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BobsV35B(at)aol.com
Guest

Posted: Wed Jul 01, 2009 5:41 am Post subject: self weighing our planes

Good Morning David,

  

 Strain gauges do have a lot of capability. For some reason, every time a  proposal is made to use them for a control function, various calibration issues  arise. It will be interesting to see what the brainy guys on the list come up  with.

  

 The idea of having an instantaneous check of weight has been toyed with for  many years. Not sure how long ago it started. However, my first exposure was  just after WWII when tricycle landing gear became common on air carrier  aircraft. Since everyone of the then popular tricycle landing geared airliners  used air/oil hydraulic struts on their landing gear, the  obvious  answer was to measure the change in strut pressure as the  aircraft was being loaded.

  

 The first objection came from those who mentioned air loads. We can't even  get a good static weighing of an airplane unless the weighing is being conducted  in a closed hangar. Even ceiling fans must be shut off because those have been  known to affect a precise weighing. 

  

 Once an engine is started, additional varying loads would be applied that  mess up the weight numbers.

  

 If all those variables are considered, do we really want something that  will tell us we are ten pounds too heavy? Or maybe that our CG is two tenths of  an inch aft of where it should be?  

  

 For safety, I think we would all like to have that information, but only if  it was absolutely guaranteed to be accurate and repeatable information. 

  

 I wish you well in your endeavor and hope that the problems can be solved,  but the powers that be have elected to study the situation quite a bit more  before using it in commercial aviation.

  

 Let us know how it works for you.

  

 Happy Skies,

  

 Old Bob

  

 Downers Grove IL

 LL22

 Stearman N3977A

  

  In a message dated 7/1/2009 6:37:05 A.M. Central Daylight Time,  ainut(at)hiwaay.net writes:

  	  Quote: 	
		  -->    AeroElectric-List message posted by: "David M."    <ainut(at)hiwaay.net>



Does anyone have experience with strain    gauges?  I envision strain 

gauges somewhere on each of the 3 "legs"    of the plane, calibrated 

initially at the empty weight of the plane and    then again at full fuel, 

oil, and etc.  What that would give us is a    constant readout or our 

plane's weight, esp on takeoff.  One could    argue that landing weight 

could be inferred as well while still in the    air.  This should help 

immensely with the (uncommon) problems of    taking off too heavy or (gasp) 

CG being out of range.

I want to try    this on my plane but I have no experience with strain 

gauges.  I'm    thinking of mounting them where the legs meet the fuselage 

for the mains,    and maybe at the movable joint on the front (mine is a 

trike.)

Any    ideas?



David  M.

	


 Make your summer sizzle with fast and easy recipes for the grill.

junk(at)jaredyates.com
Guest

Posted: Wed Jul 01, 2009 6:19 am Post subject: self weighing our planes

I think that some airliners have tried onboard systems, but the shortcoming

is that it is hard to build a system that is sensitive enough to keep the

accuracy where you would want it but yet strong enough to survive the

stresses of landings.  Most big planes have instead moved in the direction

of math calculations with average weights instead.  Those calculations have

a lot of room for error, and yet someone must have decided at some point

that they were still more accurate than strain gauges.  Maybe with a small

plane and feather fingertips for the landings, you could make it work!



--

khorton01(at)rogers.com
Guest

Posted: Wed Jul 01, 2009 10:40 am Post subject: self weighing our planes

On 1 Jul 2009, at 07:32, David M. wrote:



 	  Quote: 	
		   



 Does anyone have experience with strain gauges?  I envision strain  

 gauges somewhere on each of the 3 "legs" of the plane, calibrated  

 initially at the empty weight of the plane and then again at full  

 fuel, oil, and etc.  What that would give us is a constant readout  

 or our plane's weight, esp on takeoff.  One could argue that landing  

 weight could be inferred as well while still in the air.  This  

 should help immensely with the (uncommon) problems of taking off too  

 heavy or (gasp) CG being out of range.

