Appendix 2
b. Vertical tracking performance from 700’ HAT to 200’ HAT should be stable without large deviations (i.e., within ±75 microamps deviation) from the indicated path.
6.2.3. GLS [PoC]. Paragraph 5.3 provides background GLS considerations.
a. Lateral tracking performance from 1000’ HAT to 200’ HAT should be stable without large deviations (i.e., within ±50 microamps deviation) from the indicated course or path, or equivalent.
b. Vertical tracking performance from 700’ HAT to 200’ HAT should be stable without large deviations (i.e., within ±75 microamps deviation) from the indicated path, or equivalent.
6.2.4. RNP. The accuracy criteria for RNP are designed to enable a seamless transition from en route RNP to approach RNP. RNP operations are based upon the accuracy of the airplane flight path in absolute terms with respect to the defined flight path over the ground. The Total System Error (TSE) will be characterized by the combined performance of airplane systems and any navigation aids. The certification plan should identify any navigation aid(s) on which the RNP performance will be established and how the airplane performance interacts with the navigation aid(s) to meet the TSE performance requirements. The certification plan should identify the assumed relationship between airplane performance and any navigation aid performance.
a. The approach RNP is specified from the FAF to the point along the final approach segment at which the lowest applicable Decision Altitude (Height) (DA(H)) typically is applied. There may be one or more levels of RNP specified on a final segment. Missed approach RNP, or levels of RNP if more than one level of RNP is specified, is typically specified from a point related to the lowest applicable DA(H), and typically continues to a missed approach holding fix or missed approach waypoint. RNP also may be applied to a “go-around safety” assessment. When applied to a “go-around safety assessment,” the RNP level and associated obstacle clearance start at the end of the touchdown zone with an expanding lateral area that widens to match the level of RNP used, and then continues at the RNP level(s) specified. The expanding lateral area starts on the centerline for the approach at the end of the touchdown zone and widens at a 7.5 degree splay, or ICAO 1:8 splay, depending on procedure development criteria used. It is applicable from the end of a touchdown zone to reaching the missed approach holding fix or applicable missed approach waypoint (See Appendix 5).
b. Assumptions regarding the performance for any radio navigation aid(s) used should be consistent with ICAO Annex 10 or an equivalent State standard. In cases where site-specific geometry must be considered in the evaluation of the NSE, limits on the assumed geometry should be identified
c. The guidance or control system shall be demonstrated to maintain a flight path which tracks the defined flight path to the RNP Type as specified in Paragraph 4.5 of the body of this AC, as applicable.
6.2.5. Flight Path Definition. Refer to Paragraph 4.6 in the main body of this AC for consideration on Flight Path Definition when navigation aids are used which do not have the required flight path inherent in the structure of the signal in space.
6.2.6. Area Navigation Systems. The accuracy requirements for area navigation systems are as specified in AC 25- 15, Approval of Flight Management Systems in Transport Category Airplanes, AC 20-129, Airworthiness Approval of Vertical Navigation (VNAV) Systems for Use In the U.S. NAS and Alaska, and AC 20-130, Airworthiness Approval of Navigation or Flight Management Systems Integrating Multiple Navigation Sensors, as amended. In addition, criteria described in the table below may alternately be met and referenced in the AFM.
The guidance or control system shall be demonstrated to track the lateral and vertical flight path or lateral flight path alone, if applicable, to one of the levels shown below.
See paragraph 4.4.4. in the main body of this AC for vertical performance specification.
Appendix 2 The basis for demonstration, or the demonstrated values, should be referenced in the AFM
6.3. Approach System Integrity Requirements. The applicant shall provide the certification authority with an overall operational safety assessment plan for the use of systems other than ILS or MLS for “path in space” guidance.
