While the horizontal reference datum can be anywhere the manufacturer chooses, most small training helicopters have the horizontal reference datum 100 inches forward of the main rotor shaft centerline.
12.
Since reference datums can have different radii and different center points, a specific point on the Earth can have substantially different coordinates depending on the datum used to make the measurement.
13.
The horizontal reference datum is an imaginary vertical plane or point, placed along the longitudinal axis of the aircraft, from which all horizontal distances are measured for weight and balance purposes.
14.
;Moment : The moment is the moment of force, or torque, that results from an object s weight acting through an arc that is centered on the zero point of the reference datum distance.
15.
Aircraft center of gravity calculations are only performed along a single axis from the zero point of the reference datum that represents the longitudinal axis of the aircraft ( to calculate fore-to-aft balance ).
16.
;Reference Datum : The " reference datum " is a reference plane that allows accurate, and uniform, measurements to any point on the aircraft . The location of the reference datum is established by the manufacturer and is defined in the aircraft flight manual.
17.
;Reference Datum : The " reference datum " is a reference plane that allows accurate, and uniform, measurements to any point on the aircraft . The location of the reference datum is established by the manufacturer and is defined in the aircraft flight manual.
18.
;Reference Datum : The " reference datum " is a reference plane that allows accurate, and uniform, measurements to any point on the aircraft . The location of the reference datum is established by the manufacturer and is defined in the aircraft flight manual.
19.
Since each of these two parameters uses a different reference datum, significant confusion can result because even though a projectile is tracking well below the line of departure it can still be gaining actual and significant height with respect to the line of sight as well as the surface of the earth in the case of a horizontal or near horizontal shot taken over flat terrain.
20.
Where u is the mean flow velocity, \ beta = g K \ cos \ zeta, ( K is the earth pressure coefficient, \ zeta is the slope ), s _ g = g \ sin \ zeta, x is the channel downslope position and x _ d is the distance from the point of the mass release along the channel to the point where the flow hits the horizontal reference datum; E _ { pot } ^ p = \ beta h and E _ { pot } ^ g = s _ g ( x _ d-x ) are the pressure potential and gravity potential energies, respectively.