 I want to try this on my plane but I have no experience with strain  

 gauges.  I'm thinking of mounting them where the legs meet the  

 fuselage for the mains, and maybe at the movable joint on the front  

 (mine is a trike.)

 Any ideas?


	




One big problem will be that as you add weight, and the gear flexes,  

the bottom end of the gear legs need to move outwards.  If you are  

stopped, the friction between the tires and the ground prevent the  

bottom ends of the gear legs from spreading apart.  Once you start to  

move, and the wheels roll, the wheels will spread apart a bit to allow  

the gear legs to take up their new natural position.  So, once the  

aircraft is loaded, you won't get a repeatable measurement until the  

aircraft rolls a few feet.  If while the aircraft is rolling, a tire  

comes upon a piece of ground that is not even from side to side, that  

will tend to make the wheel roll a bit to the left or right of its  

natural position, which will affect the strain on the upper end of the  

gear leg, changing the strain gauge output.



There is no harm in conducting the experiment, but I'm not optimistic  

that you would be able to get acceptable accuracy in the real world.  

I'll be amazed if you get accuracy better than 100 lb.



Please keep up posted.  This is an interesting project.

--

Kevin Horton (Grounded)

RV-8 (Flight Test Phase)

Ottawa, Canada

http://www.kilohotel.com/rv8

nuckolls.bob(at)aeroelect
Guest

Posted: Wed Jul 01, 2009 2:28 pm Post subject: self weighing our planes

 	  Quote: 	
		  

 One big problem will be that as you add weight, and the gear flexes,  

 the bottom end of the gear legs need to move outwards.  If you are  

 stopped, the friction between the tires and the ground prevent the  

 bottom ends of the gear legs from spreading apart.  Once you start to  

 move, and the wheels roll, the wheels will spread apart a bit to allow  

 the gear legs to take up their new natural position.  So, once the  

 aircraft is loaded, you won't get a repeatable measurement until the  

 aircraft rolls a few feet.  If while the aircraft is rolling, a tire  

 comes upon a piece of ground that is not even from side to side, that  

 will tend to make the wheel roll a bit to the left or right of its  

 natural position, which will affect the strain on the upper end of the  

 gear leg, changing the strain gauge output.



 There is no harm in conducting the experiment, but I'm not optimistic  

 that you would be able to get acceptable accuracy in the real world.  

 I'll be amazed if you get accuracy better than 100 lb. 	


    Aha! I'd not thought of that one. Thanks Ken.



    Got my feet wet in strain gages about 38 years

    ago when we fiddled with adding a patient weighing

    feature to the Mobilizer hospital patient transporter

    for which I was developing the electrics.



     http://aeroelectric.com/Pictures/Misc/Mobilizer_3s.jpg



    The task using electronics available at the time

    was a challenge! The feature didn't get incorporated

    until years after the project was sold off and 

    I note that the brochure doesn't mention it now.



     http://tinyurl.com/mtt42o 



    Here's what we wrestled with back then . . . and

    you have to look forward to today.



    Strain gages measure stretching or compression

    on the surface. It's expressed in MICROINCHES per

    INCH of dimensional variation as the material

    is stressed. There's an excellent historical

    on perceptions and measurement of force at:



  http://www.omega.com/Literature/Transactions/volume3/history.html



    The full scale value of signal from a strain

    gage is very small. Typically, a strain-gage

    bridge stretched (or compressed) to near limits

    and excited with 10 volt will give you an output

    between 5 and 20 millivolts. The materials from

    which your landing gear is constructed will

    determine how much strain the gage sees . . .

    but in landing gears (designed for robustness)

    it's hard to get large values of strain on

    robust articles!  It's more likely that you

    would get useful data if you could incorporate

    off-the-shelf, ruggedized load cells into your

    gear system.



  http://www.daytronic.com/products/trans/t-loadcells.htm



    Pretty ugly . . . no?



    Hence the signal you need to slice up into

    1000-2000 parts for accurately resolving

    weights can get pretty small to begin with.

    As Ken mentioned, getting the geometry right

    for accurately sensing the true gravity 

    component of load on the gear is daunting.

