CHAPTER 5. MODEL QUALIFICATION PROCESS REQUIREMENTS
This chapter is designed to help the user of this AC design a Model Qualification Process. This process is used by the STC holder and the ACO to determine and document the applicability of an AML STC to a given airplane model. In contrast, the installation instructions are intended to be used by the installer to determine applicability of the STC to a particular serial number airplane. The Model Qualification Process is designed to be used to: 1) include a given aircraft model on the existing AML (to determine if the installation is appropriate under the AML), 2) determine if a particular model would require further compliance showing to be added to the AML, or 3) determine if an installation is complex enough to warrant an individual STC. The following list of items is meant only as a guideline and does not represent an exhaustive list of potential issues that must be addressed to qualify a model for an AML approval.
1. Evaluation of Physical Location of Installed Equipment
a. Will the equipment for the proposed modification fit in the model being considered? This should include considerations for available space for new equipment and for systems that will need to be moved or displaced to complete the modification.
b. Is the proposed installation location, or proposed alternate mounting locations, compatible with the criticality and visibility of displayed information, including required announcements and warnings?
c. Is the environment suitable for the limitations of the equipment? This should include cooling considerations.
2. Evaluation of the Applicability of the Proposed STC
a. Is a particular model airplane configured in such a way that would preclude it from being eligible for the STC, although it is listed on the AML? This might be caused by existing equipment, where the interface is not covered in the installation instructions for the system, inadequate electrical capacity because of existing equipment, or other factors.
b. Are the operational characteristics of a particular model airplane compatible with the assumptions made during the initial certification? For example, an airplane may be approved for CAT II approach from the factory, where adding new equipment and replacing it with the new system might cancel this ability.
3. Evaluation of Intended Function of the Proposed Equipment
a. Will the proposed equipment be able to perform its intended function in the model being considered?
b. Is the intended function compatible with the equipment approval for the system, including software and hardware design assurance levels?
c. Is the software development level of the proposed equipment compatible with the intended function for the category/classification of the model in question?
d. Does the intended function change for the model being considered compared to other models already on the AML? If so, the applicant may need to split the AML into sections or seek separate approvals.
4. Evaluation of the Installation Complexity of the Proposed Equipment
a. Will the proposed modification present unique model specific installation challenges for the models being considered? This should include an analysis of the complexity of the proposed modification with consideration to existing equipment that would typically appear on a given model.
b. Will the proposed installation affect the electrical load analysis, the functional hazard assessment, or the calibration/operation of existing systems?
c. How will calibration issues for the new equipment, EMI related issues, and the possible effects to the HIRF and lightning certification of the proposed model be addressed?
d. How will the proposed modification interface with other existing systems on the model being proposed? What existing equipment is acceptable to interface with the new equipment?
e. Is specific training needed to install the system? Consider the existing installation instructions to see if more model specific details are needed to include the model in question.
f. Are there continued airworthiness issues that should also be evaluated to see if any model specific issues exist? For example, consider the installation location of the equipment and whether this might influence inspection, calibration, or maintenance schedules of the equipment.
5. Evaluation of Operational Requirements of the Proposed Equipment
a. Will the proposed equipment change the operational capabilities of the model being considered? This should include an evaluation of possible changes to the following: 1) existing precision approach capabilities, 2) navigational accuracy and procedures, 3) current pilot workload, 4) special certification conditions, and 5) operational approvals for the model being proposed, such as RVSM or CAT II approval.
b. Are there model specific limits and possible additions or changes to the AFM or AFM Supplements?
6. Pilot Evaluation and Human Factors Issues for the Proposed Equipment
Will the proposed modification create any issues that would warrant a pilot evaluation or any human factors concerns for the model being considered? This should include an evaluation of existing equipment, how the modification will affect the pilot's primary field of view, and how the system will be ground and flight tested after installation.
Ground and flight test procedures should contain exact test procedures and expected response data, with clear pass/fail criteria for each test.
