AC 20-191 Appendix C
• RTCA/DO-253D, "Minimum operational Performance Standards for GPS Local Area Augmentation Airborne Equipment".
• RTCA / DO-253C, Minimum Operational Performance Standards (MOPS) for GPS Local Area Augmentation System (LAAS) Airborne Equipment.
• T. Murphy, M Harris, C. Shively, L. Azoulai , M. Brenner "Fault Modeling for GBAS Airworthiness Assessments", Proceedings of the Institute of Navigation Global Navigation Satellite System Conference, 2010.
• Use of GNSS signals and their augmentations for civil Aviation Navigation during Approaches with Vertical Guidance and Precision Approaches – PhD Thesis P. Neri – 2011.
C.4 Acronyms and Definitions for GBAS Performance Model.
• Bj,vert Estimate of the vertical error due to a fault of the jth reference receiver
• ECEF Earth-Centered, Earth Fixed coordinate system
• EL Lateral Error
• EMAX Peak error magnitude
• EV Vertical error
• GERP GBAS Elevation Reference Point
• GRP GLS Reference Point
• GW Lateral distance between the main landing gear
• GWN Gaussian White Noise
• Gx Compensation gain
• H(s) Second order Butterworth filter that is implemented in the GBAS NSE generator
• Katrk NSE geometry scale factor – along track
• Kvert NSE geometry scale factor – vertical track
• Kxtrk NSE geometry scale factor – cross-track
• LAL Lateral Alert Limit
• LLC Land Long Criteria
• LP Lateral Protection Level
• LSC Land Short Criteria
• LTP Landing Threshold Point
• M Number of GNSS reference receivers C-23
AC 20-191 Appendix C
• maxEL User specified maximum allowable lateral position error
• maxEV User specified maximum allowable vertical position error
• Pmd Probability of missed detection
• pTSE_LATE(x,E) P robability density function for the lateral touchdown given a bias of magnitude E
• pTSE_LONE(x,E) Probability density function for the longitudinal touchdown given a bias of magnitude E
• Pmd (E) Probability of an error not being detected as a function of E
• PU (E) Probability of an unsuccessful landing given an error
• PULE (E) Probability of an unsuccessful landing given a particular size of error
• RMS Root Mean Square
• RR Ramp Rate
• RRFM Reference Receiver Fault Monitor
• RWE Lateral landing criteria
• SAprvert.i Projection of the vertical component and translation of the alongtrack components into the vertical for ith ranging source
• Slat Largest lateral coefficient magnitude for any single satellite
• Slat2 Largest sum of lateral coefficient magnitudes for any two satellites
• Svert Largest vertical coefficient magnitude for any single satellite
• Svert_max Maximum vertical projection for any satellite allowed by geometry screening
• Svert2 Largest sum of vertical coefficient magnitudes for any two satellites
• TBAC Maximum threshold for the RRFM monitor
• TTD Time To Detect
• VAL Vertical Alert Limit
• VPL Vertical Protection Level
• ω n Natural frequency in radians/second C-24
AC 20-191 Appendix D APPENDIX D. AFM PROVISIONS AND EXAMPLE AFM WORDING D.1 Example Provision: AFM "Certificate Limitation" Section.
(With "Type Specific" Example Information and Notes) (List Aircraft Type)
AIRPLANE FLIGHT MANUAL Section 1 - CERTIFICATE LIMITATIONS
ELECTRONIC SYSTEMS
AUTOPILOT/FLIGHT DIRECTOR SYSTEM Automatic Landing Maximum wind component speeds when landing weather minima are predicated on autoland operations:
Headwind: 25 knots Tailwind: 15 knots Crosswind: 5 knots The maximum and minimum glideslope angles are 3.25 degrees and 2.5 degrees respectively.
The autoland capability may be used with flaps 20 or 30, with both engines operative or with one engine inoperative. The Autopilot Flight Director System (AFDS) status annunciation must have LAND 2 or LAND 3 displayed and the SLATS DRIVE message must not be present.
Automatic Approach with Flaps 25 Autoland is not approved with flaps 25.
FAA APPROVED (Date) Section 3 Page D-1
AC 20-191 Appendix D D.2 Example Provision - AFM “Normal Procedures” or “Normal Operation” Section.
