troubleshooting, cleaning, maintenance procedures for the MEL relief and software loading/configuration control. Special consideration should be taken to consider the maintenance of databases used for SVGS operations and the impact of installed databases that have expired. The FAA will evaluate alternative methods consistent with the FAA’s safety continuum.
4.3 ASA-SVS General Criteria and Performance Standards.
4.3.1 RTCA DO-371 section 2 provides general standards for ASA-SVS. RTCA DO-371 Section 3 provides minimum performance standards.
4.3.2 In addition to meeting the criteria of RTCA DO-371, the ASA-SVS should also meet all the criteria for a SVS found in section 4.1 of this AC.
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CHAPTER 5. PERFORMANCE EVALUATION
5.1 SVS Performance Evaluation
5.1.1 Performance demonstration. Establishing aircraft system compliance with applicable FAA regulations typically includes bench testing, simulation flight testing, data collection, and data reduction to show that the proposed performance criteria can be met. Minimum performance standards necessitate an evaluation of the system used during anticipated operational scenarios. The performance evaluations should therefore include demonstrations of taxi, take-off, missed approaches, failure conditions, cross wind conditions, and approaches into specific airports as appropriate for the system’s intended function.
5.1.2 This AC does not prescribe specific test procedures. The FAA recognizes that alternative methods can be used. Your test procedures must show compliance with the applicable regulations. System performance tests as they relate to operational capability are the most important tests. Subsystem tests are used to test subsystems during system buildup to ensure appropriate subsystem performance as it relates to overall system performance.
5.1.3 The applicant should use any of these four general verification methods as appropriate (refer to AC 25.1329-1C, AC 23.1309-1E, AC 27-1B, or AC 29-2C, as applicable):
5.1.3.1 Analysis. Demonstrate compliance using an engineering analysis.
5.1.3.2 Flight Test. Demonstrate compliance using an aircraft that is fully representative for the purpose of the test in terms of flight deck geometry, instrumentation, alerts, indications, and controls (in the air or on the ground).
5.1.3.3 Laboratory Test. Demonstrate compliance using an engineering bench representative of the final SVS/SVGS/ASA-SVS system being certified.
5.1.3.4 Simulation. Demonstrate compliance using a flight simulator.
5.1.4 The applicant should specify the individual verification methods in the certification plan. Confirm the appropriate certification office agrees with your plan before you begin. For extensions, features, and design decisions not explicitly specified in this AC, conduct human factors evaluations. Conduct these evaluations through analyses, bench, simulation, and/or flight testing, as appropriate.
5.1.5 The applicant should verify both the installed system and the individual system components meet the SVS criteria described in Chapter 4.
5.1.6 The applicant should demonstrate the system meets the performance criteria specified in Chapter 4 by flight test and other appropriate means, which can include use of a flight simulator. The flight test program assumes that the guidance system utilized to 5-1
satisfactorily position the aircraft has been separately tested and shown to fully perform its intended function. Testing and data collection to demonstrate this is not part of this document.
5.1.7 Airframe and equipment manufacturer based tests or analyses, as applicable, should be developed and conducted to validate the detailed system criteria. No specific test 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.
System performance tests as they relate to operational capability are the most important tests. Subsystem tests are added during system buildup to ensure appropriate subsystem performance as it relates to overall system performance.
5.1.8 The applicant should conduct an evaluation of the system used during anticipated operational scenarios.
5.2 SVGS Performance Evaluation
5.2.1 RTCA DO-359 section 4 provides system performance verification criteria.
5.2.2 In addition to the test conditions listed in DO-359 section 4.2.2, the applicant should also demonstrate their system in representative day and night VMC.
5.2.3 Where appropriate for the performance demonstration, the non-visual conditions can be achieved either by natural obscuration or by use of a visibility limiting device in front of the pilot.
5.2.4 The use of a simulator can be considered, provided the simulator was assessed to adequately conform with respect to the aircraft and the SVGS performance, and was assessed to be suitable for the required task.