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Disclaimer:
The following sample document provides an example of a generic framework for the process used to show applicability of a given STC to a particular airplane model. The document proposes a structure for the formal engineering process that must be followed before a model can be added to the AML for a given STC.
The sample Model Qualification Process document is provided only as an example for the agreement between the STC holder and the ACO. It is not meant to capture all the possible information that would be required to determine applicability or use of a particular airplane for a given STC. Depending on the complexity of the system being approved, the detailed steps of this process may need to be reduced or expanded in scope to allow suitable installation and certification requirements for a particular approval.
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Appendix 1
CONTENTS
1 INTRODUCTIONA1-3
1.1 SummaryA1-3
1.2 Definitions and AcronymsA1-3
1.3 Applicable Documents and ReferencesA1-3
2 CERTIFICATION CONSIDERATIONSA1-3
2.1 AML STC DefinitionA1-3
2.2 AML STC Limitations and AssumptionsA1-3
2.3 Installation OverviewA1-4
2.4 AML Revision ProcessA1-4
3 DETERMINATION OF APPLICABILITYA1-4
3.1 Certification BasisA1-5
3.2 Prior ConsiderationsA1-5
3.3 Operational ConsiderationsA1-5
3.4 Installation ConsiderationsA1-6
3.5 Final ApprovalA1-6
4 SPECIFIC AIRCRAFT EVALUATIONSA1-6
4.1 Intended FunctionA1-7
4.2 Applicability Across Serial NumbersA1-7
4.3 Physical Location of Installed EquipmentA1-7
4.4 Interface to Existing EquipmentA1-8
4.5 Electromagnetic InterferenceA1-8
4.6 Human FactorsA1-8
5 ACCEPTANCE PROCESSA1-9
5.1 Model Qualification DiagramA1-9
List of Tables and Figures
Figure A1-1 AML Model Qualification Process DiagramA1-10
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SAMPLE DOCUMENT (CONTINUED)
1 Introduction
1.1 Summary
This section should contain a brief summary of the scope and purpose of the document, including a brief description of the certification approval project itself.
1.2 Definitions and Acronyms
This section should contain any project specific definitions and acronyms applicable for the approval.
1.3 Applicable Documents and References
This section should contain a listing of applicable certification documentation for the STC being considered, any applicable regulatory references, and other guidance suitable for a particular approval.
2 Certification Considerations
This section should contain an outline of the certification philosophy used by the ACO to approve the proposed modification. This information is provided so the reader is familiar with the basic certification assumptions surrounding the approval of the proposed modification.
2.1 AML STC Definition
This section should contain a clear definition of the AML STC as defined for the project approval in question. This includes a clear definition of the intended function of the equipment as provided in other certification documentation for the approval.
2.2 AML STC Limitations and Assumptions
This section should contain a summary list of assumptions made about the airplane, or equipment, for the initial certification that would influence the decision to include a given model on a proposed AML. One example would be the assumption that electromechanical back-up instruments are maintained and considered in the System Safety Assessment for a Primary Flight Display installation. Another example would be the software development assurance level that relates to the failure condition classification and airplane classification under AC 23.1309-1C.
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This summary list should allow an initial review by the reader to help define whether a given model should be considered for inclusion on the AML.
2.3 Installation Overview
This section should provide an outline of the installation, including a brief description of the basic steps of the installation and the equipment being installed.
If a rearrangement of existing equipment or instruments is necessary, this section should provide an outline about what is being replaced, where the new instrumentation is to be placed, and the reinstallation of existing equipment. This section should reference sections that appear later in this document and other installation documentation that provides a greater level of detail for these items.
This section should also provide an outline of whether there are model specific installation issues to be evaluated, including references to specific sections later in the document. If model specific installation instructions are needed, this section should provide a summary list of applicable installation documents. Model specific installation instructions should be used for complex installations where model-to-model variations in the installation, or system configuration, are significant. Also, a “prototyping” approach can be used, where each new model is added to the AML as installations are performed and the model specific installation issues are addressed.
