Appendix E E-2 Intruder. - Aircraft satisfying the TCAS II traffic advisory detection criteria.
Missing resolution advisory. - An RA that does not occur, or that occurs later than the CAS logic indicates is necessary, when a threat is present.
Mode A. - Type of secondary surveillance radar (SSR) equipment or mode of operation that replies by selected 4096 code (nonaltitude) when interrogated.
Mode C. - Type of secondary surveillance radar (SSR) equipment or mode of operation that replies with aircraft altitude information when interrogated.
Mode S. - Type of secondary surveillance radar (SSR) equipment that replies to Mode A and Mode C ground interrogations, a discrete address, and other aircraft information in response to interrogations from the ground or air.
Other traffic. - Aircraft more than ±1200 feet vertical or 6 nautical miles (NM) from own aircraft that are neither RA nor TA.
Passive surveillance. - The use of airborne position messages to update a TCAS track.
Preventive resolution advisory. - Requires a pilot to avoid certain deviations from current vertical rate (for example, a Do Not Climb RA when the aircraft is level).
Proximate traffic. - Aircraft within 6 NM in range and within ±1,200 feet vertically from own aircraft, but does not meet the TCAS II thresholds of a TA or RA.
Resolution advisory. - Aural voice and display information provided by TCAS II to a flight crew, advising that a particular maneuver should, or should not, be performed to attain or maintain minimum safe vertical separation from an intruder.
Resolution display. - Shows vertical guidance depicting areas to “fly to” and/or avoid above or below the TCAS II equipped aircraft.
Sense. - A direction that an RA may take (either Climb or Descend) relative to the existing flight path of own aircraft.
Threat. - An intruder that satisfies the threat detection logic and thus requires an RA.
Track. - Estimated position and velocity of a single aircraft based on correlated surveillance data reports.
Traffic. - Aircraft with an operating transponder capable of being tracked and displayed by a TCAS-equipped aircraft.
Traffic advisory (TA). - Aural voice and display information from TCAS II to a flight crew, identifying the location of nearby traffic meeting certain minimum separation criteria.
Traffic display. - Horizontal position of transponder-equipped aircraft relative to the TCAS II equipped aircraft.
Transponder register. - Transponder register means a transponder data buffer containing different pieces of information. It has 56 bits which are divided into different fields. The definition of the transponder registers can be found in ICAO Doc 9871 edition 2 and in RTCA/DO-181E, Minimum Operational Performance Standards for Air Traffic Control Radar Beacon System/Mode Select (ATCRBS/Mode S) Airborne
Appendix E E-3 Equipment. Transponder registers are numbered in hexadecimal (00 hex to FF hex).
The register number is also known as the BDS code (Comm-B data selector). In this documentation a register is named: register XY16 or register addressed by BDS code X,Y. Outside this document, it is also often referenced as just BDS X,Y.
E.2 Acronyms.
14 CFR Title 14 of the Code of Federal Regulations ACARS Aircraft communications addressing and reporting system ADS-B Automatic dependent surveillance - broadcast AFM Airplane flight manual AFMS Airplane flight manual supplement AGL Above ground level ASR Airport surveillance radar AMC Acceptable Means of Compliance ATA Air Transport Association ATC Air traffic control ATCRBS Air traffic control radar beacon system CAS Collision avoidance algorithm, or CAS logic CMC Central Maintenance Computer CRS CAS requirements specification dB Decibel EADI Electronic attitude display indicator EFIS Electronic flight instrument system EHS Enhanced Surveillance EHSI Electronic horizontal situation indicators ELS Elementary Surveillance EMC Electromagnetic compatibility FAA Federal Aviation Administration FD Flight director FHA Functional hazard assessment FL Flight level FMEA Failure modes and effects analysis FPM Feet Per Minute
Appendix E E-4 GPS Global positioning system GPWS/TAWS Ground proximity warning system/terrain awareness warning system HUD Heads-up device ICA Instructions for Continued Airworthiness ICAO International Civil Aviation Organization IVSI Instantaneous vertical speed indicator JAA Joint Aviation Authorities MHz Megahertz NAS National Airspace System ND Navigation display NM Nautical mile PFD Primary flight display RVSM Reduced Vertical Separation Minimum RA Resolution advisory SARP Standards and Recommended Practices STC Supplemental type certificate TA Traffic advisory TC Type certificate TCAS II Traffic alert and collision avoidance system TSO Technical standard order TTP TCAS transition program Vmo Maximum operating limit speed
Appendix F F-1 APPENDIX F. INTERFACING THE TRANSPONDER TO AIRCRAFT SYSTEMS TO
SUPPORT TRANSMISSION OF SHORT-TERM INTENT F.1 General.
