2-15 Table 1. Maneuvers
CONDITION FLIGHT REGIME WEIGHT
ALTITUDE,
TEMPERATUR E1 THRUST FLAPS GEAR INITIAL AIRSPEED2 MINIMUM AIRSPEED2 MANEUVER3 1 Takeoff Part 25 climb limit Maximum rated takeoff All takeoff Up V2+204 1.2VS15 thru RA A 2 Takeoff Part 25 climb limit Maximum rated takeoff All takeoff Up V2+204 1.2VS15 thru RA B 3 Takeoff Part 25 Climb limit Maximum rated takeoff All takeoff Up AFM allengine takeoff speed6 15° bank to stall warning7 thru recovery C 4 Approach Part 25 Climb limit Spin up to max go-around thrust during maneuver from thrust for level flight Less than landing Up 1.6VS1 1.2VS15 thru RA A 5 Approach Part 25 Climb limit Spin up to max go-around thrust during maneuver from thrust for level flight Less than landing Up 1.6VS1 1.2VS15 thru RA B 6 Approach Part 25 Climb limit Spin up to max go-around thrust during maneuver from thrust for level flight Less than landing Up, or down to up Min.
maneuver speed from training procedures 15° bank to stall warning7 thru recovery C
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CONDITION FLIGHT REGIME WEIGHT
ALTITUDE,
TEMPERATUR E1 THRUST FLAPS GEAR INITIAL AIRSPEED2 MINIMUM AIRSPEED2 MANEUVER3 7 Landing, Transition to Go-Around at RA Part 25 Climb limit Spin up to max go-around thrust during maneuver from thrust required for 3° glideslope Transition from landing flap to goaround flap Down to up VREF + 10 1.2VS15 thru RA A 8 Landing, Transition to Go-Around at RA Part 25 Climb limit Spin up to max go-around thrust during maneuver from thrust required for 3° glideslope Transition from landing flap to goaround flap Down to up VREF + 10 1.2VS15 thru RA B 9 Landing, Transition to Go-Around at RA Part 25 climb limit Spin up to max go-around thrust during maneuver from thrust required for 3° glideslope Transition from landing flap to goaround flap Down to up VREF + airspeed addition from training procedures 15° bank to stall warning7 thru recovery C 10 En Route Critical Wt/Alt giving 0.3g to buffet onset Thrust for level flight increased to max continuous, if required Up Up Long-range cruise Higher of
1.2VS5 if defined or buffet onset A 11 En Route Critical Wt/Alt giving 0.3g to buffet onset Thrust for level flight increased to max continuous, if required Up Up Long-range cruise Higher of
1.2VS5 if defined or buffet onset B
2-17 Notes:
1. Weight = Lesser of climb limit or structural; Airport Pressure Altitude = sea level to 5300 ft; Temperature = ISA ± 50 °F; Evaluate conditions 1 through 3 700 ft above airport; evaluate conditions 4 - 9 1700 ft above airport.
2. For those airplanes that use reference stall speed (VSR) in lieu of stalling speed (VS), replace 1.2 VS1 with 1.13 VSR1, 1.2VS with
1.13VSR and 1.6 VS1 with 1.5 VSR1.
3. Maneuvers:
a. Maneuver A evaluates the TCAS II CLIMB RA. From the initial steady-state condition, after a 3-second pilot-reaction time delay, rotate the aircraft at 1.25 g to attain +1500 feet per minute climb. Hold until the total duration of the RA of 25 seconds has elapsed. Recover to attain the initial trim airspeed.
b. Maneuver B evaluates the TCAS II INCREASE CLIMB RA following a CLIMB RA. From the initial steady-state condition, after a 3-second pilot-reaction time delay, rotate the aircraft at 1.25 g to attain +1500 feet per minute climb. Hold until 15 seconds has elapsed from when the CLIMB RA was issued. Then, after a 1-second pilot reaction time-delay to the INCREASE CLIMB RA, rotate the aircraft again at 1.25 g to attain +2500 feet per minute climb and hold until the total duration of the RA of 25 seconds has elapsed. Recover to attain the initial trim airspeed.
c. Maneuver C evaluates a maximum duration TCAS II INCREASE CLIMB RA following a minimum duration CLIMB RA.
