What should be done if a start attempt is interrupted with fuel introduced and no light off at N2 >= 20%?

The correct response in this situation is to proceed with dry motoring. When a start attempt is interrupted after fuel introduction and there is no light off once N2 reaches 20%, it indicates that the engine has not ignited the fuel that was introduced. Continuing with dry motoring is a critical step because it helps to clear any unburned fuel from the combustion chamber, thereby reducing the risk of a fire during a subsequent start attempt.

Additionally, dry motoring allows the starter to continue cranking the engine without introducing more fuel, which is essential in preventing a build-up of flammable material that could result in a hazardous situation. This procedure is part of standard operating practices in managing engine start attempts and ensures safety while maintaining the integrity of the engine components.

The other options do not appropriately address the situation. Attempting another start immediately without the dry motoring could lead to unsafe conditions, while waiting for 10 minutes without addressing the stagnant fuel could also exacerbate the problem. Notifying maintenance, while a prudent step later, is not immediately relevant to managing the immediate engine start interruption situation.