This plan shall identify the assumptions and considerations for the non-aircraft elements of the system and how these assumptions and considerations relate to the airplane system certification plan.
a. The onboard components of the landing system, considered separately and in relation to other associated onboard systems, should be designed to comply with Title 14 of the Code of Federal Regulations (14 CFR) part 25, section 25.1309, considering any specific safety-related criteria identified in this appendix, or as identified in accordance with the operating rules.
b. The following criteria are provided as advisory material for the application of section 25.1309 to Landing Systems:
6.3.1. ILS. The aircraft system response to loss of ILS guidance signals (localizer and glideslope) shall be established.
6.3.2. MLS. The aircraft system response to loss of MLS guidance signals (elevation and azimuth) shall be established.
6.3.3. GLS. The aircraft system response to loss of GLS guidance signals shall be established.
6.3.4. RNP. The aircraft system response to loss of the navigation service(s) used to conduct the RNP operation shall be established.
a. The aircraft system response during any switch over to alternate navigation services shall be established.
b. It shall be demonstrated that the airplane will maintain the required flight path within the containment limits
(i.e., 2 times the RNP value) when un-annunciated failures not shown to be extremely remote (probability in the order of 10-7 per approach, or less) are experienced.
6.3.5. Area Navigation Systems. The integrity requirements for area navigation systems are as specified in AC 25- 15, as amended, or equivalent.
6.4. Approach System Availability Requirements. Below 500 ft. on approach, the demonstrated probability of a successful landing should be at least 95% (i.e., no more than 5% of the approaches result in a go-around, due to the combination of failures in the landing system and the incidence of unsatisfactory performance). In addition, a dual or single area navigation (RNAV) approach system installation should meet the availability requirements consistent with the operational objective of 14 CFR part 121, section 121.349, (as applicable to standard Operations Specifications (OpSpecs)).
6.5. Go-around Requirements. A Go-around may be required following a failure in the Approach System, as required by the flightcrew or by Air Traffic Service (ATS) at any time prior to touchdown.
a. It should be possible to initiate a missed approach at any point during the approach until touchdown on the runway. It should be safe to initiate a missed approach that results in a momentary touchdown on the runway.
b. A go-around should not require unusual pilot skill, alertness, or strength.
c. The proportion of approaches terminating in a go-around below 500 ft. (150 m) due to the combination of failures in the landing system and the incidence of unsatisfactory system performance may not be greater than 5%.
d. Information should be available to the operator to assure that a safe go-around flight path can be determined.
Appendix 2
6.6. Flightdeck Information, Annunciation, and Alerting Requirements. This section identifies information, annunciations and alerting requirements for the flight deck.
The controls, indicators and warnings must be designed to minimize crew errors that could create a hazard. Mode and system malfunction indications must be presented in a manner compatible with the procedures and assigned tasks of the flightcrew. The indications must be grouped in a logical and consistent manner and be visible under all expected normal lighting conditions.
6.6.1. Flightdeck Information Requirements. This section identifies requirements for basic situational and guidance information.
a. For manual control of approach flight path, the appropriate flight display(s), whether head down or head up, must provide sufficient information, without excessive reference to other cockpit displays, to enable a suitably trained pilot to:
(1) maintain the approach path
(2) to make the alignment with the runway, and if applicable, safely flare and roll out, or
(3) go-around.
b. Sufficient information should be provided in the flight deck to allow the pilots to monitor the progress and safety of the approach operation, using the information identified above and any additional information necessary to the design of the system.
c. Required flight performance monitoring capability includes at least the following:
(1) unambiguous identification of the intended path for the approach, and, if applicable, safely flare and roll out, (e.g., ILS/MLS approach identifier/frequency, and selected navigation source), and
(2) indication of the position of the aircraft with respect to the intended path (e.g., raw data localizer and glide path, or equivalent).
6.6.2. Annunciation Requirements. A positive, continuous, and unambiguous indication should be provided for the modes actually in operation, as well as those that are armed for engagement. In addition, where engagement of a mode is automatic (e.g., localizer and glide path acquisition), clear indication must be given when the mode has been armed by either action of a member of the flightcrew, or automatically by the system (e.g., a pre-land test - LAND 3).
