U.S. Department

of Transportation **Federal A**

**viation Ad**  **ministration** 

# Advisory

**Circular**

**Subject:** Airworthiness Approval of Enhanced Vision System, Synthetic Vision System, Combined Vision System, and Enhanced Flight Vision System Equipment **Date: Initiated by**  **:** AIR - 130 **AC No:**  20 - 167A

**Forew ord**  This advisory circular (AC) provides guidance for gaining airworthiness approval for enhanced and synthetic vision systems in aircraft. Specifically, it p rovides 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 air plane or rotorcraft.

David W . Hempe Manager, Aircraft Engineering DivisionMM/DD/YYYY AC 20 - 167A

ii **Table of Contents Paragraph**  **Page Chapter 1. Introduction**  **................................ ................................**  **................................ ..............**  **1** 1 - 1. Purpose ................................ ................................ ................................ ............................ 1 1 - 2. AC Audience ................................ ................................ ................................ ................... 1 1 - 3. Applicability ................................ ................................ ................................ ................... 1 1 - 4. How to Use This Document ................................ ................................ ............................ 1 1 - 5. Cancellation ................................ ................................ ................................ .................... 2 **Chapter 2. Vision Systems Overview ................................**  **................................ .........................**  **3** 2 - 1. Enhanced Vision S ys tems ................................ ................................ ............................... 3 2 - 2. Sy

nthetic Vision Sy stems ................................ ................................ ............................... 4 2 - 3. Combined Vision Systems ................................ ................................ .............................. 7 2 - 4 . Enhanced Flight Vision Sy stems ................................ ................................ .................... 7 **Chapter 3. Airworthiness Package Contents ................................**  **................................ ...........**  **11** 3 - 1. Airworthiness Package ................................ ................................ ................................ .. 11 3 - 2. Intended Function. ................................ ................................ ................................ ........ 11 **Chapter 4 System Criteria ................................**  **................................ ................................**  **......... 13**  4 - 1. EVS or SVS (or CVS when EVS and SVS combined)

– General. ............................... 13 4 - 2. EVS Specific Criteria. ................................ ................................ ................................ ... 16 4 - 3. SVS Specific Criteria. ................................ ................................ ................................ ... 17 4 - 4. CVS Specific Criteria. ................................ ................................ ................................ .. 21 4 - 5. EFVS

– General and Specific Criteria. ................................ ................................ .......... 21 **Chapter 5. Systems Installation Considerations ................................**  **................................ .....**  **31** 5 - 1. EV S/SVS/CVS Installations Considerations ................................ ................................ 31 5 - 2. EFVS Installation Considerations ................................ ................................ ................. 33 5 - 3. HIRF Considerations for All Installations (EVS, SVS, CVS, and EFVS). .................. 37 **Chapte r 6. Performance Evaluation**  **................................ ................................**  **........................ 38**  6 - 1. EVS/SVS/EFVS Performance Demonstration ................................ ............................. 38 6 - 2. Performance Demonstration of EFVS II. ................................ ................................ ...... 39 6 - 3. Environmental Qualification. ................................ ................................ ........................ 40 **Appendix 1. FAA EFVS 14 CFR Compliance (Partial List) ................................**  **.............. A1**  **- 1**  1 - 1. Airworthiness Standards. ................................ ................................ .......................... A1 - 1 1 - 2. EFVS Compliance. ................................ ................................ ................................ ... A1 - 1MM/DD/YYYY AC 20 - 167A

iii **Appendix 2. EFVS I and EFVS II Systems Safety Guidance**  **................................ ............**  **A2 -**  **1** 2 - 1. General. ................................ ................................ ................................ ..................... A2 - 1 2 - 2. Required Level of Safety. ................................ ................................ ......................... A2 - 1 2 - 3. Demonstration. ................................ ................................ ................................ .......... A2 - 2 2 - 4. State Data. ................................ ................................ ................................ ................. A2 - 2 **Appendix 3. EFVS I and II Safety Standards ................................**  **................................ .....**  **A3 -**  **1** 3 - 1. Safety

factors for EFVS described in this AC ................................ .......................... A3 - 1 3 - 3. Demonstration. ................................ ................................ ................................ .......... A3 - 2 **Appendix 4. Sample EFVS I Flight Test Considerations ................................**  **................... A4**  **- 1**  4 - 1. General Flight Test Considerations. ................................ ................................ ......... A4 - 1 4 - 2. Minimum Flight Test Conditions Observed. ................................ ............................ A4 - 1 4 - 3. Tes t Points ................................ ................................ ................................ ................. A4 - 2 4 - 4. Evaluation During Taxi ................................ ................................ ............................. A4 - 2 4 - 6. Climb and Descent and Lateral Modes Evaluation ................................ ................... A4 - 3 4 - 7. Instrument Approaches. ................................ ................................ ............................ A4 - 3 4 - 8. Flare Landing and Go Around ................................ ................................ .................. A4 - 3 4 - 9. Copilot Monitor ................................ ................................ ................................ ........ A4 - 3 4 - 10. Failure Cases. ................................ ................................ ................................ ............ A4 - 3 4 - 11. Ice Protection Sy stem Evaluation ................................ ................................ ............. A4 - 4 4 - 12. Evaluation Matrix. ................................ ................................ ................................ .... A4 - 4 **Appendix 5. Sample Flight Test Considerations for EFVS II ................................**  **........... A5**  **- 1**  5 - 1. General Flight Test Considerations. ................................ ................................ ......... A5 - 1 5 - 2. Minimum Flight Test Co nditions Observed. ................................ ............................ A5 - 1 5 - 3. Test Points. ................................ ................................ ................................ ................ A5 - 2 5 - 4. Evaluation During Taxi ................................ ................................ ............................. A5 - 3 5 - 5. Take off Evaluation. ................................ ................................ ................................ .. A5 - 3 5 - 6. Climb and Descent an d Lateral Modes Evaluation. ................................ .................. A5 - 4 5 - 7. Instrument Approaches to the DA(H) ................................ ................................ ....... A5 - 4 5 - 8. Final Approach from the DA/DH, Flare, Landing and Rollout to Safe Taxi Speed. A5 - 4 5 - 9. Rejected Landing ................................ ................................ ................................ ...... A5 - 4 5 - 10. Pilot Monitoring (PM) Display . ................................ ................................ ................ A5 - 4 5 - 11. Failure Cases. ................................ ................................ ................................ ............ A5 - 5 5 - 12. Ice Protection Sy stem Evaluation. ................................ ................................ ............ A5 - 5MM/DD/YYYY AC 20 - 167A

iv 5 - 13. Evaluation Matrix ................................ ................................ ................................ ..... A5 - 5 **Appendix 6. Sample Airplane Flight Manual (AFM) Supplement ................................**  **... A6**  **- 1**  **Appendix 7. Installation of Enhanced Vision System and or/Synthetic Vision System on Rotorcraft**  **................................ ................................**  **................................ ................................**  **A 7**  **- 1**  7 - 1. General. ................................ ................................ ................................ ..................... A7 - 1 7 - 2. Applicability . ................................ ................................ ................................ ............ A7 - 1 7 - 3. Airworthiness Approval. ................................ ................................ ........................... A7 - 1 7 - 4. Design Considerations. ................................ ................................ ............................. A7 - 1 **Appendix 8. Additional Part 23 Considerations for Enhanced Vision System/or Synthetic Vision System for Situation Awareness Only**  **................................ ................................**  **....... A8**  **- 1**  8 - 1. Introduction. ................................ ................................ ................................ .............. A8 - 1 8 - 2. Terrain Alerting. ................................ ................................ ................................ ....... A8 - 1 8 - 3. Moving Map Display that Corresponds to and Complements Sy nthetic Vision PFD Display . ................................ ................................ ................................ ..................... A8 - 2 8 - 4. Minimums Audio Callout Capability . ................................ ................................ ....... A8 - 2 8 - 5. Digital Evaluation Mo del (DEM) Resolution. ................................ .......................... A8 - 2 8 - 6. Aircraft Flight Manual Supplement (AFMS). ................................ .......................... A8 - 3 8 - 7. SVS Unusual Attitude Recovery . ................................ ................................ ............. A8 - 3 8 - 8. Pilot Evaluation. ................................ ................................ ................................ ........ A8 - 3 **Appendix 9. Definitions and Acronyms ................................**  **................................ ...............**  **A9 -**  **1** 9 - 1. Definitions ................................ ................................ ................................ ................. A9 - 1 9 - 2. Acron ym s. ................................ ................................ ................................ ................. A9 - 5 **Appendix 10. Related Publications ................................**  **................................ .....................**  **A10 -**  **1** 10 - 1. Related Publications. ................................ ................................ ............................... A10 - 1 10 - 2. How to Get Publications. ................................ ................................ ........................ A10 - 2 **List of Figures Figure**  **Page** Figure 1. Enhanced Vision Diagram ................................ ................................ .............................. 3 Figure 2. S ynthetic Vision Diagram ................................ ................................ .............................. 5 Figure 3. Minimum Detection Range ................................ ................................ .......................... 24 Figure 4. Field of View ................................ ................................ ................................ ............ A9 - 3 **List of Tables**MM/DD/YYYY AC 20 - 167A

v **Table Page**  Table 1. 14 CFR 91.176 EFVS Visibility and Visual Reference Requirements ......................... 23 Table 2. Sy stem Operating Phases for Considerations ................................ ................................ 32 Table 3. EFVS Acceptable Methods of Compliance ................................ ................................ A1 - 1 Table 4. Required Level of Safety, 14 CFR part 25 Aircraft ................................ ................... A2 - 1 Table 5. Example EFVS/HUD Functional Hazard Assessment, 14 CFR part 25 Aircraft, ILS Approaches to 100 ft Height Above Touchdown, RVR 12 00 ft ................................ ............... A2 - 3 Table 6. EFVS I Evaluation Matrix ................................ ................................ ......................... A4 - 4 Table 7. EFVS II Evaluation Matrix ................................ ................................ ........................ A5 - 5MM/DD/YYYY AC 20 - 167A

1 **Chapter 1. Introduction**  **1 -**  **1. Purpose**  a. In this advisory

circular (AC), the Fe deral Aviation Administration (FAA) provides guidance on airworthiness approval s of enhanced vision sy stem (EVS), sy nthetic vision sy stem (SVS), combined vision system (CVS), and enhanced flight vision sy stem (EFVS) equipment installation. b. E xisting ACs address flight guidance s ymbology , head - up display s (HUD) and visual display

characteristics (for example, AC 25 - 11A, Elec tronic Flight Deck Display s, AC 25.1329 - 1B, Approval of Flight Guidance S ys tems and AC 23.1311 - 1C Installation of Electronic Display in P art 23 Airplanes ). For a complete listing of related regulations and guidance, refer to Appendix 1. This AC complements existing guidance. c. 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 s ynthetic vision technologies. However, if you use the means described in this AC, yo u must follow it in all aspects. **1 -**  **2. AC Audience**  This AC is for airplane and rotorcraft manufacturers, modifiers, and type certification engineers seeking certification or installation guidance for their visual display s ys tem. Sections 23.773, 25.773 27.773 and 29.773 address vision sy stems using a transparent display surface located in the pilot’s o utside view, such as a head - up - display , head - mounted display , or other equivalent display . Such “vision s ystems” include any EVS, EFVS, SVS, or CVS. **1 -**  **3. Applicability**  a. This AC applies to all applicants for a new ty pe certificate (TC), an amended ty pe certificate (ATC), or a supplemental ty pe certificate (STC), to install enhanced and/or s ynthetic 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, EV S, CVS, or EFVS equipment. b. 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 Sy stems. **1 -**  **4. How to Use This Document**  a. This AC provides methods, procedures, and practices acceptable to the FAA for complying with regulations. EFVS compliance references are listed in Appendix 1. b. This material does not alter regulatory requirements.MM/DD/YYYY AC 20 - 167A

2 c. This AC describes s ys tem performance. d. EFVS safety

standards and sample flight test considerations for EFVS conducted to 100 feet height above runway touchdown zone elevation (EFVS I) and for EFVS operations conducted to touchdown and rollout (EFVS II) are in Appendices 3, 4, and 5, respectivel y. e. A sample flight manual supplement is outlined in Appendix 6. f. Appendix 7 addresses specific installation guidance for EVS and/or SVS on rotorcraft. Appendi x 8 addresses additional part 23 considerations for situation awareness only . g. Definitions and acronym s are in appendix 9. h. Certain material within this AC is from RTCA/DO - 315A, Minimum Aviation Sy stem Performance Standards (MASPS) for Enhanced Vision S ys tem s, Sy nthetic Vision sy stems, Combined Vision Sy stems, and Enhanced Flight vision Sy stems. RTCA/DO - 315 A is copy righted by

RTCA, Inc. and used with permission. Purchase information is in Appendix 9. **1 -**  **5. Cancellation**  AC 20 - 167, Airworthiness Approval of Enhance d Vision System, S ynthetic Vision Sy stem, Combined Vision System, and Enhanced Flight Vision System Equipment, dated June 22, 2010, is canceled.MM/DD/YYYY AC 20 - 167A

3 **Chapter 2. Vision Systems Overview**  **2 -**  **1. Enhanced Vision System**  **s** a. An EVS is an electronic means to provide a display of the forward external scene topograph y 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 infor mation/sy mbology required in 14 CFR 91.176 on a HUD or equivalent display . While Enhanced Vision S ys tems share a similarity with EFVS technology , an EVS does not have to be integrated with a flight guidance s ystem. Furthermore, while an EVS may provide a dditional situation awareness without the additional capabilities provided b y 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: 1. EVS sensor sy stem.

2. D isplay

processor. 3. EVS display . 4. P ilot controls/interface. 5. Mounting .

**V i s i**  **b l e**  E x t e r n a l S cene **Ene r g**  **y** A t m o spher e

S e nsor S e nsor Conver s i o n Sensor S y s t e m

D i s p la y

P r o c e s sor

**P i lo**  **t '**  **s E y**  **e Enhanced**  **F l i g**  **h t V**  **is i o**  **n S y**  **s t e m** 

A i r c r a ft S ta t e D a ta

H e a d - up D i spl ay P r ocessi n g H e a d - u p D i spl a y **Enhanced V i**  **s i on**  **S y s t**  **e m**

EVS D i spl a y P i lo t C ont r o ls

**Figure 1**  **. Enhanced Vision Diagram** (Dashed lines and shading represent individual system boundaries for EVS and EFVS)MM/DD/YYYY AC 20 - 167A

4 **Note:** While an EFVS contains all the elements of an EVS, for the purposes of this AC any discussion of an EVS excludes an EFVS. b. The categories of current EVS sensors are passive or active sensors. 1. Passive Sensors: Scene contrast detected b y pas sive infrared sensors can be much different than that detected b y natural pilot vision. On a dark night, thermal differences of objects, not detectable by the naked eye, will be easil y detected b y many imaging infrared sy stems. However, contrasting color s in visual wavelengths distinguished by the naked eye may not be visible using an imaging infrared s ys tem. Sufficient thermal scene contrast allows shapes and patterns of certain visual references to be recognized in the infrared image b y the pilot. How ever, depending on conditions, they can also appear different to a pilot in the infrared image than they would with normal vision. 2. Active Sensors: Scene contrast by active s ys tems depends on several parameters such as: whether the transmitter is centered on the aircraft velocity vector, display updates rates, latency , range resolution, sensitivity , dy namic 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 s ys tems is their general immunity to weather obscurations.

3. Unlike the pilot's external view, the enhanced vision image can be a mono chrome, 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 non visible energy

source conditions. Gain settings of the sensor, and brightness or contrast settings of the HUD, can significantly affect image quality . Certain sy stem characteristics could create distracting and confusing display arti facts. **2 -**  **2. Synthetic Vision System**  **s** a. Sy

nthetic vision is a computer - generated image of the external scene topograph y from the perspective of the flight deck that is derived from aircraft attitude, high - precision navigation solution, and database of terrain, obs tacles, and relevant cultural features. A s ynthetic vision system is an electronic means to display a sy nthetic vision image of the external scene topograph y to the flight crew. Sy nthetic 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 awareness but cannot be used in lieu of natural vision . The application of synthetic vision s ys tems is through a prim ary 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.

1. Display

(includes interface and installation). 2. Sy stem interface. 3. Database of t errain and obstacle s .MM/DD/YYYY AC 20 - 167A

5 4. 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 sy stem boundaries. External scene visible image is not affected b y SVS.) b. Sy

nthetic vision coordinate referenced databases are usuall y 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 s ynthetic vision display.

**Note** : For information purpose s, there are three DTED levels with the following terrain spacing: 1. DTED Level 0 uses 30 arc second spacing (nominally one kilometer). 2. DTED Level 1 uses 3 arc second spacing (approximately 100 meters). 3. DTED Level 2 uses one arc second spacing (approximately 30 meters).MM/DD/YYYY AC 20 - 167A

6 c. With the exception of terrain and database processing (addressed in chapter 4, paragraph 4 - 3.g.), s ynthetic vision characteristics may include: 1. Display

factors, such as: (a) Conformality . (b) Refresh rate. (c) Field of regard (FOR) . (d) Field of view (FOV) . 2. Display

placement factors, such as: (a) Pilot’s primary

FOV versus pilot’s secondary FOV. (b) Head down display (HDD) versus Head up display (HUD). 3. Terrain presentation factors, such as: (a) Depiction (such as monochromatic, photo - realistic, elevation coloring). (b) Gri dding (presence versus absence, spacing).

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

(d) Resolution. DEM resolution and DTED level. (e) Range indication ( e.g., terrain based range marks, color scheme). 4. Terrai n and cultural f eatures, such as: (a) Rivers, valley s, and mountains. (b) Major landmarks, highway s, and buildings within close proximity to airport. (c) Hue and contrast between terrain and sky.

(d) Man - made obstacles ( e.g., radio towers, bridges, tall buildings) and air port depiction. (e) Airport depiction, including markings ( e.g. , extended runway centerline and numbers, taxiway markings, approach lighting sy stem). (f) Range marks or indications. 5. Functions, such as: (a) Alerting (terrain, obstacles, traffic, and airspace). (b) Declutter. (c) Mode reversion. (d) Image control (FOV, brightness, contrast, registration). 6. Integration of guidance s ymbology (if incorporated), such as:MM/DD/YYYY AC 20 - 167A

7 (a) Guidance cues (flight path vector, flight path angle reference cue, velocity vector, command guidance cues, deviation indicators, and trend indicators). (b) Aircraft reference relative to terrain (indication of relationship between zero pitch line and terrain). (c) Pathway

markings ( “breadcrumbs, ” rectangles) and boundaries, to indicate past or intended future aircraft track. (d) Nav igation information (course lines, fixes, icons, special - use airspace). (e) Unusual attitude recovery. (f) Crosswind indication (and image display based on cross - track). **2 -**  **3. Combined Vision System**  **s** a. The CVS concept involves a combination of SVS and EVS or EFVS . Some e xamples of a CVS include database - driven s ynthetic 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 s ys tem 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 sy nthetic to enhanced vision, either for SVS picture validation or displaying the runway environment. b. For combined vision s ys tems applicants are expected to meet applicable performance criteria for each incorporated sy stem. **2 -**  **4. Enhanced Flight Vision System**  **s** a. An EFVS, as defined in 14 CFR 1.1, is “...an installe d aircraft sy stem which uses an electronic means to provide a display of the forward external scene topography (the applicable natural or manmade features of a place or region especiall y in a way to show their relative positions and elevation) through the use of imaging sensors, such as forward - looking infrared, millimeter wave radiometry , millimeter wave radar, or low - light level image intensification. The EFVS sensor imagery

and required aircraft flight information and flight symbology is displayed on a head - up display , or an equivalent display , so that the imagery and s ymbology

is clearl y visible to the pilot flying in his or her normal position with the line of vision looking forward along the flight path. An EFVS includes the display element, sensors, computers and power supplies, indications, and controls.” During an instrument approach, the enhanced vision image is intended to enhance the pilot's ability to detect and identify the visual references required b y the regulations. b. An EFVS requires a real - time imaging sensor providing demonstrated vision performance in low visibility conditions and a level of safety suitable for the proposed operational procedure. This allows the required visual references to become visible in the image before they

are v isible naturally

out - the - window. Depending on atmospheric conditions and the strength of energy

emitted and/or reflected from the scene, the pilot can use the imageryMM/DD/YYYY AC 20 - 167A

8 produced b y an EFVS to see these visual references on the display better than the pilot can see them through the window without enhanced vision. Currently approved enhanced flight vision sy stems use passive infrared sensor technology . However, an active or passive sensor, as described in chapter 2, paragraph 2 - 1.b., could be used provided i t meets the performance criteria in this AC. c. The basic elements of an installed EFVS are defined in 14 CFR 91.17 6 , and are listed below, with the EFVS diagram in Figure 1 . Specific s ys tem criteria for EFVS s ys tems can be found in Section 4 of this AC.

1. An electronic means to provide a display of the forward external scene topograph y (the natural or manmade features of a place or region especially in a way to show their relative positions and elevation) through the use of imaging sensors, such as a forward l ooking infrared, millimeter wave radiometry , millimeter wave radar, and low - light level image intensifying; 2. The EFVS sensor imagery and aircraft flight s ymbology ( i.e., at least airspeed, vertical speed, aircraft attitude, heading, altitude, command guidan ce as appropriate for the approach to be flown, path deviation indications, flight path vector, and flight path angle reference cue) are presented on a head - up display , or an equivalent display , so they are clearl y visible to the pilot flying in his or her normal position and line of vision and looking forward along the flight path, to include:

(a) The displayed EFVS imagery , attitude s ymbology , flight path vector, and flight path angle reference cue, and other cues, which are referenced to this imagery and ext ernal scene topograph y, must be presented so they are aligned with and scaled to the external view; (b) The flight path angle reference cue must be displayed with the pitch scale, selectable b y the pilot to the desired descent angle for the approach, and suita ble for monitoring the vertical flight path of the aircraft on approaches without vertical guidance; and

(c) The displayed imagery and aircraft flight sy

mbology do not adversel y obscure the pilot's outside view or field of view through the cockpit window.