    Measuring pressure in an oleo strut seems

    most promising.



    We do this kind of thing in the lab all the

    time . . . and on flight test aircraft. But I

    can tell you that of ALL the measurements we

    do on test airframes, strain gages are the

    most problematic either for bonding, wiring,

    amplifying signals to useful levels, etc.



    Even if you whipped the instrumentation

    design, then there's a matter of robustness in

    the work-a-day environment.



    Accurate resolution of weight-on-wheels in service

    has been considered on a lot of projects big and small.

    They may be doing it well on something like

    the A380 or B787 . . . but if my boss handed

    me a project like that today, I'd seriously

    consider advancing my retirement date! It's

    NOT easy or everyone would be doing it.



    Bob . . .

    



     [quote][b]

aerobubba(at)earthlink.ne
Guest

Posted: Thu Jul 02, 2009 4:41 am Post subject: self weighing our planes

IIRC, the Airbus A-320 family of aircraft weigh themselves.  Right after

takeoff, and for the reasons cited previously...

harley(at)AgelessWings.co
Guest

Posted: Thu Jul 02, 2009 5:11 am Post subject: self weighing our planes

OK, my turn...we used strain gauges in the processing tanks when I worked for a living (pharmaceutical company). It was my idea to incorporate them, and it became my responsibility to calibrate and see that they were properly maintained.  

 

 For example, when the 5,000 gallon processors were full of product being manufactured, even a fork truck driving by in an aisle outside the room would change the readings...the act of mixing the product would change the readings...even trying to massage the information we were getting from the gauges through computers only worked when everything was still...running water or other liquids into the process could only be accurately measured after the fluids had stopped sloshing around. 

 

 So, how can strain gauges ever work in a plane while it is moving (as someone earlier wished for...to determine LANDING WEIGHT for example!) Once the plane is in the air, the load is off the legs...the strain is gone...at least the strain from the craft's weight.  And while flying, even if there was a method to transfer the measured load from the legs to the wings, that would change constantly with attitude and g forces. 

 

 The only way I can see the airbus weighing themselves right after take off is a differential between the reading on the ground motionless, and when flying level...after that, I would think that any "weight" reading would be interpolated from fuel burn rate and not an actual weight. 

 

 Harley

 

 glen matejcek wrote: [quote]    	  Quote: 	
		  --> AeroElectric-List message posted by: "glen matejcek" <aerobubba(at)earthlink.net> (aerobubba(at)earthlink.net)



IIRC, the Airbus A-320 family of aircraft weigh themselves.  Right after

takeoff, and for the reasons cited previously...

  	
 [b]

khorton01(at)rogers.com
Guest

Posted: Thu Jul 02, 2009 6:22 am Post subject: self weighing our planes

On 2 Jul 2009, at 08:29, glen matejcek wrote:



 	  Quote: 	
		   

 >



 IIRC, the Airbus A-320 family of aircraft weigh themselves.  Right  

 after

 takeoff, and for the reasons cited previously...


	


I've done flight testing on most of the Airbus family, and this is the  

first I've ever heard of this.  The fly-by-wire Airbus aircraft do  

have a backup CG calculation that uses airspeed, weight and stabilizer  

angle.  This serves to crosscheck the CG that is calculated from the  

crew entered values of zero fuel weight and CG.  Maybe this is what  

you were thinking of.



--

Kevin Horton (Grounded)

RV-8 (Flight Test Phase)

Ottawa, Canada

http://www.kilohotel.com/rv8

nuckolls.bob(at)aeroelect
Guest

Posted: Thu Jul 02, 2009 6:22 am Post subject: self weighing our planes

At 07:29 AM 7/2/2009, you wrote:

 	  Quote: 	
		  

<aerobubba(at)earthlink.net>



IIRC, the Airbus A-320 family of aircraft weigh themselves.  Right after

takeoff, and for the reasons cited previously...