F.1.1 Selected altitude information is intended for use by ATC to improve the controller tactical view by providing them with a digital indication of altitude clearance intent and for improving performance of conflict probe automation.
F.1.2 With respect to implementing short-term intent, the term “target altitude” is the next altitude at which the aircraft will level-off if in a climb or descent, or the aircraft current intended altitude if it is intending to hold its altitude.
F.1.3 A pilot may operate the aircraft in a manual mode or Flight Director/Autopilot mode where the level off altitude is not known by any aircraft system. Even when operating the aircraft in Flight Director/Autopilot mode, some legacy flight automation may have knowledge of the level off altitude, but not provide this information via an external interface. In either of these conditions, the BDS 4016 and BDS 6216 implementation must indicate that the target altitude is unknown.
F.1.4 Some legacy aircraft do not have selected altitude functionality, but do have a function that alerts the flight crew when a desired altitude is reached, commonly called an altitude alerter. In installations where an altitude alerter is present and the operator of the aircraft has operating guidance to require its use, the altitude alerter setting may be used to encode MCP/FCU selected altitude.
F.1.5 Note: If the flight crew does not use the altitude alerter, encoding this information will be misleading and the equipment should not be interfaced to the transponder.
F.1.6 In existing aircraft with federated avionics suites, it is typical to have a pilot interface to the autopilot implemented as separate self-contained unit which is wired to the rest of the systems in the aircraft as needed. This is commonly referred to as a Mode Control Panel (MCP) or Flight Control Unit (FCU). Historically, there was no connection between these control units and the transponder. In the following paragraphs, the guidance is written from the perspective of this type of federated architecture. In aircraft with more integrated avionics suites, the display and control of autopilot functions may be integrated with the display and control of several other aircraft functions. In this type of integrated architecture there is not a literal MCP or FCU. In these cases, the guidance still applies to the autopilot control function regardless of what hardware it is integrated into.
F.1.7 A similar case exists for the Flight Management System (FMS) function. Historically, the FMS was a self-contained unit wired to other aircraft systems as needed. In modern flight decks, the FMS function can be integrated in hardware with other aircraft systems. The following guidance is written as if the FMS is a federated unit.
The guidance still applies to the case where FMS functionality is integrated with other aircraft systems.
Appendix F F-2 F.2 F.2.1 F.2.2 F.2.3 F.2.4 F.2.5 F.2.5.1 F.2.5.2 F.2.5.3 F.2.5.4 Populating Selected Vertical Intention Register BDS 4016.
This section provides guidance for interfacing the transponder to aircraft systems for complying with the EU Enhanced Surveillance requirement for Selected Vertical Intent Register BDS 4016.
I f available on the aircraft, interface the MCP/FCU to the transponder and verify that the selected altitude information is reported correctly and marked as valid. If the data is either not available or invalid, verify that it is reported as invalid.
For installations with an FMS system, the installer should ensure the transponder is receiving valid selected altitude information. If the data is either not available or invalid, verify that it is reported as invalid.
The installer should ensure that the transponder receives the barometric pressure setting in use. In some installations, it is possible to override the barometric pressure setting and fly the aircraft to the uncorrected pressure altitude. In this case the reported correction should be zero. If the data is either not available or invalid, verify that it is reported as invalid.