3. The EFVS includes the display element, sensors, computers and power supplies, indications, and controls. It may receive inputs from an airborne navigation sy stem or flight guidance s ys tem; and

4. The display

characteristics and dy

namics are suitable for manual c ontrol of the aircraft. 5. Depending on the EFVS intended function , installations designed to be eligible for EFVS II operations also need a flare cue and radio altitude. Refer to the performance criteria in paragraph 4 - 5 of this AC. d. Enhanced flight vision technology can use either stroke or raster technology . 1. Stroke sy

mbology illuminates a small fraction of the total display area of the HUD, leaving much of that area free of reflected light that could interfere with the pilot's view out the window through the display .MM/DD/YYYY AC 20 - 167A

9 2. The raster infrared image is in the center of the pilot's regulated "pilot compartment view." A "raster" image is comprised of a set of horizontal lines continuously sweeping across the display to form a picture by

modulating their intensity ( luminance). It should be free of interference, distortion, and glare that would adversel y affect the performance of the pilot's normal performance and workload. A raster image can be more difficult for the pilot to see through than stroke - written s ymbols also displayed on the HUD. Unlike stroke sy mbology , the raster image illuminates, to some degree, most of the total display area of the HUD with much greater potential interference with the pilot compartment view. It is sufficient for the pilot to see around the raster image, but the outside scene must be visible through it. e. Unlike the pilot's external view, the enhanced flight vision image is 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 flight vision image and the level of enhanced flight vision sensor performance could depend significantl y on the atmospheric and external light source conditions. Gain settings of the sensor, and brightne ss or contrast settings of the HUD, can significantly affect image quality . Certain sy stem characteristics could create distracting and confusing display artifacts. Finally, this is a sensor - based s ystem that is intended to provide a conformal perspectiv e. Refer to Figure 1 for a diagram of the sy stem. f. Depending on the intended operational function of the EFVS, airworthiness approval will be designated as an EFVS I or EFVS II as described below. Depending on the airworthiness approval being sought b y the applicant, additional basic equipage may be required. Those additional requirements can be found in paragraph 4 - 5 of this AC.

1. EFVS I

– The installed EFVS has been demonstrated to meet the criteria for AC 20 - 167A for EFVS Ito be used for instrument app roach operations from DA/DH or MDA to 100 HAT.

2. EFVS II

– The installed EFVS has been demonstrated to meet the criteria for AC 20 - 167A for EFVS II to be used for instrument approach and landing operations that rel y on sufficient visibility

conditions to e nable unaided rollout and to mitigate for loss of EFVS function. An EFVS that meets the certification criteria for EFVS II also meets the certification criteria for EFVS I. Flight Standards currently authorizes EFVS II operations to be conducted on a straight - in instrument approach procedure from DA/DH to touchdown to visibilities as low as a Runway Visual Range (RVR) of 1000 feet, depending on what was demonstrated during certification flight test. g. Although the European Aviation Safety Agency (EASA) uses the term “EVS” as equivalent to the FAA “EFVS,” do not confuse an EFVS with an Enhanced Vision System (EVS). 1. Unlike with EFVS, an aircraft with EVS does not necessarily provide the additional flight information or sy mbology required by 14 CFR 91.176 . An EVS is not required to use a HUD, and may

not be able to present the image and flight s ymbology in the same scale and alignment as the outside view. An EVS can provide situation awareness to the pilot, but does not meet the regulatory requirements of 14 C FR 91.176. An EVS cannot be used as a means to determine enhanced flight visibility or to identify

the required visual references in order to gain operational credit and descend below the DA/DH or MDA.MM/DD/YYYY AC 20 - 167A

10 2. For the primary

display , the regulations also make provision for an equivalent display . Specifically , 14 CFR 91.176(a),(1),(i),(B) states that the EFVS sensor imagery and aircraft flight sy

mbology must be presented “ on a head - up display , or an equivalent display , on which the imagery and s ymbology

is clearly visible to the pilot flying in his or her normal position with the line of vision looking forward along the flight path.” An equivalent display must be some typ e of head - up presentation of the required information. A head - down display does not meet th e regulatory requirement. For the monitoring display, see paragraph 4 - 5.b.(1) of this AC.MM/DD/YYYY AC 20 - 167A

11 **Chapter 3. Airworthiness Package Contents 3**  **- 1.**  **Airworthiness Package** The applicant is responsible for the following contents in the airworthiness package (for the purpo se of this AC). This AC specificall y addresses SVS with attitude displayed on the primary flight display

(PFD), EVS/SVS/CVS with a head down display other than a PFD (such as a navigation display

or multifunction display), EVS image displayed on a head up display , and an EFVS. a. Intended function: Information on intended function can be found in section 3 - 2. b. General operation: Information on the general operations and specific performance criteria can be found in Chapter 4. c. Performance criteria and evalu ation plan for the respective s ys tem . Performance evaluation is addressed in Chapter 6 with sample test considerations found in the appendices of this document, and d. Installation considerations: Information regarding installation considerations can be found in Chapter 5 of this document. **Note** : Depending on the s ys tem (for example, EVS, SVS, CVS, or EFVS), the appropriate guidance will depend on the respective sy stem. **3 -**  **2. Intended Function**  **.** a. EVS, SVS, or CVS: Define the intended functions of your EVS, SVS or CV S. In clude what features yo u will display and the criticality

of pilot decision - making using the display features. Define additional intended functions (for example, terrain alerting) according to AC 25 - 11A and 14 CFR 2X.1301. b. EFVS: Clearl y define the i ntended function of yo ur EFVS (EFVS I, II, or III). This must include its use to assess enhanced flight visibility and to visuall y acquire the visual references required to operate below the DA/DH or MDA as specified in 14 CFR 91.176 (a) and (b), 121.651, 125.381 and 135.225, and the criticality of pilot decision - making based on what is visible using the EFVS display . The purpose of the EFVS is to provide a visual advantage over the pilot’s out - the - window view using natural vision. In low visibility conditions, the “enhanced flight visibility” should exceed the “flight visibility” and the required visual references should become visible to the pilot at a longer distance with an EFVS than they would out - the - window using natural vision. Visual advantage us ing an EFVS must be demonstrated before descending below DA/DH or MDA because this is the point in an instrument approach procedure where the operating rules permit an EFVS to be used in lieu of natural vision for operational benefit. **Note 1** : The EFVS is not intended to change the technologies or procedures already used to safel y fl y the aircraft down to the MDA/MDH or DA/DH. The EFVS sensor provides a visual advantage over the pilot's out - the - window view. In low visibility conditions, the "enhanced flight visibility " should exceed the "flight visibility" and the required visual references should become visible to the pilot at a longer distance in the EFVS than out - the - window. The EFVSMM/DD/YYYY AC 20 - 167A

12 complements other instrument approach equipment by providing a means for the pilot to see (with the EFVS) the required visual references that might otherwise not be visible **Note 2** : While the goal of EFVS is to exceed the natural flight visibility in the majority of cases/weather conditions, there may be meteorological conditions where the EFVS does not provide a significant advantage.MM/DD/YYYY AC 20 - 167A

13 **Chapter 4 System Criteria**  **4 -**  **1. EVS or SVS (or CVS when EVS and SVS combined)** 
**– General.**  a. EVS/SVS/CVS Primary Display s. EVS, SVS, or CVS functionality can be superimposed on the electronic flight instrument sy stem (EFIS), for example the primary flight display (PFD) as installed in the flight deck. In this configuration example, the EVS, SVS, or CVS image can be merged into the sky /ground shading of the attitude direction indicator. In addition to the traditional head down display PFD, this ty

pe of superimposed display could also be associated with a HUD or equivalent display sy stem using EVS, SVS, or CVS capabilities. Maneuvering the aircraft during any phase of flight (taxi, approach, landing rol lout, etc.) shall not be predicated on EVS imagery . b. EVS/SVS/CVS Secondary Display s. EVS, SVS, or CVS functionality can be selected on a multi - function display (MFD) or navigation display (ND) as one of many stand alone ty pe formats available in the flight deck. For example, an EVS, SVS, or CVS image can be one selection on the MFD, while an electrical sy noptic could be another selection on the same MFD. c. EVS, SVS, or CVS installed on side - mounted display s: While similar in concept to the MFD, side - mounted display s s ys tems are, in general, limited due to the nature of the installation constraints of these devices. Side - mounted display s of EVS technologies can present unique certification challenges such as alignment or positioning concerns relating to the display installation. (See AC 120 - 76B, Guidelines for Certification, Airworthiness, and Operational Use of Electronic Flight Bag, for specific applications.) d. The intended function for any installation of EVS/SVS/CVS must be clearly defined (appropriate 14 CFR 2X.1301), and the design and installation safety levels must be appropriate for the stated intended function. Although normally associated with use during flight, utilization of EVS display during ground operations should not be used if sensor proximity to the taxiway

surface causes a distraction. 1. The intended function should be reasonable considering the actual functionality

of the installation . 2. Operating limitations should be proposed to the FAA by the applicant . Operating limitations must be clearl y defined and stated in the aircraft’s flight manual supplement in line with the intended function.

3. An EVS must not be used for flight guidance or navigation . An EVS cannot be used in lieu of natural vision to descend below DA/DH or MDA under 91.176, 121. 651, 125.381 or 135.225 regardless of whether it is on a HUD, or on a head down display . e. Although EVS/SVS/CVS installations do not provide additional operational credit , the proposed s ys tem (EVS, SVS, and/or CVS) :

1. Should h ave a means to automatically or manually control display brightness. 2. Must not degrade presentation of essential flight information. In other words, the pilot’s ability

to see and use the required primary flight display

information such asMM/DD/YYYY AC 20 - 167A

14 primary attitude, airspeed, altitude, and command bars/command guidance must not be hindered or compromised b y the EVS/SVS/CVS image.

3. If the vision sy stem uses a head - up display or the equivalent, then it may not distort the pilot compartment view, provide a distorted (i.e. non - conformal) view of the exte rnal scene, or interfere with the pilot’s ability to safel y perform any maneuvers within the operating limitations of the aircraft, including tax i ing, takeoff, approach, and landing. See paragraph 4 - 1.f.2 of this section .

4. Not adversel y affect any other installed aircraft s ystem. 5. Perform its intended function in each aircraft environment where s ys tem approval is desired. For example, if the sy stem is intended to perform in (or after exposure to) known icing conditions, a means can be required to keep the EVS sensor window clear of ice accumulation. 6. Display the mode of operation (EVS, SVS, or CVS) to the pilot/crew. Consideration should be given to recording the EVS/SVS/CVS display status in a flight data recorder or some form of nonvolatile memory .

7. Not h ave undesirable display characteristics (for example, jitter, jerky motion, and excessive delay s). f. Display

Implementation. EVS/SVS/CVS can be incorporated into differing display types installed in the cockpit. AC 25 - 11A and AC 23.1311 - 1C, Installation of Electronic Display in Part 23 Airplanes, provide more information on electronic displays. The display is subject to all applicable primary flight information rules and guidance for the category of aircraft. 1. Primary Flight Display

(PFD). Primary

display s are cockpit display s used to provide information needed to guide and control the aircraft and provide the aircraft altitude, attitude, and airspeed indications. EVS/SVS/CVS can be implemented on the primary Head Down Display

(HDD) in 14 CFR part 23 and 2 5 aircraft. Refer to AC 27 - 1B and AC 29 - 2C for guidance on installation on rotorcraft. The following criteria appl y to EVS/SVS/CVS implemented on a PFD.

(a) The image, or loss thereof, must not adversel y affect the PFD functionality . (b) Align the displayed imag e with the aircraft ’s inertial axis, physical axis or as appropriate for the intended function. The alignment can be variable and/or “phase of flight” dependent. The relationship be tween the image and the aircraft ’s heading angle, pitch angle, roll angle , and track angle should generally align with the trajectory

of the aircraft, should be recognizable b y the flight crew , and not be misleading. For example, if two display s show EVS, SVS, or CVS information, or a combination (EVS on one and SVS on another), the orientation of the displays should be the same. Alignment of imagery presented on the PFD should be consistent with the real world and appropriate for the s ys tem’s intended function accounting for possible aircraft attitudes, turbulence, and wind e ffects.

(c) Scale and align all spatially referenced s ymbology

within each axis with the imagery

so as not to present any

misleading information to the pilot.MM/DD/YYYY AC 20 - 167A

15 (d) The Field of Regard (FOR) can be variable, but must be designed to ensure the displayed image is not distracting or misleading and does not adversel y affect crew performance and workload. (reference 14 CFR §§ 2X.771 and 2X.1309.)

(e) The display should not impede a clearl y visible zero pitch reference line, distinct in visual appearance relative to any possible terrain, obstacle, or cultural feature display

appearance. **Note** : Consider including a flight path vector or velocity vector to show the pilot the aircraft’s trajectory relative to displayed terrain. (f) Per 14 CFR 2x.771 and 2x.773, pilot tasks must not b e degraded by the displayed imagery. Depending on the intended function of the display information, the imagery must not provide the pilot with misleading information regarding detection, accurate identification, and avoidance of terrain, obstacles, and o ther flight hazards.

2. Head - Up Display . EVS/SVS/CVS can be implemented on a HUD, HDD or equivalent. The following criteria apply to EVS/SVS/CVS implemented on a HUD display : (a) A design with EVS/SVS/CVS imagery displayed on a HUD must account for the pilot co mpartment view requirements found in 14 CFR 23.773, 25.773, 27.773, and 29.773, including validation that the display of EVS imagery

does not conflict with the pilot compartment view. The following tasks associated with the use of the pilot’s view must no t be degraded below the level of safety that existed without the EVS: (i) Detection, accurate identification and maneuvering, as necessary , to avoid traffic, terrain, obstacles, and other hazards of flight. (ii) Accurate identification and utilization of visual ref erences required for every

task relevant to the phase of flight.

**Note** : Although normally associated with use during flight, utilization of video imagery on the HUD during ground operations should not be considered if sensor proximity

to the taxiway

surfac e causes a distraction. (b) The safety and performance of the pilot tasks associated with the use of the pilot compartment view must not be degraded b y the display of imagery

on the HUD. Per 14 CFR 2X.773, pilot tasks which must not be degraded b y the imagery include: (i) Detection, accurate identification, and maneuvering, as necessary , to avoid traffic, terrain, obstacles, and other hazards of flight. (ii) Accurate identification and utilization of visual references required for every

task relevant to the phase of fl ight. (c) Imagery

on the HUD must be conformal with the real world and appropriate for the s ys tem’s intended function accounting for possible aircraft attitudes, turbulence, and wind effects.

(d) Society

of Automotive Engineers (SAE) International design standards for HUD s ymbology , optical elements and video imagery are also prescribed with SAE Aerospace Standard (AS) 8055, Minimum Performance Standard for Airborne Head Up Display (HUD), dated March 1999, SAE Aerospace Recommended Practice (ARP) 5288, Transport Category Airplane Head Up Display (HUD) Sy stems, dated May 2001, and SAE ARP 5287,MM/DD/YYYY AC 20 - 167A

16 Optical Measurement Procedures for Airborne Head Up Display (HUD), dated March 1999. Apply specific design standards for resolution and line width, luminance and contrast rat io, chromaticity , and grayscale.

3. Secondary display s. EVS/SVS/CVS can be implemented with ego - centric “inside aircraft” views or exocentric “outside aircraft” viewpoints on head down display s. This includes installed EFBs or MFD. The following criteria a ppl y to EVS/SVS/CVS implemented on secondary

display s:(a) The orientation and perspective of the EVS/SVS/CVS view should be clear to the pilot. (b) If PFD information is displayed, it should meet PFD integrity requirements and availability criteria .

(c) EVS/SVS/CVS i mage, or loss thereof, must not adversel y affect other approved display

functionality

(such as navigation display s). **Note** : Generall y, the orientation of the secondary display should be the same as the primary

display to decrease the possibility of pilot c onfusion. **4 -**  **2. EVS Specific**  **Criteria .**  a. An EVS requires a real - time imaging sensor and display , providing improved vision performance. These sy stems do not qualify for additional operational credit over and above what is already approved, and are installed on a non - interference basis. b. EVS installations must meet the following criteria : 1. The EVS depiction must be crew de - selectable (if on the primary display , the pilot should be able to easily and quickl y declutter the EVS or remove sensor image). For an EVS image displayed on a HUD, provide a control which permits the pilot flying to deactivate and reactivate the display of the EVS image on demand without removing the pilot’s hands from the primary

flight controls (yoke or equivalent) or thrust control. 2. The display mode (status of EVS), either through crew de - selection or as a result of a failure, should be clearly indicated or obvious to the crew. 3. The display

and sensor FOR should be sufficient for the intended functions. 4. SAE design standards for EVS sy mbology , op tical elements and video imagery are also prescribed in SAE AS 8055, SAE ARP 5288 and SAE ARP 5287. Apply the specific design standards for resolution and line width, luminance and contrast ratio, chromaticity , and grayscale.

5. Consider the following criteria for display characteristics for the EVS design, regardless of the display type: (a) For part 25 airplanes, apply all display

characteristics listed in AC 25 - 11A. For part 23 airplanes, appl y all display characteristics listed in AC 23.1311 - 1. For other ai rcraft without corresponding criteria, the guidance in AC 25 - 11A or AC 23.1311 - 1 serves as recommended guidance.MM/DD/YYYY AC 20 - 167A

17 (b) The display

should not have undesirable display characteristics (such as blooming, “burlap,” and running water).

6. Image c haracteristics . (a) On a HD D , the relationship of the display FOR to the actual field of view should be suitable for the pilot to smoothly transition from the HDD to the out - the window real world view or HUD.

(b) The image data should be refreshed at 15 Hz or better. (c) The image latency s hould be less than 100 milliseconds where the latency is measured from the image source time of applicability to the display

of the image. **Note** : EVS refresh rate, when used in direct aircraft or power plant manual control tasks (such as attitude, engine p arameters, etc.), equal to, or greater than 15 Hz has been found to be acceptable. Any lag introduced b y the display s ys tem should be consistent with the aircraft control task associated with that parameter. In particular, display s ys tem lag (including th e sensor) for attitude which does not exceed a first order equivalent time constant o f 100 milliseconds for aircraft with conventional control sy stem response is generall y acceptable.

7. For display

on a HUD, the minimum system should provide a control of the EVS display

contrast/brightness which is effective in dy namically changing background (ambient) lighting. In addition, the minimum system must:

, (a) prevent distractions to the pilot, (b) P revent impairment of the pilot’s ability to detect and identify visual references, (c) Prevent masking of flight hazards,

(d) Prevent d egrad ation of task performance or safety. 8. When EFVS is incorporated on the primary display , the EVS - based primary display must be clear and unambiguous when recovery from unusual attitudes is require d. An accurate, easy , quick - glance interpretation of attitude should be possible for all unusual attitude situations and other “non - normal” maneuvers sufficient to permit the pilot to recognize the unusual attitude and initiate a recovery within one secon d. We recommend you use chevrons, pointers, and/or permanent ground - sky horizon on all attitude indications to perform effective manual recovery from unusual attitudes. (For part 25 aircraft, refer to AC 25 - 11A. For part 23 aircraft, refer to appendix 8 .) Alway s have some indication of both sky and ground visible on the PFD for use in initiating unusual attitude recovery . **4 -**  **3. SVS Specific**  **Criteria .**  a. Sy

nthetic Vision Sy stems require a terrain and obstacle database, a precision navigation position, display , and height, attitude, and heading/track inputs. The design and installation safety

levels should be appropriate for the sy stem’s intended function. AC 25 - 11A and AC 23.1311 - 1 provide additional general display guidance. b. Image characteristics:MM/DD/YYYY AC 20 - 167A

18 1. Failure or de - selection of the sy nthetic vision depiction should be obvious to the crew. 2. The display can depict the scene from the pilot’s view looking through the front window (egocentric) or from outside the aircraft (exocentric). However, if implemented on a prim ary display , then the display should depict the scene from the pilot’s perspective looking through the front window.

3. The Field of Regard (FOR) should be appropriate for the s ys tem’s intended function and account for possible aircraft attitudes, turbulence, and wind effects (for example, to orient the line of sight according to heading and not to track). Sy nthetic vision scene compression can result from FOR selections or display size limitations. Regardless, prominent topographical features should be easi ly identified and must be correlated with the actual external scene. 4. Id entify dominant topographical features present in the SVS image in the outside view. D ominant topographical features present in the outside view should also be identifiable in the SVS image.

5. Terrain: (a) A potential terrain or obstacle conflict should be obvious to the pilot, and must not conflict with TAWS or HTAWS requirements. One mechanism for making such conflicts obvious on a primary display is an earth - based flight path vector. For guidance regarding alerts, use AC 23.1311 - 1 or AC 25. 1322 - 1 .

(b) Displayed topographical features should not intersect guidance provided to the pilot to fly a published approach path. Terrain and 3 - space position resolution should be accurate enough that top ographical features should not intersect published approach paths. (c) Threatening terrain, close enough to generate a terrain warning alert, should appear above the artificial horizon zero pitch reference line if it is higher than the aircraft altitude.

6. SVS - b ased primary display s must be clear and unambiguous when recovery from unusual attitudes is required. An accurate, eas y, quick - glance interpretation of attitude should be possible for all unusual attitude situations and other “non - normal” maneuvers suffic ient to permit the pilot to recognize the unusual attitude and initiate a recovery within one second. We recommend you use chevrons, pointers, and/or permanent ground - sky horizon on all attitude indications to perform effective manual recovery from unusual attitudes. (For part 25 aircraft, refer to AC 25 - 11A . For part 23 aircraft, refer to appendix 7.) Alway s have some indication of both sky

and ground visible on the PFD for use in initiating unusual attitude recovery . SVS display s used as an attitude indicator require an egocentric orientation.

