Jabiru J230-D 2020 Pilot Operating Handbook page 12

Weight and Balance Terminology
•
Datum – An imaginary vertical plane from which all horizontal distances are measured for
balance purposes.
•
Station – A location along the aircraft fuselage usually given in terms of distance from the
reference datum.
•
Arm – The horizontal distance from the reference datum to the centre of gravity (C of G) of
an item.
•
Moment – The product of the weight of an item multiplied by its arm.
•
Index Unit – Moment divided by a constant. Used to simplify balance calculations by
reducing the number of digits.
•
Centre of Gravity (C of G) – The point at which an aircraft would balance if suspended. The
distance from the C of G to the reference datum can be found by dividing the total moment
by the total weight of the aircraft.
•
C of G Arm – The arm obtained by adding the aircraft's individual moments and dividing the
sum by the total weight.
•
C of G Limits – The extreme centre of gravity locations within which the aircraft must be
operated at a given weight.
•
Useable Fuel – The quantity of fuel available for flight planning purposes.
•
Unusable Fuel – The quantity of fuel (determined under adverse fuel flow conditions) that
is not available for flight.
•
Empty Weight – Weight of aircraft with unusable fuel and full oil.
•
Useful Load – Difference between take-off weight, and basic empty weight.
•
Maximum Take-Off Weight – Maximum weight approved for take-off.
•
Maximum Landing Weight – Maximum weight approved for the landing.
•
Header Tank – Fuel tank plumbed between the wing tanks and the engine. Also known as
Collector Tank or Sump Tank.
JP-FM-09 Revision:
Jabiru Aircraft
Model J230-D
6
Pilot Operating Handbook
28/2/2020 Page 12