How does preignition differ from detonation?

Choices

• ✓ Preignition is ignition of the mixture before the spark plug fires, from a hot spotcorrect

  Preignition is early ignition off a hot spot such as a glowing deposit, before the plug fires.

• Preignition only happens on the ground during run-up

  Preignition is a combustion phenomenon in flight or on the ground, not limited to run-up.

• Preignition cools the engine below normal temperatures

  Preignition overheats the engine; it does not cool it.

• Preignition is the normal, smooth burning of the charge

  Normal combustion is a smooth even flame; preignition is abnormal.