7. The relationship of the display FOR to the actual field of view should be suitable for the pilot to smoothly transition from the head - down display to the head - up, out - the window real features.

8. The terrain depiction should include large bodies of water and rivers. Differentiation between water and sky depictions should be clearl y distinguishable.

9. The pilot’s view should not be depicted below the earth’s surface.MM/DD/YYYY AC 20 - 167A

19 10. The image should be updated at 15 Hz or better and function smoothly during all expected maneuvering reasonable for the class and type of aircraft.

11. The image latency for a PFD or HUD should be consistent with the image guidance in AC 25 - 11A or that necessary for expected maneuvering reasonable for the clas s and ty pe of aircraft. For other display s in the flight deck, a larger lag can be acceptable subject to the intended function.

12. Undesirable display characteristics should be minimized (for example, jitter, jerky

motion, and excessive delay s). 13. Range: (a) The s cene range should be the natural horizon for both egocentric and exocentric display s. For s ys tems intended for use in approach, missed approach, take - off, and departure operations, the scene range should be whichever is less of the following: natural horizon, 40 nautical miles, or 10 minutes at maximum cruise speed.

(b) The scene range from the eye position to the terrain horizon must not be misleading and must be appropriate to the intended function. The intent is to prevent misleading information due to a SVS range limitation to the horizon that could lead to crew confusion at a critical phase of flight. At some airports the missed approach can take the aircraft on a course towards mountains. Pilots need to see that the mountains will be a factor in their missed approach long before they get to the runway . Thus, it is not acceptable for an approach to appear as if it is over flat terrain until short final when the mountains in the distance finall y start appearing on the PFD.

14. Although every

possible scenario cannot be described, the crew should be able to perceive relative distances to prominent topographical features. For example, the pilot should be able to identify an immediate terrain threat versus a distant terrain conflict.

15. All obstacles taller than 200 feet above ground level should be displayed . These obstacles must be displayed conformall y on the synthetic vision image.

**Note** : Obstacle display

consideration should be given to reducing clutter when objects pose no threat, yet not suddenl y appear at low altitudes during periods of task saturation. c. Position Source. The horizontal position source used for the SVS display should at least meet the criteria for TAWS or HTAWS. The horizontal position source must not provide contradictory

indications of h orizontal terrain clearance. Additional guidance for the horizontal position source can be necessary , depending on the intended functions of the SVS. TAWS guidance is contained in AC 25 - 23 and AC 23 - 18. HTAWS guidance is contained in AC 27 - 1B and 29 - 2C. 1. The sy nthetic vision display

must not conflict with either the terrain warning or terrain awareness functions (for example, TAWS or HTAWS).

2. Any

aircraft incorporating SVS from the egocentric perspective should also provide a TAWS or HTAWS or terrain warni ng s ys tem (refer to appendix 8 for specifics on a terrain warning s ys tem). If terrain alerts and cautions are depicted on the SVS, they must be consistent across all display s in the cockpit when terrain threats are identified. In other words, terrain dat abase sources should be consistent.MM/DD/YYYY AC 20 - 167A

20 d. Altitude Source. The altitude source used for the SVS display should meet the criteria for TAWS or HTAWS installations, including the need to account for cold temperature errors which could place the aircraft closer to the surface than the altimeter indicates. The altitude source should be consistent with that used for the onboard terrain awareness and alerting sy stem on the aircraft and must not provide contradictory indications of vertical terrain clearance. Addition al criteria for the altitude source can be necessary , depending on the intended functions of the SVS. TAWS guidance is contained in AC 25 - 23 and AC 23 - 18. HTAWS guidance is contained in AC 27 - 1B, AC 29 - 2C, and TSO - C194. e. Attitude Source. The attitude source must not conflict with attitude information or integrity criteria provided by the primary

flight display . f. Heading/Track Source. The heading/track source must not conflict with heading/track information provided b y the navigation display. g. Terrain and O bstacle Database. 1. Terrain and obstacle database processing. The terrain and obstacle database, along with any other database used to create the SVS image should be compliant to RTCA/DO - 200A, as applicable to the intended function. The minimum terrain dat abase resolution and accuracy

must be consistent with the intended function, and should comply with the resolution and accuracy listed in TSO - C151, appendix 1, section 6.3, or for helicopters, TSO C194. (a) Position accuracy , s ymbology , and topographical infor mation should be consistent with each other.

(b) Runway

elevations must be accurate at the approach ends and not just at the airport center.

2. Obst acle d atabase. The obstacle database should include all available phy sical hazards greater than 200 feet above gro und level, not just terrain. The sy stem should neither disregard nor corrupt obstacles available in the database greater than 200 feet above ground level. Obstacles displayed should be those deemed hazardous to the flight (or phase of flight). The applic ant should provide procedures in the Instructions for Continued Airworthiness to ensure the most current obstacle database is installed.

**Note** : It is difficult to apply one altitude value across a wide range of aircraft performance, from rotary wing to high performance fixed wing. Generally , above 5,000 ft AGL, most obstacles are not tall enough to be hazardous. However, in the airport terminal area, even obstacles less than 1,000 ft AGL can be hazardous.

3. Navigation Database. The navigation database used by SVS for runway and airport information should be consistent with that used by other s ys tems in the aircraft (for example, flight management sy stems). The applicant should provide procedures to document database currency

in the Instructions for Continu ed Airworthiness. 4. Features. If flight path guidance features are provided by the SVS, they should complement (or correspond with) approved navigation sy stem guidance.

5. Head - Up Display s. Providing complete guidance for s ynthetic vision sy stems is complicat ed by the many design variables available to manufacturers. Since s yntheticMM/DD/YYYY AC 20 - 167A

21 vision displays can share many characteristics with a HUD, applicants should use HUD display guidance where appropriate.

6. Terrain display . If the intended function is “terrain awar eness,” then “awareness” is consistent with the actual terrain. The display may not match the terrain perfectly , but the display

should provide a reasonable representation of the terrain in a manner that does not misrepresent the threat posed by the terrai n. The display , while possibl y resolution or field - ofview limited, may

still adequatel y portray

terrain awareness. The pilot should be aware of less than a 1:1 ratio of depiction. Display suitability

must be matched against intended function. **4 -**  **4. CVS Specific**  **Criteria .**  a. CVS requires a real - time imaging sensor and display that provides demonstrated vision performance for its intended function. They also require a terrain and obstacle database and a precision navigation position for the sy nthetic portion of the display . The design assurance levels should be appropriate for the s ys tem’s intended function. The following criteria appl y to CVS installations:

1. CVS should meet the respective criteria of the EVS and SVS implementations.

2. The EVS and SVS depic tions should be conformal with each other. 3. Fusion of EVS and SVS should require the images to be aligned within 5 milliradian (mrad) laterally and verticall y at the boresight of the display . Therefore, blended EVS and SVS images should not cause confusion to the flight crew. Image discrepancies between EVS and SVS due to failure conditions should be obvious to the crew.

**Note** : It is difficult to define every implementation in order to determine what is “significant.” However, the applicant is expected to reduce discrepancies to as near - zero as possible. The final determination will occur during flight test. b. The CVS should meet the detailed performance criteria for EVS and SVS specified in paragraphs 4 - 2 and 4 - 3 of this chapter. **4 -**  **5. EFVS** 
**– General an**  **d Specific Criteria**  **.** a. EFVS criteria would meet EVS criteria . However, there are additional EFVS general and specific criteria needed to be eligible for operational credit, as follows:

1. Mitigate s ys tem failures more frequent than extremely improbable which p roduce effects the pil ot (or the aircraft itself) cannot safel y handle. Design the aircraft s ys tems so the entire fault probability is kept to an acceptable level, and complies with 14 CFR part 2x.1309 regulations.

2. The sensor image, combined with the required aircraft state and position reference s ymbology , is presented to the flight crew on the HUD , or an equivalent display , so that they are clearl y visible to the pilot flying in his or her normal position and line of vision looking forward along the flight. For HUD operations, the pilot flying views the EFVS sensor and sy mbolic information that is properly aligned and registered to enable a one - to - one (conformal) overlay

with the actual external scene.MM/DD/YYYY AC 20 - 167A

22 3. The HUD and displayed FOR should be sufficient for the EFVS information to be displayed conformally over the range of anticipated aircraft attitudes, aircraft configurations, and environmental (for example, wind) conditions. The aircraft state and position reference data is presented in the form of sy mbolo gy overlaying the image presentation. The flight instrument data on the HUD must include:

(a) Airspeed; (b) Vertical speed; (c) Aircraft attitude; (d) Heading; (e) Altitude; (f) Command guidance as appropriate for the approach to be flown (g) Path deviation indications (h) Flight path v ector; and (i) Flight path angle reference cue. 4. For an EFVS II intended for landing and rollout (i.e. from DA/DH through touchdown and roll - out at not less than 1000ft RVR , the following specified aircraft flight information, in addition to that noted above in 4 - 5.a.3, must also be displayed:

(a) Radio altitude, and (b) Flare prompt or flare guidance for achieving acceptable touchdown performance, as required by paragraph 6 - 2. 5. The minimum system should include a control of EFVS display contrast/brightness which is effe ctive in dyn amically changing background (ambient) lighting, prevents distractions to the pilot, prevents impairment of the pilot’s ability to detect and identify visual references, prevents masking of flight hazards, or otherwise degrades task performance or safety. If automatic control for image brightness is not provided, it should be shown that manual setting of image brightness meets the above criteria and does not cause excessive workload.

6. The EFVS display controls should be visible to, and within re ach of, the pilot flying from any

normal seated position. The position and movement of the controls should not lead to inadvertent operation. The EFVS controls, except those located on the pilot’s control wheel, should be adequately illuminated for all n ormal background lighting conditions, and should not create any objectionable reflections on the HUD or other flight instruments. Unless fixed illumination of the EFVS controls is shown to be satisfactory under all lighting conditions for which approval i s sought, there must be a readily accessible control provided that permits the pilot to immediately

deactivate or reactivate the display of the EFVS image on a HUD. This control must be on demand without removing the pilot’s hands from the primary flight controls (yoke or equivalent) and thrust control.

7. Base the approach path situation information references and command guidance information on the navaids dictated b y the straight - in instrument approach procedure in use.MM/DD/YYYY AC 20 - 167A

23 8. Under FAA regulations, as defined in 14 CFR 91.176 , upon reaching the decision altitude/decision height (DA/DH) or minimum descent altitude/minimum descent height (MDA/MDH), the required visual references presented in Table 1 must be distinctly visible and identifiable to the pilot. **Table 1**  **. 14 CFR 91.176**  **EFVS Visibility and Visual Reference Requirements** From the authorized DA/DH to 100 feet height above touchdown zone elevation of the runway

of intended landing, the approach light sy stem (if installed) or both the runway threshold and the touchdown zone are distinctly visible and identifiable to the pilot using an EFVS. (A) The runway

threshold must be identified using at least one of the following visual references - (1) The beginning of the runway landing surface; (2) The threshold lights; or (3) The runway

end identifier lights. (B) The touchdown zone must be identified using at least one of the following visual references - (1) The runway

touchdown zone landing surface; (2) The touchdown zone lights; (3) The touchdown zone markings; or (4) The runway

lights At 100 feet height above touchdown zone elevation of the runway of intended landing the approach can be continued while still relying on the EFVS imagery provided that at least one of the following visual references must be visible and identifia

ble to the pilot using an EFVS. (A) The runway

threshold; (B) The lights of markings of the threshold (C) The runway

touchdown zone landing surface; or (D) The lights or markings of the touchdown zone. 9. In terms of sensor design criteria , sensor performance criteria can be quantified in terms of the range of the enhanced flight visibility when low visibility

conditions exist. The visual references of the runway environment must be seen by the sensor at operationall y relevant distances.

10. The minimum detection EFVS range ( figure 3, below) can be derived b y using an assumed minimum distance of the aircraft at the nominal Category I(200 ft) decision altitude before which the EFVS should image the runway threshold. On a 3 degree glide slope, the horizontal distance from the aircraft to the runway threshold is approximately 2816 feet (3816 feet from the precision touchdown zone markers). Use this range as a minimum requirement. These values do not take into account pilot decision time or actual atmospheric conditions, the use of non - precision approaches which can require greater distances , or the use of approaches with higher DAs, DHs, or MDAs .MM/DD/YYYY AC 20 - 167A

24 **Figure 3**  **. Minimum Detection Range** 11. The EFVS imagery displayed on the HUD must account for the pilot compartment view requirements found in 14 CFR 25.773, 23.773, 27.773, and 29.773, including validation that the display of imagery does not conflict with the pilot compartment view. The display of EFVS sensor imagery should be on a s ystem that compensates for th e interference caused b y the provided imagery provides an undistorted and conformal view of the external scene, provides a means to deactivate the display and does not restrict the pilot from performing specific maneuvers. The following tasks associated w ith the use of the pilot’s view must not be degraded below the level of safety that existed without the video imagery :

(a) Detection, accurate identification and maneuvering, as necessary , to avoid traffic, terrain, obstacles, and other hazards of flight.

(b) Accurate identification and utilization of visual references required for every task relevant to the phase of flight.

**Note** : Although normally associated with use during flight, utilization of video imagery

on the HUD during ground operations should be conside red if sensor proximity to the taxiway

surface causes a distraction. b. EFVS General S ys tem Criteria . 1. The EFVS image must be compatible with the FOV and head motion box of a HUD designed against SAE ARP 5288 (transport category head - up display

(HUD) s ys tems). The HUD and EFVS FOR must provide a conformal image with the visual scene over the range of aircraft attitudes and wind conditions for each mode of operation.

(a) A display

that provides the pilot monitoring with EFVS sensor imagery is not required for EFVS I operations. However, for EFVS II operations, when a minimum flightcrew of more than one pilot is required for the conduct of the operation, the aircraft must be equipped with an operable display that provides the pilot monitoring with EFVS sensor imagery. (b) The display must be located within the maximum primary field of view of the pilot monitoring and any s ymbology displayed must not adversely obscure the sensor imagery of the runway

environment.MM/DD/YYYY AC 20 - 167A

25 2. EFVS display

criteria must meet the airworthiness certific ation requirements in 14 CFR parts 21, 23, 25, 27, and 29 (as applicable). Specifically , the EFVS sy stem installation and operations must demonstrate compliance with the requirements listed in Appendix 1, EFVS compliance checklist. These requirements are specific to EFVS and are in addition to all other requirements applicable to the HUD and the basic avionics installation.

3. The current FAA guidelines for head - up display s apply with respect to EFVS. These criteria include well - established military as well as civil aviation standards for HUDs as defined in MIL - STD - 1787C, Aircraft Display S ymbology , and AC 25 - 11A. SAE design standards for HUD sy mbology , optical elements and video imagery are also prescribed within SAE AS 8055, SAE ARP 5288 and SAE ARP 5287. Apply specific design standards for image size, resolution and line width, luminance and contrast ratio, chromaticity and gray scale. 4. The EFVS image, when superimposed on the HUD sy mbology and when used in combination with other aircraft sy stems, must mee t the criteria below. The EFVS image and installation must : (a) B e suitable for and successfully perform its intended function. (b) A llow the accurate identification and utilization of visual references, using both EFVS and natural vision as appropriate.

(c) H ave acc eptable display characteristics to accomplish the intended function. (d) P rovide a means to allow the pilot the pilot using the display to immediately

deactivate and reactivate the vision sy stem imagery , on demand, without removing the pilot’s hands from the primary flight controls (yoke or equivalent) or thrust controls. (e) N ot degrade the presentation of essential flight information on the HUD. (f) N ot be misleading and should not cause confusion or any significant increase in pilot workload.

(g) B e aligned and scaled to the external scene, and should include the effect of near distance parallax.

(h) N ot cause unacceptable interference with the safe and effective use of the pilot compartment view.

(i) N ot significantl y alter the color perception of the external scene to preclude the pilot’s performance of any required maneuvers . (j) A llow the pilot to recognize misaligned or non - conformal conditions. 5. Additionally , the EFVS installation and image s hould have an effective control of EFVS display

brightness without causing excessive pilot workload and not cause adverse ph ys iological effects such as fatigue or eyestrain.

6. A HUD modified to display EFVS must continue to meet the conditions of the original approval and be adequate for the intended function, in all phases of flight in whic hMM/DD/YYYY AC 20 - 167A

26 the EFVS is used. An accurate, eas y, quick - gl ance interpretation of attitude should be possible for all unusual attitude situations and other “non - normal” maneuvers to permit the pilot to recognize the unusual attitude and initiate recovery within one s econd. We recommend you use chevrons, pointers, and/or permanent ground - sky horizon on all attitude indications to perform effective manual recovery from unusual attitudes. Refer to AC 25 - 11A for guidance on electronic flight deck display s.

7. 14 CFR 91.17 6 requires that the EFVS display a flight path vector (FPV) and flight path angle reference cue (FPARC) on the HUD or equivalent display . The following criteria apply

to these s ymbols: (a) The position and motion of the FPV should correspond to the aircraft’s earth referenced flight path vector.

(b) The dy

namic response of FPV should follow pilot control inputs. Refer to AE ARP 5589 for dy namic response guidance. (c) The display

of the FPARC should be suitable for monitoring the vertical flight path of the aircraft.

(d) T he Sy stem should provide the pilot a means to select the desired descent angle that is represented b y the FPARC.

8. The display

of attitude s ymbology , FPV, FPARC, and other visual elements which are earth - referenced, must be aligned with and scaled (i.e., con formal) to the external view. 9. The EFVS display of imagery , flight information and flight s ymbology should be a suitable visual reference for the pilot during the manual performance of any maneuvers within the operating limitations of the aircraft, including taxiing, takeoff, approach, landing and rollout. c. EFVS Detailed S ys tem Criteria . 1. The performance of EFVS imaging s ys tems does not solely depend upon sy stem design, but also depends upon the target scene characteristics such as the runway , light structures , electromagnetic radiation and atmospheric conditions.

2. Since the purpose of the EFVS sensor is to provide a visual advantage over the pilot’s out - the - window view, the design should include a general performance anal ys is. This analy sis includes calculated performance, which indicates the viability of the sy stem to meet the proposed intended function, specificall y including the calculated performance of the sensor operation within the range of the environment proposed.

3. Likewise, since the purpose of the EFV S sensor is to provide a visual advantage over the pilot’s out - the - window view, the general performance analy sis should include the calculated transmission of electromagnetic energy in the visible spectrum and other frequencies that can assess length of tr ansmission over a path with generalized extinction coefficients at a given wavelength.

**Note:** Examples of acceptable sensor models are MODTRAN and LOWTRAN which can be used to estimate the performance of infrared s ys tems. Other models (FASCODE) for radar sy stems may

be used for these typ es of sensors and provide a basic measure of signalMM/DD/YYYY AC 20 - 167A

27 attenuation helpful in assessing performance and viability for the functions defined in 14 CFR 91.17 6 . 4. Minimum system performance. Integration of the major components inc ludes the installed sensor, its interconnections with the sensor display processor, the display device, pilot interface, and aircraft mechanical interface, which can include the radome for the sensor. (a) Latency . EFVS latency should be no greater than 100 mi lliseconds (msec). A longer lag time can be found satisfactory, provided it is demonstrated not to be misleading or confusing to the pilot. L atency , as a general requirement, should not be discernible to the pilot and should not affect control performanc e or increase pilot workload. EFVS latency

causes, at best, undesirable oscillatory image motion in response to pilot control inputs or turbulence. At worst, EFVS latency may cause pilot - induced oscillations if the pilot attempts to use the EFVS for acti ve control during precision tracking tasks or maneuvers in the absence of other visual cues.

(b) EFVS FOR. The minimum fixed FOR should be 20 degrees horizontal and 15 degrees vertical. In applications where the FOR is centered on the flight path vector the minimum vertical FOR should be 5 degrees (± 2.5 degrees) and 20 degrees horizontal. (i) The requirement for a minimum EFVS FOR should not only consider the HUD FOV (i.e., how large of an area displayed), but also the area over which this area subtends (i.e., what is shown on the conformal display). The FOR portrayed on the HUD is established b y three primary determinants: (1) HUD and EFVS sensor Field - Of - View; (2) Orientation of the HUD with respect to the aircraft frame of reference (for example, boresight and proximity to pilot’s eye); and (3) Orientation (for example, attitude) of the aircraft. (ii) SAE ARP 5288 states, “ The design of the HUD installation should provide adequate display fields - of - view in order for the HUD to function correctly in all anticipated flight attit

udes, aircraft configurations, or environmental conditions such as crosswinds for which it is approved. Limitations should be clearl y spec ified in the AFM if the HUD cannot be used throughout the full aircraft flight envelope.” A quantitative EFVS FOR re quirement was established as minimum design criteria to be qualitativel y checked during certification flight test for sufficiency in meeting its intended function. The EFVS FOR requirement resulted after consideration of the minimum field of regard criteria for various aircraft attitudes and wind conditions using a critical altitude of 200 ft height above touchdown zone elevation for EFVS visibility . (iii) A variable FOR is permissible assuming a slewable sensor (i.e., variable field - of

- regard), centered on the Flight Path Vector, with a minimum +/ - 2.5 deg about the flight path v ector to allow for momentary flight path perturbations and to allow sufficient fore/aft view of the required visual references.

(c) Off

- axis rejection. A source in object space greater than 1 degree outside the FOV should not result in any perceptible point or edge like image within the field ofMM/DD/YYYY AC 20 - 167A

28 view. The EFVS should preclude off - axis information from folding into the primary FOR imagery , creating the potential for misleading or distracting imagery .

(d) Jitter. When viewed from the HUD eye reference point, the displayed EFVS image jitter amplitude should be less than 0.6 mrad. Jitter for this use is defined in SAE ARP 5288. This implies the EFVS and HUD cannot exhibit jitter greater than that of the HUD itself. (e) Flicker. Flicker is brightness variations at frequency above 0.25 Hz per SAE ARP 5288. The minimum standard for flicker should meet the criteria of SAE ARP 5288. Flicker can cause mild fatigue and reduced crew efficiency. This requirement implies the EFVS and HUD cannot exhibit flicker greater than that of the HUD itself.

