Stock W&B

Jaybird180

Jaybird180

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Jaybird180
For certified, manufactured aircraft why do they require W&B sheets upon coming off the assembly line? Certianly I understand if an aircraft has been modified for equipment substitued, but if serial # 000034 is the same as 000035 why not publish and use stock figures published in the POH and only require W&B sheets if there have been any changes?
 
You're assuming that two identically equipped airplanes will weigh the same coming off the line.

They won't. One may have gotten a slightly thicker coat of paint. One may have had a batch of wiring in that is slightly heavier.

Bottom line is that every airplane gets the "as built" W&B as part of the certification process.
 
TMetzinger said:
You're assuming that two identically equipped airplanes will weigh the same coming off the line.

They won't. One may have gotten a slightly thicker coat of paint. One may have had a batch of wiring in that is slightly heavier.

Bottom line is that every airplane gets the "as built" W&B as part of the certification process.
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What would cause this variation in an assembly line built, same equipment airplane?

Yes, manufacturing tolerances exist, but the W&B tolerance can be stated in the POH. One needn't extract every ounce from the max weight (which usually includes 150% structural capacity anyhow)
 
TMetzinger said:
You're assuming that two identically equipped airplanes will weigh the same coming off the line.

They won't. One may have gotten a slightly thicker coat of paint. One may have had a batch of wiring in that is slightly heavier.

Bottom line is that every airplane gets the "as built" W&B as part of the certification process.
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Not really correct. Manufactures are allowed to have a "baseline" aircraft for W&B purposes and then can add options. An airplane manufactured using standard manufacturing techniques is weighed and used as this baseline.

For Quality Control an airplane is pulled from the production line every so often and weighed to see that it conforms to the baseline model.
 
Rotor&Wing said:
Not really correct. Manufactures are allowed to have a "baseline" aircraft for W&B purposes and then can add options. An airplane manufactured using standard manufacturing techniques is weighed and used as this baseline.

For Quality Control an airplane is pulled from the production line every so often and weighed to see that it conforms to the baseline model.
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So, I imagine you have an answer to the original question:rolleyes:
 
The answer is a sheet must be prepared for each aircraft, but they can do it by computation off the baseline, and they do not have to actually weight each plane, just an occasional sampling.
 
Jaybird180 said:
For certified, manufactured aircraft why do they require W&B sheets upon coming off the assembly line? Certianly I understand if an aircraft has been modified for equipment substitued, but if serial # 000034 is the same as 000035 why not publish and use stock figures published in the POH and only require W&B sheets if there have been any changes?
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WE all assume you are referring to an aircraft built on a production certificate, because all aircraft are certified, and all are manufactured.

all other aircraft not built on a production certificate are weighed each and every one of them have their own weight and balance sheet.

If you think not, try and get a Experimental Amateur built aircraft certified with out one, or ask the vintage folks how they comply with AROW, with out one.
 
Ron Levy said:
The answer is a sheet must be prepared for each aircraft, but they can do it by computation off the baseline, and they do not have to actually weight each plane, just an occasional sampling.
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What percentage of aircraft in light general aviation do you believe that still comply with that weight and balance sheet?
 
Rotor&Wing said:
Not really correct. Manufactures are allowed to have a "baseline" aircraft for W&B purposes and then can add options. An airplane manufactured using standard manufacturing techniques is weighed and used as this baseline.

For Quality Control an airplane is pulled from the production line every so often and weighed to see that it conforms to the baseline model.
Click to expand...

Are you saying they don't weigh each airplane to put the info in the AFM, or that they do but not for the reason I gave?

I've never seen an airplane, even freshly delivered, without an individual w&b. Or is the individual weight calculated?

Sent from my ADR6300 using Tapatalk
 
When we bought the 2006 172S, it came with a fleet average weight and balance from the factory. It specified right on it that it was based on an average weight of sampled models. We did an actual W&B and found it about 15 pounds heavier.

Dan
 
Tom-D said:
What percentage of aircraft in light general aviation do you believe that still comply with that weight and balance sheet?
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I don't know, and I don't care, and it doesn't matter as regards the original question.
 
Mine are nice round numbers, If I think about it tomorrow I will scan and post what Piper charged me 175 bucks for.

Think a photo copied sheet of legal paper with handwritten nice round numbers on it.
 
Ron Levy said:
I don't know, and I don't care, and it doesn't matter as regards the original question.
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Just a point worth pondering to those interested enough to post this thread.

Of all the old aircraft that I deal with yearly there is only 1 that still has never been modified and the W&B sheet up dated.
 
Tom-D said:
Just a point worth pondering to those interested enough to post this thread.

Of all the old aircraft that I deal with yearly there is only 1 that still has never been modified and the W&B sheet up dated.
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I know of 2 pre 1975 rigs that have been flown to annual and back and that's it since new, the owner is under some sort of opinion that the planes will be museum pieces one day, they're Cessna 172's while a fine fine plane, I don't think that day is anytime soon.
 
TMetzinger said:
Are you saying they don't weigh each airplane to put the info in the AFM, or that they do but not for the reason I gave?

I've never seen an airplane, even freshly delivered, without an individual w&b. Or is the individual weight calculated?

Sent from my ADR6300 using Tapatalk
Click to expand...

