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cjaviator(at)gmail.com
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 Posted: Mon Feb 13, 2012 9:59 pm Post subject: Nanchang MAUW |
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Hi all...
anyone no of an official MAUW for the Nanchang?
The reason I ask is that we have just installed the 120 litre bladder tanks and with 2 people, 240 litres of fuel and, say, 20kg of bags we come out at about 1530 kg (3366 lb)
When the first CJ came into New Zealand they were unable to find a published MAUW and chose 1400 kg as this was the cut-off point for the cheapest landing fees and so forth... nothing to do with the aircraft so to speak!
Incidentally, to flog a dead horse, after revising the fuel vent system as per the instructions (inclulding new vent lines from the tanks) and alternating the collector tank flapper valves from one side to the other, the blasted thing still feeds from the LH tank first!
Must be the rigging/balance!
Cheers, Jay
New Zealand
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wlannon(at)shaw.ca
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| Posted: Tue Feb 14, 2012 9:39 am Post subject: Nanchang MAUW |
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Jay;
1400 Kg. is the “Normal flying weight” per the Tech. Specs. manual. This has been accepted by Canadian authorities as the MAUW.
I think the UK and the US are the same though someone else should correct if not so.
As to your fuel imbalance I can say only of course. The vent system is not the problem! But I have said it before and no one seems interested.
Walt
From: Jay McIntyre (cjaviator(at)gmail.com)
Sent: Monday, February 13, 2012 9:58 PM
To: yak list (yak-list(at)matronics.com)
Subject: Nanchang MAUW
Hi all...
anyone no of an official MAUW for the Nanchang?
The reason I ask is that we have just installed the 120 litre bladder tanks and with 2 people, 240 litres of fuel and, say, 20kg of bags we come out at about 1530 kg (3366 lb)
When the first CJ came into New Zealand they were unable to find a published MAUW and chose 1400 kg as this was the cut-off point for the cheapest landing fees and so forth... nothing to do with the aircraft so to speak!
Incidentally, to flog a dead horse, after revising the fuel vent system as per the instructions (inclulding new vent lines from the tanks) and alternating the collector tank flapper valves from one side to the other, the blasted thing still feeds from the LH tank first!
Must be the rigging/balance!
Cheers, Jay
New Zealand
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jonboede(at)hotmail.com
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| Posted: Tue Feb 14, 2012 9:46 am Post subject: Nanchang MAUW |
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Hahaha... if we made every person who comes to the Yak List complaining about fuel-feed imbalance buy a beer for thinking it's the venting... we'd all be alcoholics by now. 
Jon
From: wlannon(at)shaw.ca
To: yak-list(at)matronics.com
Subject: Re: Nanchang MAUW
Date: Tue, 14 Feb 2012 09:38:38 -0800
Jay;
1400 Kg. is the “Normal flying weight” per the Tech. Specs. manual. This has been accepted by Canadian authorities as the MAUW.
I think the UK and the US are the same though someone else should correct if not so.
As to your fuel imbalance I can say only of course. The vent system is not the problem! But I have said it before and no one seems interested.
Walt
From: Jay McIntyre (cjaviator(at)gmail.com)
Sent: Monday, February 13, 2012 9:58 PM
To: yak list (yak-list(at)matronics.com)
Subject: Nanchang MAUW
Hi all...
anyone no of an official MAUW for the Nanchang?
The reason I ask is that we have just installed the 120 litre bladder tanks and with 2 people, 240 litres of fuel and, say, 20kg of bags we come out at about 1530 kg (3366 lb)
When the first CJ came into New Zealand they were unable to find a published MAUW and chose 1400 kg as this was the cut-off point for the cheapest landing fees and so forth... nothing to do with the aircraft so to speak!
Incidentally, to flog a dead horse, after revising the fuel vent system as per the instructions (inclulding new vent lines from the tanks) and alternating the collector tank flapper valves from one side to the other, the blasted thing still feeds from the LH tank first!
Must be the rigging/balance!
Cheers, Jay
New Zealand
[quote]
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Etienne Verhellen
Joined: 13 Apr 2007
Posts: 141
Location: Belgium
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| Posted: Tue Feb 14, 2012 11:12 am Post subject: Re: Nanchang MAUW |
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You are right Walt.
For the UK CAA, the MTOW for the Nanchang is also 1400 kg :
http://www.caa.co.uk/application.aspx?catid=60&pagetype=65&appid=1&mode=summary&aircrafttype=Nanchang
For instance, this one based in Belgium, registered G-CJSA :
http://www.caa.co.uk/application.aspx?catid=60&pagetype=65&appid=1&mode=detail&aircrafttype=Nanchang&dataindex=4
http://www.abpic.co.uk/popup.php?q=1304573
For the Yak-52 :
http://www.caa.co.uk/application.aspx?catid=60&pagetype=65&appid=1&mode=summary&aircrafttype=Yak-52
the UK Civil Aviation Authority states a MTOW of 1315 kg or 1415 kg.
