Hot start in a gas turbine engine is defined as a start which occurs with normal engine rotation, but exhaust temperature exceeds prescribed limits. This is usually caused by what condition?

• A. A start which occurs with normal engine rotation, but exhaust temperature exceeds prescribed limits due to an excessively rich mixture.
• B. A start where engine rpm rapidly increases to idle.
• C. A start that occurs when exhaust temperature is below limits.
• D. A start with no fuel reaching combustor.

Answer: (A)

Hot start means the engine rotates normally during start, but the exhaust gas temperature is higher than allowed. The most common reason for this is an excessively rich fuel/air mixture during light-off. When too much fuel is metered for the available air, the flame temperature climbs and more heat ends up in the turbine and exhaust, pushing the EGT beyond limits. This situation is typically due to a fault in fuel metering or fuel scheduling during start. The other scenarios describe different conditions not associated with a hot start: a rapid rise to idle doesn’t by itself indicate overheating; an exhaust temperature below limits indicates a cold start; and no fuel reaching the combustor means ignition would not occur.