Calculating Aircraft Weight and Balance
by Mike_maurer
137K
24
10
Intro: Calculating Aircraft Weight and Balance
This instructable explains the process of finding the center of gravity
for the weight and balance of an aircraft. This is an important process
when piloting an aircraft because the location affects performance
characteristics of the aircraft and if it is out of acceptable limits the
aircraft may be uncontrollable. Having this information calculated and on
hand is, in fact, a requirement for every flight you make.
What you will need:
Aircraft information manual
Paper
Pencil
Calculator
STEP 1: Find Your Aircraft's Empty Weight and Moment.
Each aircraft's weight and moment are different. This information will be
found in the Pilot's Operating Handbook (POH) specific to the aircraft
you are flying. It will be in the weight and balance chapter which is
standard chapter six.
STEP 2: Find Weights of Everything Loaded.
This includes pilot, all passengers, baggage, and the fuel that will be
loaded into the aircraft. You will find the fuel load in the first
chapter of the POH. Keep in mind that you will use the amount labeled
"usable fuel" because unusable fuel is included in the aircraft's weight
and that fuel weighs six pounds per gallon.
STEP 3: Calculate the Moment for the Load.
In chapter 6 of the POH you will find either a chart similar to the one
on the left or a figure like the one shown on the right. If you have the
chart you can follow the weight to the appropriate line to find the
moment. If you have the figure, you need to multiply the weight of each
position by the number given as the arm to find the moment. Calculate the
moments for the pilot, all passengers, fuel, and baggage.
Example:
Using the graph above, if the pilot and front passenger weighed 300
pounds, you would find 300 on the vertical axis. You then follow that
over to where it intersects the line labelled "Pilot and front
passenger". You then follow that down to the horizontal axis to get your
moment value of about 11. Using the other method with the same 300 pounds
you would multiply by the value given for the pilot and front passenger
which gives you 300*37=11,100
STEP 4: Total Up the Weights and the Moments
Add together the weights for the aircraft, people, fuel, and baggage.
Also add the moments found in the previous step (pilot, passengers, fuel,
and baggage) to the moment of the empty aircraft.
STEP 5: Determine If Center of Gravity Is Within Limits
In chapter 6 of the POH find the chart that shows the acceptable limits
of the center of gravity. It will look like one of the charts pictured
above. One compares the total weight to the total moment and one compares
the total weight to the arm of the center of gravity. If your chart uses
the arm all you need to do is divide the total moment by the total weight
to find that value. If the intersection falls within the area outlined on
the chart you are within acceptable limits to fly.
Example:
If your total weight was 2500 and total moment was 105 (105,000) you
would find these values on their specific axes on the second chart
pictured and their intersection lies within the outlined area. Using the
arm you would find 105,000/2500=42 which when found on the first chart
also falls withing the border.
6 Comments
RohaidianaR 6 years ago
can you please explain the moment formula ?
SkyWalter 3 years ago
a moment is just given by the multiplication of the weight by its arm
Weight * Arm = Moment
AeroUNO 6 years ago
What does the 37 mean in the equation? Thanks!
SkyWalter 3 years ago
It refers to the Pilot CG arm position, starting from the zero point
(Datum, firewall, as you can see in the figure). The station is between
34 and 46 and it means to be located exactly in 37
tomatoskins 10 years ago
I think this is very informative! I like learning intersting things like
this. Keep it up!
carlos66ba 10 years ago
Interesting information. There should be an app for this :)
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