2.4 AML Revision Process
This section should contain the agreed on process between the FAA and the applicant on how the AML is to be revised to add or remove a given model. This part of the document should provide a clear step-by-step process so the same method will be used each time the AML is revised. The process should state that the determining of eligibility should only be made by an individual with specific knowledge of the proposed model and the proposed modifications required by the STC. Also, AML revisions must be FAA approved. The step-by-step process should relate to later sections in this document and outline the steps for a determination of applicability.
3 Determination Of Applicability
This section should contain a summary of general steps that are used to determine if a proposed model should be included on the AML. This section should include a review of the certification basis of the proposed model, prior certification considerations applicable to the particular model, model specific installation limitations, and relevant operational considerations for the proposed model. The section should provide an outline of the
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engineering process that the installer would use to assure the installation is applicable for a particular model airplane.
3.1 Certification Basis
This section provides a detailed review of the certification basis that was briefly introduced earlier in the document for the AML approval. This should include information about the certification basis of the equipment and the airplane models on the AML. Order 8110.48 contains more detail on how to determine the certification basis for a changed product.
It is possible for an airplane on the AML to have a different certification basis than the equipment in the proposed installation. For example, applicability of an STC could be limited to older part 23 airplanes, but the proposed system could be certified to the latest amendment. The rest of the airplane is left at the older certification basis, while the latest certification requirements are applied to the proposed equipment, according to existing § 21.101 related guidance.
This section should also contain reference to any certification item that was documented in issue papers for the approval in question. This will allow the terms of that issue paper to be captured as part of the Model Qualification Process so a consistent approach can be used.
3.2 Prior Considerations
This section should list any known items, related to prior STC approvals for the airplane model being proposed for the AML that would influence the proposed modification.
This could include prior STC approvals or other considerations that are applicable to the project. For example, if a single model STC is being expanded to include other models where similarity can be clearly determined and documented, this section should contain that information.
Also, this section should outline the proposed modification that could be affected by the combined effects of other STC installations, such as critical hazard analysis details, or electrical system load analysis limitations.
3.3 Operational Considerations
This section should contain an outline of the operational considerations for the proposed modification. For example, if the system is only certified for day VFR, this section should clearly state the limitations of the system so it is not misused. As another A1-5
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example, if the proposed installation can influence previously installed equipment and change an operational approval, such as CAT II approach capability or RVSM certification, these items should be addressed in this section.
3.4 Installation Considerations
This section should contain details of the installation that may vary from model to model.
This section should state clearly whether a generic set of installation instructions are being used or if model specific installation instructions are to be used. This section should also contain a summary of the assumptions that qualify a particular airplane for the proposed installation. In the case of an antenna installation only structurally approved for installation on a nonpressurized airplane, this section should draw attention to the further certification involvement that will be needed for installation on a pressurized airplane.
The section can refer to general guidelines and reference standard practices and procedures considered acceptable by FAA regulations. For example, for a generic installation where similarity between models on the AML can be clearly documented, specific references to AC 43.13-1B, “Acceptable Methods, Techniques, and Practices - Aircraft Inspection and Repair,” and AC 43.13-2A, “Acceptable Methods, Techniques, and Practices - Aircraft Alterations,” may be acceptable.
3.5 Final Approval
The final step to include the aircraft on the STC AML is FAA approval. A form 8110-3 for Recommend Approval with a statement the proposed aircraft model(s) has been qualified through the FAA-approved Model Qualification Process and signed by an authorized DER should go with the AML data submittal. According to Order 8110.37C, the submittal should also include a clarifying note stating, "This approval is for engineering design data only and is not an installation approval." The FAA will review the form 8110-3 to approve the suggested revision to the AML as well as any applicable changes to the applicable documentation for the STC.
4 SPECIFIC AIRCRAFT EVALUATIONS
A specific aircraft evaluation is required to determine relevance of a given serial number airplane as a potential candidate for the proposed modification. An individual with specific knowledge of the aircraft make and model should perform the engineering analysis. The person’s knowledge must be extensive enough to answer each question in the AML decision tree and document those decisions to satisfy the ACO. This decision process can refer to specific written documentation from the original equipment manufacturer. This may be in the form of TCDS, specific aircraft drawings, photographs, or detailed reports.