From the initial steady-state condition, after a 3-second pilot-reaction time delay, rotate the aircraft at 1.25 g targeting +1500 feet per minute climb until 6 seconds has elapsed from when the the system issued the CLIMB RA. Then, after a 1-second pilot-reaction time delay to the INCREASE CLIMB RA, rotate the aircraft again at 1.25 g to attain +2500 feet per minute climb and hold until the total duration of the RA of 25 seconds has elapsed. Recover to attain the initial trim airspeed.
4. VY + 10 for nontransport category aircraft without a defined V2.
5. For those airplanes where the power-on stalling speed is significantly lower than the power-off stalling speed, use 1.1VS or
1.08VSR for those airplanes that use reference stall speed (VSR) in lieu of stalling speed (VS).
6. VY for nontransport category aircraft without a defined V2
7. For those airplanes where the power-on stalling speed is significantly lower than the power-off stalling speed, use VS1 or 0.94VSR1 for those airplanes that use reference stall speed (VSR) in lieu of stalling speed (VS).
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2.3.5.8 A summary of the system inhibits (limitations) programmed into the TCAS II computer is given in Table 2 below.
Table 2 System Inhibits
INHIBIT PARAMETERS Increase Descent RA Inhibited below 1650 ft AGL while climbing and inhibited below 1450 ft AGL while descending.
Descend RA Inhibited below 1200 ft AGL while climbing and inhibited below 1000 ft AGL while descending.
TA Voice Messages Inhibited below 400 ft AGL while descending and inhibited below 600 ft AGL while climbing.
RAs Inhibited below 1100 ft AGL while climbing, and inhibited below 900 ft AGL while descending. (TCAS automatically reverts to TA only).
Self-Test Can be inhibited when airborne.
Advisory Priority Automatically reverts to TA only when higher priority advisories (such as GPWS/TAWS and windshear) occur.
Climb RA Can be inhibited, based upon aircraft performance capability.
Increase Climb RA Can be inhibited, based upon aircraft performance capability.
2.3.6 How Aircraft Systems Should Interface with TCAS II.
2.3.6.1 Pressure altitude information.
The pressure altitude data must be from the most accurate source available in the aircraft and it must be the same data the associated Mode S transponder transmits. The accuracy of the altitude data must be at least that specified in RTCA/DO-185A or RTCA/DO-185B, paragraph 3.2.8 as applicable. You must show that the resolution of the altimetry source is compatible with TCAS II. The altitude source with the finest compatible resolution must be used. When available, the resolution should be in increments of 10 feet or less. Also provide information to indicate when the pressure altitude information is invalid.
2.3.6.2 Radio altitude information.
2.3.6.2.1 Provide radio altitude information to the TCAS II to inhibit:
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2.3.6.2.2 INCREASE DESCENT RAs below 1650 ft AGL while climbing and below 1450 ft AGL while descending,
2.3.6.2.3 DESCEND RAs below 1200 ft AGL while climbing and below 1000 ft AGL while descending,
2.3.6.2.4 All TA voice messages (aural traffic advisories) below 400 ft AGL while descending and below 600 ft AGL while climbing, and
2.3.6.2.5 All RAs below 1100 ft AGL while climbing and below 900 ft AGL while descending, to allow automatic sensitivity level selection when close to the ground, and to determine that individual targets are on the ground.
2.3.6.2.6 Also provide information to indicate when the radio altitude information is invalid.
2.3.6.3 Aircraft configuration.
Use discrete information from flaps, slat, landing gear, and/or other aircraft configuration sensors to ensure that TCAS II appropriately inhibits CLIMB and INCREASE CLIMB RAs to the airplane performance limits as described in paragraph 2.3.4 and 2.3.5.
2.3.6.4 Aircraft identification.
Provide discrete information to the Mode S transponder for the unique aircraft Mode S identification code and its maximum airspeed capability.
