Weight & Balance:
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You can learn more about this topic in chaper 10 of the FAA's
Pilot Handbook
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Weight and Balance
for our planes:
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Why is it
important?
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Weight and balance
is one of the most important factors affecting
safety of flight. An overweight aircraft, or
one, whose center of gravity is outside the
allowable limits, is inefficient and dangerous
to fly. The responsibility for proper weight
and balance control is the responsibility of
the pilot in command at the end of the day.
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Terms and
Definitions
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- Basic Empty
Weight (or Empty Weight)
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Airframe, engines,
and fixed equipment. Includes optional &
special equipment, fixed ballast, hydraulic
fluid, unusable (residual) fuel, and full engine
oil (some older aircraft only include un-drainable
residual oil)
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- Usable Fuel
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fuel available
for flight planning (1gal = 6 lbs)
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- Unusable fuel
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remaining fuel
after a runout test is completed - fill lines
or trapped in the sumps
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- Fuel load
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Expendable part
of the load of the airplane. It includes only
usable fuel, not fuel required to fill the lines
or that which remains trapped in the tank sumps.
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- Useful load
(payload)
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The weight of
the pilot, copilot, passengers, baggage, usable
fuel, and drainable oil. It is the empty weight
subtracted from the maximum allowable gross
weight. This term applies to general aviation
aircraft only.
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- Max Ramp Weight
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Max weight approved
for ground maneuvers
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- Max Takeoff
Weight
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Max weight approved
for start of takeoff roll
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- Max Landing
Weight
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Max weight approved
for landing touchdown
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- Center of gravity
(CG)
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The point about
which an aircraft would balance if it were suspended
- the mass center of the aircraft or the theoretical
point at which the entire weight of the aircraft
is assumed to be concentrated Þ (The plane
rotates around the CG during flight)
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- Center of gravity
limits (range / envelope)
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Forward and
aft points within which the CG must be located
during flight. These limits are indicated on
pertinent airplane specifications.
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- Center of gravity
range
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Distance between
the forward and aft CG limits indicated on pertinent
airplane specifications.
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- Center of Pressure
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Point on the
airfoil where lift is concentrated.
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- Datum (reference
datum)
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Imaginary vertical
plane or line from which all measurements of
arm are taken. The datum is established by the
manufacturer. Once the datum has been selected,
all moment arms and the location of CG range
are measured from this point.
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- Station
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Location in
the airplane which is identified by a number
designating its distance in inches from the
datum. The datum is, therefore, identified as
station zero. An item located at station +50
would have an arm of 50 inches.
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- Arm
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Horizontal distance
in inches from the reference datum line to the
center of gravity of an item. The algebraic
sign is plus (+) if measured aft of the datum,
and minus (-) if measured forward of the datum.
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- Moment
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Product of the
weight of an item multiplied by its arm. Moments
are expressed in pound-inches (lb-in). Total
moment is the weight of the airplane multiplied
by the distance between the datum and the CG.
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Study Questions:
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What is the Max
Gross Weight for your aircraft?
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Where do you
find W&B data for your aircraft?
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How do you find
the CG? (Describe the process, terms, and equation)
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Performance Characteristics
of being overloaded
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Performance Characteristics
of a forward CG
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Performance Characteristics
of an aft CG
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Standard weights
- gallon of gas, one person
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Know how to calculate
the CG and plot it based on information in chapter
6 of your POH
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