Take-off The distance to accelerate to Rotation Speed, rotate, accelerate to lift-off, then climb and accelerate in order to achieve 50 ft speed at 50 feet above the runway.
Take-off Flight Path The minimum gradient of climb required to clear obstacles in excess of 35 feet, measured horizontally from reference zero and vertically at the altitude above the runway. Reference zero is the point where the airplane has reached 35 feet above the runway as determined from the Accelerate-Go graphs.

WEIGHT AND BALANCE TERMINOLOGY 載重平衡術(shù)語
 

Approved Loading Envelope   Those combinations of airplane weight and center of gravity which define the limits beyond which loading is not approved.
Arm The distance from the center of gravity of an object to a line about which moments are to be computed.
Basic Empty Weight The weight of an empty airplane including full engine oil and unusable fuel. This equals empty weight plus the weight of unusable fuel, and the weight of all the engine oil required to fill the lines and tanks. Basic empty weight is the basic configuration from which loading data is determined.
Center Of Gravity A point at which the weight of an object may be considered concentrated for weight and balance purposes.
CG Limits The extreme center of gravity locations within which the airplane must be operated at a given weight.
Datum A vertical plane perpendicular to the airplane longitudinal axis from which fore and aft (usually aft) measurements are made for weight and balance purposes.