Establishing the reliability of a complex COTS device that is used outside its specification (its recommended operating limits), as determined by the device manufacturer, is considered to be difficult and might introduce risks that should be mitigated.
One process to qualify the device, called an ‘uprating’ process, could be applied to verify the appropriate operation of the device itself and to guarantee that performance is achieved in the target environment in all operating conditions over the lifetime of the equipment. This uprating process focuses on the device itself and takes into account the different variations in technology (variation in performance over different batches/over different dies). This uprating process evaluates the performance of the device itself, so it is different from ED-14/DO-160 environmental qualification of equipment.
Thermal uprating is addressed in IEC/TR 62240-1. It provides information to select semiconductor devices, to assess their capability to operate, and to assure their intended quality in the wider temperature range. It also reports the need for documentation of such usage.
It is understood that each case of uprating might follow a different process depending on the ‘uprated’ characteristics (the frequency, temperature, voltage, etc.) and the performance guaranteed by the device manufacturer’s datasheet. For that reason, objective COTS-3 is separated from objective COTS-2 and is only to be applied in cases of COTS device uprating.
IEC/TR 62240-1 states the following: “For each instance of device usage outside the manufacturer's specified temperature range relevant data are documented and stored in a controlled, retrievable format.” This is considered to be a best practice for any uprating case as evidence satisfying objective COTS-3.
Note: when a simple COTS device is used outside its datasheet values, applying an uprating process would be considered to be a best practice to ensure that the device functions properly within the newly defined and intended environment/usage conditions.
3.2.2.3 Additional Information for Section 6.4.2 COTS Device Malfunctions The applicant needs access to errata information on the device during the entire life cycle of the product (before and after certification). Refer to AC 20-152A, Section 6.4.1.
In general, this assessment typically includes the analysis of which errata are, or are not, applicable to the specific installation of the equipment, and for each of the applicable errata:
• The description of the mitigation implemented, and
• The evidence that the implementation of errata mitigations are covered by relevant requirements, design data, and are verified.
The assessment of the errata of a simple COTS device is considered a best practice to remove the safety risks associated with device malfunctions.
While the applicant is expected to document the process applied for errata in the PHAC, the errata and evidence of assessment would typically be captured in other documents that can be referred to in the PHAC and HAS.
3.2.2.4 Additional Information for Objective COTS-6 on COTS Device Malfunctions It is understood that the task linked with this objective is performed in close coordination with the hardware, software, and system teams.
In order to support the safety analysis process, this objective focuses on the failure effects and not on their root causes. The hardware domain, knowing the detailed usage of the device, starts by identifying the effects of failures of the device on the intended functions. This information will be provided to the system safety process. When necessary, mitigation means will be defined and verified by the appropriate domain or across the hardware, software, and system domains.
While the applicant is expected to document the process to satisfy objective COTS-6 in the PHAC, the evidence would typically be captured in other documents that can be referred to in the PHAC and ultimately in the HAS.
When a simple COTS device interfaces with software, complying with objective COTS-6 is considered to be a best practice.
3.3 Clarification of Objective CBA-1 on Circuit Board Assembly Development In the aviation domain, the applicant typically has internal processes to develop circuit board assemblies. There is a clear benefit for the applicant (or developer of the airborne system and equipment) in having a process to address the development of a circuit board assembly (a board or a collection of boards) that encompasses the requirements capture, validation, verification, and configuration management activities and ensures an appropriate requirement flow down.
It is a common practice for the applicant’s internal process to already encompass the above-mentioned activities that satisfy objective CBA-1. Industry standards ED-80/DO- 254 or ED-79A/ARP-4754A provide guidance that may be used by applicants seeking further information.
Note 1: The applicant’s internal processes might be tailored according to the equipment and hardware complexity if necessary.
Note 2: The organization of the process life cycle data is at the discretion of the applicant’s internal process.
Note 3: T he hardware requirements may be verified at a higher level of integration.
3.4 Development of Airborne Electronic Hardware Contributing to Hardware DAL D Functions For airborne electronic hardware contributing to hardware DAL D functions, the acceptable means of compliance include ED-80/DO-254 or existing level D hardware development assurance practices that demonstrate that the requirements allocated to the DAL D airborne electronic hardware have been satisfied. Additionally, system-level development assurance practices such as ED-79A/ARP-4754A or other means may be used if the applicant can demonstrate at the system level that the requirements allocated to the DAL D airborne electronic hardware have been satisfied.
4 RELATED REGULATORY, ADVISORY, AND INDUSTRY MATERIAL
4.1 Title 14 of the Code of Federal Regulations (14 CFR) Applicable Sections 14 CFR parts 21, 23, 25, 27, 29, 33 and 35 (principally, §§ 21 subpart O, 23.2500,
23.2505, 23.2510, 25/27/29.1301, 25/27/29.1309, 33.28, and 35.23).
4.2 FAA Advisory Circulars
• AC 20-152, Development Assurance for Airborne Electronic Hardware.
• AC 20-174, Development of Civil Aircraft and Systems.
• AC 21-50, Installation of TSOA Articles and LODA Appliances.
• AC 23.1309-1, System Safety Analysis and Assessment for Part 23 Airplanes.
• AC 23.2010-1, FAA Accepted Means of Compliance Process for 14 CFR Part 23.
• AC 25.1309-1, System Design and Analysis.
• AC 27-1, Certification of Normal Category Rotorcraft (Changes 1 – 8 incorporated).
• AC 29-2, Certification of Transport Category Rotorcraft (Changes 1 – 8 incorporated).
• AC 33.28-1, Compliance Criteria for 14 CFR § 33.28, Aircraft Engines, Electrical and Electronic Engine Control Systems.
• AC 33.28-2, Guidance Material for 14 CFR 33.28, Reciprocating Engines, Electrical and Electronic Engine Control Systems.
• AC 33.28-3, Guidance Material for 14 CFR § 33.28, Engine Control Systems.
• AC 35.23-1, Guidance Material for 14 CFR 35.23, Propeller Control Systems.
4.3 EASA Acceptable Means of Compliance (AMC) AMC 20-152, Development Assurance for Airborne Electronic Hardware.
4.4 Industry Documents
• SAE International Aerospace Recommended Practice (ARP) 4754A, Guidelines for Development of Civil Aircraft and Systems, dated December 21, 2010.
SAE International Aerospace R ecommended Practice (ARP) 4761, Guidelines and Methods for Conducting the Safety Assessment Process on Civil Airborne Systems and Equipment, dated December 1996.
EUROCAE ED-79A, Guidelines for Development of Civil Aircraft and Systems, dated December 1, 2010.
RTCA DO- 254, Design Assurance Guidance for Airborne Electronic Hardware, dated April 19, 2000.
EUROCAE ED-80, Design Assurance Guidance for Airborne Electronic Hardware, dated April 1, 2000.
5 WHERE TO FIND THIS AC.
You may find this AC at http://www.faa.gov/regulations_policies/advisory_circulars/ If you have suggestions for improving this AC, you may use the Advisory Circular Feedback form at the end of this AC.
Digitally signed by
VICTOR W WICKLUND Date: 2022.10.07 14:12:13 -07'00' Victor Wicklund Acting Director, Policy and Innovation Division Aircraft Certification Service 16
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Appendix A A -1 APPENDIX A. GLOSSARY This glossary complements the terms defined in AC 20-152A with terms used only in this AC
00-72.
Uprating – A process to assess the capability of a COTS device to meet the performance requirements of the application in which the device is used outside the manufacturer's datasheet ranges (definition adapted from the IEC/TR 62240-1 thermal uprating definition.)
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