MTOW 1315 kg for the standard Yak-52, for instance this one also based in Belgium, registerd G-CBSR :
http://www.caa.co.uk/application.aspx?catid=60&pagetype=65&appid=1&mode=detail&aircrafttype=Yak-52&dataindex=16
MTOW 1415 kg for Yak-52 equipped with Long Range fuel tanks (2 x 80l), e.g. :
http://www.caa.co.uk/application.aspx?catid=60&pagetype=65&appid=1&mode=detail&aircrafttype=Yak-52&dataindex=17
http://www.caa.co.uk/applicationmodules/ginfo/ginfo_photo.aspx?regmark=G-CBSS&imgname=G-CBSS001&imgtype=jpg
Cheers, Etienne.
http://wayakc2012.mfavs.ru/pilots-and-teams.html
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cjpilot710(at)aol.com
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| Posted: Wed Feb 15, 2012 5:56 am Post subject: Nanchang MAUW |
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The main reason for a fuel imbalance, is yaw. It is the same on the T-34 (the model with the same fuel setup). The T-34 guys figured it out along time ago, which they can correct because they have rudder trim. I too put in larger tanks and moved the vents out to the wing tip. Still does the same thing. There maybe other contributing factor but the main one is yaw. Once she starts feeding out of one tank, that tanks gets lighter in weight, that wing start to rise, causing even more "head pressure". At some point in the future I plan on adding an adjustable rudder trim.
Jim "Pappy" Goolsby
In a message dated 2/14/2012 12:39:22 P.M. Eastern Standard Time, wlannon(at)shaw.ca writes:
| Quote: | Jay;
1400 Kg. is the “Normal flying weight” per the Tech. Specs. manual. This has been accepted by Canadian authorities as the MAUW.
I think the UK and the US are the same though someone else should correct if not so.
As to your fuel imbalance I can say only of course. The vent system is not the problem! But I have said it before and no one seems interested.
Walt
From: Jay McIntyre (cjaviator(at)gmail.com)
Sent: Monday, February 13, 2012 9:58 PM
To: yak list (yak-list(at)matronics.com)
Subject: Nanchang MAUW
Hi all...
anyone no of an official MAUW for the Nanchang?
The reason I ask is that we have just installed the 120 litre bladder tanks and with 2 people, 240 litres of fuel and, say, 20kg of bags we come out at about 1530 kg (3366 lb)
When the first CJ came into New Zealand they were unable to find a published MAUW and chose 1400 kg as this was the cut-off point for the cheapest landing fees and so forth... nothing to do with the aircraft so to speak!
Incidentally, to flog a dead horse, after revising the fuel vent system as per the instructions (inclulding new vent lines from the tanks) and alternating the collector tank flapper valves from one side to the other, the blasted thing still feeds from the LH tank first!
Must be the rigging/balance!
Cheers, Jay
New Zealand
| Quote: |
href="http://www.matronics.com/Navigator?Yak-List">http://www.matronics.com/Navigator?Yak-List
href="http://forums.matronics.com">http://forums.matronics.com
href="http://www.matronics.com/contribution">http://www.matronics.com/c
="http://www.matronics.com/Navigator?Yak-List">http://www.matronics.com/Navigator?Yak-List
s.matronics.com/">http://forums.matronics.com
p://www.matronics.com/contribution">http://www.matronics.com/contribution
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[quote][b]
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viperdoc(at)mindspring.co
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| Posted: Wed Feb 15, 2012 6:53 am Post subject: Nanchang MAUW |
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Ahh..that pesky “Step on the Ball” thing again.
Doc
From: owner-yak-list-server(at)matronics.com [mailto:owner-yak-list-server(at)matronics.com] On Behalf Of cjpilot710(at)aol.com
Sent: Wednesday, February 15, 2012 7:54 AM
To: yak-list(at)matronics.com
Subject: Re: Nanchang MAUW
The main reason for a fuel imbalance, is yaw. It is the same on the T-34 (the model with the same fuel setup). The T-34 guys figured it out along time ago, which they can correct because they have rudder trim. I too put in larger tanks and moved the vents out to the wing tip. Still does the same thing. There maybe other contributing factor but the main one is yaw. Once she starts feeding out of one tank, that tanks gets lighter in weight, that wing start to rise, causing even more "head pressure". At some point in the future I plan on adding an adjustable rudder trim.
Jim "Pappy" Goolsby
In a message dated 2/14/2012 12:39:22 P.M. Eastern Standard Time, wlannon(at)shaw.ca (wlannon(at)shaw.ca) writes:
| Quote: |
Jay;
1400 Kg. is the “Normal flying weight” per the Tech. Specs. manual. This has been accepted by Canadian authorities as the MAUW.
