Originally Posted by
Bassman1985
Holy crap, who designed that POS? This isn't a DC-9 from the 60s we're talking about, even the Saab from the early 80s made more sense. This reads like a procedure from the good old days when you had the plumber sitting behind you.
The point is, it's not an issue/hasn't been an issue as long as the type 4 isn't applied on the top of the fuselage. Now, in their infinite wisdom, the FAA has determined that the top of the fuselage is a critical surface and requires anti-icing of that surface. You can't take off with wing and engine anti-ice on without the APU providing 10th stage air for the cabin. If you do, the type 4 can get ingested into the APU and things get messy.
I haven't seen much of a problem with the unpressurized takeoff. There is no reason to open the emergency depress valve. The ram air SOV is opened and the packs are off. Climbing at 2500 fpm, the cabin stays well below 1000 fpm, with a bit of a squeeze when the packs come on.