I read a book about this but it was a very long time ago and I can't find the book anymore... I only remember that it has a WW2 pilot said something like, "When the Musashi/Yamato fired, the shockwave was strong enough to make my whole plane rattle and I can feel that my wings are ready to fold at any moment."
Was the 18" blast shockwaves that powerful or does it have the same shockwave as 16" guns on the Iowa classes?
Yamato's Type 94 18.1" guns used 360 kg of gunpowder to fire a 1460 kg shell at 780 meters per second.
Iowa's Mark 7 16" guns used 300 kg of gunpowder to fire a 1,225 kg shell at 762 meters per second.
So Yamato's guns were about 20 percent more powerful than Iowa's.
Still, to me it seems unlikely that it would rattle a plane unless the plane was very close, although perhaps that is possible after dropping a bomb or torpedo.