	


   Hmmmm . . . that perhaps answers some questions

   about maintain strain gage calibration that accounts

   for creep in offsets. Waiting until after t.o to

   display weight gets them a "zero weight" value off

   the gear stress sensors that becomes a new baseline

   for the next weighing action.



   But that does beg the question as to what's the

   value of knowing that you're over-gross/out-of-CG

   AFTER takeoff?



        Bob . . .



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

        ( . . .  a long habit of not thinking   )

        ( a thing wrong, gives it a superficial )

        ( appearance of being right . . .       )

        (                                       )

        (                  -Thomas Paine 1776-  )

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

BobsV35B(at)aol.com
Guest

Posted: Thu Jul 02, 2009 6:36 am Post subject: self weighing our planes

Good Morning aerobubba,

  

 Any of us can do the same if we wish to go to the trouble of getting highly  accurate calibration of all factors involved. For any specific weight and any  specific angle of attack there will be just one speed at which the aircraft will  leave the ground. 

  

 If we note that speed and adjust for all the other pertinent factors we  will have the weight.

  

 I have used that technique to some degree when flying the DC-8 in a charter  operation. I found that if my weight really was what the paperwork said it was  and I initiated rotation when the book said I should, the DC-8 would leave the  surface at a nine degree nose up attitude. When I started to find airplanes in  the charter operation that didn't do what I expected, I began to evaluate each  takeoff very carefully. 

  

 If I rotated to nine degrees and it did not fly, I held the nine degrees  until it did lift off.  I would then add two thousand pounds to whatever my  weight manifest said for each knot above the normal lift off speed that I  attained by holding the nine degrees. If I then added that extra weight to my  performance calculations, all became normal. 

  

 As an example, if the lift off speed was ten knots higher than had been  calculated I would be twenty thousand pounds heavier than the paperwork showed.  By using that new weight to establish climb and cruise numbers, the airplane  would deliver the performance required. Hopefully, modern techniques for  gathering the data for weight manifests have improved drastically in the  thirty-five plus years since I flew those charters, but it worked well for  me!

  

 Happy Skies,

  

 Old Bob

  

 Downers Grove, IL

 LL22

 Stearman N3977A

  

  In a message dated 7/2/2009 7:44:03 A.M. Central Daylight Time,  aerobubba(at)earthlink.net writes:

  	  Quote: 	
		  -->    AeroElectric-List message posted by: "glen matejcek"    <aerobubba(at)earthlink.net>



IIRC, the Airbus A-320 family of    aircraft weigh themselves.  Right after

takeoff, and for the reasons    cited  ========================bsp;  = Use   utilities  Day  ================================================               - MATRONICS WEB FORUMS  ================================================             - List Contribution Web Site  sp;                             ===================================================



	


 Dell Summer Savings: Cool Deals on Popular Laptops - Shop Now!

  [quote][b]

nuckolls.bob(at)aeroelect
Guest

Posted: Thu Jul 02, 2009 6:38 am Post subject: self weighing our planes

 	  Quote: 	
		  For example, when the 5,000 gallon processors were full of product 

being manufactured, even a fork truck driving by in an aisle outside 

the room would change the readings...the act of mixing the product 

would change the readings...even trying to massage the information 

we were getting from the gauges through computers only worked when 

everything was still...running water or other liquids into the 

process could only be accurately measured after the fluids had 

stopped sloshing around.


	


   Yeah. I recall an associate once describing strain

   gage technology akin to working with tweezers

   under a microscope during an earthquake. It's

   truly an exercise in sifting grains of sugar

   from the rock salt. The artful application of

   strain gages has been enhanced by advances in

   software analysis of noise-laden micro-signals.

   Computers made a huge improvement in accuracy and

   resolution of slow moving data but if you're

   wanting to measure vibration or other rapidly

   changing data over long periods of time, it's

   a whole new ball game.

        Bob . . .



