I was wondering that; what if the Su27 pilot went to 'burner but for some reason the 'burner either failed to ignite or there was a delay before it ignited pumping excess fuel out of the exhaust.
I've seen it happen when watching a jet dragster so it can happen.
Except that jet dragsters don't actually have afterburners. I believe it is illegal in the U.S. for a private citizen to own one and they are removed by the military when equipment is sold. All the jet cars do is dump a bunch of extra fuel into the exhaust stream for visual effect.