The JT15D-5 engine starting limit when ITT is 550 to 600 degrees C is a maximum of:

The JT15D-5 engine starting limit when ITT is 550 to 600 degrees C is a maximum of:

• A. 2 seconds
• B. 4 seconds
• C. 6 seconds
• D. 8 seconds

Answer: (B)

During starting, ITT is the key parameter that limits how long you can crank. When ITT is in the 550–600 C range, the allowable cranking duration is four seconds. This keeps heat in check and prevents overloading the turbine and starter components as they come up to light-off. If the engine hasn’t started within that four-second window, you abort and follow the cooldown/restart procedure. Four seconds is long enough to achieve a reliable light-off at that ITT level, but short enough to avoid pushing temperatures higher or overworking the starter. A shorter duration, like two seconds, risks an unsuccessful start, while longer durations such as six or eight seconds could drive ITT past safe limits and increase the chance of damage to the turbine or starter.

During starting, ITT is the key parameter that limits how long you can crank. When ITT is in the 550–600 C range, the allowable cranking duration is four seconds. This keeps heat in check and prevents overloading the turbine and starter components as they come up to light-off. If the engine hasn’t started within that four-second window, you abort and follow the cooldown/restart procedure.

Four seconds is long enough to achieve a reliable light-off at that ITT level, but short enough to avoid pushing temperatures higher or overworking the starter. A shorter duration, like two seconds, risks an unsuccessful start, while longer durations such as six or eight seconds could drive ITT past safe limits and increase the chance of damage to the turbine or starter.