Which start condition is most likely to cause engine damage?

Which start condition is most likely to cause engine damage?

• A. Hot start
• B. Hung start
• C. Cold start
• D. Wet start

Answer: (A)

Starting an engine when it is already hot puts the engine under extreme thermal stress during the initial combustion. The combustion chamber, valves, piston crowns, and turbine surfaces are already near their temperature limits from prior operation. Introducing fuel for a start when those parts are hot can cause combustion to run hotter than the design allows, leading to overheating, pre-ignition or detonation, and accelerated wear or damage to heat-stressed components. In turbine engines, this shows up as a rapid rise in exhaust gas temperature and the potential for thermal fatigue or blade damage if limits are exceeded. Because the heat is already in the system, a hot start makes damage more likely than the other start conditions. Cold starts, hung starts, or wet starts involve different risks and generally don’t push temperatures as quickly or severely toward those damaging levels.

Starting an engine when it is already hot puts the engine under extreme thermal stress during the initial combustion. The combustion chamber, valves, piston crowns, and turbine surfaces are already near their temperature limits from prior operation. Introducing fuel for a start when those parts are hot can cause combustion to run hotter than the design allows, leading to overheating, pre-ignition or detonation, and accelerated wear or damage to heat-stressed components. In turbine engines, this shows up as a rapid rise in exhaust gas temperature and the potential for thermal fatigue or blade damage if limits are exceeded. Because the heat is already in the system, a hot start makes damage more likely than the other start conditions. Cold starts, hung starts, or wet starts involve different risks and generally don’t push temperatures as quickly or severely toward those damaging levels.