Which indication confirms BRM is active during start on the MAX?

Which indication confirms BRM is active during start on the MAX?

• A. MOTORING is displayed on the N2 gauge between 18% and 24% N2
• B. N2 gauge shows 0%
• C. FUEL FLOW warning
• D. APU DOOR light

Answer: (A)

During an APU start on the MAX, the BRM controls the initial phase where the starter motor spins the APU compressor before any ignition occurs. The best indication that BRM is active is when the N2 gauge shows the label “MOTORING” in the range around 18% to 24% N2. This tells you the APU is being driven by the starter and is not yet firing or producing bleed air; it’s in the pre-ignition motoring stage managed by BRM. If N2 were at 0%, there’d be no rotation at all, so BRM wouldn’t be indicating motoring. A fuel flow warning would appear only after ignition and fuel is being burned, not during motoring. The APU door light relates to the door position and isn’t a direct indicator of BRM activity.

During an APU start on the MAX, the BRM controls the initial phase where the starter motor spins the APU compressor before any ignition occurs. The best indication that BRM is active is when the N2 gauge shows the label “MOTORING” in the range around 18% to 24% N2. This tells you the APU is being driven by the starter and is not yet firing or producing bleed air; it’s in the pre-ignition motoring stage managed by BRM.

If N2 were at 0%, there’d be no rotation at all, so BRM wouldn’t be indicating motoring. A fuel flow warning would appear only after ignition and fuel is being burned, not during motoring. The APU door light relates to the door position and isn’t a direct indicator of BRM activity.