I think the UK and the US are the same though someone else should correct if not so.
As to your fuel imbalance I can say only of course. The vent system is not the problem! But I have said it before and no one seems interested.
Walt
From: Jay McIntyre (cjaviator(at)gmail.com)
Sent: Monday, February 13, 2012 9:58 PM
To: yak list (yak-list(at)matronics.com)
Subject: Nanchang MAUW
Hi all...
anyone no of an official MAUW for the Nanchang?
The reason I ask is that we have just installed the 120 litre bladder tanks and with 2 people, 240 litres of fuel and, say, 20kg of bags we come out at about 1530 kg (3366 lb)
When the first CJ came into New Zealand they were unable to find a published MAUW and chose 1400 kg as this was the cut-off point for the cheapest landing fees and so forth... nothing to do with the aircraft so to speak!
Incidentally, to flog a dead horse, after revising the fuel vent system as per the instructions (inclulding new vent lines from the tanks) and alternating the collector tank flapper valves from one side to the other, the blasted thing still feeds from the LH tank first!
Must be the rigging/balance!
Cheers, Jay
New Zealand
0 |
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brian(at)lloyd.com
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| Posted: Wed Feb 15, 2012 7:41 am Post subject: Nanchang MAUW |
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On Wed, Feb 15, 2012 at 5:54 AM, <cjpilot710(at)aol.com (cjpilot710(at)aol.com)> wrote:
| Quote: | The main reason for a fuel imbalance, is yaw. It is the same on the T-34 (the model with the same fuel setup). The T-34 guys figured it out along time ago, which they can correct because they have rudder trim. I too put in larger tanks and moved the vents out to the wing tip. Still does the same thing. There maybe other contributing factor but the main one is yaw. Once she starts feeding out of one tank, that tanks gets lighter in weight, that wing start to rise, causing even more "head pressure". At some point in the future I plan on adding an adjustable rudder trim.
|
Pappy, I love you, but ...
Hey, I know I am pedantic, which means I pick nits, but one of the things I do is teach and one of the things I am rigid about in my teaching is to make sure that the information I give my students is correct to the limits of my ability to do so. It is surprising how even small errors in information can accumulate to produce large errors in the mind of the student. (This is why the instructor needs to be very familiar with the phrases, "I don't know but I will find out," and, "I am not sure but I will find out.")
That having been said, I have to take exception with your beginning statement that yaw is the source of the fuel imbalance. Actually it is that the apparent force on the aircraft, i.e. the vector sum of gravity and centrifugal force, is not "down" and aligned with the vertical axis of the airplane. (And for you other pedants, I know that there is no such thing as centrifugal force, only centripetal force, the effect of which appears to be a force outward from the center of the turn, which has been erroneously named 'centrifugal force' but is really a manifestation of inertia or Newton's 1st law.)
We have an instrument in the cockpit that measures the direction of this force -- the ball. (For the rest of your pedants who know that force is a vector and not a scalar, the G-meter measures the magnitude of this composite force vector.)
What you say about using rudder trim to adjust this direction of this force vector is necessary but not quite correct. The real answer is that, since we are adjusting the aircraft in roll, the correction is applied with the ailerons since they control the aircraft about the roll axis. But since that means that the ailerons are deflected, one wing is flying at a greater AoA than the other, which increases the drag of that wing and producing a torquing force about the yaw axis which produces a turn. In order to counter the resulting rotation about the yaw axis (so there IS a reason to talk about yaw) we use the rudder trim to provide a constant countering force about the yaw axis and stop the turn.
But to be 100% accurate, the force needed to bring the ball into the center comes from the aileron and the force needed to cancel the resulting turn comes from the rudder. When we do this we say that the airplane is flying "coordinated".
And if you have read this whole thing, the bottom line is that you need to calibrate the ball by leveling the airplane and then adjusting the attitude indicator and turn indicator so that their balls are centered. Soon it will become a badge of competency to be able to say to your fellow pilots, "My balls are centered."
--
Brian Lloyd, WB6RQN/J79BPL
3191 Western Dr.
Cameron Park, CA 95682
brian(at)lloyd.com (brian(at)lloyd.com)
+1.767.617.1365 (Dominica)
+1.916.877.5067 (USA)
[quote][b]
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jan.mevis(at)informavia.b
Guest
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| Posted: Wed Feb 15, 2012 8:02 am Post subject: Nanchang MAUW |
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A good, scientific explanation is ALWAYS welcome. I’ve learned something.