(f) Image artifacts. The EFVS must not exhibit any objectionable noise, local disturbances or an artifact that hazardously detracts from the use of the s ys tem. The EF VS design must minimize display characteristics or artifacts (for example, internal s ys tem noise, “burlap” overlay , or running water droplets) which obscure the desired image of the scene, impair the pilot's ability

to detect and identify

visual references , mask flight hazards, distract the pilot, or otherwise degrade task performance or safety.

(g) Image c onformality . The accuracy of the integrated EFVS and HUD image should not result in a greater than 5 mrad display error at the center of the display at a range of 2000 ft (100 ft altitude on a 3 degree glideslope). In accordance with SAE ARP 5288, the total HUD s ys tem display accuracy erro r as measured from the HUD eye reference p oint, should be less than 5.0 mrad at the HUD boresight, with increasing error allowable toward the outer edges of the HUD. Errors away from the bore sight should be as defined in SAE ARP 5288. The primary

EFVS error components include the installation misalignment of the EFVS sensor from aircraft/HUD boresight and sensor parallax. A range parameter is used in the EFVS conformability

requirement to account for the error component associated with parallax. There is no error allowed for the EFVS sensor, since it is assumed any error can be electronicall y compensated during installati on. With EFVS operations, the aircraft is flown essentially irrespective of the EFVS/HUD dynamic error, to the MDA or DA. From this point to 100 ft height above touchdown zone elevation, the EFVS conformality error introduces error in the pilot’s ability to track along the extended centerline/vertical glide path as the pilot fl ies the flight path vector and glidepath reference l ine toward the EFVS image of the runway .

(h) Sensor/sensor p rocessor. (i) Dy

namic range. The minimum required dy namic range for passive EFVS should be 48 db. For active EFVS, side lobes should be 23 db below the main beam, and 40 db dynamic range plus sensitivity time control (STC). (ii) Sensor image c alibration. Visible image calibrations and other built - in tests that cannot be achieved with in a total latency of 100 milliseconds should occur onl y on either pilot command or be coordinated by aircraft data to only occur in non critical phases of flight. If other than normal imagery is displayed during the non - uniformity correction (NUC) or oth er built - in tests, the image must be removed from the pilot’s display . This requirement prohibits excessive times to complete maintenance or calibration functions which would remove or degrade the EFVS imagery during critical phases of flight, unless the pilot commands the action (with full knowledge of effect based on training and experience).MM/DD/YYYY AC 20 - 167A

29 Abnormal imagery

should be removed from the display to eliminate the potential for any misleading information. (iii) Sensor resolution. As a minimum, the sensor resolut ion performance requirement shall adequatel y resolve (for pilot identification) the runway threshold and the touchdown zone to enable the intended function. For example, a radar- based EFVS should resolve a 60 ft wide runway from 200 ft height above touchd own zone elevation with a ty pical 3 - degree glide slope. The required sensor resolution was established by providing this resolution at a minimum range, allowing the pilot to continue the descent below DA or MDA. (These values do not take into account pil ot decision time or actual atmospheri c conditions, or the use of non - precision approaches which may require greater distances.) A 60 ft wide runway was chosen as the ICAO minimum runway width to support an instrument approach procedure. (iv) Passive sensor optical distortion. Optical distortion should be 5 percent or less across the minimal FOR as defined in paragraph 4 - 5.c.(4)(b) and no greater than 8 percent outside the minimal FOR. (v) Sensor s ensitivity . In this context, the EFVS sensor sensitivity should be at least a noise equivalent temperature difference (NETD) of 50 o mK tested at an appropriate ambient temperature, for passive EFVS sy stems or - 20dB sm/sm (square meter/square meter) surface at R max from 200 ft height above touchdown zone elevation with a typical 3 - degree glide slope for active EFVS sy stems. Passive sensors for different visible or short - wave infrared sources can require very sensitive detectors, as specified by low noise equivalent powers. (vi) Failure m essages. EFVS malfunctions detected by the sy stem, and which can adversel y affect the normal operation of the EFVS, should be annunciated. As a minimum, specific in - flight failure message(s) for sensor failure and frozen image must be displayed to the flight crew. (vii) Blooming. The sensor should i ncorporate features to minimize blooming, which can create an unusable or objectionable image. Objectionable blooming is defined as the condition that obscures the required visual cues defined in Figure 3. Blooming to the extent the required visual refer ences are no longer distinctly visible and identifiable is unacceptable. (viii) Image persistence. The image persistence time constant should be less than 100 milliseconds. However, burn - in or longer image persistence caused b y high energy

sources (for example, the sun saturating the infrared sensor elements), should be removed from the image to comply with paragraph 4 - 5, c.(4)(f), Im age artifacts, by a secondary on - demand process (for example, the NUC process). (ix) Dead p ixels. Dead pixels or sensor elements replac ed b y a “bad pixel” replacement algorithm should be limited to 1 percent average of the total display area, with no cluster greater than 0.02 percent within the minimum FOR. A small number of disparate dead pixel elements can be effectivel y replaced b y im age processing but eventually , the algorithms will degrade the image quality and accuracy due to the sheer number and closel yspaced location of the element. (x) Parallax. The effects of parallax caused b y lateral, vertical, and longitudinal offset of the sen sor from the pilots’ design eye points cannot impede the EFVSMM/DD/YYYY AC 20 - 167A

30 from performing its intended function, as evaluated during flight test. Parallax sh ould not result in significant performance differences in safety- related performance parameters (e.g., flare h eight; sink rate, touchdown location; groundspeed during landing, exit and taxi) between EFVS operations and visual operations in the same aircraft .MM/DD/YYYY AC 20 - 167A

31 **Chapter 5. Systems Installation Considerations 5**  **- 1.**  **EVS/SVS/CVS Installations Considerations** a. EVS/SVS/CVS Pilot Controls. 1. The EVS/SVS/CVS display controls should be visible to, and within reach of, the pilot flying from any normal seated position. The position and movement of the controls should not lead to inadvertent operation.

2. The EVS/SVS/CVS controls, except those located on the pilot’s control wheel, must be adequately illuminated for all normal background lighting conditions and must not create any objectionable reflections on other flight instruments.

3. There must be a means to modulate illumination unless fix ed illumination of the EVS/SVS/CVS controls is shown to be satisfactory under all lighting conditions. b. EVS/SVS/CVS Preventive Maintenance. Use manufacturer data for preventive maintenance (for example, Instructions for Continued Airworthiness, per 14 CFR 21.50 and FAA Order 8110.54) , or other methods, techniques, and practices acceptable to the Administrator . c. EVS/SVS/CVS Built - InTest (BIT). Provide a BIT capability that, at a minimum, limits the exposure time to latent failures consistent with the exposure limits in the sy stem safety assessment. d. The electrical s ys tem must be able to furnish the required power at the proper voltage for the EVS/SVS/CVS . e. EVS/SVS/CVS System Safety Design Criteria. The overall safety requirement of the aircraft is based on in stalled equipment. A complete fault hazard analysis (FHA) and s ys tem safety analysis (SSA) should be conducted to identify failure modes and classify the hazard levels. To meet the safety criteria, the s ys tem design will be demonstrated through anal ys is and engineering tests to preclude failures that can cause hazardousl y misleading information to be presented to the pilot or crew, or which can otherwise subsequently cause an unsafe condition. The following guidelines do not preclude the results of a full SSA. The results of an SSA found acceptable to the FAA should prevail. f. EVS/SVS/CVS Required Safety L evel. 1. The airworthiness standard under which approval is sought can impact criticality (for example, 14 CFR part 23, 25, 27, or 29). Recognizing that eac h implementation and integration of each installation can be unique, the applicant should perform a thorough FHA, SSA, and Failure Mode and Effects Anal ys is (FMEA). An y failure or malfunction that could cause misleading enhanced vision, sy nthetic vision , or combined vision depiction should be immediately

annunciated and the imagery depiction should be removed. 2. The applicant must perform a safety assessment as required b y the regulations , based on the proposed installation for the given aircraft and intende d function for each phase of flight. Information presented to a pilot on a PFD is considered truth unless flagged otherwise. Therefore, presenting hazardously misleading information to the pilot must be avoided. One example of hazardously misleading inf

ormation ( HMI ) would be the aircraft levelMM/DD/YYYY AC 20 - 167A

32 ramifications of a “frozen EVS/SVS/CVS display” that is undetected b y the flight crew. In general, the sensor or s ys tem performance and level of design must be consistent with the safety assessment . 3. Once the safe ty assessment has been completed, for any hazard or failure classification greater than Major, a fault tree analy sis (FTA) should be evaluated using the guidance found in the FAA sy stem safety advisory circular that is applicable to the installation (e.g., AC 23.1309 - 1E, AC 25.1309 - 1A, AC 27 - 1B (containing AC 27.1309) and 29 - 2C ). The FTA should include the display monitor, power supply , IR camera and sensors, cable, status annunciations, and other components that affect the top - level events. The FTA shoul d not include pilot detection and corrective actions, which have no fixed probability value. 4. The variables influencing the outcome of the failure condition and its classification vary

between 14 CFR parts 23, 25, 27, and 29. In general, the sensor or s ys t em performance and level of design shall be consistent with the SSA. Table 2 provides sample sy stem operating phases for consideration. The results of an SSA found acceptable to the FAA should prevail. **Table 2**  **. System Operating P hases for Considerations**  **GROUND TAKEOFF**  **IN -**  **FLIGHT LANDING**  (1)Taxi (2) Maintenance (1) Takeoff Roll Prior

to V 1 , (2) Takeoff Roll After V 1 , (3) Takeoff After V R to 200’ (4) Rejected Takeoff (1) Climb

(2) Gear Up, (3) Cruise (4) Descent, (5) Gear Down, (6) Approach 200’ to 0’ (7) Go Around (1) Touchdown &

Rollout (2) Taxi

5. The normal operation of the EVS/SVS/CVS may not adversel y affect, or be adversel y affected b y o ther normall y operating aircraft systems. The criticality of the EVS/SVS/CVS system’s functi on to display imagery , including the potential to display hazardously

misleading information, should be assessed according to the applicable 14 CFR part 2x.1309, AC 25 - 11A chapter 4, and AC 2x.1309, Sy stem Safety Analysis and Assessment for Part 23/25 Airp lanes. Likewise, the hazard effects of any malfunction of the EVS/SVS/ CVS that could adversely

affect interfaced equipment or associated s ys tems should be determined and assessed according to the applicable 14 CFR 2x.1309, AC 25 - 11A chapter 4, and AC 2x. 1309. As applicable, similar criteria is found in SAE ARP 4754, and ARP 4761. g. EVS/SVS/CVS Environmental Specifications. The EVS/SVS/CVS should meet all specified operating conditions and should provide required operating performance, life and reliability when operating within the aircraft and subsy stem flight envelope as specified in RTCA/DO - 160G (as revised) Environmental Conditions and Test Procedures for Airborne Equipment. These criteria must also include the high - intensity radiated fields (HIRF),MM/DD/YYYY AC 20 - 167A

33 ele ctromagnetic interference (EMI) and lightning requirements as specified in the certification basis of the aircraft to be installed. A lightning zone anal ys is and assessment of the effects of lightning strike on the camera in conjunction with other cockpit equipment should be accomplished. The instal lation must protect the aircraft against catastrophic effects from lightning. **5 -**  **2. EFVS Installation Considerations**  a. EFVS Annunciations. Any modes of EFVS operation should be annunciated on the flight deck and visib le to the crew. The modes of the EFVS operation must be made available to the flight data recorder as required. b. EFVS Display . 1. Display

r esolution of the HUD. Since the sensor can be active or passive, the EFVS display should adequatel y resolve a 60 ft. wi de runway from 200 ft. height above touchdown zone elevation with a ty pical 3 - degree glide slope. The pilot needs to be able to detect and accuratel y identify the visual references in the image.

2. Imagery

and s y mbology display . Imagery

must not degrade pre sentation of essential flight information on the HUD. The pilot's ability to see and use the required primary flight display

information such as primary attitude, airspeed, altitude, and command bars must not be hindered or compromised by the EFVS image o n the HUD. 3. Flare C ue. An EFVS II must have a flare cue because it is intended to enable landing in low visibility . The f lare c ue, whether a f

lare p rompt or f

lare guidance, should demonstrate compliance to the landing criteria found in paragraph 6 - 2. For some aircraft, f lare guidance may

be required because a f

lare p rompt is not sufficient. (a) Flare Prompt. A flare prompt is intended to notify the pilot that it is time to initiate the flare maneuver, but does not guide the pilot’s manual pitch control inputs . The pilot must use situational information (e.g., altitude, vertical rate, attitude, FPV, perspective view of the runway) from the EFVS to judge the magnitude and rate of manual pitch control inputs. The appearance and dy namic behavior of the f

lare p ro mpt should be distinguishable from command guidance. The f lare prompt should appear timel y and conspicuously to the pilot using the HUD so that the flare maneuver will be neither too early nor and within the touchdown zone as described in paragraph 6 - 2 of this document.

(b) Flare Guidance. EFVS II operations require a flare cue - either flare prompt or flare guidance, as appropriate, for achieving acceptable touchdown performance. Each applicant for a ty

pe design approval must demonstrate acceptable touchdown performance for their particular EFVS implementation using either flare prompt or flare guidance. This provides the pilot with additional information to conduct the flare maneuver during conditions of low visibility

ty picall y encountered during EFVS operations to touchdown and rollout. The flare cue should be demonstrated to meet the landing criteria found in paragraph 6 - 2. c. EFVS Maintenance **.** Instructions for Continued Airworthiness are to be furnished after final design approval (reference 14 CFR 21.50 and FAA Order 8110.54). d. EFVS Built - in Test (BIT). Provide a BIT capability (or equivalent means) that, at a minimum, limits the exposure time to latent failures in support of the s ys tem safety assessment. e. EFVS Sy stem Safety Design Criteria.MM/DD/YYYY AC 20 - 167A

34 1. The overall le vel of safety of the aircraft is based on installed equipment. A complete s ys tem safety analysis (SSA) should be conducted to identify failure modes and classify the hazard levels. To meet the safety criteria, the s ys tem design should preclude failures that can cause hazardously misleading information (HMI) to be presented to the pilot or crew, or which can otherwise subsequently cause an unsafe condition. For example, HMI could include information providing attitude, altitude, and distance cues as outsi de terrain imagery . This demonstration should be accomplished through analy sis and engineering tests.

(a) The EFVS s ys tem must perform its intended function for each operation and phase of flight that it would use.

(b) The normal operation of the EFVS cannot adversely affect, or be adve rsel y affected b y other aircraft sy stems. Annunciate detected malfunctions of the EFVS sy stem and remove the malfunctioning display elements. 2. Appendix 2, Table 4 lists the categories of s ys tems and failure probabilities to meet the safety criteria in 14 CFR part 25 airplanes (AC 25.1309 - 1A). For 14 CFR part 23 aircraft, similar information can be found in 14 CFR 23.1309 and AC 23.1309. The relationship among airplane classes, probabilities, severity of failure conditions and sof tware development assurance levels is found in AC 23.1309 - 1E. Section 2x.1309, as applicable, and the following additional guidance helps assess the criticality of the EFVS display , including the potential to display

HMI: (a) AC 25 - 11A (chapter 4), (b) AC 23.131 1 - 1, and (c) AC 27 - 1B and AC 29 - 2C, as appropriate for the installation. 3. Validate all alleviating flightcrew actions that are considered in the EFVS safety analysis during testing either for incorporation in the AFM/AFMS or RFM/RFMS limitation section, procedures section or for inclusion in ty pe - specific training. f. EFVS I Required Level of Safety . 1. When you are designing an EFVS I , establish safety design goals for airworthiness approval. The safety criteria for each phase of flight, including approach and landi ng s ys tems are defined in terms of accuracy , continuity , availability , and integrity. FAA design guidance provides criteria to determine the overall required level of safety for the aircraft, in any mode of flight, for any

combination of failures which can cause an unsafe condition to be fully assessed and categorized. This includes the probability of the pilot(s) to cope with these failures. The hazard level for any aircraft system depends on the ability of the pilot(s) to cope with failures. For failur es where the SSA assumes a particular pilot intervention to limit the hazard effects, fo r example from Catastrophic or H azardous to Major or Minor, the applicant must show that pilot indeed can be relied on to perform that intervention. For example, the p ilot might be assumed to detect a sy stem error because of other display s or view out the window. It must be demonstrated that pilots will indeed detect the error in a timely fashion and not be hazardously

misled. The demonstration must validate the propo sed hazard classification, as applicable (see Appendix 2, Table 4 ).MM/DD/YYYY AC 20 - 167A

35 2. The applicant should demonstrate a satisfactory safety (failure and performance) level which must not be less than the safety level required for non - EFVS I based precision and non - precisio n approaches with decision altitudes of 200 ft. or above. In showing compliance, probabilities cannot be factored b y the portion of approaches which are made using EFVS. Consideration, however, can be given to the EFVS I critical flight time, such as fro m the highest DH that can be expected for an EFVS I based approach to 100 ft. above the TDZE.

3. The design assurance levels (DALs) are directl y linked to the specific intended use and to the specific EFVS I installation as an integrated part of the cockpit f light information sy stem.

4. There are failure modes within the EFVS I which determine that software and hardware DALs should be RTCA/DO - 178B or level C (major) as a minimum. However, dependent upon the mitigations you utilize, stemming from the specific EFV S and cockpit installations, the DAL s can be higher than this minimum level.

5. The aircraft level functional hazard anal ys is (FHA) you prepare should determine whether the minimum required DALs of level C are adequate for your specific installation. An example FHA is shown in Appendix 2, but is a model case only and cannot be applied to any specific aircraft without independent analysis.

6. A s ys tem safety analysis (SSA) of an EFVS I was performed for a certification on an in strument flight capable aircraft for straight - in non - precision and precision approach and landing operation per 14 CFR 91.17 6(b) . This SSA is shown in appendix 2 for example and general guidance onl y. The applicant must provide the applicable 14 CFR 23, 25, 27, and 29.1309 anal ys is.

7. Conduc t a safety anal ys is to show the EFVS I sy stem meets all the integri ty criteria for the aircraft , HUD and EFVS. Demonstrate s ys tem and subsy stem malfunctions which are not shown to be extremely improbable as appropriate in a simulation or in flight. The m alfunction annunciation and fault detection schemes must achieve the determined level of safety . g. EFVS II Required Level of Safety. 1. The applicant is must demonstrate a satisfactory level of safety (failure and performance) appropriate to the operations bein g addressed, but with the visual segment primarily accomplished by

the use of an EFVS II rather than natural vision. 2. To achieve the required safety level , the minimum baseline safety levels required for the installed EFVS II equipment regardless of visibil ity , should be dependent on the demonstrated performance.

3. An aircraft level Functional Hazard Anal ys is (FHA) and S ys tem Safety Assessment (SSA) sh ould be prepared b y the applicant to assess the hazard level associated with sy stem failure conditions and to determine the minimum required software and hardware Design Assurance Levels (DAL) based on the applicant’s specific installation. Mitigating s ys tem design features include redundancy , independent guidance display , s ys tem monitoring, pilot in the loop, pi lot not flying, etc. In no case should the DAL be less than DAL C.

4. The minimum required safety level for an EFVS II s ys tem (EFVS to touchdown in visibilities not less than RVR 1000 feet) is based on the assumption the minimumMM/DD/YYYY AC 20 - 167A

36 visibility limitation of 1000 feet provides the flight crew a means to verify that the aircraft is safel y approaching the runway for EFVS II - based landing, or, if not, to initiate a timely go around. This provides additional integrity to the operation. Depending on the applicant’s d esign, it may

be possible that the minimum visibility can also compensate for loss of EFVS imagery , such that the pilot can use the remaining sy mbolic flight information on the HUD and the external view to safely land. S ys tem evaluation should consider EF VS II failure modes and whether the pilot can safely land and rollout with available natural vision plus whatever remains of EFVS II . A Safe landing should not be assumed with only available natural vision after total loss of EFVS II (i.e., s ymbology and image). 5. In showing compliance with these safety criteria , do not factor probabilities of EFVS II failure conditions b y the fraction of approaches which require EFVS II . Also, do not factor probabilities of EFVS II failure conditions by a statistical distribution of visibility conditions. The exposure time used for EFVS II failure calculations should be the elapsed time from descent below the highest expected DA/DH for the EFVS II based approach to completion of rollout to a safe taxi speed. h. Sy stem Safety Assessment **.** 1. An aircraft level Functional Hazard Anal ys is (FHA) sh ould be prepared b y the applicant to assess the hazard level associated with sy stem failure conditions and to determine that the minimum required software and hardware Design Assurance Level (DALs) is appropriate to the applicant’s specific intended function .

2. The DALs are directly linked to the specific intended use and to the specific EFVS installation as an integrated part of the cockpit flight information sy stem. The availability

and integrity

of situational and flight path information from sources other than the EFVS image and the ability of the pilot monitoring to monitor the operation should be considered when assessing the appropriate hazard levels for the EFVS.

3. The applicant sh ould pro vide a Sy stem Safety Assessment (SSA) for compliance to the applicable to 14 CFR 2X.1309 regulation.

4. The safety assessment sh ould show that the applicant’s specific installation meets all the integri ty criteria for the aircraft sy stems, HUD and EFVS.

5. The a

pplicant may

need to demonstrate by

flight test or simulation, combinations of EFVS malfunctions which are not shown to be extremely improbable (10 E - 9) be demonstrated.