6.6.3. Alerting. Alerting requirements are intended to address the need for warning, caution, and advisory information for the flightcrew.
6.6.3.1. Warnings. Section 25.1309 requires that information must be provided to alert the crew to unsafe system operating conditions and to enable the crew to take appropriate corrective action. A warning indication must be provided if immediate corrective action is required. The design should account for crew alerting cues, corrective action required, and the capability of detecting faults.
6.6.3.2. Cautions. A caution is required whenever immediate crew awareness is required and timely subsequent crew action may be required. A means shall be provided to advise the flightcrew of failed airplane system elements that affect the decision to continue or discontinue the approach.
For RNP systems, the guidance or control system shall indicate to the flightcrew when the Actual Navigation Performance (ANP) exceeds the RNP
Appendix 2
6.6.3.3. System Status. Appropriate system status and failure annunciations suited to the guidance systems used, navigation sensors used, and any related aircraft systems (e.g., autopilot, flight director, electrical system) should be provided for the operator to determine prior to departure and the flightcrew to determine after departure, the capability of the airplane approach system components to accomplish the intended approach.
a. While en route, the failure of each airplane component affecting the approach capability should be indicated without flightcrew action. The indication should be an advisory (i.e., not a warning or caution, annunciates without flightcrew action, but does not demand immediate flightcrew attention), unless the failure requires a warning or caution for other reasons (e.g., autopilot disconnect warning).
b. A means shall be provided to advise the flightcrew of failed airplane system elements that affect the decision to continue to the destination or divert to an alternate.
c. System Status indications should be identified by names that are different than operational authorization categories (e.g., do not use names such as “CAT I,” “CAT II,” “CAT III”).
6.7. Multiple Landing Systems and Multi-mode Receivers (MMR) for Category I. International agreements have established a number of landing systems as an acceptable means to provide guidance to support the conduct of an instrument approach. This section identifies unique requirements which relate to airplane systems which provide the capability to conduct approach and landing operations using these multiple landing systems (e.g., ILS, MLS, GLS). Typically these multiple landing systems are implemented through use of one or more multi-mode navigation receivers (MMR), capable of providing navigation information for ILS, MLS, and GLS or any one or more combinations of these landing sensor systems.
a. ICAO has specified an ILS protection date of at least 2010 to support international approach and takeoff operations. In addition, MLS or GLS may be used on a regional basis, until GLS based approach, landing, and departure system are in worldwide use. Accordingly, an operator may elect to use ILS, ILS/MLS, ILS/GLS, or ILS/MLS and GLS. If a Multi-mode Receiver (MMR) is used, MMR characteristics should be consistent with applicable related ARINC characteristics for MMR.
b. For systems which elect to use MLS, either FAA criteria or JAR-AWO as amended, (e.g., NPA AWO 9), may be used as a consideration in defining the airworthiness requirements for MLS certification.
6.7.1. General Requirements. Where practicable, the flight deck approach procedure should be the same irrespective of the navigation source being used.
a. A means (for example, the current ILS audio idents) should be provided to confirm that the intended approach aid(s) has been correctly selected.
b. During the approach, an indication of a failure in each non-selected airplane system element must be provided to the flightcrew as an indication of system status; it should not produce a caution or warning;
6.7.2. Indications. The following criteria apply to indications in the flight deck for the use of a multi-mode landing system:
The loss of acceptable deviation data shall be indicated on the display. It is acceptable to have a single failure indication for each axis common to all navigation sources.
6.7.3. Annunciations. The following criteria applies to annunciations in the flight deck when using a multi-mode approach system:
a. The navigation source (e.g., ILS, MLS, GLS, FMS) selected for the approach shall be positively indicated in the primary field of view at each pilot station;
Appendix 2
b. The data designating the approach (e.g., ILS frequency, MLS channel, GLS approach identifier) shall be unambiguously indicated in a position readily accessible and visible to each pilot;
c. A common set of mode ARM and ACTIVE indications (e.g., LOC and GS) is preferred for ILS, MLS, and GLS operations;
d. A means should be provided for the crew to determine a failure of the non-selected navigation receiver function, in addition to the selected navigation receiver function. When considering equipment failures, the failure indications should not mislead through incorrect association with the navigation source. For example, it would not be acceptable for the annunciation “ILS FAIL” to be displayed when the selected navigation source is MLS and the failure actually affects the MLS receiver.