2.3.6.5 Attitude.
The system may provide aircraft pitch and roll attitude to assist with stabilization of the directional antenna function to assure surveillance and to ensure normal aircraft maneuvers don’t affect TA display data. If TCAS II uses attitude information, provide information to indicate when the attitude data are invalid.
2.3.6.6 Heading.
The system may provide aircraft heading for the TA display reference presentation. If it does, it must also indicate when the heading data are invalid.
2.3.6.7 System failure display.
Provide an appropriate level alert in accordance with Section 2.2.10 to indicate when RAs are not possible due to failure of the TCAS II equipment or any of its sensors or displays.
Note: Section 2.3.8.2 has system safety analysis requirements for failure to provide an RA when required without indication of loss of RA capability.
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2.3.6.8 Altitude alerter data.
You may provide the current clearance altitude from the altitude alerter to enable TCAS II to select RAs that are more consistent with the aircraft’s altitude clearance once it resolves the immediate collision threat.
Note: Altitude alert functionality is optional per RTCA/DO-185A and RTCA/DO-185B. Not all TSO-C119( ) TCAS II units will have this option available.
2.3.6.9 Mode S Transponder Gillham altitude input requirements.
The Gillham format uses 11 discrete wires that, depending on which wires are turned off or on, represent an altitude value. The Gillham format is sometimes called a blind encoder, as there is no error detection and/or correction on the wires. For this reason, ARINC 718, Mark 3 Air Traffic Control Transponder (ATCRBS/MODE S), dated December 1989, states:
“Pins have been reserved to permit the direct application of Gillham code data to the transponder. This practice is not encouraged because of concerns that a “stuck bit” in the coded input could be the cause of serious errors in TCAS II resolution advisories.” This is a failure mode peculiar to the Gillham code against which protection is virtually impossible. If you cannot avoid using Gillham coded altitude for the TCAS II installations, you must connect two sources of altitude information to the transponder and compare their values. The system must annunciate all transponder altitude comparator failures.
2.3.6.10 Hybrid surveillance failure annunciations (TSO-C119d and later units).
For aircraft equipped with centralized alert and warning system and or an onboard maintenance system, you should consider integrating the hybrid surveillance alerting functionality into the system so as to alert the crew with an appropriate failure annunciation. Refer to section 2.3.9 for more information.
2.3.7 Verifying and Validating TCAS II Software. For the first installation of a manufacturer’s TCAS II equipment, you must verify and validate TCAS II software using the procedures below. Also, apply these procedures to subsequent software changes to a manufacturer’s TCAS II equipment. A manufacturer may provide a design that partitions the software that affects RAs from other software, such as that necessary for the traffic display. The TCAS II manufacturer may not use the minor change authority of the TSO system to change any software in the same partition as the software that affects RAs.
2.3.7.1 Verification and validation of TCAS II software represents a unique challenge. A formal statechart representation in the CAS requirements specification (CRS) in RTCA/DO-185A, Volume II and RTCA/DO-185B, Volume II, specifies collision avoidance algorithms, commonly called “the CAS logic,” in detail. In addition, Attachment A of Volume II provides a
2-21 software design specification in pseudocode that meets these requirements. We require this level of detail because the coordination algorithms in the CAS logic assume that the software that all manufacturers implement will have exactly the same CAS logic.
However, the manufacturer of the TCAS II equipment must develop the surveillance software necessary to establish and maintain the relative tracks of nearby transponder-equipped aircraft and the software necessary to provide the interface with the Mode S transponder and with other aircraft sensors and displays. This hybrid approach to the specification of the software requirements means that the FAA and our contractors have satisfied the application of the software criteria in RTCA/DO-178B, Software Considerations in Airborne Systems and Equipment Certification, dated December 1, 1992, for the detailed CAS requirements and the pseudocode software design, while the remaining requirements of RTCA/DO-178B (considering any applicable provisions of AC 20-115C, Airborne Software Assurance, dated July 19, 2013) or DO-178C, dated December 13, 2011, as applicable, are the responsibility of the manufacturer.
