Is JetA1 heavier then Avgas? Maybe topped it off and it all sunk to the bottom the tanks or something
There's a bloke over in the west who has first hand experience in just that very subject while he was conducting a mail run. He tried it in a C210 in around 2004 sometime in central Australia. His inattention when refuelling his aircraft very nearly cost him his life quite some distance and stops after he refuelled.
I am not saying that PGW had Jet A1 in its tanks in this instance but there seem to be similarities to the incident I speak of in some of the evidence arising from some witnesses to the way the remaining engine was delivering power.
Despite the difference in specific gravity it seems to float on the AVGAS with a layer that does mix to a certain extent, which seems to allow an aircraft to get airbourne with the inevitable power degradation (when the engine is trying to digest the cocktail of Avgas and Jet A1 it still runs, however belches smoke and runs very rough) sometime later.