6.7.4. Alerting. Flight operations require alternate airports for takeoff, en route diversion, and landing. These alternate airports may have different landing systems. Flight operations may be planned, released, and conducted on the basis of using one or more landing systems.
a. The capability of each element of a multi-mode approach and landing system shall be available to the flightcrew to support dispatch of the airplane.
b. A failure of each element of a multi-mode approach and landing system must be indicated to the flightcrew without pilot action, as an advisory (i.e., not a warning or caution, does not demand immediate flightcrew attention), during en route operation.
c. A failure of the active element of a multi-mode approach and landing system during an approach shall be accompanied by a warning, caution, or advisory (i.e., not a warning or caution, annunciates without flightcrew action, but does not demand immediate flightcrew attention), as appropriate.
d. An indication of a failure in each non-selected element of a multi-mode approach and landing system during an approach may be made available to the flightcrew as an advisory (i.e., not a warning or caution, annunciates without flightcrew action, but does not demand immediate flightcrew attention), but should not produce a caution or warning.
6.7.5. Multi-mode Receivers (MMR). For MMRs using more than one type of landing system, the means of compliance required for certification can be simplified, provided the applicant provides appropriate justification.
This section provides guidance for retrofit certifications, for “ILS Look alike” applications, and for certification of ILS installations with either new or modified receivers.
Typical receiver configurations for retrofit applications include:
a. An ILS receiver from a new supplier;
b. A modified ILS receiver from the same supplier (e.g., for purposes of providing improved FM Immunity);
c. A re-packaged receiver from the same supplier (e.g., the ILS partition in an MMR, or the transition from ARINC 700 to 900 series equipment);
d. A stand-alone MLS receiver (“ILS look alike”);
e. An MLS partition in an MMR (“ILS look alike”);
f. A stand-alone GLS receiver (“ILS look alike”); or
g. A GLS partition in an MMR (“ILS look alike”).
Appendix 2
6.7.5.1. “ILS Look alike” Definition Applicable to MMR. “ILS Look alike” is defined as the ability of a non-ILS based navigation receiver function to provide operational characteristics and interface functionality to the rest of the aircraft equivalent to that provided by an ILS-based receiver function. Specifically in the case of an MLS or GNSS (GLS) based receiver function, the output should be in DDM/microamps, with a sensitivity equivalent to an ILS receiver taking account of the effects of runway length.
6.7.5.2. General Certification Considerations.
6.7.5.2.1. Certification Process. An “impact assessment” should address any new receiver functionality considering:
a. Differences between the current basis of certification and that requested (if applicable).
b. The functionality being added.
c. Credit that can be taken for the existing approval.
6.7.5.2.2. Equipment Approval. TSO/MOPS compliance should be demonstrated where appropriate, including software qualification and receiver environmental qualification to the appropriate levels.
6.7.5.2.3. Aircraft Installation Approval (14 CFR Part 25). The following should be considered:
a. Impact on airplane system safety assessments.
b. Radio approval (e.g., antenna positions, range, polar diagrams, coverage, compatibility between receiver and antenna).
c. EMI/EMC testing.
d. Functional integration aspects of the receiver with respect to other systems, controls, warnings, displays.
e. Electrical loading.
f. Flight data recorder requirements.
g. Suitable Aircraft Flight Manual (AFM) provisions.
h. Certification means of compliance for the receiver installation (e.g., specification of ground and/or flight testing, as necessary).