[Typical Aircraft Type with Fail Operational and Fail Passive FGS Capability] (List Aircraft Type)
AIRPLANE FLIGHT MANUAL Section 3 - NORMAL PROCEDURES AUTOPILOT - FLIGHT DIRECTOR SYSTEM (AFDS)
LOW WEATHER MINIMA - AUTOMATIC LANDING - FAIL-OPERATIONAL The autopilot system has been shown to meet the applicable airworthiness, performance, and integrity criteria applicable to Category III as specified in FAA Advisory Circular AC 20-191 for a fail- operational automatic landing system, with the following functions operative and LAND 3 annunciated:
Autoland status annunciation on both PFD’s Autothrottle/autothrust Independent ILS and radio altitude sources on the PFD for each pilot, i.e., the following alerting messages are not displayed:
SGL SOURCE DISPLAYS
SGL SOURCE RAD ALT
SINGLE SOURCE ILS
LOW WEATHER MINIMA - AUTOMATIC LANDING - FAIL-PASSIVE The autopilot system has been shown to meet the applicable airworthiness, performance, and integrity criteria applicable to Category III as specified in FAA AC 20-191 for a fail-passive automatic landing system, with the following functions operative and LAND 2 annunciated:
Autoland status annunciation on both PFD’s Independent ILS and radio altitude sources on the PFD for each pilot, i.e., the following alerting messages are not displayed:
SGL SOURCE DISPLAYS
SGL SOURCE RAD ALT
SINGLE SOURCE ILS The demonstration for fail-passive autoland operations with LAND 2 annunciated included a provision for a go-around if a subsequent autopilot system failure were to be detected on approach, if operational credit for use of autoland is required.
CAUTION: If the autopilot disconnects during an engine-out go-around, loss of autopilot rudder control can result in large yaw and roll excursions.
FAA APPROVED (Date) Section 3 Page D-2
AC 20-191 Appen dix D Page 2 of Example Provision - AFM “Normal Procedures” or “Normal Operation” Section[Typical Aircraft Type with Fail Operational and Fail Passive FGS Capability]
Section 3 - NORMAL PROCEDURES AUTOPILOT - F LIGHT DIRECTOR SYSTEM (AFDS) (Continued)
LOW WEATHER MINIMA - AUTOPILOT APPROACH The autopilot system has been shown to meet the applicable airworthiness, performance, and integrity criteria applicable to Category II as specified in FAA AC 20-191 Chapter 4 for automatic approach with the following functions operative and LAND 3 or LAND 2 annunciated: Independent ILS and radio altitude sources on the PFD for each pilot, i.e., the following alerting messages are not displayed:
SGL SOURCE DISPLAYS
SGL SOURCE RAD ALT
SINGLE SOURCE ILS
LOW WEATHER MINIMA - FLIGHT DIRECTOR The flight director system has been shown to meet the applicable airworthiness, performance, and integrity criteria applicable to Category II as specified in FAA AC 20-191 for manual approach with the following functions operative:
Normal flight controls Air Data Inertial Reference Unit Independent ILS and radio altitude sources on the PFD for each pilot, i.e., the following alerting messages are not displayed:
SGL SOURCE DISPLAYS
SGL SOURCE RAD ALT
SINGLE SOURCE ILS
SINGLE SOURCE F/D FAA APPROVED (Date) Section 3 Page
D-3
AC 20-191 Appendix D D.3 Example Provision - AFM “Normal Procedures” or “Normal Operation” Section.
[Typical Aircraft Type with Fail Passive FGS Capability] (List Aircraft Type)
AIRPLANE FLIGHT MANUAL Section 3 - NORMAL OPERATIONS
AUTOPILOT - FLIGHT DIRECTOR SYSTEM (AFDS) The Autopilot-Flight Director System is used as either a single channel autopilot or flight director for en route and single channel approaches. Dual autopilot channels provide fail-passive operation for automatic landing and go-around. Dual flight directors provide for takeoff, approach, and go-around guidance.
