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

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

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

Answer: (A)

Crank limits define how long you can energize the starter during a start and how long you must wait between attempts to protect the starter and electrical system from overheating. For flight starts of engine groups 3 through 5, the permissible continuous cranking is 120 seconds, followed by a minimum 5-minute cooling period before attempting another start. This 120 seconds on, 5 minutes off duty cycle ensures the engine can spool and ignite properly while giving the starter a safe cooldown time. Shorter on-times or shorter off-times (like 90 seconds or 10 seconds) don’t provide the necessary cooling and could overheat the starter or components, so they aren’t used in this scenario.

Crank limits define how long you can energize the starter during a start and how long you must wait between attempts to protect the starter and electrical system from overheating. For flight starts of engine groups 3 through 5, the permissible continuous cranking is 120 seconds, followed by a minimum 5-minute cooling period before attempting another start. This 120 seconds on, 5 minutes off duty cycle ensures the engine can spool and ignite properly while giving the starter a safe cooldown time. Shorter on-times or shorter off-times (like 90 seconds or 10 seconds) don’t provide the necessary cooling and could overheat the starter or components, so they aren’t used in this scenario.