The Filter hatch folds like 120° to 130°.
The hatch with the air fans folds 180°, but you see some pics where that hatch is folded until the fans lie horizontal.
But I think that the hinges were designed so you could stop the hatch at any angle you want (this is nor confirmed though, it just appears to me that different photos show different angles...)
well and here's a link for that filter hatch:
http://www.archivesnormandie39-45.org/specificPhoto.php?ref=p002323Greetings,
ekke