Ground start of engine groups 3 through 5 has what crank limit?

Ground start of engine groups 3 through 5 has what crank limit?

• A. 90 sec ON / 5 min OFF
• B. 120 sec ON / 5 min OFF
• C. 90 sec ON / 10 sec OFF
• D. 120 sec ON / 10 sec OFF

Answer: (A)

The test is about the starter duty cycle for ground starts. There is a maximum time you can keep the starter engaged in a single attempt, followed by a required cooldown to protect the starter and electrical system from overheating. For ground starts of engine groups 3 through 5, you may crank up to 90 seconds in one continuous attempt, then you must wait 5 minutes before attempting another start. This limit helps prevent starter motor overheating and wear, and ensures the electrical system isn’t overstressed during the start sequence. If the engine doesn’t start within that 90-second window, you should stop and allow the cooldown period before trying again. Longer cranking or shorter cooldowns would increase the risk of damage to the starter and related components, which is why the 90 seconds on, 5 minutes off option is the correct limit.

The test is about the starter duty cycle for ground starts. There is a maximum time you can keep the starter engaged in a single attempt, followed by a required cooldown to protect the starter and electrical system from overheating.

For ground starts of engine groups 3 through 5, you may crank up to 90 seconds in one continuous attempt, then you must wait 5 minutes before attempting another start. This limit helps prevent starter motor overheating and wear, and ensures the electrical system isn’t overstressed during the start sequence. If the engine doesn’t start within that 90-second window, you should stop and allow the cooldown period before trying again.

Longer cranking or shorter cooldowns would increase the risk of damage to the starter and related components, which is why the 90 seconds on, 5 minutes off option is the correct limit.