AC 20-191 automatic l anding and rollout sy stems) typically require the use of a high fidelity "fast-time" simulation.
5.4.5.2 For airworthiness certification credit, a review of the simulation, on a caseby-case basis, must address at least the following factors:
• Simulation fidelity relevant to landing system assessment;
• Stability derivatives, equation of motion assumptions, and relevant ground effect and air and ground dynamic models used ;
• Adequacy of the source of aerodynamic performance and handling quality data used;
• Disturbance input method(s) and fidelity ;
• Environmental models and methods of model input to the equations of motion, including suitable incorporation of altitude and atmospheric temperature effects;
• Adverse weather models (e.g., turbulence, wind gradients, wind models); and
• Adequacy of irregular terrain models.
5.4.5.3 Fidelity of the aerodynamic model is needed for at least ground effect, propulsion effects, touchdown dynamics, de-rotation, and landing gear models if required for ground rollout characteristics. The fidelity of the simulator may be demonstrated using matching time histories obtained from flight test. The data provided to validate the simulation and the simulation data itself will be included as part of the type certification data package.
5.4.6 Flight Test Performance Demonstration .
The applicant should conduct a flight test performance demonstration in part, to confirm the results of simulation. A test aircraft equipped with special instrumentation can be used to record the necessary flight test data, for subsequent correlation of flight test results with simulation results. Comparisons should address flight test data, "Monte Carlo simulation" results, and failure demonstration simulation results.
5.4.6.1 The principal performance parameters the applicant must address include, as applicable:
• Vertical and lateral flight path tracking with respect to the intended path
(e.g., LOC error, GS error, lateral deviation, GLS path deviation error, from runway centerline during rollout);
• Altitude and height above terrain during approach or the runway;
• Air data vertical speed and radar altitude sink rate;
• Airspeed and ground speed; and
• Longitudinal and lateral runway touchdown point.
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AC 20-191
5.4.6.2 Ins trumentation capable of appropriate sample rates and scaling should be used to record relevant parameters (as a function of time, when applicable) including:
• Air data parameters (e.g., airspeed, angle of attack, temperature);
• Aircraft position; attitude; heading;
• Track; velocity and velocity errors (e.g., ground speed, speed error), relevant accelerations;
• Pilot control inputs and resulting surface positions, command information (i.e., flight director), sink rate at touchdown (for structural limit load);
• Drift angle at touchdown (for gear/tire load);
• Applicable mode and mode transition information (e.g., flare, autothrottle/autothrust retard, rollout engage);
• Wind as measured at the aircraft;
• A method to determine any unusual aircraft contact with the runway
(e.g., wing, nacelle, or tail skid ground contact); and
• Reported surface winds and gusts near the runway, at the time of approach and landing.
5.4.6.3 Data taken during demonstration flight tests should be used to validate the simulation(s). Unless otherwise agreed to by the FAA, the objective of a flight test program should be to demonstrate performance of the system to 100% of the steady state wind limit values (e.g., typically at least a 25 kt headwind, 15 kt crosswind, and 10 kt tailwind) that are used in the simulation statistical performance analysis. The simulation is considered validated if at least four landings are accomplished during flight test at no less than 80% of the intended limit steady state wind value, and a best effort has been made to achieve the full steady state wind component values. The landing system must be robust near the desired AFM wind demonstrated values.
5.4.7 Demonstration of Approach and Automatic Landing with an Inoperative Engin e.
5.4.7.1 When an applicant demonstrates the low visibility landing system with an inoperative engine, the AFM may state that capability was satisfactorily demonstrated. With the critical engine inoperative, the applicant may demonstrate the capability to “initiate” and complete the approach and landing. Alternatively, the applicant may demonstrate the capability to “continue” the approach and landing following failure of the critical engine at any point above the AH or DH.
5.4.7.2 The applicant should identify the critical engine, if any, considering any steady state or transient effects on performance, handling, loss of systems, 5-43
AC 20-191 and landing mode status (e.g., a lignment, flare, rollout). Individual engines may be critical for different reasons.
5.4.7.3 If the aircraft configuration, procedures or operation are the same as those used in section 5.2.9 for all-engine operation performance demonstration, compliance may be demonstrated by 10 to 15 landings. If there are differences in these aircraft configurations, procedures or operations, the number of required landings will be determined by FAA on a case-by-case basis.
5.4.7.4 If the aircraft configuration, procedures or operation is changed significantly from the all-engine operating case, the applicant must demonstrate compliance by statistical analysis or Monte-Carlo simulation results supported by flight test. Any effect on configuration or landing distance must be considered.
5.4.7.5 To aid planning for landing with an inoperative engine or engine failure during approach or go-around, appropriate procedures, performance, and obstacle clearance information should be available to permit an operator to conduct a safe go-around at any point in the approach to touchdown. For the purposes of this performance provision, demonstration or data regarding landing and go-around performance in the event of a second engine failure need not be considered.
