Cabin pressure

[burgessbuilderMO13]

Gents
Does anyone have any information regarding the difference of pressure inside the cockpit in flight versus the outside air pressure?
I would assume that there has to be a differential of some value.
Thanks

 

[Jesse]

I have no idea of actual values, but the main difference would be caused by having fresh air vents open or closed. Opened vents would cause a very slight pressurization of the cabin, but very very small, as the cabin is by no means sealed.

 

[BobTurner]

Download a Cessna 172 POH. The effect of using cabin air as an alternate static is well documented. The air going around the cabin has to speed up, so its pressure drops. Fly with alternate air with the windows open and you get that low pressure air, altimeter and ASI go up. Close the windows and open the heat (cowling pressurized air) and the cabin pressure goes up, altimeter and ASI go down. Everything closed, it pretty much all cancels out. In an RV it probably depends on where the 'leaks' are located. Before I plugged them, I got a lot of cold air from the tail cone entering via the corrigated aft bulkhead.