The installer should verify all reserved fields are unused and set to zero.
For installations that do not have VNAV, LNAV, Autopilot Engaged, Altitude Hold, or Approach Mode information available, the installer should ensure the MCP/FCU Mode bits are marked invalid. If the transponder receives one or more of the mode parameters, the installer should verify the MCP/FCU Mode bits are set in accordance with the horizontal/vertical mode controlling the aircraft. The extent of these modes can vary significantly across different aircraft platforms. A description of each field follows, to clarify the intended use of these parameters by ATC. Refer to the example scenarios for a detailed description on setting the mode field.
Note: Altitude Hold Mode may be inhibited when the aircraft has c aptured the approach (e.g. capturing the glideslope).
F.2.5.5 Approach Mode indicates the pilot has armed the desired approach source (e.g.
VOR/LOC and G/S or LNAV and VNAV).
VNAV indicates when an aircraft is following vertical path guidance using information from the FMS. The pilot may arm this mode manually.
LNAV indicates when the aircraft is following lateral path guidance using information from the FMS. The pilot may arm this mode manually.
Autopilot Engaged indicates when the pilot has engaged the Autopilot system.
Altitude Hold Mode indicates that the aircraft will remain at its current altitude regardless of the current setting or a change to the MCP/FCU selected altitude or FMS selected altitude data.
Appendix F F-3 F.3 Populating Target State and Status Information Register BDS 6216.
This section provides guidance for interfacing the ADS-B system to aircraft systems for complying with the EU ADS-B requirement for Target State and Status BDS 6216.
F.3.1 SILSUPP is based on whether the position source probability of exceeding the reported integrity value is calculated on a per-hour or per-sample basis and should be set based on design data from the position source equipment manufacturer. ADS-B systems interfaced with a GNSS position source compliant with any revision of TSO-C129, TSO-C145, TSO-C146, or TSO-C196 may preset SILSUPP to ZERO, as GNSS position sources use a per hour basis for integrity.
F.3.2 For installations with both an MCP/FCU and an FMS system, the installer should ensure the selected altitude information transmitted is the MCP/FCU selected altitude.
This should be verified in transponder register BDS 4016 and the Target State and Status ADS-B message. If neither the MCP/FCU nor the FMS is providing selected altitude information or the information is invalid, then the installer should ensure the data status is set to all ZEROs. In some legacy aircraft, the selected altitude information may be available but the system does not indicate which source, MCP/FCU or FMS, is in control of the aircraft vertical profile. In this case, the MCP/FCU selected altitude should be encoded when it is valid. If MCP/FCU selected altitude is not valid, and the FMS selected altitude is valid, then the FMS selected altitude should be encoded.
F.3.3 The installer should ensure that when the aircraft vertical intent is to fly the current altitude (e.g., altitude hold) or the pilot is manually flying the aircraft, the MCP/FCU selected altitude is encoded in the Target State and Status ADS-B message.
F.3.4 The installer should ensure that the transponder receives the barometric pressure setting in use. In some installations, it is possible to override the barometric pressure setting and fly the aircraft to the uncorrected pressure altitude. In this case the reported correction should be zero. If the barometric pressure setting is not available or invalid, the installer should verify that the data status is marked invalid.
F.3.5 For installations with both an MCP/FCU and an FMS system, the installer should ensure the selected heading information transmitted by the transponder corresponds to the system in control of the aircraft horizontal profile. If the data is either not available or invalid, verify that it is reported as invalid. In some legacy aircraft, the selected heading information may be available but the system does not indicate which source, MCP/FCU or FMS, is in control of the aircraft horizontal profile. In this case, the MCP/FCU selected heading should be encoded when it is valid. If MCP/FCU selected heading is not valid, and the FMS selected heading is valid, then the FMS selected heading should be encoded.
