Appendix 1 to AMC 20-136A -- Definitions and acronyms

• ED Decision 2022/001/R found in: AMC-20 Amdt 23 - Airworthiness of Products, Parts and Appliances (Jan 2022)

Appendix 1 to AMC 20-136A — Definitions and acronyms ED Decision 2022/001/R a.         Definitions **Adverse effect:** a response of a system that results in an unexpected and unacceptable operation of an aircraft system, or unexpected and unacceptable operation of the function performed by the system. **Actual transient level (ATL):** the level of transient voltage or transient current that appears at the equipment interface circuits because of the external environment. This level may be less than or equal to the transient control level but should not be greater. **Aperture:** an electromagnetically transparent opening. **Attachment point:** a point where the lightning flash contacts the aircraft. **Automatically recover:**return to normal operations without pilot action. **Channel:**a subset of a system consisting of equipment, components, elements and electrical interconnections,which performs an aircraft function provided by the system. A system could be composed of redundant similar or dissimilar channels in order to maintain the function at aircraft level in case of failure on one or several channels. **Component damage:** a condition in which transients permanently alter the electrical characteristics of a circuit. Because of this, the component can no longer perform to its specifications. **Continued safe flight and landing:** thecapability for continued controlled flight and landing at a suitable location, possibly using emergency procedures, but without requiring exceptional piloting skill or strength. For CS-25 aeroplanes, the pilot must be able to land safely at a suitable airport. For CS-23 aeroplanes, it is not necessary to land at an airport. For rotorcraft, the rotorcraft must continue to cope with adverse operating conditions, and the pilot must be able to land safely at a suitable site. Some aircraft damage may be associated with a failure condition during flight or upon landing. **Direct effects:** physical damage to the aircraft or to its electrical and electronic systems. Direct attachment of lightning to the system’s hardware or components causes the damage. Examples of direct effects include tearing, bending, burning, vaporisation, or blasting of aircraft surfaces and structures, and damage to the electrical and electronic systems. **Electrical and electronic system:** an electrical or electronic system includes all electrical and electronic equipment, components, elements, and the electrical interconnections that are required to perform a particular function. **Equipment:** a component of an electrical or electronic system with interconnecting electrical conductors. **Equipment electrical interface:** a location on a piece of equipment where an electrical connection is made to the other equipment in a system of which it is a part. The electrical interface may consist of individual wires or wire bundles that connect the equipment. **Equipment transient design level (ETDL):** the peak amplitude of transients to which equipment is qualified. **Function:**the specific action of a system, equipment, and flight crewperformance aboard the aircraft that, by itself, provides a completely recognisable operational capability. For example, ‘display aircraft heading to the pilots’ is a function. One or more systems may perform a specific function, or one system may perform multiple functions. **External environment:** the natural lightning environment, outside the aircraft, for design and certification purposes. See SAE ARP 5412B/EUROCAE ED-84A, which references documents that provide additional guidance on aircraft lightning environments and the related waveforms. **Immunity:** thecapacity of a system or piece of equipment to continue to perform its intended function, in an acceptable manner, in the presence of RF fields. **Indirect effects:** electrical transients induced by lightning in aircraft electrical or electronic circuits. **Internal environment:** the electric and magnetic fields, currents, and voltages on and within the aircraft produced by a lightning strike to the aircraft. **Lightning flash:** the total lightning event. It may occur in a cloud, between clouds, or between a cloud and the ground. It can consist of one or more return strokes, plus intermediate or continuing currents. **Lightning strike:** attachment of the lightning flash to the aircraft. **Lightning strike zones:** aircraft surface areas and structures that are susceptible to lightning attachment, dwell times, and current conduction. See SAE ARP 