents (including Technical Standard Order (TSO)-146c, TSO-151b, AC 20-138B, AC 90-101A, Order 8110.55A, and Order 8110.49).

This chapter surveys DO-200A, AC 20-153A, and several other FAA and industry documents related to aeronautical data in order to provide a highlevel overview of expectations for aeronautical data.

23.2 DO-200A: Standards for Processing Aeronautical Data

RTCA’s DO-200A (as well as its European Organization for Civil Aviation Equipment (EUROCAE) equivalent, ED-76) is recognized as the standard for ensuring the quality of aeronautical data. DO-200A is referenced in the following FAA documents, just to name a few:

• AC 20–153A—Acceptance of Aeronautical Data Processes and Associated Databases

• Order 8110.55A—How to Evaluate and Accept Processes for Aeronautical Database Suppliers

• Order 8110.49—Software Approval Guidelines

• AC 20–138B—Airworthiness Approval of Positioning and Navigation Systems

• AC 90–101A—Approval Guidance for Required Navigation Performance (RNP) Procedures with Authorization Required (AR)

• TSO-C151b—Terrain Awareness and Warning System (TAWS)

• TSO-C146c—Stand-Alone Airborne Navigation Equipment Using the Global Positioning System Augmented By The Satellite Based Augmentation System

This section provides an overview of DO-200A. The next section examines the FAA’s AC 20-153A and Order 8110.55A, which define the process for obtaining a letter of acceptance for a DO-200A compliant process.

DO-200A is considered the minimum standard and guidance to address the processing quality assurance and data quality management of aeronautical data used for navigation, flight planning, terrain awareness, flight simulators, etc. The output of the DO-200A compliant process is a database that is distributed to the user for implementation in their equipment.

DO-200A identifies requirements and recommendations to provide the appropriate assurance level for the aeronautical data. DO-200A defines assurance level as “the degree of confidence that a data element is not corrupted while stored or in transit. This can be categorized into three levels: 1, 2, and 3; with 1 being the highest degree of confidence” [1]. As with the DO-178C software levels, DO-200A assurance levels are determined by the potential impact of corrupted data on safety. DO-201A (discussed in Section 23.5.1) defines the assurance levels for aeronautical information related to area navigation (RNAV). Assurance levels for applications of data not covered by DO-201A need to be determined by the end user or application provider, based on the safety impact [2].

Table 23.1 shows the three DO-200A assurance levels and their relationship to the ICAO criticality levels and the failure condition categories. The related development assurance levels (DALs) or software levels are also shown. The ICAO classifications of critical, essential, and routine are defined as follows [3]:

• Critical data (Assurance Level 1)—The data, if erroneous, would prevent continued safe flight and landing or would reduce the ability to cope with adverse operating conditions to the extent that there is a large reduction in safety margins or functional capabilities. There is a high probability when trying to use corrupted critical data that an aircraft would be placed in a life threatening situation;

  Table 23.1 DO-200A Assurance Levels

  DO-200A Assurance Level	Related Requirement on State-Provided Data (ICAO)	Failure Condition Category	DAL or SW Level
  1	Critical	Catastrophic or hazardous/ severe-major	A, B
  2	Essential	Major or minor	C, D
  3	Routine	No safety effect	E

• Essential data (Assurance Level 2)—The data, if erroneous, would reduce the ability to cope with adverse operating conditions to the extent that there is a significant reduction in safety margins. There is a low probability when trying to use corrupted essential data that an aircraft would be placed in a life threatening situation;

• Routine data (Assurance Level 3)—The data, if erroneous, would not significantly reduce airplane safety. There is a very low probability when trying to use corrupted routine data that an aircraft would be placed in a life threatening situation.

DO-200A uses the concept of an aeronautical data chain to explain the path that the aeronautical data takes: “An aeronautical data chain is a series of interrelated links wherein each link provides a function that facilitates the origination, transmission, and use of aeronautical data for a specific purpose” [1]. There are normally five major links, including origination, transmission, preparation, application integration, and end use [1]. There may be multiple organizations involved in a single link (e.g., there may be sublinks in the preparation and transmission phases), or a single organization may perform multiple types of links (e.g., one company may originate, prepare, and transmit data). The originator is “the first organization in an aeronautical data chain that accepts responsibility for the data. For example, a State or RTCA DO-200A/EUROCAE ED-76-compliant organization” [1]. An end user is “the last user in an aeronautical data chain. Aeronautical data end-users are typically aircraft operators, airline planning departments, air traffic service providers, flight simulation providers, airframe manufacturers, systems integrators, and regulatory authorities” [1]. Figure 23.1 illustrates a typical aeronautical data chain.

