Can you solve this W/B?

TK211X

TK211X

Pre-takeoff checklist
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Can anyone solve this problem? TIME SENSITIVE.

I need help, my mind sort of froze up on this. :confused:

Here is an airplane and all of the information available to you.....

Empty Weight: 1443.42 ARM: ?
Oil 8 quarts: 15 ARM: -20
Pilot & Pax: --- ARM: 36
Fuel: --- ARM: 48
Rear Pax: --- ARM: 70
Bag Comp.: --- ARM: 95

Here is the newest weight stat sheet with fairings included.......

Nose Fairing: "402" ARM: -7 MOM: -2814
LG Fairing: "529" ARM: 56.7 MOM: 29994.3
RG Raring: "527" ARM: 56.7 MOM: 29880.9

New empty weight is: 1458
New empty CG is: 39.13
New Moment: 57061.2

The new useful load is 842LBS. at 2300LBS. gross weight.

Question:
What is the empty weight and empty Arm C.G. for this airplane WITHOUT the wheel fairings?
 
Last edited:
What am I missing? Looks simple.

Divide moment of each fairing by arm of each fairing to get weight of each fairing. Subtracts weights from empy weight given to get new empty weight.

Subtract the three fairing moments from aircraft moment to get new moment.
Divide new moment by new weight to get new c.g.
 
looks to me like we just don't understand the fairing information.
they way it is written it looks like the nose fair way 402.

402 what, obviously not pounds
could it be 4.02 pounds?


Brian
 
brcase said:
looks to me like we just don't understand the fairing information.
they way it is written it looks like the nose fair way 402.

402 what, obviously not pounds
could it be 4.02 pounds?


Brian
Click to expand...

Right, I did that and calculated the new empty weight simply as 1443.42 but where is the new CG?
 
Re: Can anyone solve this problem? TIME SENSITIVE.

TK211X said:
Nose Fairing: "402" ARM: -7 MOM: -2814
LG Fairing: "529" ARM: 56.7 MOM: 29994.3
RG Raring: "527" ARM: 56.7 MOM: 29880.9

QUOTE]

To begin with... I'm thinking these should be
more like:

Nose Fairing: "4.02" ARM: -7 MOM: -28.14
LG Fairing: "5.29" ARM: 56.7 MOM: 299.94
RG Fairing: "5.27" ARM: 56.7 MOM: 298.81

Unless you have some really heavy fairings or very short airplane...
Click to expand...
 
The difference in empty weights is 15 pounds. If we assume decimal places two points too far to the right for the weight and moment of the fairings, that works out.
So, assuming that,
If we take -28.14 +299.14+298.81 = 569.81 for the total fairing moment.

Given the new moment of 57061.2 - 569.81 we get a fairing removed moment of 56491.
Now, taking the moment of 56491. divided by the (assumed) empty weight of (1458 - 14.58) (a little odd that the numbers match up like that) we get an empty CG arm of 39.1372 without the fairings.
 
brcase said:
looks to me like we just don't understand the fairing information.
they way it is written it looks like the nose fair way 402.

402 what, obviously not pounds
could it be 4.02 pounds?


Brian
Click to expand...

yeah, if they weighed that much, I'd pull them off too. :D
 
SkyDog58 said:
Hard to do calculations with bad data. Garbage in = garbage out.
Click to expand...

In this case though it's irrelevant because the change in balance falls within the margin of error of graphing the result into the envelope. Basically you just adjust the useful load 15 lbs for the pants on or off.
 
But the pants are only part of the installation. The brackets and bolts that hold them on could easily be 1/2 of the installation.


Do you remove them as well?
 
The answer is........








.....pancakes, fresh pankakes with tutti frutti syrup.
 
Re: Can anyone solve this problem? TIME SENSITIVE.

TK211X said:
I need help, my mind sort of froze up on this. :confused:

Here is an airplane and all of the information available to you.....

Empty Weight: 1443.42 ARM: ?
Oil 8 quarts: 15 ARM: -20
Pilot & Pax: --- ARM: 36
Fuel: --- ARM: 48
Rear Pax: --- ARM: 70
Bag Comp.: --- ARM: 95

Here is the newest weight stat sheet with fairings included.......

Nose Fairing: "402" ARM: -7 MOM: -2814
LG Fairing: "529" ARM: 56.7 MOM: 29994.3
RG Raring: "527" ARM: 56.7 MOM: 29880.9

New empty weight is: 1458
New empty CG is: 39.13
New Moment: 57061.2

The new useful load is 842LBS. at 2300LBS. gross weight.

Question:
What is the empty weight and empty Arm C.G. for this airplane WITHOUT the wheel fairings?
Click to expand...

The Nose, LG, and RG Fairing weights are weights of the airplane with a scale under the nose 402 pounds, left main 529 pounds, and right main 527 pounds. They add up to 1458 pounds. The arms are the station locations measured for the three scales. The moments are wt times arm. Add them together and you get 57061.2. The CG is 57061.2/1458.

There is no weight given for the weights of the fairings unless you are implying that the 1443.42 is the weight with the fairings removed. If so, the combined weight of the fairings is 14.58 pounds. Divide that by three to get an average fairing weight of 4.86 pounds or 5 pounds to the nearest pound. Then you would adjust the three weights and moments by subtracting 5 pounds from each, then recalculate the moments and add the moments and the new weights.

Nose Fairing: "402 -5 = 397" ARM: -7 MOM: -2779
LG Fairing: "529 -5 = 524" ARM: 56.7 MOM: 29710.8
RG Raring: "527 -5 = 522" ARM: 56.7 MOM: 29597.4

New empty weight is: 397+524+522 = 1443
New empty CG is: 56509.2/1443 = 39.16
New Moment: -2799 +29710.8 + 29597.4 = 56509.2
 
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