Which term describes ignition that does not require a pilot to ignite the fuel-air mixture?

• A. Piloted ignition
• B. Auto ignition
• C. Spontaneous ignition
• D. Thermal ignition

Answer: (B)

Ignition without a pilot happens when the fuel–air mixture burns because enough heat is present to start the reaction on its own. This is known as auto ignition. It occurs when the mixture reaches its ignition temperature or when heat from compression or a hot surface provides the energy to start burning, without any external flame or spark.

A piloted ignition would need a flame or spark to start the burn, so it doesn’t fit. Spontaneous ignition refers to self-heating within a material that can lead to ignition without an external heat source, which is a different scenario. Thermal ignition is a broader term related to heat-caused ignition, but auto ignition is the precise term used for ignition of a fuel–air mixture without a pilot.