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Thruster87

Joined: 16 Apr 2008
Posts: 193
Location: Australia

Posted: Mon Aug 10, 2009 1:29 am Post subject: Calibrating fuel qty gauges

How do you calibrate fuel qty using  a 10 - 75 ohm sender unit with a 0 -90 ohm fuel gauge? in other words what's the best why to get the gauges to read accurately near empty,  which is more important then FULL. Thanks

pwmac(at)sisna.com
Guest

Posted: Mon Aug 10, 2009 5:55 am Post subject: Calibrating fuel qty gauges

Buy a Cruz Pro gauge and calibrate is evey 1 gallon at the low end.

PW

===========

At 03:29 AM 8/10/2009, you wrote:

 	  Quote: 	
		  



How do you calibrate fuel qty using  a 10 - 75 ohm sender unit with 

a 0 -90 ohm fuel gauge? in other words what's the best why to get 

the gauges to read accurately near empty,  which is more important 

then FULL. Thanks





Read this topic online here:



http://forums.matronics.com/viewtopic.php?p 56888#256888

nuckolls.bob(at)aeroelect
Guest

Posted: Mon Aug 10, 2009 7:30 am Post subject: Calibrating fuel qty gauges

At 04:29 AM 8/10/2009, you wrote:

  	  Quote: 	
		  --> AeroElectric-List message posted by: "Thruster87" <alania(at)optusnet.com.au>



 How do you calibrate fuel qty using  a 10 - 75 ohm sender unit with a 0 -90 ohm fuel gauge? in other words what's the best why to get the gauges to read accurately near empty,  which is more important then FULL. Thanks 	


     The floats-on-a-swing-arm senders are

     a legacy product from cars and other

     vehicles that go back a very long way.



     Making these things really accurate in more\

     than one place is a bit fussy.



     Years ago, we crafted an electronic signal

     conditioning board for the Bonanzas and Barons

     that allowed dead-on calibration of empty

     and full. All other readings across the scale

     simply fell where where the physics of the

     sender dictates. The physics of these devices

     are affected mildly by linearity of the wire

     wound sensor resistor (usually within 5% of

     true) but a whole lot by trigonometry of

     the swing arm and tank geometry.



     But as you've already recognized, the one

     level you really want to be accurate is

     the empty point. For this you can do some

     things with series calibration resistors

     and/or bending the float arm on the sender.

     This CAN be a tedious, trial-by-error activity.



     If it were my airplane, I'd probably craft

     a microprocessor based signal conditioner

     that would allow me to take readings at 5%

     increments from empty to full and generate

     a lookup table that converts as-installed

     sender (transducer) readings into real

     numbers. The BEST way to watch full levels

     is with installation of a "dip stick" style

     sensor at the low fuel warning level (generally

     1/4 to 1/3 tank). Consider devices like this:



 [img]cid:.0[/img]

     One of these stuck through the tank wall at

     the warning level will light a lamp on the

     panel at the desired fuel quantity with

     no risk for drift of calibration. See:



  http://www.gemssensors.com/content.aspx?id 82



     This is the no-brainer, dead-nuts accurate

     low liquid lever sensing method I know of.

     Capacity fuel gages with processor augmentation

     are also easy to calibrate . . . but I think

     I could get by with no active fuel gaging

     other than a set of optical level detectors

     cited above.



 

        Bob . . .



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

        ( . . .  a long habit of not thinking   )

        ( a thing wrong, gives it a superficial )

        ( appearance of being right . . .       )

        (                                       )

        (                  -Thomas Paine 1776-  )

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

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Speedy11(at)aol.com
Guest

Posted: Wed Aug 12, 2009 8:37 am Post subject: Calibrating fuel qty gauges

Bob,

 These fuel sensors are a great idea.  I wish I had seen them while  building.  I could have installed three of them in the wing root of each  tank - one at "wing root full," one at "wing root half," and one at "wing root"  empty (maybe two gal remaining).  They would have been easy to calibrate  and label on the panel.  Then I would know exactly the fuel remaining at  those levels.

 The Princeton Capacitance Sensors I bought and connected to the AF-3400 EM  do not work.  I've calibrated them 7 times and they still fluctuate  between full and 8 gallons when the tanks are full and fluctuate wildly when  less than full.  Perhaps I've done something wrong in the calibration - I  know most errors are installation or operator errors - but, I tried to follow  the AF-3400 instructions accurately.

 Anyway, I may try to retro fit the Gem sensors.

 Stan Sutterfield

  

  	  Quote: 	
		  http://www.gemssensors.com/content.aspx?id=282



        This is the no-brainer, dead-nuts accurate

        low liquid lever sensing method I know of. 	


 

  

 

  [quote][b]

nuckolls.bob(at)aeroelect
Guest

Posted: Wed Aug 12, 2009 1:08 pm Post subject: Calibrating fuel qty gauges

At 11:32 AM 8/12/2009, you wrote:

  	  Quote: 	
		   Bob,

 These fuel sensors are a great idea.  I wish I had seen them while building.  I could have installed three of them in the wing root of each tank - one at "wing root full," one at "wing root half," and one at "wing root" empty (maybe two gal remaining).  They would have been easy to calibrate and label on the panel.  Then I would know exactly the fuel remaining at those levels.

 The Princeton Capacitance Sensors I bought and connected to the AF-3400 EM do not work.  I've calibrated them 7 times and they still fluctuate between full and 8 gallons when the tanks are full and fluctuate wildly when less than full.  Perhaps I've done something wrong in the calibration - I know most errors are installation or operator errors - but, I tried to follow the AF-3400 instructions accurately.

 Anyway, I may try to retro fit the Gem sensors. 	


   I'm sorry to hear that the capacity sensors are

   not performing for you. I presume you've already

   had discussions with the factory. These SHOULD be

   pretty stable. There are design issues with respect

   to variable dielectric constant of the fuel. But

   this is a calibration error, not a dynamic level

   sensing problem.



   I've been fiddling with a processor based capacity

   gaging amplifier for a TC application. Having a

   micro-controller in the system opens a lot of interesting

   doors including calibrating to the as-installed

   sensor and tank combination and compensating for

   temperature and dielectric constant as well.



   Depending on what I learn with this program, I may

   have a similarly agile capacity fuel gage amplifier

   product to offer. However, even if our latest-n-greatest

   gage makes it to production, it will still be augmented

   with electro-optic, dip-sticks for absolute low-liquid

   warning. I did the first such sensors to find their

   way onto Beech products about 1980.



  http://www.electromech.com/liquidlevel3RED.html



   They've now been produced in dozens of configurations

   and tens of thousands of fielded product. One of

   my more prolific brainstorms.



 

        Bob . . .



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

        ( . . .  a long habit of not thinking   )

        ( a thing wrong, gives it a superficial )

        ( appearance of being right . . .       )

        (                                       )

        (                  -Thomas Paine 1776-  )

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



     [quote][b]

pwmac(at)sisna.com
Guest

Posted: Wed Aug 12, 2009 2:17 pm Post subject: Calibrating fuel qty gauges

In my past life we used 3 fixed point ultrasonic sensors on the bottom of the rocket tanks. It took 3 to overcome the slosh issues. 

