pitot-static system
 

In the condition of using alternate static source in an unpressurized airplane, I know there is a lower pressure in the cockpit/cabin than the outside atmosphere. The book always says the low pressure in the cockpit/cabin is due to the slipstream of the airplane. But I don't understand why the slipstream will create a lower pressure inside the cockpit?

Confused....

Open a window and see where the air goes.

Doing Jepp revisions in DC-3 I could make all the old charts disappear.

The external shape of the cockpit/cabin is a lot like a wing. Curved surface on top, flatter on the bottom. Bernoulli works there, too.

The pressure in the cockpit is relatively lower than the outside static pressure, so the high pressure air moves into the low pressure area (cockpit). The smoke will not go out??? and that's why we have to close the windows before activating the fire extinguisher???