At each link in the aeronautical data chain, the data should satisfy the following seven quality characteristics based upon the intended func tion that will use the data: (1) accuracy, (2) resolution, (3) assurance level (based on the safety assessment), (4) traceability (to the origin of the data), (5) timeliness (to support need for valid and current data), (6) completeness (all necessary data provided), and (7) format (consistent with the data’s intent, including transmission resolution). These data quality requirements are defined based upon the intended function supported by the data.

DO-200A focuses on the preparation and transmission links in the aeronautical data chain. While origination, application integration, and end use links are mentioned in order to provide context, they are considered beyond the scope of DO-200A.

The aeronautical data preparation functional link includes the following four phases:

1. Assemble—collecting data from suppliers

2. Translate—changing the information format (often combined with the assemble phase)

3. Select—choosing desired data from the collection of assembled aeronautical data

4. Format—transforming the data into the format acceptable for the next functional link

The aeronautical data transmission functional link includes two phases:

• Receive—accepting, verifying, and validating data

• Distribute—last phase of the processing model which becomes part of the transmission link

At each phase of the processing, the data are verified and any issues are documented in an error report. Corrective action is taken as needed. If the data from a trusted source, such as an ICAO member state, are found to have an error, the error must be reported to the trusted source. However, it is often difficult to get the trusted source to immediately correct the data. Oftentimes, once the data are confirmed to be erroneous, they are corrected by the organization that applies the DO-200A compliant process.

DO-200A section 2 defines the guidance for each organization in order to ensure that the data satisfy the seven quality characteristics mentioned earlier. Each organization in the data chain is responsible for the following:

• Developing a compliance plan

• Defining data quality requirements

• Defining the data processing procedures

• Ensuring that data alteration is not performed unless properly coordinated with the originator

• Maintaining configuration management

• Ensuring the skills and competencies of personnel

• Performing tool assessment and qualification as needed

• Developing and implementing quality management procedures

Depending on the assurance level, the amount of required validation and verification varies. DO-200A defines validation and verification as follows [1]:

• Validation—The activity whereby a data element is checked as having a value that is fully applicable to the identity given to the data element, or a set of data elements that is checked as being acceptable for their purpose.

• Verification—The activity whereby the current value of a data element is checked against the value originally supplied.

In general, for assurance level 1, validation by application (i.e., applying the data under test) and verification are required; for assurance level 2, validation by application is not required, but verification is; and for assurance level 3, validation and verification are recommended but not required [1].

23.3 FAA Advisory Circular 20-153A

Just as the previous section provided a high-level overview of DO-200A, this section includes a summary of FAA AC 20-153A.

AC 20-153 (the predecessor to AC 20-153A) only applied to navigation databases. In 2010, the FAA expanded the AC to apply to other types of aeronautical data, including terrain, obstacle, and airport map databases. Each of the databases covered by AC 20-153 is briefly explained as follows. The AC may be applied to other databases; however, those should be closely coordinated with the certification authority.

• Navigation database—”Any navigation data stored electronically in a system supporting navigation applications. Navigation data is information intended to be used to assist the pilot to identify the aircraft’s position with respect to flight plans, ground reference points and navaid fixes … as well as items on the airport surface” [2].

• Terrain database—”Any data stored electronically in a system supporting terrain applications. Terrain data includes the natural surface of the earth excluding man-made obstacles” [2].

• Obstacle database—”Any data stored electronically in a system supporting obstacle applications. Obstacle data includes any natural or manmade fixed object which has vertical significance in relation to adjacent and surrounding features and which is considered as a potential hazard to the safe passage of aircraft” [2].

• Airport map database—”Any navigation data stored electronically in a system supporting airport map applications. Airport map data is information intended to be used to assist the pilot to identify the aircraft’s position with respect to items on the airport surface” [2].

