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In aviation, a hot start is an adverse effect of a reaction engine being improperly started. In a jet engine - be it a pure jet, a turbofan or a turboprop - a great amount of the air ingested by the engine runs around the combustion chamber or around its flame, instead of being mixed with fuel and burned. The purpose of this air is to keep the temperature of the chamber within its limits. If it weren't for this cooling effect, the chamber would get too hot because of the combustion, and it would then be burned or even melted. In a turbofan, the engine is started when compressed air is blown through its high-pressure stages. In a turboprop, the engine is started by the starter-generator, which is the engine's own electric generator - during the start, an electric current runs through it, making it spin, and then making the whole engine turn. In both cases, the engine must be already spinning before igniting the fuel, so as to have the compressors attain enough speed to draw air and make it flow though the engine. When there is a sufficient amount of air flowing, the fuel is injected, and then the engine will be able to run by itself. The critical part is injecting the fuel. If the fuel is ignited before there is enough air flowing around the chamber, its temperature will increase dramatically and exceed the design limits of the combustion chamber and turbine blades, thus causing a failure. This condition is known as a hot start.〔 〕 In some modern jet engines FADEC system prevents such condition from occurring. When FADEC is not present the flight crew has to monitor the engine parameters and manually shut off the fuel valve if the exhaust temperature exceeds its maximum allowed value. ==References== A hot start is aviation pilot slang referring to the condition during a turbine engine (turboprop, jet, turbofan, etc.) start in which the Turbine Inlet Temperature or Interstage Turbine Temperature exceeds the turbine manufacturer's prescribed starting limits. Hot starts damage the turbine engine usually by causing damage to the metal structure of the engine. A hot start may occur when fuel is introduced into the engine combustion chamber while the compressor RPM of the turbine engine is too low. When fuel is introduced without adequate air pressure from the compressor section of the turbine engine, fuel will burn in combustion chamber without adequate outflow to the turbine section of the engine, thus creating an extremely hot temperature in the combustion chamber. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Hot start」の詳細全文を読む スポンサード リンク
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