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Pitot heater performance

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johnt(at)comp-sol.com
Guest

Posted: Tue Nov 28, 2006 8:45 am Post subject: Pitot heater performance

Anyone,



I'm not underdstanding a point in the http://www.aeroelectric.com/articles/Pitot_Heater/Gauging_Pitot_Heater_Performance.pdf on Bob's website...namely that "If you are considering an AN5814 heated pitot tube installtion, the data gathered suggests that the tube be wired with 14AWG in a metal airplane and perhaps 12AWG in a plastic airplane."



SO - why perhaps 12AWG in a plastic airplane....?



John

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retasker(at)optonline.net
Guest

Posted: Tue Nov 28, 2006 9:57 am Post subject: Pitot heater performance

Just speculation on my part, but I would bet that the metal airplane 

would be using the airframe as a ground return (local to the heater) 

which would be very low resistance and mean that there is effectively a 

one way path for the electrons (through the 14 gauge wire to the heater 

to ground).  In the plastic airplane, the path would be round trip 

(through the 12 gauge wire to the heater and back through the 12 ga wire 

to the common ground).



So the total path length would be twice as much in the plastic airplane, 

hence the larger gauge recommended.



YMMV, my $0.02...  Do not archive



Dick Tasker



John Tvedte wrote:



 	  Quote: 	
		  Anyone,



I'm not underdstanding a point in the http://www.aeroelectric.com/articles/Pitot_Heater/Gauging_Pitot_Heater_Performance.pdf on Bob's website...namely that "If you are considering an AN5814 heated pitot tube installtion, the data gathered suggests that the tube be wired with 14AWG in a metal airplane and perhaps 12AWG in a plastic airplane."



SO - why perhaps 12AWG in a plastic airplane....?



John

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nuckollsr(at)cox.net
Guest

Posted: Tue Nov 28, 2006 11:30 am Post subject: Pitot heater performance

At 12:55 PM 11/28/2006 -0500, you wrote:



 	  Quote: 	
		  John Tvedte wrote:



>Anyone,

>

>I'm not underdstanding a point in the 

>http://www.aeroelectric.com/articles/Pitot_Heater/Gauging_Pitot_Heater_Performance.pdf 

>on Bob's website...namely that "If you are considering an AN5814 heated 

>pitot tube installtion, the data gathered suggests that the tube be wired 

>with 14AWG in a metal airplane and perhaps 12AWG in a plastic airplane."

>

>SO - why perhaps 12AWG in a plastic airplane....?

>

>John


	



<retasker(at)optonline.net>



Just speculation on my part, but I would bet that the metal airplane would 

be using the airframe as a ground return (local to the heater) which would 

be very low resistance and mean that there is effectively a one way path 

for the electrons (through the 14 gauge wire to the heater to ground).  In 

the plastic airplane, the path would be round trip (through the 12 gauge 

wire to the heater and back through the 12 ga wire to the common ground).



So the total path length would be twice as much in the plastic airplane, 

hence the larger gauge recommended.



YMMV, my $0.02...  Do not archive



Dick Tasker



         That's worth at least two-bits Richard. You're

         right on.

         Bob . . .



      ---------------------------------------------------------

      < What is so wonderful about scientific truth...is that >

      < the authority which determines whether there can be   >

      < debate or not does not reside in some fraternity of   >

      < scientists; nor is it divine. The authority rests     >

      < with experiment.                                      >

      <                            --Lawrence M. Krauss       >

      ---------------------------------------------------------

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