The following flight path control functions for automatic (autopilot) and/or manual (flight director) control of the airplane are provided:
• Lateral navigation (LNAV)
• Vertical navigation (VNAV)
• VOR
• LOC (Front course only) Approach
• Autoland (Dual autopilot only)
• Go-around (Dual autopilot and/or flight director only) The following pilot assist functions for automatic (autopilot) and/or manual (flight director) control of the airplane are provided:
• Control Wheel Steering (Autopilot only)
• Heading select and hold
• Vertical speed select and hold
• IAS/Mach select and hold (Elevator control of speed in level change)
• Altitude Select/Acquire or Capture and Hold
• Takeoff (Dual Flight director only)
• Go-around, one engine inoperative (Dual Flight director only) The Captain’s and First Officer’s instruments (Display Source, VHF NAV and IRS) must not be on the same source when credit for use of the AFDS is necessary to make lower weather minima approaches.
An interlock is provided with the electrical transfer bus sensing circuit to preclude dual-channel autopilot operation on a single source of power. However, the Auxiliary Power Unit generator may be used as an independent power source.
FAA APPROVED (Date) Section 3 Page ___ D-4
AC 20-191 Appen dix D Page 2 of Example Provision - AFM “Normal Procedures” or “Normal Operation” Section [Typical Aircraft Type with Fail Passive FGS Capability]
Section 3 - NORMAL OPERATIONS AUTOPILOT - FLIGHT DIRECTOR SYSTEM (AFDS) (Continued)
DEMONSTRATED CONDITIONS The system has been demonstrated both with and without yaw damper and autothrottle/autothrust and with normal landing flaps 30 and 40.
The approach speed selected for automatic approaches using autothrottles/autothrust was VREF + 5 knots (no wind correction).
The approach speed selected for autothrottle/autothrust inoperative was VREF for calm air conditions and VREF + 1/2 (Headwind) + Full Gust for wind conditions.
The automatic landing system has been demonstrated in VMC conditions with the following wind conditions:
Headwind - 25 knots Tailwind - 30 knots Crosswind - 24 knots Satisfactory Automatic Landing System performance has been demonstrated on U.S. Type II and Type III ILS ground facilities.
An autopilot minimum engage height of 400 feet after takeoff has been demonstrated to provide satisfactory performance.
Single Engine Approach: The AFDS has demonstrated adequate performance for low visibility approach using a single engine, with flaps 15.
MINIMUM MULTICHANNEL ENGAGE ALTITUDE FOR AUTOLAND On approach for autoland, dual channel operation should be engaged prior to 800 feet AGL. Check FLARE arm annunciation at approximately 500 feet AGL.
FAA APPROVED (Date) Section 3 Page
D-5
AC 20-191 Appendix D Page 3 of Example Provision - AFM “Normal Procedures” or “Normal Operation” Section [Typical Aircraft Type with Fail Passive FGS Capability] Section 3 - NORMAL OPERATIONS AUTOPILOT - FLIGHT DIRECTOR SYSTEM (AFDS) (Continued)
AFDS SYSTEM CONFIGURATION The AFDS equipment listings in this section do not necessarily denote all of the systems and equipment required for the types of operation specified. Applicable FAR's and AC’s may prescribe performance provisions for such additional systems such as autothrottle/autothrust, or autobrakes. Operators should determine the total systems requirements for each type of operation prior to requesting OpSpecs authorization.
Demonstrated compliance with the airworthiness performance standards does not constitute approval to conduct operations in lower weather minimums.
DEMONSTRATED ALTITUDE LOSS The demonstrated altitude loss due to a simulated hard-over autopilot malfunction is: Level Flight:
Flaps up - 370 feet when recovery was initiated 3 seconds after the recognition point.
Approach:
(a) 23 feet with a 1 second time delay between recognition point and initiation of recovery.
(b) Negligible when recovery was initiated without delay after pilot recognition.
