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pequeajim
Joined: 03 Sep 2006
Posts: 708
Location: New Holland, PA
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 Posted: Fri Dec 05, 2008 7:39 pm Post subject: Pitot Tube angle |
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All:
I look at my airplane and notice that the pitot tube angles up a little even when the aircraft is sitting straight and level; is this correct? If not, what all did you do to correct the issue, shim it?
Jim!
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Colin K.
Joined: 04 Sep 2006
Posts: 157
Location: Oklahoma
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| Posted: Sat Dec 06, 2008 6:11 am Post subject: Pitot Tube angle |
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Jim,
I would be interested in the answer to your question.
I would also be interested in how you determine the airplane is straight and level in the pitch axis?
Colin K.
OK
Lightning # 52 under construction.
http://www.mykitlog.com/cojaken
[quote]
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Colin K.
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N1BZRich(at)aol.com
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| Posted: Sat Dec 06, 2008 7:23 am Post subject: Pitot Tube angle |
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In a message dated 12/5/2008 10:39:46 P.M. Eastern Standard Time, pequeajim(at)gmail.com writes:
| Quote: |
I look at my airplane and notice that the pitot tube angles up a little even when the aircraft is sitting straight and level; is this correct? If not, what all did you do to correct the issue, shim it?
|
HI Jim,
The real key is to have the pitot tube aligned so that it is perpendicular to the vertical axis and parallel to the longitudinal axis of the aircraft when the aircraft is in flight - not when sitting on the ground. Or in other words for practicable use, aligned with the relative airflow in front of the wing. Since airplanes fly at different angles of attack at different airspeeds, the actual alignment with the airflow as it meets the wing obviously varies as you change speeds. So in reality, the pitot tube alignment is important, with longitudinal alignment being possibly more critical since we know that the other alignment will change with angle of attack. So get it as accurate as you can. But remember that it will only be exact at one angle of attack.
What is probably more important is the placement of the static ports. The pitot / static tube measures total pressure (or impact pressure) at the nose of the pitot tube and the static pressure of the air stream at side ports. The difference of these pressures, or the dynamic or velocity pressure varies with the square of the gas velocity. So static source is just as important, if not more so, than pitot pressure measurement.
The Lightning kit uses a good pitot / static tube with the static ports right on the tube, so generally your airspeed measurements will be pretty accurate as long as you have the tube parallel to the longitudinal axis and perpendicular to the vertical axis when the airplane is at normal cruise speed. It should be that way when you install it as the plans and build manual call for. The only problem comes when some "delta alpha" (dumb ass) walks into it at an airshow and bends it. Yes, that has happened to me at Oshkosh. I just bent it back to a TLAR measurement and it seems to be OK. (TLAR = that looks about right).
Hope all this helps.
Buz
Make your life easier with all your friends, email, and favorite sites in one place. Try it now.
[quote][b]
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Colin K.
Joined: 04 Sep 2006
Posts: 157
Location: Oklahoma
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| Posted: Sat Dec 06, 2008 9:19 am Post subject: Pitot Tube angle |
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Thanks Buz. I think that addresses my question too!
Colin K.
OK
Lightning # 52 under construction.
http://www.mykitlog.com/cojaken
[quote]
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Colin K.
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pequeajim
Joined: 03 Sep 2006
Posts: 708
Location: New Holland, PA
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| Posted: Sat Dec 06, 2008 10:11 am Post subject: Pitot Tube angle |
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I used a digital level with a 2” x 4” and judged it the best I could.
From: owner-lightning-list-server(at)matronics.com [mailto:owner-lightning-list-server(at)matronics.com] On Behalf Of Colin J. Kennedy
Sent: Saturday, December 06, 2008 9:11 AM
To: lightning-list(at)matronics.com
Subject: RE: Pitot Tube angle
Jim,
I would be interested in the answer to your question.
I would also be interested in how you determine the airplane is straight and level in the pitch axis?
Colin K.
OK
Lightning # 52 under construction.
http://www.mykitlog.com/cojaken
[quote]
--
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http://www.matronics.com/Navigator?Lightning-List |
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pequeajim
Joined: 03 Sep 2006
Posts: 708
Location: New Holland, PA
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| Posted: Sat Dec 06, 2008 10:12 am Post subject: Pitot Tube angle |
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(grin), as usual, thanks Buz.
