redflyer
Topic Author
Posts: 3882
Joined: Thu Feb 24, 2005 3:30 am

Automatic Weight & Balance Calc Device

Tue Jul 05, 2011 5:54 pm

I recall a couple of years ago after the EK A340 tail strike in Australia there was some discussion around why an automatic device couldn't be implemented to prevent just such an occurrence. It appears Boeing has just patented such a device. Now we need to see if it can be put to practical use.

http://patft.uspto.gov/netacgi/nph-P...44.PN.&OS=PN/7967244&RS=PN/7967244
My other home is in the sky inside my Piper Cherokee 180.
 
pilotpip
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Joined: Fri Sep 19, 2003 3:26 pm

RE: Automatic Weight & Balance Calc Device

Tue Jul 05, 2011 6:00 pm

We've been doing ours via ACARS for 3 years. To put some sort of sensors on the aircraft, while patented is likely impractical.
DMI
 
yeelep
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Joined: Mon Apr 04, 2011 7:53 pm

RE: Automatic Weight & Balance Calc Device

Tue Jul 05, 2011 7:27 pm

May be impractical as a retrofit, due to wiring, but on a new aircraft it wouldn't. I imagine it would be offered as a option if it ever is introduced.
 
redflyer
Topic Author
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RE: Automatic Weight & Balance Calc Device

Tue Jul 05, 2011 8:20 pm

Quoting yeelep (Reply 2):
I imagine it would be offered as a option if it ever is introduced.

And if it is ever introduced, my guess is it will be used only as a verification/sanity check.
My other home is in the sky inside my Piper Cherokee 180.
 
B747FE
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RE: Automatic Weight & Balance Calc Device

Wed Jul 06, 2011 2:07 am

Looks like an upgrade of what has already been in use for many years.

Installed Weight Scales.. (by SunriseValley Mar 3 2005 in Tech Ops)?threadid=111949&searchid=112043&s=weight+scales#ID112043

Regards,
B747FE.
"Flying is more than a sport and more than a job; flying is pure passion and desire, which fill a lifetime"
 
474218
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RE: Automatic Weight & Balance Calc Device

Wed Jul 06, 2011 2:50 am

Quoting redflyer (Thread starter):
I recall a couple of years ago after the EK A340 tail strike in Australia there was some discussion around why an automatic device couldn't be implemented to prevent just such an occurrence. It appears Boeing has just patented such a device. Now we need to see if it can be put to practical use.


An on-board weight and balance system was an option on the L-1011 in the 1970's. Saudia was the only operator that choose the option and it was removed after only a very short time in service, as it provide to be quite failure prone!
 
JoeCanuck
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RE: Automatic Weight & Balance Calc Device

Wed Jul 06, 2011 5:20 am

It reminds me of the rough load calculations that can be made from checking the pressure in the suspension air bags on a big rig and trailer.

Electronic load cells are so reliable and small that it's amazing that it's taking this long to get them on planes. It wouldn't be difficult to beat the accuracy of the current system...especially for passengers.
What the...?
 
wilco737
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RE: Automatic Weight & Balance Calc Device

Wed Jul 06, 2011 6:09 am

The 747 has a simple system installed already. It won't give you exact trim and weight, but it is a form of check there.
If you enter a very aft CG into the FMS, but the real CG is far in the front and the nose gear is compressed, the airplane gives you an error message. Same happens the other way around as well.

Problem with these automatically weight is when it is snowing or raining or ice is on the airplane. The airplane then is a lot heavier than expected and the sensor would measuer that as well.

wilco737
  
 
Mir
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RE: Automatic Weight & Balance Calc Device

Wed Jul 06, 2011 6:13 am

Quoting wilco737 (Reply 7):
Problem with these automatically weight is when it is snowing or raining or ice is on the airplane. The airplane then is a lot heavier than expected and the sensor would measuer that as well.

And anti-ice fluid, I'd imagine.

-Mir
7 billion, one nation, imagination...it's a beautiful day
 
wilco737
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RE: Automatic Weight & Balance Calc Device

Wed Jul 06, 2011 6:19 am

Quoting Mir (Reply 8):
And anti-ice fluid, I'd imagine.

