When using external power, what is the maximum duration for engine start?

• A. 20 seconds on, 30 seconds off
• B. 25 seconds on, 30 seconds off
• C. 30 seconds on, 30 seconds off
• D. 25 seconds on, 30 minutes off

Answer: (B)

The correct answer specifies that the maximum duration for engine start while using external power is 25 seconds on, followed by a recovery period of 30 seconds off. This restriction is in place to prevent overheating and ensure the longevity of the engine start system.

When an aircraft engine is started with external power, the initial engagement of the starter requires a significant amount of electrical power. Limiting the engagement duration to 25 seconds helps manage the thermal and electrical load placed on both the engine and the external power source. The 30 seconds off period allows for adequate cooling and recovery, preventing damage or reduced performance in future starts. By adhering to these specified intervals, operators can maintain the integrity and reliability of the aircraft's start system.

Understanding these intervals is crucial for maintaining safe and effective operations during engine starts, especially in situations where external power is being utilized.