After too many pops of the primer, excess fuel collects in the intake manifold. When you turn the ignition and supply the spark, that excess fuel can ignite. Engine backfires, flames travel down the intake manifold Excess fuel from over-priming pools in intake manifold and air intake. ...then turn off the fuel selector, ignition, and master. Get out of the airplane immediately. Use the fire extinguisher to extinguish any blaze, if necessary. The airplane will need to be inspected before it can fly again. FLIGHT TRAINING NOVEMBER/DECEMBER 2021 31