Thanks,
Jan
From: owner-yak-list-server(at)matronics.com [mailto:owner-yak-list-server(at)matronics.com] On Behalf Of Brian Lloyd
Sent: woensdag 15 februari 2012 16:40
To: yak-list(at)matronics.com
Subject: Re: Nanchang MAUW
On Wed, Feb 15, 2012 at 5:54 AM, <cjpilot710(at)aol.com (cjpilot710(at)aol.com)> wrote:
The main reason for a fuel imbalance, is yaw. It is the same on the T-34 (the model with the same fuel setup). The T-34 guys figured it out along time ago, which they can correct because they have rudder trim. I too put in larger tanks and moved the vents out to the wing tip. Still does the same thing. There maybe other contributing factor but the main one is yaw. Once she starts feeding out of one tank, that tanks gets lighter in weight, that wing start to rise, causing even more "head pressure". At some point in the future I plan on adding an adjustable rudder trim.
Pappy, I love you, but ...
Hey, I know I am pedantic, which means I pick nits, but one of the things I do is teach and one of the things I am rigid about in my teaching is to make sure that the information I give my students is correct to the limits of my ability to do so. It is surprising how even small errors in information can accumulate to produce large errors in the mind of the student. (This is why the instructor needs to be very familiar with the phrases, "I don't know but I will find out," and, "I am not sure but I will find out.")
That having been said, I have to take exception with your beginning statement that yaw is the source of the fuel imbalance. Actually it is that the apparent force on the aircraft, i.e. the vector sum of gravity and centrifugal force, is not "down" and aligned with the vertical axis of the airplane. (And for you other pedants, I know that there is no such thing as centrifugal force, only centripetal force, the effect of which appears to be a force outward from the center of the turn, which has been erroneously named 'centrifugal force' but is really a manifestation of inertia or Newton's 1st law.)
We have an instrument in the cockpit that measures the direction of this force -- the ball. (For the rest of your pedants who know that force is a vector and not a scalar, the G-meter measures the magnitude of this composite force vector.)
What you say about using rudder trim to adjust this direction of this force vector is necessary but not quite correct. The real answer is that, since we are adjusting the aircraft in roll, the correction is applied with the ailerons since they control the aircraft about the roll axis. But since that means that the ailerons are deflected, one wing is flying at a greater AoA than the other, which increases the drag of that wing and producing a torquing force about the yaw axis which produces a turn. In order to counter the resulting rotation about the yaw axis (so there IS a reason to talk about yaw) we use the rudder trim to provide a constant countering force about the yaw axis and stop the turn.
But to be 100% accurate, the force needed to bring the ball into the center comes from the aileron and the force needed to cancel the resulting turn comes from the rudder. When we do this we say that the airplane is flying "coordinated".
And if you have read this whole thing, the bottom line is that you need to calibrate the ball by leveling the airplane and then adjusting the attitude indicator and turn indicator so that their balls are centered. Soon it will become a badge of competency to be able to say to your fellow pilots, "My balls are centered."
--
Brian Lloyd, WB6RQN/J79BPL
3191 Western Dr.
Cameron Park, CA 95682
brian(at)lloyd.com (brian(at)lloyd.com)
+1.767.617.1365 (Dominica)
+1.916.877.5067 (USA) | Quote: | | http://www.matronics.com/Navigator?Yak-List |
01234567
[quote][b]
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brian(at)lloyd.com
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| Posted: Wed Feb 15, 2012 8:29 am Post subject: Nanchang MAUW |
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On Wed, Feb 15, 2012 at 7:40 AM, Brian Lloyd <brian(at)lloyd.com (brian(at)lloyd.com)> wrote:
And then after all that, I make a stupid mistake. When I wrote this:
| Quote: | But to be 100% accurate, the force needed to bring the ball into the center comes from the aileron and the force needed to cancel the resulting turn comes from the rudder. When we do this we say that the airplane is flying "coordinated".
|
I should have written:
But to be 100% accurate, the force needed to level the wings comes from the aileron and the force needed to cancel the resulting rotation about the yaw axis comes from the rudder. When we do this the ball moves to the center and we say that the airplane is flying "coordinated".
Regardless, my balls are still centered.
--
Brian Lloyd, WB6RQN/J79BPL
3191 Western Dr.
Cameron Park, CA 95682
brian(at)lloyd.com (brian(at)lloyd.com)
+1.767.617.1365 (Dominica)
+1.916.877.5067 (USA)
[quote][b]
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wlannon(at)shaw.ca
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| Posted: Wed Feb 15, 2012 10:15 am Post subject: Nanchang MAUW |
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Brian;
If you have some time to spare would you be kind enough to run a (for you) simple mathematical exercise? Of course it has to do with fuel imbalance in the CJ, my interpretation of that problem and my total inability to convince anyone that it is not the vent system.
Assuming full fuel tanks determine the fuel weight, measure the area of the fuel tank bottom and calculate the resulting pressure in psi.
Examine one of the header tank flapper valves and determine the area of the valve face that is subject to that pressure to open the valve. From that find the actual opening force.
Using the same fuel pressure (or slightly increasing to accommodate the 4 lts in the header tank) determine the area of the valve face that is subject to that pressure to close the valve. Find the actual closing force.
