G/GS 5.6A Operationwc_tx000152gb.fm 174.6 Generator DeratingAll generators are subject to derating for altitude and temperature.Internal combustion engines, unless modified, run less efficiently athigher altitudes due to the reduction of air pressure. This translatesinto a lack of power and thus reduction in generator output.Temperature affects both engine and generator performance. Astemperature increases, an engine will run less efficiently and moreresistance will be found in electrical components. Therefore, as thetemperature increases, the output of the generator decreases. Altitudealso affects the cooling capacity of air—the higher the altitude the lessdense the air is and thus the lower its ability to transfer heat.For every increase in altitude of 500 m (1650 ft.) above 1000 m (3300ft.), the output of the generator will be reduced by 3%. For everyincrease of 5° C (9° F) in ambient temperature above 40° C (104° F),the output of the generator will be reduced by 3%. Use the tablesshown for altitude and temperature deration factors. It may benecessary to consider both altitude and ambient temperature derationfactors to determine true generator output.Ambient Temp.°C (°F) Derate Factor45 (113) 3 % 0.9750 (122) 6 % 0.9455 (131) 9 % 0.9160 (140) 12 % 0.88Altitudem (ft.) Derate Factor1500 (4900) 3 % 0.972000 (6600) 6 % 0.942500 (8200) 9 % 0.913000 (9900) 12 % 0.883500 (11500) 15 % 0.854000 (13100) 18 % 0.82