The later C-172s all had their W&B in the POH. and it also gives the weight of each piece of equipment and its arm, to allow the changes to be calculated and recorded in the POH. There is no separate W&B sheet. That is one of the reasons the aircraft is not airworthy without that aircrafts POH.
 
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Tom-D said:
The later C-172s all had their W&B in the POH. and it also gives the weight of each piece of equipment and its arm, to allow the changes to be calculated and recorded in the POH. There is no separate W&B sheet. That is one of the reasons the aircraft is not airworthy with that aircrafts POH.
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:dunno:
 
Tom-D said:
Of all the old aircraft that I deal with yearly there is only 1 that still has never been modified and the W&B sheet up dated.
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On that note, a word of caution -- check all the math. I've seen planes with bad W&B data that traced back to a math error decades back. We picked them up when we did a W&B, and it appeared the aircraft was a couple of inches out of forward cg with two in front and a couple of nav bags in the back seat -- which just didn't make sense. Going backwards through all the calculations for 25-40 years, we found an error early on which nobody caught through a dozen or more recomputations with removed/replaced/installed equipment. A bit of work with Excel fixed the problem, but you know that nobody did a W&B in all that time or they would have realized something was way out of whack.
 
I found an errant W&B while getting ready for my PPL checkride. No idea if the maintenance shop fixed it. They seemed to take it serious in my presence but I didn't get that warm and fuzzy that they were going to DO anything about it.
 
Ron Levy said:
On that note, a word of caution -- check all the math. I've seen planes with bad W&B data that traced back to a math error decades back. We picked them up when we did a W&B, and it appeared the aircraft was a couple of inches out of forward cg with two in front and a couple of nav bags in the back seat -- which just didn't make sense. Going backwards through all the calculations for 25-40 years, we found an error early on which nobody caught through a dozen or more recomputations with removed/replaced/installed equipment. A bit of work with Excel fixed the problem, but you know that nobody did a W&B in all that time or they would have realized something was way out of whack.
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This old 170 is as stock as it gets, and still has the Cessna W&B sheet. even the radios haven't been changed, the owner flys it VFR on a hand held.

I doubted the accuracy of the numbers so last year I put it on the scales, it's with in 1 pound of the empty weight given on the Cessna Original factory data.

Surprised me.
 
Well this has been interesting. Every single new Cessna (fresh from the factory) I've ever flown has had a serialized AFM with a specific W&B sheet in it for that airplane. And they varied in BEW, even though they were supposedly identically equipped.

I Think what I've learned here is that that W&B sheet may reflect a calculation rather than an actual weighing.

I couldn't make any sense of what Tom D was trying to say here. I don't know if that's a reflection on Tom or me, though. It may be the difference between a generic POH/PIM and the individual airplane flight manual.
 
Are there repairs or other types of work that _require_ a new weighing rather than just calculations?

John
 
jsstevens said:
Are there repairs or other types of work that _require_ a new weighing rather than just calculations?

John
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Part 135 multiengine require reweighing the airplane on a periodical basis.

A good source of information is the FAA F-H-8083-1A "Aircraft Weight and Balance Handbook".
 
Rotor&Wing said:
Huh?...
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Well, the POH/AFM tells you all the placards that should be in/on the plane -- maybe that's what he meant. Or that for planes built after 1977, as well as earlier ones whose type certificate requires it, the POH/AFM must be in the plane per 14 CFR 91.9. Otherwise...:dunno:, because the POH is definitely not a placard.
 
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Rotor&Wing said:
You ain't the only one. :)
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Read the type certificate :
DATA PERTINENT TO ALL MODELS 172 THROUGH 172Q (cont'd)
Equipment:
NOTE 1:
The basic required equipment as prescribed in the applicable airworthiness requirements (see Certification Basis) must be installed in the aircraft for certification. This equipment must include a current Airplane Flight Manual effective S/N 17271035 and on.
 
Ron Levy said:
Well, the POH/AFM tells you all the placards that should be in/on the plane -- maybe that's what he meant. Or that for planes built after 1977, the POH/AFM must be in the plane per 14 CFR 91.9. Otherwise...:dunno:
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Exactly ! the aircraft is not airworthy without that aircraft's POH, simply because that is where the W&B is done.

grab one and read it. Plus read the type certificate
DATA PERTINENT TO ALL MODELS 172 THROUGH 172Q (cont'd)
Equipment:
NOTE 1:
The basic required equipment as prescribed in the applicable airworthiness requirements (see Certification Basis) must be installed in the aircraft for certification. This equipment must include a current Airplane Flight Manual effective S/N 17271035 and on.
 
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jsstevens said:
Are there repairs or other types of work that _require_ a new weighing rather than just calculations?

John
Click to expand...

Yes there is, those requirements for Cessna are in the structural repair manual, it varies from one manufacturer to another where that info is found.
 
Tom-D said:
The later C-172s all had their W&B in the POH. and it also gives the weight of each piece of equipment and its arm, to allow the changes to be calculated and recorded in the POH. There is no separate W&B sheet. That is one of the reasons the aircraft is not airworthy with that aircrafts POH.
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Did you mean "without"?
 
Makes much more sense. Neither one of us is nuts. I do the same thing when I proofread sometimes. I now get into the habit of having someone else proof it if it's really important or I'm getting graded on it.
 
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