From: owner-lightning-list-server(at)matronics.com [mailto:owner-lightning-list-server(at)matronics.com] On Behalf Of N1BZRich(at)aol.com
Sent: Saturday, December 06, 2008 10:23 AM
To: lightning-list(at)matronics.com
Subject: Re: Pitot Tube angle
In a message dated 12/5/2008 10:39:46 P.M. Eastern Standard Time, pequeajim(at)gmail.com writes:
| Quote: |
I look at my airplane and notice that the pitot tube angles up a little even when the aircraft is sitting straight and level; is this correct? If not, what all did you do to correct the issue, shim it?
|
HI Jim,
The real key is to have the pitot tube aligned so that it is perpendicular to the vertical axis and parallel to the longitudinal axis of the aircraft when the aircraft is in flight - not when sitting on the ground. Or in other words for practicable use, aligned with the relative airflow in front of the wing. Since airplanes fly at different angles of attack at different airspeeds, the actual alignment with the airflow as it meets the wing obviously varies as you change speeds. So in reality, the pitot tube alignment is important, with longitudinal alignment being possibly more critical since we know that the other alignment will change with angle of attack. So get it as accurate as you can. But remember that it will only be exact at one angle of attack.
What is probably more important is the placement of the static ports. The pitot / static tube measures total pressure (or impact pressure) at the nose of the pitot tube and the static pressure of the air stream at side ports. The difference of these pressures, or the dynamic or velocity pressure varies with the square of the gas velocity. So static source is just as important, if not more so, than pitot pressure measurement.
The Lightning kit uses a good pitot / static tube with the static ports right on the tube, so generally your airspeed measurements will be pretty accurate as long as you have the tube parallel to the longitudinal axis and perpendicular to the vertical axis when the airplane is at normal cruise speed. It should be that way when you install it as the plans and build manual call for. The only problem comes when some "delta alpha" (dumb ass) walks into it at an airshow and bends it. Yes, that has happened to me at Oshkosh. I just bent it back to a TLAR measurement and it seems to be OK. (TLAR = that looks about right).
Hope all this helps.
Buz
Make your life easier with all your friends, email, and favorite sites in one place. Try it now.
| Quote: | | http://www.matronics.com/contribution |
01234567890123
[quote][b]
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pennington(at)q.com
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| Posted: Sun Dec 07, 2008 4:20 am Post subject: Pitot Tube angle |
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<?xml:namespace prefix="v" /><?xml:namespace prefix="o" /><![endif]--> Buz
You are a real prize. I've never met you, but, I really like you. Some day I would enjoy the honor of meeting and talking to you.
Gary Pennington
[quote] ---
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info(at)flylightning.net
Guest
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| Posted: Mon Dec 08, 2008 6:21 am Post subject: Pitot Tube angle |
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Jim,
You palm works well to give it a slight bend until the tube us level with the cockpit…
Nick
From: owner-lightning-list-server(at)matronics.com [mailto:owner-lightning-list-server(at)matronics.com] On Behalf Of Jim Langley
Sent: Friday, December 05, 2008 9:39 PM
To: lightning-list(at)matronics.com
Subject: Pitot Tube angle
All:
I look at my airplane and notice that the pitot tube angles up a little even when the aircraft is sitting straight and level; is this correct? If not, what all did you do to correct the issue, shim it?
Jim! | Quote: | | http://www.matronics.com/contribution |
01234567890123
[quote][b]
| | - The Matronics Lightning-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?Lightning-List |
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pequeajim
Joined: 03 Sep 2006
Posts: 708
Location: New Holland, PA
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| Posted: Mon Dec 08, 2008 8:10 am Post subject: Pitot Tube angle |
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Sounds good, thanks nick.
On Mon, Dec 8, 2008 at 9:21 AM, flylightning <info(at)flylightning.net (info(at)flylightning.net)> wrote:
[quote]
Jim,
You palm works well to give it a slight bend until the tube us level with the cockpit…
Nick
From: owner-lightning-list-server(at)matronics.com (owner-lightning-list-server(at)matronics.com) [mailto:owner-lightning-list-server(at)matronics.com (owner-lightning-list-server(at)matronics.com)] On Behalf Of Jim Langley
Sent: Friday, December 05, 2008 9:39 PM
To: lightning-list(at)matronics.com (lightning-list(at)matronics.com)
Subject: Pitot Tube angle
All:
I look at my airplane and notice that the pitot tube angles up a little even when the aircraft is sitting straight and level; is this correct? If not, what all did you do to correct the issue, shim it?
Jim! 0 12 3
[b]
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http://www.matronics.com/Navigator?Lightning-List |
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