AC 20-167A

U.S. Department of Transportation Federal Aviation Administration Advisory Circular Subject: Airworthiness Approval of Enhanced Vision System, Synthetic Vision System, Combined Vision System, and Enhanced Flight Vision System Equipment Date: 12/6/16 Initiated by: AIR-130 AC No: 20-167A This advisory circular (AC) provides guidance for gaining airworthiness approval for enhanced and synthetic vision systems in aircraft. Specifically, it provides one acceptable means for complying with Title 14 of the Code of Federal Regulations (14 CFR) part 23, 25, 27, or 29 airworthiness regulations when installing a synthetic vision system (SVS), enhanced vision system (EVS), combined vision system (CVS), or enhanced flight vision system (EFVS) in an airplane or rotorcraft.

Since the release of Draft AC 20-167A for public comment, the FAA revised the standard format for Advisory Circulars. AC 20-167A is formatted in compliance with the new standard format, meaning the numbering of paragraphs changed from the draft that was presented for public comment. The preamble accompanying the 2016 EFVS rule specifically references paragraphs 4-5, 4-5.c.4, 4-5.c.4.(h).(iv), and 6-2.f.4. These referenced paragraphs equate to paragraphs 4.5,

4.5.3.4, 4.5.3.4.8.4, 6.2.6.4, respectively.

If you have suggestions for improving this AC, you may use the Advisory Circular Feedback form at the end of this AC.

Richard E. Jennings Acting Manager, Design, Manufacturing, & Airworthiness Division Aircraft Certification Service

ii Table of Contents Paragraph Page

Chapter 1. Introduction1-1

1.1 Purpose1-1

1.2 Audience1-1

1.3 Applicability1-1

1.4 How to Use This Document1-2

1.5 Definitions and acronyms are in Appendix I1-2

1.6 Cancellation1-2

Chapter 2. Vision Systems Overview2-1

2.1 Enhanced Vision Systems2-1

2.2 Synthetic Vision Systems2-2

2.3 Combined Vision Systems2-5

2.4 Enhanced Flight Vision Systems2-6

Chapter 3. Airworthiness Package Contents3-1

3.1 Airworthiness Package3-1

3.2 Intended Function3-1

Chapter 4. System Criteria4-1

4.1 EVS or SVS (or CVS when EVS and SVS combined) – General4-1

4.2 EVS Specific Criteria4-4

4.3 SVS Specific Criteria4-6

4.4 CVS Specific Criteria4-10

4.5 EFVS – General and Specific Criteria4-11

Chapter 5. Systems Installation Considerations5-1

5.1 EVS/SVS/CVS Installations Considerations5-1

5.2 EFVS Display (HUD or Equivalent) Installation Considerations5-3

5.3 HIRF Considerations for All Installations (EVS, SVS, CVS, and EFVS)5-9

Chapter 6. Performance Evaluation6-1

6.1 EVS/SVS/EFVS Performance Demonstration6-1

6.2 Performance Demonstration of EFVS Landing System6-2

6.3 Environmental Qualification and Design Assurance6-4

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Appendix A. FAA EFVS 14 CFR Compliance (Partial List)A-1

A.1 Airworthiness StandardsA-1

A.2 EFVS ComplianceA-1

Appendix B. EFVS Approach System and EFVS Landing System Systems Safety GuidanceB-1

B.1 GeneralB-1

B.2 Required Level of SafetyB-1

B.3 DemonstrationB-2

B.4 State DataB-2

Appendix C. EFVS Approach System and II Safety StandardsC-1

C.1 Safety factors for EFVS described in this ACC-1

C.2 FeaturesC-1

C.3 DemonstrationC-2

C.4 In addition to the sensor imagery, at least the following specific aircraft flight

information must be displayed:C-4

C.5 Head-Up DisplayC-4

Appendix D. Sample EFVS Approach System Flight Test ConsiderationsD-1

D.1 General Flight Test ConsiderationsD-1

D.2 Minimum Flight Test Conditions ObservedD-1

D.3 Test PointsD-2

D.4 Evaluation During TaxiD-3

D.5 Take off EvaluationD-3

D.6 Climb and Descent and Lateral Modes EvaluationD-3

D.7 Instrument ApproachesD-3

D.8 Flare Landing and Go AroundD-4

D.9 Copilot MonitorD-4

D.10 Failure CasesD-4

D.11 Ice Protection System EvaluationD-4

D.12 Evaluation MatrixD-5

Appendix E. Sample Flight Test Considerations for EFVS Landing SystemE-1

E.1 General Flight Test ConsiderationsE-1

E.2 Minimum Flight Test Conditions ObservedE-1

E.3 Test PointsE-3

iv

E.4 Evaluation During TaxiE-4

E.5 Take off EvaluationE-4

E.6 Climb and Descent and Lateral Modes EvaluationE-5

E.7 Instrument Approaches to the DA(H)E-5

E.8 Final Approach from the DA/DH, Flare, Landing and Rollout to Safe Taxi SpeedE-5