5.2.5 The workload associated with using the SVGS to fly instrument approaches to a missed approach point of 150 feet HAT should be considered when showing compliance with 14 CFR 23.2610, 25.1523, 27.1523, 29.1523, and meeting the provisions of AC
23.1523, AC 25.1523, AC 27-1B, AC 29-2C as applicable to the aircraft in which the SVGS is being installed. The FAA will evaluate alternative methods consistent with the FAA’s safety continuum.
5.3 ASA-SVS Performance Evaluation RTCA DO-371 section 4 provides system performance verification criteria.
5.4 Preventive Maintenance.
Incorporate all appropriate maintenance requirements into the Instructions for Continued Airworthiness pursuant to 14 CFR 23.1529, 25.1529, 27.1529, or 29.1529, as applicable. The FAA will evaluate alternative methods consistent with the FAA’s safety continuum.
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5.5 Environmental Testing.
Follow the guidance in AC 21-16G, RTCA Document DO-160 versions D, E, F, and G, “Environmental Conditions and Test Procedures for Airborne Equipment.”
5.6 Design Assurance.
5.6.1 Sections 23.2500, 25.1309, 27.1309, and 29.1309 require applicants to design systems to ensure they perform their intended function. The applicant should use the guidance provided in the following ACs when accomplishing their system safety assessment and showing compliance with the above regulations as applicable.
x AC 20-174, Development of Civil Aircraft and Systems x AC 23.1309-1E, System Safety Analysis and Assessment for Part 23 Airplanes x AC 25.1309-1A, System Design and Analysis x AC 27-1B, Certification of Normal Category Rotorcraft x AC 29-2C, Certification of Transport Category Rotorcraft
5.6.2 Follow the guidance in AC 20-115D, Airborne Software Development Assurance Using EUROCAE ED-12() and RTCA DO-178() to develop software. The version should be current at time of application.
Follow the guidance in AC 20-152, RTCA, Inc., Document RTCA/DO-254, Design Assurance Guidance for Airborne Electronic Hardware, to develop your airborne electronic hardware, if applicable. The version should be current at time of application.
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____________________ Appendix A APPENDIX A. SAMPLE AIRPLANE FLIGHT MANUAL (AFM) SUPPLEMENT Note: Appendix A presents a sample for the AFM supplement for STC installations. This example may not be entirely applicable to airplane manufacturers when SVS, SVGS, or ASA- SVS are approved with the type certificate. The ACO will assist the applicant in developing an appropriate Rotorcraft Flight Manual Supplement (RFMS).
Installation Center/Repair Station Model XXX SVS/SVGS/ASA-SVS 123 Fourth Street Vision System Anytown, USA
FAA-APPROVED AIRPLANE FLIGHT MANUAL SUPPLEMENT
ABC MODEL XXX YYY VISION SYSTEM AIRPLANE MAKE:
AIRPLANE MODEL:
AIRPLANE SERIAL NO.:
REGISTRATION NO.:
This document must be carried in the airplane at all times. It describes the operating procedures for the ABC Model XXX YYY vision system when it has been installed in accordance with <manufacturer'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> only in those areas listed herein. For limitations, procedures, and performance information not contained in this document, consult the basic Airplane Flight Manual.
FAA APPROVED Title Office Federal Aviation Administration City, State A-1
01/27/21 SAMPLE AIRPLANE FLIGHT MANUAL (Continued) AC 20-185A Appendix A Installation Center/Repair Station Model XXX SVS/SVGS/ASA-SVS 123 Fourth Street Vision System Anytown, USA Table of Contents
SectionPage
1 General.............................................< > 2 Limitations........................................< > 3 Emergency/Abnormal Procedures....< > 4 Normal Procedures...........................< > 5 Performance......................................< > 6 Weight and Balance..........................< > 7 System Description...........................< > FAA Approved Page <> of <> Date: ________ A-2
Appendix A SAMPLE AIRPLANE FLIGHT MANUAL (Continued) Installation Center/Repair Station Model XXX SVS/SVGS/ASA-SVS 123 Fourth Street Vision System Anytown, USA SECTION 1 - GENERAL <Include the appropriate statement to describe the equipment capability:> SVS: The installed ABC Synthetic Vision System meets the FAA-accepted general criteria and performance standards specified in AC 20-185A for <situation awareness>.