Go-Around:
The demonstrated altitude loss during an automatic go-around initiated below 100 feet AGL is listed below:
GA Altitude (ft AGL) Altitude Loss (ft) 70 to 100 26 60 21 50 20 40 18 30 11 20 3 10 2.5 FAA APPROVED (Date) Section 3 Page D-6
AC 20-191 Appendix D Page 4 of Example Provision - AFM “Normal Procedures” or “Normal Operation” Section [Typical Aircraft Type with Fail Passive FGS Capability] Section 3 - NORMAL OPERATIONS AUTOPILOT - FLIGHT DIRECTOR SYSTEM (AFDS) (Continued) AUTOPILOT APPROACH/AUTOLAND (FAIL PASSIVE) (Applicable to Category III) The Autopilot System has been shown to meet the applicable airworthiness and performance and reliability criteria of FAA AC 20-191 for automatic approach and landing of the aircraft to touchdown with the following additional equipment operative and FLARE arm annunciated.
• Dual Channel Autopilot engaged
• Low Range Radio Altimeter and display for each Pilot
• DH Display for each Pilot
• Two Digital Air Data Computer Systems
• Windshield Wipers for each Pilot
• ILS Receiver and display for each Pilot
• Flight Mode Annunciator for each Pilot
• Two ADIRU's (associated with the engaged autopilots) in NAV mode
• Dual Hydraulic Systems
• Two sources of electrical power (The APU generator may be used as an independent power source)
• Both Engines Operating AUTOPILOT APPROACH (Applicable to Category II) The Autopilot System has been shown to meet the airworthiness, performance, and reliability criteria of FAA AC 20-191, Chapter 4 for Category II, for automatic approach with the following additional listed equipment operative:
• Single or Dual channel Autopilot engaged
• Low Range Radio Altimeter and display for each Pilot
• DH Display for each Pilot
• Two Digital Air Data Computer Systems
• Windshield Wipers for each Pilot
• ILS Receiver and display for each Pilot
• Flight Mode Annunciator for each Pilot
• Two ADIRU's (associated with the engaged autopilot) in NAV mode
• Two sources of electrical power (The APU generator may be used as an independent power source.)
• Both Engines Operating FAA APPROVED (Date) Section 3 Page D-7
AC 20-191 Appendix D Page 5 of Example Provision - AFM “Normal Procedures” or “Normal Operation” Section [Typical Aircraft Type with Fail Passive FGS Capability] Section 3 - NORMAL OPERATIONS AUTOPILOT - FLIGHT DIRECTOR SYSTEM (AFDS) (Continued)
FLIGHT DIRECTOR (F/D) The flight director command may be used as supplemental guidance to the primary speed and attitude indications for takeoff, climb, and descent to acquire and maintain desired altitudes.
All of the autopilot command modes, except "CWS," are also available on the flight directors. An additional takeoff mode exists for the F/D only. One or both F/Ds may be on for all modes, except during T/O or GA that requires dual F/D ON.
FLIGHT DIRECTOR APPROACH (Applicable to Category II) The flight director system has been shown to meet the applicable airworthiness, performance, and reliability criteria of FAA AC 20-191 for manual approach with the following equipment operative:
• Both flight directors must be selected
• Low Range Radio Altimeter and display for each Pilot
• DH Display for each Pilot
• Two Digital Air Data Computer Systems
• Windshield Wipers for each Pilot
• ILS Receiver and display for each Pilot
• Flight Mode Annunciator for each Pilot
• Two ADIRUs in NAV mode.
• Two sources of electrical power. (The APU generator may be used as an independent power source.)
• Both Engines Operating
GO - AROUND When go-around is initiated, the autothrottle/autothrust system (if engaged) advances the thrust levers automatically. Flaps and landing gear must be controlled manually.
An Autothrottle/autothrust, Flight Director and/or Dual Autopilot go-around may be initiated below a radio altitude of 2000 feet by pressing the go-around switches.
When a decision is made to abort an approach, actuate the go-around switches and assure rotation to go-around attitude. Verify thrust lever movement to achieve a nominal rate of climb and retract flaps to flaps 15.
After a positive rate of climb has been established, retract landing gear. Climb to a safe altitude, accelerate and retract remaining flaps according to takeoff flap retraction speed schedule. Monitor rate of climb, attitude, and airspeed.
Full go-around thrust may be obtained, after engine spool up, by reactivating the go-around switch(es). In windshear, the recommended procedure is to delay flap and gear retraction until windshear is no longer a factor.
FAA APPROVED (Date) Section 3 Page D-8
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