E.9 Rejected LandingE-5

E.10 Pilot Monitoring (PM) DisplayE-5

E.11 Failure CasesE-6

E.12 Ice Protection System EvaluationE-6

E.13 Evaluation MatrixE-6

Appendix F. Sample Airplane Flight Manual (AFM) SupplementF-1

Appendix G. Installation of Enhanced Vision System and or/Synthetic Vision System on

RotorcraftG-1

G.1 GeneralG-1

G.2 ApplicabilityG-1

G.3 Airworthiness ApprovalG-1

G.4 Design ConsiderationsG-1

Appendix H. Additional Part 23 Considerations for Enhanced Vision System/or Synthetic

Vision System for Situation Awareness OnlyH-1

H.1 IntroductionH-1

H.2 Terrain AlertingH-1

H.3 Moving Map Display that Corresponds to and Complements Synthetic Vision PFD

DisplayH-2

H.4 Minimums Audio Callout CapabilityH-2

H.5 Digital Evaluation Model (DEM) ResolutionH-2

H.6 Aircraft Flight Manual Supplement (AFMS)H-3

H.7 SVS Unusual Attitude RecoveryH-3

H.8 Pilot EvaluationH-4

Appendix I. Definitions and AcronymsI-1

I.1 DefinitionsI-1

I.2 AcronymsI-5

Appendix J. Related PublicationsJ-1

v

J.1 Related PublicationsJ-1

J.2 How to Get PublicationsJ-3

Appendix K. Advisory Circular Feedback InformationK-1

List of Figures Figure Page

Figure 1. Enhanced Vision Diagram2-1

Figure 2. Synthetic Vision Diagram2-3

Figure 3. Minimum Detection Range4-14

Figure 4. Field of ViewI-3

List of Tables Table Page

Table 1. EFVS Visibility and Visual Reference Requirements4-13

Table 2. System Operating Phases for Considerations5-2

Table 3. EFVS Acceptable Methods of ComplianceA-1

Table 4. Required Level of Safety, 14 CFR part 25 AircraftB-2

Table 5. Example EFVS/HUD Functional Hazard Assessment, 14 CFR part 25 Aircraft, ILS

Approaches to 100 ft Height Above Touchdown, RVR 1200 ftB-3

Table 6. EFVS Approach System Evaluation MatrixD-5

Table 7. EFVS Landing System Evaluation MatrixE-6

1-1 CHAPTER 1. INTRODUCTION

1.1 Purpose

1.1.1 In this advisory circular (AC), the Federal Aviation Administration (FAA) provides guidance on airworthiness approvals of enhanced vision system (EVS), synthetic vision system (SVS), combined vision system (CVS), and enhanced flight vision system (EFVS) equipment installation. The FAA has attempted to use regulatory language that is performance based and not limited to a specific sensor technology. The FAA believes this action will accommodate future growth in sensor technologies used in vision systems.

1.1.2 Existing ACs address flight guidance symbology, head-up displays (HUD) and visual display characteristics (for example, AC 25-11B, Electronic Flight Deck Displays, AC

25.1329-1B, Approval of Flight Guidance Systems and AC 23.1311-1C Installation of Electronic Display in Part 23 Airplanes). For a complete listing of related regulations and guidance, refer to Appendix A and Appendix J. This AC complements existing guidance.

1.1.3 This AC is not mandatory and does not constitute a regulation. This AC describes an acceptable means, but not the only means, to install and obtain airworthiness approval for enhanced and synthetic vision technologies. However, if you use the means described in this AC, you must follow it in all aspects.

1.2 Audience This AC is for airplane and rotorcraft manufacturers, modifiers, and type certification engineers seeking certification or installation guidance for their visual display system.

Sections 23.773, 25.773, 27.773 and 29.773 address vision systems using a transparent display surface located in the pilot’s outside view, such as a head-up-display, headmounted display, or other equivalent display. Such “vision systems” could include any EVS, EFVS, SVS, or CVS.

1.3 Applicability

1.3.1 This AC applies to all applicants for a new type certificate (TC), an amended type certificate (ATC), or a supplemental type certificate (STC), to install enhanced and/or synthetic vision systems and equipment. The method of compliance described in this AC can be used to obtain a TC, STC, or ATC for an airplane or rotorcraft equipped with SVS, EVS, CVS, or EFVS equipment.