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

        ( . . .  a long habit of not thinking   )

        ( a thing wrong, gives it a superficial )

        ( appearance of being right . . .       )

        (                                       )

        (                  -Thomas Paine 1776-  )

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

rv7a.builder(at)yahoo.com
Guest

Posted: Thu Jul 02, 2009 7:15 am Post subject: self weighing our planes

Perhaps knowing something about the weight and CG in case you need to make a landing, especially an emergency landing?  JR



---

nuckolls.bob(at)aeroelect
Guest

Posted: Thu Jul 02, 2009 7:20 am Post subject: self weighing our planes

At 10:12 AM 7/2/2009, you wrote:

 	  Quote: 	
		  

<rv7a.builder(at)yahoo.com>

Perhaps knowing something about the weight and CG in case you need 

to make a landing, especially an emergency landing?  JR




	


   But is it not an FAA mandate (and a damned good

   idea) that the pilot know that weight and balance

   limits have been checked BEFORE takeoff?

        Bob . . .



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

        ( . . .  a long habit of not thinking   )

        ( a thing wrong, gives it a superficial )

        ( appearance of being right . . .       )

        (                                       )

        (                  -Thomas Paine 1776-  )

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

BobsV35B(at)aol.com
Guest

Posted: Thu Jul 02, 2009 7:31 am Post subject: self weighing our planes

Good Morning Bob,

  

 It has to do with something like: "The best laid plans of mice and men  ------   "

  

 Happy Skies,

  

 Old Bob

  

  In a message dated 7/2/2009 10:22:05 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>



At 10:12 AM 7/2/2009, you    wrote:

 	  Quote: 	
		  --> AeroElectric-List message posted by: "rv7a.builder"    

<rv7a.builder(at)yahoo.com>

Perhaps knowing    something about the weight and CG in case you need 

to make a landing,    especially an emergency landing?  JR




	


   But is    it not an FAA mandate (and a damned good

   idea) that the pilot    know that weight and balance

   limits have been checked BEFORE    takeoff?

        Bob . . .



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

           ( . . .  a long habit of not thinking      )

        ( a thing wrong, gives it a superficial    )

        ( appearance of being right . . .          )

        (                                             )

           (                  -Thomas Paine    1776-  )

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



	


 Dell Summer Savings: Cool Deals on Popular Laptops - Shop Now!

  [quote][b]

echristley(at)nc.rr.com
Guest

Posted: Thu Jul 02, 2009 11:12 am Post subject: self weighing our planes

Kevin Horton wrote:

 	  Quote: 	
		  



 One big problem will be that as you add weight, and the gear flexes, 

 the bottom end of the gear legs need to move outwards.  If you are 

 stopped, the friction between the tires and the ground prevent the 

 bottom ends of the gear legs from spreading apart.  Once you start to 

 move, and the wheels roll, the wheels will spread apart a bit to allow 

 the gear legs to take up their new natural position.  So, once the 

 aircraft is loaded, you won't get a repeatable measurement until the 

 aircraft rolls a few feet.  If while the aircraft is rolling, a tire 

 comes upon a piece of ground that is not even from side to side, that 

 will tend to make the wheel roll a bit to the left or right of its 

 natural position, which will affect the strain on the upper end of the 

 gear leg, changing the strain gauge output.



 There is no harm in conducting the experiment, but I'm not optimistic 

 that you would be able to get acceptable accuracy in the real world. 

 I'll be amazed if you get accuracy better than 100 lb.




	


I'd expect that what you'd get is a readout that bounced around.  The 

question is, does it bounce around the middle of your W&B range, or is 

it bouncing around one of the extremes?  If you use it for a sanity 

check, it could be a useful tool.  No one really needs the weight to 

within a 1/4 oz anyway, just whether the wife was lying about how many 

shoes she was taking.  If you're trying to use it to get an exact W&B, 

I'd say you were fooling yourself. 



BTW, Kevin.  If I were within 100lbs of gross or 1/2" of my CG limit, 

I'd be reweighing stuff and re-doing my calculation a couple more times 

with extra care anyway 8*)



-- 



http://www.ernest.isa-geek.org

Eric M. Jones

Joined: 10 Jan 2006
Posts: 565
Location: Massachusetts

Posted: Fri Jul 03, 2009 6:58 am Post subject: Re: self weighing our planes

There have been a lot of good suggestions here.