  IMO, fixed point sensors are not workable in a plane. An analog design is required. The best solution I have seen and I use is a simple boat turbine flow meter made by Northstar. The gauge reads gal/hour, gal remaining, and gal used. It has to be updated each time fuel is added. It is accurate after the initial fill. One still has to remember how many gallons is safe when the tank gets low. Many homebuilts use this product with success. No issues with slosh.



 I am trying the CruzPro gauge for my truck which allows many cal points and the gauge reads the same stuff as the Northstar. This setup uses the stock resistance gauge and is still inaccurate due to slosh and tilt. However there is some damping in the float mechanism.



 Paul

 =================



 [quote]At 11:32 AM 8/12/2009, you wrote:

  	  Quote: 	
		  Bob,

 These fuel sensors are a great idea.  I wish I had seen them while building.  I could have installed three of them in the wing root of each tank - one at "wing root full," one at "wing root half," and one at "wing root" empty (maybe two gal remaining).  They would have been easy to calibrate and label on the panel.  Then I would know exactly the fuel remaining at those levels.

 The Princeton Capacitance Sensors I bought and connected to the AF-3400 EM do not work.  I've calibrated them 7 times and they still fluctuate between full and 8 gallons when the tanks are full and fluctuate wildly when less than full.  Perhaps I've done something wrong in the calibration - I know most errors are installation or operator errors - but, I tried to follow the AF-3400 instructions accurately.

 Anyway, I may try to retro fit the Gem sensors. 	


   I'm sorry to hear that the capacity sensors are

   not performing for you. I presume you've already

   had discussions with the factory. These SHOULD be

   pretty stable. There are design issues with respect

   to variable dielectric constant of the fuel. But

   this is a calibration error, not a dynamic level

   sensing problem.



   I've been fiddling with a processor based capacity

   gaging amplifier for a TC application. Having a

   micro-controller in the system opens a lot of interesting

   doors including calibrating to the as-installed

   sensor and tank combination and compensating for

   temperature and dielectric constant as well.



   Depending on what I learn with this program, I may

   have a similarly agile capacity fuel gage amplifier

   product to offer. However, even if our latest-n-greatest

   gage makes it to production, it will still be augmented

   with electro-optic, dip-sticks for absolute low-liquid

   warning. I did the first such sensors to find their

   way onto Beech products about 1980.



  http://www.electromech.com/liquidlevel3RED.html



   They've now been produced in dozens of configurations

   and tens of thousands of fielded product. One of

   my more prolific brainstorms.



        Bob . . .



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

        ( . . .  a long habit of not thinking   )

        ( a thing wrong, gives it a superficial )

        ( appearance of being right . . .       )

        (                                       )

        (                  -Thomas Paine 1776-  )

         ---------------------------------------[b]

bbradburry(at)bellsouth.n
Guest

Posted: Wed Aug 12, 2009 2:33 pm Post subject: Calibrating fuel qty gauges

I have the Princeton capacitance sensors in my Lancair.  I have not yet calbrated them, but I would be very shocked if the fuel slosh didn’t cause a lot of errors.  The sensors are about 6 feet long and must be no more than 20 degrees off of horizontal.  Fuel sloshing would move a great distance up and down the tubes.  I have them in there because FAA says I need a fuel guage.  I will check the level visually before each flight and refill when I should be at ¼ to ½ tank.  Reguardless of what the fuel gage says!  

   

Bill B   

  

       

  

From: owner-aeroelectric-list-server(at)matronics.com [mailto:owner-aeroelectric-list-server(at)matronics.com] On Behalf Of Robert L. Nuckolls, III

 Sent: Wednesday, August 12, 2009 5:03 PM

 To: aeroelectric-list(at)matronics.com

 Subject: Re: AeroElectric-List: Re: Calibrating fuel qty gauges  

At 11:32 AM 8/12/2009, you wrote:

 

   

Bob,

 These fuel sensors are a great idea.  I wish I had seen them while building.  I could have installed three of them in the wing root of each tank - one at "wing root full," one at "wing root half," and one at "wing root" empty (maybe two gal remaining).  They would have been easy to calibrate and label on the panel.  Then I would know exactly the fuel remaining at those levels.

 The Princeton Capacitance Sensors I bought and connected to the AF-3400 EM do not work.  I've calibrated them 7 times and they still fluctuate between full and 8 gallons when the tanks are full and fluctuate wildly when less than full.  Perhaps I've done something wrong in the calibration - I know most errors are installation or operator errors - but, I tried to follow the AF-3400 instructions accurately.

 Anyway, I may try to retro fit the Gem sensors.  



   I'm sorry to hear that the capacity sensors are

   not performing for you. I presume you've already

   had discussions with the factory. These SHOULD be

   pretty stable. There are design issues with respect

   to variable dielectric constant of the fuel. But

   this is a calibration error, not a dynamic level

   sensing problem.

 

   I've been fiddling with a processor based capacity

   gaging amplifier for a TC application. Having a

   micro-controller in the system opens a lot of interesting

   doors including calibrating to the as-installed

   sensor and tank combination and compensating for

   temperature and dielectric constant as well.

 

   Depending on what I learn with this program, I may

   have a similarly agile capacity fuel gage amplifier

   product to offer. However, even if our latest-n-greatest

   gage makes it to production, it will still be augmented

   with electro-optic, dip-sticks for absolute low-liquid

   warning. I did the first such sensors to find their

   way onto Beech products about 1980.

 

 http://www.electromech.com/liquidlevel3RED.html

 

   They've now been produced in dozens of configurations

   and tens of thousands of fielded product. One of

   my more prolific brainstorms.

 

 

     

       Bob . . .

 

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

        ( . . .  a long habit of not thinking   )

        ( a thing wrong, gives it a superficial )

        ( appearance of being right . . .       )

        (                                       )

        (                  -Thomas Paine 1776-  )

         ---------------------------------------   	  Quote: 	
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mprather(at)spro.net
Guest

Posted: Wed Aug 12, 2009 3:48 pm Post subject: Calibrating fuel qty gauges

Seems like sloshing can be dealt with either/both mechanically or/and

electrically:



 - A restriction or a baffle can be used to slow the flow of fuel into and

out of the tube(s).  I'd be slightly surprised if the manufacturer didn't

include this.



 - A low pass filter can be used to average and damp the display in

response to the raw input from the sensor.  Again, I'd be slightly

surprised if the manufacturer didn't include this.

Regards,



Matt-



 	  Quote: 	
		   I have the Princeton capacitance sensors in my Lancair.  I have not yet

 calbrated them, but I would be very shocked if the fuel slosh didn’t cause

 a

 lot of errors.  The sensors are about 6 feet long and must be no more than

 20 degrees off of horizontal.  Fuel sloshing would move a great distance

 up

 and down the tubes.  I have them in there because FAA says I need a fuel

 guage.  I will check the level visually before each flight and refill when

 I

 should be at ¼ to ½ tank.  Reguardless of what the fuel gage says!



 Bill B



   _____



 From: owner-aeroelectric-list-server(at)matronics.com

 [mailto:owner-aeroelectric-list-server(at)matronics.com] On Behalf Of Robert

 L.

 Nuckolls, III

 Sent: Wednesday, August 12, 2009 5:03 PM

 To: aeroelectric-list(at)matronics.com

 Subject: Re: Re: Calibrating fuel qty gauges



 At 11:32 AM 8/12/2009, you wrote:



 Bob,

 These fuel sensors are a great idea.  I wish I had seen them while

 building.

