Reading W&B Report

Jaybird180

Jaybird180

Final Approach
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Jaybird180
I intend to create a spreadsheet to calculate W&B for me. Obtaining a copy of the latest W&B report revealed some interesting factoids.

#1- The W&B has been calculated not weighed
#2- The useful load is based on Ramp Weight not Gross weight:dunno:. I obtained this by adding the useful and empty weights as reported together and obtained 2558.
#3- The Empty and Useful weights are given in Hundreths of a pound (ie xxx.xx)

Ramp weight of the C-172S is 2558 vs gross of 2550.

Is #2 correct? Is #3 normal?
 
Jay, sometimes you have a higher max ramp weight than the max takeoff weight. It means you can put that sort of load in the plane on the ground, but you cannot go rolling at high speeds with that load.

In this case, you've got to burn a gallon and a half of gas between start and takeoff.
 
Jaybird180 said:
#3- The Empty and Useful weights are given in Hundreths of a pound (ie xxx.xx)

Is #2 correct? Is #3 normal?
Click to expand...

#3 is just plain funny. Do you think anything in your plane has been weighed accurately to the hundredth of a pound? Have you been weighed accurately to the hundredth of a pound.

That W&B is carrying around more significant digits than it should. I would guess it is not accurate to 5 lbs. I don't think my plane has ever been weighed since 1966 (if it was even weighed then). I'd guess that my W&B is off by at least 25lbs.
 
COFlyBoy said:
#3 is just plain funny. Do you think anything in your plane has been weighed accurately to the hundredth of a pound? Have you been weighed accurately to the hundredth of a pound.

That W&B is carrying around more significant digits than it should. I would guess it is not accurate to 5 lbs. I don't think my plane has ever been weighed since 1966 (if it was even weighed then). I'd guess that my W&B is off by at least 25lbs.
Click to expand...

See #1 :rofl:
 
TMetzinger said:
Jay, sometimes you have a higher max ramp weight than the max takeoff weight. It means you can put that sort of load in the plane on the ground, but you cannot go rolling at high speeds with that load.

In this case, you've got to burn a gallon and a half of gas between start and takeoff.
Click to expand...

What I meant is:
Isn't the W&B supposed to be based on GROSS and not RAMP weight like this one? I know about the 8 pounds
http://www.youtube.com/watch?v=HR6n_EQqcCg
 
#1,#3 Airplanes are weighed at the completion of the manufacuring/outfitting process. Most of the weight and balance changes once in-service result from equipment and configuration changes and the weight and balance is updated based on known weights and arms. It is quite possible that the airplane has only physically been wighed once, and there is nothing really wrong with that. If you have reason to believe the actual weight differs from the revisions, the airplane can always be weighed again. Most reputable shops weigh the aircraft using digital scales that read very accurately. We always weigh three times, rotating the three scales each time. Then we average the three readings for each point to get an incredibly accurate actual weight.
#2 The 172S has the following published maximum weights:
Ramp Weight:
Normal Category . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2558 POUNDS
Utility Category . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2208 POUNDS
Takeoff Weight:
Normal Category . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2550 POUNDS
Utility Category . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2200 POUNDS
Landing Weight:
Normal Category . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2550 POUNDS​

Utility Category . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2200 POUNDS

So yes, the maximum gross weight is 2558 lbs and this is the number to use for the W&B, knowing that during the taxi you'll burn off fuel to the max takeoff weight. I don't believe the term "gross" is in the Cessna 172S manual, so that could be a source of confusion.

Scott
 
FlyWithScott said:
#1,#3 Airplanes are weighed at the completion of the manufacuring/outfitting process.
Click to expand...
No requirement for that. Most (if not all) light plane weights are based on average weights from the first dozen or two produced plus occasional spot-check sampling thereafter, with computations to account for equipment above standard. So...

It is quite possible that the airplane has only physically been wighed once, and there is nothing really wrong with that.
Click to expand...
...it is entirely possible and even likely that unless it was at some point used in Part 135 ops (where periodic weighing is required), your plane has never been weighed.
 
Ron Levy said:
No requirement for that. Most (if not all) light plane weights are based on average weights from the first dozen or two produced plus occasional spot-check sampling thereafter, with computations to account for equipment above standard. So...

...it is entirely possible and even likely that unless it was at some point used in Part 135 ops (where periodic weighing is required), your plane has never been weighed.
Click to expand...

In my best Johnny Carson voice " I did not know that"...

I thought all planes were weighed when they were finished and headed out the door for the end user...

Ben.
 
Ron Levy said:
No requirement for that. Most (if not all) light plane weights are based on average weights from the first dozen or two produced plus occasional spot-check sampling thereafter, with computations to account for equipment above standard. So...

...it is entirely possible and even likely that unless it was at some point used in Part 135 ops (where periodic weighing is required), your plane has never been weighed.
Click to expand...

A 172 used for 135 never has to be weighed either, that requirent is only for multi-engine aircraft.
 
My shop had my plane (Cherokee 140) weighed and a new W&B done at that last annual, because he didn't like how some of logging had been done (it was the first annual, since I had bought the plane). It gained 60 lbs. :(
 
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