5.4.7.6 If compliance for the case of initiation or continuation of an approach with engine failure is intended, a statement must be included in the non-normal procedures or equivalent section of the flight manual.
5.4.7.7 The flight manual should note that approach and automatic landing with an engine inoperative has been satisfactorily demonstrated. The AFM should list the relevant configuration and conditions under which that demonstration was made.
5.4.8 Safety Assessment.
In addition to any specific safety related criteria identified in this chapter, the applicant must conduct a safety assessment of the landing and rollout system, considered separately and in conjunction with other systems, to show compliance with §§ 23.2500,
23.2510, 23.2605, 25.1309, 27.1309, or 29.1309 per the guidance contained in AC 23.1309-1, AC 25.1309-1, AC 27-1, or AC 29-2, as applicable.
5.4.8.1 The applicant must consider the responses to failures of navigation facilities.
The applicant must take into account ICAO and other pertinent State criteria for navigation facilities.
5.4.8.2 Documented conclusions of the safety analysis must include:
5.4.8.2.1 Pursuant to §§ 23.2500, 23.2510 and 23.2605, 25.1309,
27.1309, or 29.1309, an FHA conducted in accordance with 5-44
AC 20-191 AC 23.1309-1, A C 25.1309-1, AC 27-1, or AC 29-2, respectively; a summary of results from the fault tree analysis, demonstrated compliance, and probability determination for significant functional hazards.
5.4.8.2.2 Information regarding "alleviating flight crew actions" that were considered in the safety analysis. This information should list appropriate alleviating actions, if any, and should be consistent with the validation conducted during testing. If alleviating actions are identified, the applicant should describe the alleviating actions in a form suitable to aid in developing, as applicable:
• Pertinent provisions of the AFM procedures section(s).
• FCOM provisions, or equivalent.
• Pilot qualification criteria (e.g., training requirements, FSB provisions).
• Any other reference material necessary for an operator or flight crew to safely use the system.
5.4.8.2.3 Information to support preparation of any maintenance procedures necessary for safety such as:
• CMRs.
• Periodic checks.
• Other checks, as necessary (e.g., return to service).
5.4.8.2.4 Information applicable to lim itations, as necessary.
5.4.8.2.5 Identification of applicable syste ms, modes, or equipment necessary for use of the landing syste m. This information may be used to aid in development of flight planning , dispatch criteria, or procedures or checklists for pilot selection of modes or assessment of system status, prior to initiation of approach or during approach.
5.4.8.2.6 Information necessary for development of Non-normal procedures.
5.4.9 Continued Airworthiness.
5.4.9.1 Pursuant to §§ 23.1529, 25.1529, 27.1529, or 29.1529, an applicant must prepare an ICA for use by operators. The applicant must submit to the FAA a program showing how the applicant distributes changes made to the ICAs by the applicant or by the manufacturers of the ILS or GBAS avionics 5-45
AC 20-191 installed in the aircraft. ICAs established during the approval process form th e basis for an operator’s maintenance program.
5.4.9.2 Pursuant to 14 CFR §§ 21.3, the applicant must report any failure, malfunctions or defect whose occurrences could impact the safety of the flight crew or the structural integrity of the aircraft itself.
5.5 Aircraft Flight Manual.
Pursuant to 14 CFR §§ 23.2620, 25.1581, 27.1581, or 29.1581, as applicable, an applicant must furnish AFM with each aircraft. The AFM should contain the following information: Upon satisfactory completion of an airworthiness assessment and test program, the FAA-approved AFM or supplement, and any associated markings or placards, if appropriate, should be issued or amended to address the following:
5.5.1 Relevant conditions or constraints applicable to landing or landing and rollout system use regarding the airport or runway conditions. For example:
• Runway elevation
• Ambient temperature
• Approach path slope
• Runway slope
• Ground profile under the approach path
5.5.2 The criteria and configurations used for the demonstration of the system.
5.5.3 Any constraints or limitations necessary for safe operation.
5.5.4 Acceptable normal and non-normal procedures (including procedures for response to loss of guidance).
5.5.5 The type of navigation facilities used as a basis for demonstration. This should not be taken as a limitation on the use of other facilities. The AFM may contain a statement regarding the type of facilities or condition known to be unacceptable for use (e. g., ILS or GLS systems). The AFM should indicate that operation is predicated upon the use of an ILS (or GLS) facility with performance and integrity equivalent to, or better than, a United States Type II or Type III ILS, GBAS GAST D or equivalent ICAO Annex 10 Facility Performance Category III facility.