 I could have installed three of them in the wing root of each tank - one

 at

 "wing root full," one at "wing root half," and one at "wing root" empty

 (maybe two gal remaining).  They would have been easy to calibrate and

 label

 on the panel.  Then I would know exactly the fuel remaining at those

 levels.

 The Princeton Capacitance Sensors I bought and connected to the AF-3400 EM

 do not work.  I've calibrated them 7 times and they still fluctuate

 between

 full and 8 gallons when the tanks are full and fluctuate wildly when less

 than full.  Perhaps I've done something wrong in the calibration - I know

 most errors are installation or operator errors - but, I tried to follow

 the

 AF-3400 instructions accurately.

 Anyway, I may try to retro fit the Gem sensors.

   I'm sorry to hear that the capacity sensors are

   not performing for you. I presume you've already

   had discussions with the factory. These SHOULD be

   pretty stable. There are design issues with respect

   to variable dielectric constant of the fuel. But

   this is a calibration error, not a dynamic level

   sensing problem.



   I've been fiddling with a processor based capacity

   gaging amplifier for a TC application. Having a

   micro-controller in the system opens a lot of interesting

   doors including calibrating to the as-installed

   sensor and tank combination and compensating for

   temperature and dielectric constant as well.



   Depending on what I learn with this program, I may

   have a similarly agile capacity fuel gage amplifier

   product to offer. However, even if our latest-n-greatest

   gage makes it to production, it will still be augmented

   with electro-optic, dip-sticks for absolute low-liquid

   warning. I did the first such sensors to find their

   way onto Beech products about 1980.



 http://www.electromech.com/liquidlevel3RED.html



   They've now been produced in dozens of configurations

   and tens of thousands of fielded product. One of

   my more prolific brainstorms.





        Bob . . .



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

        ( . . .  a long habit of not thinking   )

        ( a thing wrong, gives it a superficial )

        ( appearance of being right . . .       )

        (                                       )

        (                  -Thomas Paine 1776-  )

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

echristley(at)nc.rr.com
Guest

Posted: Thu Aug 13, 2009 6:16 am Post subject: Calibrating fuel qty gauges

Matt Prather wrote:

 	  Quote: 	
		   



 Seems like sloshing can be dealt with either/both mechanically or/and

 electrically:



  - A restriction or a baffle can be used to slow the flow of fuel into and

 out of the tube(s).  I'd be slightly surprised if the manufacturer didn't

 include this.



  - A low pass filter can be used to average and damp the display in

 response to the raw input from the sensor.  Again, I'd be slightly

 surprised if the manufacturer didn't include this.



   


	


And the sensor should be located near the center of the tank putting it 

in the middle of where the sloshing "see-saws".



-- 

Ernest Christley, President

Ernest(at)TechnicalTakedown.com



TechnicalTakedown, LLC

www.TechnicalTakedown.com

101 Steep Bank Dr.

Cary, NC  27518

(919) 741-9397

nuckolls.bob(at)aeroelect
Guest

Posted: Thu Aug 13, 2009 6:24 am Post subject: Calibrating fuel qty gauges

Seems like sloshing can be dealt with either/both mechanically or/and

electrically:



  - A restriction or a baffle can be used to slow the flow of fuel into and

out of the tube(s).  I'd be slightly surprised if the manufacturer didn't

include this.



    Me too. Over the years I've seen both mechanical and

    electrical approaches to slosh management. Long sensors

    can be mounted inside a tube that has a tiny hole at

    each end to restrict rate of flow into and out of the

    tube. The sensor he described may already have such

    restrictions.



    On the single engine Cessna's about '64 we looked at

    "lubricating" the pivots on the fuel gages (automotive

    moving magnets driven by rheostats with swing-arm-floats)

    with 30,000 centistoke silicone oil. The smallest droplet

    of this oil injected to the pivot bearing attenuated

    sloshing response to a very low value.



  - A low pass filter can be used to average and damp the display in

response to the raw input from the sensor.  Again, I'd be slightly

surprised if the manufacturer didn't include this.



    Yeah, the one I'm working with now filters the slosh

    in software. The guys are playing with several filtering

    philosophies. The most attractive is a simple running

    average of 200 readings taken 10 times a second.



    The B52 had capacity fuel gages in it when I was

    working on them in '61. They were vacuum tube amplifier

    driven servo motors that kept an LRC bridge balanced.

    The servo motor also drove a potentiometer that produced

    the output signal for the panel instrument. I recall

    the instructor stating that the servo motor was

    deliberately designed to be slow. Full scale response

    time was on the order of 1 to 2 minutes. Exceedingly

    unresponsive to slosh.



    Anyone who has flown an old Cessna with the mechanical

    swing-arm-float indicators in the wing roots or a J-3

    with a wire on a cork will understand the seeds from

    which more convenient and accurate fuel gaging systems

    were grown. Seems the only time those gages were accurately

    readable was on the ground.



    The first moves for embarking upon a new

    design for a fuel gaging system is to get the HISTORY.

    An excellent source are patents. Freepatentsonline.com is

    but one of several libraries of ideas good, bad, and

    ugly that go back over 100 years. I've looked at

    hundreds of such patents on liquid level measurement.

    There are no excuses these days for not meeting design

    goals that move the best-we-know-how-to-do forward. There's

    also no excuse for any system designed in the past 40

    years not to provide a level of functionality commensurate

    with what they cost.

        Bob . . .



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

        ( . . .  a long habit of not thinking   )

        ( a thing wrong, gives it a superficial )

        ( appearance of being right . . .       )

        (                                       )

        (                  -Thomas Paine 1776-  )

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

nuckolls.bob(at)aeroelect
Guest

Posted: Thu Aug 13, 2009 6:55 am Post subject: Calibrating fuel qty gauges

 	  Quote: 	
		    IMO, fixed point sensors are not workable in a plane. An analog 

 design is required. The best solution I have seen and I use is a 

 simple boat turbine flow meter made by Northstar. The gauge reads 

 gal/hour, gal remaining, and gal used. It has to be updated each 

 time fuel is added.


	


    This is an ambitious design goal . . . and technologically

    feasible. I'll suggest that there are good reasons NOT to

    have such accuracy displayed on the panel of an airplane.



    Folks who learned about living comfortably in the world

    of airplanes discovered pretty quickly that oldest pilots

    were not so bold as to flight-plan with a dependency upon

    their "fudge factors". I.e. fuel reserves. The reasons for

    this are pretty clear. It's difficult to anticipate your

    fuel needs with accuracy. Winds can affect speed over

    the ground. Weather can affect routing changes. Conditions

    at the destination airport can force delays or an alternate, etc.



    The finely tuned fuel level indication system encourages

    the pilot to exploit that knowledge. The pilot's willingness

    to fly closer "to the edge" becomes increasingly comfortable.

    The prudent pilot never launches into an extended operation

    with less than KNOWN amounts of fuel aboard. Up to the tab,

    slot-in-the-tab, or better yet . . . full. From time of take

    of, the pilot with NO fuel gage is acutely aware of the fact

    that so many hours from now, the engine stops. He's also

    aware of the variables that affect accuracy of that

    calculation. Hence, that thing called "reserve" fuel is

    a both a PHYSICAL and PSYCHOLOGICAL buffer for hitting the

    "wall of variables" in flight planning.



