tions 4 through 7 of the USAF Stability and Control Datcom (revised April. ). The report consists of the following three volumes: o Volume I, Users Manual. This report is a collection, correlation, codification, and recording of best knowledge, opinion, and judgment in the area of aerodynamic stability and control. contract FC, which automated Sections 4 and 5 of the USAF Sta- bility and Control Datcom; AFFDL TR produced under contract.
Digital DATCOM requires an input file containing a geometric description of an aircraft, and outputs its corresponding dimensionless stability derivatives according to the specified flight conditions. The values obtained can be used to calculate meaningful aspects of flight dynamics. The report consists of. A maximum of Mach-altitude combinations can be run at once, with up to 20 angles of attack for each combination. The user can specify whether the Mach number and altitude varies together, the Mach number varies at a constant altitude, or the altitude varies at a constant Mach number.
The theoretical wing area, mean aerodynamic chordand wing span are input along with a parameter defining the surface roughness of the aircraft. The X- and Z- coordinates are needed for the winghorizontal tailand uasf tail in order for the aircraft to be synthesized correctly. DATCOM does not require that the origin for the aircraft has to be the nose of the aircraft; any arbitrary point will do, but all of the dimensions need to be referenced from that point.
Incidence angles can also be added to the wing and horizontal tail.
Up to 20 stations can be specified with the fuselage half-width, upper coordinate and lower coordinate being defined at each station. For supersonic analysis, additional parameters can be input. The basic parameters such as root chord, tip chord, half-span, twistdihedral and sweep are input. The canard must be ksaf as the forward lifting surface i.
Additionally, custom airfoils can be input using the appropriate namelists. Up to 9 flap deflections can be datclm at each Mach-altitude combination. All dimensions are taken in feet and degrees unless specified otherwise. By default, only the data for the aircraft is output, but additional configurations can be output:. For each configuration, stability coefficients and derivatives are output at each angle of attack specified.
The basic output includes:. For complete aircraft configurations, downwash data is also included. However, in its day, the program was an advanced estimation tool, and certainly much faster than plowing through pages and pages of engineering texts.
USAF Stability and Control DATCOM – Wikipedia
The simplification affects the coefficient of drag for the aircraft. Dynamic derivatives are not output for aircraft that have wings that are not straight-tapered or have leading edge extensions. This problem can be overcome by using experimental data for the wing-body using non-straight tapered wing.
There is no method to input twin vertical tails mounted on the fuselage, although there is a method for H-Tails. This problem can be addressed by approximating the twin vertical tails as a single equivalent vertical tail mounted to the fuselage. According to the manual, there is no any input parameters which define the geometriy of rudder. This problem can be addressed by superposition of lifting surfaces through the experimental input option.
There are intentions among those that use this package to improve the overall package, through an easier user interface, as well as more comprehensive output data.
While the original DIGDAT program has been left relatively untouched, there has been a new front-end created that will allow the user to name the input file with something more significant than FOR The new input file format allows the ysaf to place comments in the input file.
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There have also been datcoj placed in the DIGDAT that allow for alternate outputs in addition to the original output format, which is columns wide and slightly user abusive if you intend to import the data into another application. Data tables can easily be output to the screen or to PNG files for inclusion into reports. OpenDatcom incorporates all the basic non-experimental functionality supported by the Digital DATCOM while providing real-time input error and bounds checking.
An alpha version of the program was released November 1, to the general public.
There has been some research in using Digital DATCOM in conjunction with wind tunnel studies to predict aerodynamics of structurally impaired aircraft. Raw results from the code provide good correlation with wind tunnel data at very low angles of attack, but accuracy deteriorates rapidly as the angle of attack increases.
A new methodology is then proposed which combines the experimental results of healthy aircraft with the predicted aerodynamics of the damaged cases, to yield better correlation between experimental and predicted aerodynamic coefficients for damaged aircraft. Three damage-configurations are studied at supersonic speeds. The methodology can be used to quickly generate aerodynamic model for damaged aircraft for simulation and reconfigurable control.
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