Assuming the impossible flight with zero yaw and zero turbulence or absolutely no outside effect on fuel pressure and determine the change in fuel quantity necessary to open the closed valve.
Actual turbulence and resulting yaw will, in my opinion , be a positive factor in fuel flow. I also believe the preponderance for the LH tank to feed first is a direct result of the difference in lengths of the fuel feed and vent pipelines. The RH tank fuel & vent lines are approx. 2 ft. longer than the LH which, I think, will slightly increase the coefficient of friction enough to cause this, particularly in the fuel line.
When I say the vent system is not the problem I am assuming that both sides are in good condition, internally clean and undamaged and equal with the minor exception noted above.
Look forward to hearing your results. If you can show that I am out to lunch I will shut up and forever hold my peace, which may be hard to do given the three CJ’s whose owners no longer have to think about fuel imbalance.
Thanks;
Walt
From: Brian Lloyd (brian(at)lloyd.com)
Sent: Wednesday, February 15, 2012 7:40 AM
To: yak-list(at)matronics.com (yak-list(at)matronics.com)
Subject: Re: Nanchang MAUW
On Wed, Feb 15, 2012 at 5:54 AM, <cjpilot710(at)aol.com (cjpilot710(at)aol.com)> wrote:
| Quote: | The main reason for a fuel imbalance, is yaw. It is the same on the T-34 (the model with the same fuel setup). The T-34 guys figured it out along time ago, which they can correct because they have rudder trim. I too put in larger tanks and moved the vents out to the wing tip. Still does the same thing. There maybe other contributing factor but the main one is yaw. Once she starts feeding out of one tank, that tanks gets lighter in weight, that wing start to rise, causing even more "head pressure". At some point in the future I plan on adding an adjustable rudder trim.
|
Pappy, I love you, but ...
Hey, I know I am pedantic, which means I pick nits, but one of the things I do is teach and one of the things I am rigid about in my teaching is to make sure that the information I give my students is correct to the limits of my ability to do so. It is surprising how even small errors in information can accumulate to produce large errors in the mind of the student. (This is why the instructor needs to be very familiar with the phrases, "I don't know but I will find out," and, "I am not sure but I will find out.")
That having been said, I have to take exception with your beginning statement that yaw is the source of the fuel imbalance. Actually it is that the apparent force on the aircraft, i.e. the vector sum of gravity and centrifugal force, is not "down" and aligned with the vertical axis of the airplane. (And for you other pedants, I know that there is no such thing as centrifugal force, only centripetal force, the effect of which appears to be a force outward from the center of the turn, which has been erroneously named 'centrifugal force' but is really a manifestation of inertia or Newton's 1st law.)
We have an instrument in the cockpit that measures the direction of this force -- the ball. (For the rest of your pedants who know that force is a vector and not a scalar, the G-meter measures the magnitude of this composite force vector.)
What you say about using rudder trim to adjust this direction of this force vector is necessary but not quite correct. The real answer is that, since we are adjusting the aircraft in roll, the correction is applied with the ailerons since they control the aircraft about the roll axis. But since that means that the ailerons are deflected, one wing is flying at a greater AoA than the other, which increases the drag of that wing and producing a torquing force about the yaw axis which produces a turn. In order to counter the resulting rotation about the yaw axis (so there IS a reason to talk about yaw) we use the rudder trim to provide a constant countering force about the yaw axis and stop the turn.
But to be 100% accurate, the force needed to bring the ball into the center comes from the aileron and the force needed to cancel the resulting turn comes from the rudder. When we do this we say that the airplane is flying "coordinated".
And if you have read this whole thing, the bottom line is that you need to calibrate the ball by leveling the airplane and then adjusting the attitude indicator and turn indicator so that their balls are centered. Soon it will become a badge of competency to be able to say to your fellow pilots, "My balls are centered."
--
Brian Lloyd, WB6RQN/J79BPL
3191 Western Dr.
Cameron Park, CA 95682
brian(at)lloyd.com (brian(at)lloyd.com)
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brian(at)lloyd.com
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| Posted: Wed Feb 15, 2012 11:36 am Post subject: Nanchang MAUW |
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On Wed, Feb 15, 2012 at 10:14 AM, Walter Lannon <wlannon(at)shaw.ca (wlannon(at)shaw.ca)> wrote:
| Quote: | Brian;
If you have some time to spare would you be kind enough to run a (for you) simple mathematical exercise? Of course it has to do with fuel imbalance in the CJ, my interpretation of that problem and my total inability to convince anyone that it is not the vent system.
Assuming full fuel tanks determine the fuel weight, measure the area of the fuel tank bottom and calculate the resulting pressure in psi.
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It doesn't require any knowledge of area or volume. Pressure is entirely a function of head. Shape isn't involved at all.
| Quote: |
Examine one of the header tank flapper valves and determine the area of the valve face that is subject to that pressure to open the valve. From that find the actual opening force.
