flaming onion

noun2

1. •
   (slang, historical) A 37 mm Hotchkiss revolving-barrel anti-aircraft gun used by the German army at the beginning of World War I.
2. •
   (slang, historical) The flare or tracer ammunition fired by this weapon.

   • Allied pilots feared and loathed these, because a hit from a flaming onion instantly turned an aeroplane into an inferno. — 1985