87.48 Derivative engines for emissions certification purposes.§ 87.48 Derivative engines for emissions certification purposes.
(a) General. A type certificate holder may request from the FAA a determination that an engine configuration is considered a derivative engine for emissions certification purposes. This would mean that the engine configuration is determined to be similar in design to a previously certificated engine (the “original” engine) for purposes of compliance with exhaust emission standards (gaseous and smoke). In order for the engine configuration to be considered a derivative engine for emission purposes under this part, it must have been derived from an original engine that was certificated to the requirements of 14 CFR part 33, and one of the following conditions must be met:
(1) The FAA determined that a safety issue exists that requires an engine modification.
(2) Emissions from the derivative engines are determined to be similar. In general, this means the emissions must meet the criteria specified in paragraph (b) of this section. FAA may adjust these criteria in unusual circumstances, consistent with good engineering judgment.
(3) All of the regulated emissions from the derivative engine are lower than the original engine.
(b) Emissions similarity. (1) The type certificate holder must demonstrate that the proposed derivative engine model's emissions meet the applicable standards and differ from the original model's emission rates only within the following ranges:
(i) ±3.0 g/kN for NOX.
(ii) ±1.0 g/kN for HC.
(iii) ±5.0 g/kN for CO.
(iv) ±2.0 SN for smoke.
(2) If the characteristic level of the original certificated engine model (or any other sub-models within the emission type certificate family tested for certification) before modification is at or above 95% of the applicable standard for any pollutant, you must measure the proposed derivative engine model's emissions for all pollutants to demonstrate that the derivative engine's resulting characteristic levels will not exceed the applicable emission standards. If the characteristic levels of the originally certificated engine model (and all other sub-models within the emission type certificate family tested for certification) are below 95% of the applicable standard for each pollutant, then, you may use engineering analysis to demonstrate that the derivative engine will not exceed the applicable emission standards, consistent with good engineering judgment. The engineering analysis must address all modifications from the original engine, including those approved for previous derivative engines.
(c) Continued production allowance. Where we allow continued production of an engine model after new standards begin to apply, you may also produce engine derivatives if they conform to the specifications of this section.
(d) Non-derivative engines. If the FAA determines that an engine model does not meet the requirements for a derivative engine for emissions certification purposes, the type certificate holder is required to demonstrate that the engine complies with the emissions standards applicable to a new engine type.