SVGS: The installed SVGS meets the general criteria and performance standards specified in AC 20-185A for SVGS to be used for instrument landing system (ILS) approaches with a DH no lower than 150 feet HAT.
ASA-SVS: The installed ABC ASA-SVS meets the general criteria and performance standards specified in AC 20-185A for <situation awareness>.
SECTION 2 - LIMITATIONS
1. The system must utilize software version <insert version identification>.
2. Valid and compatible databases must be installed and contain current data. <The terrain, runway, and obstacle database requirements must support the intended function applicable to the particular installation.>
3. The <Insert model specific identification of the SVGS installed> meets the general criteria and performance specified in AC 20-185A, Airworthiness Approval of Synthetic Vision System, Synthetic Vision Guidance System and Aircraft State Awareness Synthetic Vision System.
However, this does not constitute operational approval for use.
4. <Specify any additional limitations applicable to the particular installation.> FAA Approved Page <> of <> Date: ________ A-3
Appendix A SECTION 3 - EMERGENCY/ABNORMAL PROCEDURES
EMERGENCY PROCEDURES No Change
ABNORMAL PROCEDURES
1. If ABC Model XXX YYY vision system 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 periodically cross-check the GPS guidance to other, approved means of navigation.
SECTION 4 - NORMAL PROCEDURES
1. Normal operating procedures are outlined in the ABC Model XXX YYY Pilot's Guide.
2. System Annunciators <applicable to installations with external annunciators>.
3. System Switches <applicable to installations with external switches>.
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: ________ A-4
Appendix A SECTION 5 - PERFORMANCE No Change SECTION 6 - WEIGHT AND BALANCE <Refer to revised weight and balance data, if applicable.> SECTION 7 - SYSTEM DESCRIPTION <Provide a brief description of the system, its operation, installation, etc.> FAA Approved Page <> of <> Date: ________ A-5
Appendix B APPENDIX B. SYNTHETIC VISION SYSTEMS INSTALLED IN ROTORCRAFT B.1 General.
This appendix provides guidelines for the installation of SVS in rotorcraft as nonrequired safety enhancing equipment. To promote standardized installation of nonrequired safety enhancing equipment, a policy memorandum, PS-ASW-27, 29-10, Policy Statement Concerning Non-Required Safety Enhancing Equipment (NORSEE) in Rotorcraft, dated 5/29/2013, was published to address a means of compliance for the installation of non-required safety enhancing equipment. Contact your ACO for guidance. Also, refer to AC 27-1B and AC 29-2C for certification guidance.
B.2 Applicability.
There are unique aspects to rotorcraft that do not apply to fixed wing aircraft. Rotorcraft typically operate at altitudes much closer to the ground and obstacles than fixed-wing aircraft. Additionally, they are inherently unstable and, without a stabilization system, require hands-on control at all times accompanied by constant visual scans to keep the rotorcraft oriented correctly. There are advantages and disadvantages to presenting 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 (particularly in night operations), and the installation of SVS displays that interact with automated flight control systems and flight guidance systems.
B.3 Airworthiness Approval.
For rotorcraft, the applicant should accomplish all SVS/SVGS/ASA-SVS installations on the primary flight display (PFD) or navigation display through the TC/STC/ATC process.
B.4 Design Considerations.
The functional hazard analysis (FHA) developed for the system should define the hazards of presenting misleading information to the pilot, and loss of an SVS feature.
The system should be designed accordingly. The hazard classification will be based on display location, intended function of the system features, and phase of flight. The hazard classification of misleading information for SVS on the primary flight displays 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 is placed on ancillary displays not used for the display of flight information and not in the pilot’s primary field of view. The intended function of the SVS/SVGS/ASA-SVS should be defined as it specifically applies for the rotorcraft application. If HTAWS or HTAWS-like features are incorporated, see TSO- C194 HTAWS, AC 27-1B, or AC 29-2C, MG-18 as appropriate for additional criteria.
