FAA Order 8110.105

FAA Order 8110.105A, Simple and Complex Electronic Hardware Approval Guidance, supplements RTCA DO-254() by explaining how FAA aircraft certification staff can use that document "when working on certification projects" and is recommended as a reference for developers applying for certification under DO-254(). A particular focus is on clarification of the application of DO-254 guidance to "simple" custom micro-coded components (for example, ASICs, PLDs, or FPGAs with simple firmware functions installed) as opposed to the more rigorous assurance expected of complex custom micro-coded components. Micro-coded devices are typically presumed to be complex components that cannot be verified through testing alone; however, some applicants have proposed their specific micro-coded device applications as simple components.

Simple and Complex Electronic Hardware Approval Guidance
FAA Publication
AbbreviationFAA Order 8110.105
Year started2008[1]
Latest versionA
2017 (2017)
OrganizationFederal Aviation Administration
DomainAvionics, type certification
Websitefaa.gov

Additionally, Order 8110.105 addresses some of the omissions and clarification needs identified by the Certification Authorities Software Team in their position paper, CAST-31, and as such informs hardware developers of interests beyond those presently expressed in DO-254.[1]

Functioning hardware systems and products certified through DO-254() processes range from replaceable electronic boxes, circuit boards within such enclosures, and ASICs, PLDs, or FPGAs placed on such boards. These sorts of hardware can be classified as simple or complex.[2] With respect to DO-254(), a device is classified as simple if comprehensive inspection or testing alone can demonstrate that it is reasonably free of design defects or errors and has deterministic behavior. A complex device, then, is one that cannot be assessed by comprehensive inspection or testing alone.[3][4][5]

For the purposes of aircraft type certification efforts, aircraft system components are designated as software or hardware. Software components are computer programs installed and operating on computers or microcontrollers and are usually subjected to the design assurance processes of RTCA DO-178() when installed in aircraft. DO-254() is applied to the certification of both simple and complex hardware components, particularly inclusive of both simple and complex custom micro-coded components. "A hardware item is considered simple if a comprehensive combination of deterministic tests and analyses can ensure correct functional performance under all foreseeable operating conditions with no anomalous behavior." All other hardware items are considered complex and, since complex hardware items cannot be completely validated by inspection and testing alone, design assurance methodology is required.[6] Advisory Circular 20-152 recognizes the guidance in DO-254 as a suitable means for demonstrating compliance for the use of complex custom micro-coded components within aircraft systems.[7] However, application of DO-254 to simple micro-coded components was not explicitly addressed by that circular.[8]

Initially, applicants and developers were concerned with the apparent ambiguity of DO-254's guidance on simple electronic hardware. That document is largely concerned with the objectives and activities of developing complex electronic hardware. However, it provides only one short paragraph suggesting that a simple hardware item should be configuration controlled and verified, but "extensive documentation is not needed". In response to the concern, CAST-30 Simple Electronic Hardware and RTCA Document DO-254 and EUROCAE Document ED-80 was completed in 2007 to provide clarification to the guidance in DO-254/ED-80 specifically for simple electronic hardware.[9][10] Following this, FAA Order 8110.105 was released in 2008 to supplement the guidance for both simple and complex electronic hardware,[1] and revised to Revision A in 2017. Three primary chapters are clarification of

  • topics applicable to both simple and complex electronic hardware,
  • topics applicable to complex electronic hardware alone, and
  • topics applicable to simple electronic hardware alone.[11][12]

References
  1. Cary Spitzer; Uma Ferrell; Thomas Ferrell, eds. (2015). Digital Avionics Handbook, Avionics, Development and Implementation (3rd ed.). Boca Raton, FL: CRC Press. p. 14-17 to 14-18. ISBN 978-1138076983. The FAA published Order 8110.105 originally in 2008. ... The Order explains FAA interpretation and application of DO-254 to simple and complex electronic approval. [emphasis added]
  2. Digital Avionics Handbook, Avionics. p. 14-1. The hardware items encompass line-replaceable units (LRUs), circuit card assemblies, and custom microcoded devices such as fieldprogrammable gate arrays (FPGAs) and ...
  3. Digital Avionics Handbook, p. 14-2, Hardware that is fully testable, through comprehensive and deterministic verification tests that address all foreseeable operating conditions, is classified as simple. The verification of simple hardware needs to demonstrate that the hardware has deterministic behavior and is free of anomalies.
  4. Acquisition Management : A Guide for Program Management. Systems Command, United States. 1976. Retrieved 2022-06-16. Complex equipments and subsystems cannot be evaluated by inspection and testing alone. [emphasis added]
  5. Challenges and Approaches for Selecting, Assessing and Qualifying Commercial Industrial Digital Instrumentation and Control Equipment for Use in Nuclear Power Plant Applications. IAEA. 2020. ISBN 9789201100207. Retrieved 2022-06-16. This is particularly important for ... complex hardware (such as FPGAs), where inspection or testing alone cannot confirm the behavior of the device. [emphasis added]
  6. RTCA/DO-254 "Design Assurance Guidance For Airborne Electronic Hardware", Appendix C
  7. AC 20-152, FAA, Office AIR-100, 2005. "This AC recognizes the guidance in RTCA/DO-254 applies specifically to complex custom micro-coded components with hardware design assurance levels of A, B, and C, such as ASICs, PLDs, and FPGAs", Page 1.
  8. "8110.105 Simple And Complex Electronic Hardware Approval Guidance" (PDF). FAA Order. FAA: 1–2. 2008-07-13. Retrieved 2019-09-04. "[AC 20-152] doesn't recognize RTCA/DO-254 as a way to demonstrate compliance to regulations for simple micro-coded components.
  9. "CAST-30 Simple Electronic Hardware and RTCA Document DO-254 and EUROCAE Document ED-80, Design Assurance Guidance for Airborne Electronic Hardware" (PDF). Position Paper. FAA: 1. Retrieved 2019-09-04. This CAST paper provides clarification to the guidance in RTCA document DO-254 and EUROCAE document ED-80 for simple electronic hardware, ...
  10. Digital Avionics Handbook, pp. 14–18 CAST-30 is listed as relevant to 8110.105
  11. "8110.105 Simple And Complex Electronic Hardware Approval Guidance" (PDF). FAA Order. FAA. 2008-07-13. Retrieved 2019-09-04.
  12. Digital Avionics Handbook, pp. 14–18 The table list these three subjects.
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