During windmill airstart, what is the minimum airspeed and N2 requirement?

• A. 250 Knots - Vmo and 7.2% N2 minimum
• B. 200 Knots - Vmo and 5% N2
• C. 300 Knots - Vmo and 8% N2
• D. 150 Knots - N2 2%

Answer: (A)

During a windmill airstart you rely on ram air to spin the engine’s high-pressure spool. For the start to be reliable, you need enough airflow to bring N2 up to a level where fuel can be introduced and ignition can be sustained. The required minimum is 250 knots indicated airspeed, while staying within the engine’s Vmo envelope, and the N2 must reach at least 7.2% before you proceed with the start. If the airspeed is too low, the compressor won’t windmill fast enough; if N2 doesn’t reach the ~7.2% threshold, ignition won’t occur reliably. The other options either propose speeds that don’t provide adequate ram air or specify N2 values that won’t guarantee a stable windmill start, so they’re not appropriate.