    Fitting an airplane with a fuel gage that accurately

    depicts engine stopping to the minute is a psychological

    trap that WILL eventually catch some pilot and his/her

    passengers. I'm not suggesting that anyone, including

    yourself, cannot prudently use accurate fuel quantity

    measurement to good advantage . . . as long as you

    continue to recognize that the value of that accuracy

    becomes less useful as larger and less predictable

    conditions pile onto your error budget.



 	  Quote: 	
		    It is accurate after the initial fill. One still has to remember 

 how many gallons is safe when the tank gets low. Many homebuilts 

 use this product with success. No issues with slosh.



I am trying the CruzPro gauge for my truck which allows many cal 

points and the gauge reads the same stuff as the Northstar. This 

setup uses the stock resistance gauge and is still inaccurate due to 

slosh and tilt. However there is some damping in the float mechanism.


	


    All true. But never diminish the ideas that described

    the WHOLE flight system and the environment in which

    it operates. Even if you can absolu8tely depend on

    the accuracy of a fuel quantity measurement system,

    be alert and cognizant of both the values and risks

    associated with KNOWING that number when there

    are other more restrictive conditions that you

    cannot know or predict with accuracy.



    This is why our fuel gaging system will include both

    a reasonably accurate level indication system combined

    with "dip stick" accurate level warnings. The published

    advise for using this system will suggest that no matter

    how accurate the indication, no matter how well your

    planning conforms to actual conditions, when that low

    fuel warning light comes on you need to be 100% assured

    of comfortable return to earth whether at your airport

    of intended destination or not.



    There are situations where the guy flying comfortably

    with a wire on a cork is perhaps better off than the

    guy who believes there is exploitable value in knowing

    fuel quantity remaining down to the nearest cubic

    centimeter. He may make more fuel stops but shucks, those

    takeoffs and near greaser landings are so much fun.

    You get to meet more friendly FBO line boys too.



    Bob . . .

thorps18(at)gmail.com
Guest

Posted: Thu Aug 13, 2009 7:13 am Post subject: Calibrating fuel qty gauges

Here's the low fuel sensor I'm using.



http://www.pillarpointelectronics.com/



On Mon, Aug 10, 2009 at 8:27 AM, Robert L. Nuckolls, III <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)> wrote:

  	  Quote: 	
		    At 04:29 AM 8/10/2009, you wrote:

  	  Quote: 	
		  --> AeroElectric-List message posted by: "Thruster87" <alania(at)optusnet.com.au (alania(at)optusnet.com.au)>



 How do you calibrate fuel qty using  a 10 - 75 ohm sender unit with a 0 -90 ohm fuel gauge? in other words what's the best why to get the gauges to read accurately near empty,  which is more important then FULL. Thanks 	


     The floats-on-a-swing-arm senders are

     a legacy product from cars and other

     vehicles that go back a very long way.



     Making these things really accurate in more\

     than one place is a bit fussy.



     Years ago, we crafted an electronic signal

     conditioning board for the Bonanzas and Barons

     that allowed dead-on calibration of empty

     and full. All other readings across the scale

     simply fell where where the physics of the

     sender dictates. The physics of these devices

     are affected mildly by linearity of the wire

     wound sensor resistor (usually within 5% of

     true) but a whole lot by trigonometry of

     the swing arm and tank geometry.



     But as you've already recognized, the one

     level you really want to be accurate is

     the empty point. For this you can do some

     things with series calibration resistors

     and/or bending the float arm on the sender.

     This CAN be a tedious, trial-by-error activity.



     If it were my airplane, I'd probably craft

     a microprocessor based signal conditioner

     that would allow me to take readings at 5%

     increments from empty to full and generate

     a lookup table that converts as-installed

     sender (transducer) readings into real

     numbers. The BEST way to watch full levels

     is with installation of a "dip stick" style

     sensor at the low fuel warning level (generally

     1/4 to 1/3 tank). Consider devices like this:



 [img]cid:.0[/img]

     One of these stuck through the tank wall at

     the warning level will light a lamp on the

     panel at the desired fuel quantity with

     no risk for drift of calibration. See:



  http://www.gemssensors.com/content.aspx?id=282



     This is the no-brainer, dead-nuts accurate

     low liquid lever sensing method I know of.

     Capacity fuel gages with processor augmentation

     are also easy to calibrate . . . but I think

     I could get by with no active fuel gaging

     other than a set of optical level detectors

     cited above.



 

        Bob . . .



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

        ( . . .  a long habit of not thinking   )

        ( a thing wrong, gives it a superficial )

        ( appearance of being right . . .       )

        (                                       )

        (                  -Thomas Paine 1776-  )

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

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ianxbrown

Joined: 16 May 2009
Posts: 80

Posted: Thu Aug 13, 2009 7:23 am Post subject: Calibrating fuel qty gauges

My EI FL-2CA fuel gauges come with the ability to select the "rate of update" which solves one of the problems, but isn't the REAL problem that one shouldn't be playing down in the "low fuel minefield" any way?   Why worry about how to tell exactly when you're going to run out of fuel?  I'd rather have really accurate gauges down to a quarter tank, and then who cares, it's time to fill up.

 

 An accurate stick with marks on it, and confidence in fuel consumption rates, IMHO, are much more important than measuring fuel quantities near empty, unless you have no access at all to a physical measurement of fuel levels.

 

 Ian Brown

 Bromont, QC

 

 On Thu, 2009-08-13 at 09:23 -0500, Robert L. Nuckolls, III wrote:  	  Quote: 	
		    	  Quote: 	
		  

--> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)>



--> AeroElectric-List message posted by: "Matt Prather" <mprather(at)spro.net (mprather(at)spro.net)>



Seems like sloshing can be dealt with either/both mechanically or/and

electrically:



  - A restriction or a baffle can be used to slow the flow of fuel into and

out of the tube(s).  I'd be slightly surprised if the manufacturer didn't

include this.



    Me too. Over the years I've seen both mechanical and

    electrical approaches to slosh management. Long sensors

    can be mounted inside a tube that has a tiny hole at

    each end to restrict rate of flow into and out of the

    tube. The sensor he described may already have such

    restrictions.



    On the single engine Cessna's about '64 we looked at

    "lubricating" the pivots on the fuel gages (automotive

    moving magnets driven by rheostats with swing-arm-floats)

    with 30,000 centistoke silicone oil. The smallest droplet

    of this oil injected to the pivot bearing attenuated

    sloshing response to a very low value.



  - A low pass filter can be used to average and damp the display in

response to the raw input from the sensor.  Again, I'd be slightly

surprised if the manufacturer didn't include this.



    Yeah, the one I'm working with now filters the slosh

    in software. The guys are playing with several filtering

    philosophies. The most attractive is a simple running

    average of 200 readings taken 10 times a second.



    The B52 had capacity fuel gages in it when I was

    working on them in '61. They were vacuum tube amplifier

    driven servo motors that kept an LRC bridge balanced.

    The servo motor also drove a potentiometer that produced

    the output signal for the panel instrument. I recall

    the instructor stating that the servo motor was

    deliberately designed to be slow. Full scale response

    time was on the order of 1 to 2 minutes. Exceedingly

    unresponsive to slosh.



    Anyone who has flown an old Cessna with the mechanical

    swing-arm-float indicators in the wing roots or a J-3

    with a wire on a cork will understand the seeds from

    which more convenient and accurate fuel gaging systems

    were grown. Seems the only time those gages were accurately

    readable was on the ground.