6.7.5.2.4. Alternative Means of Compliance using JAR-AWO. JAR-AWO may be considered as an acceptable means of compliance for ILS or MLS if the applicant establishes that the proposed new or modified navigation receiver configuration can be considered to have “ILS Look alike” characteristics. The following interpretative material to existing ACJ may be considered for that part of the certification affected by the revised installation:
ACJ AWO 131 Performance Demonstration. 2.1 Flight Demonstrations - Program of Landings for Certification.
ACJ AWO 161(b) Failure Conditions.
ACJ AWO 231 Flight Demonstration. 1.1 Continuous Method (Analysis of Maximum Value).
ACJ AWO 431 Performance (Interpretative Material).
Appendix 2
6.7.5.2.5. Recertification of an ILS function following the Introduction of a New or Modified ILS Navigation Receiver Installation. The certification program should consider the differences between the new configuration and the pre-existing ILS receiver system. An “impact assessment” may be used to establish a basis for certification.
6.7.5.2.5.1. New or Modified ILS Impact Assessment.
a. An impact assessment should consider the following aspects of the new or modified ILS receiver, or receiver function, for equivalence with the existing ILS receiver configuration:
(1) hardware design;
(2) software design;
(3) signal processing and functional performance;
(4) failure analysis;
(5) receiver function, installation and integration (e.g., with controls, indicators and warnings).
b. The impact assessment should also identify any additional considerations such as:
(1) Future functionality provisions which have no impact on system operation;
(2) Shared resources to support future functionality.
Based upon the assumption that the ILS receiver, or receiver function, can be shown to be equivalent to the current ILS configuration, the applicant may propose that the new installation be treated as a new ILS receiver for installation on a given airplane type.
6.7.5.2.5.2. New or Modified ILS Failure Analysis. The failure characteristics of the new or modified installation should be reviewed, equivalent to systems using ILS data, to ensure that the failure characteristics are compatible with and do not invalidate any original or previous safety assessments.
6.7.5.2.5.3. New or Modified ILS Autoland or HUD Guidance Landing Function Flight Testing (if necessary).
For systems intended to provide Autoland or HUD guidance landing function using a new ILS, MLS, GLS, or combined MMR receiver, a flight test program of typically a minimum of eight approaches terminating in a successful (automatic or HUD) landing and rollout (if applicable) using the flight control/guidance system, including a minimum of two ILS facilities should be completed. Approaches should include captures from both sides of the final approach course, at angles and distances representative of typical instrument approach procedures, and, if applicable, from below and above the glideslope.
The approach and landing performance (flight path deviation, touchdown data, etc.) as appropriate, should be shown to be equivalent to that achieved in the original ILS certification. Recorded flight test data may be required to support equivalency demonstration.
A demonstration of take off guidance performance should be included where applicable.
6.7.5.2.5.4. New or Modified ILS Documentation. The following documentation should be provided for certification:
a. An Impact Assessment including effects on System Safety Assessments.
b. A Flight test report, if applicable.
Appendix 2
c. Revisions to the Flight Manual, where appropriate.
6.7.5.2.6. Recertification following the Introduction of an MLS or GLS Navigation Receiver Installation.
6.7.5.2.6.1. MLS or GLS Introduction Impact Assessment. An MLS or GLS receiver or receiver function can be certificated with an “impact assessment” similar to that required for the re-certification of a new or modified ILS receiver, provided that the unit(s) has been shown to have satisfactory “ILS Look alike” characteristics. The “impact assessment” should assess equivalent aspects of the MLS or GLS receiver or receiver function to those for the existing ILS receiver configuration.
Based upon the assumption that the MLS or GLS receiver or receiver function, can be shown to have “ILS look alike” characteristics, the applicant may propose that the new installation be treated as a new ILS receiver for approval on a particular airplane type.
6.7.5.2.6.2. MLS or GLS Failure Analysis. The failure characteristics of the new or modified installation should be reviewed, equivalent to systems using ILS data, to ensure that the failure characteristics are compatible with and do not invalidate any original or previous safety assessments.
