Complex sentence: As the engine separated it flew through the air on its own, crackling and sputtering loudly as it burned off the last of its fuel before landing in a gas station next to the gas pumps.
Split into simpler sentences: As the engine separated it flew through the air on its own. As it did so, it crackled and sputtered loudly as it burnt off the last of its fuel before landing in a gas station next to the gas pumps.