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That is too complex because I don't know all the forces involved. You will have to actually measure the required pressure and differences in hinge friction will have a substantial effect on the result.
| Quote: |
Using the same fuel pressure (or slightly increasing to accommodate the 4 lts in the header tank) determine the area of the valve face that is subject to that pressure to close the valve. Find the actual closing force.
Assuming the impossible flight with zero yaw and zero turbulence or absolutely no outside effect on fuel pressure and determine the change in fuel quantity necessary to open the closed valve.
Actual turbulence and resulting yaw will, in my opinion , be a positive factor in fuel flow. I also believe the preponderance for the LH tank to feed first is a direct result of the difference in lengths of the fuel feed and vent pipelines. The RH tank fuel & vent lines are approx. 2 ft. longer than the LH which, I think, will slightly increase the coefficient of friction enough to cause this, particularly in the fuel line.
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The effect of viscosity on the flow of the air in the vent is inconsequential compared to the effect of viscosity on the flow of the fuel in the fuel line so you can discard differential pressure in the vent system as an issue.
But here is the thing that most people miss. If the flapper valve is closed, there is no flow. None. So the actual pressures seen in the system in that case are entirely static and entirely a function of head. It doesn't matter how big or long the fuel or vent lines are to the act of opening the flapper valve.
Now, if both flapper valves are open the same amount there might be a slight difference in flow from both tanks due to length and topology of the intervening fuel lines but I think that if you actually measure it, the difference would be inconsequential.
So, I keep coming back to the same point: if your flapper valves, fuel lines, and vent system (stock) are in a proper state of repair, flow from the tanks will be determined almost entirely by the effective gravitational vector as indicated by the position of the ball. If you keep your balls hanging straight, the airplane should reward you with even fuel flow.
| Quote: | When I say the vent system is not the problem I am assuming that both sides are in good condition, internally clean and undamaged and equal with the minor exception noted above.
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Yes.
| Quote: |
Look forward to hearing your results. If you can show that I am out to lunch I will shut up and forever hold my peace, which may be hard to do given the three CJ’s whose owners no longer have to think about fuel imbalance.
|
You know, it doesn't matter what anyone calculates. If you really want to know for a given airplane, jack it up so that it is level and draw fuel from the header tank at a normal rate, e.g. something like 15gph. You probably need to periodically bang on the header tank to overcome stiction in the flapper valves due to the lack of engine vibration. You will most likely find that the tanks drain evenly.
I do know that, in all the CJs and Yak-52s I have flown, when I see an imbalance in fuel, I just slip the airplane to move the ball in the direction of the tank with less fuel and I have no problem bringing the fuel level back into balance between tanks. I have never felt a need to do anything to the fuel system other than that.
And I am really not interested in arguing about anything here. Nothing trumps actual empirical measurement and I don't plan to bother with that myself.
--
Brian Lloyd, WB6RQN/J79BPL
3191 Western Dr.
Cameron Park, CA 95682
brian(at)lloyd.com (brian(at)lloyd.com)
+1.767.617.1365 (Dominica)
+1.916.877.5067 (USA)
[quote][b]
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mark.bitterlich(at)navy.m
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| Posted: Wed Feb 15, 2012 12:00 pm Post subject: Nanchang MAUW |
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Brian, an alternative answer might have been:
"I don't know, and I don't plan to bother finding out myself".
Being a teacher myself, that is how I would have put it.
This is Mark, just pulling your leg a little bit. Have a nice day!
--
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brian(at)lloyd.com
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| Posted: Wed Feb 15, 2012 12:22 pm Post subject: Nanchang MAUW |
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On Wed, Feb 15, 2012 at 11:59 AM, Bitterlich, Mark G CIV Det Cherry Point, MALS-14 64E <mark.bitterlich(at)navy.mil (mark.bitterlich(at)navy.mil)> wrote:
| Quote: | --> Yak-List message posted by: "Bitterlich, Mark G CIV Det Cherry Point, MALS-14 64E" <mark.bitterlich(at)navy.mil (mark.bitterlich(at)navy.mil)>
Brian, an alternative answer might have been:
"I don't know, and I don't plan to bother finding out myself".
|
I thought that is what I said, with the caveat that the reason is that I have never seen the problem.
--
Brian Lloyd, WB6RQN/J79BPL
3191 Western Dr.
Cameron Park, CA 95682
brian(at)lloyd.com (brian(at)lloyd.com)
+1.767.617.1365 (Dominica)
+1.916.877.5067 (USA)
[quote][b]
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cjpilot710(at)aol.com
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| Posted: Wed Feb 15, 2012 7:23 pm Post subject: Nanchang MAUW |
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Smirk smirk smirk. I wondered when you'd catch that. 