    The first moves for embarking upon a new

    design for a fuel gaging system is to get the HISTORY.

    An excellent source are patents. Freepatentsonline.com is

    but one of several libraries of ideas good, bad, and

    ugly that go back over 100 years. I've looked at

    hundreds of such patents on liquid level measurement.

    There are no excuses these days for not meeting design

    goals that move the best-we-know-how-to-do forward. There's

    also no excuse for any system designed in the past 40

    years not to provide a level of functionality commensurate

    with what they cost.

        Bob . . .



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

        ( . . .  a long habit of not thinking   )

        ( a thing wrong, gives it a superficial )

        ( appearance of being right . . .       )

        (                                       )

        (                  -Thomas Paine 1776-  )

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

echristley(at)nc.rr.com
Guest

Posted: Thu Aug 13, 2009 8:14 am Post subject: Calibrating fuel qty gauges

Robert L. Nuckolls, III wrote:

 	  Quote: 	
		      Anyone who has flown an old Cessna with the mechanical

    swing-arm-float indicators in the wing roots or a J-3

    with a wire on a cork will understand the seeds from

    which more convenient and accurate fuel gaging systems

    were grown. Seems the only time those gages were accurately

    readable was on the ground.


	


Maybe that is one more thing Heinlein should have added to his list of 

things a man should know how to do:  tell how much fuel is in a tank by 

how wildly the indicator is bouncing.



First rule:  If you are so worried about the fuel remaining that you 

need to know within a tenth of a gallon, you need to be punching the 

"nearest" button on your GPS...not stretching your glide to the destination.



Second rule:  If the guage is bouncing all over the place, you either 

have fuel or the guage is broken.  One of the first things we learned in 

my high-school chemistry class was how to interpret a bouncing arm on a 

triple-beam scale.  If it bounced equally to both side of the center 

mark, then it was balanced.  With the fuel level indicator, if it is 

bouncing around the top, proceed.  If it bounces around the bottom, 

punch "nearest" of call the fuel truck before launching.



Third rule:  The FAA minimums are minimums, not a GOAL.



-- 

Ernest Christley, President

Ernest(at)TechnicalTakedown.com



TechnicalTakedown, LLC

www.TechnicalTakedown.com

101 Steep Bank Dr.

Cary, NC  27518

(919) 741-9397

BobsV35B(at)aol.com
Guest

Posted: Thu Aug 13, 2009 9:17 am Post subject: Calibrating fuel qty gauges

Just out of curiosity, What ever happened to "Ernest is a Nerd?" He sure  seemed like a very nice person?

  

 Happy Skies,

  

 Old Bob

 Definitely Do Not Archive<G>

  

  In a message dated 8/13/2009 11:15:33 A.M. Central Daylight Time,  echristley(at)nc.rr.com writes:

  	  Quote: 	
		  -->    AeroElectric-List message posted by: Ernest Christley    <echristley(at)nc.rr.com>



Robert L. Nuckolls, III    wrote:

 	  Quote: 	
		      Anyone who has flown an old Cessna with the    mechanical

    swing-arm-float indicators in the wing roots    or a J-3

    with a wire on a cork will understand the seeds    from

    which more convenient and accurate fuel gaging    systems

    were grown. Seems the only time those gages were    accurately

    readable was on the ground.


	


Maybe that    is one more thing Heinlein should have added to his list of 

things a man    should know how to do:  tell how much fuel is in a tank by 

how wildly    the indicator is bouncing.



First rule:  If you are so worried    about the fuel remaining that you 

need to know within a tenth of a gallon,    you need to be punching the 

"nearest" button on your GPS...not stretching    your glide to the destination.



Second rule:  If the guage is    bouncing all over the place, you either 

have fuel or the guage is    broken.  One of the first things we learned in 

my high-school    chemistry class was how to interpret a bouncing arm on a 

triple-beam    scale.  If it bounced equally to both side of the center 

mark, then    it was balanced.  With the fuel level indicator, if it is 

bouncing    around the top, proceed.  If it bounces around the bottom, 

punch    "nearest" of call the fuel truck before launching.



Third rule:     The FAA minimums are minimums, not a GOAL.



-- 

Ernest Christley,    President

Ernest(at)TechnicalTakedown.com



TechnicalTakedown,    LLC

www.TechnicalTakedown.com

101 Steep Bank Dr.

Cary, NC     27518

(919)  ========================;  = Use   utilities  Day  ================================================               - MATRONICS WEB FORUMS  ================================================             - List Contribution Web Site  sp;                             ===================================================



	


 

  [quote][b]

BobsV35B(at)aol.com
Guest

Posted: Thu Aug 13, 2009 9:50 am Post subject: Calibrating fuel qty gauges

Good Afternoon 'Lectric Bob,

  

 This may be just an exercise in semantics, but I do disagree with the  philosophy I think you are espousing. 

  

 There is nothing wrong with planning on arriving at a safe landing spot  with ten to fifteen minutes of fuel as long as you are confident you will be at  that spot at the appointed time. 

  

 To say we should always have something beyond what is required is too broad  for my liking. On those few occasions when I had the pleasure of flying a T-38,  we landed every time with "Bingo" fuel. In that airplane, Bingo fuel was a bit  less than twenty minutes worth. Good enough for one full power go around and not  much more. 

  

 We pay a LOT of money for every pound of payload we put in our flying  machines. I think it is very rational to reduce the amount of fuel down to what  is required for the mission at hand. My cross country flyer has tip tanks and it  can fairly easily fly twelve hours with full tanks. My planning for that  airplane often has me arriving with less than one hours worth of fuel. If I was  able to be as certain of landing field availability as I was when flying the  T-38 and as confident as I was of the accuracy of the fuel gauges, I would not  hesitate to fly my long ranger down to a Bingo fuel of twenty minutes.

  

 Back when I was doing sling work with a helicopter, we added fuel for each  trip lifting air conditioners to a roof top. Carrying no more than about five  minutes of reserve fuel, we managed to get more air conditioners per day up on  top of those roofs. The reserve fuel planned on should be based on the accuracy  of the fuel indicating system and the reliability of the landing estimate 

  

 To do otherwise is as foolish as asking that every airplane be fitted with  four engines just in case one of them happens to quit. We have decided that a  good single engine provides adequate safety for many of us. The same thing goes  for carrying extra fuel. Every ounce we carry that is not needed for the task at  hand costs us money and $time$.

  

 I prefer to know how much fuel is on board and how much I want when I  land.

  

 Just my thoughts

  

 Happy Skies,

  

 Old Bob

 Stearman N3977A

 Downers Grove, Illinois

 LL22

  

  In a message dated 8/13/2009 9:56:02 A.M. Central Daylight Time,  nuckolls.bob(at)aeroelectric.com writes:

  	  Quote: 	
		  -->    AeroElectric-List message posted by: "Robert L. Nuckolls, III"    <nuckolls.bob(at)aeroelectric.com>

 	  Quote: 	
		    IMO, fixed point    sensors are not workable in a plane. An analog 

 design is required.    The best solution I have seen and I use is a 

 simple boat turbine flow    meter made by Northstar. The gauge reads 

 gal/hour, gal remaining, and    gal used. It has to be updated each 

 time fuel is added.


	


       This is an ambitious design goal . . . and technologically

       feasible. I'll suggest that there are good reasons NOT to

       have such accuracy displayed on the panel of an airplane.



