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  #11  
Old 06-10-2019, 10:14 AM
Steve Melton's Avatar
Steve Melton Steve Melton is offline
 
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when the pressure goes up, it is increasing. when the pressure goes down, it is decreasing. when the pressure is static, it is the same. also, if the pressure is going up and down equally at the same time, it is static.

it this is the case, I would look for bugs in the line.
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Last edited by Steve Melton : 06-10-2019 at 10:21 AM.
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  #12  
Old 06-10-2019, 10:35 AM
lr172 lr172 is offline
 
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Quote:
Originally Posted by vic syracuse View Post
Wrong. Actually, pressure is increasing within the static line. Outside atmospheric pressure is dropping as you climb. Due to the static line being a closed loop system due to the blockage, the pressure within the line increases.

Vic
This logic only applies with a flexible walled material, like a diaphragm or a bag of chips that pops open in the climb. It does not apply to a rigid walled tube, like a static line, that eliminates the influence of ambient pressure. The pressure will remain constant from the time it was blocked and will not be influenced by the ambient pressure. It does increase on a "relative" basis compared to a reducing ambient pressure, but it does not increase per se.

relative to the point I think you were trying to make (pressure differential) - As the ambien pressure decreases, the higher pressure in the blocked line will exhibit an ever increasing force against any diaphragm (flexible material) in the blocked segment that has a pressure of an increasingly lower value on the opposite side. This is due to the increased pressure differential across the diaphragm and NOT an increase of the blocked pressure level.
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Last edited by lr172 : 06-10-2019 at 11:05 AM.
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  #13  
Old 06-10-2019, 10:47 AM
rv7charlie rv7charlie is offline
 
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Quote:
Originally Posted by vic syracuse View Post
Wrong. Actually, pressure is increasing within the static line. Outside atmospheric pressure is dropping as you climb. Due to the static line being a closed loop system due to the blockage, the pressure within the line increases.

Vic
Hmmm. Other than due to temperature increase, or shrinking container, how can pressure rise in a closed container?
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  #14  
Old 06-10-2019, 10:58 AM
BobTurner BobTurner is online now
 
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The on-going arguement is whether you are referring to absolute pressure in the line (most are) or ‘gauge pressure’, what a standard gauge would read. Most gauges read the pressure difference between where they’re hooked to, and the outside world (e.g. a tire pressure gauge attached to a deflated tire reads zero, not 14.7 psi). This confusion tripped up a well-known theoretical physicist during the NFL ‘deflate-gate’)
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  #15  
Old 06-10-2019, 10:59 AM
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Bill Boyd Bill Boyd is offline
 
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Quote:
Originally Posted by rv7charlie View Post
Hmmm. Other than due to temperature increase, or shrinking container, how can pressure rise in a closed container?
Now don't you go bringing your ideal gas equations in here, mister. We don't do Boyle's Law. Heck, in VAF we don't even do Cole's Law, except on barbecue.

What about carbonation? Did you think of that? Carbonated beverage trapped in the static line could make the pressure increase. Or Alka-Seltzer. Lots of possibilities, Charlie.



Like I said (and I'm sorry I mentioned it now) "Minor point." Vic is absolutely right about the effect of a blocked static line on instrument readings. We just disagree on some semantics, more or less.
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  #16  
Old 06-10-2019, 11:23 AM
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Carl Froehlich Carl Froehlich is offline
 
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Quote:
Originally Posted by Alan Cockrell View Post
Heated elenent.
By chance is this a pitot/static combination pitot, the kind that has the static holes drilled along the circumference of the probe (the old Gretz heated pitot)?

Carl
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