AC 20-153A provides guidance to aeronautical service providers, equipment or avionics manufacturers, and/or operators necessary to obtain a letter of acceptance (LOA). An LOA is a letter granted by the FAA, acknowledging compliance with AC 20-153A and DO-200A for aeronautical data processing. “The LOA formally documents that a supplier’s databases are being produced pursuant to RTCA/DO-200A, or for some established systems, RTCA/DO-200” [2]. AC 20-153A identifies two types of LOAs:

• Type 1 LOA: Type 1 acceptance letters are primarily for data suppliers that are data service providers. “A Type 1 LOA provides recognition of a data supplier’s compliance with RTCA/DO-200A with no identified compatibility with an aircraft system… This acceptance letter may be issued to data suppliers, operators, avionics manufacturers, or others” [2].

• Type 2 LOA: “Type 2 acceptance letters are based on requirements that ensure compatibility with particular systems or equipment and are for data suppliers that are avionics manufacturers/application integrators… Type 2 data suppliers have additional requirements to ensure the delivered database is compatible with the DQRs [data quality requirements] necessary to support the intended function approved for the target application” [2].^**

AC 20-153A explains the LOA application process and how to apply DO-200A and additional requirements for Types 1 and 2 LOA applications. The AC also provides additional notes about DO-200A processes. Guidance is provided for operators, equipment and avionics manufactures (i.e., application providers), and data service providers. The AC also explains that contracting states are encouraged to follow DO-200A, as well as other applicable data quality guidelines (e.g., DO-201A, DO-272B, and DO-276A).

AC 20-153A section 14 explains that data obtained from a DO-200A compliant source or from a contracting state may be trusted. However, data from other suppliers must be verified and validated for the appropriate assurance level. Per the AC, DO-272B (section 3.9) provides acceptable techniques for verification and validation of airport map data [4].^* Likewise, per the AC, DO-276A (sections 6.1.4 and 6.1.5) provides acceptable verification and validation techniques for terrain and obstacle data [5].

AC 20-153A section 17 provides a correction to DO-200A’s error detection probabilities. The AC points out that for assurance level 1, the error detection must have a probability of undetected corruption of less than or equal to 10−9 (rather than 10−8 as identified in DO-200A). Likewise, for assurance level 2, the error detection must have a probability of undetected corruption of less than or equal to 10−5 (rather than 10−4 as identified in DO-200A). These probabilities better align with XX.1309 requirements at the aircraft level [2].^†

AC 20-153A Appendix 3 provides a compliance matrix for aeronautical database suppliers to use to help ensure that they satisfy the DO-200A and AC 20-153A requirements prior to applying for an LOA.

In addition to AC 20-153A, the FAA has published Order 8110.55A, How to Evaluate and Accept Processes for Aeronautical Database Suppliers [6]. The Order provides guidelines for FAA Aircraft Certification Offices to evaluate and accept aeronautical processes and to grant LOAs. While this Order is primarily for FAA staff, it provides some insight for aeronautical database providers on what to expect during FAA audits and how to prepare for such audits.

23.4 Tools Used for Processing Aeronautical Data

Because of the volume of data and the need for repeatability, aeronautical data processing is tool intensive. Typically, a combination of integrity checks (such as cyclic redundancy checks) and qualified tools are used to ensure the integrity of the aeronautical data as they go through the data chain. Sometimes, tools are run in parallel and results compared to avoid the need for qualification. All tools must be identified and assessed. Tools whose output is not verified may require qualification. DO-200A and AC 20-153A reference DO-178B section 12.2 criteria for tool qualification. DO-178C’s section 12.2 is also acceptable. As explained in Chapter 13, DO-178C section 12.2 invokes DO-330, Software Tool Qualification Considerations. DO-330 was written to be applicable to multiple domains, including the aeronautical data domain. DO-330 frequently asked question (FAQ) D.7 may provide valuable information for aeronautical data processing tools in some scenarios. This FAQ describes how the output of an unqualified tool may be verified by a qualified tool to ensure the accuracy of the unqualified tool.

23.5 Other Industry Documents Related to Aeronautical Data

DO-200A and AC 20-153A reference several other industry documents. A brief summary of these documents is provided to complete the survey of aeronautical database guidance. The RTCA documents are presented first (in sequential order), followed by two ARINC documents.