6.7.5.2.6.3. MLS or GLS Statistical Performance Assessment. If the flight control/guidance system control algorithms are unchanged or effects of any changes are fully accounted for (e.g., navigation reference point), the statistical performance assessment of a currently certificated automatic landing system or Head Up Display landing or takeoff system should typically not have to be re-assessed for the addition of MLS or GLS functionality. This equivalence is based on the assumption that the MLS or GLS receiver, or the MLS or GLS partition of an MMR, can be shown to have satisfactory “ILS Look alike” characteristics.
6.7.5.2.6.4. MLS or GLS Antenna or Navigation Reference Point Location. The implication of differences in position of the MLS or GLS and ILS aircraft antennas or Navigation Reference Point should be assessed considering:
a. Wheel-to-threshold crossing height;
b. Lateral and vertical antenna position or navigation reference point position effects on flight guidance system performance (including any alignment, flare, or rollout maneuvers).
6.7.5.2.6.5. MLS or GLS Introduction Flight Testing (as necessary). For an installation of MLS or GLS which can be treated as a new ILS receiver, a flight test program of typically a minimum of 10 to15 approaches terminating in a landing and rollout (if applicable) using the flight control/guidance system, including a minimum of two MLS or GLS facilities for each system to be authorized should be completed. The approaches should include captures from both sides of the final approach course using representative angles and distances, should include captures from below and above the glideslope if applicable, and should include representative wind conditions where antenna or navigation reference point positions may impact performance.
The approach and landing performance (flight path deviation, touchdown data etc.) as appropriate, should be shown to be equivalent to that achieved in the original ILS certification. Recorded flight test data may be required to support equivalency.
A demonstration of take off guidance performance should be included where applicable.
6.7.5.2.6.6. MLS or GLS Introduction Documentation. The following documentation should be provided for certification of MLS or GLS:
a. An Impact Assessment including effects on System Safety Assessments.
b. A Flight test report, if applicable.
Appendix 2
c. Revisions to the Flight Manual where appropriate.
6.8. Steep Angle Approaches. The following considerations should be considered before AFM provisions are incorporated for steep angle approaches:
a. The descent gradient range to be demonstrated.
b. Suitable “touchdown zone” size considerations, if not standard.
c. Adequate descent gradient abuse recovery.
d. Adequate speed abuse recovery.
e. Engine-failure continuation safety.
f. Engine-failure balked or rejected landing safety.
g. Adverse tailwind gradients on approach.
h. Adverse tailwind component limits at touchdown.
i. De-ice and Anti-ice protection considerations.
j. Suitability of cockpit visibility during approach and flare.
k. Suitability of climb gradient achievable while in the steep angle approach configuration, as necessary.
l. Suitability of descent, flare, and touchdown sink rates.
m. Provision for drag device (e.g., spoiler or auto-feather) failure.
n. Suitability of auto-feather response and time delays, as applicable.
o. Flight guidance system compatibility with steep angle approach paths to be flown.
p. Antenna function for navigation and communication performance are satisfactory.
q. Flight guidance display systems are satisfactory.
r. Suitable procedures are provided for approach, rejected landing, and missed approach for all-engine and engine-inoperative cases, and engine failure is addressed at any time until touchdown, during rollout, or after a go around.
s. Any adverse deck angle effects or landing gear geometry effects.
7. APPROACH SYSTEM EVALUATION. An evaluation should be conducted to verify that the pertinent systems as installed in the airplane meet the airworthiness requirements of paragraph 6 of this appendix. The evaluation should include verification of approach system performance requirements and a safety assessment for verification of the integrity and availability requirements. Engine failure cases and other selected failure conditions identified by the safety assessment should be demonstrated by simulator and/or flight tests.