5414B/EUROCAE ED-91A, which references documents that provide additional guidance on aircraft lightning zoning. **Lightning stroke (return stroke):** a lightning current surge that occurs when the lightning leader (the initial current charge) makes contact with the ground or another charge centre. A charge centre is an area of high potential of opposite charge. **Margin:** the difference between the equipment transient design levels and the actual transient level. **Multiple burst:** a randomly spaced series of bursts of short duration, low-amplitude current pulses, with each pulse characterised by rapidly changing currents. These bursts may result as the lightning leader progresses or branches, and are associated with the cloud-to-cloud and intra-cloud flashes. The multiple bursts appear most intense when the initial leader attaches to the aircraft. See SAE ARP 5412B/EUROCAE ED-84A. **Multiple stroke:** two or more lightning return strokes during a single lightning flash. SeeSAE ARP 5412B/EUROCAE ED-84A. **Non-normal situation:**any situation that requires non-normal, abnormal, emergency, or unusual procedures, or configurations for operating an aircraft. **Normal operation:** a status where the system is performing its intended function. When addressing compliance with CS23.1306/2515(a)(2), 25.1316(a)(2), 27.1316(a)(2), and 29.1316(a)(2), the function whose failure would prevent the continued safe flight and landing should be in the same undisturbed state as before exposure to the lightning threat while other functions, performed by the same system, subject to CS23.1306/2515(b), 25.1316(b), 27.1316(b), and 29.1316(b), are not required to be recovered. The system that performs the function may be nevertheless in a different state as long as the function is not adversely affected. **Timely manner:** timely recovery has been introduced to account for the necessary period for complex systems to reconfigure safely after a disruption. The meaning of ‘in a timely manner’ depends upon the function performed by the system to be evaluated, the specific system design, interaction between that system and other systems, and interaction between the system and the flight crew, or the phase of flight, which must be considered in the safety assessment. Therefore, the definition of ‘in a timely manner’ must be determined for each specific function performed by the system. The applicable definition could be included in the lightning compliance plan for review and concurred with the Agency. **Transient control level (TCL):** the maximum allowable level of transients that appear at the equipment interface circuits because of the defined external environment. **Upset:** impairment, either permanent or momentary, of the system’s operation. For example, a change of digital or analogue state that may or may not require a manual reset. b.         Acronyms <table border="0" cellpadding="0" cellspacing="0"> <tr> <td valign="top"> <p>14 CFR:</p> </td> <td valign="top"> <p>Title 14 of the Code of Federal Regulations</p> </td> </tr> <tr> <td valign="top"> <p>AC:</p> </td> <td valign="top"> <p>advisory circular</p> </td> </tr> <tr> <td valign="top"> <p>AMC:</p> </td> <td valign="top"> <p>acceptable means of compliance</p> </td> </tr> <tr> <td valign="top"> <p>ARP:</p> </td> <td valign="top"> <p>aerospace recommended practice </p> </td> </tr> <tr> <td valign="top"> <p>ATL:</p> </td> <td valign="top"> <p>actual transient level</p> </td> </tr> <tr> <td valign="top"> <p>CS:</p> </td> <td valign="top"> <p>certification specification</p> </td> </tr> <tr> <td valign="top"> <p>DAL:</p> </td> <td valign="top"> <p>development assurance level (ED-79A/ARP4754A) / <br/> design assurance level (ED‑80/DO-254, ED-12C / DO-178C) </p> </td> </tr> <tr> <td valign="top"> <p>DEL:</p> </td> <td valign="top"> <p>direct effect of lightning</p> </td> </tr> <tr> <td valign="top"> <p>ETDL:</p> </td> <td valign="top"> <p>equipment transient design level</p> </td> </tr> <tr> <td valign="top"> <p>EASA:</p> </td> <td valign="top"> <p>European Union Aviation Safety Agency</p> </td> </tr> <tr> <td valign="top"> <p>EUROCAE:</p> </td> <td valign="top"> <p>European Organisation for Civil Aviation Equipment</p> </td> </tr> <tr> <td valign="top"> <p>FAA:</p> </td> <td valign="top"> <p>Federal Aviation Administration</p> </td> </tr> <tr> <td valign="top"> <p>ICAs:</p> </td> <td valign="top"> <p>instructions for continued airworthiness</p> </td> </tr> <tr> <td valign="top"> <p>IEL:</p> </td> <td valign="top"> <p>indirect effect of lightning</p> </td> </tr> <tr> <td valign="top"> <p>TCL:</p> </td> <td valign="top"> <p>transient control level</p> </td> </tr> </table> [Amdt 20/23]