AMC AWO-1 All-weather operations recertification following the installation of new or modified navigation receivers providing xLS capability
ED Decision 2022/007/R
1 Purpose
The purpose of this AMC is to provide acceptable means of compliance for retrofit certifications, addressing the certification of xLS receivers in the so-called ‘ILS lookalike’ applications, and the certification of ILS installations with either new or modified receivers.
2 Scope
CS AWO already provide acceptable means of compliance for the certification of new xLS installations. Where, for an already certified installation, it is established that the proposed new or modified navigation receiver configuration can be considered to have ‘ILS lookalike’ characteristics, the contents of this AMC may be used as an alternative for that part of the certification affected by the revised installation.
This AMC provides acceptable means of compliance for the approval of all-weather operations. Other generic certification processes (such as software, equipment, and radio approvals, etc.) remain equally applicable to new and retrofit applications. These general certification considerations are summarised for reference in paragraph 5 below.
3 Definitions
‘ILS lookalike’ is 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 those provided by an ILS-based receiver function. Specifically, in the case of an xLS receiver function, the output should be in DDM/micro amps, with a sensitivity equivalent to an ILS receiver taking account of the effects of the runway length.
‘Impact assessment’ is the justification that is provided, usually in a certification plan, to determine the scope of work and certification activity that are required for a retrofit certification.
4 Related requirements and documents
This AMC provides another means of compliance for retrofit certifications to the following CS‑AWO and CS-25 AMC material.
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AMC AWO.A.ALS.106 Paragraph 2.1 |
Flight demonstration — Programme of landings for certification |
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AMC AWO.B.CATII.113 Paragraph 1.1 |
Flight demonstration — Continuous method (analysis of maximum value) |
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Performance demonstration |
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Flight demonstration of failure conditions |
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Performance (interpretative material) |
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AMC 25.1329 Paragraph 5.3.4. |
Paragraph 5.3.4 Flight demonstration of autopilot failure conditions coupled to an ILS glide path |
5 General certification considerations
5.1 Certification process
An ‘impact assessment’ is required to determine the tasks that are required to achieve approval of the new receiver functionality in a retrofit application. Based on the ‘impact assessment’, the certification plan should consider:
(a) the differences between the current basis of certification and that requested (if applicable);
(b) the functionality being added; and
(c) the credit that can be taken for the existing approval.
5.2 Equipment approval
Suitable procedures for equipment approval should be employed. CS-ETSO compliance should be demonstrated, where appropriate, including software qualification and receiver environmental qualification to the appropriate levels.
5.3 Aircraft installation approval (CS-25)
The following should be considered for the approval of the installation:
(a) impact on aeroplane system safety assessments (SSAs);
(b) radio approval (e.g. antenna positions, range, polar diagrams, coverage, compatibility between receiver and antenna);
(c) electromagnetic interference (EMI) / electromagnetic compatibility (EMC) testing;
(d) functional integration aspects of the receiver with respect to other systems, controls, warnings, and displays;
(e) electrical loading;
(f) flight data recorder requirements;
(g) impact on the aircraft flight manual; and
(h) certification means of compliance for the receiver installation, e.g. ground and/or flight testing.
6 CS-AWO recertification of the xLS function following the introduction of a new or modified xLS navigation receiver installation
The magnitude of the certification programme will be based upon an ‘impact assessment’ of the differences between the configuration offered for certification and the pre-existing xLS receiver system installed in a given aircraft type. The ‘impact assessment’ should establish the basis and rationale for the work to be accomplished to achieve certification.
6.1 Impact assessment
The impact assessment should assess the following aspects of the new or modified xLS receiver, or receiver function, for equivalence with the existing xLS receiver configuration:
(a) hardware design;
(b) software design;
(c) signal processing and functional performance;
(d) failure analysis; and
(e) receiver function, installation and integration (e.g. with controls, indicators and alerts).
The impact assessment should also identify any additional considerations. This may include:
(a) any functionality, or provisions for future functionality, which have no impact on the functionality for which certification is sought; and
(b) any shared resources, which will support future functionality.
Based upon the assumption that the xLS receiver, or receiver function, can be shown to be equivalent to the current xLS configuration, it may be proposed that the new installation be treated as a new xLS receiver for approval on a given aeroplane type.
6.2 Failure analysis
The failure characteristics of the new or modified installation should be reviewed in the context of the safety assessments of systems using xLS data, to ensure that the failure characteristics are equivalent to, or are compatible with and do not invalidate, the current safety assessments.
6.3 Flight testing
For an installation which can be treated as a new xLS receiver, a flight test programme of typically a minimum of 10–15 approaches terminating in an automatic landing and roll‑out (if applicable) using the flight control/guidance system, including a minimum of 2 xLS facilities should be carried out. The approaches should include captures from both sides of the beam.
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 xLS certification. Recorded flight test data may be required to support the equivalency demonstration.
A demonstration of take-off guidance performance should be included where applicable.
6.4 Antenna location
The implication of differences in the position of the xLS aircraft antennas should be assessed for their impact on:
(a) the wheel-to-threshold crossing height; and
(b) the lateral and vertical performance.
6.5 Statistical performance assessment
The statistical performance assessment of a currently certified automatic landing system or a HUD system should not have to be reassessed for the addition of the xLS functionality to the aircraft provided the xLS receiver (or the xLS partition of a multi-mode receiver (MMR)) is shown to have satisfactory ‘ILS lookalike’ characteristics. This assumes that the flight control / guidance system control algorithms are unchanged.
6.6 Documentation
The following documentation should be provided for certification:
(a) an impact assessment including effects on system safety assessments (SSAs);
(b) a flight test report; and
(c) revisions to the flight manual, where appropriate.
[Issue: CS-AWO/2]