1.3.2 This AC does not address operational aspects of vision systems or any changes in aircraft operational capability that may result from installation of vision systems.

Guidance material for the operational aspects of EFVS described in this AC can be found in AC 90-106A, Enhanced Flight Vision Systems.

1-2

1.4 How to Use This Document

1.4.1 This AC provides methods, procedures, and practices acceptable to the FAA for complying with regulations. EFVS compliance references are listed in Appendix A.

1.4.2 This material does not alter regulatory requirements.

1.4.3 This AC describes system performance.

1.4.4 EFVS safety standards and sample flight test considerations for EFVS conducted to 100 feet height above runway touchdown zone elevation (EFVS Approach System) and for EFVS operations conducted to touchdown and rollout (EFVS Landing System) are in Appendices B, C, D, and E.

1.4.5 A sample flight manual supplement is outlined in Appendix F.

1.4.6 Appendix G addresses specific installation guidance for EVS and/or SVS on rotorcraft.

Appendix H addresses additional part 23 considerations for situation awareness only.

1.5 Definitions and acronyms are in Appendix I.

1.5.1 Certain material within this AC is from RTCA/DO-315A, Minimum Aviation System Performance Standards (MASPS) for Enhanced Vision Systems, Synthetic Vision Systems, Combined Vision Systems, and Enhanced Flight Vision Systems. RTCA/DO- 315A is copyrighted by RTCA, Inc. and used with permission. Purchase information is in Appendix J.

1.6 Cancellation AC 20-167, Airworthiness Approval of Enhanced Vision System, Synthetic Vision System, Combined Vision System, and Enhanced Flight Vision System Equipment, dated June 22, 2010, is canceled.

2-1 CHAPTER 2. VISION SYSTEMS OVERVIEW

2.1 Enhanced Vision Systems

2.1.1 An EVS is an electronic means to provide a display of the forward external scene topography through the use of imaging sensors, such as forward looking infrared (FLIR), millimeter wave (MMW) radiometry, MMW radar, and/or low-light-level image intensifying. EVS need not provide the additional flight information/symbology required in 14 CFR 91.176 on a Head Up Display (HUD) or equivalent display. While Enhanced Vision Systems share a similarity with EFVS technology, an EVS does not have to be integrated with a flight guidance system. Furthermore, while an EVS may provide additional situation awareness without the additional capabilities provided by an EFVS, it provides no credit towards operations conducted under 14 CFR 91.176 (a) and (b). The elements of an installed EVS are listed below, with the EVS diagram shown in Figure 1:

 EVS sensor system.

 Display processor.

 EVS display.

 Pilot controls/interface.

 Mounting.

Visible External Scene Energy Atmosphere Sensor Sensor Conversion Sensor System Display Processor Pilot's Eye Enhanced Flight Vision System Aircraft State Data Head-up Display Processing Head-up Display Enhanced Vision System EVS Display Pilot Controls

Figure 1. Enhanced Vision Diagram (Dashed lines and shading represent individual system boundaries for EVS and EFVS)

2-2 Note 1: While an EFVS contains all the elements of an EVS, for the purposes of this AC any discussion of an EVS excludes an EFVS.

Note 2: For the purposes of this AC, any guidance that applies to Head Up Display (HUD) also applies to displays equivalent to HUD.

2.1.2 The categories of current EVS sensors are passive or active sensors.

2.1.2.1 Passive Sensors: Scene contrast detected by passive infrared sensors can be much different than that detected by natural pilot vision. On a dark night, thermal differences of objects, not detectable by the naked eye, will be easily detected by many imaging infrared systems. However, contrasting colors in visual wavelengths distinguished by the naked eye may not be visible using an imaging infrared system. Sufficient thermal scene contrast allows shapes and patterns of certain visual references to be recognized in the infrared image by the pilot. However, depending on conditions, they can also appear different to a pilot in the infrared image than they would with normal vision.

2.1.2.2 Active Sensors: Scene contrast by active systems depends on several parameters such as: whether the transmitter is centered on the aircraft velocity vector, display updates rates, latency, range resolution, sensitivity, dynamic range, and azimuth and elevation resolution. For an active infrared thermal imaging sensor, the infrared illuminator has the potential to illuminate more weather obscurations, which can compete with scene contrast and interpretation. One advantage of millimeter wave radar systems is their general immunity to weather obscurations.

2.1.2.3 Unlike the pilot's external view, the enhanced vision image can be a monochrome, two-dimensional display. Some, but not all, of the depth cues found in the natural view are also found in the imagery. The quality of the enhanced vision image and the level of enhanced vision sensor performance depend on the atmospheric and external visible and nonvisible energy source conditions. Gain settings of the sensor, and brightness or contrast settings of the display, can significantly affect image quality. Certain system characteristics could create distracting and confusing display artifacts.

