Why the hell is this stuff approved for deicing then?
I have seen it oozing down the fuselage of the same type on stand at destination, at least 2 hours after it was applied at the other end, and after a rotation a flight and a landing of course. It is not supposed to be there.
I have watched it freeze at the end of flap mount fairings on 737 where I have presumed that it can cause no harm, and then watched it thaw again on decent.
It is unbelievable that so much cost and effort is expended by aviation designers and testers to avoid these things, but as soon as the certication is issued it becomes "one of those things" associated with very loose interpretation by groundrats, engineers and pilots alike, and drags on as such for decades all supported with notions like "yeah it's normal" or "well we've no evidence it has caused any accidents".