Yes, every additional substance (snow, ice, anti- ice fluid, rain...) on the airplane makes the airplane heavier...

wilco737
  
 
JoeCanuck
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RE: Automatic Weight & Balance Calc Device

Fri Jul 08, 2011 7:03 am

Quoting wilco737 (Reply 9):
Yes, every additional substance (snow, ice, anti- ice fluid, rain...) on the airplane makes the airplane heavier...

Is that really such a bad thing? I would venture a guess that the vast majority of flights will not be encumbered by snow and except for those rare occasions, load sensors would seem to me to be a reliable tool.
What the...?
 
tdscanuck
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RE: Automatic Weight & Balance Calc Device

Sat Jul 09, 2011 5:18 am

Quoting JoeCanuck (Reply 10):
I would venture a guess that the vast majority of flights will not be encumbered by snow and except for those rare occasions, load sensors would seem to me to be a reliable tool.

The problem is that the load sensors that are really simple and don't introduce a new failure path aren't that accurate, and the ones that are really accurate introduce weigh, complexity, and (most importantly) a new load path. Yes, it would be nice to have, and it's offered on some jets where it really matters (mostly freighters) but, in the vast majority of cases, it's not worth the headache.

Tom.
 
bond007
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RE: Automatic Weight & Balance Calc Device

Sat Jul 09, 2011 11:33 am

Quoting tdscanuck (Reply 11):
aren't that accurate


Agreed, but is that lack of accuracy relative to the accuracy of load sensors as a whole, or relative to the accuracy to what we calculate the CG and W&B to the majority of the time?


Jimbo
I'd rather be on the ground wishing I was in the air, than in the air wishing I was on the ground!
 
JoeCanuck
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RE: Automatic Weight & Balance Calc Device

Mon Jul 11, 2011 7:03 am

Accurate, reliable and portable load sensors have been available to the trucing industry and regulators for decades. I see the problem of implementation to be more of avoiding the expense, time and pain of certifying the devices for commercial flying use than their lack of accuracy.

If not installed on the plane, load sensor pads could be set up at the gates, either permanent or portable. Or set up on the taxiway. A vehicle doesn't have to completely stop to get an accurate weight measurement.

I have no doubt that a properly calibrated load sensor would be significantly more accurate than the current weight guesstimates of passengers.
What the...?
 
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Jetlagged
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RE: Automatic Weight & Balance Calc Device

Thu Jul 14, 2011 11:01 pm

Quoting wilco737 (Reply 7):
The 747 has a simple system installed already. It won't give you exact trim and weight, but it is a form of check there.
If you enter a very aft CG into the FMS, but the real CG is far in the front and the nose gear is compressed, the airplane gives you an error message. Same happens the other way around as well

As an option, 744s have a weight and balance system installed which will calculate gross weight and CG and present those on the FMS PERF INIT page for the crew to either accept, or enter values from the loadsheet.
The glass isn't half empty, or half full, it's twice as big as it needs to be.
 
KAUSpilot
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RE: Automatic Weight & Balance Calc Device

Fri Jul 15, 2011 11:49 am

The 744 freighters I fly have a gross weight and CG readout on the main deck just forward of the L1 door, near the nose cargo door control panel. In addition, I have flown some 744 BCF's which give a gross weight readout on the upper EICAS display in the flight deck. I was told that the airplane computes this by measuring the compression of the nose gear strut, although I'm sure it's more complex than that.

Even though the plane calculates these weights on its own, we still use separate, computer generated weight and balance manifests to calculate aircraft performance and generate takeoff speeds. In my experience (and I'm still very new to the airplane), the airplane's readout and the computer generated manifest have usually been within a few percentage points of each other.
 
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Jetlagged
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RE: Automatic Weight & Balance Calc Device

Fri Jul 15, 2011 7:17 pm

Quoting KAUSpilot (Reply 15):
The 744 freighters I fly have a gross weight and CG readout on the main deck just forward of the L1 door, near the nose cargo door control panel. In addition, I have flown some 744 BCF's which give a gross weight readout on the upper EICAS display in the flight deck. I was told that the airplane computes this by measuring the compression of the nose gear strut, although I'm sure it's more complex than that.

Once the FMC has a gross weight and CG initialised (either from the loadsheet or via the WBS, if installed) that is the basis for all weight and CG calculations in flight. The only thing which varies in flight is fuel weight and CG, so the FMC can compute changes in gross weight and CG as a result of fuel usage.
The glass isn't half empty, or half full, it's twice as big as it needs to be.

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