Pappy
In a message dated 2/15/2012 11:29:58 A.M. Eastern Standard Time, brian(at)lloyd.com writes:
| Quote: | On Wed, Feb 15, 2012 at 7:40 AM, Brian Lloyd <brian(at)lloyd.com (brian(at)lloyd.com)> wrote:
And then after all that, I make a stupid mistake. When I wrote this:
| Quote: | But to be 100% accurate, the force needed to bring the ball into the center comes from the aileron and the force needed to cancel the resulting turn comes from the rudder. When we do this we say that the airplane is flying "coordinated".
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I should have written:
But to be 100% accurate, the force needed to level the wings comes from the aileron and the force needed to cancel the resulting rotation about the yaw axis comes from the rudder. When we do this the ball moves to the center and we say that the airplane is flying "coordinated".
Regardless, my balls are still centered.
--
Brian Lloyd, WB6RQN/J79BPL
3191 Western Dr.
Cameron Park, CA 95682
brian(at)lloyd.com (brian(at)lloyd.com)
+1.767.617.1365 (Dominica)
+1.916.877.5067 (USA)
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[quote][b]
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wlannon(at)shaw.ca
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| Posted: Wed Feb 15, 2012 8:10 pm Post subject: Nanchang MAUW |
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That’s too bad Brian. I thought you might enjoy the challenge. My mistake.
Walt
From: Brian Lloyd (brian(at)lloyd.com)
Sent: Wednesday, February 15, 2012 11:34 AM
To: yak-list(at)matronics.com (yak-list(at)matronics.com)
Subject: Re: Nanchang MAUW
On Wed, Feb 15, 2012 at 10:14 AM, Walter Lannon <wlannon(at)shaw.ca (wlannon(at)shaw.ca)> wrote:
| Quote: | Brian;
If you have some time to spare would you be kind enough to run a (for you) simple mathematical exercise? Of course it has to do with fuel imbalance in the CJ, my interpretation of that problem and my total inability to convince anyone that it is not the vent system.
Assuming full fuel tanks determine the fuel weight, measure the area of the fuel tank bottom and calculate the resulting pressure in psi.
|
It doesn't require any knowledge of area or volume. Pressure is entirely a function of head. Shape isn't involved at all.
| Quote: |
Examine one of the header tank flapper valves and determine the area of the valve face that is subject to that pressure to open the valve. From that find the actual opening force.
|
That is too complex because I don't know all the forces involved. You will have to actually measure the required pressure and differences in hinge friction will have a substantial effect on the result.
| Quote: |
Using the same fuel pressure (or slightly increasing to accommodate the 4 lts in the header tank) determine the area of the valve face that is subject to that pressure to close the valve. Find the actual closing force.
Assuming the impossible flight with zero yaw and zero turbulence or absolutely no outside effect on fuel pressure and determine the change in fuel quantity necessary to open the closed valve.
Actual turbulence and resulting yaw will, in my opinion , be a positive factor in fuel flow. I also believe the preponderance for the LH tank to feed first is a direct result of the difference in lengths of the fuel feed and vent pipelines. The RH tank fuel & vent lines are approx. 2 ft. longer than the LH which, I think, will slightly increase the coefficient of friction enough to cause this, particularly in the fuel line.
|
The effect of viscosity on the flow of the air in the vent is inconsequential compared to the effect of viscosity on the flow of the fuel in the fuel line so you can discard differential pressure in the vent system as an issue.
But here is the thing that most people miss. If the flapper valve is closed, there is no flow. None. So the actual pressures seen in the system in that case are entirely static and entirely a function of head. It doesn't matter how big or long the fuel or vent lines are to the act of opening the flapper valve.
Now, if both flapper valves are open the same amount there might be a slight difference in flow from both tanks due to length and topology of the intervening fuel lines but I think that if you actually measure it, the difference would be inconsequential.
So, I keep coming back to the same point: if your flapper valves, fuel lines, and vent system (stock) are in a proper state of repair, flow from the tanks will be determined almost entirely by the effective gravitational vector as indicated by the position of the ball. If you keep your balls hanging straight, the airplane should reward you with even fuel flow.
| Quote: | When I say the vent system is not the problem I am assuming that both sides are in good condition, internally clean and undamaged and equal with the minor exception noted above.
|
Yes.
| Quote: |
Look forward to hearing your results. If you can show that I am out to lunch I will shut up and forever hold my peace, which may be hard to do given the three CJ’s whose owners no longer have to think about fuel imbalance.
|
You know, it doesn't matter what anyone calculates. If you really want to know for a given airplane, jack it up so that it is level and draw fuel from the header tank at a normal rate, e.g. something like 15gph. You probably need to periodically bang on the header tank to overcome stiction in the flapper valves due to the lack of engine vibration. You will most likely find that the tanks drain evenly.
