Thread: Alternate Static
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Old 03-23-2014, 07:34 AM
  #9  
MD11
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Joined APC: Dec 2007
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Originally Posted by TheStranger View Post
JNB,
Bones,
I agree, but want to know HOW the heat/defrost ON and vents/windows closed would correct the error.
The free form body of the fuselage accelerates air and therefore reduces the air pressure lower than ambient along the skin. Door and window seals do not seal 100%, thereby allowing cabin air to seep out. The procedure is a two step process: Close the vents windows; this further reduces inner cabin ambient pressure from flowing outside. The second step is to open the heat and defrost. This air is ducted from the heat exchanger (gas heater) in the nose. On the right side of the PA44, I believe there is a NACA scoop that feeds air to the cabin heater. This is ram air pressure. By opening the heater controls, air pressure from that duct is introduced into the cabin further equalizing the difference. If I remember correctly, all non pressurized aircraft standby static vents are plumbed to inside cabin atmosphere.
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