2.3.7.2 If the system uses software for the display of TCAS II RAs or in the operation of the Mode S transponder data link, you must do the verification and validation of this software to Level B requirements, as defined in RTCA/DO-178B/C. Also, apply these procedures when the TCAS II manufacturer develops the software requirements for the TCAS II processor associated with functions other than surveillance or the CAS logic. With the software design specified in RTCA/DO-185A, Volume II or RTCA/DO-185B, Volume II, the manufacturer of the TCAS II processor should conduct code walk-throughs and develop and perform module tests and module integration tests to verify that the implementation of the specified software design is correct. This includes the surveillance software necessary to establish and maintain the relative tracks of nearby transponder-equipped aircraft.
2.3.7.3 The functional tests required by TSO-C119b and TSO-C119c/d/e, as described in RTCA/DO-185A, Volume I and RTCA/DO-185B, Volume I respectively, do not provide complete testing for the TCAS II processor software. However, coverage analysis performed on the CAS test suite, described in Volume I, demonstrated that the CAS test suite tests each column of every transition table and macro, and each identity transition in the CAS requirements specification in RTCA/DO-185A, Volume II or RTCA/DO-185B, Volume II. Thus, the CAS test suite provides more than full decision coverage (but not full condition coverage) as defined in RTCA/DO-178B. TCAS II manufacturers must develop additional functional tests that correspond to the detailed requirements that they develop for the TCAS II processor. The potential consequences of software errors in the TCAS II processor or resolution display require the manufacturer to provide a structural coverage analysis showing single
2-22 condition test coverage of all instructions at the source code that can affect the generation and display of RAs. These tests may be a combination of module tests, module integration tests and functional tests.
2.3.7.4 Equipment produced under a TSO has obtained FAA concurrence that the software for the equipment was developed in accordance with RTCA/DO- 178B/C to the software level the TSO specifies. Subsequent installations of the same TCAS II equipment on other aircraft types do not require any additional verification if the software and the interface is not changed.
2.3.8 Failure Conditions System Safety Assessment and Design Assurance. Unannunciated failures of the TCAS II equipment, its associated transponder, or sensors or displays that could generate an incorrect or false RA, or result in a missing RA, must be improbable. This can be accomplished using the methods described in AC 25.1309-1A, System Design and Analysis. A functional hazard assessment (FHA), a failure modes and effects analysis (FMEA), and a quantitative probability analysis of the TCAS II equipment, Mode S transponder, displays, and sensors (including altitude information sources) will normally be necessary to show that the system design meets the probabilities specified for the following failure conditions.
Note: Appendix E, Section E.1, Definitions, gives the definitions of a missing RA, incorrect RA, and false RA.
2.3.8.1 The probability of failure of the installed system to perform its intended function from a reliability and availability perspective should be shown to be no greater than 1.0 x10-3 per flight hour.
2.3.8.2 The probability of a missing RA, without indication of loss of capability to generate an RA, should be shown to be no greater than 1.0 x 10-4 per flight hour in the terminal environment and 1.0 x 10-5 per flight hour in the enroute environment.
2.3.8.3 The probability of a false RA aural and visual alert due to a failure of the system should be shown to be no greater than 1.0 x 10-4 per flight hour in the terminal environment and 1.0 x 10-5 per flight hour in the enroute environment.
2.3.8.4 Software that presents incorrect RA aural and visual alerts, or results in a missing RA, is considered a hazardous failure condition. Develop software involved in generating RAs to RTCA/DO-178B/C, Level B standards.
2.3.8.5 The probability of an incorrect RA aural and visual alert due to a failure of the hardware should be shown to be no greater than 1.0 x 10-4 per flight hour in the terminal environment and 1.0 x 10-5 per flight hour in the enroute environment.
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2.3.8.6 The frequency of encounters where another aircraft could present a potential threat depends on the density of aircraft in the airspace. In terminal airspace, you may assume the frequency to be once every 10 hours and, in enroute airspace, it may be once every 200 hours. You may establish different frequencies based on operational data. Provide these analyses for the first installation of TCAS II equipment on a new model aircraft. For subsequent installations of the same equipment in other aircraft, you may use some of the same analyses paying particular attention to the differences in the altitude sensors that are used.