5.5.6 Applicable atmospheric conditions under which the system was demonstrated (e.g., headwind, crosswind, tailwind) should be described as follows:
5.5.6.1 In the limitations section, the wind component values used as a basis for statistical analysis, as supported by flight evaluation and validation, which 5-46
AC 20-191 may apply to use of the landing system, such as if credit for use is sought for low visibility operations,
5.5.6.2 In the normal operations section, or equivalent section, maximum wind component values experienced during the flight demonstration, described as "Demonstrated Wind Component(s),"
5.5.6.3 For use of the landing system other than for low visibility credit (e.g., in wind or other conditions where system performance may not necessarily be supported by the statistical analysis), any necessary description of considerations, if other than the maximum demonstrated wind component values for the basic aircraft apply.
Note: The FAA does not apply a "landing system" wind limitation unless unacceptable system characteristics dictate use of a limitation. This is consistent with specification of the demonstrated wind component value for the basic aircraft, which is included in the AFM for information, and is not limiting.
5.5.7 For a landing or landing and rollout system meeting provisions of this chapter, the normal procedures, normal operations, or equi valent section, of the AFM should also contain the following statements:
"The airborne system has been demonstrated to meet the airworthiness provisions of AC 20-191 Chapter 5 for [specify the pertinent Landing or Landing and Rollout Capability Section(s) criteria met] when the following equipment is installed and operative:
[list pertinent equipment] "This AFM provision does not constitute operational approval for Category III use of this system."
5.5.8 The AFM provisions:
• May list the AH demonstrated AH;
• Should not include visual segment specifications.
Examples of general AFM considerations, specific AFM provisions, and location of those provisions for applicable landing or landing and rollout systems are in Appendix D.
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AC 20-191 Appendix A APPENDIX A. DEFINITIONS AND ACRONYMS A.1 This appendix contains the acronyms and definition of terms used within this AC. The appendix also contains certain terms that are not used in this AC but are used in related ACs and are included for convenient reference. Certain acronyms and definition of terms are also provided to facilitate common use of this appendix for other related ACs.
Where the definitions or acronyms in this Appendix differ from their definition or meaning in 14 CFR, these definitions or acronyms are for the purposes of, and only applicable to, this AC.
A.1.1 Acronyms.
• AC Advisory Circular
• ACJ Advisory Circular Joint (EASA)
• ADI Attitude Director Indicator
• AFM Aircraft Flight Manual
• AH Alert Height
• APU Auxiliary Power Unit
• ATS Air Traffic Service
• AWO All Weather Operations
• BITE Built-In Test Equipment
• CFR Code of Federal Regulations
• CMR Certification Maintenance Requirements
• DA Decision Altitude
• DA(H) Decision Altitude (Height)
• DH Decision Height
• DOD Department of Defense
• EADI Electronic Attitude Director Indicator
• EASA European Union Aviation Safety Agency
• EFVS Enhanced Flight Vision System
• EMC Electromagnetic Compatibility
• EMI Electromagnetic Interference
• EVS Enhanced Vision System
• FAF Final Approach Fix
• FAS Final Approach Segment A-1
AC 20-191 Appendix A
• FCOM Flight Crew Operating Manual
• FDR Flight Data Recorder
• FGS Flight Guidance System
• FHA Functional Hazard Assessment
• FM Frequency Modulation
• FMC Flight Management Computer
• FMS Flight Management System
• FPAP Flight Path Alignment Point
• FPCP Flight Path Control Point
• FSB Flight Standardization Board
• FTE Flight Technical Error
• GAST GBAS Approach Service Type
• GBAS Ground Based Augmentation System
• GIRP Glidepath Intercept Reference Point
• GLS GBAS Landing System
• GNSS Global Navigation Satellite System
• GPA Glide Path Angle
• GPIWP Glide Path Intercept Waypoint
• GPS Global Positioning System
• HAT Height Above Touchdown
• HQRS Handling Quality Rating System
• HUD Head Up Display
• IAP Instrument Approach Procedure
• ICAO International Civil Aviation Organization
• ILS Instrument Landing System
• IM ILS Inner Marker
• IMC Instrument Meteorological Conditions
• IRS Inertial Reference System
• IRU Inertial Reference Unit
• ISA International Standard Atmosphere
• LNAV Lateral Navigation A-2
AC 20-191 Appendix A
• L OC ILS Localizer
• MAP Missed Approach Point
• MDA Minimum Descent Altitude
• MLS Microwave Landing System
• MMR Multi-mode Receiver
• MSL Mean Sea Level [altitude reference datum]
• NAVAID Navigational Aid
• NOTAM Notice to Airmen
• PF Pilot Flying
• PFD Primary Flight Display
• QNH Altimeter Setting referenced to airport ambient local pressure
• RDP Runway Datum Point
• RMS Root-mean-square
• RNAV Area Navigation
• RNP Required Navigation Performance
• RPDS Reference Path Data Selector
• RPI Runway Path Identifier
• RVR Runway Visual Range
• SARPs Standards and Recommended Practices (ICAO)
• STC Supplemental Type Certificate
• TC Type Certificate
• TSE Total System Error
• V1 The maximum speed in the takeoff at which the pilot must take the first action (e.g., apply brakes, reduce thrust, deploy speed brakes) to stop the airplane within the accelerate-stop distance. V1 also means the minimum speed in the takeoff, following a failure of the critical engine at VEF, at which the pilot can continue the takeoff and achieve the required height above the takeoff surface within the takeoff distance.