F.3.6 The accuracy limits for the Navigation Accuracy Category for Position (NACP) allow the surveillance applications to determine whether the reported geometric position has an acceptable level of accuracy for its intended use. The ADS-B equipment must set the NACP based on the real time 95% accuracy metric provided by the position source.
Appendix F F-4 When interfacing GNSS sources, the NACP should be based on a qualified Horizontal Figure of Merit (HFOM).
F.3.7 You should verify the type of altitude source installed in the aircraft and interface the altitude system per the ADS-B equipment manufacturer’s instructions. For aircraft with an approved, non-Gillham altitude source, NICBARO should be preset at installation to ONE. For aircraft with a Gillham altitude source without an automatic cross-check, NICBARO must be preset at installation to ZERO. For aircraft which dynamically cross-check a Gillham altitude source with a second altitude source the NICBARO must be set based on the result of this cross-check. We recommend that ADS-B installations use non-Gillham altitude encoders to reduce the potential for altitude errors.
F.3.8 SIL is typically a static (unchanging) value and may be set at the time of installation if a single type of position source is integrated with the ADS-B system. SIL is based solely on the position source’s probability of exceeding the reported integrity value and should be set based on design data from the position source equipment manufacturer. Installations which derive SIL from GNSS position sources compliant with any revision of TSO-C129, TSO-C145, TSO-C146, or TSO-C196 which output Horizontal Protection Level (HPL) or Horizontal Integrity Level (HIL) should set the SIL = 3 because HPL and HIL are based on a probability of 1x10-7 per hour. Do not base NIC or SIL on Horizontal Uncertainty Level (HUL) information. If integrating with a non-compliant GPS, SIL must be set to 0.
F.3.9 For installations that do not have VNAV, LNAV, Autopilot Engaged, Altitude Hold, or Approach Mode information available, the installer should ensure the MCP/FCU Mode bits are reported as invalid. If one or more of the mode parameters are provided to the transponder, the installer should verify the MCP/FCU Mode bits are set in accordance with the horizontal/vertical mode controlling the aircraft. The extent of these modes can vary significantly across different aircraft platforms. A description of each field follows, to clarify the intended use of these parameters by ATC. Refer to the example scenarios for a detailed description on setting the mode field.
F.3.9.1 VNAV indicates when an aircraft is following vertical path guidance using information from the FMS. The pilot may arm this mode manually.
F.3.9.2 LNAV indicates when the aircraft is following lateral path guidance using information from the FMS. The pilot may arm this mode manually.
F.3.9.3 Autopilot Engaged indicates when the pilot has engaged the Autopilot system.
F.3.9.4 Altitude Hold Mode indicates that the aircraft will remain at its current altitude regardless of the current setting or a change to the MCP/FCU selected altitude or FMS selected altitude data.
Note: Altitude Hold Mode may be inhibited when the aircraft has captured the approach (e.g. capturing the glideslope).
Appendix F F-5 F.3.9.5 Approach Mode indicates the pilot has armed the desired approach source (e.g.
VOR/LOC and G/S or LNAV and VNAV).
F.3.10 The installer should verify all reserved fields are unused and set to zero.
F.3.11 The TCAS Installed and Operational field must interface with the TCAS II system if your aircraft has a TCAS II system. This parameter should be preset to ZERO if your aircraft does not have a TCAS II or if your aircraft has a TCAS I. Typically, this parameter will already be provided to the Mode S transponder from the TCAS II.
TCAS II systems compliant with TSO-C119( ) indicate they are operational and able to issue an RA when they transmit Reply Information (RI) = 3 or 4 to the transponder.
F.3.12 MCP/FCU Mode Examples To further clarify how the vertical mode bits should operate, this section presents a set of scenarios below. Figure 3 depicts a series of vertical maneuvers. Table 1 illustrates how the equipment would set the parameters for BDS 4016 during each maneuver.