2.2 Synthetic Vision Systems

2.2.1 Synthetic vision is a computer-generated image of the external scene topography relative to the aircraft that is derived from aircraft attitude, high-precision navigation solution, and database of terrain, obstacles, and relevant cultural features. A synthetic vision system is an electronic means to display a synthetic vision image of the external scene topography to the flight crew. Synthetic vision creates an image relative to terrain and airport within the limits of the navigation source capabilities (position, altitude, heading, track, and the database limitations). SVS provides situation

2-3 awareness but cannot be used in lieu of natural vision. The application of synthetic vision systems is through a primary flight display from the perspective of the flight deck (egocentric), or through a secondary flight display from the perspective correlating to outside the aircraft (exocentric, like a “bird’s eye” view of a moving map display). This AC addresses both perspectives. The elements of an installed SVS are listed below, with the SVS diagram shown in Figure 2.

 Display (includes interface and installation).

 System interface.

 Database of terrain and obstacles.

 Sources providing the aircraft altitude, attitude, and position.

Visible External Scene Energy Atmosphere Aircraft Altitude, Attitude, Position Database Synthetic Vision Display Processing Pilot's Eye Display

Figure 2. Synthetic Vision Diagram (Dashed lines represent individual system boundaries. External scene visible image is not affected by SVS.)

2-4

2.2.2 Synthetic vision coordinate referenced databases are usually referenced to digital terrain elevation data (DTED). Digital terrain data can help produce a digital elevation model (DEM), a terrain database used to draw the terrain image on a synthetic vision display.

Note: For information purposes, there are three DTED levels with the following terrain spacing:

 DTED Level 0 uses 30 arc second spacing (nominally one kilometer).

 DTED Level 1 uses 3 arc second spacing (approximately 100 meters).

 DTED Level 2 uses one arc second spacing (approximately 30 meters).

2.2.3 With the exception of terrain and database processing (addressed in chapter 4, paragraph 4.3.7), synthetic vision characteristics may include:

2.2.3.1 Display factors, such as:

 Conformality.

 Refresh rate.

 Field of regard (FOR).

 Field of view (FOV).

2.2.3.2 Display placement factors, such as:

 Pilot’s primary FOV versus pilot’s secondary FOV. See figure A3-1 in AC 25-11B.

 Head down display (HDD) versus Head up display (HUD).

2.2.3.3 Terrain presentation factors, such as:

 Depiction (such as monochromatic, photo-realistic, elevation coloring).

 Gridding (presence versus absence, spacing).

 Color, shading, shadowing, and texturing. (This AC does not establish criteria for these items.)

 Resolution. DEM resolution and DTED level.

 Range indication (e.g., terrain based range marks, color scheme).

2.2.3.4 Terrain and cultural features, such as:

 Rivers, valleys, and mountains.

 Major landmarks, highways, and buildings within close proximity to airport.

 Hue and contrast between terrain and sky.

2-5  Man-made obstacles (e.g., radio towers, bridges, tall buildings) and airport depiction.

 Airport depiction, including markings (e.g., extended runway centerline and numbers, taxiway markings, approach lighting system).

 Range marks or indications.

2.2.3.5 Functions, such as:

 Alerting (terrain, obstacles, traffic, and airspace).

 Declutter.

 Mode reversion.

 Image control (FOV, brightness, contrast, registration).

2.2.3.6 Integration of guidance symbology (if incorporated), such as:

 Guidance cues (flight path vector, flight path angle reference cue, velocity vector, command guidance cues, deviation indicators, and trend indicators).

 Aircraft reference relative to terrain (indication of relationship between zero pitch line and terrain).

 Pathway markings (“breadcrumbs,” rectangles) and boundaries, to indicate past or intended future aircraft track.

 Navigation information (course lines, fixes, icons, special-use airspace).

 Unusual attitude recovery.

 Crosswind indication (and image display based on cross-track).

2.3 Combined Vision Systems

2.3.1 The CVS concept involves a combination of SVS and EVS or EFVS. Some examples of a CVS include database-driven synthetic vision images combined with real-time sensor images superimposed and correlated on the same display. This includes selective blending of the two technologies based on the intended function of the vision system for which approval is sought. For example, on an approach, most of the arrival would utilize the SVS picture. As the aircraft nears the runway, the picture gradually and smoothly transitions from synthetic to enhanced vision, either for SVS picture validation or displaying the runway environment.

2.3.2 For combined vision systems applicants are expected to meet applicable performance criteria for each incorporated system.