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4.1 Intended Function
This section should refer to any differences in intended function that may be present in the proposed installation, depending on the installed equipment for a given airplane. For example, it may be possible for one piece of equipment to be installed and used differently on two airplanes of the same model if one is approved for precision approach and the other is not. For another example, a multifunction display can be installed with varying capabilities, depending on the other equipment installed in the airplane. This section should document those variations so they can be evaluated when a particular airplane is being considered for the proposed modification.
4.2 Applicability Across Serial Numbers
This section should include details on specific airplanes within a series that may not qualify for the installation or would require further certification involvement. For example, it is possible for an aircraft to have changed during its production so some serial numbers may not be applicable for a given STC while others are applicable.
4.3 Physical Location of Installed Equipment
This section should provide details of the specific installation location proposed for the modification to determine if a given model will be able to accommodate the installation.
Each aircraft identified as a potential candidate for the AML must provide a suitable mounting location for the proposed modification. The installation location may vary from model to model and from serial number to serial number, but the STC installation documentation should clearly state the installation requirements and limits for the proposed modification. This should include detailed instructions on how much an installation can vary before further certification involvement is needed.
This section should address requirements for acceptable location, structural mounting, cooling, and wiring related issues. Also, installation requirements for equipment that is sensitive to installation location because of EMI issues, such as an Attitude Heading Reference System (AHRS), should be clearly described.
For example, to install a GPS navigation system, this section should clearly state acceptable installation location, suitable remote annunciation requirements, and other items. Suitable guidance materials should be referenced where applicable, such as AC 20-138A and AC 23.1311-1A. For these installations, the GPS navigation receiver is typically found in the center radio stack. However, the location of the center radio stack varies from airplane to airplane model. This section should provide added information to clarify field of view requirements and acceptable installation locations for the AML installation.
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The proposed installation requirements should be consistent with existing FAA guidance materials suitable for the equipment. Also, references to specific sections in AC 43.13- 1B should be used, rather than general references, to document installation procedures and to satisfy the requirements of § 21.31 to describe the type design, when suitable.
4.4 Interface to Existing Equipment
The proposed modification may require interfaces into the aircraft’s existing equipment.
This section should provide enough detail for a specific model to be evaluated to make sure suitable interfacing can be performed for a given model. This could include, but is not limited to, the following:
• Navigation System Interface [(Horizontal Situation Indicator (HIS) and or Course Deviation Indicator (CDI)]
• Antenna Installations (GPS, Communication, and Navigation systems)
• Electrical System Interface (Including an electrical load analysis impact study)
• Interface to other systems, such as the Pitot Static system, autopilot, and Angle of Attack sensors.
When interfaced with external equipment, extensive instructions should be provided to ensure the interface with the equipment is properly wired, properly configured, and properly tested. The installation manual should contain detailed test procedures, with expected system response, for each interface. This can include both ground test and flight check procedures, when necessary.
4.5 Electromagnetic Interference
This section should contain specific tests to ensure the proposed installation does not electronically or magnetically interfere with existing equipment, or conversely. This section should also list any equipment in the proposed installation that may be susceptible to EMI, such as an AHRS or a GPS system. The installation instructions should include ground tests and operational flight checks.
4.6 Human Factors
This section should contain details related to human factors considerations for the proposed installation including the basic design of the system, the certification basis, the intended function of the equipment, and the installation location of the equipment.
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SAMPLE DOCUMENT (CONTINUED)
5 ACCEPTANCE PROCESS
5.1 Model Qualification Diagram
The following decision process in Figure A1 is presented as an example to determine applicability of a given model to the AML. It is a graphic representation of the decision points outlined previously in the document. Once an airplane has been identified as a potential candidate to be included on the AML, a qualified person with specific knowledge of the model in question may use this decision process to qualify the aircraft.
Specific installation questions must be answered and clearly documented to prove the applicability of a particular model.
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