An applicant shall provide a certification plan(s) that describes:
Appendix 2
a. The means proposed to show compliance with the requirements of paragraph 6 of this appendix, with particular attention to methods that differ significantly from those described in this appendix.
b. How any non-airplane elements of the Approach System relate to the airplane system from a performance, integrity, and availability perspective (e.g., appropriate reference to ICAO Annex or U.S. Standard).
c. The assumptions on how the performance, integrity, and availability requirements of the non-airplane elements of the Standard Landing Aid will be assured.
d. The system concepts and operational philosophy to allow the regulatory authority to determine whether criteria and requirements in excess of that contained in this appendix are necessary.
Early agreement between the applicant and the FAA should be reached on the proposed certification plan. Upon completion of an FAA engineering design review and supporting simulation studies, a type inspection authorization (TIA) should be issued to determine if the complete installation of the equipment associated with Category I operations meets the criteria of this appendix.
7.1. Performance Evaluation. The performance assessment can be accomplished “in flight,” or credited from similar installations as follows:
a. Performance shall be demonstrated by flight test, or analysis validated by flight test, using at least 3 different representative facilities for a minimum of 9 total approaches, with a representative range of environmental and system variables which have an effect on overall performance.
b. Acceptable performance may be established as a by-product of, or in conjunction with, a more restrictive performance demonstration(s) (e.g., Basic type certification, or as a consequence of successfully meeting Category II/III criteria);
• As a dedicated qualitative “in flight” demonstration of acceptable performance; or
• By establishing similarity with other mature and acceptably performing system installations.
For this provision, “in-flight” demonstration is not necessary, but a functional ground check, bench test, or other equipment check is typically appropriate (e.g., this provision is typically used in the instance of installation of a new model of ILS, VOR, ADF, or DME receiver).
7.2. Safety Assessment. Except as required by any specific safety-related criteria identified in this appendix, or by the operating rules, a safety assessment of the approach system, considered separately and in conjunction with other systems, shall be conducted to show compliance with section 25.1309.
8. AIRBORNE SYSTEM REQUIREMENTS. This section identifies criteria applicable to specific aircraft system architecture selected to conduct the operation. This criteria is developed from operational considerations, approach system considerations, airplane system considerations, and the general operational philosophy contained in the body of this AC.
8.1. General. Various airplane systems are expected to comply with the basic performance, integrity, and availability requirements as identified in paragraph 6 of this appendix.
8.2. Autopilot. Criteria applicable to Autopilot systems is as specified by section 25.1329.
8.3. Head Down Guidance. Criteria applicable to Head Down Guidance systems are specified in the pertinent parts of paragraphs 4 and 5 of this appendix.
8.4. Head Up Guidance. The following criteria is applicable to Head Up Guidance systems:
Appendix 2
a. The workload associated with use of the HUD should be considered in showing compliance with section
25.1523.
b. The HUD display medium must not significantly obscure the pilot’s view through the cockpit window.
c. Control of Approach Flight Path - the HUD must provide sufficient guidance information, without excessive reference to other cockpit displays, to enable a suitably trained pilot to:
• maintain the approach path
• go-around
d. The pilot should be able to align with the runway without the HUD adversely affecting the pilot task. If command information is provided for the flare and landing, it must not be misleading and should be consistent with the characteristics of normal manual maneuvers.
e. If only one HUD is installed, it should be installed at the pilot-in-command crew station.
f. The HUD guidance must not require exceptional piloting skill to achieve the required performance.
g. The HUD system performance and alerting should be consistent with the intended operational use for duties and procedures of the pilot flying (PF) and pilot not flying (PNF) (see paragraphs 5.6 and 5.8 of the main body of this AC).
h. If the autopilot is used to control the flight path of the airplane to intercept and establish the approach path, the point during the approach at which the transition from automatic to manual flight takes place shall be identified and used for the performance demonstration.
i. Any transition from autopilot to HUD guidance must not require exceptional piloting skill, alertness, strength, or excessive workload.
8.5. Hybrid HUD/Autoland Systems [PoC]. The following criteria is applicable to Hybrid systems:
a. If a HUD is used to monitor an autoflight system, it should be shown to be compatible with the autoflight system and permit a pilot to detect unsuitable autopilot performance.
b. Other hybrid systems (e.g., including EVS) require a proof of concept [PoC] evaluation to establish suitable criteria.
