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1) in the case of aircraft, the modification involves increase in the seating capacity, installation of floats or skids, conversion from passenger to freighter version, fuselage stretch, increase in design mass of more than 10 per cent, primary structure change from metallic to composite material, certification for flights into known icing conditions, or comprehensive flight deck upgrades;
2) in the case of an aircraft engine, the modification involves use of new design fan blade and fan hub in a turbine engine, change in the containment case material, conversion from mechanical to electrical control systems, addition of a turbocharger, or conversion from spark-ignition to compression-ignition for piston engines; or
3) in the case of propellers, the modification involves introduction of a different principle of blade retention.
c) Not Significant Change. A design change whose effect on the product does not rise to the level of neither a substantial nor significant change. A Not Significant change remains a major modification, and should not be confused as equivalent to, or treated like, a minor change (see 5.3.3, Minor Modification Category). The effect of a Not Significant change is usually confined to a single area, system, or component of an aircraft, engine or propeller. Some examples of modifications that are generally regarded as Not Significant changes are:
1) in the case of aircraft, the modification involves general avionics upgrade, relocation of galley, installation of non-essential auxiliary power unit, substitution of one structural bonding method for another, installation of wheel skis, installation of quieter exhaust system, increase in fuel tank capacity, installation of new type passenger seats, or mass increase of less than 5 per cent;
2) in the case of an aircraft engine, the modification involves change in oil tank design, fan blade re-design, software changes, bearing change, change in limits on exhaust gas temperature, change from one hydro-mechanical control to another hydro-mechanical control, change in crankshaft, or redesigned cylinder head, valves or pistons; or
3) in the case of propellers, the modification involves change in the material of the bearing or change to a component in the control system.
5.3.3 Minor modification category
By definition, a minor modification is a design change that has a negligible, or no appreciable, effect on the mass, balance, structural strength, reliability, operational characteristics, or other characteristics affecting the airworthiness of the product. The accomplishment of minor modifications normally involves use of standard or generally accepted practices.
5.3.4 Emissions change category
The type certification of an aircraft and engine include compliance with, and certification to, the environmental standards of Annex 16, Environmental Protection. The demonstrated levels of noise and exhaust smoke and gaseous emissions for which an aircraft and/or engine were approved for purposes of issuance of a Type Certificate are those recorded in the Type Certificate Data Sheet. The intent of Annex 16 is to ensure that these recorded levels are maintained, or improved, throughout the operational life of the aircraft or engine. Where a modification is not intended to change the approved emissions limit of an aircraft or engine, an environmental assessment may be conducted, at the discretion of the CAA, to verify the unintended consequential changes to the approved emissions limit of the aircraft or engine. However, if the proposed modification is specifically directed at changing or improving the current emissions level of an aircraft or engine (such as retrofit of hush kits or re-engine programme), a re-certification is necessary to establish compliance with the applicable requirements. As part of an assessment of a modification as either major or minor, the proposed modification to emission levels should also be categorized as one or more of the following:
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适航手册 AIRWORTHINESS MANUAL(94)
