Turbine Engine Start Abort and Hot Start Recognition
A turbofan engine is being started on the ground at an ambient temperature of 38°C. The start sequence begins normally, with N2 rising and fuel flow indicating 450 lb/hr after fuel is introduced. Within 8 seconds, the exhaust gas temperature rises rapidly past the normal start limit of 750°C and reaches 820°C, while N2 stagnates at 22% and does not increase. The starter is still engaged, and the ignition is on. The crew has a 20-minute slot before the next departure and the aircraft has a full passenger load. The engine has a known history of slow starts in hot weather.
1. Identify the condition and justify the immediate action.
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The rapid EGT rise with stagnating N2 after fuel introduction is a hot start. Fuel is burning but the compressor is not accelerating, so the combustion energy is heating the turbine rather than producing thrust. The EGT has already exceeded the start limit, so the crew must abort the start immediately by closing the fuel shutoff valve and continuing to motor the engine with the starter to purge unburned fuel and cool the turbine. Continuing the start would risk turbine blade damage and possibly a tailpipe fire. The hot ambient temperature and the engine's history of slow starts increase the likelihood of a hot start, so the crew should not treat this as a normal slow start. The decision to abort is not optional once the EGT limit is exceeded; the judgement is in how quickly the crew recognises the trend and acts.
2. Describe the post-abort actions and the criteria for attempting a second start.
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After aborting, the crew should keep the starter engaged to motor the engine until the EGT falls below the limit and stabilises, then complete the shutdown checklist and record the peak EGT. Maintenance should be consulted because an exceedance may require an inspection. A second start attempt is acceptable only if the EGT has cooled, the cause of the slow acceleration is understood, and the crew uses a procedure suited to hot conditions, such as a higher starter-assisted motoring period before fuel introduction. If the second attempt shows the same EGT trend, the crew should not try a third time and should consider a different aircraft or a delay. The judgement call is to balance the schedule pressure against the risk of an undetected turbine exceedance, and the conservative choice is to delay rather than press on.