       Folks who learned about living comfortably in the world

       of airplanes discovered pretty quickly that oldest pilots

       were not so bold as to flight-plan with a dependency upon

       their "fudge factors". I.e. fuel reserves. The reasons for

       this are pretty clear. It's difficult to anticipate your

       fuel needs with accuracy. Winds can affect speed over

       the ground. Weather can affect routing changes. Conditions

    at    the destination airport can force delays or an alternate, etc.



       The finely tuned fuel level indication system encourages

       the pilot to exploit that knowledge. The pilot's willingness

       to fly closer "to the edge" becomes increasingly comfortable.

       The prudent pilot never launches into an extended operation

       with less than KNOWN amounts of fuel aboard. Up to the tab,

       slot-in-the-tab, or better yet . . . full. From time of take

       of, the pilot with NO fuel gage is acutely aware of the fact

       that so many hours from now, the engine stops. He's also

       aware of the variables that affect accuracy of that

       calculation. Hence, that thing called "reserve" fuel is

    a    both a PHYSICAL and PSYCHOLOGICAL buffer for hitting the

       "wall of variables" in flight planning.



    Fitting an    airplane with a fuel gage that accurately

    depicts engine    stopping to the minute is a psychological

    trap that WILL    eventually catch some pilot and his/her

    passengers. I'm not    suggesting that anyone, including

    yourself, cannot prudently    use accurate fuel quantity

    measurement to good advantage . .    . as long as you

    continue to recognize that the value of that    accuracy

    becomes less useful as larger and less    predictable

    conditions pile onto your error    budget.



 	  Quote: 	
		    It is accurate after the initial fill. One still has    to remember 

 how many gallons is safe when the tank gets low. Many    homebuilts 

 use this product with success. No issues with    slosh.



I am trying the CruzPro gauge for my truck which allows    many cal 

points and the gauge reads the same stuff as the Northstar.    This 

setup uses the stock resistance gauge and is still inaccurate due    to 

slosh and tilt. However there is some damping in the float    mechanism.


	


    All true. But never diminish the ideas that    described

    the WHOLE flight system and the environment in    which

    it operates. Even if you can absolu8tely depend    on

    the accuracy of a fuel quantity measurement    system,

    be alert and cognizant of both the values and    risks

    associated with KNOWING that number when    there

    are other more restrictive conditions that    you

    cannot know or predict with accuracy.



       This is why our fuel gaging system will include both

    a    reasonably accurate level indication system combined

    with    "dip stick" accurate level warnings. The published

    advise for    using this system will suggest that no matter

    how accurate    the indication, no matter how well your

    planning conforms to    actual conditions, when that low

    fuel warning light comes on    you need to be 100% assured

    of comfortable return to earth    whether at your airport

    of intended destination or    not.



    There are situations where the guy flying    comfortably

    with a wire on a cork is perhaps better off than    the

    guy who believes there is exploitable value in    knowing

    fuel quantity remaining down to the nearest    cubic

    centimeter. He may make more fuel stops but shucks,    those

    takeoffs and near greaser landings are so much    fun.

    You get to meet more friendly FBO line boys    too.



    Bob . . .  ========================= Use   utilities  Day  ================================================               - MATRONICS WEB FORUMS  ================================================             - List Contribution Web Site  sp;                             ===================================================



	


 

  [quote][b]

DanFM01(at)butter.toast.n
Guest

Posted: Thu Aug 13, 2009 10:22 am Post subject: Calibrating fuel qty gauges

On Thu, 2009-08-13 at 13:30 -0400, BobsV35B(at)aol.com wrote:

 	  Quote: 	
		   Good Afternoon 'Lectric Bob,

  

 This may be just an exercise in semantics, but I do disagree with the

 philosophy I think you are espousing. 

  

 There is nothing wrong with planning on arriving at a safe landing

 spot with ten to fifteen minutes of fuel as long as you are confident

 you will be at that spot at the appointed time. 

  


	


What if something happens you didn't plan on -- such as an accident

blocking the runway 10 minutes before your arrival or unforecast thick

fog etc.  Prudent planning includes adequate fuel to fly to an

alternate.

 	  Quote:

ianxbrown

Joined: 16 May 2009
Posts: 80

Posted: Thu Aug 13, 2009 11:04 am Post subject: Calibrating fuel qty gauges

It's a significantly more serious exercise than one of semantics.  We're talking about life-saving behaviours like not PLANNING to run out of gas ten minutes from now, whilst still flying!!!!!!

 

 Two days ago I returned to the circuit and "some idiot" decided to go ahead and encroach the runway without a radio call, despite my repeated calls on downwind, base, final, and "overshooting".   He apologized that his radio reception wasn't very good, but then apparently neither was his eyesight.  He then exited our right hand circuit UNDER me, at five hundred feet,  while I was still in the overshoot.  My circuit took more than ten minutes, and I had PLENTY fuel for the go-around.

 

 Old Ian (and planning to get older).

 

 On Thu, 2009-08-13 at 13:30 -0400, BobsV35B(at)aol.com wrote:  	  Quote: 	
		       Good Afternoon 'Lectric Bob,             This may be just an exercise in semantics, but I do disagree with the philosophy I think you are espousing.              There is nothing wrong with planning on arriving at a safe landing spot with ten to fifteen minutes of fuel as long as you are confident you will be at that spot at the appointed time.              To say we should always have something beyond what is required is too broad for my liking. On those few occasions when I had the pleasure of flying a T-38, we landed every time with "Bingo" fuel. In that airplane, Bingo fuel was a bit less than twenty minutes worth. Good enough for one full power go around and not much more.              We pay a LOT of money for every pound of payload we put in our flying machines. I think it is very rational to reduce the amount of fuel down to what is required for the mission at hand. My cross country flyer has tip tanks and it can fairly easily fly twelve hours with full tanks. My planning for that airplane often has me arriving with less than one hours worth of fuel. If I was able to be as certain of landing field availability as I was when flying the T-38 and as confident as I was of the accuracy of the fuel gauges, I would not hesitate to fly my long ranger down to a Bingo fuel of twenty minutes.             Back when I was doing sling work with a helicopter, we added fuel for each trip lifting air conditioners to a roof top. Carrying no more than about five minutes of reserve fuel, we managed to get more air conditioners per day up on top of those roofs. The reserve fuel planned on should be based on the accuracy of the fuel indicating system and the reliability of the landing estimate              To do otherwise is as foolish as asking that every airplane be fitted with four engines just in case one of them happens to quit. We have decided that a good single engine provides adequate safety for many of us. The same thing goes for carrying extra fuel. Every ounce we carry that is not needed for the task at hand costs us money and $time$.             I prefer to know how much fuel is on board and how much I want when I land.             Just my thoughts             Happy Skies,             Old Bob      Stearman N3977A      Downers Grove, Illinois      LL22             In a message dated 8/13/2009 9:56:02 A.M. Central Daylight Time, nuckolls.bob(at)aeroelectric.com writes:       	  Quote: 	
		           --> AeroElectric-List message posted by: "Robert L. Nuckolls, III" <nuckolls.bob(at)aeroelectric.com>

         

         

         >  IMO, fixed point sensors are not workable in a plane. An analog 

         > design is required. The best solution I have seen and I use is a 

         > simple boat turbine flow meter made by Northstar. The gauge reads 

         > gal/hour, gal remaining, and gal used. It has to be updated each 

         > time fuel is added.