I do know that, in all the CJs and Yak-52s I have flown, when I see an imbalance in fuel, I just slip the airplane to move the ball in the direction of the tank with less fuel and I have no problem bringing the fuel level back into balance between tanks. I have never felt a need to do anything to the fuel system other than that.
And I am really not interested in arguing about anything here. Nothing trumps actual empirical measurement and I don't plan to bother with that myself.
--
Brian Lloyd, WB6RQN/J79BPL
3191 Western Dr.
Cameron Park, CA 95682
brian(at)lloyd.com (brian(at)lloyd.com)
+1.767.617.1365 (Dominica)
+1.916.877.5067 (USA)
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samira.h(at)shaw.ca
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| Posted: Thu Feb 16, 2012 7:46 pm Post subject: Nanchang MAUW |
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Walt, you are absolutely right.
Too bad some people don't listen
to you, I guess they like to do
things the hard way.
I always appreciate your postings
on the list very much, thank you
for not giving up.
cheers
Elmar
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Pete Fowler
Joined: 07 Jul 2009
Posts: 76
Location: California
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| Posted: Sat Feb 18, 2012 8:55 am Post subject: Re: Nanchang MAUW |
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LOL, someone lecturing Pappy about flying HAHAHAHAHA!
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brian(at)lloyd.com
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| Posted: Sat Feb 18, 2012 9:17 am Post subject: Nanchang MAUW |
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On Sat, Feb 18, 2012 at 8:55 AM, Pete Fowler <pfdesign1(at)cox.net (pfdesign1(at)cox.net)> wrote:
| Quote: | --> Yak-List message posted by: "Pete Fowler" <pfdesign1(at)cox.net (pfdesign1(at)cox.net)>
LOL, someone lecturing Pappy about flying HAHAHAHAHA!
|
There are no sacred cows in aviation.
--
Brian Lloyd, WB6RQN/J79BPL
3191 Western Dr.
Cameron Park, CA 95682
brian(at)lloyd.com (brian(at)lloyd.com)
+1.767.617.1365 (Dominica)
+1.916.877.5067 (USA)
[quote][b]
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barryhancock
Joined: 09 Oct 2008
Posts: 285
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| Posted: Tue Feb 21, 2012 5:47 pm Post subject: Re: Nanchang MAUW |
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First of all, Brian is right, Pappy is no sacred cow....rather a flying legend, perhaps.
As for fuel imbalance. Since I'm able to effectively trim hands off in my CJ (and others we restored) with 3 axis electric trim, there is no fuel imbalance. Since we replumbed my entire aircraft, we made separate vent lines for the left and right tanks. I don't think this has made a whit of difference, however, but it was simple to do at the time. So, I do think that the comments about yaw inducing the fuel feed imbalance are further supported by my experience (I have stock flopper valves in my header tank).
That being said, I just ferried a CJ for a customer from back east, and by the time I got it here to Utah I had adjusted the trim tabs to where the fuel imbalance was less than 10 liters after a 2+ hour flight. So, it can be mitigated to a certain extent by adjusting the trim tabs.
Barry
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_________________
Barry Hancock
Worldwide Warbirds, Inc.
www.worldwidewarbirds.com |
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bwade154(at)yahoo.com
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| Posted: Wed Feb 22, 2012 7:14 am Post subject: Nanchang MAUW |
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How many have flown routinely with say 30 liters in one tank and 0 in the other the reason I ask is will the fuel flow from the 30 liter tank until empty or will fuel be trapped towards the outside of the tank? As for me when one red light comes on the pucker factor kicks in along with rudder and shortly there after landing.
Bill Wade
From: barryhancock <bhancock(at)worldwidewarbirds.com>
To: yak-list(at)matronics.com
Sent: Tuesday, February 21, 2012 8:47 PM
Subject: Yak-List: Re: Nanchang MAUW
--> Yak-List message posted by: "barryhancock" <bhancock(at)worldwidewarbirds.com (bhancock(at)worldwidewarbirds.com)>
First of all, Brian is right, Pappy is no sacred cow....rather a flying legend, perhaps.
As for fuel imbalance. Since I'm able to effectively trim hands off in my CJ (and others we restored) with 3 axis electric trim, there is no fuel imbalance. Since we replumbed my entire aircraft, we made separate vent lines for the left and right tanks. I don't think this has made a whit of difference, however, but it was simple to do at the time. So, I do think that the comments about yaw inducing the fuel feed imbalance are further supported by my experience (I have stock flopper valves in my header tank).
That being said, I just ferried a CJ for a customer from back east, and by the time I got it here to Utah I had adjusted the trim tabs to where the fuel imbalance was less than 10 liters after a 2+ hour flight. So, it can be mitigated to a certain extent by adjusting the trim tabs.
Barry
--------
Barry Hancock
Worldwide Warbirds, Inc.
(877) 869-6458
www.worldwidewarbirds.com
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=366912#366912
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