6. Any

malfunction fault detection and annunciation schemes must satisfy the required lev els of safety and must perform their intended functions. 7. All aircraft configurations to be certified must be addressed. i. EFVS Fail Safe Features. The normal operation of the EFVS may not adversely affect, or be adversely

affected by

other normall y operatin g aircraft sy stems. Malfunctions of the EFVS which could cause display of misleading information must be annunciated and the misleading information removed. The criticality of the EFVS’s function to display imagery , including the potential to display haz ardousl y misleading information, should be assessed according to 14 CFR 25.1309, AC 25 - 11A chapter 4, and AC 25.1309 - 1A. L ikewise, the hazard effects of any malfunction of the EFVS that could adversel y affect interfaced equipment orMM/DD/YYYY AC 20 - 167A

37 associated s ys tems sho uld be determined and assessed according to 14 CFR 25.1309, AC 25 - 11A chapter 4, and AC 25.1309 - 1A. As applicable, similar criteria is found in 14 CFR 23.1309, and AC 23.1309 - 1C, 14 CFR 27.1309 and AC 27 - 1B and 14 CFR 29.1309 and AC 29 - 2C. This requirement must be met through a sy stem safety assessment and documented via FTA, failure mode and effects anal ys is (FMEA), and failure mode and effects anal ys is substantiation (FMEA Substantiation), or equivalent safety documentation. j. EFVS Environmental Specifications. The EFVS must meet all specified operating criteria and must provide required operating performance, life and reliability when operating within the aircraft and subs ys tem flight envelope as specified in RTCA/DO - 160F (as revised) Environmental Condi tions and Test Procedures for Airborne Equipment, or future versions. These criteria must also include the HIRF, EMI and lightning requirements as specified in the certification basis of the aircraft to be installed. **5 -**  **3. HIRF Considerations for All Installat** **ions (EVS, SVS, CVS, and EFVS).** a. The immunity

of critical avionics/electronics and electrical sy stems to High Intensity Radiated Fields (HIRF) must be established. Critical functions are those whose failure would contribute to or cause a failure condition that would prevent the continued safe flight and landing of the aircraft . Refer to AC 20 - 158, The Certification of Aircraft Electrical and Electronic S ys tems for Operation in the High - Intensity Radiated Fields (HIRF) Environment, for compatibility

with other sy stems. b. New avionics/electronics and electrical s ys tems performing critical functions should be designed and installed to preclude component damage and interruption of function due to both the direct and indirect effects of HIRF. For these s ys tems, c ompliance must be shown to 14 CFR 23.1308(a), 25.13l7(a), 27.13l7(a), or 29.1317(a), as appropriate. **Note** : AC 20 - 158 (paragraph 6) provides guidance on Approaches to Compliance.MM/DD/YYYY AC 20 - 167A

38 **Chapter 6. Performance Evaluation 6**  **- 1.**  **EVS/SVS/EFVS Performance Demonstration** a. Th e performance demonstration, establishing aircraft sy stem compliance with applicable FAA regulations, ty picall y includes bench testing, flight testing, data collection, and data reduction to show that the proposed performance criteria can be met. Minimal performance standards necessitate an evaluation of the s ys tem used during anticipated operational scenarios. The performance evaluations should therefore include demonstrations of taxi, take - off, approach, missed approaches, failure conditions, cross wind conditions, and approaches into specific airports as appropriate for the sy stem’s intended function. For EFVS, the applicant should demonstrate performance at the lateral and vertical limits for the ty pe of approach (for example, precision, non - precision , and approach with vertical guidance) credit being sought. Appendix 4 provides sample EFVS flight test considerations. b. No specific test procedures are cited, as it is recognized that alternative methods can be used. Alternate procedures can be used if i t can be demonstrated that they provide all the information needed to show compliance with the applicable regulations . Sy stem performance tests as they

relate to operational capability are the most important tests. Subsy stem tests are used as subsy stems are added during sy stem buildup to ensure appropriate subsy stem performance as it relates to overall sy stem performance. c. The applicant should u se any of these four general verification methods (refer to AC 25.1329 - 1B , AC 23.1309, AC 27 - 1B or AC29 - 2C as app licable )..

1. Analy sis. D emonstrate compliance using an engineering analy sis. 2. Flight Test. D emonstrate compliance using an appropriate aircraft (in the air or on the ground).

3. Laboratory

Test. D emonstrate compliance using an engineering bench representative of the final EVS/SVS/CVS/EFVS sy stem being certified.

4. Simulation. D emonstrate compliance using a flight simulator. d. Specify

the individual verification methods that you use in the certification plan. Confirm the appropriate certification office agrees wi th your plan before yo u begin. For extensions, features, and design decisions not explicitly specified in this AC, conduct human factors evaluations. Conduct these evaluations through bench, simulation, or flight testing. e. Verify

both the installed sy stem and the individual sy stem components meet the EVS/SVS/CVS/EFVS criteria described in Chapter 4. f. Demonstrate the s ys tem meets performance criteria by flight test and other appropriate means, which can include use of a flight simulator. An example of a flight test program for EFVS is described in appendix 4 in this AC. The flight test program assumes that the guidance s ys tem utilized to sati sfactorily position the aircraft at the DA/DH or MDA has been separatel y tested and shown to fully perform its intended function. Testing and data collection to demonstrate this is not part of this document. g. Airframe and equipment manufacturer based tests or anal ys is , as applicable , should be developed and conducted to validate the detailed system criteria . No spec ific testMM/DD/YYYY AC 20 - 167A

39 procedures are cited because alternative methods can be used. You can use alternate procedures if you can demonstrate that they provide all the required information. Sy stem performance tests as they relate to operational capability are the most important tests. Subsy stem tests are used as subsy stems are added during s ys tem buildup to ensure appropriate subs ys tem performance as it relates to overall sy stem performance. h. Conduct an evaluation of the sy stem used during anticipated operational scenarios. i. For EFVS testing: If the aircraft has all elements of 14 CFR 91.176(a)( 1 ) and 91.176(b)( 1 ), as appropriate for EFVS operations to touchdown and roll - out or EFVS operations to 100 feet, and as documented in the Ty pe Inspection Acceptance, it can proce ed with the number of approaches per the approved test plan. Use of a build - up approach should facilitate the process obtaining a waiver to conduct flight test of an uncertified system. **6 -**  **2. Performance Demonstration of EFVS**  **II .**  a. Where appropriate for the performance demonstration, the non - visual conditions can be achieved either b y natural obscuration or by use of a visibility limiting device in front of the pilot. Caution should be used if the applicant chooses to use a visibility limiting device for sy stem performance demonstrations . Visibility- limiting devices may not adequatel y simulate low visibility

conditions for all EFVS II landing performance demonstrations because of the unrealistically

good external visibility

outside the HUD FOV and the unrealist ic EFVS II image performance in good atmospheric conditions. b. The workload associated with the use of EFVS II for approach, landing and rollout must be considered when showing compliance with 14 CFR 23/25/27/29.1523 . c. Final a

pproach course offsets greater th an 3 degrees will be subject to additional flight test evaluation. The maximum allowable final approach course offset is established by flight test. These tests sh ould include the factors related to the offset, such as HUD/EFVS field of view, crosswinds, and the maximum drift angle for a conformal flight path vector. d. The EFVS II image, with superimposed flight s ymbology , must not mislead, distract or jeopardize the safety of the landing and rollout. Performance shall be demonstrated to be equivalent or b etter to that normally achieved in visual operations for the specific aircraft for all performance parameters measured. e. Benchmark data establishing equivalence to normal visual operations with the specific aircraft would not normally be necessary . However , if flight test results show deviations for the standard criteria listed above, then benchmark data might be used to establish the equivalence of EFVS II operations to normal visual op erations for that specific airc raft . f. Without requiring exceptional pilo t skill, alerting, strength or workload, the image/s ymbology should provide the visual cues for the pilot to perform the following items.

1. Speed control within +10/ - 5 knots of the approach speed, whether manually controlled or with auto - throttle, as propose d by the applicant, up to the point where the throttles are retarded for landing.

2. A smooth transition through flare to landing. 3. Approach, flare, and landing at a normal sink rate for the aircraft .MM/DD/YYYY AC 20 - 167A

40 4. All touchdowns in the touchdown zone. Lateral touchdown performance must be demonstrated to be equivalent or better than that achieved in visual operations for the specific aircraft . Longitudinal touchdown performance must be demonstrated within the first third , or the first 3000ft, of the runway , whichever is m ore restrictive, and demonstrated to be equivalent or better than that achieved in visual operations for the specific aircraft .

5. Prompt and predictable correction of any lateral deviation away

from the runway centerline to smoothly

intercept the centerline. 6. Touchdowns with a bank angle that is not hazardous to the airplane. 7. Demonstrated pe rformance of the installed EFVS at representative visibilities for EFVS I and EFVS II operatio ns a described in this document , will determine any additional limitation (for example, crosswind and offset).

8. A normal derotation. 9. Satisfactory

and smooth control of the path of the airplane along the runway centerline through rollout to a safe taxi speed. 10. A safe go around anyt ime including up to touchdown in all configurations t o be certified. **6 -**  **3. Environmental Qualification.**  a. Installed equipment meets the criteria in RTCA/DO - 160F (as revised), Environmental Conditions and Test Procedures for Airborne Equipment. b. Design Assurance. 1. Follow the criteria of RTCA/DO - 178 B or higher , Software Considerations in Airborne Sy stems and Equipment Certification, to conduct software design assurance tests. The version must be current at time of application.

2. Follow the criteria of RTCA/DO - 254, Design Assurance Guideline for Airborne Electronic Hardware , to conduct hardware design assurance tests, if applicable. The version must be current at time of application .MM/DD/YYYY AC 20 - 167A

A1 - 1 **Appendix 1. FAA EFVS 14 CFR Compliance (Partial List) 1**  **- 1.**  **Airworthiness Standards .**  a. Certification Procedures for Products and Parts (14 CFR part 21). b. Normal, Utility , Acrobatic, and Commuter Category Airplanes (14 CFR part 23). c. Transport Category Airplanes (14 CFR part 25). d. Normal Category

Rotorcraft (14 CFR part 27). e. Transport Category Rotorcraft (14 CFR part 29). **1 -**  **2. EFVS Compliance**  **.** The following re quirements address EFVS and are in addition to HUD criteria . The amount of new test data can be determined by the individual application, availability , and relevance of data. **Table 3**  **. EFVS Acceptable Methods of Compliance 14 CFR §**  **Description Acceptable Method of**  **Compliance** 23/25/27/29.251 Vibration and b uffeting Flight Test 23/25/27/29.301 Loads Analy sis 23/25/27/29.303 Factor of safety Analy sis 23/25/27/29.307 Proof of structure Analy sis 25.561/25.562(c)(5) ) Emergency landi ng c onditions; Head Injury

Criterion (HIC) Analy sis 25/27/29.571 and 23.573 Damage - tolerance and fatigue

evaluation of structure Analy sis 25.571(e) Damage - t olerance and fatigue

evaluation of structure (discrete source) evaluation Analy sis and/or Tes t (See Note) 25.581 Li ghtning p rotection Analy sis 23/25/27/29.601 General DrawingMM/DD/YYYY AC 20 - 167A

A1 - 2 **14 CFR § Description**  **Acceptable Method of Compliance**  23/25/27/29.603 Materials Drawing 23/25/27/29.605 Fabrication methods Drawing 23/25/27/29.609 Protection of structure Drawing 23/25/27/29.611 Accessibility provisio ns Drawing 23/25/27/29.613 Material Strength properties and

material design values Drawing, Analy sis, Test (See Note) 23/25/27/29.619 Special factors Analy sis 23/25/27/29.625 Fitting Factors Analy sis 25.629 (d)(8) Aeroelastic stability Analy sis, Tes t 25.631 Bird strike d amage Analy sis, or T est if necessary . (Testing should be accomplished unless the anal ys is shows that the integrity of the original structure has not been compromised by EFVS installation modification.) 23/25/27/29.771 Pilot compartment Flight Test 23/25/27/29.773 Pilot compartment view Flight Test 23/25/27/29.777 Flight deck controls Flight Test 23/25/27/29.1301 Function and installation Ground Test and Flight Test 23/25/27/29.1309 Equip, sy stems, and install Analy sis and/or Tes t and D esign data 25.1316 Sy stem lightning protection Analy sis and Ground TestMM/DD/YYYY AC 20 - 167A

A1 - 3 **14 CFR § Description**  **Acceptable Method of Compliance**  23.1308, and 25/27/29.1317 High - i ntensity Radiated Fields (HIRF) Protection Ground Test and Flight Test Analy sis/Data 23/25/27/29.1321 Arrangement and visibility Ground Test and Flight Test 23/25/27/29.1322 Warning, caution, advisory lights Ground Test and Flight Test 25.1323 Airspeed indicating s ys tems Flight Test 25.1335 Flight director s ys tems Ground Test and Flight Test 23/27.1351 Electrical S ys tems and

Equipment ; Gene ral Analy sis 25/29.1353 Electrical equipment and

installation Analy sis 23/25/27/29.1357 Circuit protective devices Analy sis and Ground Test 23/25/27/29.1381 Instrument lights Ground Test and Flight Test 23/25/27/29.1419 Ice p rotection Analy sis 23/25/29.1431(a)(c) Electronic equipment Analy sis and Ground Test 23/25/27/29.1459(e) Flight data recorders Flight test 23/25/27/29.1501 Operating Limitations and

In formation; General Flight Test 23/25/27/29.1523 Minimum flight c rew Flight Test or Simulation 23/25/27/29.1525 Kind s of o peration Flight Test 23/25/27/29.1529 Instructions for Continued

Airworthiness Design DataMM/DD/YYYY AC 20 - 167A

A1 - 4 **14 CFR § Description**  **Acceptable Method of Compliance**  23/25/27/29.1581 Aircraft flight manual ; General Design Data and Flight Test 23/25/27/29.1583 Operating limitations Flight Test Data 23/25/27/29.1585 Operating procedures Flight Test Data 26.47 Holders of and applicants for a supplemental ty

pe certificate - alterations and repairs to alterations. Analy sis

**. Note**  : In some cases, previously app roved test data for the aircraft may be resubmitted for compliance, if anal ys is can e stablish that the test data remains valid for the aircraft with the new modification.MM /DD /YYYY AC 20 - 167A

A2 - 1 **Appendix 2. EFVS I and EFVS II**  **Systems Safety Guidance 2**  **- 1.**  **General.** a. Safety

C riteria. Safety

criteria for approach and landing sy stems generall y consider four elements: accuracy , continuity , availability , and integrity. These criteria appl y to both the external navigation sy stems as well as airborne navigation equipment. Trajectory management or flight technical error, which can be interpreted as signal structure contributing to roughness, bends and scalloping of ILS - based guidance, should also be considered. They also define how the airspace and aircraft are integrated together to make a safe approach and landing. The FAA dev eloped, in conjunction with the other governments, definitions related to safety and performance for a landing s ys tem. b. Transport Category Airplanes. For aircraft s ys tems, 14 CFR 25.1309 defines the safety requirement and AC 25.1309 define s the means for v erification . The probability of each catastrophic failure condition must be 10 - 9 or less per flight hour considering any mode of flight, any combination of failures causing an unsafe condition, and including the probability of the crew to cope with the f

ailures. The FAA accepts this number to assure a negligible adverse effect on accident rates, and to help reduce them as new sy stems come on line. c. General Aviation or Non - Transport Category Airplanes. Similar information can be found in 14 CFR 23.1309 an d AC 23.1309. The relationship among airplane classes, probabilities, severity of failure conditions and software development assurance levels is found in AC 23.1309 - 1. d. Rotorcraft. Similar information can be found in 14 CFR 27.1309 and AC 27 - 1B and 14 CF R 29.1039 and AC 29 - 2C . **2 -**  **2. Required Level of Safety**  **.** The required level of safety for any aircraft s ys tems, therefore, depends on the ability of the crew to cope with failures as shown in Table 3, which lists the categories of s ys tems and failure probabilitie s to meet the safety criteria in 14 CFR parts 23 and 25 airplanes. For part 23 airplane s , similar information can be found in 14 CFR 23.1309 and AC 23.1309 - 1D. The relationship among airplane classes, probabilities, severity of failure conditions and sof tware development assurance levels is found in AC 23.1309 - 1E.

**Table 4**  **. Required Level of Safety, 14 CFR part 25 Aircraft** Required Level of Safety, 14 CFR part 25 airplanes Classification Effect Target Probability P Minor Slight reduction in safety margins or functional

capabilities. Slight increase in crew workload. Some inconvenience to occupants. 10E - 3 > P > 1E - 5MM /DD /YYYY AC 20 - 167A

A2 - 2 Major Significant reduction in safety margins or functional

capabilities. Significant increase in crew workload o r in conditions impairing crew efficiency . Some discomfort to occupants. 10E - 5 > P > 1E - 7

Hazardous/ Severe Major Large reduction in safety margins or functional

capabilities. Higher workload or ph ys ical distress such that the crew could not be relied upon to perform tasks accuratel y or completely. Adverse effects upon occupants including serious or fatal injury

to a relatively small number of occupants other than the flight crew. 10E - 7 > P > 1E - 9

Catastrophic Failure conditions which would prevent c ontinued

safe flight and landing, resulting in multiple fatalities, usually with the loss of the airplane. 10E - 9 > P **2 -**  **3. Demonstration.**  To meet the safety

criteria, the EFVS design will be demonstrated through anal ys is and engineering tests to preclude any c ritical failure combinations that can cause hazardousl y misleading information to be presented to the crew, or which can otherwise subsequentl y cause an unsafe condition. Failures which are self - evident or made obvious to the crew, and with which they

can safel y cope, need not be specifically monitored. **2 -**  **4. State Data.**  The aircraft state data is provided by the standard inertial, air data, and radio guidance sensors. The HUD or display

processor will be required to be at a sufficient level of safety for the aircraft ty pe and application to detec t critical random or common faults that could otherwise cause an unsafe condition. The ability to continue the approach below the standard Category I DA/DH/MDA/MDH therefore is strictl y borne b y the pilot, a safety fac tor already accounted for in the safety analysis for standard Category I operations. The example below in Table 5 is a model case and cannot be applied for any specific aircraft. Functional hazard assessments as required b y the FAA are aircraft and s ys t ems specific.MM /DD /YYYY AC 20 - 167A

A2 - 3 **Table 5**  **. Example EFVS/HUD Functional Hazard Assessment, 14 CFR part 25 Aircraft,**

**ILS Approaches to 100 ft Height Above Touchdown, RVR 1200 ft** FHA NO. FAILURE CONDITION PHASE OF FLIGHT PI LOT ACTION HAZARD

IN DEX O BJECTIVE 1.0 LOSS OF FUNCTION 1.1 Loss of EFVS imagery on HUD Taxi and Takeoff

Enroute Terminal Arrival Final Approach - Above 100 ft. EFVS height above touchdown zone elevation Go - Around Crew would revert to standard head up and/or head down pro cedures MI

NOR 1 0 E - 3

1.2 Loss of EFVS imagery on HUD Final Approach - From

100 ft. height above touchdown zone elevation to Landing Crew would perform a go around or possibly a minimum flare landing MI

NOR 1 0 E - 3

1.3 Loss of HUD sy mbology Taxi and Takeo ff

Enroute Terminal Arrival Final Approach - Above 100 ft. height above touchdown zone elevation Go - Around Crew would revert to standard head down procedures MI

NOR 1 0 E - 3

1.4 Loss of HUD sy mbology Final Approach - From

100 ft. height above touchdown zone elevation to Landing Pilot would continue the approach and land MI

NOR 1 0 E - 3

1.5 Loss of HUD and EFVS Imagery Final Approach - From

100 ft. height above touchdown zone elevation to Landing Pilot would continue the approach and land MI

NOR 1 0 E - 3MM /DD /YYYY AC 20 - 167A

A2 - 4 FHA NO . FAILURE CONDITION PHASE OF FLIGHT FAILURE EFFECT HAZARD

IN DEX OBJECTIVE 2.0 MI SL EADING IN FORMAT ION 2.1 Misleading EFVS imagery on HUD Taxi

Enroute Terminal Arrival Final Approach - Above 100 ft height above touchdown zone elevation Go - Around Crew would

revert to standard head down procedures MI

NOR 1 0 E - 3

2.2 Misleading EFVS imagery on HUD Final Approach -

From 100 ft. height above touchdown zone elevation to Landing Crew would

perform a go around or possibly a minimum flare landing MAJOR 1 0 E - 5

2. 3 Misleading HUD sy mbology Taxi and Takeoff

Enroute Terminal Arrival Final Approach - Above 100 ft. height above touchdown zone elevation Final Approach - From 100 ft. height above touchdown zone elevation to Landing Go - Around Pilot would take

appropriat e action as defined in AFM for standard display s and HUD Various

failure conditions with the highest hazard index being MAJOR Various failure

conditions with the highest objective being 1 0 E - 5

2.4 Misleading EFVS imagery and HUD s ymbology Final Approach -

Above 100 ft. height above touchdown zone elevation Copilot would

recognize condition using copilot's PFD MAJOR 1 0 E - 5

2.5 Misleading EFVS imagery and HUD s ymbology Final Approach -

From 100 ft. height above touchdown zone elevation to Landing Crew wou ld

perform a go around or possibly a minimum flare landing MAJOR 1 0 E - 5MM /DD /YYYY AC 20 - 167A

A2 - 5 FHA NO. FAILURE CONDITION PHASE OF FLIGHT FAILURE EFFECT HAZARD

IN DEX OBJECTIVE 3.0 OBSTRUCTION OF PILOT'S VI EW 3.1 Obstruction of the pilot's view through the HUD Takeoff Pi lot would abort takeoff prior to V 1 MAJOR 1 0 E - 5 3.2 Obstruction of the pilot's view through the HUD Taxi

Enroute Terminal Arrival Pilot would take appropriate action MI

NOR 1 0 E - 3 3.3 Obstruction of the pilot's view through the HUD Final Approach -

Above 100 ft. height above touchdown zone elevation Go - Around Pilot would take appropriate action MAJOR 1 0 E - 5

3.4 Obstruction of the pilot's view through the HUD Final Approach - From

100 ft. height above touchdown zone elevation to Landing Pilot would execut e a go around MAJOR 1 0 E - 5MM/DD/YYYY AC 20 - 167A

A3 - 1 **Appendix 3. EFVS I and II**  **Safety Standards 3**  **- 1.**  **Safety factors for EFVS described in this AC** Safety standards for the following factors include: a. An acceptable degree of interference of the window or “window and HUD” view, potential image misalignment, distortion, and the potential for pilot confusion or misleading information. b. Determination of EFVS imagery as flight guidance. The FAA does not intend for the EFVS imagery

to be used either as a means of flight guidance/instrument guidance , or as the substitution for the outside view prior to DA/DH or MDA . c. Criteria to determine EFVS is of the kind and design appropriate to the following functions: 1. Presenting an enhanced view that would aid the pilot during the approach.