         

             This is an ambitious design goal . . . and technologically

             feasible. I'll suggest that there are good reasons NOT to

             have such accuracy displayed on the panel of an airplane.

         

             Folks who learned about living comfortably in the world

             of airplanes discovered pretty quickly that oldest pilots

             were not so bold as to flight-plan with a dependency upon

             their "fudge factors". I.e. fuel reserves. The reasons for

             this are pretty clear. It's difficult to anticipate your

             fuel needs with accuracy. Winds can affect speed over

             the ground. Weather can affect routing changes. Conditions

             at the destination airport can force delays or an alternate, etc.

         

             The finely tuned fuel level indication system encourages

             the pilot to exploit that knowledge. The pilot's willingness

             to fly closer "to the edge" becomes increasingly comfortable.

             The prudent pilot never launches into an extended operation

             with less than KNOWN amounts of fuel aboard. Up to the tab,

             slot-in-the-tab, or better yet . . . full. From time of take

             of, the pilot with NO fuel gage is acutely aware of the fact

             that so many hours from now, the engine stops. He's also

             aware of the variables that affect accuracy of that

             calculation. Hence, that thing called "reserve" fuel is

             a both a PHYSICAL and PSYCHOLOGICAL buffer for hitting the

             "wall of variables" in flight planning.

         

             Fitting an airplane with a fuel gage that accurately

             depicts engine stopping to the minute is a psychological

             trap that WILL eventually catch some pilot and his/her

             passengers. I'm not suggesting that anyone, including

             yourself, cannot prudently use accurate fuel quantity

             measurement to good advantage . . . as long as you

             continue to recognize that the value of that accuracy

             becomes less useful as larger and less predictable

             conditions pile onto your error budget.

         

         >  It is accurate after the initial fill. One still has to remember 

         > how many gallons is safe when the tank gets low. Many homebuilts 

         > use this product with success. No issues with slosh.

         >

         >I am trying the CruzPro gauge for my truck which allows many cal 

         >points and the gauge reads the same stuff as the Northstar. This 

         >setup uses the stock resistance gauge and is still inaccurate due to 

         >slosh and tilt. However there is some damping in the float mechanism.

         

             All true. But never diminish the ideas that described

             the WHOLE flight system and the environment in which

             it operates. Even if you can absolu8tely depend on

             the accuracy of a fuel quantity measurement system,

             be alert and cognizant of both the values and risks

             associated with KNOWING that number when there

             are other more restrictive conditions that you

             cannot know or predict with accuracy.

         

             This is why our fuel gaging system will include both

             a reasonably accurate level indication system combined

             with "dip stick" accurate level warnings. The published

             advise for using this system will suggest that no matter

             how accurate the indication, no matter how well your

             planning conforms to actual conditions, when that low

             fuel warning light comes on you need to be 100% assured

             of comfortable return to earth whether at your airport

             of intended destination or not.

         

             There are situations where the guy flying comfortably

             with a wire on a cork is perhaps better off than the

             guy who believes there is exploitable value in knowing

             fuel quantity remaining down to the nearest cubic

             centimeter. He may make more fuel stops but shucks, those

             takeoffs and near greaser landings are so much fun.

             You get to meet more friendly FBO line boys too.

         

             Bob . . . ========================= Use utilities Day ================================================              - MATRONICS WEB FORUMS ================================================            - List Contribution Web Site sp;                         ===================================================

         

         

         

     	
      

          	  Quote:

BobsV35B(at)aol.com
Guest

Posted: Thu Aug 13, 2009 11:22 am Post subject: Calibrating fuel qty gauges

Good Afternoon Dan,

  

 The availability of alternate landing space is absolutely part of the  computations needed. 

  

 When we were flying the T-38, we had the salt runways of Muroc available.  When we were lifting air conditioners, there were alternate spots in the parking  lot in which we could land. Worst case, we could stay on the roof and carry a  gas of can up to the helicopter.

  

 Evaluating the reliability of the landing site is as big a part of fuel  planning as is any other factor. Once again. proper planning is key.

  

 There are times when I want four hours worth of fuel when I am on final  approach.

  

 I do NOT like to make wild guesses as to what will be needed. I plan for  what is likely to happen. Both expected and variable conditions must be  considered.

  

 As Always, It All Depends!

  

 Happy Skies

  

 Old Bob

 AKA

 Bob Siegfried

 628 west 86th Street

 Downers Grove, Illinois

 LL22

 Stearman N3977A

  

  In a message dated 8/13/2009 1:23:19 P.M. Central Daylight Time,  DanFM01(at)butter.toast.net writes:

  	  Quote: 	
		  -->    AeroElectric-List message posted by: Dan Morrow    <DanFM01(at)butter.toast.net>



On Thu, 2009-08-13 at 13:30 -0400,    BobsV35B(at)aol.com wrote:

 	  Quote: 	
		   Good Afternoon 'Lectric Bob,

     

 This may be just an exercise in semantics, but I do disagree with    the

 philosophy I think you are espousing. 

  

    There is nothing wrong with planning on arriving at a safe landing

    spot with ten to fifteen minutes of fuel as long as you are confident

    you will be at that spot at the appointed time. 

  


	


What if    something happens you didn't plan on -- such as an accident

blocking the    runway 10 minutes before your arrival or unforecast thick

fog etc.     Prudent planning includes adequate fuel to fly to an

alternate.

 	  Quote: 	
		    ========================= Use   utilities  Day  ================================================               - MATRONICS WEB FORUMS  ================================================             - List Contribution Web Site  sp;                             ===================================================


	


	


 

  [quote][b]

BobsV35B(at)aol.com
Guest

Posted: Thu Aug 13, 2009 11:39 am Post subject: Calibrating fuel qty gauges

Good Afternoon Old Ian,

  

 If you are saying you disagree with my philosophy, that is just fine.  

  

 I rarely plan to arrive with only ten minutes of reserve fuel, but there  are conditions where I would be happy to do so. The T-38 flights at Edwards were  just such flights. 

  

 My personal planning at the average multi runway airport is forty-five  minutes. If there is only one runway, I want a close by alternate and fuel to  get there 

  

 It All Depends!

  

 That is more than what the FAA requires, but it is what I like to have.  However, I do NOT wish to arrive anywhere without knowing accurately how much  fuel I do have on board. If I know that amount due to careful timing or by the  trust I have in my fuel gauges, I still want to know the amount, not just  that there is an indeterminate large amount of fuel on board.

  

 You speak quite sarcastically about an airplane that was arriving at "your"  destination and who was not listening to your pronouncements on the radio.

  

 We all must remember that it is still legal for aircraft that have no radio  to be using most airspace in this nation. You may not think that is proper, but  if you are flying in pilot controlled airspace, you should always be aware that  it is quite likely that a NORDO aircraft may be sharing "your" airspace. 

  

 The most likely cause of a NORDO conflict is when you or the pilot of the  other aircraft have made the error of not tuning the correct frequency, flipping  the right audio switch, pressing the wrong mike button or other similar pilot  failures of omission or commission. I know I have made all of those errors at  one time or another. While I try very hard to reduce my errors, I know that I am  human and all of us humans do make mistakes. Not only that, but radios DO  fail.