Similarly, Table 2 illustrates how the equipment would set the parameters for BDS 6216 during each maneuver. The parameters encoded in BDS 4016 and BDS 6216 by the transponder are based on information received from other aircraft equipment or via aircraft configuration strapping. Below the table there is a description of each step along with any assumptions made for the given maneuver. For the purposes of these examples, we assume that the pilot has the ability to manually select the use of MCP/FCU or FMS as the source providing the flight path information to the aircraft’s autoflight guidance system. We also assume that a change by the pilot on the MCP/FCU will override the information provided by the FMS.
Figure F- 1: Aircraft Flight Path Step 1 Step 2 Step 3 Step 4 Step 6 Step 0 Waypoint 1 Waypoint 2 Waypoint 3 Waypoint 4 Waypoint 5 Waypoint 6 Waypoint 7 HDG: 293o Alt: FL250 HDG: 280o Alt: FL220 HDG: 275o Alt: FL220 HDG: 301o Alt: FL210 Step 5 HDG: 275o Alt: FL240 Waypoint 8 HDG: 301o Alt: FL170 Step 7 HDG: 301o Alt: FL200 HDG: 301o Alt: FL190
Appendix F F-6 Table F- 1. BDS 4016 Parameters Step 0 Step 1 Step 2 Step 3 Step 4 Step 5 Step 6 Step 7 VNAV 1 1 0 0 0 0 1 1 Alt Hold 0 0 1 1 0 0 0 0 Approach 0 0 0 0 0 0 1 1 Target Altitude Source1 11 11 01 01 10 00 11 11 Table F- 2: BDS 6216 Parameters Step 0 Step 1 Step 2 Step 3 Step 4 Step 5 Step 6 Step 7 Autopilot Engage 1 1 1 1 1 0 1 1 VNAV 1 1 0 0 0 0 1 1 LNAV 1 1 1 0 1 0 1 1 Alt Hold 0 0 1 1 0 0 0 0 Approach 0 0 0 0 0 0 1 1 Selected Altitude MCP MCP MCP MCP MCP MCP MCP MCP
Appendix F F-7 F.3.12.1 Step 0 F.3.12.1.1 Assumptions:
F.3.12.1.1.1 Aircraft is flying an en-route segment; the pilot engages the use of the FMS.
F.3.12.1.1.2 The pilot has engaged the Autopilot System F.3.12.1.2 Maneuver: Level Flight to Waypoint 1 F.3.12.1.3 The aircraft autopilot levels off the aircraft at the specified heading and altitude based on the waypoint information provided by the FMS system
(i.e., HDG: 293o, ALT: FL250). The transponder sets the parameters as follows:
F.3.12.1.3.1 BDS 4016 and BDS 6216 Parameters:
F.3.12.1.3.1.1 When the pilot engages the FMS system as the vertical driving source for the aircraft, VNAV is set to “ONE”.
F.3.12.1.3.1.2 Altitude hold is set to “ZERO”.
F.3.12.1.3.1.3 The pilot has not armed the approach. Therefore, approach mode is set to “ZERO”.
F.3.12.1.3.2 BDS 4016 Specific Parameters:
F.3.12.1.3.2.1 Target Altitude Source represents the use of FMS (i.e., “11”) as the source being used for selected altitude information.
F.3.12.1.3.2.2 Reserved F.3.12.1.3.3 BDS 6216 Specific Parameters:
F.3.12.1.3.3.1 Once engaged by the pilot, the Autopilot system sets Autopilot Engage to “ONE”.
F.3.12.1.3.3.2 When the pilot engages the FMS system as the lateral driving source for the aircraft, LNAV is set to “ONE”.
F.3.12.1.3.3.3 Selected Altitude field is populated with MCP/FCU selected altitude and the selected altitude type is set to MCP/FCU.
F.3.12.2 Step 1 F.3.12.2.1 Assumptions:
F.3.12.2.1.1 The pilot has made no changes on the MCP/FCU system.
Appendix F F-8 Note: The altitude in the MCP/FCU must be higher or lower than the achieve altitude desired by the FMS. If not, the MCP/FCU will act as an upper or lower altitude restriction.