If you want to know the whole story, use the search facility at USPTO.com, which is the US patent and trademark office....always a first stop for technological issues. 



Search "aircraft weighing" or similar strings. This search takes a couple minutes but will give you all the relevant patents. Anything filed before July3, 1989 is yours to use in any way you want. You can use more recent stuff, but don't commercialize or advertise it.



You must download and install AlternaTIFF:  http://www.alternatiff.com/  to see and print the full images. It is well worth a few minutes to figure out how to do this.



My other fav source is the NACA/NASA Technical Report Server: 

http://naca.larc.nasa.gov/search.jsp



This goes back to the start of aviation and is well worth a look.



"The problem with the world is that only the intelligent people want to be 

smarter, and only the good people want to improve." 

    - Eolake Stobblehouse

_________________
Eric M. Jones
www.PerihelionDesign.com
113 Brentwood Drive
Southbridge, MA 01550
(508) 764-2072
emjones(at)charter.net

aerobubba(at)earthlink.ne
Guest

Posted: Fri Jul 03, 2009 9:20 am Post subject: self weighing our planes

glen matejcek

aerobubba(at)earthlink.net



 	  Quote: 	
		   So, how can strain gauges ever work in a plane while it is moving (as 

 someone earlier wished for...to determine LANDING WEIGHT for example!) 


	


Well, if strain gauges were to be used my guess would be to put them on the

spars, subtract the stabilizer load from the wing load and then factor by

the g load.



 	  Quote: 	
		      But that does beg the question as to what's the

    value of knowing that you're over-gross/out-of-CG

    AFTER takeoff?


	


That was my first question.  As I recall, the answer given was to get a

measured weight in flight to determine accurate performance numbers.  The

bus continuously displayed buffet margins, cruise speeds, best glide speed,

and the low speed raster.  I don't know how much of that can be calculated

and displayed without determining the weight of the aircraft.  An

independent AoA is pretty straight forward, but displaying performance

hacks numerically without knowing the weight of the plane seems like it'd

be a little trickier.  It also occurs to me that the glide ratio of that

plane varied with weight (due to flexure of the structure causing a change

in the geometric twist of the wing ) which would factor into best economy

and glide calculations.



 	  Quote: 	
		   I've done flight testing on most of the Airbus family, and this is the  

 first I've ever heard of this.  The fly-by-wire Airbus aircraft do  

 have a backup CG calculation that uses airspeed, weight and stabilizer  

 angle.  This serves to crosscheck the CG that is calculated from the  

 crew entered values of zero fuel weight and CG.  Maybe this is what  

 you were thinking of.


	


Given a fighting chance, I can pooch just about anything, but I just went

and took a quick look at some old training docs and they do say the plane

calculated it's weight after lift off.  



 	  Quote: 	
		   As an example, if the lift off speed was ten knots higher than had been 



 calculated I would be twenty thousand pounds heavier than the paperwork 

 showed.  By using that new weight to establish climb and cruise numbers,

  the 

 airplane  would deliver the performance required. Hopefully, modern techni

 ques 

 for  gathering the data for weight manifests have improved drastically in

  the  

 thirty-five plus years since I flew those charters, but it worked well for



 me!




	


About 10 years ago my employer of that moment darn near lost a 737 at LGA. 

At V1 the F/O pulled the yoke all the way to the stop, yet the nose stayed

firmly on the ground.  Fortunately, he had the presence of mind to start

running nose up trim.  They got airborne before getting wet, but not by

much.  After returning for the landing they found 5,000 undocumented pounds

in the forward bin....  