2. Displaying an image that the pilot can use to detect and identify the “visual references for the intended runway” required by 14 CFR 91.17 6(b)(3) to continue the approach with vertical guidance to 100 feet height above touchdown (HAT).

3. Depending on the atmospheric condi tions and the particular visual references that happen to be distinctly visible and identifiable in the EFVS image, these two functions (found in paragraphs 3 - 1,a, 1 and 3 - 1, a, 2) would support its use by the pilot to visually monitor the integrity of the approach path.

4. Compliance does not affect the applicability of any of the requirements in the operating regulations (such as 14 CFR parts 91, 121, 125 and 135). The EFVS does not change the approach minima prescribed in the standard instrument approach procedure being used; published minima still apply . (Refer to AC 90 - 106A for additional information) **3 -**  **2. Features.**  a. The EFVS can be used as a supplemental device to enhance the pilot's situational awareness during any phase of flight or operation in which its s afe use has been established. b. An EFVS image can provide an enhanced image of the scene that can compensate for any reduction in the clear outside view of the visual field framed b y the HUD combiner. The pilot must be able to use this combination of inform ation seen in the image, and the natural view of the outside scene seen through the image, as safely and effectivel y as the pilot would use a 14 CFR 2 X .773 - compliant pilot compartment view without an EVS image. c. 14 CFR 2 X .1301, Equipment: Function and inst allation, and 25.1309, Equipment, sy stems, and installations, address certain image characteristics, installation, demonstration, and sy stem safety. 1. Image characteristics criteria include:

(a) Resolution (b) Luminance (c) Luminance uniformityMM/DD/YYYY AC 20 - 167A

A3 - 2 (d) Low level luminance (e) Contrast variation (f) Display

quality (g) Display

dy namics (for example, jitter, flicker, update rate, and lag) and (h) Brightness controls

2. Installation criteria address: (a) Visibility

and access to EFVS controls (b) Integration of EFVS in the cockpit **3 -**  **3. Demonstration.**  The EFVS dem onstration criteria address the flight and environmental conditions that should to be covered. a. The EFVS imagery on the HUD must not degrade the safety of flight, nor interfere with the effective use of outside visual references for required pilot tasks, du ring any phase of flight in which it is used. b. To avoid unacceptable interference with the safe and effective use of the pilot compartment view, the EFVS device should meet the following criteria :

1. The EFVS design should minimize unacceptable display charact eristics or artifacts (for example, noise, “burlap” overlay , running water droplets) that obscure the desired image of the scene, impair the pilot's ability to detect and identify

visual references, mask flight hazards, distract the pilot, or otherwise degrade task performance or safety.

2. Control of EFVS display brightness should be sufficiently effective, in dy namically changing background (ambient) lighting conditions, to prevent full or partial blooming of the display

that would distract the pilot, impair the pilot's ability to detect and identify visual references, mask flight hazards, or otherwise degrade task performance or safety . If automatic control for image brightness is not provided, it should be shown that a single manual setting is satisfactory .

3. A readil y accessible control , that does not require the removal of the pilot ’s hands from the primary flight controls, must be provided that permits the pilot to immediately

deactivate and reactivate display of the EVS image on demand. 4. The EFVS image on the HUD should not impair the pilot's use of guidance information nor degrade the presentation and pilot awareness of essential flight information displayed on the HUD, such as alerts, airspeed, attitude, altitude and direction, approach guidance, windshe ar guidance, TCAS resolution advisories, and unusual attitude recovery cues. 5. The EFVS image should be sufficientl y aligned and conformal to both the external scene and conformal HUD s ymbology so as not to be misleading, cause pilot confusion, or increase w orkload.MM/DD/YYYY AC 20 - 167A

A3 - 3 6. The safety and performance of the pilot tasks associated with the use of the pilot compartment view must not be degraded by the display

of the EFVS image. Pilot tasks that must not be degraded by the EFVS image include: (a) Detection, accurate identi fication, and maneuvering, as necessary , to avoid traffic, terrain, obstacles, and other hazards of flight.

(b) Accurate identification and use of visual references required for every task relevant to the phase of flight. 7. Compliance with these criteria does no t affect the applicability of any of the requirements in the operating regulations (for example, 14 CFR parts 91, 121, 125 and 135). The criteria must be of a kind and design appropriate to the following functions:

(a) Present an image to aid the pilot during the approach. (b) Display

an image that the pilot can use to detect and identify the "visual references for the intended runway " required by 14 CFR 91.176 to continue the approach to 100 feet height above touchdown (HAT) under EFVS I operations or all the way to touchdown and rollout under EFVS II operations . Appropriate limitations should be included in the Operating Limitations section of the Airplane Flight Manual to prohibit the use of the EFVS for functions not found to be acceptable. c. In addition to the sensor imagery , at least the following specific aircraft flight information must be displayed :

1. Airspeed 2. Vertical speed; 3. Aircraft attitude; 4. Heading; 5. Altitude; 6. Command guidance as appropriate for the approach to be flown; 7. Path deviation indications; 8. Flight p ath vector; and 9. Flight path angle reference cue. 10. Radio altitude (For s ys tems seeking EFVS II credit) 11. Flare Cue (For s ys tems seeking EFVS II credit) d. Head - Up Display . An EFVS used to conduct operations under 14 CFR 91.176 , 121.651, 125.381, and 135.225 must have an FAA ty pe design approval, or for a foreign registered aircraft, the EFVS must comply with all of the EFVS requirements of the U.S. regulations. Under 14 CFR 91.176 , an EFVS is an installed airborne s ys tem which includes:

1. The display

element, whic h is a HUD or an equivalent display , that presents the features and characteristics required by the regulations such that they are clearl y visible to the pilot flying in his or her normal position and line of vision looking forward along the flight path.MM/DD/YYYY AC 20 - 167A

A3 - 4 2. S ensors that provide a real - time image of the forward external scene topograph y, as described above.

3. Computers and power supplies. 4. Indications. 5. Controls.MM/DD/YYYY AC 20 - 167A

A4 - 1 **Appendix 4. Sample EFVS I**  **Flight Test Considerations 4**  **- 1.**  **General Flight Test Considerations.** a. The objecti ves of the flight test program are to ensure that the s ys tem performs its intended function when installed, and to demonstrate that the EFVS is operationally acceptable and safe. The objectives of the flight test program are not to quantitativel y measure the detection performance of the sensor. b. At the end of the flight test program, the EFVS I should have demonstrated it is capable of imaging the required visual references before they are visible out the window using natural vision. The EFVS should enable descent below DA/DH or MDA using enhanced flight visibility when visual references would not otherwise be visible using natural vision at an altitude no lower than DA/DH or MDA . c. The combination of the EFVS I imagery with the HUD s ymbology and the relation ship between the two in terms of brightness and contrast is a critical issue with respect to the installation; therefore, for the purpose of certification flight testing, the environmental conditions chosen should be such that these parameters are adequate ly evaluated. d. Environmental conditions should be chosen to exercise both the automatic and manual control of items such as brightness, contrast, and gain, and any other parameter that affects the image displayed to the pilot. **4 -**  **2. Minimum Flight Test Conditions**  **Observed.** a. Testing should include an appropriate number of fault - free approaches (see note below) in as many of the conditions listed below as practicable and as applicable. Past experience has shown that more than 50 fault - free approaches to demonstrate than an EFVS adequatel y performs its intended function. The list below should be assessed against the specific sensor ty pe . A dditional test conditions can be specified . 1. Night VFR conditions over various topography (urban, rural, snow covered, etc.). 2. Day and night IFR conditions over various topography .

3. Representative levels of rainfall. 4. Representative levels of snowfall. 5. Representative levels of fog. 6. Haze 7. Representative sun angles. 8. Representative airport lighting configurations. 9. Representative airport/runway surface conditions (dry , wet, standing water, snow cover).

10. Representative thermal crossover conditions.MM/DD/YYYY AC 20 - 167A

A4 - 2 11. Representative crosswind and off - set approach course conditions regarding lateral FOR.

12. Representative runway surface types (dirt, asphalt, concrete, etc.). 13. Representative adjacent surfaces ty pes ( dirt , asphalt , concrete , etc.). 14. Representative vertical path. **Note** : A successful go - around due to lack of either enhanced vision from the DH/DA or natural vision at 100 ft above TDZE , does not constitute a f aulted approach. A faulted approach is if: 1. HUD or EFVS I failure has occurred. 2. At 100 ft above TDZE the indicated airspeed, heading, or attitude are not satisfactory

for a normal flare and landing, due to a confusing or misaligned EFVS I image. 3. At 100 ft a

bove TDZE the aircraft is not positioned so that the cockpit is within, and tracking so as to remain within, the lateral confines of the runway extended. 4. Due to a confusing or misaligned image , the touchdown will be too short or too long. 5. The EFVS I image degrades the fl y- ability of the display

such that a successful approach to DA/DH or MDA/MDH is not possible. **4 -**  **3. Test Points**  Testing should include all phases of flight for which the applicant seeks approval of the s ys tem. In addition to the success criteria for approaches, the EFVS I minimum performance standards require the assessment of the HUD/EFVS I display when used in conjunction with the flight instrumentation required in 14 CFR 91.176 and listed in chapter 4, paragraph 4 - 5.a.3 of this AC. The followi ng evaluations should be performed in representative configurations. (The pilot evaluation matrix is at the end of this appendix.) **4 -**  **4. Evaluation D**  **uring Taxi** a. Assess EFVS I/HUD combination while taxiing and making identification of objects on runway s, taxiway s , parking aprons. b. Verify

the use of EFVS I does not cause confusion or misleading information when viewing through the HUD/EVS all types of airport runway, taxiway, obstruction, and barrier lighting , marking and signage as well as the navigation, taxi, and landing lights of other aircraft **.** c. Verify

the HUD combiner, with the image displayed, does not significantly alter the color perception of the external scene . d. Assess lack of burn - in or blooming from high intensity heat sources such as operating (running) engines, etc. **4 -**  **5. Take off Evaluation**  a. Ensure correct pitch angle is achieved using HUD pitch reference target.MM/DD/YYYY AC 20 - 167A

A4 - 3 b. Verify

s ymbology

in EFVS I mode is clear, visible and does not cause over control or oscillations in acquiring and maintaining the required ground tra ck. c. Confirm the HUD with EFVS I provides the pilot with a quick - glance (instant) sense of flight parameters. d. Assess the transition to different selected vertical modes. e. Evaluate the EFVS I image during the take off roll and throughout the climb segment, ag ainst the attributes listed in the pilot evaluation matrix. **4 -**  **6. Climb and Descent and Lateral Modes Evaluation**  a. Climb, descent, and lateral modes should be evaluated in day and night IMC and VMC to assess HUD/EFVS I compatibility . b. During vertical and lateral guidance maneuvers, evaluate the EFVS I image against the attributes listed in the pilot evaluation matrix. **4 -**  **7. Instrument Approaches.**  During any instrument approach for which approval is sought, HUD/EFVS I compatibility should be evaluated against the attribute s listed in the pilot evaluation matrix. **4 -**  **8. Flare Landing and Go Around**  a. While using EFVS I during final approach and through the flare (below 50 ft), touchdown roll or go - around, assess the transition to natural vision and compatibility of the guidance when f

ollowing the HUD/EFVS I flight cues. b. Confirm landing rollout information, if provided in the display , is sufficiently visible to the pilot and does not cause over- control or oscillations in acquiring and maintaining the required ground track. c. Throughout th e approach guidance maneuvers , evaluate the EFVS I image against the attributes listed in the pilot evaluation matrix. **4 -**  **9. Copilot Monitor**  a. A copilot monitor is not required b y the FAA for operations within the United States. However, if one is installed, the applicant should assess the ergonomic aspects of the image on the copilot’s EFVS I monitor.

1. Verify

satisfactory

display of imagery

in all lighting and environmental conditions and that dimming controls of the display are adequate.

2. If the display

has dual p urposes, verify the means of switching the display to being the EFVS I monitor and back is satisfactory and clearl y evident. 3. Verify

no flicker and/or jitter in the display . 4. Verify

no objectionable glare or reflections are generated by the display

or are vi sible in the display .

5. Verify

the co - pilot’s use of the EFVS I monitor does not require undue head/body movement away from his/her normal scan pattern or his/her normal seated position . **4 -**  **10. Failure Cases.** MM/DD/YYYY AC 20 - 167A

A4 - 4 Failure cases to support the FHA should be assessed as required, for example, uncommanded full image brightness, misaligned image, frozen image, etc. in addition to the approaches required in this appendix. **4 -**  **11. Ice Protection System Evaluation**  a. If the EFVS I sensor installation has ice protection capability , the EFV S I image must be evaluated with the ice protection on and off in representative environmental conditions . b. Icing of the sensor fairing/radome must be appropriately assessed in accordance with the certified flight envelope . **4 -**  **12. Evaluation Matrix.**  a. Table 6 contai ns the pilot’s evaluation matrix. The evaluation matrix should be used to support the testing described in this appendix. **Table 6**  **. EFVS I**  **Evaluation Matrix** A Confirm crew workload is not adversel y affected by the HUD/EFVS I instal lation. B Verify

n o adverse physiological effects from using the HUD/EFVS I (for example, fatigue, eye strain). C Verify

HUD/EFVS I symbology i s visible within pilot Field of View (FOV) (When viewed by

b oth eyes from an y off - cent e r position within eye b ox, non uniformities should not produce perceivable differences in binocular view). D Verify

no jitter o r flicker of HUD/EFVS I sy mbology /image. E Verify

the EFVS I image does not have noise, local disturbances or artifacts that distract from the use of the sy stem. F If HUD sy

mbology h as been modified to accommodate the EFVS I image, assess HUD guidance and ensure that introduction of EFVS I does not induce lag in control sy mbols inducing PI O. G Verify

the sy stem is not adversel y affected by aircraft maneuvering or changes in attitudes encountered during the referenced environmental conditions. H Ensure the required flight and navigation functions applicable for the phase of flight being evaluated are clearl y displayed on the HUD with no unacceptable oc clusions during testing. I Verify

the total data presented by the EFVS I imagery

and HUD sy

mbology d oes not over clutter the HUD combiner display area. J Assess the degree of obscuration of the pilot’s outside view or field of view through the cockpit wi ndow as a result of EFVS I imagery and HUD s ymbology .MM/DD/YYYY AC 20 - 167A

A4 - 5 K Confirm the pilot’s ability t o detect hazards, maneuver, avoid traffic, terrain or other obstacles, is not impaired or degraded b y the display of EFVS I imagery . L Confirm there is no discrepancy b e tween the conformal HUD sy mbols, sensor image, and the outside view through the windshield. M Verify

outside visibility

a s viewed through combiner sensor imagery is adequately aligned and conformal to the external scene and HUD sy mbology . N Confirm the E FVS I imagery d oes not obscure the desired imagery o f the scene, impair the pilot’s ability to detect and identify visual references, mask flight hazards, or distract the pilot. O Assess the ease of operating the HUD with the sensor image displayed, durin g aircraft maneuvers and change in attitude, encountered in normal operations. P Determine whether there is an y glare or reflection that could interfere with the EFVS I image either in day or night lighting conditions. Q Determine if an y impairment is experienced in the ability to use the display

d ue to visible external surfaces within the HUD. R Determine whether the sensor image displayed on the HUD combiner objectionably

impairs the pilot compartment view. S Assess impact of water droplets running ac ross the sensor window to ensure that it does not distract the pilot or degrade his/her task performance or safety . T Verify

identification of approach lights, runway threshold, touchdown zone etc. as per 14 CFR 91.176(b)(3) . U Confirm the HUD EFVS I ima ge is suitable and performs its intended function. V Confirm the sensor image on the co - pilot’s display ( if installed) is useable and performs its intended function. W Evaluate the EFVS I image during the takeoff roll and throughout the climb segment, ag ainst the attributes listed in the attached pilot evaluation matrix. X During vertical and lateral guidance maneuvers evaluate the EFVS I image against the attributes listed in the attached pilot evaluation matrix.MM/DD/YYYY AC 20 - 167A

A5 - 1 **Appendix 5. Sample Flight Test C onsiderations for EFVS**  **II 5**  **- 1.**  **General Flight Test Considerations.** a. The objectives of the flight test program are to ensure that the s ys tem performs its intended function when installed, and to demonstrate that the EFVS II is operationall y acceptable and safe. The objectives of the flight test program are not to quantitativel y measure the detection performance of the sensor. b. The flight test program should demonstrate that the EFVS II is capable of providing enhanced flight visibility that is no less than the vis ibility required by

the instrument approach, in conditions where actual flight visibility is no less than the visibility requ ired b y the instrument approach . The EFVS II flight demonstrations should prove that the sy stem provides a satisfactory

view of th e required visual references for descent below DA/DH even when they are not visible using natural vision. The EFVS II should enable the pilot to complete the instrument approach, landing, and rollout to a safe taxi speed using enhanced flight visibility when visual references would not otherwise be sufficientl y visible using natural vision. c. The flight test should demonstrate that the EFVS II display of imagery

and HUD sy mbology is satisfactory, so that both elements of information are readable and usable w ithout mutual interference. The flight test should demonstrate that the brightness levels of the imagery and the s ymbology

can be effectivel y controlled and provide satisfactory contrast between two. Since flight deck and external light levels can affect the readability of the EFVS II display

and can change significantl y throughout the approach and landing operation, the flight test should demonstrate that control of display brightness in dy

namic conditions does not require excessive workload for the pilo t. d. Environmental conditions sh ould be chosen to exercise both the automatic and manual control of items such as brightness, contrast, and gain, and any other parameter that affects the image displayed to the pilot. **5 -**  **2. Minimum Flight Test Conditions Observed.**  a. Testing sh ould include an appropriate number of fault - free approaches and landings in as many of the conditions listed below as practicable and as applicable . The applicant should plan for no less than 50 fault free approaches and landings, of which at le ast 5 approaches will be needed to confirm satisfactory go - around performance. A sufficient number of approaches will be needed, with visibility conditions between 2400ft RVR or less and 1000ft RVR , to demonstrate that the EFVS II can provide at least 240 0 ft of enhanced flight visibility and enable the complete low visibility operation. The applicant and the FAA will agree on the minimum number of such approaches, but the number may change depending on demonstration results. The following list sh ould be assessed against the EFVS II Sensor(s), intended use and the specific installation. Additional tests may be specified . The environmental conditions to be tested must be agreed to by the FAA.

1. Night VFR conditions over various topography (urban, rural, s now covered, etc. ). 2. Day and night IFR conditions over various topography . 3. Representative levels of rainfall .MM/DD/YYYY AC 20 - 167A

A5 - 2 4. Representative levels of snowfall . 5. Representative levels of fog . 6. Haze . 7. Representative sun angles . 8. Representative airport lighting configurations . 9. R epresentative airport/runway surface conditions (dry , wet, standing water, snow covered) .

10. Representative thermal crossover conditions . 11. Representative wind conditions (e.g., crosswind, headwind, tailwind) and off - set conditions regarding lateral field of re gard .

12. Representative runway surface types (dirt, asphalt, concrete, etc.) . 13. Representative adjacent surfaces ty pes ( dirt , asphalt , concrete , etc.) . 14. Representative runway widths . 15. Representative approach procedures and vertical approach angles . 16. Representative runway slopes (within the aircraft limitations) . b. A faulted approach occurs any time the pilot is unable to complete a safe and successful approach, landing, rollout, and turnoff within the operational performance parameters detailed in Appendix 4, or withi n additional operational performance s tandards as may be required b y the certifying authority. However, a faulted approach does not occur due to the lack or loss of enhanced visibility due to the atmosphere, so long as a successful missed approach or reje cted landing is executed. A faulted approach also does not occur due to ATC intervention, interference from other aircraft, interference from ground vehicles or persons, interference from animals (including birds), or any other reason not relating directl y to the EFVS. **5 -**  **3. Test Points.**  a. Testing sh ould include all phases of flight in which EFVS II operation will be permitted, approach types, approach course geometries, and aircraft configurations for which the applicant seeks approval of the sy stem . In addition to the success criteria for the approach, landing and rollout, the EFVS II minimum performance standards require the assessment of the HUD/EFVS display

when used in conjunction with the head up flight indications required in 14 CFR 91.176 and listed in ch apter 4, paragraph 4 - 5.a.3 of this AC. For effective post - flight anal ys is and evaluation of the results, past experience has shown that time - stamped video of exactly what is displayed on the HUD are recommended. b. The test program should demonstrate that th e EFVS II image, with superimposed flight s ymbology , does not mislead, distract or jeopardize the safety of the landing and rollout. Without requiring exceptional pilot skill, alerting, strength or workload, the image/s ymbology should allow and provide th e visual cues for the pi lot to perform:

1. Speed control within +10/ - 5 knots of the approach speed, whether manually controlled or with auto - throttle, as proposed by the applicant, up to the point where the throttles are retarded for landing.MM/DD/YYYY AC 20 - 167A

A5 - 3 2. A smooth transit ion through flare to landing. 3. Approach, flare and landing at a normal sink rate for the aircraft . 4. Lateral touchdown performance shall be demonstrated to be the equivalent or better to that achieved in visual operations for the specific aircraft . Longitudi nal touchdown performance shall be demonstrated within the first 1/3, or the first 3000 ft, of the runway , whichever is more restrictive, and demonstrated to be equivalent or better to that achieved in visual operations for the specific aircraft .