  

 That is what planning is all about. We plan what we need and how to handle  what we don't expect. Such planning requires careful analysis of the conditions  that prevail and that includes a good idea as to how much fuel we have at any  particular moment. I do not wish to carry somewhere between three to five hours  of fuel when I have no idea which amount of fuel is actually in my flying  machine.

  

 Whether I plan on landing with ten minutes fuel or four hours fuel, I want  to know how much there is and where it is located.

  

 Happy Skies,

  

 Old Bob

 Didn't get that way by making Wild Guesses!

  

  In a message dated 8/13/2009 2:05:48 P.M. Central Daylight Time,  ixb(at)videotron.ca writes:

  	  Quote: 	
		  It's a    significantly more serious exercise than one of semantics.  We're talking    about life-saving behaviours like not PLANNING to run out of gas ten minutes    from now, whilst still flying!!!!!!



Two days ago I returned to the    circuit and "some idiot" decided to go ahead and encroach the runway without a    radio call, despite my repeated calls on downwind, base, final, and    "overshooting".   He apologized that his radio reception wasn't very    good, but then apparently neither was his eyesight.  He then exited our    right hand circuit UNDER me, at five hundred feet,  while I was still in    the overshoot.  My circuit took more than ten minutes, and I had PLENTY    fuel for the go-around.



Old Ian (and planning to get older).



On    Thu, 2009-08-13 at 13:30 -0400, BobsV35B(at)aol.com wrote:     	  Quote: 	
		  Good Afternoon      'Lectric Bob, This may be just an      exercise in semantics, but I do disagree with the philosophy I think you are      espousing. There is nothing      wrong with planning on arriving at a safe landing spot with ten to fifteen      minutes of fuel as long as you are confident you will be at that spot at the      appointed time. To say we should      always have something beyond what is required is too broad for my liking. On      those few occasions when I had the pleasure of flying a T-38, we landed      every time with "Bingo" fuel. In that airplane, Bingo fuel was a bit less      than twenty minutes worth. Good enough for one full power go around and not      much more. We pay a LOT of      money for every pound of payload we put in our flying machines. I think it      is very rational to reduce the amount of fuel down to what is required for      the mission at hand. My cross country flyer has tip tanks and it can fairly      easily fly twelve hours with full tanks. My planning for that airplane often      has me arriving with less than one hours worth of fuel. If I was able to be      as certain of landing field availability as I was when flying the T-38 and      as confident as I was of the accuracy of the fuel gauges, I would not      hesitate to fly my long ranger down to a Bingo fuel of twenty      minutes. Back when I was      doing sling work with a helicopter, we added fuel for each trip lifting air      conditioners to a roof top. Carrying no more than about five minutes of      reserve fuel, we managed to get more air conditioners per day up on top of      those roofs. The reserve fuel planned on should be based on the accuracy of      the fuel indicating system and the reliability of the landing estimate      To do otherwise is      as foolish as asking that every airplane be fitted with four engines just in      case one of them happens to quit. We have decided that a good single engine      provides adequate safety for many of us. The same thing goes for carrying      extra fuel. Every ounce we carry that is not needed for the task at hand      costs us money and $time$. I prefer to know      how much fuel is on board and how much I want when I land.    Just my      thoughts Happy      Skies, Old      Bob Stearman      N3977A Downers Grove,      Illinois LL22    In a message dated      8/13/2009 9:56:02 A.M. Central Daylight Time, nuckolls.bob(at)aeroelectric.com      writes:       	  Quote: 	
		  --> AeroElectric-List        message posted by: "Robert L. Nuckolls, III"        <nuckolls.bob(at)aeroelectric.com>

 	  Quote: 	
		    IMO, fixed point sensors are not        workable in a plane. An analog 

 design is required. The best solution I have seen and I        use is a 

 simple        boat turbine flow meter made by Northstar. The gauge reads        

 gal/hour, gal        remaining, and gal used. It has to be updated each 

 time fuel is        added.


	


           This is an ambitious design goal . . . and        technologically

           feasible. I'll suggest that there are good reasons NOT        to

    have        such accuracy displayed on the panel of an        airplane.



           Folks who learned about living comfortably in the        world

    of        airplanes discovered pretty quickly that oldest        pilots

           were not so bold as to flight-plan with a dependency        upon

    their        "fudge factors". I.e. fuel reserves. The reasons        for

    this        are pretty clear. It's difficult to anticipate your

    fuel needs with accuracy. Winds        can affect speed over

    the ground. Weather can affect routing        changes. Conditions

    at the destination airport can force delays or        an alternate, etc.



    The finely tuned fuel level indication system        encourages

           the pilot to exploit that knowledge. The pilot's        willingness

           to fly closer "to the edge" becomes increasingly        comfortable.

           The prudent pilot never launches into an extended        operation

           with less than KNOWN amounts of fuel aboard. Up to the        tab,

           slot-in-the-tab, or better yet . . . full. From time of        take

    of,        the pilot with NO fuel gage is acutely aware of the        fact

    that        so many hours from now, the engine stops. He's also

    aware of the variables that        affect accuracy of that

    calculation. Hence, that thing called        "reserve" fuel is

           a both a PHYSICAL and PSYCHOLOGICAL buffer for hitting        the

    "wall        of variables" in flight planning.



    Fitting an airplane with a fuel gage that        accurately

           depicts engine stopping to the minute is a        psychological

           trap that WILL eventually catch some pilot and        his/her

           passengers. I'm not suggesting that anyone,        including

           yourself, cannot prudently use accurate fuel        quantity

           measurement to good advantage . . . as long as you

    continue to recognize that the        value of that accuracy

    becomes less useful as larger and less        predictable

           conditions pile onto your error budget.



 	  Quote: 	
		    It is accurate after the initial        fill. One still has to remember 

 how many gallons is safe when the tank gets low. Many        homebuilts 

 use        this product with success. No issues with slosh.



I am trying the CruzPro gauge for my truck which allows        many cal 

points and        the gauge reads the same stuff as the Northstar. This        

setup uses the        stock resistance gauge and is still inaccurate due to        

slosh and tilt.        However there is some damping in the float        mechanism.


	


           All true. But never diminish the ideas that        described

           the WHOLE flight system and the environment in        which

    it        operates. Even if you can absolu8tely depend on

    the accuracy of a fuel quantity        measurement system,

    be alert and cognizant of both the values and        risks

           associated with KNOWING that number when there

    are other more restrictive        conditions that you

    cannot know or predict with        accuracy.



           This is why our fuel gaging system will include        both

    a        reasonably accurate level indication system        combined

           with "dip stick" accurate level warnings. The        published

           advise for using this system will suggest that no        matter

    how        accurate the indication, no matter how well your

    planning conforms to actual        conditions, when that low

    fuel warning light comes on you need to be        100% assured

           of comfortable return to earth whether at your        airport

    of        intended destination or not.



    There are situations where the guy flying        comfortably

           with a wire on a cork is perhaps better off than        the

    guy        who believes there is exploitable value in knowing

    fuel quantity remaining down to        the nearest cubic

           centimeter. He may make more fuel stops but shucks,        those

           takeoffs and near greaser landings are so much fun.

    You get to meet more friendly FBO        line boys too.



    Bob . . . ========================= Use        utilities Day ================================================                     - MATRONICS WEB FORUMS        ================================================                   - List Contribution Web Site sp;                                       ===================================================



	


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