 	  Quote: 	
		  



 Perhaps knowing something about the weight and CG in case you need to

make a landing,
	


 	  Quote: 	
		   especially an emergency landing? JR




	


I have yet to see Sully's presentation, but having that and related info

instantly available was likely a factor in the Hudson river event.  I don't

recall if it was the 'bus or a different glass cockpit in my past, but one

of them would give you a glide range circle instead of an altitude

intercept arc when you spun the altitude alerter down to ground level.  If

that function was available on the 'bus, it could have been an aid in

determining if to a return to LGA (or TEb or EWR) was feasible.



 	  Quote: 	
		  

    But is it not an FAA mandate (and a damned good

    idea) that the pilot know that weight and balance

    limits have been checked BEFORE takeoff?



Certainly.  But load reports can be significantly off, you can burn an
	


awful lot of gas enroute, totalizers can be inaccurate or inop, fuel gauges

can err, fuel can be lost, and so on.  If 767's could weigh themselves, the

odds of a Gimli Glider - type episode would probably be reduced.  It's just

one more tool, whose greatest utility might not be realized until the

unforeseen occurs.



 	  Quote: 	
		  

 It has to do with something like: "The best laid plans of mice and men  




	


AMEN!

DanFM01(at)butter.toast.n
Guest

Posted: Fri Jul 03, 2009 9:43 am Post subject: self weighing our planes

A point just to prevent confusion.  USPTO.com is a private site that

offers patent related services.  The government site is USPTO.gov



On Fri, 2009-07-03 at 07:58 -0700, Eric M. Jones wrote:

 	  Quote: 	
		   

 

 There have been a lot of good suggestions here.

 

 If you want to know the whole story, use the search facility at USPTO.com, which is the US patent and trademark office....always a first stop for technological issues. 

 


	


 	  Quote: 	
		   

 

 

 Read this topic online here:

 

 http://forums.matronics.com/viewtopic.php?p 51306#251306

Eric M. Jones

Joined: 10 Jan 2006
Posts: 565
Location: Massachusetts

Posted: Fri Jul 03, 2009 9:55 am Post subject: Re: self weighing our planes

Slightly off topic--but there is a little electronic gauge that hot rods use that measures acceleration. Reduced take-off acceleration hampers your ability to get the bird into the air. It could be caused by any of a number of issues such as excess weight--and would be good to know.

_________________
Eric M. Jones
www.PerihelionDesign.com
113 Brentwood Drive
Southbridge, MA 01550
(508) 764-2072
emjones(at)charter.net

khorton01(at)rogers.com
Guest

Posted: Fri Jul 03, 2009 11:20 am Post subject: self weighing our planes

On 3-Jul-09, at 13:18 , glen matejcek wrote:



 	  Quote: 	
		   

 >



> I've done flight testing on most of the Airbus family, and this is  

> the

> first I've ever heard of this.  The fly-by-wire Airbus aircraft do

> have a backup CG calculation that uses airspeed, weight and  

> stabilizer

> angle.  This serves to crosscheck the CG that is calculated from the

> crew entered values of zero fuel weight and CG.  Maybe this is what

> you were thinking of.



 Given a fighting chance, I can pooch just about anything, but I just  

 went

 and took a quick look at some old training docs and they do say the  

 plane

 calculated it's weight after lift off.


	


Fascinating.  Do the docs give any clue what the data source is for  

this calculation?



The aircraft does know the crew-entered zero fuel weight and it knows  

the fuel quantity sensed by the fuel indication system.  It does  

continuously calculate the current gross weight from that data, and  

this is the weight that is used to display minimum flap/slat retract  

speeds, green dot speed, etc.



--

Kevin Horton (Grounded)

RV-8 (Flying)

Ottawa, Canada

http://www.kilohotel.com/rv8

Eric M. Jones

Joined: 10 Jan 2006
Posts: 565
Location: Massachusetts

Posted: Fri Jul 03, 2009 12:31 pm Post subject: Re: self weighing our planes

Google "weight and balance computer"



Everything is there. DON'T Miss the Librascope analog weight and balance computer. You can Google that too.

_________________
Eric M. Jones
www.PerihelionDesign.com
113 Brentwood Drive
Southbridge, MA 01550
(508) 764-2072
emjones(at)charter.net

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