Weight and Balance regs

flyingcheesehead

flyingcheesehead

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A&P's, is there something somewhere in the regs that says for a weight and balance change under a certain weight that the arm/moment doesn't need to be recalculated?

I've seen this a couple of times now, where on a small-ish change the weight is updated but the arm and moment are just left as is. Should I follow up, or is this something that is considered OK?
 
Circular (AC) 43.13-1 (as revised), Methods Techniques and Practices—Aircraft Inspection and Repair:
• One pound or less for an aircraft whose weight empty is less than 5,000 pounds;
• Two pounds or less for aircraft with an empty weight of more than 5,000 pounds to 50,000 pounds;
• Five pounds or less for aircraft with an empty weight of more than 50,000 pounds.


W&B good read
http://www.faa.gov/regulations_poli...on/pilot_handbook/media/PHAK - Chapter 09.pdf

quote came from page 9-4
 
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Tom-D said:
Circular (AC) 43.13-1 (as revised), Methods Techniques and Practices—Aircraft Inspection and Repair:
• One pound or less for an aircraft whose weight empty is less than 5,000 pounds;
• Two pounds or less for aircraft with an empty weight of more than 5,000 pounds to 50,000 pounds;
• Five pounds or less for aircraft with an empty weight of more than 50,000 pounds.


W&B good read
http://www.faa.gov/regulations_poli...on/pilot_handbook/media/PHAK - Chapter 09.pdf

quote came from page 9-4
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Hmmm. In both cases these were aircraft that weighed less than 5000 pounds but the mod was more than one pound.

However, the weight *was* shown. The CG was the old one. Right after the part you quoted is this:

"Negligible CG change is any change of less than 0.05 percent Mean Aerodynamic Chord (MAC) for fixed-wing aircraft."

How do I calculate MAC to determine if this is the case?
 
flyingcheesehead said:
Hmmm. In both cases these were aircraft that weighed less than 5000 pounds but the mod was more than one pound.

However, the weight *was* shown. The CG was the old one. Right after the part you quoted is this:

"Negligible CG change is any change of less than 0.05 percent Mean Aerodynamic Chord (MAC) for fixed-wing aircraft."

How do I calculate MAC to determine if this is the case?
Click to expand...

I don't think you have to. That is just your normal CG range on a straight wing airplane.
 
Amusingly as imprecise as it seems after 50 years of piecemeal W&B updates and assumptions about changes being "negligable" when I reweighed my plane, the new empty weight numbers were not very different than the old ones.
 
flyingron said:
Amusingly as imprecise as it seems after 50 years of piecemeal W&B updates and assumptions about changes being "negligable" when I reweighed my plane, the new empty weight numbers were not very different than the old ones.
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I had my new-to-me plane re-weighed at my first annual, and lost 100 pounds of useful load. I've heard plenty of "me-too" stories, too. I know at least two people who refuse to have their plane weighed because they're afraid of the same thing happening.
 
Jim_R said:
I had my new-to-me plane re-weighed at my first annual, and lost 100 pounds of useful load. I've heard plenty of "me-too" stories, too. I know at least two people who refuse to have their plane weighed because they're afraid of the same thing happening.
Click to expand...

100 lbs in a certified plane is ALOT of new weight.... Us experimental guys can add and subtract stuff as we play with different concepts...
 
Yup, when those negligible 1 pound changes (which were likely 2- 3 pounds) are done 25 times over the years you are gonna have a surprise when the plane has to go on the scales for some reason.
My mechanic (paranoid - but then I AM out to get him :) recalculates and makes the entry to the log for every change no matter what. He already has the plane in his computer software (he has been working on the plane since he was a teenager) - it is three keystrokes and done.
 
flyingcheesehead said:
Hmmm. In both cases these were aircraft that weighed less than 5000 pounds but the mod was more than one pound.

However, the weight *was* shown. The CG was the old one. Right after the part you quoted is this:

"Negligible CG change is any change of less than 0.05 percent Mean Aerodynamic Chord (MAC) for fixed-wing aircraft."

How do I calculate MAC to determine if this is the case?
Click to expand...

It's all here

http://www.faa.gov/regulations_policies/handbooks_manuals/aircraft/media/faa-h-8083-1a.pdf
 
N801BH said:
100 lbs in a certified plane is ALOT of new weight.... Us experimental guys can add and subtract stuff as we play with different concepts...
Click to expand...


We see probably an average 7 weigh jobs a week, with nealy all of them being the "load cell on a wing jack" type and not the "roll-on" platforms. I've seen a Cessna 750 (21,XXX empty) that underwent a full interior and paint job with a heavy inspection come out within 5 pounds of the superceded W&B Report. I calculate about 1 out of every 3 of these reports.

Typically a 10,000 to 25,000 pound jet gains somewhere between 5 and 50 pounds when it gets weighed.

If I weighed a single engine piston pounder and came out 100 pounds heaver, I would assume there is some kind of side load or preload on the scale cells interfering with an accurate weigh.
 