8.6. Satellite-Based Approach System. The following criteria is applicable to satellite-based approach systems:
a. Satellite-based systems should be shown to provide equivalent or better capability than navigation systems based on VOR, DME, or ILS for comparable operations, or meet provisions applicable to RNP.
b. Satellite-based systems should not exhibit undue sensitivity to masking of satellite vehicles, or interference from onboard or external sources.
c. Satellite-based systems should not exhibit adverse characteristics during acquisition or loss of satellites.
8.7. Area Navigation Systems.
a. Area navigation systems should operate consistent with criteria specified in:
(1) AC 25-15, Approval of Flight Management Systems in Transport Category Airplanes;
Appendix 2
(2) AC 20-129, Airworthiness Approval of Vertical Navigation (VNAV) Systems for use in the U.S. NAS and Alaska; and
(3) AC 20-130, Airworthiness Approval of Navigation or Flight Management Systems Integrating Multiple Navigation Sensors, as amended, or equivalent criteria.
b. In addition, area navigation systems used for approach should have at least the following characteristics:
(1) If the operational software (ops program) is modifiable or loadable (e.g., by maintenance action) a “Version” identification must be provided and available for display to the pilot or maintenance personnel (e.g., PS4052520-161, or U7.4, or B767-300.3);
(2) A suitable database must be used which can be assured to be suited for the specific aircraft and navigation system type, and which can be assessed to have current data (e.g., Navigation Database “NW19810001”);
(3) Pilot input/output functions, keys, and displays should have standard functions available, and operate consistent with industry standard conventions and practice;
(4) Single systems must be accessible and usable by either pilot located at a pilot or copilot crew station
(e.g., the PF or PNF) of a multi-crew aircraft. It is not necessary that such systems also be accessible, or easily accessible, to pilots other than the PF and PNF sitting in a jumpseat (e.g., do not need to be readily accessible to International Relief Officers (IROs)), but it is recommended that such a system be at least visible to such other pilots (if they have assigned duties) for enhancement of crew coordination and monitoring;
(5) Dual (or more) system installations must have a convenient and expedient way to “crossload” and be kept updated. Each system should have CDUs, displays, and annunciations, or equivalent that are at least visible and accessible to both the PF and PNF. This is to provide both for monitoring and use in failure cases. It is not necessary that such systems also be accessible, or easily accessible, to pilots other than the PF and PNF sitting in a jumpseat (e.g., do not need to be readily accessible to IROs), but it is recommended that such a system be at least visible to such other pilots (if they have assigned duties) for enhancement of crew coordination and monitoring;
(6) System performance must be consistent with operational authorizations sought (see paragraphs 4 and 5 of this appendix), or should be consistent with an identifiable performance standard such as for various levels of RNP;
(7) If credit is sought for operating on complex and closely spaced multiple Waypoint paths, an interface with a suitable “track up” or “heading up” navigation map display is necessary;
(8) A means to monitor lateral and vertical deviations should be provided (e.g., displacement display, progress page lateral and vertical deviation);
(9) A means must be provided to assure suitable operation or updating, and if RNP is included, to identify the level of RNP to be used, and ANP (or EPE);
8.8. Autothrottle. If autothrottle capability is installed, the applicant should identify any necessary modes, conditions, procedures, or constraints that apply to its use. Use of the autothrottle should not cause unacceptable performance of any autopilot modes intended for use, and any autopilot mode intended for use with autothrottle should not cause unacceptable autothrottle performance. The autothrottle should expeditiously capture any commanded speed adjustments, acceptably maintain speed, and not cause any hazardous conditions with normal use, or for any probable failure modes, considering pilot intervention using normal piloting skills.
8.9. Data Link [PoC]. A datalink may be used to provide data to the airplane to provide the accuracy necessary to support the approach.