• VDB VHF Data Broadcast
• VFAILURE Speed at which failure occurs
• VHF Very High Frequency
• VMC Visual Meteorological Conditions
• VMCG Ground Minimum Control Speed A-3
AC 20-191 Appendix A
• VNA V Vertical Navigation
• WGS-84 World Geological Survey - 1984 A.2 Definitions of Terms.
Term Definition A measure of the current estimated navigation performance,
• Actual excluding Flight Technical Error (FTE). Actual Navigation Navigation Performance is measured in terms of accuracy, integrity, and Performance availability of navigation signals and equipment.
The airborne equipment that senses and computes the aircraft position
• Airborne relative to the defined path, and provides information to the displays Navigation and to the flight guidance system. It may include a number of System receivers or system computers such as a Flight Management Computer (FMC) or both and typically provides inputs to the Flight Guidance System.
A height above the runway based on the characteristics of the aircraft
• Alert Height and its fail-operational landing system, above which a Category III approach would be discontinued and a missed approach initiated if a failure occurred in one of the redundant parts of the fail operational landing system, or in the relevant ground equipment (Manual for All Weather Operations, ICAO Doc. 9365).
• Automatic A go-around that is accomplished by an autopilot following pilot Go-Around selection and initiation of the go-Around autopilot mode, when an autopilot is engaged in an approach mode.
• Availability An expectation that systems or elements required for an operation will be available to perform their intended functions so that the operation will be accomplished as planned to an acceptable level of probability.
• Balked A discontinued landing attempt. This term is often used in Landing conjunction with aircraft configuration or performance assessment, as in “Balked landing climb gradient,” Also, see “Rejected Landing.”
• Category II A precision instrument approach operation with a DH lower than 150 (FAA) ft (45m) but not lower than 100 ft (30m) and a runway visual range not less than 300m (1000 ft).
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AC 20-191 Appendix A Term D efinition
• Category II A Type B instrument approach operation to a DH lower than 60 m (ICAO) (200 ft), but not lower than 30 m (100 ft) and a runway visual range not less than 300 m (1000 ft).
• Category III A precision instrument approach or approach and landing with a (FAA) decision height lower than 100 ft (30m), or no decision height, or a runway visual range less than 1000ft (300m).
• Category III A Type B instrument approach operation to a DH lower than 30 m (ICAO) (100 ft) or no DH and a runway visual range not less than 1000ft (300m) or no RVR limitations.
• Combiner The element of the head up display (HUD) in which the pilot simultaneously views the external visual scene along with synthetic information provided in symbolic form.
• Command Information that directs the pilot to follow a course of action in a Information specific situation (e.g., information provided by a flight director).
• Conformal Information that correctly overlays the image of the real world, Information irrespective of the pilot’s viewing position.
• Contaminated A runway is considered contaminated when more than 25 % of the Runway runway surface area (within reported length and width being used) is covered by standing water (greater than 1/8 inch or 3 mm), frost, ice, and any depth of snow, slush, or heavy rubber deposits.
• Decision A specified altitude in an instrument approach procedure at which the Altitude (DA) 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.
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AC 20-191 Appendix A Term D efinition
• Decision For Category II and certain Category III procedures (e.g., when using Altitude a Fail Passive autoflight system), the DH (or an equivalent IM (Height) position fix) is the controlling minima, and the altitude value DA(H)) specified is advisory. The altitude value is available for cross reference. Use of a barometrically referenced DA for Category II is not currently authorized for 14 CFR Parts 121, 129, or 135 operations at U.S. facilities (Adapted from ICAO - IS&RP Annex 6).
• Decision A specified height above the ground in an instrument approach Height (DH) 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.
• Defined Path The path that is defined by the path definition function.
• Design Eye The three-dimensional volume in space surrounding the Design Eye Box Position from which the HUD information can be viewed.
• Design Eye The position at each pilot’s station from which a seated pilot achieves Position the optimum combination of outside visibility and instrument scan.
• Desired Path The path the flight crew and air traffic control can expect the aircraft to fly.
• Enhanced An installed aircraft system which uses an electronic means to Flight Vision provide a display of the forward external scene topography (the System 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, including but not limited to forward-looking infrared, millimeter wave radiometry, millimeter wave radar, or lowlight level image intensification. An EFVS includes the display element, sensors, computers and power supplies, indications, and controls.
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