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I would assume at least part of it is from the cumulative effect of all the belly-jelly that accumulates in the bowels combined with years of "estimating" the +/- of add/removes.

bnt83 said:
If I weighed a single engine piston pounder and came out 100 pounds heaver, I would assume there is some kind of side load or preload on the scale cells interfering with an accurate weigh.
Click to expand...
 
bnt83 said:
We see probably an average 7 weigh jobs a week, with nealy all of them being the "load cell on a wing jack" type and not the "roll-on" platforms. I've seen a Cessna 750 (21,XXX empty) that underwent a full interior and paint job with a heavy inspection come out within 5 pounds of the superceded W&B Report. I calculate about 1 out of every 3 of these reports.

Typically a 10,000 to 25,000 pound jet gains somewhere between 5 and 50 pounds when it gets weighed.

If I weighed a single engine piston pounder and came out 100 pounds heaver, I would assume there is some kind of side load or preload on the scale cells interfering with an accurate weigh.
Click to expand...

Agreed... I bought some deadly accurate race car scales to weigh my plane,, 1/-1 lb resolution... Kind of a shame they just sit in my shop doing nothing 99% of the time..I weigh mime when I do any change to it like removing the heavy mufflers and installing SS tubing, or any prop change.. I can usually tell if I forgot to remove my 3 lb flight bag or a couple of quarts of spare oil... I cannot fathom a single engine plane picking up 100 lbs out of the blue though..:nonod:
 
For me, a 100lb increase would just be from bugs and oil. I'm afraid to wash it, lest the paint come off.
 
N801BH said:
Agreed... I bought some deadly accurate race car scales to weigh my plane,, 1/-1 lb resolution... Kind of a shame they just sit in my shop doing nothing 99% of the time..I weigh mime when I do any change to it like removing the heavy mufflers and installing SS tubing, or any prop change.. I can usually tell if I forgot to remove my 3 lb flight bag or a couple of quarts of spare oil... I cannot fathom a single engine plane picking up 100 lbs out of the blue though..:nonod:
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O-320 weighs 266# per this equipment list I'm looking at. 100# is A LOT
 
Dr. O said:
Yup, when those negligible 1 pound changes (which were likely 2- 3 pounds) are done 25 times over the years you are gonna have a surprise when the plane has to go on the scales for some reason.
Click to expand...
We've done a number of "weigh-ins" in the Grumman community, and find that our 1050-1500 lb empty weight planes average 1 lb more empty weight than the paperwork shows for every year since their last weighing.
 
bnt83 said:
O-320 weighs 266# per this equipment list I'm looking at. 100# is A LOT
Click to expand...

That is another misleading figure often thrown about in the experimental circles....

Lycoming lists the 0-320 at 266 lbs... Then you add all the components to actually make it run like starter, carb /fuel system, mags, harness, complete exhaust system, alternator, baffles, belts, hoses, oil cooler and filter and all the other little details it takes and you are magically in the 355+lbs range........
 
N801BH said:
That is another misleading figure often thrown about in the experimental circles....

Lycoming lists the 0-320 at 266 lbs... Then you add all the components to actually make it run like starter, carb /fuel system, mags, harness, complete exhaust system, alternator, baffles, belts, hoses, oil cooler and filter and all the other little details it takes and you are magically in the 355+lbs range........
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there is an engine, then there are appliances.:)
 
Jim_R said:
. . . . . I know at least two people who refuse to have their plane weighed because they're afraid of the same thing happening.
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Seriously? :hairraise: Do these same people believe that the laws of physics won't apply to them as long as the paperwork says so? I'm guessing these types are fudging their take-off weights even with the known understated BEW and are often the ones we read about in accident reports on warm days. Amazing.
 
When we first got our Cherokee 180. I removed the KX155 (only radio in the airplane), and installed a GNC300 with indicator, a Narco MK12-D with G/S, a KMA24 audio panel, and a PS engineering 4 place intercom.

cleaned all the FOD from inside the wings and fuselage, and Gained 200# useful load. :D
I guess all those "negligable" W&B entries in th' logs over the years added up.
 
bluerooster said:
When we first got our Cherokee 180. I removed the KX155 (only radio in the airplane), and installed a GNC300 with indicator, a Narco MK12-D with G/S, a KMA24 audio panel, and a PS engineering 4 place intercom.

cleaned all the FOD from inside the wings and fuselage, and Gained 200# useful load. :D
I guess all those "negligable" W&B entries in th' logs over the years added up.
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More likely, somewhere along the line someone made one or more arithmetic errors.

I always verify the calculations when an A&P modifies the W&B of my airplane and I've caught at least three mistakes. One wasn't even subtle (2" shift in CG with a weight change of less than 10 lbs.
 
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bluerooster said:
When we first got our Cherokee 180. I removed the KX155 (only radio in the airplane), and installed a GNC300 with indicator, a Narco MK12-D with G/S, a KMA24 audio panel, and a PS engineering 4 place intercom.

cleaned all the FOD from inside the wings and fuselage, and Gained 200# useful load. :D
I guess all those "negligable" W&B entries in th' logs over the years added up.
Click to expand...

Either someone really jacked the math up in the past or the scales were off. Id be looking hard to find that 200 lb discrepancy and wouldn't just trust the new numbers. Something could have been off with the new weighing.

200 lbs is a lot of weight.
 
jesse said:
Either someone really jacked the math up in the past or the scales were off. Id be looking hard to find that 200 lb discrepancy and wouldn't just trust the new numbers. Something could have been off with the new weighing.

200 lbs is a lot of weight.
Click to expand...

Sounds typical of a mistake of not removing the tear weight from the equation.
 
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