Which N2 range is associated with MOTORING on the N2 gauge?

Which N2 range is associated with MOTORING on the N2 gauge?

• A. Between 10% and 20% N2
• B. Between 18% and 24% N2
• C. Between 25% and 35% N2
• D. Between 5% and 15% N2

Answer: (B)

During engine start, the starter turns the engine to build up the high-pressure spool speed without burning fuel. This is what “MOTORING” on the N2 gauge indicates—the engine is being driven by the starter to reach a speed where ignition can occur, but no combustion is taking place yet. The best match is the range around 18–24% N2. It sits in the middle of the motoring window: high enough that the starter can turn the compressor smoothly, but not so high that fuel is being injected and the engine is about to light off. Other options fall outside this typical motoring band—lower ranges are too close to pre-start or stalled conditions, and higher ranges (like 25–35% N2) are associated with approaching or achieving light-off and normal start progression. So 18–24% N2 is the designated motoring range on the N2 gauge.

During engine start, the starter turns the engine to build up the high-pressure spool speed without burning fuel. This is what “MOTORING” on the N2 gauge indicates—the engine is being driven by the starter to reach a speed where ignition can occur, but no combustion is taking place yet.

The best match is the range around 18–24% N2. It sits in the middle of the motoring window: high enough that the starter can turn the compressor smoothly, but not so high that fuel is being injected and the engine is about to light off. Other options fall outside this typical motoring band—lower ranges are too close to pre-start or stalled conditions, and higher ranges (like 25–35% N2) are associated with approaching or achieving light-off and normal start progression. So 18–24% N2 is the designated motoring range on the N2 gauge.