The N2 displays on a gray background during the start until ________.

The N2 displays on a gray background during the start until ________.

• A. N2 reaches 100%
• B. The engine is stable
• C. Bleed air is supplied
• D. Engine reaches idle

Answer: (B)

The N2 indicator uses a gray background to show that the engine start is in progress. N2 represents the high-pressure spool speed, and during the start sequence it climbs from zero toward idle while the engine is stabilizing. The display stays with that gray background until the engine becomes stable—that is, N2 rises smoothly and settles within normal limits with the engine parameters consistent for normal operation. Once stability is achieved, the indication returns to the normal background so you can monitor the engine normally. Bleed air, reaching 100% N2, or idle timing aren’t the trigger for this change; the switch from gray to normal operation is driven by engine stability.

The N2 indicator uses a gray background to show that the engine start is in progress. N2 represents the high-pressure spool speed, and during the start sequence it climbs from zero toward idle while the engine is stabilizing. The display stays with that gray background until the engine becomes stable—that is, N2 rises smoothly and settles within normal limits with the engine parameters consistent for normal operation. Once stability is achieved, the indication returns to the normal background so you can monitor the engine normally. Bleed air, reaching 100% N2, or idle timing aren’t the trigger for this change; the switch from gray to normal operation is driven by engine stability.