5. Prompt an d predictable correction of any lateral deviation away from the runway centerline to smoothly

intercepted the centerline. 6. Touchdowns with a bank angle that is not hazardous to the airplane. 7. Demonstrated performance of the installed EFVS II at the represent ative RVR/visibility, as described in this document, will determine any additional limitations (for example, crosswind and offset).

8. A normal de - rotation . 9. Satisfactory

and smooth control of the airplane from touchdown to a safe taxi speed. 10. Satisfactory and smooth control of the path of the airplane along the runway centerline through rollout to a safe taxi speed. 11. A safe go around anyt ime including touchdown in all configurations to be certified. **5 -**  **4. Evaluation D**  **uring Taxi** a. Assess EFVS/HUD combination while taxiin g and making identification of objects on runway s, taxiway s, parking aprons. b. Verify

that the use of EFVS II does not cause confusion or misleading information when viewing through the HUD/EFVS II appropriate ty pes of airport runway , taxiway , obstruction, and barrier lighting and signage as well as the navigation, taxi, and l anding lights of other aircraft . c. Verify

the HUD combiner with the image displayed does not significantl y alter the color perception of the external scene. d. Assess the impact of burn - in or blooming (if applicable) on the EFVS II image from high intensity heat sources such as running engines, stationary lights, etc. **5 -**  **5. Take off Evaluation.**  a. Ensure correct pitch angle is achieved using HUD pitch sy mbology . b. Verify

s ymbology

in EFVS II mode is clear, visible and does not cause over control or oscillations in acquiring and maintaining the required ground track. c. Confirm that the HUD with EFVS II provides the pilot with a quick - glance (instant) sense of flight parameters. d. Assess the transition to different selected vertical modes.MM/DD/YYYY AC 20 - 167A

A5 - 4 e. Evaluate the EFVS II image during the take off roll and throughout the climb segment, against the attributes listed in the pilot evaluation matrix. **5 -**  **6. Climb and Descent and Lateral Modes Evaluation.**  a. Climb, descent and lateral mod es should be evaluated in day and night IMC and VMC to assess HUD/EFVS II compatibility . b. During vertical and lateral guidance maneuvers , evaluate the E(F)VS image against the attributes listed in the pilot evaluation matrix. **5 -**  **7. Instrument Approaches to the DA**  **(H)** a. During any instrument approach for which approval is sought, HUD/EFVS II compatibility

sh ould be evaluated against the attributes listed in the pilot evaluation matrix. b. Final approach course offsets greater than 3 degrees require further flight test ev aluation. The maximum allowable final approach course offset is to be established by flight test. These tests sh ould include the factors related to the offset, such as the HUD/EFVS II field of view, crosswinds, and the maximum drift angle possible for a conformal flight path vector. Since 14 CFR 91.176 permits EFVS to touchdown for approaches which could be offset up to 15 degrees, flight test evaluation should factor this offset into potential limitations and airworthiness approvals. **5 -**  **8. Final Approach fro**  **m the DA/DH, Flare, Landin g and Rollout to Safe Taxi S**  **peed.** a. While using EFVS II during an enhanced visual final approach and through the flare (below 50ft), touchdown, rollout and turn - off, assess the performance of the EFVS II image and displayed sy

mbolog y against the attributes listed in the pilot evaluation matrix. b. Confirm that a landing and rollout to a safe taxi speed that is primaril y performance based on the EFVS II image and displayed sy mbology does not cause over - control or oscillations in acquirin g and maintaining the required ground track. **5 -**  **9. Rejected Landing**  Confir m that at any

time during the EFVS II based approach between DA/DH and touchdown, a safe rejected landing can be conducted. **5 -**  **10. Pilot Monitoring (PM) Display.**  a. Verify

the display

is located within the maximum primary field of view of the pilot monitoring and any sy mbology displayed should not adversel y obscure the sensor imagery of the runway

environment. b. Verify

satisfactory

display of imagery in all lighting and environmental conditions and that dimming controls of the display are adequate. c. If the display

has dual purposes , verify the means of switching the display to being the EFVS II monitor and back is satisfactory and clearly

evident. d. Verify

that the pilot monitoring use of the PM display mo nitor does not require undue head/body movement away from his/her normal scan pattern or his/her normal seated position.MM/DD/YYYY AC 20 - 167A

A5 - 5 e. Verify

the PM display

provides a conformal image with the visual scene over the range of aircraft attitudes and wind conditions for eac h mode of operation. The PM’s display should be shown to be acceptable for the pilot monitoring to see and identify visual references and to verify

that all visual requirements for the approach and landing are satisfied. **5 -**  **11. Failure Cases.**  Failure cases to su

pport the FHA shall be assessed and tested as required (e.g. uncommanded full image brightness, misaligned image, frozen image, failed image, etc.) during the approaches required in this appendix. **5 -**  **12. Ice Protection System Evaluation.**  a. If the EFVS II sensor ins tallation has ice protection/de - misting capability , the EFVS II image sh ould be evaluated with the ice protection/de - misting on and off in representative environmental conditions. b. Icing of the sensor fairing sh ould be appropriatel y assessed in accordance w ith the aircraft ’s certified flight envelope. **5 -**  **13. Evaluation Matrix**  Table 7 below is the test evaluation matrix that should be used to support the testing described above. **Table 7**  **. EFVS II**  **Evaluation Matrix** A Confirm that crew workload is not adversel y affected by the HUD/EFVS II installation . B Verify

no adverse ph ys iological effects from using the HUD/EFVS II (e.g. f atigue, eye strain). C Verify

HUD/EFVS II symbology is visible within pilot Field of View (FOV) . (When viewed b y both eyes from any off - center position within eye box, non - uniformities shall not produce perceivable differences in binocular view). D Verify

no jitter or flicker of HUD/EFVS II sy mbology /image. E Verify

that the EFVS II image does not have noise, local dis turbances or artifacts that distract from the use of the sy stem. F If HUD s ymbology has been modified to accommodate the EFVS II image, assess HUD guidance and ensure that introduction of EFVS II does not induce lag in control sy mbols inducing PIO. G Verify

the s ys tem is not adversel y affected b y aircraft maneuvering or changes in attitudes encountered during the referenced environmental conditions. H Ensure that the required flight and navigation functions applicable for the phase of flight being evaluated are clearl y displayed on the HUD with no unacceptable occlusions during testing.MM/DD/YYYY AC 20 - 167A

A5 - 6 I Verify

that the total data presented b y the EFVS II imagery and HUD s ymbology

does not over clutter the HUD combiner display area. J Assess the degree of obscuration o f the pilots outside view or field of view through the cockpit window as a result of EFVS II imagery and HUD s ymbology . K Confirm that the pilot’s ability to detect hazards, maneuver, avoid traffic, terrain or other obstacles, is not impaired or degraded by the display

of EFVS II imagery . L Confirm that there is no discrepancy between the conformal HUD s ymbols, sensor image and the outside view through the windshield. M Verify

that outside visibility

as viewed through combiner sensor imagery is adequatel y aligned and conformal to the external scene and HUD sy mbology . N Confirm that the EFVS II imagery does not obscure the desired imagery of the scene, impair the pilot’s ability

to detect and identify

visual references, mask flight hazards or distract the pilot. O Assess the ease of operating the HUD with the sensor image displayed, during aircraft maneuvers and change in attitude, encountered in normal operations. P Determine whether there is any glare or reflection that could interfere with the EFVS II image external surfaces within the HUD. Q Determine if any impairment is experienced in the ability to use the display

due to visible external surfaces within the HUD. R Determine whether the sensor image displayed on the HUD combiner objectionably impairs the pilot compartment view. S Assess impact of water droplets running across the sensor window to ensure that it does not distract the pilot or degrade his/her task performance or safety . T Verify

identification of approach lights, runway threshold, touchdown zone etc. as per 14 CFR 91.176(a)(3) . U Confirm the sensor image on the copilot’s display (if installed) is useable and performs its intended function. V Confirm the sensor image on the copilot’s display (if installed) is useable and performs its intended function. W Evaluate the EFVS II image during the take off roll and throughout the climb segment, against the attributes listed in the attached pilot evaluation matrix. X During vertical and lateral guidance maneuvers evaluate the EFVS II im age against theMM/DD/YYYY AC 20 - 167A

A5 - 7 attributes listed in the attached pilot evaluation matrix. Y Confirm that the EVS provides the correct and appropriate visual cues for the pilot to perform the required stabilized approach from the DA(H). Z Confirm that approach speed can be controlled within +10/ - 5kts, both with and without auto - throttle if fitted, up to the point where the throttles are retarded for landing. AA Confirm that the EVS provides the correct visual cues for the pilot to perform a smooth transition through flare to landing. AB Confirm that the EVS provides the correct visual cues for the pilot to perform a flare and landing with a normal sink rate. AC Confirm that the EVS provides the correct visual cues to alway s allow a consistent touchdown in the defined t ouchdown zone. AD Confirm that the EVS provides the correct visual cues to allow a consistent touchdown with a bank angle that is not hazardous to the airplane. AE Confirm that the EVS provides the correct the correct visual cues to allow satisfactory an d smooth control of the airplane from touchdown to a safe taxi speed. AF Confirm that EVS provides the correct visual cues to allow prompt and predictable correction of any lateral deviation away from the runway centerline to smoothly intercept the centerline. AG Confirm that the EVS provides the correct visual cues to allow prompt and predictable correction of any lateral deviation away from the runway centerline to smoothly intercept the centerline. AH Confirm that the EVS provides the correct visual cues to allow satisfactory and smooth control of the path of airplane along the runway centerline through rollout to a safe taxi speed.MM/DD/YYYY AC 20 - 167A

A6 - 1 **Appendix 6. Sample Airplane Flight Manual (AFM)**  **Supplement Note:**  Appendix 6 presents a sample for the AFM supplement for STC installations. This example may

not be entirely

applicable to airplane manufacturers when SVS, EVS, CVS, or EFVS are approved with the ty pe certificate. The ACO will assist the applicant in developing an appropriate Rotorcraft Flight Manual Suppl ement (RFMS). Installation Center/Repair Station Model XXX EVS/SVS/EFVS 123 Fourth Street Vision Sy stem Any town, USA

FAA APPROVED AIRPLANE FLIGHT MANUAL SUPPLEMENT

ABC MODEL XXX YYY VI SI ON SYSTEM AIRPLANE MAKE: AIRPLANE MODEL: AIRPLANE SERIAL NO.: REGI STRATION NO.: This document must be carried in the airplane at all times. It describes the operating procedures for the ABC Model XXX YYY vision sy stem when it has been installed in accordance with < ma nufacturer's installation manual number and date>. For airplanes with an FAA Approved Airplane Flight Manual, this document serves as the FAA Approved ABC Model XXX YYY Flight Manual Supplement. For airplanes that do not have an approved flight manual, this document serves as the FAA Approved ABC Model XXX YYY Supplemental Flight Manual. The information contained herein supplements or supersedes the basic Airplane Flight Manual dated < insert date> onl y in those areas listed herein. For limitations, pro cedures, and performance information not contained in this document, consult the basic Airplane Flight Manual. FAA APPROVED

____________________ Title Office Federal Aviation Administration City , StateMM/DD/YYYY AC 20 - 167A

A6 - 2 **SAMPLE AIRPLANE FLIGHT MANUAL (Continued)** Installation Center/Repair Station Model XXX EVS/SVS/EFVS 123 Fourth Street Vision Sy stem Any town, USA Table of Contents Section ............................................... Page 1 General.............................................< > 2 L im itations........................................< > 3 Emergency

/Abnormal Procedures....< > 4 Normal Procedures...........................< > 5 Performance......................................< > 6 Weight and Balance................ ..........< > 7 Sy stem Description...........................< >

FAA Approved Page <> of <> Date: ________MM/DD/YYYY AC 20 - 167A

A6 - 3 **SAMPLE AIRPLANE FLIGHT MANUAL (Continued)** Installation Center/Repair Station Model XXX EVS/SVS/EFVS 123 Fourth Street Vision Sy stem Any town, USA SECTI ON 1 - GENERAL <Include the appropriate statement to describe the equipment capability: > EVS: The installed ABC Enhanced Vision S ys tem meets with AC 20 - 167A performance criteria for <situation awareness> . SVS: The installed ABC S ynthetic Vision System meets with AC 20 - 167A performance criteria for <situation awareness> . EFVS I: The installed EFVS has been demonstrated to meet the criteria for AC 20 - 167A for EFVS I to be used for DA/DH or MDA down to 100 feet HAT. During certification flight test, the lowest visibility and maximum final approach course offset angle at which the installed EFVS was demonstrated to be used in lieu of natural vision to descend below DA/DH or MDA and complete a landing in accordance with 14 CFR 91.176(b ) was < insert RVR value or SM value > and < insert angle in degrees >, respectivel y. EFVS II: T he installed EFV S II has been demonstrated to meet the criteria for AC 20 - 167A for EFVS II to be used for instrument approach and landing operations that rely on sufficient visibility conditions to enable unaided rollout and to mitigate for loss of EFVS function. An EFVS that meets the certification criteria for EFVS II also meets the criteria for EFVS I. During certification flight test, the lowe s t visibility and maximum final approach course offset angle at which the installed EFVS was demonstrated to be used in lieu of natural vision to descend below DA/DH or MDA and complete a landing in accordance with 14 CFR 91.176(b) was < insert RVR value or SM value > and < insert angle in degrees >, respectivel y.
SECTI ON 2 - LIMITATIONS 1. The ABC Model XXX YYY Quick Reference Guide, P/N < insert part number>, dated < insert date> (or later appropriate revision) must be immediately available to the flight crew whe never navigation is predicated on the use of the sy stem.MM/DD/YYYY AC 20 - 167A

A6 - 4 2. The sy stem must utilize software version < insert version identification >. 3. A valid and compatible database must be installed and contain current data. 4. <Specify any additional limitations applicable to the particular installation. > FAA Approved Page <> of <> Date: ________

SECTI ON 3 - EMERGENCY/ABNORMAL PROCEDURES EMERGENCY PROCEDURES No Change ABNORMAL PROCEDURES 1. If ABC Model XXX YYY vision sy stem information is not available or invalid, utilize remaining operational navigation equipment as appropriate. 2. If Loss of Integrity

Monitoring message is displayed, revert to an alternate means of navigation appropriate to the route and phase of flight or periodicall y c ross - check the GPS guidance to other, approved means of navigation. SECTI ON 4 - NORMAL PROCEDURES 1. Normal operating procedures are outlined in the ABC Model XXX YYY Pilot's Guide. 2. Sy stem Annunciators <applicable to installations with external annunciators> 3. Sy stem Switches <applicable to installations with external switches>MM/DD/YYYY AC 20 - 167A

A6 - 5 4. Pilot's Display

< describe the pilot's display(s) > 5. Flight Director/Autopilot Coupled Operation < describe any procedures for integrated flight director and/or autopilot system(s) > 6. < include any other normal operating procedures as necessary> FAA Approved Page <> of <> Date: ________MM/DD/YYYY AC 20 - 167A

A6 - 6 SECTI ON 5 - PERFORMANCE No Change SECTI ON 6 - WEI GHT AND BALANCE < Refer to revised weight and balance data, if applicable. > SECTI ON 7 - SYSTEM DESCRIPTION < Provide a brief description of the system, its operation, installation, etc. >

FAA Approved Page <> of <> Date: ________MM/DD/YYYY AC 20 - 167A

A7 - 1 **Appendix 7. Installation of Enhanced Vision System and or/S ynthetic Vision System on**  **Roto r**  **craft 7**  **- 1.**  **General.** This appendix provides guidelines for the installation of EVS and/or SVS installed in Rotorcraft as non - required safety enhancing equipment. To promote standardization installation of non required safety enhan cing equipment, the Rotorcraft Directorate published a policy memo to address a means of compliance for the installation of non - required safety enhancing equipment . Contact the FAA Rotorcraft Directorate for guidance. Also refer to AC 27 - 1B and AC 29 - 2C for certification guidance. **7 -**  **2. Applicability.**  There are unique aspects to rotorcraft that do not apply to fixed wing aircraft. Rotorcraft ty picall y operate at altitudes much closer to the ground and obstacles than fixed - wing aircraft. Additionally , they

ar e inherentl y unstable and, without a stabilization system, require hands - on control at all times accompanied by constant visual scans to keep them oriented correctl y. There are advantages and disadvantages to presenting EVS or SVS information to the pilot . Particular issues of concern are the compelling nature of the display used in a VFR see - and - avoid environment, the presentation of misleading information relating to aircraft location relative to hazards (particularl y in night operations), and the installation of EVS/SVS/CVS displays that interact with automated flight control s ys tems and flight guidance s ys tems. **7 -**  **3. Airworthiness Approval.**  The Rotocraft Directorate has determined that installation of EVS/SVS/CVS on a primary flight display , either ADI or NAV display , requires ACO involvement through the STC process, under FAA Order 8900.1, Volume 4, Chapter 9 “Selected Field Approvals , ” Figure 4 - 68, Major Alterations Job Aid. In stallations on a primary flight display

will involve human factors evaluations and flight test evaluations. **7 -**  **4. Design Considerations.**  The FHA developed for the sy stem should define the hazards of presenting misleading information to the pilot, and loss of an SVS/EVS feature. The s ys tem should be designed accordingl y. The hazard classif ication will be based on display location, intended function of the sy stem features, and phase of flight. The hazard classification of misleading information for SVS/EVS/CVS on the primary flight display s will be higher than the classification of misleading information on a display

outside the pilot’s primary field of view. For example, the hazard classification of misleading information may be lower if the SVS/EVS/CVS is placed on ancillary display s not used for the display of flight information and not in the pilot’s primary field of view. Additionally , see Appendix 8 of this AC for further guidance. However, the Rotorcraft Directorate does not accept “situation awareness only” information on primary flight display s (either PFD or MFD’s within the pilo t’s primary field of view). Therefore the intended function of the SVS/EVS/CVS should be defined. If HTAWS or HTAWS - like features are incorporated, see TSO - C194 HTAWSMM/DD/YYYY AC 20 - 167A

A8 - 1 **Appendix 8. Additional Part 23 Considerations for Enhanced Vision System/or Synthetic**

**Vision System for Situation Awareness Only 8**  **- 1.**  **Introduction.** S ynthetic vision may

be so compelling that pilots may try to use it beyond the intended function. Current sy

nthetic vision sy stems may not offer the depth/distance cueing necessary to be used for te rrain avoidance. Another way of saying this is that error margins may still be too large to use any s ynthetic vision sy stem alone. C urrent s ys tems should be used with approved flight and navigation information. If other s ys tems are not included to augment the sy nthetic vision system for terrain awareness, the applicant should show that the error margins due to field of view size, depth perception, resolution of the database used, resolution of the display , update rate of the display and any other factors are small enough that sy nthetic vision alone is adequate for terrain awareness in all flight conditions expected. Display size constraints may result in a “compressed” display

that has the potential to cause misleading altitude and range estimation. In addition, cumulative errors from GPS, terrain databases, and barometric altimetry s ys tems may contribute to misleading distance and height cues. Adequate mitigation should be provided to avoid the effects of such hazards. Such mitigation may be incorporated in the design or may include training or procedures to use other navigation sources. However, it is unwise to depend solely on Aircraft Flight Manual (AFM) limitations. **8 -**  **2. Terrain Alerting.**  Any airplane equipment incorporating a sy nthetic vision system s hould also provide some ty pe of terrain warning for pilots. The terrain warning feature should be incorporated on the Multifunction Display

(MFD) or separate display unless the applicant can demonstrate that the feature is effective on the PFD. Sy nthetic vision sy stems on the PFD should provide adequate altitude and distance cues if used for terrain warning. a. Applicants may

use TSO - C151c , Class A, B, or C standards as applicable. Applicants may

develop their own terrain warning sy stem. However, the optio n of developing a terrain warning s ys tem is only available when there is not a specific carriage requirement for TAWS or HTAWS; it is not a substitute for any TAWS or HTAWS regulatory requirement. Applicants who want to develop their own terrain warning s ys tem should include:

1. A one - minute caution and 30 - second warning if the airplane’s current flight path will collide with terrain or an obstacle.

2. Aural call - out for both the caution and the warning (CAUTION

– TERRAI N, TERRAIN; WARNI

NG

– TERRAIN, TERRAI N). 3. T errain impact region highlighted on the moving map. 4. A safety margin or buffer of at least 100 feet for cumulative errors in both the GPS altitude and terrain database.

