Weight & Balance Workup

ahkahn

ahkahn

Line Up and Wait
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Hi there-

Two questions. First of all, how often would you reweigh/rework your airplane? I cannot find the last weight and balance on my plane... it's just been a lot of +3/-3 entries in the POH.

Secondly, does anyone know of a reasonably priced weight/balance place around the Chicagoland area? I also frequently fly to Owensboro, KY, Detroit area, and Cincinnati area.

I've been quoted by one high-volume maintenance shop something like $800 to do a workup, and the next quote I got was for like $75, but it was a guy with a set of scales who does it on the side and can only do it like the 4th Thursday of every other month and only when the sun is out for longer than 15 hours.

Thanks in advance!
 
The $800 seems a bit high but the $75 is suspiciously low. Doing an actual weigh and then doing the W&B calculation and paperwork is not as quick and easy as one might think. First you need a set of calibrated scales which are not cheap. Then you need to prepare the aircraft for weighing which mean a good wash job, sumping the fuel so that only the unusable remains, making sure all other fluids are properly serviced, removing all payload (junk) from the aircraft, ensuring all required equipment is on board, etc. Then you normally weigh it three times and take the average of the weights for each of the three points. Then you do the calculations and prepare the report. Not easily done for $75.

That being said, the shops most likely to have the equipment and experience to do the job correctly will be the ones that specialize in heavy mods as many prefer to do a weighing rather than just a calculation after such work. Your small one man shop normally will not be your best bet for this sort of work. If you haven't done it yet, you might want to call JA at ARR. TEAM at DPA might also be worth a try. Who have you tried so far?
 
In Anchorage we have a service that travels with digital scales. I weigh my plane every time I do any significant mods. I drain usable fuel and remove loose gear. The weighing is done indoors in still air while in level flight position and the scale connects to a computer that computes a complete W&B. The mechanic doing the weighing then does a detailed equipment list and prints it along with the airplane TCDS and binds it with a nice cover. He also makes a reduced size W&B that's laminated for carrying in the plane. He can add seasonal items like Fluidyne wheel skis and I get a version with that equipment, too. I think I paid $300 or so last time I did it a couple of years ago.
 
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ahkahn said:
Two questions. First of all, how often would you reweigh/rework your airplane?
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As long as you have an unbroken record of W&B changes, there's no requirement to ever reweigh a privately owned/operated light plane. Many owners choose not to do so because they know that light planes tend to gain about a pound a year of undocumented weight, and those with a mid-70's plane not weighed since it left the factory aren't real happy about the idea of potentially losing 40 lb of legal useful load. OTOH, if you really want to know what your plane weighs so you are sure you're not exceeding book limits, and it hasn't been weighed in a lot of years, the only thing to do is to have it weighed.

I cannot find the last weight and balance on my plane... it's just been a lot of +3/-3 entries in the POH.
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That's typical.

I've been quoted by one high-volume maintenance shop something like $800 to do a workup, and the next quote I got was for like $75, but it was a guy with a set of scales who does it on the side and can only do it like the 4th Thursday of every other month and only when the sun is out for longer than 15 hours.
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Is your convenience worth $725? That's about two days' pay for me, so giving up a day to save $725 would be a no-brainer for me.
 
Minor quibble. You don't drain all the "usable" fuel, and you don't leave the "unusable" fuel.

You drain all the "drainable" fuel, leaving only "undrainable."
 
Not according to TCDS 5A6!

Fuel capacity 60 gal. total, 55 gal. usable (two 30 gal. tanks in wings at +48)
See Note 1 for weight of unusable fuel.

Oil capacity 12 qt. (-15) includes 6 qt. usable
See Note 1 for data on undrainable oil.
Click to expand...
 
kgruber said:
Minor quibble. You don't drain all the "usable" fuel, and you don't leave the "unusable" fuel.

You drain all the "drainable" fuel, leaving only "undrainable."
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It's whatever the manufacturer calls it and they aren't all the same nor do they all specify drainable/undrainable, trapped, residual, dry, usable, unusable etc.
 
135 operators are required to weigh every three years. Many their GMMs are so generic and wonky on weight and balance it's a waste of FAA approved paperwork.
 
ahkahn said:
Hi there-

Two questions. First of all, how often would you reweigh/rework your airplane? I cannot find the last weight and balance on my plane... it's just been a lot of +3/-3 entries in the POH.