2.3.9 Maintenance Considerations for Hybrid Surveillance Functionality (TSO-C119d and later).
2.3.9.1 RTCA/DO-300A section 2.2.10, Monitoring Requirements, provides a means for annunciation or recording of failures of own-ship latitude, longitude and/or ground speed inputs. Note that a failure of any of these inputs will not cause TCAS to fail, but it will disable the hybrid surveillance functionality.
2.3.9.2 To ensure that latent failures don’t exist in airborne TCAS II units for long periods of time, the system must annunciate failures of hybrid surveillance to the flight crew, or there must be periodic scheduled maintenance tasks to check hybrid surveillance functionality. The instructions for continued airworthiness (ICA) must also require operators to periodically report reliability of the hybrid surveillance functionality. Depending on the level of avionics integration in the aircraft, you can use different methods to ensure the continued airworthiness of the hybrid surveillance such as:
2.3.9.2.1 For those aircraft equipped with an engine indicating and crew alerting (EICAS) system (or other similar annunciation system) integrate the failure information into the warning system such that a failure of hybrid surveillance is annunciated to the flight crew.
2.3.9.2.2 For aircraft equipped with an onboard maintenance computer interfaced with TCAS, add a scheduled maintenance task to the aircraft’s maintenance program to check for presence of any existing or past failures of hybrid surveillance. Take corrective action as specified by the TCAS manufacturer.
2.3.9.2.3 For aircraft without a centralized warning system and/or an onboard maintenance computer, add a scheduled maintenance task to the aircraft’s maintenance program to check for presence of any existing or past failures of hybrid surveillance and to ensure hybrid surveillance is functional.
Take corrective action as specified by the TCAS manufacturer.
2.3.9.2.4 If a scheduled maintenance task is employed, the installer must establish the initial frequency of the task in conjunction with the manufacturer of
2-24 the TCAS equipment but on a frequency not to exceed two calendar years between tasks. Operators can use normal maintenance escalation procedures later to extend the maintenance frequency if they provide adequate justification to do so to the responsible ACO. Coordinate any such extension request with the ACO prior to implementation of changes.
2.3.9.3 The ICA must require operators of TCAS equipment with hybrid surveillance to report hybrid surveillance maintenance history to the TCAS manufacturer periodically but not to exceed 18 calendar months between reports.
2.3.10 Populating Mode S Transponder registers 4016 and 6216 (if implemented).
Some airspace regulations require the transponder to report short term intent data, such as the Selected Altitude data, in transponder replies or via ADS-B. For example, 14 CFR § 91.225 requires that by Jan 1, 2020 specific message elements must be broadcast. Some of those elements are contained in the BDS 6216 register, such as SIL and NACP. Refer to AC 20-165B, Airworthiness Approval of ADS-B Out Systems, for more information on compliance with the requirements of 14 CFR 91.225 and 14 CFR § 91.227. When complying with either the EU Enhanced Surveillance rule or the U.S.
ADS-B rule, the short term intent fields are only required to be implemented if the data is available on the aircraft via a digital interface. For example, there is no expectation that a new autopilot must be installed to comply with reporting Selected Altitude if it is not available from the existing system on the aircraft. Any data that is not available on the aircraft should be reported as zero.
2.3.10.1 Selected Vertical Intention (BDS register 4016). If available, interface the transponder to the aircraft systems that provide vertical intention information for the various subfields in register 4016 e.g. MCP/FCU selected altitude, FMS selected altitude, etc. Appendix F provides guidance for interfacing to these systems.
2.3.10.2 Target State and Status Information (BDS register 6216). If available, interface the transponder to the aircraft systems that provide the transponder with state and status information for the various subfields in register 6216 e.g. SIL supplement, NACP, NICBARO, barometric pressure setting, selected heading, etc. Appendix F provides guidance for interfacing to these systems.
3-1 CHAPTER 3. TEST AND EVALUATION (INITIAL APPROVAL).
3.1 General.
Test the first installation of a manufacturer’s TCAS II or Mode S transponder system.