5. A terrain database/DEM developed using the criteria in RTCA DO - 200A, “Standards for Proc essing Aeronautical Data,” September 28, 1998.MM/DD/YYYY AC 20 - 167A

A8 - 2 6. The sy

nthetic vision display

must not provide any information that is in conflict with or incompatible with either the terrain warning or terrain awareness functions of the TAWS or HTAWS. **8 -**  **3. Moving Map Display th**  **at Corresponds to and Complements S ynthetic Vision**  **PFD Display.**  a. S ynthetic vision depictions on the PFD have the potential to provide pilots with enhanced terrain and landmark awareness during non - precision and precision approaches. However, the display

may not provide depth perception and may not provide a field - of

- view for pilots to know what is to the left and right of the display view area. When viewing the terrain on a limited field - of

- view display , pilots may mistakenly

infer the location of the airc raft relative to the terrain. b. There should be a second, complementary plan view display . The second display should depict the same terrain, obstacles, and features that appear on the PFDs sy nthetic vision display . This complementary display mitigates the lack of depth perception and FOV limitations on the ty pical sy nthetic vision display . This display should be the navigation display , but it could also be an MFD or a third, separate display . I deall y, the TAWS OR HTAWS or terrain alerting s ys tem should b e part of this display (unless incorporated into the PFD) so that hazardous terrain or obstacles are highlighted. **8 -**  **4. Minimums Audio Callout Capability.**  Applicants are encouraged to incorporate either a pilot selectable or automatic altitude alert with audio c allout to remind pilots they are approaching minimums. Pilots may “see” the runway environment on their s ynthetic vision display and continue below minimums inadvertently because they

were so intent on following the approach guidance. This scenario is si milar to pilots fixating on a flight director and descending below minimums. Alerting pilots that they are nearing minimums reduces the opportunity for this situation to occur. **8 -**  **5. Digital Evaluation Model (DEM) Resolution.**  The DEM resolution is one factor th at determines how well the sy nthetic vision terrain depiction will match the terrain environment. NASA experiments have shown that a terrain resolution of 30 - arc - seconds “rounds off” the terrain peaks and fills in valley s. This makes the terrain appear l ess hazardous for the peaks than it is and potentially reduces some safety benefit. Conversel y, for the valley s, the terrain appears higher and is therefore conservative. The same set of NASA experiments pointed out that even though pilots preferred terrain created using higher resolutions ( one and three - arc - seconds), a s ynthetic vision display using a 30 - arc - second database could provide more situation awareness (and, therefore, safety) than the conventional instrument panel. Therefore, we had historically considered 30 - arc - second resolution the minimum safety standard for sy nthetic vision display s. This allowed for the introduction of sy nthetic vision systems given the technology

limitations. But technology has surpassed the need to allow as low a min imum resolution. N ew s ys tems should meet 15 arc sec or better. Current sy stems do very well at twice the resolution minimum, but we want to encourage applicants to use the highest resolutions available in unclassified databases. Applicants may also cons ider using very high resolution databases near airports while reducing the resolution in the rest of the database. More importantly , applicants should clearl y define the resolution and measuring units of the DEM usedMM/DD/YYYY AC 20 - 167A

A8 - 3 by their sy nthetic vision sy stem in th e AFMS and the pilots’ handbooks so that pilots can understand any visual limitation caused by resolution limits. **Note** : The DEM resolution needed on a sy nthetic vision display

depends on the intended function of that display . Applicants need to consider how they are going to use the terrain database information for their sy nthetic vision display , and this information should be given to the FAA at the beginning of a s ynthetic vision certification program. Common elevation references are average elevation , maximum elevation, and sometimes, the elevation of the geometric center of the area. As post - spacing increases, the difference between the DEM value and the actual elevation of a point within a cell may differ significantl y . The elevations used for a s ynthetic vision display should be conservative; use the highest elevation for a given cell. This concept is identical to the current sectional charts labeling the highest elevation in the given quadrangle (square sector) of latitude and longitude. **8 -**  **6. Aircraf** 

**t Flight Manual Supplement (AFMS).** The AFMS should contain limitations for pilots on use of the applicant’s system. These limitations should be explained in detail. Warnings, cautions, and notes should also address the proper use and potential misuse of the display for terrain awareness and avoidance. **8 -**  **7. SVS Unusual Attitude Recovery.**  Historically , the FAA required all but essential flight information is removed from the PFD in unusual attitudes. This “decluttering” was meant to aid pi lots in recovering the aircraft. Therefore, the first sy

nthetic vision sy stems removed the s ynthetic depiction and reverted to the traditional “blue - over - brown” display during unusual attitudes. Based on a past report, the FAA Civil Aeronautical Medical Institute (CAMI) observ ed little performance difference between recoveries with and without the sy nthetic depiction. Furthermore, there was a possibility pilots might be temporarily

confused by

the significant change to their primary attitude display . Therefore, applicants sho uld consider leaving the synthetic vision depiction on the PFD for unusual attitude recovery. The SVS update rate will be evaluated in flight test against FAA Practical Test Standard maneuvers. a. Some indication of both sky and ground should alway s be visib le on the PFD for use in initiating unusual attitude recovery . b. Pilots should be able to initiate a recovery toward the correct horizon and altitude within one second of recognition. **Note** : For example, a test scenario could include climbing with a large mo untain or plateau in the background into a stall condition or descending into rising terrain with decreasing airspeed into a stall condition. c. The artificial horizon line and other attitude - relate sy mbology (for example, aircraft s ymbol and pitch ladder) sh ould be very prominent and highl y visible against all possible backgrounds and s ymbology , including the assignment of a level of priority over other sy mbology on the display

commensurate with its importance. **8 -**  **8. Pilot Evaluation.** MM/DD/YYYY AC 20 - 167A

A8 - 4 There are hundreds of variable s that can distinguish one display s ys tem from another. Depending on the design implementation, a sy nthetic vision system might not provide a safety improvement. Because of the number of variables, a thorough FAA pilot evaluation will be necessary for th e first implementation of any sy nthetic vision display

s ys tem. L ess FAA involvement may

be possible on subsequent installations or sy stem upgrades. Often, it is useful to gather subjective pilot assessments of the sy nthetic vision display s. Questionnaires used with flight evaluations and/or simulation are good tools to use for pilot assessment, but they need to be specific rather than merel y solicit general impressions. Accepted and proven evaluation protocol, measures, and scales should be used where a pplicable to ensure the integrity of the evaluation process. The questions should target specific information presented on the display , its intended function, and whether it is usable for flight tasks required for ty pical instrument and commercial ratings. Besides using FAA pilots (including Designated Engineering Representative (DER) pilots), the applicant should consider conducting assessments with representative end user/operational pilots. Applicants should coordinate plans for any pilot evaluation with the responsible ACO.MM/DD/YYYY AC 20 - 167A

A9 - 1 **Appendix 9. Definitions and Acronyms 9**  **- 1.**  **Definitions** a. **Appliance** ( 14 CFR 1.1) - An y instrument, mechanism, equipment, part, apparatus, appurtenance, or accessory , including communications equipment, that is used or intended to be used in operating or controlling an aircraft in flight, is installed in or attached to the aircraft, and is not part of an airframe, engine, or propeller. b. **Approach Lighting Designators** 1. AL SF - I: High Intensity Approach Lighting Sy stem with Sequenced Flashing L ight s, Category IConfiguration. 2. AL SF - II: High Intensity Approach Lighting Sy stem with Sequenced Flashing L ights, Category I I Configuration. 3. MAL SR: Medium Intensity Approach Lighting Sy stem with Sequenced Flashing L ights.

4. SSALR: Simplified Short Approach Li ghting Sy stem with Runway Alignment Indicator Lights.

5. MAL SF: Medium Intensity Approach Lighting Sy stem with Sequenced Flashing L ights.

6. RAIL: Runway

Alignment Indicator Lights (RAIL). 7. SF: Sequenced Flashing Lights (SF). c. **Combined Vision System (CVS)** - A s ys tem which combines information from an enhanced vision sy stem and a s ynthetic vision system in a single integrated display. d. **Command Guidance** - Sy mbolic information that directs the pilot to follow a course of action to control attitude or thrust in a spe cific situation (for example, flight director). e. **Conformal** (AC 25 - 11A) **-** Refers to displayed graphic information that is aligned and scaled with the outside view. f. **Decision A**  **ltitude** (14 CFR 1.1) **-** A specified altitude in an instrument approach procedure at which the pilot must decide whether to initiate an immediate missed approach if the pilot does not see the required visual reference, or to continue the approach. Decision altitude is expressed in feet above mean sea level. g. **Decision H**  **eight** (14 CFR 1.1) **-** A specified height above the ground in an instrument approach procedure at which the pilot must decide whether to initiate an immediate missed approach if the pilot does not see the required visual reference, or to continue the approach. Decision height is expressed in feet above ground level. h. **Ego -**  **centric** - Used to define the view of a display image that correlates to inside the aircraft. One example is what the flight crew would see out the window from a forward facing perspective. i. **Enhanced Flight Visibilit y (EFV)**  (14 CFR 1.1) - The average forward horizontal distance, from the cockpit of an aircraft in flight, at which prominent topographicalMM/DD/YYYY AC 20 - 167A

A9 - 2 objects can be clearly

distinguished and identified by day or night by

a pilot using an enhanced flight vision sy ste m. j. **Enhanced Flight Vision System (EFVS)** (14 CFR 1.1) - An installed aircraft sy stem which uses an electronic means to provide a display of the forward external scene topograph y (the applicable natural or manmade features of a place or region especiall y in a way to show their relative positions and elevation) through the use of imaging sensors , such as forward looking infrared, millimeter wave radiometry , millimeter wave radar, and/or low light level image intensifying. The EFVS sensor imagery and required aircraft flight information and flight s ymbology is displayed on a head - up display , or an equivalent display , on which the imagery and s ymbology

is clearl y visible to the pilot flying is his or her normal position with the line of vision looking forward along the flight path. An EFVS includes the display element , sensors, computers and power supplies, indications, and controls. k. **Enhanced Vision System (EVS)** - An electronic means to provide a display of the forward external scene topography (the natural or manmade features of a place or region especiall y in a way

to show their relative positions and elevation) through the use of imaging sensors, such as a forward looking infrared, millimeter wave radiometry , millimeter wave radar, low light level image inten sifying. **Note 1:** EASA uses term “EVS” as equivalent to FAA description of “EFVS.” **Note 2:** Unlike an EFVS, an EVS does not necessarily provide the additional flight information/sy

mbology required by

14 CFR 91.17 6 , cannot use a head - up display or an equivalent display , and cannot be able to present the image and flight s ymbology in the same scale and alignment as the outside view. This sy stem can provide situation awareness to the pilot, but does not meet the regulatory requirements of 14 CFR 91.17 6 . As s uch, an EVS cannot be used as a means to determine enhanced flight visibility or to identify

the required visual references and descend below the minimum descent altitude (MDA) or decision height (DH). l. **Equivalent D isplay**  - Inthe context of 14 CFR 91.17 6 , a display which has at least the following characteristics:

1. A head - up presentation not requiring transition of visual attention from head down to head up.

2. Display s sensor - derived imagery conformal (as defined in SAE AS 8055) with the pilots external view.

3. Permits simultaneous view of the EFVS sensor imagery , required aircraft flight s ymbology , and the external view.

4. Display

characteristics and dy

namics are suitable for manual control of the aircraft. m. **Exocentric** - Used to define the view of a display image that correlates to outside the aircraft. One common exocentric view would be a North Up Plan view shown on moving map display s. n. **Eye Reference Point (ERP)** - The ERP is the point in the cockpit that allows for a finite reference enabling the precise determin ation of geometric entities that define the layout of the cockpit and displays.MM/DD/YYYY AC 20 - 167A

A9 - 3 o. **Field of Regard (FOR)** (SAE ARP 5677) - The angular extent of the external world that is represented on a display . p. **Field of View (FOV)** - The angular extent of the display that c an be seen by either pilot with the pilot seated at the pilot’s station. AC 25 - 11A provides the following diagram for primary

field of view. See Figure 4 below.

**Figure 4**  **. Field of View** q. **Flicker** (RTCA/DO - 315 A ) - High frequency luminance variations. r. **Flight Path Angle Reference Cue** - Pilot selectable reference cue on the pitch scale displaying the desired approach angle. s. **Flight Path Vector** - A sy mbol on the primary

display (HUD or PFD) that shows where the aircraft is actually goin g, the sum of all forces acting on the aircraft. t. **Flight Visibility** (14 CFR 1.1) - The average forward horizontal distance, from the cockpit of an aircraft in flight, at which prominent unlighted objects can be seen and identified by

day and prominent light ed objects can be seen and identified by night. u. **Head Up Display (HUD)** (AC 25.1329 - 1B) - A transparent optical display sy stem located level with and between the pilot and the forward windscreen. The HUD display s a combination of control, performance, navig ation, and command information superimposed on the external field of view. It includes the display element, sensors, computers and power supplies, indications and controls. It is integrated with airborne attitude, air data and navigation sy stems, and as a display of command information is considered a component of the flight guidance s ys tem. v. **IFR conditions** (14 CFR 1.1) - Weather conditions below the minimum for flight under visual flight rules.MM/DD/YYYY AC 20 - 167A

A9 - 4 w. **Instrument** (14 CFR 1.1) **-** A device using an internal mechanis m to show visually or aurall y the attitude, altitude, or operation of an aircraft or aircraft part. It includes electronic devices for automatically controlling an aircraft in flight. x. **Jitter** (RTCA/DO - 315 A ) - High frequency positional oscillations. y. **Latency** (AC 25 - 11A) - The time taken b y the display s ys tem to react to a triggered event coming from an input/output device, the sy mbol generator, the graphic processor, or the information source. z. **Minimum Descent A ltitude**  (14 CFR 1.1) - The lowest altitude, expre ssed in feet above mean sea level, to which descent is authorized on final approach or during circle - to - land maneuvering in execution of a standard instrument approach procedure, where no electronic glide slope is provided. aa. **Noise Equivalent Power (NEP)** - M easure of the sensitivity of an optical detector or detector s ys tem. bb. **Noise Equivalent Temperature Difference (NETD)**

– A measure of the sensitivity

of a detector of thermal radiation in the infrared, terahertz radiation, or microwave radiation parts of the electromagnetic spectrum. cc. **Non -**  **Uniformity Correction (NUC)** - Calibration of a detector utilizing more than one detector element. dd. **Precision Approach P rocedure**  (14 CFR 1.1) - A standard instrument approach procedure in which a precision lateral and vertical p ath is provided. ee. **Primary Flight Display (PFD)** - The display s used to present primary flight information. ff. **R ma**  **x .**  **-** T he maximum range the radar can detect. gg. **Situation Information** (AC 120 - 29 A , Criteria for Approval of Category Iand Category II Weather Minima f

or Approach ,) - Information that directly informs the pilot about the status of the aircraft system operations or specific flight parameters including flight path. hh. **Synthetic Vision** (14 CFR 1.1)

– A computer - generated image of the external scene topograph y from the perspective of the flight deck that is derived from aircraft attitude, high - precision navigation solution, and database of terrain, obstacles and relevant cultural features. ii. **Synthetic Vision System (SVS)** (AC 25.1329 - 1) - An electronic means to dis play a computer - generated image of the applicable external topography from the perspective of the flight deck that is derived from aircraft attitude, altitude, position, and a coordinate - referenced database. **Note:** “Topograph y” defined as maps or charts of natural and man - made features of a place or region especially in a way to show their relative positions and elevations, as applicable whenever deemed appropriate and practicable. jj. **Thermal C rossover**  - The natural phenomenon that normally occurs twice daily when temperature conditions are such that there is a loss of contrast between two adjacent objects on infrared imagery .MM/DD/YYYY AC 20 - 167A

A9 - 5 kk. **Threshold Crossing H eight (TCH)**  (Pilot/Controller Glossary) - The theoretical height above the runway

threshold at which the aircraft’s glideslope antenna would be if the aircraft maintains the trajectory established b y the mean ILS glideslope. ll. **Visual References** - Visual information the pilot derives from the observation of real - world cues, out the flight deck window, used as a primary ref erence for aircraft control or flight path assessment. **9 -**  **2. Acronyms.**  AC Advisory circular ACO Aircraft certification office AFM Aircraft flight manual BIT Built in test CVS Combined vision system DA Decision altitude DEM Digital elevation model DH Decis ion height DTED Digital terrain elevation data EASA European Aviation Safety Agency EFB Electronic flight bag EFIS Electronic flight instrument sy stem EFVS Enhanced flight vision system EMI Electromagnetic interference EVS Enhanced vision s ys tem FAA Federal Aviation Administration FHA Functional hazard anal ys is FLIR Forward looking infrared FMEA Failure mode and effects anal ys is FOR Field of regard FOV Field of view FTA Fault tree anal ys is HAT Height above touchdown HDD Head - down display HIRF High intensity radiated fields HMI Hazardously misleading information HTAWS Helicopter terrain awareness and warning s ys tem HUD Head - up display IFR Instrument flight rules ILS Instrument landing s ys tem MDA Minimum descent altitude MDH Minimum des cent height MFD Multi - function displayMM/DD/YYYY AC 20 - 167A

A9 - 6 ND Navigation display NETD Noise equivalent temperature difference NUC Non - uniformity correction PFD Primary flight display PI O Pilot Induced Oscillation RFM Rotorcraft flight manual RVR SSA Runway Visual Rang e Sy stem safety

anal ys is STC Sensitivity time control; supplemental ty pe certificate SVS Sy nthetic vision sy stem TAWS Terrain awareness and warning s ys tem TC Ty pe certificate TCH Threshold crossing height TDZE Touchdown zone elevationMM/DD/YYYY AC 20 - 167A

A10 - 1 **Appendix 10. Related Publications**  **10 -**  **1. Related Publications.**  a. FAA Documents: 1. Order 8110.4C, Ty pe Certification. 2. Order 8110.54 A , Instructions for Continued Airworthiness Responsibilities, Requirements, and Contents.

3. AC 23 - 18, Installation of Terrain Awareness and Warning S ystem (TAWS) Approved for Part 23 Airplanes.

4. AC 23.1309 - 1 E , Equipment, Sy stems, and Installations in Part 23 Airplanes. 5. AC 23 - 1311 - 1 C , Installation of Electronic Display Instrument Sy stems in Part 23 Airplanes.

6. AC 25 - 11A Electronic Flight Deck Display s. 7. AC 25 - 23, Airworthiness Criteria for the Installation Approval of a Terrain Awareness and Warning S ys tem (TAWS) for 14 CFR part 25 Airplanes.

8. AC 25.571 - 1 D Damage Tolerance and Fatigue Evaluation of Structure 9. AC 25.629 - 1A Aeroelastic Stability Substantiation o f Transport Category Airplanes . 10. AC 25.1309 - 1 A , Sy stem Design and Anal ys is.

11. AC 25.1329 - 1 B , Approval of Flight Guidance Sy stems. 12. AC 25.1523 - 1, Minimum Flight Crew. 13. AC 27 - 1B, Certification of Normal Category Rotorcraft. 14. AC 29 - 2 C , Certification of Transport C ategory Rotorcraft. 15. AC 90 - 106A Enhanced Flight Vision Sy stems 16. AC 91 - 16, Category II Operations General Aviation Airplanes. 17. AC 120 - 29 A , Criteria for Approval of Category Iand Category

II Weather Minima for Approach.

18. AC 120 - 57 A , Surface Movement Guidance an d Control System. 19. AC 120 - 76 B , Guidelines for the Certification, Airworthiness, and Operational Approval of Electronic Flight Bag Computing Devices.

20. FAA HUD, Certification Working Paper PS - ANM100 - 2001 - 0085. b. RTCA, Inc. DocumentsMM/DD/YYYY AC 20 - 167A

A10 - 2 1. DO - 160F, Environmental Condit ions and Test Procedures for Airborne Equipment. 2. DO - 178B, Software Considerations in Airborne Sy stems and Equipment Certification. 3. DO - 200A, Standards for Processing Aeronautical Data.

4. DO - 254, Design Assurance Guidance for Airborne Electronic Hardware. 5. DO - 2 76A, User Requirements for Terrain and Obstacle Data. 6. DO - 309, Minimum Operational Performance Standards (MOPS) for Helicopter Terrain Awareness and Warning S ys tem (HTAWS) Airborne Equipment.

7. DO - 315 A , Minimum Aviation System Performance Standards (MASPS) fo r Enhanced Vision Sy stems, Sy nthetic Vision Sy stems, Combined Vision Sy stems, and Enhanced Flight Vision Sy stems. c. SAE International Documents. 1. ARP 4101, Flight Deck Layout and Facilities. 2. ARP 4102, Flight Deck Panels, Controls and Display s. 3. ARP 4103, Flight Deck Lighting and Visual Interface. 4. ARP 4105, Nomenclature and Abbreviations for Use on the Flight Deck. 5. ARP 4754, Certification Considerations for Highly- Integrated Or Complex Aircraft Sy stems.

6. ARP 4761, Guidelines and Methods for Conducting the Safety Assessment Process on Civil Airborne Sy stems and Equipment

7. ARP 5288, Transport Category Airplane Head Up Display (HUD) Sy stems. 8. ARP 5589, Human Engineering Considerations for Design and Implementation of Perspective Flight Guidance Display s.

9. ARP 5677, Human Engineering Considerations for Cockpit Integration of Enhanced/S ynthetic Vision Sy stems.

10. AS 5703, Minimum Performance Standard for Enhanced Vision S ys tem. 11. AS 8055, Minimum Performance Standard for Airborne Head Up Display (HUD). **10 -**  **2. How to Get Publications.**  a. Order copies of 14 CFR, from the Superintendent of Documents, Government Printing Office, P.O. 979050, St. L ouis, MO 63197. For general information , telephone (202) 512 - 1800 or fax (202) 512 - 2250. You can order copies online at www.access.gpo.gov . Select “Access” then “Online Bookstore.” Select “Aviation,” then “Code of Federal Regulations.” b. You can get copies of FAA ACs from the FAA website at www.airweb.faa.gov or www.faa.gov/reugulations_policies/advisory _circulars/ .MM/DD/YYYY AC 20 - 167A

A10 - 3 c. You can find a current list of TSOs on the FAA Internet website Regulatory and Guidance Library

at www.airweb.faa.gov/rgl. You will also find the TSO Index of Articles at the same site. d. Order copies of RTCA documents from RTCA, Inc., 1150 18 th St., NW, Suite 910, Washington, DC 20036 , telephone (202) 833 - 9339, f ax (202) 833 - 943 4, or website: **www.rtca.org** e. Order copies of SAE documents from SAE World Headquarters, 400 Commonwealth Drive, Warrendale, PA 15096 - 0001, USA, telephone: (877) 606 - 7323, or website: http://www.sae.org . f. Order copies of military documents from the Department of Defense Index of Specifications and Standards (DODSSP), Building 4/Section D, 700 Robbins Avenue, Philadelphia, PA 19111 - 5098. Telephone (215) 697 - 2179, fax (215) 697 - 1462. Yo u can also order copies online at http://dodssp.daps.dla.mil