Secondly, does anyone know of a reasonably priced weight/balance place around the Chicagoland area? I also frequently fly to Owensboro, KY, Detroit area, and Cincinnati area.

I've been quoted by one high-volume maintenance shop something like $800 to do a workup, and the next quote I got was for like $75, but it was a guy with a set of scales who does it on the side and can only do it like the 4th Thursday of every other month and only when the sun is out for longer than 15 hours.

Thanks in advance!
Click to expand...

I weigh them when I buy them or do major work. With the 310 since I was doing the panel right away, I had them weigh it when done since we changed out the charging system to modern alternators and removed 3 generations of boxes and dead harnesses.

I like to know for sure what my real weight is.
 
I suppose that I should have added a disclaimer to my post that those were typical steps to be taken and that my terminology was generic and not referring to any particular make or model of aircraft operating under any specific FAR or by any specific operator.

It has been 30 years since I have weighed a GA aircraft though in the intervening years, I have weighed numerous airliners including 727s, 757s and L-1011s.

I was just providing some general info to the OP.

I defer now to POA's resident experts and know-it-alls and parsers of all things written.
 
SkyDog58 said:
I suppose that I should have added a disclaimer to my post that those were typical steps to be taken and that my terminology was generic and not referring to any particular make or model of aircraft operating under any specific FAR or by any specific operator.

It has been 30 years since I have weighed a GA aircraft though in the intervening years, I have weighed numerous airliners including 727s, 757s and L-1011s.

I was just providing some general info to the OP.

I defer now to POA's resident experts and know-it-alls and parsers of all things written.
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Are airliners as confusing to get configured correctly as biz jets?
(The problem being in my experience, the OEM sell a tube and a different company installs a custom interior then what is included on the empty weight is rarely clear )
 
Henning said:
I like to know for sure what my real weight is.
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:yeahthat: Having just bought the plane recently and just had some avionics work done, I'd like to know for sure what the real weight is.

JA quoted me $700. Seemed a rather high, but not sure what everything entails.

Thanks for all the info!

What is the average price/going rate?
 
kgruber said:
It is impossible to limit draining the fuel to the unusable level. Explain how you might do that.

The unusable fuel is mathematically added back in.
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Drain fuel through the strainer in a level flight position. When the fuel stops flowing, all the usable fuel is gone. I've participated in several weighings of my own planes and that's how I've done it. That may not be technically perfect but it's darn close.
 
SkyDog58 said:
I suppose that I should have added a disclaimer to my post that those were typical steps to be taken and that my terminology was generic and not referring to any particular make or model of aircraft operating under any specific FAR or by any specific operator.

It has been 30 years since I have weighed a GA aircraft though in the intervening years, I have weighed numerous airliners including 727s, 757s and L-1011s.

I was just providing some general info to the OP.

I defer now to POA's resident experts and know-it-alls and parsers of all things written.
Click to expand...

Just for my own curiosity, how do you manage to get a big boy L-1011 to climb up on scales? Are they embedded? Ramps?
 
Stewartb said:
Drain fuel through the strainer in a level flight position. When the fuel stops flowing, all the usable fuel is gone.
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Nope. Do that and all the drainable fuel is gone. A completely different amount.

That is why they have different names.
 
Ahh, yes. Mr. W&B did add 30# "unusable" fuel back to the empty weight per the TCDS. You are correct.
 
ahkahn said:
:yeahthat: Having just bought the plane recently and just had some avionics work done, I'd like to know for sure what the real weight is.

JA quoted me $700. Seemed a rather high, but not sure what everything entails.

Thanks for all the info!

What is the average price/going rate?
Click to expand...

They through it in with the panel work on the 310, and the other 3 I did at the shops I was working at, but IIRC Ward was charging $300 or so including the de fueling and all the rest of the stuff.
 
Stewartb said:
Ahh, yes. Mr. W&B did add 30# "unusable" fuel back to the empty weight per the TCDS. You are correct.
Click to expand...


And, if you are very careful to fly coordinated.......you'll probably be able to burn the "unusable" fuel.

Skywagons Are great!
 
C'mon, tell me you don't rock those wings when the fuel gets low. Maybe more of a waggle. B) I do love my Skywagon.
 
My old Skywagon is in Anchorage. But the guy doesn't take much care of her. It's on floats. N185KG
 
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