This will verify the design and installation performs its intended function under the expected operating conditions, and that there are no adverse interactions between the TCAS II or Mode S transponder and existing aircraft systems. The test will also show that other aircraft equipment has not been adversely affected.
3.2 Create a Test Plan.
Provide a test plan that includes adequate testing to perform this verification. This test plan will generally require a combination of ground tests, basic flight tests, and flight tests involving planned encounters with another TCAS II equipped aircraft. You can use an aircraft other than a transport category aircraft for either the TCAS II installation or for the air-to-air cooperative flights. The rest of this chapter lists and explains the minimum elements of the test plan.
3.2.1 Basic Ground Tests.
3.2.1.1 Bearing accuracy.
Demonstrate the bearing estimation accuracy of the TCAS II system as installed in the aircraft. Measure the bearing accuracy using a calibrated antenna range that allows precise echo controlled, far field, angle-of-- arrival measurements at or slightly above zero degrees elevation and over 360 degrees in azimuth. You may also measure the bearing accuracy using a fixed transponder location while rotating the test aircraft on a compass rose while measuring the bearing angles at 30-degree intervals.
Alternately, you may keep the airplane in a fixed position and move the transponder (refer to Appendix B for cautionary note on testing). You may do a manual readout of the bearing estimate directly from a plan position display on the traffic advisory display. Alternatively, you may automatically record the bearing estimates or read them from a special test display. A maximum error of ±15 degrees in azimuth is acceptable;
however, larger errors are acceptable in the area of the tail (for example, within ±45 degrees of the tail) when that area is not visible from the cockpit. In this case, aircraft structure may interfere with the signal path.
3.2.1.2 Sensor failures.
Evaluate simulated failures of the aircraft sensors integrated with TCAS II to determine that the resulting system failure state agrees with the predicted results. These tests should be part of the ground test plan.
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3.2.1.3 Electromagnetic Compatibility (EMC).
Demonstrate that the TCAS II equipment is electromagnetically compatible with previously installed systems or equipment, and is not a source of adverse conducted or radiated interference, and that conducted or radiated interference from previously installed systems and equipment does not adversely affect operation of the TCAS II equipment.
Specifically demonstrate that the TCAS II equipment is electromagnetically compatible with the weather radar, particularly if operating in the C-band.
3.2.1.4 Evaluate the general arrangement and operation of controls, displays, circuit breakers, annunciators, and placards of the TCAS II system.
Conduct a human factors evaluation of the controls, displays and annunciators. Evaluate the TCAS controls and the controls of installed systems that interact with TCAS (for example, transponders) to determine that the control design and location prevents inadvertent actuation.
Evaluate TCAS displays and annunciations to determine that they support flight crew awareness of TCAS status changes which could result from TCAS mode selections, intentional pilot actuation of other installed systems, or inadvertent pilot actions with TCAS or other installed systems.
Evaluate TCAS displays to ensure all information is, at a minimum, legible, unambiguous, and attention-getting (as applicable). In particular, where transponder functions are integrated with other system controls, ensure that unintended transponder mode switching, especially switching to STANDBY or OFF, is not possible. Pay close attention to line select keys, touch screens or cursor controlled trackballs as these can be susceptible to unintended mode selection resulting from their location in the flight deck (for example proximity to a foot rest or adjacent to a temporary stowage area).
3.2.1.5 Evaluate the TCAS II self-test features and failure mode displays and annunciators.
Verify that a TCAS failure and TCAS in the standby mode are properly annunciated in accordance with sections 2.2.10 of this AC.
3.2.1.6 Verify proper interface of the pressure altitude source and radio altimeter with the TCAS II equipment.
3.2.1.7 Verify that the windshear and the ground proximity warning system/terrain awareness warning system (GPWS/TAWS) warnings along with any other higher priority alerts and TCAS II voice alerts are compatible. Also, verify that the flight crew can clearly understand windshear or GPWS/TAWS warnings and that TCAS II automatically switches to the TA Only mode when TCAS II and windshear voice or GPWS/TAWS announcements simultaneously occur. The alert priorities should be windshear, GPWS/TAWS and then TCAS II.