Targetware: Flight Model Development

Targetware ACM File Guide

PART REFERENCE: Body

As with all parts, the name, type, location and size entries must be included, as well as the following entries:

front_equiv_drag = area in square meters (frontal area * 0.3 is a good starting point)
side_equiv_drag = area in square meters
equiv_lift_area = area in square meters

With a combination of front, side and lift areas, the lift and drag of the body can be determined for any range of pitch and yaw angles.  The side and lift areas can be measured directly from the side and top views of a 3-view drawing respectively.  It is recommended that any body surface be split into at least 2 parts, one ahead and one behind the CG of the plane.  The equivalent frontal area should be adjusted to achieve proper flight speeds.  If more than one part is used to define the body, remember to divide the frontal area into each part.

critical_mach = a value between 0 and 1

This is the freestream velocity at which the local airflow over certain parts of the aircraft (airfoil, body) reaches supersonic speed.  A rise in drag will result.  Since the airspeeds corresponding to a particular mach will vary with altitude, you can use this setting to make sure that speeds are correct at all altitudes.  For example, if you've fine tuned the drag areas so that speed is correct at sea level, and you know the power vs altitude characteristics of your engine are accurate, yet your plane is too fast at high altitudes, your critical mach setting may be too high.