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Appendix C APPENDIX C. ADDITIONAL CONSIDERATIONS FOR SYNTHETIC VISION SYSTEM
USED FOR SITUATION AWARENESS ONLY C.1 Terrain Alerting.
Any airplane equipment incorporating a synthetic vision system should also provide some type 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. Synthetic vision systems on the PFD should provide adequate altitude and distance cues if used for terrain warning.
Applicants may use TSO-C151d, TAWS, Class A, B, or C, or TSO-C194 standards as applicable. Applicants may develop their own terrain warning system. However, the option of developing a terrain warning system 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 system should include:
x A one-minute caution and 30-second warning if the airplane’s current flight path will collide with terrain.
x A 20 second caution and 10 second warning if the rotorcraft’s current flight path will collide with terrain.
x Aural call-out for both the caution and the warning (CAUTION – TERRAIN, TERRAIN; WARNING – TERRAIN, TERRAIN).
x Terrain impact region highlighted on the moving map.
x A safety margin or buffer of at least 100 feet for cumulative errors in both the GPS altitude and terrain database.
x A terrain database/digital evaluation model (DEM) developed using the criteria in RTCA DO-200B, Standards for Processing Aeronautical Data, dated June 18, 2015.
x The synthetic 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.
C.2 Moving Map Display that Corresponds to and Complements Synthetic Vision PFD Display.
If there is a second complementary map view display, the second display should depict the same terrain, obstacles, or cultural features that appear on the PFD’s synthetic vision display in a consistent manner and not cause confusion to the crew when comparing the same feature across displays. This display could be on the navigation display, but also be an MFD or a third separate display. Ideally, the TAWS or HTAWS or terrain alerting C-1
Appendix C system should be part of this display (unless incorporated into the PFD) so that hazardous terrain or obstacles are highlighted.
C.3 Minimums Audio Callout Capability.
Applicants are encouraged to incorporate either a pilot selectable or automatic altitude alert with audio callout to remind pilots they are approaching minimums. Pilots may “see” the runway environment on their synthetic vision display and continue below minimums inadvertently because they were so intent on following the approach guidance. This scenario is similar 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.
C.4 Digital Evaluation Model (DEM) Resolution.
The DEM resolution is one factor that determines how well the synthetic vision terrain depiction will match the terrain environment. National Aeronautics and Space Administration (NASA) experiments, documented in NASA/TP-2008-215130, Aspects of Synthetic Vision Display Systems and Best Practices of the NASA’s SVS Project and NASA/TP-2007-214864, Terrain Portrayal for Synthetic Vision Systems Head-Down Displays Evaluation Results, have shown that a terrain resolution of 30 arc-seconds (with arc-seconds referenced to an equatorial measurement) “rounds off” the terrain peaks and fills in valleys. This makes the terrain appear less hazardous for the peaks than it is and potentially reduces some safety benefit. Conversely, for the valleys, the terrain appears higher and its depiction 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 synthetic vision display using a 30 arcsecond database could provide more situation awareness (and, therefore, safety) than the conventional instrument panel. Therefore, we had historically considered 30 arcsecond resolution the minimum safety standard for synthetic vision displays. This allowed for the introduction of synthetic vision systems given the technology limitations. However, technology has surpassed the need to allow as low a minimum resolution. New systems should meet 15 equatorial arc-seconds or better. Current systems 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 consider using very high-resolution databases near airports while reducing the resolution in the rest of the database. However, for systems intended to support low altitude operations, for example helicopter operations, the use of high-resolution databases for all phases of flight might be more appropriate. More importantly, applicants should clearly define the resolution and measuring units of the DEM used by their synthetic vision system in the Aircraft Flight Manual Supplement (AFMS) and the pilots’ handbooks so that pilots can understand any visual limitation caused by resolution limits.
Note: The DEM resolution needed on a synthetic 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 synthetic vision C-2