F.3.12.2.1.2 Reserved F.3.12.2.2 Maneuver: Descent from Waypoint 1 to Waypoint 2 F.3.12.2.2.1 The FMS determines a descent and heading change as required and transmits the appropriate information to the autopilot system (i.e., HDG:
280o, ALT: FL220). The transponder sets the parameters as follows:
F.3.12.2.2.2 BDS 4016 and BDS 6216 Parameters:
F.3.12.2.2.2.1 VNAV remains set to “ONE” as FMS system is still providing guidance to the aircraft.
F.3.12.2.2.2.2. The pilot has not engaged altitude hold and altitude hold remains set to “ZERO”.
F.3.12.2.2.2.3 The pilot has not armed a method of approach.
Therefore, approach mode remains set to “ZERO”.
F.3.12.2.2.3 BDS 4016 Specific Parameters:
F.3.12.2.2.3.1 Target Altitude Source represents the use of FMS (i.e., “11”) as the source for selected altitude information.
F.3.12.2.2.3.2 Reserved F.3.12.2.2.4 BDS 6216 Specific Parameters:
F.3.12.2.2.4.1 Autopilot Engage remains set to “ONE”.
F.3.12.2.2.4.2 LNAV remains set to “ONE” as the FMS is still providing guidance to the aircraft.
F.3.12.2.2.4.3 Selected Altitude field is populated with MCP/FCU selected altitude and the selected altitude type is set to MCP/FCU.
F.3.12.3 Step 2 F.3.12.3.1 Assumptions:
F.3.12.3.1.1 The pilot has made no heading or altitude changes on the MCP/FCU system.
F.3.12.3.1.2 Upon leveling off, the pilot engages Altitude Hold.
F.3.12.3.2 Maneuver: Level Flight from Waypoint 2 with Altitude Hold engaged
Appendix F F-9 F.3.12.3.2.1 The aircraft achieves the desired heading and altitude provided by the FMS system, and levels off at waypoint 2. The transponder sets the parameters as follows:
F.3.12.3.2.2 BDS 4016 and BDS 6216 Parameters:
F.3.12.3.2.2.1 VNAV is set to “ZERO.”
F.3.12.3.2.2.2 Altitude Hold is set it to “ONE.”
F.3.12.3.2.2.3 The pilot has not armed a method of approach.
Therefore, approach mode remains set to “ZERO.”
F.3.12.3.2.3 BDS 4016 Specific Parameters:
F.3.12.3.2.3.1 Target Altitude Source represents the use of Aircraft Altitude (i.e., “01”) as the source being used for selected altitude information.
F.3.12.3.2.3.2 Reserved F.3.12.3.2.4 BDS 6216 Specific Parameters:
F.3.12.3.2.4.1 Autopilot Engage remains set to “ONE.”
F.3.12.3.2.4.2 LNAV remains set to “ONE” as the FMS is still providing guidance to the aircraft.
F.3.12.3.2.4.3 Selected Altitude field is populated with MCP/FCU selected altitude and the selected altitude type is set to MCP/FCU.
F.3.12.4 Step 3 F.3.12.4.1 Assumptions:
F.3.12.4.1.1 The pilot has input a cleared heading assigned by ATC into the MCP/FCU.
F.3.12.4.1.2 Reserved F.3.12.4.2 Maneuver: Altitude Hold with Heading change from Waypoint 3 to Waypoint 4 F.3.12.4.2.1 As the aircraft approaches waypoint 3, the pilot received a new heading from ATC deviating from the heading information being provided by the FMS system (i.e., HDG: 275o). The pilot enters the cleared heading into the MCP/FCU, and disengages the use of the FMS system as the lateral guidance source. The autopilot remains engaged, and begins the maneuver to achieve the selected heading received from the MCP/FCU for waypoint 4. The transponder will set the parameters as follows:
F.3.12.4.2.2 BDS 4016 and BDS 6216 Parameters: