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  #1  
Old 11-27-2011, 09:51 PM
stevengrasley stevengrasley is offline
 
Join Date: Oct 2011
Location: Marathon, FL
Posts: 40
Default How many pitot's do you need?

When configuring a -7A for IFR with a glass cockpit is seems the wisdom out there dictates to also install some steam gauge backups. If so, then can a single pitot work for the EFIS ADAHRS and the steam gauge? May sound like a dumb question but I have asked several folks... including AP's...and the range of answers is somewhat astounding. What is the input from the VAF crowd?

Steve
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RV-7A, N783RV
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Lyc O-360-A1A
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  #2  
Old 11-27-2011, 10:00 PM
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AltonD AltonD is offline
 
Join Date: Sep 2005
Location: Dothan, Alabama
Posts: 1,492
Default

I have one pitot feeding an autopilot, steam airspeed, and an AFS3500. There is no flow in the pitot line.
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Alton DeWeese
N526RV RV7A Tip Up, IO360 180 W/Hartzel BA prop.
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  #3  
Old 11-28-2011, 06:05 AM
pierre smith's Avatar
pierre smith pierre smith is offline
 
Join Date: Jan 2005
Location: Louisville, Ga
Posts: 7,885
Default Yep

Since there really isn't any "flow" but rather pressure, you can use one pitot for multiple points.

My -10 has it to a D-100, a standby AS and the TruTrak autopilot.

Best,
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  #4  
Old 11-28-2011, 08:09 AM
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Ironflight Ironflight is offline
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Join Date: Jan 2005
Location: Dayton, NV
Posts: 12,457
Default

For my IFR aircraft, I use a single Pitot (been flying that way for decades in spam cans...). Pitot heat should take care of ice (although I flight plan to avoid evene the potential of icing, or I don't go!) - you are susceptable to a perfectly aimed bug of course. I personally consider that a low risk.
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  #5  
Old 11-28-2011, 08:35 AM
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JoeM JoeM is offline
 
Join Date: May 2011
Location: Perryville, MD
Posts: 93
Default

Just my opinion as a not yet pilot or aircraft owner but it seems the most likely item to cause a failure of the airspeed/altimeter indications would be leaks or clogging of the pitot/static probes and lines. I would see nothing wrong with separate systems.
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  #6  
Old 11-28-2011, 08:57 AM
Sid Lambert Sid Lambert is offline
 
Join Date: Jul 2005
Location: North Atlanta
Posts: 1,120
Default

One for each pilot on-board.
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  #7  
Old 11-28-2011, 09:12 AM
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Mark12A Mark12A is offline
 
Join Date: Jun 2011
Location: Huntsville, AL
Posts: 89
Default Sid Stole It...

I quickly read through the thread title and I though it said, "How many pilots do you need?"

That sounds like the entry line for any number of crude jokes. Especially around fighter pilots.
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  #8  
Old 11-28-2011, 09:32 AM
krw5927 krw5927 is offline
 
Join Date: Aug 2010
Location: Wichita, KS
Posts: 1,966
Default

Put 2 pitots in and you'll always wonder which one's right. Small chance they'll both read exactly the same.

Kind of like asking a guy with 2 watches what time it is.
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  #9  
Old 11-28-2011, 09:57 AM
David Paule David Paule is offline
 
Join Date: Dec 2009
Location: Boulder, CO
Posts: 4,650
Default

Quote:
Originally Posted by Ironflight View Post
....you are susceptable to a perfectly aimed bug of course. I personally consider that a low risk.
If you don't use a pitot cover on the ground, there's a much higher chance for a clogged pitot due to a bug. Happened to me once.

Now I use one of those flip-up-in-the-wind covers, test it on preflight, and in the next 1,400 hours of mostly rural airports, have had no problems and no cover malfunctions.

Here's a link to one:
http://www.aircraftspruce.com/catalo...eprotector.php

The only issue with these is that they pop open during the take-off roll and the airspeed needle swings wildly for a second right when you'd like to have it work. As a result my take-offs are by feel. And before lift-off everything's fine. The gadget is recommended.

Dave
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  #10  
Old 11-28-2011, 02:05 PM
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Don Don is offline
 
Join Date: Jan 2005
Location: Richmond, VA
Posts: 696
Default

Quote:
Originally Posted by Sid Lambert View Post
One for each pilot on-board.
I read it correctly but my first thought was, 'It depends on how many airplanes you own.' I prefer having one pitot for every plane I own. Right now I have two pitot tubes but I might need a third on soon<g>...but the wife doesn't share my opinion...yet.
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