Free increase in useful load

TangoWhiskey

TangoWhiskey

Touchdown! Greaser!
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Feb 23, 2005
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Midlothian, TX
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3Green
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KJWY - Mid-Way Regional
So, one of our members posted this link to the MSDS sheet for 100LL in another thread:

http://www.phillips66aviation.com/pdfs/AvGas MSDS.pdf

On page 5, notice the weight of 100LL is 5.83#, if you want to be exact about it. We generally use a 6#/gallon weight.

So, on the T182T I fly, with 92 gallons in full tanks, that works out to 536.36# vs 552#. A free 15.64# increase in useful load!
 
Great! Go ahead and have that bacon double cheeseburger then.
 
For math simplicity, I'll still use 6#/gallon, but just remember that in the T182T, if my calculations show me "at gross", I can safely go another 15# over and still be under gross. On the trip to OSH last year, with two guys and a week full of camping gear, 15# more would have been nice!
 
TangoWhiskey said:
So, one of our members posted this link to the MSDS sheet for 100LL in another thread:

http://www.phillips66aviation.com/pdfs/AvGas MSDS.pdf

On page 5, notice the weight of 100LL is 5.83#, if you want to be exact about it. We generally use a 6#/gallon weight.

So, on the T182T I fly, with 92 gallons in full tanks, that works out to 536.36# vs 552#. A free 15.64# increase in useful load!
Click to expand...


Thanks Troy! I am about to go change the factor in my W&B spreadsheet from 6 to 5.83. With Miss Piggy, every ounce must be considered.
 
Let's see, 0.17 pounds per gallon times 16 gallons is, um, 2.7 pounds!!!!! That's like, a whole jar of Peanut Butter!
 
TangoWhiskey said:
On page 5, notice the weight of 100LL is 5.83#, if you want to be exact about it. We generally use a 6#/gallon weight
Click to expand...

TangoWhiskey said:
For math simplicity, I'll still use 6#/gallon, but just remember that in the T182T, if my calculations show me "at gross", I can safely go another 15# over and still be under gross. On the trip to OSH last year, with two guys and a week full of camping gear, 15# more would have been nice!
Click to expand...

MBDiagMan said:
Thanks Troy! I am about to go change the factor in my W&B spreadsheet from 6 to 5.83. With Miss Piggy, every ounce must be considered.
Click to expand...
Careful now, lets figure this out before you all start changing your weight and balance :)

Keep in mind that the weight of a gallon of 100LL will vary with temperature. As 100LL warms it expands, as it expands the weight of a gallon will be less.

As I look around at various MSDS you'll see different weights that really don't add up with each other. Which is interesting.

If you take a look at Wikipedia you'll see the number most of us are used to:
Avgas has a density of 6.02 lb/U.S. gal at 15 °C, or 0.721 kg/l, and this density is commonly used for weight and balance computation. Density increases to 6.40 lb/US gallon at -40 °C, and decreases by about 0.5% per 5 °C (9 °F) increase in temperature.[1]
Click to expand...

So I slapped together this chart based on that wikipedia temperature and the phillips tsds. I have no idea if it is accurate:
100ll.png
 
I guess that's why we just use the 6#/gal figure and call it good enough. :)
 
TangoWhiskey said:
I guess that's why we just use the 6#/gal figure and call it good enough. :)
Click to expand...

If you ever get ramp checked for weight, just tell the FAA you filled up in a hangar heated to 200 degrees.

BTW- Crazy how adding a turbo to a Cessna reduces the useful load. Add a TN system to a Bonanza and you get an extra 200 lbs. gross.

Hummm.
 
jesse said:
Careful now, lets figure this out before you all start changing your weight and balance :)

Keep in mind that the weight of a gallon of 100LL will vary with temperature. As 100LL warms it expands, as it expands the weight of a gallon will be less.

As I look around at various MSDS you'll see different weights that really don't add up with each other. Which is interesting.

If you take a look at Wikipedia you'll see the number most of us are used to:

<SNIP>
Click to expand...
So if I measure the fuel density, I can adjust my W&B? :)

As for the variances in weight, there's probably a range of compounds they can put in aviation gasoline which causes variances in density.

The link cited in the first post of this thread claims up to 10% toluene.

This link claims up to 30% toluene (that v/v business usually denotes a percentage).
http://selair.selkirk.ca/Training/Program_Manual/documents/program-manual-appendix07.pdf

while this MSDS claims 10 to 15% toluene
http://www.online.petro-canada.ca/datasheets/en_CA/w118.pdf
and also gives a range of densities.

I'm guessing the toluene is in the gas to improve the octane rating because I remember (perhaps incorrectly) from my organic chem classes that aromatic compounds (benzene, toluene, xylene, etc) tend to raise the octane rating.
 
Cap'n Jack said:
So if I measure the fuel density, I can adjust my W&B? :)

As for the variances in weight, there's probably a range of compounds they can put in aviation gasoline which causes variances in density.

The link cited in the first post of this thread claims up to 10% toluene.

This link claims up to 30% toluene (that v/v business usually denotes a percentage).
http://selair.selkirk.ca/Training/Program_Manual/documents/program-manual-appendix07.pdf

while this MSDS claims 10 to 15% toluene
http://www.online.petro-canada.ca/datasheets/en_CA/w118.pdf
and also gives a range of densities.

I'm guessing the toluene is in the gas to improve the octane rating because I remember (perhaps incorrectly) from my organic chem classes that aromatic compounds (benzene, toluene, xylene, etc) tend to raise the octane rating.
Click to expand...

You remember correctly.
 
jesse said:
Careful now, lets figure this out before you all start changing your weight and balance :)

Keep in mind that the weight of a gallon of 100LL will vary with temperature. As 100LL warms it expands, as it expands the weight of a gallon will be less.

As I look around at various MSDS you'll see different weights that really don't add up with each other. Which is interesting.

If you take a look at Wikipedia you'll see the number most of us are used to:


So I slapped together this chart based on that wikipedia temperature and the phillips tsds. I have no idea if it is accurate:
100ll.png
Click to expand...
In general, Phillips knows what they are doing. They had a *very* good research lab at one point. Dunno where they are today though...
 
Looks like you tundra-bunnies lost a few lbs of useful load. :)

For me, there is enough sadness in life without W/B pedantry. If you need to take more junk, you just need a longer runway :D

...unless you're with the FAA. In which case, I calculate my W/B to 6 decimal places and sample ambient temperature at 3 points on the field.
 
schmookeeg said:
Looks like you tundra-bunnies lost a few lbs of useful load. :)

For me, there is enough sadness in life without W/B pedantry. If you need to take more junk, you just need a longer runway :D

...unless you're with the FAA. In which case, I calculate my W/B to 6 decimal places and sample ambient temperature at 3 points on the field.
Click to expand...

Haha, sounds like a chapter taken out of my fueling practices ;)
 
TangoWhiskey said:
On page 5, notice the weight of 100LL is 5.83#, if you want to be exact about it. We generally use a 6#/gallon weight.
Click to expand...

Meh. Probably .17 worth of dirt in the fuel. Back up to 6
 
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